VIVIAN'S EVERYDAY CHEMISTRY 
 MOORE AND HALLIGAN'S PLANT PRODUCTION 
 TORMEY AND LAWRY'S ANIMAL HUSBANDRY 
 
 EDITED BY 
 KIRK LESTER HATCH, B.S. 
 
 PROFESSOR OF AGRICULTURAL EDUCATION 
 UNIVERSITY OF WISCONSIN, MADISON 
 
EVERYDAY CHEMISTRY 
 
 BY 
 
 ALFRED VIVIAN 
 
 DEAN OF THE COLLEGE OF AGRICULTURE OF 
 THE OHIO STATE UNIVERSITY 
 
 AMERICAN BOOK COMPANY 
 
 NEW YORK CINCINNATI CHICAGO 
 
 BOSTON ATLANTA 
 
COPYRIGHT, 1920, BY 
 AMERICAN BOOK COMPANY 
 
 All rights reserved 
 
 VIYIAN'8 EVERYDAY CHEMISTRY 
 W. P. 3 
 
 EDUCATION LIBR* 
 
 " 
 
UAxV 
 
 GENERAL INTRODUCTION 
 
 THIS series of texts is based on the theory that the success- 
 ful citizen should know the chemical, physical, and biological 
 forces with which he has to contend ; that he should under- 
 stand the laws under which these forces operate; and that 
 he should acquire some skill in directing them. He should 
 ultimately become able to adjust and correlate these forces 
 so as to bring them all under the orderly operation of economic 
 law. In conformity with the above theory this series has 
 been made to cover the following fundamental divisions : 
 
 1. The science and art of chemistry as applied to everyday Ufa, 
 with special emphasis on household economics, soil fertility, and 
 the relation of chemistry to plant and animal production. 
 
 2. The science and art of producing plants. 
 
 3. The production, care, and management of farm animals. 
 
 4. The proper balance and combination of these aspects of 
 household economics and agricultural production, in the business 
 management of the farm. 
 
 KIRK LESTER HATCH. 
 
 M577057 
 
PREFACE 
 
 THE ordinary high-school course in chemistry in the past 
 has consisted of a condensed treatment of the subject of in- 
 organic chemistry, which was intended to prepare for the 
 further study of that subject in college. The principal ob- 
 jection to a high-school course consisting entirely of inor- 
 ganic chemistry lies in the fact that the ninety per cent of the 
 pupils, who do not go to college and who pursue the subject 
 no farther, are left with a very faint conception of the in- 
 timate relation which chemical phenomena bear to daily 
 life. Such pupils are therefore likely to think of chemical 
 changes as occurring only in beakers and in test tubes. 
 
 The reaction against the old type of high-school course 
 in chemistry has resulted in the publication of a new type of 
 textbooks for secondary schools. In these the authors 
 have gone to the other extreme by attempting to present 
 the applications of chemistry to daily life without any ground- 
 work in the fundamental chemistry of the elements, a 
 knowledge of which is necessary to the understanding of 
 chemical compositions and reactions. 
 
 This text follows a middle course, and while the outstand- 
 ing feature is its treatment of the applications of chemistry, 
 inorganic and organic, the presentation is based on a brief 
 study of the elements and their important compounds and 
 reactions. The preparation of such a book is made difficult 
 by the enormous mass of facts and theories from which 
 must be selected those which are vital to the purpose of the 
 text. Two questions have been asked regarding each fa'ct 
 and theory (1) is this fact or theory essential to the 
 understanding of any of the phenomena of daily life, or 
 (2) is it necessary to explain some other fact or theory 
 that is essential to such an understanding? Unless the 
 answer to one of these questions is affirmative the subject 
 
 7 
 
8 PREFACE 
 
 in question is excluded from the text. The only excep- 
 tions to this rule are a few subjects proved by experience 
 to be of especial value in holding the interest of the pupil. 
 Much of the theory included in the older texts is excluded 
 because of the feeling that a first course in chemistry 
 should deal largely with facts and that the theoretical con- 
 siderations should be left to a more advanced course. The 
 chemistry of the elements has been confined to a score of 
 elements that are of common occurrence. The study begins 
 with the element itself if it is commonly known, but with 
 a compound in case the element is not a familiar substance. 
 In other words, the procedure is always from the known to 
 the related unknown. 
 
 The small high school which cannot afford expensive 
 equipment has been constantly in mind during the prepara- 
 tion of this text. The exercises call for no complicated 
 apparatus ; most of the experiments may be performed by 
 means of simple homemade devices, or even in many cases 
 by the use of kitchen utensils. 
 
 No one group of pupils should be required to use all the 
 material in this book, since a wide range of topics has been 
 treated in order to meet the varying needs of boys and girls. 
 After the first thirty-five chapters have been completed the 
 boys and girls may be separated and allowed to study those 
 chapters which are of particular interest to each group. 
 This book is especially suitable for use in the vocational 
 courses in agriculture and home economics which are being 
 introduced in many high schools. 
 
 Photographs for illustrations have been furnished by: 
 Ohio Experiment Station, Frontispiece and Figs. 174, 225, 
 229, 231, 242, 244; Montana Experiment Station, Figs. 
 210, 211; Illinois Experiment Station, Fig. 236 ; L. H. 
 Guldard, Figs. 92, 237; Jeffrey Manufacturing Company, 
 Figs. 227, 228 ; Dr. E. V. McCullum, Fig. 159. 
 
A WORD TO THE TEACHER 
 
 THE success of a course in chemistry depends largely upon 
 the character of the laboratory work. Without the performance 
 of laboratory exercises the study of chemistry degenerates into 
 a mere act of memorizing. On the other hand, nothing is 
 more pernicious than unsupervised laboratory work, since it 
 not only wastes the time of the pupil but creates bad mental 
 habits. The earnest teacher of chemistry will keep in close 
 touch with the pupils throughout the course. 
 
 In small high schools where the class in chemistry does not 
 include more than ten to fifteen pupils, it is a mistake to divide 
 the time allotted to chemistry into recitation and laboratory 
 periods. The teacher should be at liberty to use each period or 
 part of a period for recitation or experimental work as the 
 progress of the subject suggests ; or better still, the experiment 
 and the recitation should be coincident. 
 
 While it is desirable to have all the pupils perform each 
 experiment, such a procedure is not absolutely essential to an 
 understanding of the subject. Where the equipment is meager, 
 very good results may be obtained by having the class gather 
 around the laboratory table and having each student in turn 
 perform an experiment while all members of the class take notes. 
 This method gives the teacher an opportunity to have the 
 class recite under the most favorable circumstances and espe- 
 cially to test the pupils' powers of inductive reasoning. It also 
 tends to develop that kind of comradeship between pupil and 
 teacher which is the successful teacher's greatest asset. 
 
 The teacher in the small high school needs no longer to hesitate 
 to introduce chemistry because of the cost of apparatus. Most 
 of the experiments in this text may be conducted with equip- 
 ment which is at hand. By the exercise of a little ingenuity 
 the remaining apparatus can be prepared from comparatively 
 inexpensive materials. Common glass tumblers may be used 
 in place of beakers when the application of heat is not neces- 
 sary. Granite ware or porcelain-lined kitchen cups may be 
 used in heating all liquids except very concentrated alkalies 
 and acids. The only advantage in the use of glass beakers is 
 that the experiment may be more readily observed. Much of 
 
 9 
 
10 A WORD TO THE TEACHER 
 
 the needed material may be collected locally by teacher and 
 pupils, and many manufacturers are glad to furnish samples of 
 their products gratuitously for use in the classroom. 
 
 It is not possible to eliminate from the course in chemistry 
 the teacher, upon whom the success of the course depends more 
 than upon any textbook or laboratory guide. For this reason 
 the author has purposely omitted detailed descriptions of the 
 laboratory experiments, leaving the specific directions to the 
 teacher, who will have to give these directions in any event, no 
 matter how complete the descriptions in the laboratory guide 
 appear to be. The larger texts on chemistry, to which the teacher 
 should refer, will give much assistance in arranging the details 
 of the experiment. 
 
 The questions found in the exercises at the end of the 
 chapters are merely suggestive, and many, more will occur to 
 the teacher. Their principal value is in enabling the pupils 
 to test their own knowledge of the subject. The teacher 
 should insist that the pupils look up every cross reference that 
 is found in the text. Additional reading should be assigned 
 on many of the topics, and it will be well to have each pupil 
 report to the class upon certain topics which have been assigned 
 as supplemental work. Most high schools own a good encyclo- 
 pedia, and at least one article in the encyclopedia may be found 
 which is germane to the matter discussed in each chapter of 
 this text. The agricultural colleges of the several states, as 
 well as the United States Department of Agriculture, publish 
 bulletins for free distribution, many of which bear upon sub- 
 jects discussed in this book. In many cases these bulletins ap- 
 peal as much to the interest of people living in the city as to 
 those in the country. Such pamphlets should be procured for 
 the school library. 
 
 The high-school curriculum should fit the community in 
 which the school is located, and the chemistry teacher has the 
 opportunity of bringing his subject into close relationship with 
 the daily life of the pupils. Chemical processes which are of 
 unusual interest to the community should be emphasized, both 
 in the classroom and by means of excursions to points where 
 these processes may be observed. Chemistry should be made to 
 assist the pupil in interpreting life. Above all, the teacher of 
 chemistry should remember that the most important thing to be 
 considered is the pupil and not the subject that is being taught. 
 
FIG. 1. 
 
 INTRODUCTORY LABORATORY 
 MANIPULATIONS 
 
 CHEMISTRY is essentially a laboratory study and is readily 
 understood only when the statements of the text are illus- 
 trated by suitable exercises. As certain 
 laboratory appliances and processes will 
 be used repeatedly during the course, the 
 student should first familiarize himself 
 with them. 
 
 The Bunsen burner is used as a source 
 of heat in most laboratories where gas is 
 available. A common form of the burner 
 is shown in Fig. 1. It is attached to the 
 gas cock by a piece of rubber tubing. When the gas is 
 turned on, the current of gas draws air through the holes 
 at the bottom of the tube, and this mixture when lighted 
 burns with an almost colorless flame, which is very hot and 
 deposits no soot. The air supply may be reduced or entirely 
 cut off by turning the ring at the bottom of the burner so 
 that the hole's in the tube are closed. As the air supply is 
 lessened, the flame gradually becomes yel- 
 low and deposits soot. The colorless 
 flame is used in all experiments unless 
 the directions state otherwise. 
 
 The alcohol lamp is ordinarily used in 
 laboratories where a supply of gas is not 
 available. The simple form shown in 
 Fig. 2 is the most common. Such a lamp 
 11 
 
 FIG. 2. 
 
12 INTRODUCTORY LABORATORY MANIPULATIONS 
 
 FIG. 3. 
 
 may be made in the laboratory from an ink bottle or an 
 oil can and a little candle wicking. When a more in- 
 tense heat is required the type of alcohol 
 lamp shown in Fig. 3 or Fig. 4 may be used. 
 In such a lamp the alcohol is converted into 
 a vapor before it is burned. With proper 
 precautions, the blow torch used by plumbers 
 and painters (Fig. 5), in which gasoline vapor 
 is burned, may be used when high 
 temperatures are needed; but gaso- 
 line requires more careful handling than does alcohol. 
 Glass Working. To cut a piece of glass tubing, 
 make a deep scratch at the desired point with a 
 triangular file. Grasp the tubing in both hands 
 with the thumbs back of the scratch (Fig. 
 G) and pull the tubing apart, at the same 
 time exerting a slight forward 
 pressure of the thumbs. If the 
 tubing does not break easily, 
 make a deeper scratch with the 
 file. Never use much pressure in 
 breaking the tubing. 
 
 Smooth the ends of all glass tubing or glass rods by hold- 
 ing them in the flame of the burner until the glass fuses 
 (Fig. 7). If desired, the end of the tubing may be closed 
 entirely by holding it in the burner until 
 the edges fuse together. 
 
 To bend glass tubing, place the wing 
 top (Fig. 8) on the burner and hold the 
 tubing in the upper part of the flame 
 until the loose end begins to drop of its 
 own weight. Then grasp the loose end FIG. 5. 
 
 FIG. 4. 
 
INTRODUCTORY LABORATORY MANIPULATIONS 13 
 
 and bend to the desired angle. Avoid 
 bends like A and B in Fig. 9, which are 
 due to heating too small an area of the 
 tube. 
 
 A glass tube may be drawn out by heat- 
 ing a small area in the point of the flame 
 (Fig. 10) until the glass is quite soft and 
 
 the walls of the 
 tube are thick- 
 ened. The tube 
 
 must be rotated in the flame dur- 
 ing heating. Remove the tube 
 from the flame and draw it gently in a horizontal position 
 until it is reduced to the desired size (Fig. 11). 
 
 FIG. 7. 
 
 FIG. 6. 
 
 FIG. 8. 
 
 FIG. 9. 
 
 FIG. 10. 
 
 FIG. 11. 
 
14 INTRODUCTORY LABORATORY MANIPULATIONS 
 
 FIG. 12. 
 
 Wash Bottle. Make a wash bottle 
 similar to Fig. 12. This will be found 
 useful in many ways in the laboratory. 
 By blowing in the tube (A) a small 
 stream of water is forced out of the jet 
 (B) . A piece of rubber tubing at C per- 
 mits the stream to be guided in any 
 direction. 
 
 Holes in corks are usually made with 
 a cork borer (Fig. 13). A round or rat- 
 tail file may be used, the hole being filed out until it is 
 the right size for the tubing. The tubing is more easily 
 inserted if it is moistened. If the 
 hole in the cork is too small, there 
 is danger of breaking the tubing 
 and seriously cutting the hands. 
 Rubber corks with holes in them 
 are now so easily obtained that they should be used when 
 possible. 
 
 Heating Liquids in Test Tubes. Hold the test tube by 
 means of a test tube holder or a band 
 of paper as in Fig. 14. Heat w r ith the 
 point of the flame near the top of the 
 liquid, but do not allow the flame to 
 strike the glass above the liquid. 
 Agitate slightly during heating. Be 
 careful that the mouth of the test tube 
 does not point toward any one in case 
 the vapor forces the liquid out of the 
 tube. 
 
 When heating liquids in glass beakers 
 FIQ. 14. the same precaution must be observed 
 
 FIQ. 13. 
 
INTRODUCTORY LABORATORY MANIPULATIONS 15 
 
 against allowing the flame to strike the glass above the 
 liquid. Beakers should be protected by placing them on 
 a piece of wire gauze or asbestos board (Fig. 15). In some 
 
 FIG. 15. 
 
 FIG. 16. 
 
 cases it is desirable to use a sand bath, which consists of a 
 small pan containing sand (Fig. 16). This distributes the 
 heat evenly and prevents breakage. 
 
 Evaporation is commonly performed in small porcelain 
 evaporating dishes 
 (Fig. 17). Wire 
 gauze or the sand 
 bath is frequently 
 used with the 
 evaporating dishes. 
 If the substance is 
 injured by high 
 
 temperature, it is 
 
 evaporated over a 
 
 water bath (Fig. 18), in which case the evaporating dish is 
 
 heated by the steam of the boiling water. The double 
 
 FIG. 17. 
 
 FIG. 18. 
 
 EV. CHEM. 2 
 
16 INTRODUCTORY LABORATORY MANIPULATIONS 
 
 boiler is an example of the practical use of a water bath in 
 the home. 
 
 Filtration is used to separate a solid from a liquid sub- 
 stance. It is usually performed by filtering the liquid 
 through a specially prepared 
 paper known as filter paper. 
 This comes in circular pieces in 
 
 FIG. 19. 
 
 FIG. 20. 
 
 various sizes, which are folded as shown in Fig. 19 so as to fit 
 into a glass funnel (Fig. 20) . When poured on the filter paper 
 the liquid runs through, while the solid remains in the funnel. 
 In transferring liquids from one vessel to another it is 
 best to pour the liquid down a glass rod (Fig. 20) as this 
 prevents danger of loss of the substance by 
 splashing. Direct the stream against the 
 side of the beaker or other vessel to which 
 the liquid is being transferred. When 
 pouring into a filter direct the stream 
 against the side of the filter having the 
 three layers of paper. 
 
 Keep the reagents pure by using ex- 
 treme care to prevent contamination of any kind. Do 
 not lay the stopper on the desk, but take it from the bottle 
 
 FIG. 21. 
 
INTRODUCTORY LABORATORY MANIPULATIONS 17 
 
 FIG. 22. 
 
 as shown in Fig. 21, holding both the bottle and the 
 stopper in the fingers as indicated in Fig. 22. Never pour 
 any liquid back into the reagent 
 bottle. A very little foreign sub- 
 stance in a reagent may spoil a 
 future experiment. Use small quan- 
 tities of all reagents. Many ex- 
 periments are ruined by the use of 
 too much material. 
 
 To collect gases the pneumatic trough is used (Fig. 23). 
 Any deep pan will serve the purpose. The bottle used to 
 
 collect the gas is filled 
 with water and placed 
 mouth downward in the 
 pneumatic trough. The 
 bottle is slightly tilted 
 so that the gas may enter 
 F IG . 23. at A and displace the 
 
 water in the bottle. Ex- 
 periment in collecting gases by placing a piece of tubing 
 under the bottle, as shown in the illustration, and gently 
 blowing into it. To remove the bottle of 
 gas from the trough slip a small piece of 
 window glass beneath the mouth of the 
 bottle (Fig. 24) while it is still under 
 water. If the gas is heavier than air, the 
 bottles should be stored mouth upward 
 with the glass plate on top. If the gas 
 is lighter than air, the bottles are kept 
 mouth downward. 
 
 Some gases are so soluble in water that some other method 
 than the one described above must be used in collecting 
 
 FIG. 24. 
 
18 INTRODUCTORY LABORATORY MANIPULATIONS 
 
 FIG. 25. 
 
 them. They may, in 
 many cases, be collected 
 over mercury, but the 
 method more commonly 
 used in the laboratory is 
 by displacement of air. 
 The gas is allowed to run 
 into the collecting vessel 
 until it has driven out all 
 or practically all of the 
 air. When the gas is 
 heavier than air it is col- 
 lected by downward dis- 
 placement (Fig. 25). If lighter than air, the gas is collected 
 by upward displacement (Fig. 26). 
 
 Cleanliness is abso- 
 lutely necessary to suc- 
 cessful laboratory work. 
 All apparatus should be 
 clean before use, and 
 should be washed as soon 
 as the experiment has 
 been completed. Direc- 
 tions should be carefully 
 followed in all the experi- 
 ments, and no exercise 
 should be started until 
 the entire procedure is 
 thoroughly understood by 
 the student. FIG. 26. 
 
CONTENTS 
 
 INTRODUCTORY LABORATORY MANIPULATIONS 
 
 PAGE 
 
 11 
 
 PART I: INORGANIC CHEMISTRY 
 
 CHAPTER 
 
 I. WATER 21 
 
 II. WATER (Continued} 34 
 
 III. HYDROGEN 45 
 
 IV. OXYGEN 52 
 
 V. OXYGEN (Continued] 61 
 
 VI. AIR NITROGEN 70 
 
 VII. SULPHUR 78 
 
 VIII. THE ATOMIC THEORY 91 
 
 IX. FORMULAS AND EQUATIONS. . . . . .97 
 
 X. Acros OF SULPHUR AND HYDROGEN SULPHIDE . 104 
 
 XI. CARBON Ill 
 
 XII. CARBON COMPOUNDS 123 
 
 XIII. LIMESTONE AND OTHER CALCIUM COMPOUNDS . 134 
 
 XIV. SALT: CHLORINE AND SODIUM .... 144 
 XV. ACIDS, BASES, AND SALTS 154 
 
 XVI. NITRIC ACID AND OXIDES OF NITROGEN . .161 
 
 XVII. AMMONIA AND ITS COMPOUNDS . . . .171 
 
 XVIII. PHOSPHORUS, PHOSPHORIC Aero, AND ARSENIC . 184 
 
 XIX. SAND, SILICON, AND BORAX 193 
 
 XX. RECOGNITION OF SUBSTANCES 201 
 
 XXI. POTASSIUM 204 
 
 XXII. MAGNESIUM AND ZINC 210 
 
 XXIII. ALUMINUM 214 
 
 XXIV. IRON 220 
 
 XXV. LEAD 226 
 
 XXVI. COPPER 230 
 
 XXVII. SILVER 235 
 
 XXVIII. REVIEW OF THE METALLIC SALTS RECOGNITION 
 
 OF THE COMMON METALS , 240 
 19 
 
20 
 
 CONTENTS 
 
 PART 
 
 CHAPTER 
 
 XXIX. 
 XXX. 
 
 II: ORGANIC AND APPLIED CHEMISTRY 
 COMPOUNDS OF CARBON WITH HYDROGEN 
 
 PAGE 
 
 244 
 250 
 
 XXXI. 
 
 ORGANIC ACIDS , 
 
 256 
 
 XXXII. 
 
 FATS, OILS, AND SOAPS ....... 
 
 263 
 
 XXXIII. 
 
 CARBOHYDRATES ....... 
 
 270 
 
 XXXIV. 
 
 ORGANIC NITROGEN COMPOUNDS . 
 
 280 
 
 XXXV. 
 
 COMPOSITION OF PLANTS ..... 
 
 289 
 
 XXXVI. 
 
 CHEMISTRY OF PLANT GROWTH .... 
 
 298 
 
 XXXVII. 
 
 CHEMISTRY OF PLANT GROWTH (Continued) . 
 
 309 
 
 XXXVIII. 
 
 ENZYMES DIGESTION FERMENTATION 
 
 317 
 
 XXXIX. 
 
 PRINCIPLES OF NUTRITION 
 
 324 
 
 XL. 
 
 FEEDING FARM ANIMALS ..... 
 
 331 
 
 XLI. 
 
 HUMAN FOODS 
 
 341 
 
 XLII. 
 
 MILK AND ITS PRODUCTS . 
 
 350 
 
 XLIII. 
 
 TESTING MILK ....... 
 
 364 
 
 XLIV. 
 
 LEAVENING AGENTS ...... 
 
 375 
 
 XLV. 
 
 FOOD PRESERVATION, ANTISEPTICS, AND DISIN- 
 
 
 
 FECTANTS 
 
 384 
 
 XLVI. 
 
 TEXTILES, DYEING, AND BLEACHING 
 
 392 
 
 XLVIL 
 
 PAINTS AND VARNISHES ....... 
 
 399 
 
 XLVIII. 
 
 CLEANING MATERIALS ...... 
 
 404 
 
 XLIX. 
 
 INSECTICIDES AND FUNGICIDES 
 
 411 
 
 
 PART III: SOILS AND FERTILIZERS 
 
 
 L. 
 
 SOIL FORMATION 
 
 420 
 
 LI. 
 
 KINDS OF SOILS . 
 
 426 
 
 LII. 
 
 RELATION OF THE SOIL TO PLANTS 
 
 433 
 
 LIII. 
 
 SOIL WATER ........ 
 
 440 
 
 LIV. 
 
 TILLAGE ......... 
 
 455 
 
 LV. 
 
 KEEPING THE SOIL SWEET . . . . 
 
 473 
 
 LVI. 
 
 ORGANIC MATTER ....... 
 
 485 
 
 LVII. 
 
 ROTATION OF CROPS 
 
 495 
 
 LVIII. 
 
 STABLE MANURE . . 
 
 501 
 
 LIX. 
 
 COMMERCIAL SOURCES OF PLANT FOOD . 
 
 520 
 
 LX. 
 
 MIXED FERTILIZERS 
 
 533 
 
 LXI. 
 
 TYPES OF FARMING AND FERTILITY 
 
 542 
 
 
 APPENDIX 
 
 
 
 TABLES ......... 
 
 549 
 
 
 INDEX ....0,0.. 
 
 553 
 
PART I 
 
 INORGANIC CHEMISTRY 
 
 CHAPTER I 
 
 WATER 
 
 1. WATER moves in an unending cycle. The heat of the 
 sun evaporates the water from the surface of rivers, lakes, 
 and oceans. The moisture thus added to the atmosphere 
 remains as water vapor until the air is cooled ; then it ap- 
 pears first as clouds, and finally is precipitated as rain. The 
 rain water soaks into the soil, later appears in springs, 
 rivers, and lakes, and is eventually returned to the ocean only 
 to repeat, over and over again, this unceasing round of 
 changes. 
 
 2. Water Never Pure in Nature. While water is very 
 abundant, it is never found in a pure state in nature. As 
 it soaks into the soil it dissolves many of the mineral sub- 
 stances found therein, and, as a result, the water issuing in 
 the springs and rivers contains dissolved mineral matter, 
 which is carried with it to the ocean. 'When water evapo- 
 rates, the dissolved solids remain, and, consequently, sea 
 water contains relatively large quantities of dissolved mat- 
 ter. All the salt and other mineral matter found in sea 
 water, therefore, was originally dissolved from the soil and 
 carried, by the streams to the ocean. That the water of 
 wells, springs, or rivers contains dissolved substances may 
 
 21 
 
22 
 
 INORGANIC CHEMISTRY 
 
 FIG. 27. Evaporating water to 
 show the presence of dissolved 
 mineral matter. 
 
 easily be shown by evaporating a small quantity to dryness 
 in a porcelain evaporating dish, as illustrated in Fig. 27. 
 
 If like amounts of water from 
 various sources are evaporated, it 
 will be found that there is a great 
 variation in the amount of solid 
 substance left in the evaporating 
 dishes. The' nature of the ma- 
 terials obtained from well and 
 spring water depends, evidently, 
 upon the character of the rock 
 and soil in which the well or 
 spring is located. Granite rocks 
 are very insoluble, while lime- 
 stone is much more readily dis- 
 solved. Water issuing from the former contains very little 
 dissolved substance, whereas it is a well-known fact that 
 the water in limestone regions is heavily charged with 
 mineral matter. 
 
 3. Rain Water the Purest Natural Water. The purest 
 natural water is rain water, but even that is not perfectly 
 pure. The atmosphere always contains more or less dust 
 and smoke, and when rain falls it carries these substances 
 down with it. Rain water in the open country is purer than 
 that in or near the cities, and if the water is not collected 
 until the air has been washed by the rain for some minutes, 
 comparatively pure water may be obtained. 
 
 4. Distillation of Water. Pure water is obtained by 
 boiling well water or hydrant water and condensing the 
 steam. This process is known as distillation and may con- 
 veniently be carried out in the apparatus shown in Fig. 28. 
 The water is boiled in the flask A, and the steam passing 
 
WATER 
 
 23 
 
 into the inner tube of the condenser B is cooled and changed 
 back to water, which is collected in the receiving flask C. 
 A current of cold water is kept running through the con- 
 denser, entering at D and flowing out at E. This water 
 cools the inner tube of the condenser sufficiently to cause 
 
 FIG. 28. Apparatus for the distillation of water. 
 
 the condensation of the steam entering from the flask A. 
 The water which collects in C is known as distilled water 
 and is quite pure, since the impurities of the original water 
 remain in the boiling flask. The first fifty cubic centime- 
 ters which pass over should be rejected, as gases and other 
 volatile substances may distill over with the first portions 
 of water, and the inside of the condenser may not be en- 
 tirely free from soluble materials. If proper precautions 
 have been observed, the distilled water made in this way 
 will leave no residue when evaporated in a porcelain dish. 
 
 5. Properties of Water. Pure water is tasteless and 
 odorless. In small quantities it seems to be colorless, but 
 when viewed in deep layers it becomes apparent that it has 
 
24 INORGANIC CHEMISTRY 
 
 a blue color. This is illustrated in the beautiful blue color 
 of many mountain lakes, which consist of almost pure 
 water derived from the melting snow. 
 
 6. Three States of Water. When water is boiled it is 
 gradually changed into a colorless and invisible vapor, 
 which, upon cooling, is again converted into liquid water. 
 If the vapor escapes into the cooler air, it is partially con- 
 densed and forms what is popularly known as steam. That 
 true steam, or water vapor, is invisible can be shown by 
 boiling water in a flask. It will be found that nothing can 
 be seen in the upper part of the flask although it must be 
 full of steam. It is only as the steam escapes into the air 
 and is condensed to small droplets of water that it can be 
 seen. 
 
 Most substances contract when they are cooled. Water 
 when cooled follows the general rule to four degrees centi- 
 grade, whereupon it begins to expand. At 4 C. water 
 reaches its maximum density. At the moment the water 
 freezes, a considerable increase in volume 
 takes place, and the resulting ice has a 
 density not much more than nine tenths 
 that of the water from which it was formed. 
 This explains why ice is always found on top 
 of the water. If the volume contracted as 
 freezing took place, ice would sink to the 
 bottom, and the lakes and rivers would be 
 frozen to a solid mass of ice. This expansion 
 
 FIG. 29. Bot- f ,-. p ' i f 
 
 tie broken by the of the water upon ireezing also accounts tor 
 omtaiiJed vnter* the fact that ice is always pushed up on the 
 banks of the lakes and rivers. The great force 
 exerted by the expansion of water at the moment of freezing 
 is well known, and nearly every one can recall an experience 
 
WATER 
 
 25 
 
 with the bursting of a water pipe, a bottle (Fig. 29), a bucket 
 or of some other vessel, due to the freezing of the con- 
 tained water. This force is also an important factor in the 
 weathering of rocks and in the formation of soils (483) . 
 
 7. Water used to Establish Standards. Pure water is 
 used to establish many of the scientific standards of measure- 
 ment. The two fixed points of the ther- 
 mometer are the boiling and the freezing 
 points of water. To graduate a thermome- 
 ter the bulb is placed in melting ice, and the 
 height of the mercury is marked. This 
 point is the zero of the centigrade scale, or 
 thirty-two degrees on the Fahrenheit scale 
 (Fig. 30). The thermometer is then im- 
 mersed in boiling water and the height of 
 the mercury again marked. This point is 
 marked 100 degrees centigrade, or 212 degrees 
 Fahrenheit. The space between these marks 
 is then divided into one hundred equal spaces 
 for the centigrade scale and into 180 for the 
 Fahrenheit. Since the boiling and the freez- 
 ing points of liquids vary with the atmos- 
 pheric pressure, the graduation described 
 above must be made at sea level, or be cor- 
 rected for the difference in pressure. In- 
 creased pressure raises the boiling point and 
 lowers the freezing point, while decreased pressure has the 
 opposite effect. That water under decreased pressure boils 
 at a lower temperature can readily be shown by boiling water 
 in a flask closed with a two-hole rubber cork, in one hole 
 of which is placed a thermometer, and in the other a tube 
 that is connected with an air pump (Fig. 31). If the air is 
 
 A B 
 
 FlQ. 30. Fah- 
 renheit (A ) and 
 centigrade (B) 
 thermometers 
 showing the rela- 
 tion of the scales. 
 
INORGANIC CHEMISTRY 
 
 partially exhausted from the flask, the water will be found to 
 boil much below 100 C. The same result may be obtained 
 
 FIG. 31. Apparatus to show effect of reduced pressure on boiling point of water. 
 
 by heating water in a flask, and, while the water is boiling 
 hard, closing the flask with a rubber stopper, and removing 
 the flask from the flame. If now a stream of water is run 
 
 over the upper part of the flask 
 (Fig. 32), the steam will be con- 
 densed, a. partial vacuum will be 
 produced, and the water will again 
 boil. This may be continued 
 until the temperature of the water 
 is much below its normal boiling 
 point. On the top of Pikes Peak 
 water boils at such a low tempera- 
 ture that an egg cannot be cooked 
 hard in it. 
 FIG. 32. A simple way of The gram, the standard of 
 
 showing the effect of reduced pres- . -. , , -. 
 
 sures on the boiling point. weight ot the metric system, is 
 
WATER 
 
 the weight of one cubic centimeter of water at its maximum 
 density ; that is, at 4 C. Water is also used as a standard 
 of density ; for the relative density, or specific gravity, of any 
 substance is determined by dividing its weight by that of 
 an equal volume of water. The standard for the measure- 
 ment of a quantity of heat is the calorie, which is the amount 
 of heat required to raise the temperature of one gram of 
 water 1 C. This is sometimes called the small calorie. 
 The large calorie is the amount of heat required to raise 
 1000 grams of water 1 C. 
 
 8. Heat of Fusion and Vaporization. When ice is heated 
 it melts, but if a thermometer is placed in the melting ice 
 (Fig. 33), and the mass is kept thoroughly stirred, it will be 
 found that the temperature of the 
 mass does not rise until all the ice 
 has been melted. Although much 
 heat has been applied, it has all 
 been used to melt the ice and not 
 to raise the temperature. The 
 heat required merely to melt a 
 substance is termed heat of fusion. 
 When the water freezes, the same 
 amount of heat is given off. Simi- 
 larly a large amount of heat is 
 required to change water into 
 vapor, or steam, and this is known 
 as the heat of vaporization of the 
 
 water. Whenever water evaporates it absorbs an amount of 
 heat equal to its heat of vaporization and, consequently, 
 cools both the air in the vicinity and the surface from which 
 evaporation takes place. This explains why sprinkling the 
 floor on a hot day cools the room. In India, wet cloths are 
 
 FIG. 33. The temperature of 
 the water does not rise until all 
 the ice is melted. 
 
28 
 
 INORGANIC CHEMISTRY 
 
 frequently hung in doorways, so that the air entering the 
 house will be cooled by evaporation of the water. Drink- 
 ing water in hot 
 climates is often 
 stored in semi- 
 porous earthenware 
 jars (Fig. 34) in 
 order that the water 
 oozing through may 
 evaporate from the 
 surface and thus 
 cool the jar and its 
 contents. 
 
 9. Water a Poor 
 Conductor of Heat. 
 It may be shown 
 that water is a poor 
 conductor of heat 
 by applying heat to 
 
 the top of a test tube full of water (Fig. 35) . The water in 
 the upper portion of the tube can be made to boil while the 
 bottom is still cool. To raise the temperature of a large body 
 of water it is necessary to apply heat at the bottom. When 
 the water next to the fire becomes heated, it expands, be- 
 comes less dense, and rises to the top (Fig. 36) . The cooler 
 and heavier liquid streams down to replace it, and thus a 
 system of currents is set up that gradually distributes the 
 heat throughout the whole mass. This statement applies to 
 other liquids and to gases as well as to water. 
 
 An interesting series of changes takes place when a pond 
 or other body of water freezes over. As the air above the 
 water becomes colder, heat is given off from the surface of 
 
 FIG. 34. Semi-porous water jars on sale in a 
 bazaar in Allahabad, India. 
 
WATER 
 
 29 
 
 FIG. 35. Showing that water is 
 a poor conductor of heat. 
 
 the water, and the cold water from above streams down to 
 
 the bottom of the pond and forces the warmer water to come 
 
 to the surface. This continues 
 
 until all the water in the pond 
 
 is cooled to 4 C. Upon further 
 
 cooling the water at the surface 
 
 expands, thus becoming lighter, 
 
 and no longer moves downward. 
 
 When the surface is cooled to 
 
 C., the water freezes, giving off an 
 
 amount of heat equal to its heat 
 
 of fusion, and the temperature 
 
 of the water immediately below 
 
 the ice is temporarily raised. The 
 
 layer of ice increases in thickness 
 
 due to the loss of heat from the surfa:e until it is sufficiently 
 
 thick to prevent further radiation of heat from the water 
 
 beneath, ice being a relatively 
 poor conductor of heat. It thus 
 happens in deep ponds that the 
 water at the bottom does not fall 
 to the freezing point, even in very 
 cold weather. 
 
 10. Water Has High Specific 
 Heat. Water requires more heat 
 to make it hot than does any other 
 substance. If equal amounts of 
 heat are applied to equal masses 
 of water and mercury, for in- 
 stance, the mercury gets hot much 
 
 more rapidly than the water. Water, therefore, is said to 
 
 have a greater capacity for heat, or a greater specific heat, 
 
 FIG. 36. Currents of warm 
 water move upward as the bottom 
 layers are heated. 
 
30 
 
 INORGANIC CHEMISTRY 
 
 than other substances. This property of water is of im- 
 portance, for substances that heat slowly also cool slowly. 
 This is one reason why hot water and steam are used to heat 
 houses, and explains why large bodies of water have a 
 moderating effect upon the climate of their vicinity. 
 
 EXERCISES 
 
 Ex. 1. Evaporate 10 cc. each of well water and rain water to dry- 
 ness by heating in glass dishes or watch glasses on a sand bath (Fig. 37). 
 
 What remains in the dish? Which 
 water gave the larger residue ? Which 
 sample of water was the purer ? Was 
 either one perfectly pure? How did 
 the residue in the dish get into the 
 water? From which well should you 
 expect the most residue, one located 
 in granite, sandstone, or limestone? 
 Why? Why does sea water contain 
 large quantities of salt and other min- 
 eral matter? Where does the mineral 
 matter in sea water come from ? Ex- 
 plain the cycle of water in nature. 
 
 Ex. 2. Arrange an apparatus ac- 
 cording to Fig. 28. Half fill the flask 
 A with the well water used in Ex. 1 
 
 and boil until 50 cc. of water is collected in C. Evaporate 10 cc. of 
 the distilled water to dryness as above. Is there any residue ? Com- 
 pare with the well water before distillation. What has become of 
 the mineral matter that was in the well water ? How is pure water 
 obtained ? 
 
 (Note. If the condenser shown in Fig. 28 is not available, sufficient 
 distilled water for this test can be produced with the apparatus shown in 
 Fig. 38. Surround the test tube with the coldest water obtainable. 
 If ice is available to cool this water, more distilled water can be pro- 
 duced.) 
 
 FIG. 37.. Evaporating a small 
 quantity of water on a watch 
 glass. 
 
WATER 
 
 31 
 
 FIG. 38. A simple apparatus for 
 producing a small quantity of distilled 
 
 water. 
 
 Ex. 3. Add a few crystals of copper sulphate to the water in flask 
 A and distil a few cubic centimeters of water. What is the color of the 
 water in the flask A ? What is the 
 color of the distilled water (some- 
 times called the distillate) ? Explain 
 the difference. In producing pure 
 distilled water why should the first 
 water that distilled over be rejected ? 
 State the properties of pure water. 
 
 Ex. 4. Boil some water in a flask 
 which is open at the top. Is the 
 vapor in the upper part of the flask 
 visible? Why does the "steam" 
 become visible when the vapor 
 passes into the air? Use a ther- 
 mometer to determine the tempera- 
 ture of the water vapor (Fig. 39). 
 
 Ex. 6. If the weather is sufficiently cold, place a bottle full of 
 water out of doors to freeze. Does water contract when cooled? 
 
 What happens when the water freezes ? 
 Why does ice float on top of the water ? 
 What would happen to lakes if ice 
 were heavier than water? At what 
 temperature is water at its maximum 
 density ? 
 
 Ex. 6. Boil water in a partial 
 vacuum created by an air pump, as 
 suggested in the text. At what tem- 
 perature does the water boil ? At what 
 temperature did' it boil in Ex. 4? Ex- 
 plain the difference. What is the ele- 
 vation of your school above sea level ? 
 Should you expect water to boil in your 
 laboratory at 100 C. or below ? Why ? 
 . Ex. 7. Fit a flask with a good rub- 
 ber stopper and place in the stopper 
 Attach a piece of rubber tubing and a 
 Boil the water in 
 
 FIG. 39. Determining the tem- 
 perature of water vapor.' <$$>& 
 
 a short piece of glass tubing-. 
 
 pinchcock to the upper end of the glass tubing. 
 
32 
 
 INORGANIC CHEMISTRY 
 
 the flask until all air is driven out, and while the water is still boiling 
 close the pinchcock and immediately remove the flame. Now run cold 
 water over the upper part of the flask. Explain what happens to th'3 
 water in the flask. Why does it take longer to cook vegetables by boil- 
 ing at high altitudes than at sea level ? If the flask used in this exercise 
 were strong enough to risk boiling the water after the cork was inserted, 
 would the boiling point of the water be raised or lowered ? Why ? 
 
 Ex. 8. Place a beaker or tin cup of water over a burner and watch 
 the rise of temperature of the water by means of a thermometer. Does 
 the temperature begin to rise immediately? Try the experiment 
 again, using water with ice in it. Does the tem- 
 perature rise immediately in this case ? Explain 
 the difference. 
 
 Ex. 9. Cool a pound of water (1 pint) to zero 
 by immersing the vessel in a mixture of ice and 
 salt until the desired temperature is reached; 
 then remove from the cooling mixture. Have 
 another pint of water heated to 80 and pour into 
 the water at zero. Stir it quickly with the ther- 
 mometer and read the temperature. What is the 
 temperature of the mixture? 
 
 Weigh one pound of ice and pour over it a pint 
 of water which has been warmed to 80. Stir 
 and read the temperature as soon as the ice has 
 melted. What is the temperature in this case? 
 How do you explain the difference in the two 
 parts of this exercise? (Note that the ice used 
 in this experiment must be at C. Can ice 
 be colder than zero ? If all conditions are right 
 for the above experiment, the mixture of water 
 at 80 and water at zero will have a temperature 
 of 40, while the mixture of water at 80 and ice at zero will have a 
 temperature of zero. Eighty times as much heat is required to melt 
 a pound of ice as is required to warm a pound of water one degree.) 
 What is meant by heat of fusion? What becomes of the heat of 
 fusion when the water freezes? When there is danger of freezing it 
 is sometimes suggested that a tub of water be placed in the cellar. 
 What is the theory of this recommendation ? 
 
 FIG. 40. Wet and 
 dry bulb thermome- 
 ters to show the effect 
 of evaporation on the 
 temperature. 
 
WATER 33 
 
 Ex. 10. Compare two thermometers to see that they register alike. 
 Wrap a piece of thin cloth around the bulb of one and moisten it with 
 water (Fig. 40). Fan the two thermometers and observe the change in 
 temperature registered. Is there any difference in the two thermome- 
 ters ? Explain. Why does sprinkling the floor lower the temperature of 
 the room ? Explain the use of porous jars to cool water in hot climates. 
 Can you think of any other instance of the cooling effect of evaporating 
 water ? 
 
 Ex. 11. Fill a long test tube with water and heat the upper part 
 over a burner until the water boils. Is the lower part of the tube hot ? 
 How do you explain it? Where should the heat be applied to warm 
 water with the least fuel ? Explain. Explain the changes that take 
 place in the freezing over of a pond. What is meant by specific 
 heat? How does the specific heat of water compare with that of 
 other substances ? Is there any connection between this fact and the 
 use of hot water and steam in heating buildings ? Explain the moder- 
 ating effect which large bodies of water have upon climate. 
 
 EV. CHEM. 3 
 
CHAPTER II 
 
 WATER (Continued) 
 
 11. Water the Best Solvent. Water is the best-known 
 solvent. In other words, it will dissolve more substances 
 than any other liquid. There are some substances, how- 
 ever, which are insoluble in water. Substances vary greatly 
 in solubility, ranging from those which will dissolve in a 
 fraction of their own weight of water, to those whose solu- 
 bility can scarcely be detected. Water dissolves other 
 
 liquids and gases as well as solid 
 substances. Liquids which are 
 soluble in water are said to be 
 miscible with water. Alcohol is 
 miscible with water in all pro- 
 portions, and so is sulphuric acid. 
 Oils, on the other hand, are prac- 
 tically insoluble in water. The 
 fact that air and other gases are 
 dissolved in natural waters can 
 be shown by gently heating the 
 water in a glass vessel (Fig. 41), 
 whereupon bubbles of gas will be 
 seen to separate. The solubility of substances in water is 
 affected by temperature. As a general rule, the solubility 
 of solids increases with the rise of temperature, while that 
 of gases decreases. Increase of pressure has a very marked 
 effect upon the solubility of gases in water, for the amount 
 
 34 
 
 Flo. 41 . Warming water to show 
 the presence of dissolved gases. 
 
WATER 35 
 
 of gas dissolved is directly proportional to the pressure; 
 that is, if the pressure upon the gas is doubled, twice as much 
 will be dissolved by the water. 
 
 12. Dissolved Substances Raise the Boiling Point of 
 Water. Substances dissolved in water raise its boiling 
 point and lower its freezing point. Water in which salt 
 is dissolved, for instance, has to be heated above 100 C. be- 
 fore it will boil, and it will not freeze until much below 
 C. This effect of the dissolved substance is made use of 
 in a number of practical ways, some of which will be re- 
 ferred to later. When the water contains all of the sub- 
 stance it can dissolve, the solution is said to be saturated. 
 From what has been said above it will be seen that a solu- 
 tion which is saturated at a low temperature will no longer 
 be saturated if the temperature is raised, and that more of 
 the substance may then be dissolved. Conversely, if the 
 temperature of a saturated solution is lowered, some of the 
 dissolved substance will be thrown out of the solution. 
 
 13. Water Accelerates Chemical Action. Water is also 
 of interest to the chemist because it hastens chemical changes. 
 In fact, most of the important chemical changes will not 
 take place at all in the absence of water. If a small quan- 
 tity of dry baking soda and dry powdered tartaric acid are 
 mixed in a beaker, no change will take place. If, however, 
 a little water is added, a marked change takes place, the 
 most noticeable thing being the large amount of gas that is 
 evolved. The rusting of iron is another example of a chemi- 
 cal change which occurs only in the presence of moisture. 
 
 14. Potable Waters. What is popularly meant by a 
 pure water is one that is fit to use for drinking purposes. 
 Such a water is technically called a potable water. Sea water 
 with its large amount of salt is obviously unfit to drink, but 
 
36 
 
 INORGANIC CHEMISTRY 
 
 it is seldom indeed that the mineral substances found in well 
 or spring water are injurious. The chief source of danger in 
 drinking water is that it may be contaminated (Fig. 42) 
 
 with sewage, if the 
 source of the water 
 is near human habi- 
 tations. The water 
 from cesspools may 
 enter the well or 
 spring, or the city 
 sewage may be 
 emptied into the 
 river. In either case 
 disease-producing 
 bacteria find their 
 
 FIG. 42. --The contamination of water. Way into the drink- 
 
 ing water. Typhoid 
 
 fever and other diseases are often spread in this way. Wells 
 should not be dug or drilled close to cesspools, for water from 
 the surrounding soil is likely to drain into them. Deep 
 wells are less likely to be contaminated than shallow ones, 
 but in any case the upper part of the veils should be made 
 water tight so that no surface water can enter. The water- 
 tight casing should be carried down to a layer of clay or 
 stone through which the surface water cannot penetrate. 
 A spring at the foot of a hill is often contaminated from 
 a cesspool on the hillside above. 
 
 15. Boiled Water for Drinking. In case water is sus- 
 pected of contamination the only safe thing to do is to boil 
 it, and thereby kill the bacteria. Many filtering devices are 
 offered for sale, but no small household filter can be de- 
 pended upon to remove all the disease-producing bacteria. 
 
WATER 37 
 
 In the case of city water supply large filtering beds may be 
 constructed which will purify the water, but even these 
 require the constant care of the expert engineer to keep them 
 working effectively. Boiled water has a flat taste because 
 of the fact that the air and other gases have been driven 
 out by the boiling process. The taste of such water may be 
 improved, however, by beating air into it after it has been 
 thoroughly cooled. Rain water, or cistern water, collected 
 in the open country, may be used for drinking purposes with 
 safety, if the rain is first allowed to wash the roof, and the 
 cistern is carefully protected to prevent contamination. 
 
 16. Hard Water. Water which contains a large amount 
 of mineral matter is known as hard water. With such 
 waters, soap, instead of forming suds, produces a curd which 
 floats on top. Hardness is for the most part caused by lime 
 compounds that are dissolved in the water. If the water 
 is boiled, some of these lime compounds are made insoluble 
 and separate, leaving the water less hard than it was. Hard- 
 ness which can be removed by boiling is known as temporary 
 hardness, while that which cannot be so removed is called 
 permanent hardness. These terms will be more fully ex- 
 plained in a later chapter. Hard water is unsuited to house- 
 hold use because so much more soap is required with it 
 than with soft water. This may be illustrated by a sim- 
 ple experiment. Equal quantities (25 cc.) of distilled 
 water, rain water, fresh well water, and boiled well water 
 are placed in four 8-ounce bottles. A one per cent solu- 
 tion of a pure soap (in alcohol) is added to each bottle, 
 a drop at a time, and the bottle is vigorously shaken after 
 each addition. It will be found that almost the first drop 
 will make suds with the distilled water ; that a little more 
 will be required with the rain water; and that the well 
 
38 
 
 INORGANIC CHEMISTRY 
 
 water will require much more than either the distilled or 
 the rain water. The boiled well water will produce suds 
 with less soap than the fresh well water. 
 
 Hard water is not satisfactory for use in boilers, for the 
 mineral matter in such water forms a crust or scale on the 
 inside of the boiler much like that found on the inside of a 
 teakettle when well water is used. In limestone countries, 
 especially, it becomes necessary to soften the water before it 
 can be used in the boilers. This is done by the addition of 
 boiler compounds made of various chemicals which will 
 throw the lime or calcium salts out of solution. Borax, 
 washing soda, quicklime, sodium phosphate, and other 
 chemicals are used for this purpose. 
 
 17. Mineral Waters. Mineral waters are not neces- 
 sarily heavily charged with mineral matter, but usually 
 contain rather large amounts of one substance which gives 
 them their peculiar characteristics. Some contain mag- 
 nesium compounds, others are noted for the iron they con- 
 tain, and still others are so 
 charged with carbon dioxide that 
 they effervesce like soda water. 
 Sulphur water and lithia waters 
 are also found in nature. 
 
 18. Water in Organic Matter. 
 The sources of water heretofore 
 mentioned, such as wells, rivers, 
 and lakes, are obvious; but 
 water also exists under conditions 
 
 FIG. 43. -Showing the presence not SO apparent. It is Well known 
 of water in organic matter. ^^ p l an t s and animals US6 large 
 
 quantities of water during their growth, and that some of 
 the water remains in the organism. If a small quantity 
 
WATER 39 
 
 of grass, potato, turnip, corn, or a bit of lean meat is heated 
 gently in a test tube, as shown in Fig. 43, the escaping water 
 will be condensed in droplets at the top. of the tube. Vege- 
 tables like beets, carrots, turnips, and potatoes are 90 
 per cent water. If the body of a calf weighing 150 pounds 
 were completely dried, it would be found to weigh only 
 about 50 pounds. In other words, such a body is nearly 
 two thirds water. 
 
 19. Water of Crystallization. If a crystal of Glauber's 
 salt (sodium sulphate) is heated in a test tube, water will be 
 driven off and the crystal will change to a powder. It may 
 be inferred from this experiment that the crystal contained 
 water, and that the water was in some way necessary to pro- 
 duce the crystalline form. If a crystal of blue vitriol (cop- 
 per sulphate) is heated, not only will water be driven off and 
 the crystalline form be destroyed, but the blue color will 
 disappear as well, leaving a grayish white mass. A little 
 water added to this mass will restore the blue color, and if 
 the material is dissolved in a small quantity of hot water 
 and allowed to stand, blue crystals will again be formed. 
 Water which thus forms a part of the crystal is known as 
 water of crystallization. Not all crystals contain water, 
 however, as some compounds crystallize without water of 
 crystallization. Quartz and potassium dichromate are 
 examples of such compounds. 
 
 20. Efflorescence and Deliquescence. If a bright crys- 
 tal of washing soda is allowed to stand exposed to the air, 
 it gradually gives off a part of its water of crystallization and 
 crumbles to a white powder. Crystals which thus give off 
 their water at ordinary temperatures are said to effloresce. 
 Other substances have such a strong attraction for water 
 that they will take it from the air until they actually dis- 
 
40 
 
 INORGANIC CHEMISTRY 
 
 solve in the absorbed water. Such materials (of which 
 calcium chloride is a good example) are said to deliquesce. 
 Substances which rejnove water so readily from the air will 
 be found to be useful in drying gases. 
 
 21. Water May Be Decomposed. Water exists in 
 three different forms solid, liquid, and gaseous water. 
 These differences, however, are purely physical. Ice may 
 be melted to water, and the water heated to steam and dis- 
 tilled, and, under proper conditions, the process may be 
 
 FIG. 44. Apparatus for the decomposition of water. 
 
 reversed. The same quantity of water may pass through 
 this cycle of changes an indefinite number of times, but it 
 will still be water. If the steam shown in Fig. 28 instead 
 of being cooled in the condenser is passed over certain heated 
 metals, a marked change takes place, as can be easily dem- 
 onstrated by the following experiment : 
 
 A small quantity of powdered zinc is placed in the hard 
 glass tube B in Fig. 44. The flask A is one third full of 
 water and the bottle C is filled with water and inverted in 
 the dish D. The water in A is boiled until the steam has 
 
WATER 41 
 
 driven all the air out of the apparatus, and then the burners 
 are lighted under the hard glass tubing B. When the zinc 
 becomes hot the end of the rubber tubing E is slipped under 
 the mouth of the bottle C. Bubbles of gas will soon enter 
 the bottle. When the bottle is filled with the gas, the rubber 
 tubing is withdrawn and the flames are extinguished. 
 
 The gas in the bottle is colorless and as far as outward 
 appearance goes might be air. It cannot be steam ; for if it 
 were, it would be cooled by the water and condensed. If 
 the bottle is carefully lifted mouth down and a lighted splint 
 or candle is introduced, the gas will ignite and burn with a pale 
 blue flame. Clearly here is a gas which has been obtained 
 from the water but which has none of the characteristics of 
 water. The heated zinc has decomposed the water, and this 
 gas is one of the resulting products. This gas was first dis- 
 covered by the English investigator Cavendish in 1766. It 
 was named hydrogen by the French chemist, Lavoisier, be- 
 cause it is one of the constituents of water. 
 
 EXERCISES 
 
 Ex. 12. Add one gram of salt to a test tube of water. Do the same 
 with pure sand. What difference do you notice? Are all substances 
 soluble? Try a little gypsum (calcium sulphate). Can you prove 
 that any of it dissolves ? Are all soluble substances equal in solubility ? 
 
 Ex. 13. Add 1 cc. of alcohol to 10 cc. of water. Do the same 
 with coal oil. What difference do you notice? What is meant by 
 the statement that a liquid is miscible with water ? 
 
 Ex. 14. Heat some well water or tap water in a beaker. What 
 are the bubbles that appear ? Are gases soluble in water ? How does 
 pressure affect the solubility of gases in water? How does rise of 
 temperature affect the solubility of gases ? Of solids ? 
 
 Ex. 15. Dissolve ten grams of salt in 100 cc. of water in a flask 
 and heat the solution to boiling. Determine the temperature of the 
 solution. How does the dissolved salt affect the boiling point ? Wipe 
 
42 INORGANIC CHEMISTRY 
 
 off the thermometer and test the temperature of the steam above the 
 water. What is the temperature? To fix the 100 point in a ther- 
 mometer, would it be best to put the bulb in the boiling water or in 
 the steam? If salt were placed in the water in the outer pan of a 
 double boiler, what effect would it have on -the temperature of the 
 material being cooked in the inner pan ? 
 
 Ex. 16. Mix one gram of bicarbonate of soda with a like amount 
 of dry powdered tartaric acid. Do you notice any change? Add a 
 few drops of water. What change do you notice now? What effect 
 does water have on chemical action? 
 
 Ex. 17. What is meant by a potable water ? Is the mineral matter 
 in well water ordinarily injurious ? What is the chief source of danger 
 in drinking water ? Why should wells never be near cesspools ? Which 
 are safer, deep or shallow wells? How should wells be protected at 
 the surface? How can contaminated water be made safe to drink? 
 Is cistern water ever fit for drinking ? 
 
 Draw a plan, where well or spring water is used, showing the 
 location of your water supply and its distance from cesspools, manure 
 piles, or other possible sources of sewage contamination. Observe 
 also whether the natural drainage slope from such sources of con- 
 tamination is towards or away from the water supply. Do you find 
 that a safe or an unsafe condition exists? Can unsatisfactory condi- 
 tions be improved by change in location, or in a modification of the 
 direction of drainage? Draft a plan which if applied would be an 
 improvement on the present arrangement. What is the only safe 
 course to pursue with reference to drinking water when changes in 
 present conditions cannot be made ? 
 
 Ex. 18. Make fine shavings of Castile soap and dissolve .5 gram in 
 50 cc. of alcohol. Place 25 cc. of rain water in an 8-oz. bottle. By 
 means of a medicine dropper add the soap solution, one drop at a 
 time, to the water and shake vigorously after each addition. Continue 
 until a suds is formed which will stand for at least a minute. Record 
 the number of drops of soap solution used. Repeat the experiment 
 with distilled water, well water, and boiled well water. Which water 
 required the most soap? Which the least? Why is rain water pre- 
 ferred to well water in the laundry ? Was there any difference between 
 the boiled and the unboiled well water ? What is meant by hardness of 
 water? By temporary hardness? By permanent hardness? Ex- 
 
WATER 
 
 43 
 
 amine the inside of the teakettle at home. Is there any mineral 
 matter on the inside of the kettle ? How do you account for it ? Would 
 you expect more scale in the kettle in a sandstone country or in a lime- 
 stone country ? What are mineral waters ? 
 
 Ex. 19. Heat small quantities of grass, potato, or other vegetables 
 in a test tube (Fig. 43). What do you notice? Repeat the experi- 
 ment with a bit of lean meat. What can you say about water in 
 organic matter? 
 
 Ex. 20. Select a clear crystal of sodium sulphate and heat in a test 
 tube. Does water come off? What is this water called? What has 
 happened to the crystal ? Repeat the experiment with a crystal of cop- 
 per sulphate. What happens to this crystal ? Has the color changed ? 
 Add a few drops of water. What happens to the color ? Dissolve in a 
 
 FIG. 45. A simple apparatus for decomposing water by means of zinc dust. 
 
 small quantity of hot water and set aside to crystallize. Do the crystals 
 resemble the one you started with ? Is water necessary to all crystals ? 
 Heat a crystal of potassium bichromate. What do you observe in this 
 case? 
 
 Ex. 21. Select a bright crystal of washing soda and allow it to 
 stand exposed to the air for several hours. What happens to the 
 crystal? What term is used for such substances? Try the same 
 experiment with calcium chloride. What do you observe in this case ? 
 What term is used for such substances? 
 
44 INORGANIC CHEMISTRY 
 
 Ex. 22. Arrange apparatus as in Fig. 44. The tube B may be of 
 hard glass or it may be a piece of one-half-inch iron gas pipe. Place 
 powdered zinc in the tube. Boil the water in the flask A so that 
 steam will pass over the zinc, which is heated to low redness by the 
 burner beneath. The air is first driven out, and then pure steam 
 passes over. Finally when the zinc becomes hot gas begins to ap- 
 pear. Collect one or two bottles of gas in the manner described in 
 Section 21. What is the appearance of the gas? Carefully lift the 
 bottle and apply a lighted splint to the mouth. What happens? 
 What is the name of this gas ? Who first discovered it ? 
 
 Note. This experiment may be conducted in the apparatus shown 
 in Fig. 45. A is a hard glass test tube. Zinc dust is placed at B. 
 The steam from C is decomposed in the same way as in Ex. 22. This 
 experiment is made more striking if magnesium tape is used in the 
 place of the zinc, as the magnesium can be seen to burn in the steam. 
 A piece of magnesium tape one foot long will furnish sufficient gas 
 to fill an 8-oz. bottle. 
 
CHAPTER III 
 HYDROGEN 
 
 22. Preparation. Hydrogen may be prepared by passing 
 steam over heated zinc, iron, or other metals in the manner 
 described in the preceding chapter, but these methods are 
 not convenient when the gas is required in large quantities. 
 The preparation of hydrogen in the laboratory is usually 
 
 a 
 
 FIG. 46. Apparatus for the preparation of hydrogen. 
 
 accomplished by the action of sulphuric acid on zinc or iron. 
 Zinc is ordinarily employed because most samples of iron 
 contain impurities which contaminate the hydrogen. In the 
 wide-mouth bottle A (Fig. 46) there is placed a small quan- 
 tity of granulated zinc, and water is poured into the thistle 
 tube B until the zinc is covered. The end of the thistle 
 tube must be beneath the water. Dilute sulphuric acid 
 is then poured down the thistle tube. An active evolution 
 
 45 
 
46 
 
 INORGANIC CHEMISTRY 
 
 of gas takes place, and when sufficient time has elapsed 
 for the hydrogen to drive all the air out of the apparatus, 
 the gas is collected over water in the wide-mouth bottle D. 
 The hydrogen in this case is contained in the sulphuric acid 
 and is replaced or driven out by the zinc. 
 
 23. Properties. Hydrogen is a gas that has no taste, 
 color, or odor. It will burn readily, and when it is mixed 
 with air the combustion takes place with an explosion. Hy- 
 drogen is the lightest known substance and weighs less than 
 
 one fourteenth as much 
 as air. For this reason 
 it was used formerly to 
 fill balloons; but it is 
 now largely superseded 
 by ordinary illuminating 
 gas, which is less expen- 
 sive. It is still used for 
 the airship or dirigible 
 balloon. That hydro- 
 gen is lighter than air is shown by the fact that it can 
 be poured upwards. A bottle full of hydrogen is gradually 
 turned mouth upward beneath an inverted bottle filled with 
 air (Fig. 47). If after a minute or two a lighted splint is 
 applied to the mouths of the two bottles, it will be found 
 that the hydrogen has passed out of the bottle A into B. 
 The same thing is shown by blowing soap bubbles with hydro- 
 gen ; in which case, owing to the lightness of the gas, the 
 bubbles will rise rapidly in the air. 
 
 24. When Hydrogen Burns Water is Formed. The 
 apparatus shown below may be used to study the behavior 
 of hydrogen when burning quietly in the air (Fig. 48). 
 
 The bottle A is the hydrogen generator already described. 
 
 FIG. 47. Pouring hydrogen upwards. 
 
HYDROGEN 
 
 47 
 
 B is a tube containing calcium chloride to dry the hydrogen. 
 After the gas has been carefully tested to make sure that all 
 air has been driven out of the apparatus, the jet is ignited 
 
 FIG. 48. Apparatus for showing behavior of hydrogen when burning in the air. 
 
 at C. The flame will be found to be intensely hot. Pure 
 hydrogen burns with a pale blue flame, but in such an appa- 
 ratus it is likely to be colored yellow by the sodium in the 
 glass. If a bell jar or a large bottle is held in the position 
 shown by D, moisture will collect on the interior until it 
 runs down the sides as indicated. When hydrogen is burned, 
 water is always produced. 
 
 25. Occurrence. Hydrogen is not found in nature in 
 the free state except in the merest traces. It is, however, 
 very abundant and very widely distributed in combination 
 with other substances. It is found in water as has been 
 shown, and it is also a part of nearly all animal and vege- 
 table substances. Crude petroleum and all the products 
 made therefrom contain hydrogen. When any substance 
 containing hydrogen is burned in air, water is formed, as can 
 
48 INORGANIC CHEMISTRY 
 
 be shown by holding a cold bottle or piece of glass over the 
 flame of a candle, kerosene lamp, or gas jet. Candles, kero- 
 sene, and gas all contain hydrogen, and a film of moisture 
 will be deposited on any cold surface held above the flame. 
 
 26. Water Contains Something Besides Hydrogen. In 
 the experiment described in section 21, it was shown that 
 hydrogen could be prepared from water. This gas is so 
 different from water, however, that water must contain 
 something in addition to hydrogen ; or, in other words, 
 hydrogen is combined with something else to form water. 
 An examination of the zinc in the hard glass tube will show 
 that part of it has changed in appearance, an occurrence 
 which indicates that something from the water has combined 
 with the zinc. It will be interesting to try to ascertain 
 what the other substance or substances in water may be. 
 
 27. Electrolysis of Water. Water and many other sub- 
 stances can be decomposed by the electric current. The 
 effect of the electric current on water can be readily 
 shown in the apparatus illustrated in Fig. 49. Platinum 
 wires, to the ends of which are attached pieces of platinum 
 foil, are fused into the tubes B and C. The stopcocks 
 at the top of the tubes are opened, and the apparatus is 
 filled with water containing about one tenth of its volume 
 of sulphuric acid. The water is put into the apparatus at 
 A. The sulphuric acid is used because pure water will not 
 conduct electricity. The stopcocks are now closed, and 
 the platinum wires in the tubes B and C are connected with 
 wires leading to a battery. Three or more dry cells, or two 
 or three dichromate cells, will serve the purpose. As soon 
 as the current begins to pass through the water, bubbles of 
 gas will be noticed passing from the platinum foil to the 
 upper part of the tube. It will be seen that more gas col- 
 
HYDROGEN 
 
 49 
 
 lects in one tube than in the other, and it will soon be appar- 
 ent that one tube contains exactly twice as much gas as 
 the other. Both of the gases must have come from water, 
 for a careful analysis would show that all the sulphuric acid 
 added still remains in the 
 apparatus. 
 
 The larger volume is on 
 the side connected with the 
 negative pole of the battery. 
 When this tube is nearly full 
 of the gas, the battery is dis- 
 connected and the gases are 
 examined. By attaching a 
 small rubber tube to the tip 
 of the stopcock the gases 
 may be collected in test 
 tubes over water in the usual 
 way. The gas from the side 
 containing the double vol- 
 ume burns in such a way as 
 to show that it is hydrogen, 
 but the other gas behaves 
 quite differently. It does 
 not burn, but if a splint with 
 a glowing coal on the end is 
 thrust into the test tube 
 containing this gas, it will burst into a flame. Here, then, is 
 a new gas which does not burn, but which causes the splint 
 to burn more vigorously than it did in the air. 
 
 This gas was discovered at about the same time (1774-75) 
 by the English chemist Priestley and the Swedish chemist 
 Scheele, although each was working independently. Lavoi- 
 
 EV. CHEM. 4 
 
 FIG. 49. Method of decomposing 
 water by the electric current. 
 
50 INORGANIC CHEMISTRY 
 
 sier, the French chemist, gave it the name oxygen (meaning 
 acid-former), because he thought that all acids owed their 
 properties to this substance, a view now known to be incor- 
 rect. 
 
 EXERCISES 
 
 Ex. 23. Arrange apparatus as in Fig. 46. A is an 8-oz. wide-mouth 
 bottle. Place 10 grams of granulated zinc in this bottle and add suffi- 
 cient water to cover the zinc and the end of the thistle tube. Prepare 
 dilute sulphuric acid by slowly pouring 15 cc. of the strong acid into 
 50 cc. of water, stirring constantly. Never pour the water into the 
 acid. Now pour a little of the dilute acid down the thistle tube. 
 
 (Note. Chemically pure zinc and sulphuric acid will not react. 
 It is advisable, therefore, to add a few drops of a solution of copper 
 sulphate to the water in the bottle A.) 
 
 Acid is added from time to time to keep up a steady flow of gas. 
 After the air has all been driven out of the apparatus collect four 
 bottles of the gas. What was the source of the hydrogen? Describe 
 the appearance of the gas. 
 
 Ex. 24. Hold a bottle of the gas mouth downward and apply a 
 lighted splint. Describe the result. What does this prove about the 
 gas? 
 
 Ex. 25. Fill a 2-oz. wide-mouth bottle half full of water, invert in 
 the pan of water, and fill with hydrogen. What does the bottle con- 
 tain? Hold it at arm's length, mouth downward, and ignite over a 
 candle or burner. What happens ? What does this prove ? 
 
 Ex. 26. Gradually turn a bottle of hydrogen mouth upward under 
 a similar bottle filled with air (Fig. 47). After a minute apply a 
 lighted splint to both bottles. Describe the results. Is hydrogen 
 lighter or heavier than air ? 
 
 Ex. 27. Arrange apparatus as in Fig. 48. Add the dilute sul- 
 phuric acid, and when hydrogen has been evolved for some minutes 
 test the purity of the gas by collecting test tubes of the gas and igniting 
 them, mouth downward. If all air is out of the apparatus, the hydrogen 
 will burn quietly ; otherwise it will explode. When you are sure that 
 only pure hydrogen is coming off, wrap a towel around the bottle and 
 
HYDROGEN 51 
 
 ignite at C. Test the heat of the flame by holding a piece of iron in 
 it. Hold a large wide-mouth bottle or bell jar over the flame. What 
 is the result ? What is formed when hydrogen burns ? 
 
 Ex. 28. Hold a wide-mouth bottle or a bell jar over the flame of a 
 candle, an alcohol lamp, or a gas 'burner, at home. Does moisture 
 collect on the side of the bottle ? What is the source of the moisture ? 
 
 Ex. 29. Fill the apparatus shown in Fig. 49 with water containing 
 one tenth its volume of sulphuric acid. Connect the platinum wires 
 with a battery (four dry cells will do) and watch the gas collect in the 
 two arms of the apparatus. Which side contains the most gas ? With 
 which pole of the battery is it connected ? What is the source of these 
 two gases? When the tube containing the larger quantity of gas is 
 nearly full, disconnect the battery. Place a piece of small rubber 
 tubing over the tip of the stopcock on the tube containing the double 
 quantity of gas and collect the gas in a test tube over water. Test it 
 with a flame. What is this gas? Collect the gas from the other side 
 in the same way. Test it by holding the test tube mouth upward 
 and thrusting into it a splint with a glowing coal on the end. What 
 happens in this case? Does this gas behave like hydrogen? What 
 name has been given to this gas? Who discovered it? By whom 
 was it named? 
 
CHAPTER IV 
 OXYGEN 
 
 28. Preparation. Oxygen may be prepared from water 
 by electrolysis, as described in the last chapter, but it is 
 more commonly prepared in the laboratory by heating some 
 substance which contains it. The material generally used 
 
 
 FIG. 50. Preparing oxygen from potassium chlorate and manganese dioxide. 
 
 is the white salt known as potassium chlorate (often called 
 chlorate of potash). This substance contains thiriy-nine 
 per cent of oxygen, which may be driven off at high tempera- 
 ture. For some unknown reason, however, the oxygen is 
 liberated at a much lower temperature if the potassium 
 chlorate is mixed with about one fourth its own weight of 
 the black substance known as manganese dioxide. The 
 manner of preparing oxygen is illustrated in Fig. 50. 
 
 52 
 
OXYGEN 
 
 53 
 
 FIG. 51. Copper 
 flask for making 
 oxygen. 
 
 The mixture of potassium chlorate and manganese dioxide 
 is placed in the flask A, which stands on a small sandbath. 
 When this is gently heated, the gas soon 
 begins to pass through the tube B and is 
 collected over water in the bottles C. The 
 gas is not collected until the air has all 
 been driven out of the apparatus. Be- 
 fore the burner is removed (at the end 
 of the experiment) the rubber tube B is 
 disconnected to prevent the water from 
 being drawn back into the flask as it cools. When large 
 quantities of oxygen are to be prepared, the copper flask, 
 shown in Fig. 51, is used instead of a glass flask, which is 
 easily broken. 
 
 29. Properties. Oxygen is a colorless, odorless, and 
 tasteless gas, which is 1.1 times heavier than air. Its most 
 interesting property is the way in which it supports combus- 
 tion. Materials which burn in the air burn much more 
 rapidly in oxygen. If a splint with a glowing coal on the 
 end is thrust into a bottle of oxygen, it .will 
 burst into flame and burn vigorously. Sul- 
 phur burns with a feeble flame in the air, 
 but in oxygen the flame is increased in size 
 and brightness. Phosphorus burns readily 
 in the air, but in oxygen it burns with a 
 dazzling brilliance. Some substances that 
 will not burn in the air will do so in pure 
 oxygen. Take a piece of picture frame wire, 
 heat the end in a Bunsen burner, and dip 
 into powdered sulphur. The sulphur will 
 adhere to the end of the wire, and if it is ignited in the 
 burner and then thrust into a jar of oxygen, the wire will 
 
 FIG. 52. Burn- 
 ing iron wire in 
 oxygen. 
 
54 INORGANIC CHEMISTRY 
 
 burn with brilliant scintillation (Fig. 52). Glowing balls of 
 molten matter drop from the wire to the bottom of the jar. 
 Hydrogen mixed with half its volume of oxygen explodes 
 when ignited much more violently than it does when mixed 
 with air. Experiments with mixtures of these two gases 
 
 H 
 
 v SECT/O/V ro SHOW co/vsr/evcr/OH 
 FIG. 53. Oxy-hydrogen blowpipe. 
 
 should be conducted with great caution. The flame made 
 by burning hydrogen in oxygen is, with one exception, the 
 hottest known. To make use of this flame a special oxy- 
 hydrogen burner is used which permits the gases to mix 
 only at the nozzle (Fig. 53). When this flame plays 
 against a piece of lime, it heats it to a white heat and forms 
 the so-called " limelight," sometimes used for stereopt icons. 
 
 30. Composition of Water. The decomposition of water 
 by electrolysis shows that both hydrogen and oxygen are 
 contained in water, but this experiment alone does not prove 
 that water is composed solely of hydrogen and oxygen. If 
 these two substances can be combined to form water, the 
 proof that water is composed only of these two substances 
 will be conclusive. This has frequently been done by means 
 of the apparatus shown in Fig. 54. 
 
 A is a graduated tube, known as a eudiometer, which has 
 two platinum wires fused into the closed end, the ends of 
 the wires being about 2 mm. apart. This tube is filled with 
 mercury and inverted in a cylinder B full of mercury. Hy- 
 drogen gas is then introduced into the tube A, and the vol- 
 
OXYGEN 55 
 
 ume is carefully determined by raising or lowering the eu- 
 diometer until the mercury is at the same level inside and 
 outside of the tube. It is an easy matter to determine the 
 volume since it may be read on the scale. Oxygen gas is then 
 introduced and measured in the same way. 
 Nothing occurs to the mixture of gases if 
 allowed to stand at ordinary temperatures; 
 but if an electric spark is caused to pass be- 
 tween the two platinum wires, the gases will 
 unite with a slight explosion. If the gases 
 are mixed in the proportion of exactly two 
 volumes' of hydrogen to one of oxygen, they will 
 disappear entirely, and nothing will be left 
 but a minute quantity of water. That the 
 quantity of water is so small is due to the 
 fact that the combined volumes of the hydro- ' 
 gen and oxygen required to produce water is 
 over 2500 times the volume of the resulting FIG. 54. Eudi- 
 water. For example, if one cubic centimeter 
 of water were decomposed into hydrogen and oxygen, the 
 combined gases would have a volume of over 2500 cubic 
 centimeters. 
 
 31. Proportion of Hydrogen and Oxygen in Water. If 
 the hydrogen in the eudiometer is more than twice the 
 volume of the oxygen, an excess* of hydrogen will remain 
 after the explosion. On the other hand if the oxygen is 
 more than half the volume of the hydrogen, an excess of 
 oxygen will remain uncombined. Repeated experiments 
 of this kind have demonstrated that water is composed of 
 hydrogen and oxygen, and that these gases always combine 
 in the ratio of one volume of oxygen to two of hydrogen. 
 As the weight of a given volume of oxygen is sixteen times 
 
56 INORGANIC CHEMISTRY 
 
 that of the same volume of hydrogen, it follows that water 
 is composed of one part by weight of hydrogen to eight parts 
 by weight of oxygen. 
 
 32. Analysis and Synthesis. Two different methods 
 have been suggested for determining the composition of 
 water. In the last chapter the method described was the 
 decomposition of water by means of the electric current. 
 A process in which a substance is separated into its component 
 parts is termed analysis. The decomposition of water by 
 means of heated zinc resulting in the formation of hydrogen 
 is also a method of analysis. Such a process as the formation 
 of water in the eudiometer, in which a substance is formed 
 by bringing about the combination of its component parts, 
 is termed synthesis. 
 
 33. Elements and Compounds. It has been shown that 
 water, which appears to be a simple substance, is in reality 
 composed of two substances hydrogen and oxygen. It 
 is natural to think that if water can be decomposed into two 
 substances it might be possible to decompose hydrogen and 
 oxygen. All attempts to get anything else out of these sub- 
 stances, however, have failed. In other words, hydrogen 
 and oxygen are such simple substances that so far as is now 
 known they cannot possibly be divided any further. Such 
 substances which cannot be split up into anything simpler 
 are called elements. 
 
 Water, which is a union of hydrogen and oxygen, is a 
 representative of that class of substances which are composed 
 of two or more elements united. Substances that are com- 
 posed of two or more elements are called compounds. Water, 
 therefore, is a compound. 
 
 The study of chemistry has shown that the number of 
 elements is quite small, only about eighty in fact. Of the 
 
OXYGEN 57 
 
 known elements, not more than twenty are of everyday im- 
 portance. These, only, will be studied in this text. A 
 complete list of the elements is given on the inside of the 
 back cover. 
 
 Although the number of elements is small, many thou- 
 sands of compounds are known, and the list is being con- 
 tinually increased. Water, sugar, salt, alcohol, ammonia, 
 and starch are familiar compounds. Oxygen, iron, lead, 
 sulphur, and carbon are well-known elements. 
 
 34. Definite Proportions. It has been shown (31) 
 that water is composed of eight parts by weight of oxygen 
 to one part by weight of hydrogen. This proportion never 
 varies no matter whether the water be obtained by melting 
 pure ice, by condensing steam, or by burning hydrogen. 
 Careful analysis of many chemical compounds has demon- 
 strated that this is a general rule, and that a chemical com- 
 pound always contains the same elements, and that these 
 elements are always present in exactly the same proportions 
 by weight. This fact is known as the law of definite propor- 
 tions. 
 
 35. Physical and Chemical Changes. Two different 
 kinds of changes in water have also been observed. Ice 
 can be changed to water and water to steam ; and the pro- 
 cess may be reversed. But whether it exists as a solid, 
 liquid, or vapor, it is still water. Such a change, which 
 merely affects the form and does not affect the composition 
 of the substance, is known as a physical change. When 
 water is decomposed into hydrogen and oxygen, or when 
 these two gases are united by the heat of the electric spark, 
 the change which takes place is quite different ; for in either 
 case the products of the change are entirely different from 
 the substance or substances undergoing the change. Such 
 
58 
 
 INORGANIC CHEMISTRY 
 
 a change as this, which affects the composition of the sub- 
 stance, is called a chemical change. 
 
 Two other terms may be explained here ; namely, mechani- 
 cal mixture and chemical compound. In a mechanical mix- 
 ture the substances do not undergo a chemical change, 
 but each retains all of its individual characteristics. The 
 mere mixing of the gases hydrogen and oxygen in the eudi- 
 ometer is a good example. In the case of a chemical com- 
 pound two or more elements have undergone a chemical 
 change, and have united and thus lost their original char- 
 acteristics. Water, which is formed by the chemical union 
 of hydrogen and oxygen, is a good example of a chemical 
 compound. 
 
 Physical changes and mechanical mixtures may be said to 
 be in the realm of physics, while the chemical changes are in 
 the field of chemistry. 
 
 EXERCISES 
 
 Ex. 30. Arrange apparatus as shown in Fig. 55. 
 A is a hard glass test tube, B a piece of glass tubing 
 bent at a right angle, C a piece of rubber tubing. Make 
 a mixture of 5 grams of potassium 
 chlorate and half its bulk of manganese 
 dioxide by rubbing the two together 
 in a mortar. (As manganese dioxide 
 sometimes contains impurities, the 
 mixture should be tested before using 
 
 FIG. 55, A simple apparatus for generating oxygen. 
 
OXYGEN 50 
 
 by heating about one gram in a test tube. If the oxygen comes off 
 quietly, proceed with the experiment.) Place the mixture in the test 
 tube and heat gradually, beginning at the top. A steady flow of gas 
 may be obtained by regulating the amount of heat applied. Collect 
 four 8-ounce bottles of the gas in the usual way. At the end of the 
 experiment withdraw the tubing from the water, or remove the cork 
 from the test tube. What is the appearance of the gas ? (The cloudi- 
 ness which sometimes shows at the beginning of the experiment will 
 soon disappear.) 
 
 Ex. 31. (a) Slip a glass plate over the mouth of one of the bottles 
 and turn it mouth upward. Thrust a splint with a glowing coal on 
 the end into the bottle repeatedly. 
 
 (6) Warm a glass rod so that a piece of sulphur (the size of a grain 
 of wheat) will adhere to it. Ignite the sulphur and note how it burns. 
 Thrust it into a bottle of oxygen and note whether it burns differently. 
 
 (c) Take a piece of picture frame wire 8 inches long and spread one 
 end slightly. Heat this end of the wire and dip it into powdered sulphur. 
 Ignite the sulphur which adheres to the wire and thrust it into a bottle 
 of oxygen. What happens to the glowing coal? Does the oxygen 
 ignite as hydrogen did? What difference do you 
 note in the sulphur burning in air and oxygen? Is 
 the odor the same in each case ? Do substances that 
 burn in air burn more or less vigorously in oxygen? 
 What happens in the case of the iron wire? Will 
 the wire burn in the air? What can you say in gen- 
 eral about burning in oxygen as compared with burn- 
 ing in air? 
 
 Ex. 32. (By the Teacher.) Hollow the end of 
 a piece of crayon into a small cup and attach a piece 
 of wire as shown in Fig. 56. Place a piece of phos- 
 phorus the size of a grain of wheat in the cup and 
 ignite by touching it with a hot wire. Lower it into 
 a bottle of oxygen and note results. (Phosphorus burning phos- 
 must be handled with extreme care. It is always p 
 kept covered with water and should always be cut under water. Never 
 touch phosphorus with the hands, but handle with forceps.) How 
 does the burning in air compare with burning in oxygen? What is 
 the source of the white fumes ? Do the white fumes dissolve in water ? 
 
60 INORGANIC CHEMISTRY 
 
 Ex. 33. (By the Teacher.) Fill a half pint cream bottle one third 
 full of oxygen and two thirds full of hydrogen. Wrap the bottle in a 
 thick towel and holding at arm's length quickly bring it mouth down- 
 ward over a flame. How does the explosion compare with that of 
 hydrogen and air ? What is meant by the oxy-hydrogen flame ? How 
 does it compare with other flames for heat? Draw a diagram of an 
 oxy-hydrogen burner. How is the limelight obtained ? 
 
 Ex. 34. What is analysis ? Synthesis ? What is an element ? A 
 compound? Give examples of each. How does the number of ele- 
 ments compare with the number of compounds? What is a physical 
 change? A chemical change? A mechanical mixture? A chemical 
 compound ? With what kind of changes is chemistry concerned ? 
 
CHAPTER V 
 OXYGEN (Continued} 
 
 36. Oxides and Oxidation. The experiments with oxy- 
 gen described in the last chapter show that at ordinary 
 temperatures oxygen has little effect upon substances placed 
 in it, but that at higher temperatures it makes them burn 
 more actively than they will in the air. Oxygen is said, 
 therefore, to be rather inactive at low temperatures, but 
 very active at high temperatures. What really happens, 
 when the substances burn in oxygen, is that the oxygen 
 combines with the burning materials. Oxygen unites with 
 sulphur and forms a suffocating gas; with phosphorus 
 it forms white fumes; and with iron it forms the black 
 molten material which drops to the bottom of the bottle. 
 
 When oxygen unites with another element, the result is a 
 compound called an oxide. Thus iron and oxygen form iron 
 oxide; phosphorus and oxygen form phosphorus oxide. 
 Some of the oxides are colorless gases like the oxides of sul- 
 phur and carbon, but the majority of them are solids, such 
 as the oxides of iron, phosphorus, and lead. When oxygen 
 unites with another element, the process is called oxidation, 
 and the resulting compounds formed are known as products 
 of oxidation. Water is the product of the oxidation of hydro- 
 gen, and is in reality hydrogen oxide. 
 
 37. Burning in Air due to Oxygen. The strong resem- 
 blance between the burning of substances in oxygen and in 
 
 61 
 
62 
 
 INORGANIC CHEMISTRY 
 
 the air suggests that these two processes are the same. More- 
 over, carefully conducted experiments show that whether 
 the substance is burned in oxygen or in the air the products 
 formed are exactly the same. It is certain, therefore, that 
 the process of burning in the air is due to the presence of 
 oxygen. The fact that substances burn less readily in air 
 than in oxygen further suggests that the air is not pure oxy- 
 gen. The proportion of oxy- 
 gen in the air can be shown 
 by a simple experiment (Fig. 
 57). 
 
 A small piece of cork or of 
 wood A is floated in the water 
 in the pan B. A piece of 
 phosphorus the size of a pea 
 is placed on the cork. The 
 phosphorus is ignited by a 
 touch from a piece of hot 
 iron wire, and a wide-mouth bottle C is carefully placed 
 over it. The phosphorus will burn until the oxygen in the 
 air within the jar is exhausted, and then it will be extin- 
 guished. The water rises in the bottle to take the place 
 of the oxygen consumed. The white cloud of oxide of 
 phosphorus will soon be dissolved in the water, and if the 
 bottle is so adjusted that the level of the water inside and 
 outside is the same, it will be found that the jar is about 
 one fifth full of water. The air, therefore, is about one fifth 
 oxygen and four fifths of some other gas which does not unite 
 with the phosphorus. 
 
 38. Combustion Defined. Combustion, in its ordinary 
 sense, whether in oxygen or in the air, consists in the union 
 of substances with oxygen with the evolution of light and 
 
 FIG. 57. Experiment to show propor- 
 tion of oxygen in the air. 
 
OXYGEN 
 
 63 
 
 heat. 1 Substances which will unite with oxygen are said to 
 be combustible and those which will not are incombustible. 
 All the important elements will unite with oxygen. 
 
 39. Kindling Temperature. It has been shown that 
 substances do not usually combine with oxygen at ordinary 
 temperatures. This is a fortunate thing ; for if it were not 
 so, all combustible substances in nature would burn up, 
 since there is sufficient oxygen in the air for that purpose. 
 Some substances need to be heated very little before they 
 will burn, while others ignite only when raised to very high 
 temperatures. If small pieces of phosphorus, sulphur, 
 and charcoal are placed on an iron plate with a lighted burner 
 beneath, the phosphorus soon bursts into a flame. The 
 sulphur, however, requires considerable heat to ignite it, 
 and the charcoal does not burn until it reaches red heat. 
 Similar experiments with 
 a variety of substances 
 demonstrate that each 
 has a certain tempera- 
 ture to which it must be 
 heated before it will ig- 
 nite. This is known as 
 the kindling temperature 
 of the substance. When 
 the material begins to 
 burn, the heat of the 
 burning parts raises the 
 
 temperature of the adjacent parts to the kindling tempera- 
 ture and the burning spreads. The way the flame creeps 
 
 1 Chemists sometimes define combustion as "any rapid chemical action 
 accompanied by light and heat." There is a limited number of such chemi- 
 cal actions in which oxygen takes no part. 
 
 FIG. 58. The difference in the kindling 
 temperature of paper, wood, and coal is utilized 
 in building a coal fire. 
 
64 INORGANIC CHEMISTRY 
 
 along a stick of wood is an example in point. Practical 
 advantage is taken of the difference in kindling tempera- 
 tures in lighting a coal fire, by the fact that paper is first 
 placed on the grate bars, then pine kindling is placed on the 
 paper, and then the coal above (Fig. 58). The paper is 
 easily ignited, but since it alone cannot raise the coal to 
 its kindling temperature, the pine is placed between. 
 
 40. Slow Oxidation. Some substances unite slowly with 
 oxygen at ordinary temperatures without the evolution 
 of light. Iron is such a substance. When iron rusts, as 
 it does when exposed to moisture, the change consists in 
 the union of the iron with oxygen, and the rust is similar 
 to the substance formed when iron is burned in oxygen. If 
 some moist iron dust or filings are placed on the floating 
 cork shown in Fig. 57, and the apparatus allowed to stand 
 for one or two weeks, the water will be seen to rise slowly 
 in the bell jar. If allowed to stand long enough, it will be 
 found that, as in the case of the burning phosphorus, one 
 fifth of the volume of the bottle is filled with water. A 
 change of this kind is known as slow oxidation. Slow oxida- 
 tion is of common occurrence. It is always taking place 
 in the animal body. The oxygen taken into the lungs acts 
 upon various substances in the body, oxidizing them into 
 other forms which can be more readily eliminated, as, for 
 example, water and an oxide of carbon. The decaying of 
 wood and other vegetable and animal matter is a slow oxida- 
 tion process brought about by the action of bacteria. 
 
 What difference is there between combustion and slow 
 oxidation ? Apparently in the case of the latter there is no 
 light or heat produced. A careful study of the subject 
 has shown, however, that a given amount of iron produces 
 exactly the same amount of heat whether burned in oxygen or 
 
OXYGEN 
 
 65 
 
 allowed to rust in the air. In the one case the heat is all 
 given off in a short time and the temperature becomes so 
 high that light is emitted. In the other case the heat is 
 evolved slowly, and the surrounding air conducts it away 
 as rapidly as it is produced. The quantity of heat is the same 
 in both cases. 
 
 41. Weight Relations of Combustion. If the burning 
 of a substance consists in its union with oxygen, it follows 
 that the products of combustion must weigh more than the 
 substance burned. The oxide resulting from the burning 
 of the iron wire weighs more than the wire itself. The oxide 
 produced when copper was heated in oxygen is heavier than 
 the copper burned. In the case of burning wood, or a lighted 
 candle, there is apparently a loss of matter, for the wood and 
 candle almost completely disappear. The wood and the 
 candle are composed 
 largely of carbon and 
 hydrogen. When the 
 latter burns, it forms 
 the oxide of hydrogen 
 called water and dis- 
 appears into the air 
 as vapor; but it has 
 been shown that the 
 water produced 
 weighs nine times as 
 much as the hydrogen 
 burned (31). The 
 
 carbon burns to an oxide which is a colorless gas, and it also 
 disappears into the atmosphere. This gas weighs nearly 
 four times as much as the carbon burned. Figure 59 shows 
 a method of demonstrating that the products of combus- 
 
 EV. CHEM. 5 
 
 FIG. 59. Experiment to show the weight relations 
 of combustion. 
 
66 INORGANIC CHEMISTRY 
 
 tion of a candle weigh more than the candle itself. Two 
 lamp chimneys are suspended on each side of a balance over 
 unlighted candles. The upper parts of the chimneys are 
 filled with caustic soda (sodium hydroxide), which has the 
 power of absorbing water and the oxide of carbon. The 
 pans are exactly balanced by placing sand or small weights 
 on the lighter side. One of the candles is then lighted, and 
 as it burns away and the products of combustion are ab- 
 sorbed by the caustic soda in the chimney above the burnt 
 candle, that side of the balance slowly sinks, showing that 
 it has increased in weight. 
 
 This experiment shows that the elements in the candle were 
 not actually destroyed, but merely changed into other com- 
 pounds by uniting with oxygen. In fact, scientists believe 
 that matter cannot be destroyed, and that after every 
 physical or chemical change the amount of matter is 
 the same as before. This is merely the equivalent of 
 saying that it is not possible either to create or destroy 
 matter. This is known as the law of the indestructibility 
 of matter, sometimes known as the law of the conservation 
 of matter. 
 
 42. Spontaneous Combustion. While slow oxidation usu- 
 ally takes place in such a way that there is no perceptible 
 rise of temperature, it is possible for the oxidizing substance 
 to be so placed that the heat cannot radiate as fast as formed. 
 In that case the heat may accumulate until it -has warmed 
 the material to its kindling temperature, upon reaching which 
 it will burn. This is probably the cause of the so-called 
 spontaneous combustion. Some oils, notably linseed oil, 
 oxidize readily, and oily rags have often been discovered 
 to be on fire. Barns have been burned by the spontaneous 
 combustion of hay, and fires that are to be accounted for 
 
OXYGEN 
 
 67 
 
 only by spontaneous combustion have been found in the 
 center of large heaps of coal. 
 
 43. Reduction the Opposite of Oxidation. It has been 
 said that the union of oxygen with other elements is called 
 oxidation; but when hydrogen is passed over copper oxide 
 the opposite effect is produced, namely, the oxygen is taken 
 away from the copper. The process, which is the reverse 
 of oxidation, is known as reduction. Anything which, like 
 hydrogen, causes another substance to lose oxygen is called 
 a reducing agent. In this experiment it will be noticed that 
 the. hydrogen is oxidized but the copper oxide is reduced. 
 
 44. Occurrence of Oxygen. Oxygen is the most abun- 
 dant and most widely distributed of all the elements. It 
 comprises four fifths of the water, one fifth of the air, and 
 one half of the rocks of the earth. It is 
 
 found in all plant and animal bodies, and 
 it is absolutely essential to all life of both 
 the animal and vegetable kingdom. It dis- 
 solves to the extent of three per cent in 
 water, making possible the life of fishes. It 
 is used commercially in a number of ways, 
 and it is useful in the treatment of certain 
 diseases. For commercial purposes it is sold 
 in a compressed form in strong steel cylin- 
 ders (Fig. 60). It is prepared from po- 
 tassium chlorate, or from liquid air in the 
 manner to be described in the next chapter. 
 
 45. Hydrogen Peroxide. Water, as has 
 been shown, consists of one part by weight 
 
 of hydrogen to eight of oxygen. Another compound of 
 hydrogen and oxygen is known which contains twice as much 
 oxygen as water, that is, 16 parts by weight of oxygen 
 
 FlG. 60. A cyl- 
 inder of commercial 
 oxygen. 
 
68 INORGANIC CHEMISTRY 
 
 to one of hydrogen. This substance is known as hydrogen 
 peroxide. It is an unstable compound and readily gives up 
 half of its oxygen and changes to water. Thus it is a good 
 oxidizing agent. Its use in medicine and in bleaching de- 
 pends upon this property. It is never used in the pure 
 state. The solution found on the market contains about 
 three per cent of actual hydrogen peroxide dissolved in 
 water. 
 
 EXERCISES 
 
 Ex. 35. Is oxygen very active at low temperatures? At high 
 temperatures ? What takes place when substances burn in oxygen ? 
 When oxygen unites with another element, what is the product called ? 
 Name the product of the combustion of oxygen with iron ; with phos- 
 phorus ; with carbon. What is meant by oxidation ? What is meant 
 by " products of oxidation " ? What is formed when hydrogen is 
 oxidized ? 
 
 Ex. 36. (By the Teacher.) Perform the experiment described in 
 paragraph 37. 1 What causes the water to rise in the bottle? What 
 proportion of the air is oxygen? Compare the burning in air with 
 burning in oxygen. Are the products of combustion the same in 
 each case? In which does the burning take place more vigorously? 
 What is meant by combustion as the term is ordinarily used? What 
 is meant by combustible and incombustible substances? 
 
 Ex. 37. Perform the experiment described in paragraph 39. What 
 happened to the phosphorus, sulphur, and charcoal ? Which ignited 
 at the lowest temperature? What is meant by kindling tempera- 
 ture? Do substances usually burn at ordinary temperatures? Why 
 is this a fortunate thing? Is there much difference in the kindling 
 temperatures of substances? Is the kindling temperature constant 
 for each substance? What practical use of the difference in kindling 
 temperatures of substances is made in the home? Light the end of 
 a long splinter of wood. What makes the flame spread along the 
 
 1 Allow the bottle to remain standing mouth downward in the water for 
 use in a later experiment. 
 
OXYGEN 
 
 69 
 
 wood ? Why does the wood burn more rapidly if held with the burn- 
 ing end downward than if the burning end is at the top ? 
 
 Ex. 38. Examine a piece of rusty iron from your home. Of what 
 is the rust composed ? How does it compare with the product formed 
 when iron burns in oxygen ? What is meant by slow oxidation ? Is it 
 of common occurrence? Mention a few instances of slow oxidation. 
 What is the source of the heat in animal bodies? Is heat produced 
 during slow oxidation ? How does the quantity of heat compare with 
 that produced by rapid combustion of the same substance ? 
 
 Ex. 39. Perform the experiment described in paragraph 41. What 
 becomes of the candle when it burns ? Do the products of combustion 
 weigh more or less than the substance burned? When wood or coal 
 is burned in the stove, only a small amount of ash is left; what be- 
 comes of the remainder of the fuel ? Is any of the matter destroyed ? 
 What is the law of the indestructibility of matter? Iron rust weighs 
 more than the iron from which it was made; has matter been created? 
 How is spontaneous combustion explained? Why is it dangerous to 
 allow oily rags to lie around ? Do you know of any cases of spontaneous 
 combustion in your vicinity? 
 
 Ex. 40. Arrange apparatus as shown in Fig. 61. A is an ordinary 
 hydrogen generator. B is a piece of glass tubing with the horizontal 
 arm about 8 inches long. C is 
 a hard glass test tube with some 
 fine copper oxide at the closed 
 end. Allow hydrogen to pass 
 through the tube for a few 
 minutes and then continuously 
 heat the copper oxide and note 
 the result. Does the copper 
 oxide change color? Why? 
 What becomes of the oxygen 
 which is removed from the cop- 
 per oxide? What is meant by reduction? Is hydrogen a reducing 
 agent ? Is the copper oxide a reducing agent or an oxidizing agent ? 
 
 Ex. 41. Tell what you can about the occurrence of oxygen, (a) in 
 the elemental form, (&) in combination with other substances. How 
 is it prepared commercially ? What is hydrogen peroxide ? For what 
 is it used? 
 
 FIG. 61. Reducing copper oxide with 
 hydrogen. 
 
CHAPTER VI 
 
 AIR NITROGEN 
 
 46. IT will be well to return to the experiment in which 
 phosphorus was burned in the wide-mouth bottle (Fig. 57). 
 The bottle is now so adjusted that the level of the water 
 inside and outside is the same, a glass plate 
 is slipped under the mouth, and the bottle 
 turned mouth upward. If, now, a lighted 
 candle is placed in the bottle (Fig. 62), it 
 will not burn as it does in air or oxygen, but 
 will be immediately extinguished. Nor will 
 the gas itself burn as does hydrogen. Here 
 is a new gas, then, which neither burns nor 
 supports combustion. This gas was first 
 studied by the English chemist Rutherford 
 in 1772. It was later named nitrogen be- 
 cause of its presence in niter or saltpeter. 
 
 47. Properties. Nitrogen is a colorless, 
 odorless, and tasteless gas. It is lighter than 
 
 FIG. 62. A 
 
 candle is extin- oxygen or air and constitute3 nearly four 
 
 fifths of the atmosphere. It is less soluble 
 in water than is oxygen. Chemically it is 
 said to be very inactive, for it will not readily unite with any 
 other element, even at rather high temperatures. It is evi- 
 dent that it does not unite with oxygen at ordinary tem- 
 peratures. The electric spark will cause a limited union 
 of nitrogen and oxygen, and this combination is supposed 
 
 70 
 
AIR NITR OGEN 71 
 
 to take place to a slight extent during electric storms. It 
 may be said, therefore, that most of its properties are of a 
 negative character, and that nitrogen is most noted in the 
 laboratory for what it will not do. Animals placed in nitro- 
 gen die immediately of suffocation, not because the gas is 
 poisonous, but because they cannot live without oxygen. 
 
 48. Occurrence. Nitrogen exists as an element in the 
 atmosphere. United with other elements into very com- 
 plex compounds, it is found in plant and animal tissues. 
 It is sometimes said to be the most important element to 
 life, as it is necessary to the formation of the protoplasm of 
 the cell upon which life depends. While the worker in the 
 laboratory finds difficulty in making nitrogen combine with 
 other elements, nature has a way of bringing about this 
 union. Certain bacteria found in the soil have the power 
 of combining nitrogen with hydrogen and oxygen in such a 
 way that crops can use it. Some of these bacteria grow in 
 little nodules, or tubercles, on the roots of plants like the 
 clovers, peas, beans, and other leguminous plants. Others 
 of these bacteria do not grow on the roots of plants but live 
 free in the soil. Animals eat the crops and get their neces- 
 sary nitrogen compounds in that way, so that these tiny 
 bacteria are responsible for most of the combined nitrogen 
 found in nature. More will be said about these bacteria 
 later (168). 
 
 49. Air a Mechanical Mixture. The ratio between 
 nitrogen and oxygen in the air is so nearly constant that 
 the question might arise whether it is a compound or a 
 mechanical mixture of these two elements. All experiments 
 indicate that the air is merely a mechanical mixture consist- 
 ing of practically 21 per cent oxygen, 78 per cent nitrogen, 
 and 1 per cent of small quantities of a number of other 
 
72 INORGANIC CHEMISTRY 
 
 gases. Two reasons for this belief may be mentioned. 
 First, true chemical compounds do not vary in the least in 
 composition. The variation in the composition of air, 
 though slight, is sufficient to show that it is not a compound. 
 Second, if air is dissolved in water and the air taken out of 
 the water by means of an air pump, it will be found that the 
 ratio of oxygen to nitrogen in this air is as 1 to 2, while in 
 the atmosphere it is as 1 to 4. The ratio of the elements in 
 a true chemical compound does not change when the sub- 
 stance is dissolved in water. 
 
 50. Air Contains Water Vapor. The experiment wherein 
 calcium chloride absorbed moisture from the air shows that 
 the atmosphere contains water vapor. This is also dem- 
 onstrated when moisture collects on a vessel containing 
 cold water. The surrounding air is cooled 
 to such an extent that some of its moisture 
 is deposited on the cold vessel in the form 
 of liquid water (Fig. 63). 
 
 The amount of moisture in the atmos- 
 phere is the most variable of all its con- 
 stituents and is known as humidity. The 
 power of the air to hold water vapor in- 
 FIG. 63. Moisture creases with rise of temperature. When 
 
 collects on the outside 
 
 of a vessel of cold air contains all the moisture it will hold, it 
 is said to be saturated. At 10 C. one cubic 
 meter of air will hold 9.7 grams of water vapor, while at 
 20 C. it takes 17.1 grams to saturate it. Relative humidity, 
 a term quite commonly used, is the ratio between the amount 
 of water vapor in the air at a given temperature and the 
 amount it could hold when saturated at that temperature. 
 A relative humidity of 80, for instance, means that the air 
 contains 80 per cent of the moisture it is possible for it to 
 
AIR NITROGEN 
 
 73 
 
 hold at that temperature. When the air is saturated, the 
 relative humidity is said to be 100. As air cools, its power 
 to hold moisture decreases, and finally the water vapor con- 
 denses as dew. The temperature at which this takes place 
 is known as the dew point. 
 
 51. Air Contains Carbon Dioxide. If a dish contain- 
 ing limewater is allowed to stand exposed to the air for a 
 short time, a crust of white material , 
 
 forms on the surface. This effect is not 
 produced by pure oxygen, by nitrogen, or 
 by water. If the mouth is placed near a 
 dish of limewater and the breath blown on 
 it, or if a lighted candle is lowered into a 
 wide-mouth bottle containing a little lime- 
 water (Fig. 64), the white crust forms very 
 rapidly. Evidently, then, the air contains 
 another gas which is probably identical 
 with some substance found in the breath, 
 and which is also formed when a candle 
 burns. This is a compound of oxygen and 
 carbon known as carbon dioxide, commonly called carbonic 
 acid gas. This gas will be more fully discussed in the 
 chapter on carbon compounds. 
 
 The amount of carbon dioxide in the air is very small, 
 amounting to only 0.03 per cent or 3 parts in 10,000 in the 
 country, and seldom exceeding 0.06 per cent in -the cities 
 where much coal is burned. Small as the quantity is, it is 
 very important ; for without it green plants could make no 
 growth. The amount in the air is practically constant; for 
 plants use it at about the same rate at which it is produced 
 by the breathing of animals, by the burning of wood and 
 coal, and by other oxidation processes (107). 
 
 FIG. 64. A burn- 
 ing candle lowered 
 into a bottle contain- 
 ing limewater. 
 
74 
 
 INORGANIC CHEMISTRY 
 
 52. Traces of Other Substances in Air. In addition to 
 the four substances mentioned, the atmosphere contains 
 small quantities of certain rare gases and traces of sulphur 
 compounds, as well as dust, bacteria, and various sub- 
 stances given off from the lungs. 
 
 53. Diffusion of Gases. Before leaving the subject of air 
 it will be well to learn something of those physical prop- 
 erties of gases to which occasional reference must be made. 
 
 Gases diffuse in all directions regardless of 
 their density. If two bottles (Fig. 65) are 
 placed mouth to mouth, the upper one con- 
 taining the light gas, hydrogen, and the 
 lower containing air, which is fourteen times 
 as heavy, diffusion begins immediately, and 
 after a few minutes there is hydrogen in the 
 lower bottle and air in the upper. If it were 
 not for this property of gases, the atmos- 
 phere would consist of a lower layer of the 
 heavy carbon dioxide, a middle layer of 
 oxygen, and an upper one of nitrogen, which 
 is the lightest of the three gases. Diffusion 
 keeps the gases uniformly mixed, but in the 
 atmosphere this process is accelerated by the 
 mixing action of the winds and other air currents. 
 
 54. Effect of Temperature and Pressure. Substances 1 
 expand when heated, but gases are affected to a much 
 greater extent than liquids or solids. That heated air 
 expands and is, therefore, lighter than cold air is shown 
 by the hot-air balloon so commonly seen at the country 
 fairs. Gases respond readily to change of pressure. The 
 volume of a gas is inversely proportional to the pressure to 
 
 1 Water below 4 C. is an exception. 
 
 FIG. 65. To 
 show the diffusion 
 of gases. 
 
AIR NITROGEN 
 
 75 
 
 which it is subjected. If the pressure is doubled, the volume 
 of the gas becomes one half, provided the temperature re- 
 mains unchanged. While different liquids and solids ex- 
 pand or contract at varying rates upon change of tempera- 
 ture or pressure, it is interesting to note that all gases behave 
 the same regardless of their composition. 
 
 55. Liquefaction. All gases can be condensed to liquids 
 and even to solids, provided the proper combination of 
 very low temperature and high pressure can be secured. 
 Oxygen cannot be condensed to a liquid unless its temper- 
 ature is lowered to 119 C., while nitrogen must be cooled 
 to - 146 C. and hydrogen to - 241 C. Air can be liquefied 
 in the same way, and when it changes back to the gaseous 
 form the nitrogen boils off first, leaving the oxygen behind. 
 Oxygen of 95 per cent purity is prepared commercially in 
 this way. This behavior of liquid air is 
 
 another proof that air is a mechanical mix- 
 ture. 
 
 56. Gases Are Substances. That gases 
 are matter and actually occupy space can be 
 shown by a simple experirrent. A bottle of 
 air or some other gas is fitted with a tight 
 cork carrying a funnel with a small opening, 
 as in Fig. 66. If the apparatus is air-tight, 
 water poured in the funnel will not run into 
 the bottle, a circumstance which shows that 
 the bottle is already full. If the cork is 
 loosened to allow the gas to escape, the water 
 will enter the bottle. 
 
 That gases have weight also may be shown by weighing 
 a flask from which the air has been exhausted by an air 
 pump, and then weighing the flask when filled with dif- 
 
 FiG.66. The 
 air in the bottle 
 prevents the water 
 in the funnel from 
 entering. 
 
76 INORGANIC CHEMISTRY 
 
 ferent gases. A liter (about one quart) of hydrogen weighs 
 0.09 gram, while a liter of oxygen weighs 1.43 grams. 
 
 EXERCISES 
 
 Ex. 42. Adjust the bottle left from Ex. 37 so that the level of the 
 water inside and outside of the bottle is the same. Slip a glass plate 
 over the mouth of the bottle and turn it mouth upward. Lower a 
 lighted candle into the bottle. Does the candle continue to burn? 
 Does the gas in the bottle ignite? Is the gas in the bottle different 
 from the two previously studied? What is the name of this gas? 
 Give the properties of nitrogen. Is nitrogen an element or a com- 
 pound? What can you tell about the occurrence of nitrogen? How 
 doe? nature cause nitrogen to combine with other elements ? How do 
 animals get their nitrogen compounds? Is air a chemical compound 
 or a mechanical mixture? Give reasons for your answer. 
 
 Ex. 43. Have you ever noticed moisture gather on the outside of 
 a vessel containing cold water? Where does this moisture come 
 from ? In what other way can you demonstrate the presence of water 
 vapor in the air? What is meant by the humidity of air? What is 
 the meaning of relative humidity? When is the relative humidity 
 said to be 100 ? If air was suddenly heated or cooled, would its relative 
 humidity be changed ? Explain. What is meant by the dew point ? 
 
 Ex. 44. Place limewater in a shallow dish and allow it to stand 
 exposed to the air. What happens to it? Blow the breath into a 
 bottle containing limewater. Lower a candle into a similar bottle. 
 What change takes place in the limewater? Does the air contain 
 something that is also found in the breath and in the products of com- 
 bustion of the candle ? What is this substance ? Is much of it present 
 in the air? At home try placing a dish of limewater outdoors and 
 another in the house (in cool weather when the windows are closed) 
 and note if there is any difference in the rate at which the white crust 
 appears in the two dishes. What other substances are found in the 
 air besides nitrogen, oxygen, water vapor, and carbon dioxide? 
 
 Ex. 45. Fill an eight-ounce bottle with hydrogen and carefully 
 place it mouth downward over another bottle filled with air as shown in 
 Fig. 65. After letting it stand some time slip a glass plate between the 
 
AIR NITROGEN 77 
 
 bottles and remove the upper one. Invert the lower bottle and quickly 
 apply a burning splint to the mouth. Have you any evidence that 
 some of the lighter hydrogen has passed downward into the lower 
 bottle ? What is meant by diffusion of gases ? What effect does this 
 property of gases have on the composition of the atmosphere ? Do air 
 currents assist? What effect does pressure have on gases? How 
 are gases affected by changes in temperature ? Would a hot-air furnace 
 heat the house as well if placed in the garret instead of in the basement ? 
 Why ? Should ice be placed in the bottom or in the top of a refriger- 
 ator ? Why ? What makes the hot-air balloon rise ? What conditions 
 are necessary to liquefy a gas ? When liquid air is boiled, which gas 
 boils off first ? Is any practical use made of this fact ? 
 
 Ex. 46. Fit a funnel with a small opening into a cork and place it 
 in a bottle as in Fig. 66. Pour water into the funnel. Why does the 
 water not run into the bottle ? What happens if you loosen the cork ? 
 
CHAPTER VII 
 SULPHUR 
 
 57. SULPHUR is a well-known article of commerce in the 
 form of roll sulphur, or brimstone, and as the yellow powder 
 called flowers of sulphur. It is an element, but unlike those 
 
 FIG. 67. A solid block of Louisiana sulphur. Molten sulphur is pumped 
 from wells into immense wooden bins, where it solidifies. It is then broken 
 by blasting and loaded on freight cars for shipment. 
 
 studied so far, is a solid and not a gas. It has been known 
 from the earliest times because it occurs abundantly in 
 nature in the elementary form. It is found in the neigh- 
 borhood of volcanoes, especially those of Sicily, which 
 
 78 
 
SULPHUR 79 
 
 country was formerly the chief source of the sulphur of 
 commerce. Recently large deposits of sulphur have been 
 discovered in a number of places in the United States. The 
 state of Louisiana (Fig. 67) is the chief producer at the 
 present time. 
 
 58. Preparation. Sulphur as found in nature is mixed 
 with earthy matter. If the ore is heated until the sulphur 
 melts, the sulphur may be drawn off in a liquid form, leav- 
 ing the stones and earth behind. The crude sulphur thus 
 obtained is purified by distillation. The sulphur is distilled 
 into large cooling chambers of brick. When the vapor 
 first enters the condensing chamber, it is suddenly cooled 
 and is deposited as the fine powder known as flowers of 
 sulphur. When the chamber becomes warmer, the vapor 
 condenses in the form of a liquid, which is drawn off from 
 the bottom of the chamber and is molded in wooden molds 
 into the form of roll sulphur. 
 
 59. Properties. Sulphur is a yellow, brittle substance. 
 It is insoluble in water, but will dissolve readily in the 
 liquid known as carbon bisulphide. It behaves very pe- 
 culiarly when heated. When the temperature reaches 
 114.5 C., the sulphur melts, forming a thin, straw-colored 
 liquid. As the heat increases, the mass becomes darker in 
 color, and at 200 to 250 C. it becomes so thick that the 
 vessel in which it is heated can be turned upside down and 
 the sulphur will not run out. Finally, it again becomes 
 liquid, and at 448.4 C. it boils and is converted into a 
 brownish yellow vapor. 
 
 60. Different Forms of Sulphur. If sulphur is dissolved 
 in carbon bisulphide and the clear liquid is poured off and 
 is allowed to evaporate slowly, crystals of sulphur (Fig. 68) 
 will be formed, which, when examined through a magnifying 
 
80 
 
 INORGANIC CHEMISTRY 
 
 FlG. 68. Rhombic or eight-sided sulphur crystals. 
 
 glass, are seen to be eight-sided. This is the form of sulphur 
 found in nature. If sulphur that has been gently heated to 
 
 the melting point is 
 allowed to cool until 
 it is about half so- 
 lidified, the solid part 
 remaining after the 
 liquid is poured off 
 is found to be in 
 the form of long 
 needlelike crystals 
 quite different from 
 those described 
 above (Fig. 69). 
 
 On the other hand, 
 
 if sulphur is heated to the boiling point, and the liquid is 
 poured in a thin stream into cold water (Fig. 70), it forms 
 a plastic mass, entirely different in appearance from either 
 of the other forms, and with no crystalline appearance. 
 This is known as 
 plastic, or amorphous, 
 sulphur. 
 
 Neither the needle- 
 like (prismatic) sul- 
 phur nor the plastic 
 sulphur is stable, 
 because each, upon 
 standing, gradually 
 changes over into FIQ 6Q _ prismatic or needlelike sulphur crystals 
 the eight-sided form. 
 
 The greater stability of this eight-sided sulphur explains 
 why it is the form found in nature. 
 
SULPHUR 81 
 
 Still another form of sulphur is known. This is found 
 sometimes in sulphur springs, but is generally obtained by 
 precipitating sulphur from some 
 of its compounds. It is almost 
 white in color and is known as 
 milk of sulphur or lac sulphur. 
 It is used in medicine. 
 
 It will thus be seen that sul- 
 phur can exist in several very 
 different forms. Each of these 
 forms, however, consists of sul- 
 phur and nothing else. These 
 are known as allotropic forms of FIG. 70. The formation of 
 
 rr,, p . amorphous sulphur. 
 
 sulphur. The property ot exist- 
 ing in different forms is known as allotropy from two Greek 
 words meaning simply " another form." 
 
 61. Sulphur Found in Compounds. In addition to its 
 occurrence in the elementary condition sulphur is found 
 in many compounds. It occurs in the water of sulphur 
 springs, in the air near volcanoes, and in many minerals. 
 It is found in many plant and animal tissues. It is used 
 as an insecticide and as a fungicide. It is an ingredient of 
 gunpowder and of fireworks, and is used in the manufacture 
 of hard and vulcanized rubber. Its most important use is 
 in the manufacture of sulphuric acid, one of the most im- 
 portant of chemical substances. 
 
 62. Sulphides. Sulphur somewhat resembles oxygen in 
 its chemical behavior, especially toward metals. Like 
 oxygen it unites slowly with some metals at ordinary tem- 
 peratures. Like oxygen, also, it readily combines with 
 most metals at high temperatures, as can be shown in the 
 following experiment. Four grams of flowers of sulphur 
 
 EV. CHEM. 6 
 
82 INORGANIC CHEMISTRY 
 
 and seven grams of fine iron filings are thoroughly mixed 
 by rubbing in a mortar. That this is only a mechanical 
 mixture may be shown by taking a portion of the mixture 
 and drawing the iron out with a magnet, or by dissolving 
 out the sulphur with carbon bisulphide. Another portion 
 of the mixture is placed in an old test tube and heated 
 over the Bunsen burner. As soon as the mass begins to 
 glow, it is removed from the flame. If, when it is cold, the 
 tube is broken and its contents are examined, it will be 
 found that the magnet does not attract the iron in the mass, 
 and that sulphur cannot be dissolved from it by carbon bi- 
 sulphide. The sulphur has combined chemically with the 
 iron, and an entirely new substance, known as iron sulphide, 
 has been formed. Copper, lead, and other metals will 
 combine with sulphur in the same way. The compound 
 formed by the union of sulphur with another element is called 
 a sulphide, just as that formed by the union of oxygen and 
 another element is called an oxide. Sulphides are abun- 
 dant in nature and many of them are valuable ores. Lead, 
 copper, mercury, and zinc are among the metals found in 
 nature as sulphides. The black substance which forms on a 
 silver spoon that has been allowed to remain in contact with 
 an egg is silver sulphide, the sulphur coming from the egg. 
 Nearly all sulphides are insoluble in water. 
 
 63. Sulphur Dioxide. In the study of oxygen it was 
 shown that sulphur burns, forming a suffocating gas. Even 
 the sulphides of the metals will burn if heated, both the 
 sulphur and the metal uniting with oxygen and yielding 
 the gaseous oxide of sulphur just mentioned, and the oxide 
 of the metal. Copper sulphide, for instance, when burned 
 becomes copper oxide, the sulphur which was combined 
 with the copper uniting with oxygen to form a gas. This 
 
SULPHUR 83 
 
 gas has been named sulphur dioxide for reasons to be ex- 
 plained shortly. 
 
 Sulphur dioxide is a colorless gas with a suffocating odor. 
 It is 2.21 times heavier than air. It can readily be con- 
 densed to a liquid. It will not burn nor support combustion. 
 In the presence of moisture it bleaches many organic dyes. 
 Flowers and moistened pieces of cloth colored with vegetable 
 dyes placed in a bottle in which sulphur is burned will lose 
 their color. Sulphur dioxide is used to bleach silk, wool, 
 straw, and some other fibers which would be injured by 
 some of the more powerful bleaching agents. It has been 
 largely used as an antiseptic and disinfectant, as it will kill 
 bacteria. A .common method of disin- 
 fecting after illness is to burn sulphur in 
 the closed room. The sulphur candle 
 (Fig. 71) in which the brimstone is 
 molded around a wick is a convenient 
 form to use for this purpose. As a disin- 
 fectant it is now largely replaced by for- 
 maldehyde, however, which does not FlG - 7l c ' a ^j^ sulphur 
 destroy the colors of the materials disin- 
 fected, nor injure the metal of the gas or electric fixtures, 
 and other hardware. Sulphur dioxide has also been used in 
 preserving fruits and other food products since it prevents 
 fermentation ; but the use of this substance in anything that is 
 to be eaten is objectionable. Sulphur dioxide is injurious to 
 plants, and it is not unusual to find trees and other vegeta- 
 tion completely destroyed in the vicinity of the smelting 
 works where the sulphide ores are being roasted to burn 
 off the sulphur. 
 
 64. Sulphur Trioxide. Sulphur dioxide has been found, 
 upon analysis, to contain equal parts by weight of sulphur 
 
84 
 
 INORGANIC CHEMISTRY 
 
 FIG. 72. Preparation of sulphur trioxide. 
 
 and oxygen. Under ordinary circumstances the sulphur 
 dioxide does not readily take on any more oxygen. If, 
 however, sulphur dioxide and oxygen are passed over finely 
 divided platinum which is highly heated, a new compound 
 of sulphur and oxygen will be formed which contains one part 
 of sulphur to one and one half parts of oxygen, or one half 
 
 imore oxygen than 
 A is found in sulphur 
 
 .^,,-Q Hm^SMS^ ^^ D i- i 
 
 s^= dioxide. This com- 
 pound is a colorless 
 liquid which solidi- 
 fies at about 15 C., 
 and has been named 
 sulphur trioxide. It 
 may be prepared 
 on a small scale by means of the apparatus shown in Fig. 72. 
 The finely divided platinum is prepared -by moistening 
 asbestos fiber with a solution of platinum chloride and 
 igniting it in a flame. The platinum-asbestos is placed in 
 the hard glass tubing at A. Air, to furnish oxygen, is 
 introduced at B, and sulphur dioxide at C. The tube and 
 asbestos are heated with a Bunsen burner, and the fumes 
 of sulphur trioxide will be seen escaping into the air at D. 
 It may be condensed to a liquid if conducted into a test 
 tube surrounded with a freezing mixture of ice and salt. 
 
 It is to be noted that the platinum itself apparently does 
 not take part in the chemical change, but in some unex- 
 plainable way causes the union of the oxygen and sulphur 
 dioxide to take place very readily. Substances like this, 
 which hasten what would otherwise be slow chemical changes, 
 are called catalytic agents or catalyzers, and the action is 
 called catalysis. A catalyzer, then, merely increases the 
 
SULPHUR 85 
 
 speed of the chemical change but does not alter its 
 products. 
 
 65. Sulphuric Acid. Sulphur trioxide unites very vig- 
 orously with water. When exposed to the air it fumes 
 strongly, and if thrown upon water it hisses like hot iron. 
 When sulphur trioxide unites with water, the product is 
 sulphuric acid, sometimes called oil of vitriol. At the 
 present time most of the sulphuric acid is manufactured by 
 a method in which sulphur trioxide is first prepared by a 
 process similar to the one described. Usually the sulphur 
 dioxide is obtained by burning pyrites, which is a sulphide 
 of iron. The sulphur dioxide and air are conducted into 
 towers in which the formation of sulphur trioxide is brought 
 about by means of platinum or some other catalyzer, and 
 the sulphur trioxide is then united with water to form sul- 
 phuric acid. This is known as the contact method of making 
 sulphuric acid. Another method will be mentioned in 
 Chapter X. 
 
 Sulphuric acid is probably the most important of all 
 manufactured chemicals. It is the most common reagent 
 of the chemical laboratory ; and is used in many industries, 
 especially in the manufacture of fertilizers, soda, aniline 
 dyes, and nitroglycerin, and in the refining of petroleum. 
 Over four million tons of sulphuric acid are produced 
 annually. 
 
 When sulphuric acid is pure it is a colorless, odorless, 
 oily liquid. It is almost twice as heavy as water, having a 
 specific gravity of 1.84. It unites with water with great 
 evolution of heat. For this reason great caution must be 
 observed in mixing sulphuric acid and water. The acid 
 should be poured slowly into the water with constant stir- 
 ring. The water should never be poured into the acid, for 
 
86 INORGANIC CHEMISTRY 
 
 the great amount of heat liberated is likely to cause an 
 explosion which will throw the acid out of the container. 
 Sulphuric acid exposed to the air absorbs water vapor until 
 it becomes quite dilute. It is, therefore, a good drying 
 agent and is often used to dry gases. It destroys plant 
 and animal tissue, for it abstracts hydrogen and oxygen from 
 them in proportions to form water, leaving behind a black 
 charred mass which is largely carbon. The painful burns 
 caused by sulphuric acid are due to this action. It is also 
 sometimes used as an oxidizing agent, for under certain con- 
 ditions it will give up part of its oxygen to another substance. 
 
 In very dilute solutions sulphuric acid has a sour taste. 
 If a piece of blue litmus paper, a paper colored with a veg- 
 etable dye called litmus, is placed in it, the paper will turn 
 red. The sour taste and the effect on litmus are properties 
 that are characteristic of a large group of chemical com- 
 pounds which are known as acids. 
 
 66. Sulphuric Acid Forms Salts. Sulphuric acid con- 
 tains sulphur, oxygen, and hydrogen, for it is produced by 
 the combination of sulphur trioxide with water. In Chapter 
 III, in the discussion of the preparation of hydrogen, it was 
 shown that the hydrogen could be liberated from sulphuric 
 acid. It will be well now to consider what became of the 
 other elements in the acid. 
 
 It was noticed that while hydrogen was being evolved 
 the zinc disappeared. If the liquid in the hydrogen generator 
 is now filtered to remove the black particles which are 
 due to impurities in the zinc, and is then slowly evaporated 
 in a porcelain dish placed in a sand bath, the residue is a 
 white solid which looks somewhat like common salt. If 
 this material is redissolved in a small quantity of hot water 
 and set aside for some time, clear crystals are formed. This 
 
SULPHUR 87 
 
 substance contains the zinc which disappeared and the 
 sulphur and oxygen which were in the sulphuric acid. It is- 
 a compound known as zinc sulphate. If iron is used instead 
 of zinc, the residue is the green material sold under the 
 name of copperas, which is in reality iron sulphate, and 
 consists of iron, sulphur, and oxygen. 
 
 What has really happened in these cases, then, is that the 
 zinc or iron has replaced the hydrogen which was in the sul- 
 phuric acid. A compound formed by replacing the hydrogen 
 of sulphuric acid with a metal is called a sulphate. Some of 
 the sulphates like zinc sulphate and iron sulphate can be 
 made by the action of the acid on the metal, but other metals 
 are not readily acted upon by sulphuric acid. The sul- 
 phates of nearly all metals, however, can be made by in- 
 direct methods ; namely, by the action of sulphuric acid on 
 the oxide of the metal. This property of sulphuric acid by 
 which its hydrogen can be replaced by a metal is a property 
 that is common to all acids. Many of the compounds so 
 formed resemble common salt in appearance, and for that 
 reason, it has become customary to call all such compounds 
 salts. Copperas, blue vitriol, washing soda, Epsom salts, 
 alum, and table salt are all common substances which the 
 chemist places in the large class of compounds known as 
 salts. They are all formed by replacing the hydrogen of some 
 acid with a metal. 
 
 67. Multiple Proportions. It has been shown that sul- 
 phur forms two distinct compounds with oxygen. Each 
 of these compounds is constant in composition in accord 
 with the law of definite proportions (34). Hydrogen and 
 oxygen likewise form two distinct compounds, water and 
 hydrogen peroxide. In the latter one part of hydrogen is 
 combined with sixteen parts of oxygen, while in water one 
 
88 INORGANIC CHEMISTRY 
 
 part of hydrogen is combined with eight parts of oxygen. 
 The ratio between the amounts of oxygen in these compounds 
 when stated in its simplest form is as 1 to 2. 
 
 In sulphur dioxide one part of sulphur is united to one 
 part of oxygen, while sulphur trioxide is composed of one part 
 of sulphur to one and one half parts of oxygen. The ratio 
 of the oxygen jn these compounds when expressed in the 
 simplest terms is as 2 to 3. 
 
 A study of all the cases where two elements unite in more 
 than one proportion has shown that similar simple ratios 
 always exist between the different amounts of one of the 
 elements which unite with a fixed amount of the other ; that 
 is, the ratio can always be expressed by small whole numbers 
 such as 1, 2, 3, 4, or 5. This fact is known as the law of 
 multiple proportions. 
 
 EXERCISES 
 
 Ex. 47. Examine a piece of roll sulphur and state its most obvious 
 physical properties. Will it dissolve in water ? In carbon bisulphide ? 
 Heat the sulphur in a test tube. What happens upon heating? Is 
 sulphur an element or a compound? How does it occur in nature? 
 How is native sulphur purified ? 
 
 Ex. 48. Dissolve one half gram of sulphur in 2 cubic centimeters 
 of carbon bisulphide. Pour the liquid into a small dish and allow the 
 carbon bisulphide to evaporate. Describe the crystals of sulphur which 
 form. 
 
 Ex. 49. Fold a piece of filter paper as if to be placed in a funnel. 
 Heat about half a test tube of sulphur until it just melts and, holding 
 the filter by the three folds, pour the melted sulphur into it. When 
 the crystals begin to form across the surface pour off the remaining 
 liquid. What is the form of the crystal in this case? Allow the 
 crystals to remain undisturbed for a few days and examine again. 
 Has any change taken place? 
 
 Ex. 50. Heat another portion of sulphur to the boiling point and 
 
SULPHUR 89 
 
 pour in a thin stream into cold water, moving the test tube so as to 
 form a coil rather than a solid mass. Describe the result. Is this 
 sulphur crystalline? Define amorphous. Preserve the sample and 
 note what change takes place in a day or two. Is this form of sulphur 
 stable? What is the stable form of sulphur? What is meant by 
 allotropic forms of sulphur? What is the property of an element by 
 which it can exist in different forms ? 
 
 Ex. 51. Rub together four grams of powdered sulphur and seven 
 grams of fine iron filings. Pass a magnet over a small portion of the 
 mixture. Treat another small portion with carbon bisulphide, pour 
 off the liquid, and evaporate. Have you a compound of iron and 
 sulphur or a mechanical mixture? Place another portion in an old 
 test tube and heat over the Bunsen burner. What happens ? When 
 cold, break the tube and test the contents with the magnet and with 
 carbon bisulphide. What results do you get ? Has a chemical change 
 taken place? What is the new compound called? Are compounds 
 of sulphur of frequent occurrence? Name some substances contain- 
 ing sulphur. How does sulphur resemble oxygen in chemical be- 
 havior ? What are the compounds of sulphur with the metals called ? 
 What makes the silver spoon turn black when used with eggs ? Why 
 does a silver coin become black when kept in the pocket with a rubber 
 band ? Silver jewelry sometimes turns black ; where does the sulphur 
 come from ? 
 
 Ex. 52. Burn a small quantity of sulphur in a bottle of air (or 
 oxygen if at hand). Smell the gas cautiously. What is this gas 
 called and of what is it composed? Heat a piece of iron sulphide, 
 lead sulphide, or copper sulphide in the Bunsen flame. What odor 
 do you note ? What is the source of the sulphur ? Give the physical 
 properties of sulphur dioxide. Place some flowers and some pieces 
 of moist colored cloth in the bottle of sulphur dioxide. What happens ? 
 What use is made of this property of sulphur dioxide ? How is sulphur 
 dioxide used as a disinfectant? Should sulphur dioxide be used to 
 preserve fruits and vegetables? What effect does sulphur dioxide 
 have upon vegetation ? 
 
 Ex. 53. (By the Teacher.) Perform the experiment described in 
 paragraph 64. If a cylinder of commercial sulphur dioxide is not at 
 hand, the gas may be generated by the action of sulphuric acid on 
 sodium sulphite. (Convince the class that this gas is the same as 
 
90 INORGANIC CHEMISTRY 
 
 that obtained by burning sulphur.) What is the product obtained 
 in this experiment? How does the proportion of oxygen in this com- 
 pound compare with that found in sulphur dioxide? What are the 
 properties of sulphur trioxide? Why was the platinum used in this 
 experiment? What is meant by a catalyzer? What other example 
 have you had of a catalytic agent? 
 
 Ex. 54. What compound is formed when sulphur trioxide unites 
 with water? Examine the sulphuric acid of the laboratory and state 
 the physical properties. Pour ten cubic centimeters of sulphuric 
 acid slowly into twice as much water. What happens? Should the 
 water ever be poured into the acid? Why? What happens when 
 sulphuric acid stands exposed to the air? If moist air or other gas 
 were forced through sulphuric acid, would it come out drier or more 
 moist than before? Put a few drops of the acid on a clean piece of 
 wood. What happens? Dip a bit of cotton cloth, a leaf of a plant, 
 and a feather in strong sulphuric acid and describe the result. What 
 is the cause of these changes? What would be the effect of spilling 
 sulphuric acid on your flesh? On your clothing? Tell something 
 of the importance of sulphuric acid. What is a common name for it? 
 What is meant by the contact method of making this acid ? 
 
 Ex. 55. Put eight or ten drops of sulphuric acid in a tumblerful of 
 water. Taste it cautiously by dipping in a glass rod and touching 
 it to the tongue. How does the mixture taste? Dip a piece of blue 
 litmus paper into the liquid. What change takes place? Of what 
 group of compounds are the sour taste and this effect on litmus paper 
 characteristic ? 
 
 Ex. 56. Perform the experiment described in paragraph 66. What 
 is the appearance of the residue left after evaporation? Of what is 
 the material composed? What is it called? What would be formed 
 if iron were used in place of zinc? Give a general definition for sul- 
 phates. What does the chemist mean by a "salt"? How are all 
 salts formed? 
 
CHAPTER VIII 
 
 THE ATOMIC THEORY 
 
 4 
 
 68. THE modern science of chemistry was preceded by 
 the work of the alchemists during the Middle Ages. These 
 men were striving to find a method by which the common 
 metals could be converted into gold, and while they failed 
 in the particular thing they desired, they discovered many 
 substances which have been of great value to mankind. 
 Sulphuric acid, nitric acid, and hydrochloric acid, as well 
 as certain of the methods of extracting metals from their 
 ores, are discoveries which were due to the work of the al- 
 chemists. But the methods of these men were haphazard, 
 and it was not until the eighteenth century, when the use of 
 the balance made quantitative studies possible, that the 
 science now known as chemistry had its beginning. It 
 was during this period that the law of definite proportions 
 (34) and the law of multiple proportions (67) were discov- 
 ered. These laws, it should be understood, are merely con- 
 cise statements of truths that haw been proved by experiment. 
 
 It is one thing, however, to know a general fact, and quite 
 another thing to know the cause of the fact. While it is 
 known that elements combine in definite and multiple pro- 
 portions, it does not necessarily follow that it is known why 
 they combine according to these laws. It is natural for 
 man to desire to know the reason for the truths which he 
 discovers, and when the cause cannot be determined directly 
 
 91 
 
92 INORGANIC CHEMISTRY 
 
 he imagines a cause, or a condition which, if it existed, would 
 lead to the results discovered. Such a theoretical explana- 
 tion is known as a hypothesis. 
 
 If, now, this hypothesis is tested in every way that sug- 
 gests itself and all facts discovered are in accordance with it, 
 it becomes a theory. A hypothesis is a guess in regard 
 to the cause of certain phenomena, while a theory is a hy- 
 pothesis which has been thoroughly tested and found to be 
 fully in accord with the known facts. 
 
 69. The Atomic Theory. The explanation of the laws 
 of definite and multiple proportions, now generally accepted, 
 is the hypothesis formulated by Dalton, the English 
 chemist, about 1804, which has come to be known as the' 
 atomic theory. This theory assumes, (1) that all elements 
 are made up of minute independent particles called atoms 
 that cannot be subdivided, (2) that all atoms of the 
 same element have the same size and weight, while the 
 atoms of different elements have different weights, (3) that 
 when two or more elements unite, the action consists in 
 the union of a definite small number of the atoms of each 
 element to form a small particle of the compound. 
 
 70. Molecules. The atom is the smallest particle of an 
 element, but it is evident that the smallest particle of a com- 
 pound which can exist must contain more than one atom ; 
 that is, it must contain at least one atom of each ele- 
 ment in the compound and may contain more than one atom 
 of each element. This smallest particle of a compound, 
 which consists of two or more atoms, is called a molecule. 
 Even in the case of the elements it is not possible for the 
 atoms to exist in the free state, but these also combine 
 into groups or molecules. There are, therefore, two kinds 
 of molecules ; namely, the molecules of an element in which 
 
THE ATOMIC THEORY 93 
 
 all the atoms are alike, and the molecules of a compound 
 in which there are at least two different kinds of atoms. 
 The molecule of hydrogen is supposed to contain two atoms 
 of hydrogen, and the molecule of water to contain two atoms 
 of hydrogen and one of oxygen. 
 
 71. The Atomic Theory Applied. If the atomic theory 
 is accepted, it is easy to understand why elements unite 
 according to the laws of definite and multiple proportion. 
 It is assumed that the molecule of water contains one atom 
 of oxygen. If any more oxygen is added to the molecule, 
 it must be at least one whole atom, for the atom is indivisible; 
 but the addition of one more atom would exactly double 
 the amount of oxygen in the molecule. The facts are in 
 accord with the theory, for hydrogen peroxide contains 
 exactly double the quantity of oxygen that is present in 
 water. Sulphur dioxide is assumed to contain one atom of 
 sulphur and two atoms of oxygen, and sulphur trioxide to 
 contain one atom of sulphur and three atoms of oxygen. 
 This assumption is in accord with the fact that the ratio 
 of oxygen in the two compounds is as 2 to 3. It must not 
 be forgotten, however, that the laws of definite and multiple 
 proportions are truths, but that the atomic theory, although 
 it is a conception which is probably true, cannot be proved 
 to be true. All the facts of chemistry discovered since 
 the time of Dalton, however, are in perfect accord with 
 the theory, and by means of this theory chemists were able 
 to predict many of the facts which have since been discovered . 
 At the present time the existence of molecules and atoms 
 can scarcely be doubted. 
 
 72. Atomic Weights. Atoms are too small to be weighed 
 directly, but if the atoms of each element are all alike and 
 of the same weight, it ought to be possible to assign some 
 
94 INORGANIC CHEMISTRY 
 
 number to the elements which would represent the relative 
 weights of the atoms. This was first done by giving to hydro- 
 gen, which was the lightest atom, the relative weight of one, 
 and studying the combinations which the other elements 
 made with it, or with some other element whose relation 
 to hydrogen had already been established. Most of the 
 atomic weights have been determined by studying the com- 
 binations of the various elements with oxygen, which had 
 been determined to be 16 ; that is, the atom of oxygen was 
 said to be 16 times as heavy as the atom of hydrogen. As 
 a matter of fact the atomic weights are now all based on the 
 assumption that oxygen is 16, for it has been found that 
 there was a slight error in the earlier calculations and that 
 hydrogen is 1.008 if oxygen is 16. 
 
 73. Chemical Symbols. In order to avoid the incon- 
 venience of using long names the chemist represents the 
 different elements by symbols. These symbols consist of 
 the first letter of the name, unless there is more than one 
 element with the same initial letter. In that case the first 
 element discovered is designated by the initial letter, and 
 the others by the initial letter with some other characteristic 
 letter of the name; as, for instance, C is the symbol for 
 carbon, but Cl for chlorine and Ca for calcium. Chemical 
 symbols are the same the world over, hence where the initial 
 letter of the name differs in different languages an abbrevia- 
 tion of the old Latin name is used for the symbol. Fe 
 (ferrum) is the symbol for iron, and Cu (cuprum) for 
 copper. 
 
 The symbol designates not merely the element, but stands 
 in each case for one atom of the element. Thus, H repre- 
 sents one atom of hydrogen, O one atom of oxygen, S one 
 atom of sulphur. But the symbols mean even more than 
 
THE ATOMIC THEORY 
 
 95 
 
 this, for they express the atomic weights as well. Thus, 
 not only means one atom of oxygen, but also means that this 
 atom weighs sixteen times more than one atom of hydrogen. 
 The table on the inside of the back cover gives a list of the 
 elements, with their symbols and atomic weights. A few of 
 the more common elements, with their atomic weights stated 
 in round numbers, are given in the following table : 
 
 ELEMENT 
 
 SYMBOL 
 
 ATOMIC WEIGHT 
 
 Hydrogen 
 
 H 
 
 1 
 
 Oxvffen 
 
 o 
 
 16 
 
 
 N 
 
 14. 
 
 
 s 
 
 32. 
 
 Carbon 
 
 c 
 
 12. 
 
 Calcium 
 
 Ca 
 
 40. 
 
 Iron 
 
 Fe (Ferrum) 
 
 56. 
 
 Sodium 
 
 Na (Natrium) 
 
 23. 
 
 Chlorine 
 
 Cl 
 
 35.5 
 
 Phosphorus 
 
 P 
 
 31. 
 
 
 1C (Kalium) 
 
 39 
 
 Copper 
 
 Cu (Cuprum) 
 
 63 6 
 
 Zinc 
 
 Zn 
 
 654 
 
 
 
 
 If more than one atom is to be designated the proper 
 numeral is placed before the symbol, thus : 
 
 2 H means 2 atoms of hydrogen. 
 
 3 S means 3 atoms of sulphur. 
 
 But if the atoms are combined with others in a compound a 
 small numeral is placed after and below the symbol, thus : 
 
 H2 means 2 atoms of hydrogen in combination. 
 83 means 3 atoms of sulphur in combination. 
 
96 INORGANIC CHEMISTRY 
 
 EXERCISES 
 
 Ex. 57, State the law of the conservation of matter. Is the amount 
 of matter in the universe constant ? Does any matter disappear when 
 coal burns in the stove? Is the amount of each chemical element in 
 the universe always constant? What is the law of definite propor- 
 tions? Of multiple proportions? What is meant by a hypothesis? 
 A theory? 
 
 Ex. 58. State the atomic theory. Show how the atomic theory 
 explains the law of multiple proportions. What name is given to the 
 smallest amount of a compound which can exist ? Are there molecules 
 of the elements as well as of the compounds? What is meant by the 
 atomic weight of an element? By a chemical symbol? Of what 
 does the chemical symbol consist? Just what does the symbol for an 
 element, S for example, designate? 
 
CHAPTER IX 
 FORMULAS AND EQUATIONS 
 
 74. Chemical Formulas. A formula is a group of sym- 
 bols that is used to express the composition of a molecule 
 of a compound. Tfye symbols of the different elements 
 are written side by side, with the proper subscript numerals 
 representing the number of atoms of each element. Thus, 
 H 2 O is the formula for water, and indicates that a molecule 
 of water is composed of two atoms of hydrogen and one of 
 oxygen. It also indicates that water is composed of 2 parts 
 by weight of hydrogen and 16 parts by weight of oxygen. 
 Sulphur dioxide is written S02, and the trioxide SOs. As 
 the atomic weight of sulphur is 32, it is seen that the dioxide 
 consists of 32 parts by weight of sulphur to 32 of oxygen. 
 The ratio in the trioxide is 32 of sulphur to 48 of oxygen. 
 The formula also shows why one is called di-oxide and the 
 other tri-oxide. The formula for sulphuric acid is H^SO^ 
 showing that the molecule contains 2 atoms of hydrogen, 1 
 of sulphur, and 4 of oxygen, the relative weights being as 
 2 to 32 to 64. The sum of the atomic weights in a molecule 
 is the molecular weight. The molecular weight of sulphuric 
 acid is 98. 
 
 A numeral placed in front of a formula multiplies the mole- 
 cule and consequently all the atoms within the molecule. 
 Thus, 3 H 2 SO 4 represents three molecules of sulphuric acid 
 and is equivalent to 6 atoms of hydrogen, 3 of sulphur, and 
 12 of oxygen. In certain cases a group of elements which 
 
 EV. CHEM. 7 97 
 
98 INORGANIC CHEMISTRY 
 
 act together are inclosed in a parenthesis and the group 
 may be multiplied by using the subscript to the right of the 
 parenthesis ; thus, in Fe 2 (804)3 the group SC>4 is multiplied by 
 3. If a numeral is placed before this formula, as 2 Fe 2 (SO 4 ) 3 , 
 it means that the whole formula is multiplied by 2, and 
 that consequently there are six SC>4 groups present and four 
 atoms of iron. 
 
 75. Reactions. A chemical reaction is a special or limited 
 chemical change. When sulphuric acid acts on zinc to pro- 
 duce hydrogen the change which takes place is a chemical reac- 
 tion. The burning of sulphur to produce SO 2 , the uniting of 
 oxygen and copper to form copper oxide, the decomposition 
 of water by means of heated iron, are all chemical reactions. 
 
 76. Reagents. A reagent is a substance capable of pro- 
 ducing a reaction with another substance. The name is 
 sometimes confined to those chemicals which are employed 
 to detect the presence of other substances. 
 
 77. Chemical Equations. To express the various facts 
 about chemical reactions it is customary to use a sort of 
 chemical shorthand known as a chemical equation. The for- 
 mulas representing the substances which enter into the 
 reaction are connected by the plus (+) sign and form the left- 
 hand member of the equation. The formulas for the prod- 
 ucts of the reaction are placed at the right, and the equation 
 is read from left to right. In place of the sign of equality 
 as used in mathematical equations it is now customary to 
 use the arrow to connect the two members of the equation. 
 For example, it is known that when water vapor is passed 
 over heated zinc the result is the production of zinc oxide 
 and hydrogen (21). This fact may be represented by the 
 following equation : 
 
 H 2 + Zn -- ZnO + 2 H. 
 
FORMULAS AND EQUATIONS 99 
 
 The equation should not be read like an equation in mathe- 
 matics, nor should it be considered as any more than a 
 brief way of stating certain known facts. The plus sign 
 should be read " and " and the arrow translated as " yields " 
 or " produces." The above equation, then, means that 
 water and zinc act upon each other to produce zinc oxide and 
 hydrogen. It also shows that one molecule of water reacts 
 with one atom of zinc and produces one molecule of zinc oxide 
 and two atoms of hydrogen. 
 
 78. Writing Reactions. If it is remembered that the 
 equation is merely a brief way of expressing certain facts, 
 it will be understood that a complete knowledge of the reac- 
 tion is necessary before the equation can be written. The equa- 
 tion cannot be figured out mathematically, nor can the equa- 
 tion for one element be " guessed out " by knowing what 
 another will do under the same circumstances. When copper 
 burns in oxygen, the equation is 
 
 Cu + O ->- CuO. 
 But when iron burns the equation is as follows : 
 
 In the case of phosphorus it is 
 
 The reaction for the formation of water may be expressed 
 as* follows: 
 
 The preparation of oxygen is represented by the following 
 equation : KC1 Q 3 ^ KQ + 3 Q 
 
 This equation should be read : Potassium chlorate yields 
 potassium chloride and oxygen. The manganese dioxide 
 is not written into the equation because it remains unchanged 
 
100 INORGANIC CHEMISTRY 
 
 and probably acts as a catalyzer. The following equations 
 will express the reactions mentioned in the last chapter. 
 Formation of sulphides : 
 
 Cu + S ^ CuS. 
 Burning of sulphur or a sulphide : 
 
 CuS + 3 O ->- CuO + SO 2 . 
 When sulphur dioxide changes to trioxide : 
 SO 2 + O ->- SO 3 . 
 
 The platinum is not written into the equation because it 
 acts as a catalyzer and takes no actual part in the reaction. 
 When sulphuric acid is formed, the equation is 
 
 H 2 O->H 2 SO 4 , 
 
 and when sulphuric acid and zinc are used to prepare hy- 
 drogen, _ 
 
 This equation should be read : zinc and sulphuric acid yield 
 zinc sulphate and hydrogen. 
 
 Since the atoms are indestructible, it follows that the 
 same number of atoms of each element should be found on 
 both sides of the arrow. The equations are also quantita- 
 tive expressions. The last equation expresses the fact that 
 65.4 parts by weight of zinc will .react w r ith 98 parts of sul- 
 phuric acid and produce 161.4 parts of zinc sulphate and 2 
 parts of hydrogen. 
 
 Thus if the quantity of any one of the factors of the equa- 
 tion is known, it will be seen that any or all of the others can 
 
FORMULAS AND EQUATIONS 101 
 
 be calculated. For example, suppose the problem is to find 
 how much sulphuric acid is required to produce 7 pounds of 
 hydrogen. First write the equation with the molecular 
 weights (73) written below : 
 
 Zn + H 2 SO 4 -> ZnSO 4 + H 2 , 
 65.4 98 161.4 2. 
 
 The equation shows that 2 parts of hydrogen can be produced 
 from 98 parts of sulphuric acid ; this, therefore, establishes 
 the ratio, and the problem is merely a matter of simple 
 proportion : 
 
 2:98 = 7:z, x= 343. 
 
 Consequently 343 pounds of sulphuric acid are required to 
 produce the 7 pounds of hydrogen. To solve similar prob- 
 lems, first write the equation with the correct atomic or 
 molecular weights, and then state the problem in the form 
 of a proportion, like the one given above. 
 
 79. Chemical Affinity. It is not known why certain 
 substances act upon each other chemically and others do 
 not. The fact that a piece of sulphur will burn when heated 
 and platinum will not is well known, but why this is so no 
 one can tell. For want of a better name this force, or attrac- 
 tion, is called chemical affinity. Whatever this force is 
 that holds the elements together, it is very important; 
 for without it the compounds could not exist, and if it ceased 
 to act all the complex substances of the animal, vegetable, 
 and mineral kingdoms would dissociate into a few simple 
 substances known as elements. Elements that readily 
 unite are said to have great affinity for each other. Sulphur, 
 since it unites with oxygen, is said to have affinity for oxygen. 
 
102 INORGANIC CHEMISTRY 
 
 Platinum, which cannot be made to burn in air, is said to 
 have slight affinity for oxygen. 
 
 80. Valence. The power that an atom of one element 
 has to unite with one or more atoms of another element is 
 called its valence. Here, again, hydrogen is used as the 
 standard and is rated at 1. Any atom that can hold one 
 atom of hydrogen in combination is said to have a valence 
 of 1, or to be univalent. If it can combine with 2 atoms of 
 hydrogen, it is bivalent. Oxygen is bivalent because it 
 unites with 2 atoms of hydrogen (H 2 O) . Elements which do 
 not unite with hydrogen are compared with oxygen or some 
 other element which does unite with hydrogen. An atom of 
 copper unites with one atom of oxygen and consequently 
 must be bivalent. The zinc atom does not unite with hydro- 
 gen, but since it replaces the 2 atoms of hydrogen in sul- 
 phuric acid, it is bivalent. The matter of valence would 
 be very simple if all elements had just one valence, but some 
 of them vary in valence. Sulphur is apparently quadri- 
 valent in SO2 and hexavalent in SOs. When an element 
 exhibits more than one valence, it is generally true that 
 the compounds at one of the valences are much more stable. 
 The compounds in which sulphur has a valence of six are 
 much more stable than those in which it appears to have a 
 valence of four. 
 
 81. Hydrogen Peroxide. The stable combination of 
 hydrogen and oxygen is water, H 2 O, sometimes written 
 H H. In hydrogen peroxide another atom of oxygen 
 is introduced into the molecule, making it H O O H 
 or H 2 O2. This oxide of hydrogen readily changes to the 
 more stable compound v/ater, and one atom of oxygen is 
 liberated. For this reason, hydrogen peroxide, or more 
 properly dioxide, is a strong oxidizing agent. It gradually 
 
FORMULAS AND EQUATIONS 103 
 
 decomposes into water and oxygen upon standing, but does 
 so very quickly if in contact with a substance that can be 
 oxidized. The equation is 
 
 82. Physics and Chemistry. From what has been said 
 in this chapter it must be evident that so long as the molecule 
 remains intact the chemical composition of a substance does 
 not change. If the make-up of the molecule changes, new 
 substances are formed, and the change which takes place 
 is a chemical change. It may be said, then, that physical 
 changes are those in -which the composition of the molecule 
 is not affected, while in chemical changes the atoms are 
 rearranged into new and different molecules. 
 
 EXERCISES 
 
 Ex. 59. What is a chemical formula and what does it represent? 
 What is the formula for sulphuric acid ? What facts about sulphuric 
 acid are represented by this formula ? What is meant by the molec- 
 ular weight of a compound? The formula for potassium chlorate is 
 KC1O 3 ; what is its molecular weight? What percentage of oxygen 
 does it contain? 
 
 Ex. 60. What is meant by a chemical equation ? Of what use are 
 these equations? How should they be read? What must be known 
 in order to write an equation ? How much potassium chlorate would 
 be needed to produce 100 pounds of oxygen ? 
 
 What is meant by chemical affinity? By valence? The formula 
 for carbon dioxide is CO 2 ; what is the valence of carbon ? What is 
 the relation of the molecule to chemical and physical changes ? 
 
CHAPTER X 
 ACIDS OF SULPHUR AND HYDROGEN SULPHIDE 
 
 83. Sulphurous Acid. Sulphur dioxide dissolves readily 
 in water, one volume of the latter absorbing forty volumes 
 of the gas. This liquid has a sour taste and turns blue litmus 
 paper red, from which it may be inferred that the solution 
 contains an acid. The reaction may be expressed as follows : 
 
 SO 2 + H 2 ->- H 2 SO 3 . 
 
 The compound H 2 S03 is sulphurous acid. When the solu- 
 tion is heated, the acid decomposes into water and sulphur 
 dioxide, the latter being driven off. This reaction may be 
 written : 
 
 H 2 SO 3 ->- H 2 O + SO 2 . 
 
 The fact that sulphurous acid decomposes when heated 
 makes it impossible to concentrate it and obtain it free from 
 water, as can be done with sulphuric acid, which does not 
 completely decompose upon boiling. Sulphurous acid pos- 
 sesses marked bleaching properties. In fact the bleaching 
 and disinfecting properties which were referred to in de- 
 scribing sulphur dioxide should properly be ascribed to sul- 
 phurous acid, for it was noted that these effects were produced 
 when the substance acted upon was moist. Under these 
 circumstances the sulphur dioxide unites with the moisture 
 to form sulphurous acid. 
 
 104 
 
ACIDS O7 SULPHUR 105 
 
 Sulphurous acid can readily be oxidized to sulphuric acid : 
 H 2 SO 3 + O -> H 2 SO 4 . 
 
 This change is brought about to a limited extent by the 
 oxygen of the air uniting with the sulphurous acid. The 
 change can also be effected by means of oxidizing agents, 
 as, for instance, hydrogen peroxide : 
 
 H 2 SO 3 + H 2 O 2 ->- H 2 SO 4 + H 2 O. 
 
 This property of readily taking on oxygen makes sulphurous 
 acid a strong reducing agent. 
 
 84. Sulphuric Acid by Chamber Process. The older 
 method of preparing sulphuric acid, known as the chamber 
 process, depended upon the oxidation of sulphurous acid 
 by means of one of the oxides of nitrogen. Under certain 
 circumstances this compound will give up a part of its 
 oxygen, and later will take up again a like quantity of oxygen 
 from the air. This oxide may be represented by the formula 
 NO 2 . In manufacturing sulphuric acid, sulphur or pyrites is 
 burned to produce S0 2 , and this compound and steam are 
 conducted into lead-lined chambers. The lead lining is 
 used because sulphuric acid has very little effect on lead. 
 The sulphur dioxide and steam unite to form sulphurous 
 acid. The NO 2 gas which is obtained from nitric acid then 
 acts upon the sulphurous acid : 
 
 H 2 SO 3 + N0 2 ->- H 2 S0 4 + NO. 
 
 Air is also admitted, and the gas takes up oxygen and changes 
 back to NO,: 
 
 Theoretically the same amount of NO 2 could be used indefi- 
 nitely, as it acts much like a catalyzer. Practically there is 
 
106 INORGANIC CHEMISTRY 
 
 always some loss of the nitrogen oxide, since some of it is 
 dissolved in the sulphuric acid and removed from the cham- 
 ber with it. The actual chemical changes which take place 
 in the chamber are much more complicated than are indi- 
 cated in the foregoing equations, and are not fully under- 
 stood, but the essential feature of the processes this power 
 of the oxide of nitrogen to take an intermediate part in the 
 reaction between sulphurous acid and the oxygen of the 
 air, or, as it is often expressed, to act as a carrier of oxygen. 
 This process results in sulphuric acid of 50 to 60 per cent 
 strength and with some impurities, namely, lead and nitro- 
 gen compounds. Where pure acid is required the contact 
 method is generally used. The chamber method is used 
 by many of the fertilizer factories as the so-called chamber 
 acid is about the strength needed in the making of fertilizers, 
 and the little impurity found in the acid is of no moment. 
 Fully one half of all the sulphuric acid produced in the world 
 is used in the manufacture of fertilizers. 
 
 85. Two Acids of Sulphur. It will be noticed that there 
 are two acids containing hydrogen, sulphur, and oxygen, 
 the difference in the formulas being one atom of oxygen. 
 These acids are H 2 SO 3 and H 2 SO 4 . Some other elements 
 also form more than one acid in which the molecules differ 
 only in the amount of oxygen present. To distinguish be- 
 tween these acids it is customary to use the ending " ous " 
 for the acid having the smaller amount of oxygen, and the 
 ending " ic" for the acid with the larger amount, hence, 
 sulphurous acid for H^SOs and sulphuric acid for H 2 SO4. 
 In studying sulphuric acid, it was found that the hydrogen 
 of the acid could be replaced by a metal to form a saltlike 
 substance. The same thing holds true of sulphurous acid 
 in a more limited way. The best-known compound of this 
 
ACIDS OF SULPHUR 107 
 
 class is sodium sulphite, which is commonly used in pho- 
 tography. It has the formula Na^SOs. The sodium atom 
 is univalent, hence two atoms are required to replace the 
 two hydrogen atoms of sulphurous acid. The sulphites, 
 like sulphurous acid, are strong reducing agents. They 
 take on oxygen and change to sulphates, thus : 
 
 This change takes place slowly when the salt is exposed to 
 the air, and consequently nearly all samples of sulphites 
 contain some sulphates unless carefully protected. The 
 salt of an acid ending in " ous " has the suffix ite; the salt 
 of an acid ending in." ic " has the suffix ate; hence, the terms 
 sulphite and sulphate. 
 
 86. Sulphuric Acid Used to Prepare Other Acids. When 
 sulphuric acid is added to the salts of other acids, the metal 
 of the salt and the hydrogen of the sulphuric acid change 
 places, and a sulphate and the acid of the original salt are 
 formed. If sulphuric acid is added to sodium sulphite, this 
 reaction takes place : 
 
 Na^SOs + H 2 SO 4 -- NasSO, + H 2 SO 3 . 
 
 As sulphurous acid happens to be a very unstable acid and 
 is readily decomposed into sulphur dioxide and water, the 
 equation is generally written to express that fact ; thus, 
 
 Na 2 SO 3 + H 2 SO 4 ->- NasSO, + H 2 O + SO 2 . 
 
 The method used for the preparation of sulphurous acid 
 is of general application, and many of the well-known acids 
 are prepared by the action of sulphuric acid on the salt of 
 the desired acid. This method will be used repeatedly in 
 the laboratory. 
 
108 INORGANIC CHEMISTRY 
 
 87. Hydrogen Sulphide. If dilute sulphuric acid is 
 added to a sulphide, like one of the sulphides of iron, a gas 
 is given off which is colorless, but which has a very offensive 
 odor suggestive of rotten eggs. This gas, which has the 
 formula H 2 S, has been named hydrogen sulphide although 
 it is popularly known as sulphureted hydrogen. The fol- 
 lowing equation represents its formation : 
 
 FeS + H 2 S0 4 ^ FeSO 4 + H 2 S. 
 
 This gas exists naturally in sulphur springs, and in the 
 air in the vicinity of volcanoes. It is poisonous and even 
 in small quantities causes headache and nausea. It is 
 slightly soluble in water, and the solution is frequently used 
 in the analytical laboratory. This solution turns blue litmus 
 paper red and in other ways gives evidence of being an acid ; 
 it is, therefore, often called hydrosulphuric acid. Here, 
 then, is an acid which contains no oxygen, from which fact 
 it may be inferred that Lavoisier was mistaken in his idea 
 that oxygen is found in all acids. It will be seen later 
 that there are other acids which contain no oxygen, one of 
 them, hydrochloric acid, being commercially very important. 
 Hydrogen sulphide is often formed during the decay of 
 organic matter containing sulphur, especially of eggs and 
 other animal matter. As most metallic sulphides are insol- 
 uble, hydrogen sulphide added to a solution of a salt of the 
 metal will cause a precipitation of the insoluble sulphide. 
 When H 2 S is added to copper sulphate, the following reac- 
 tion takes place : 
 
 CuSO 4 + H 2 S ->- CuS + H 2 SO 4 . 
 
 The copper sulphide, being insoluble, is precipitated. A piece 
 of paper which has been moistened with a solution of a lead 
 salt, such as lead acetate (sugar of lead), turns black if 
 
HYDROGEN SULPHIDE 109 
 
 exposed to the hydrogen sulphide, owing to the formation 
 of lead sulphide. This is a test for hydrogen sulphide. 
 
 88. Chemical Tests. A chemical test is a reaction used 
 to recognize or detect the presence of a particular element 
 or compound. The blackening of lead acetate paper shows 
 the presence of hydrogen sulphide. The test for hydrogen 
 is the fact that it burns and forms water ; for oxygen, that 
 it causes a glowing splint to burst into flame. There is no 
 simple test for nitrogen because it is so inactive. The test 
 for sulphur is the fact that SC>2 is formed upon burning; 
 for a sulphite, that SC>2 is given off when a strong acid is 
 added to it; for sulphuric acid or a sulphate, that a white 
 precipitate, which will not dissolve in hydrochloric acid, 
 is formed when a solution of barium chloride is added. 
 Other tests will be discussed later. 
 
 EXERCISES 
 
 Ex. 61. Place about two ounces of water in a wide-mouth bottle 
 and shake the bottle so as to moisten its sides. By means of the 
 crayon cup (Fig. 56) burn a small quantity of sulphur in the bottle, 
 keeping the mouth covered. When the sulphur has stopped burning, 
 remove the crayon cup and shake the bottle vigorously. Have you 
 any evidence that the sulphur dioxide has dissolved in the water? 
 Taste a drop of the liquid. Test it with blue litmus paper. What are 
 the results ? Does the liquid contain an acid ? Write the equation for 
 the formation of the acid. Heat a few drops of the liquid in .a test 
 tube. Is SO 2 given off ? Write the reaction. Can sulphurous acid 
 be prepared in concentrated form? Why? Dip a piece of colored 
 calico in the liquid and note the effect. Will dry SO 2 bleach ? What 
 conditions are necessary to bleach with burning sulphur? 
 
 Ex. 62. Add a few drops of sulphuric acid to a little water in a test 
 tube. Now add a few drops of the laboratory solution of barium 
 chloride. A white precipitate which will not dissolve in hydrochloric 
 acid forms immediately. This is a test for sulphuric acid. To a little 
 
110 
 
 INORGANIC CHEMISTRY 
 
 of the solution of sulphurous acid add the barium chloride solution. 
 No precipitate will form. To another portion of sulphurous acid add 
 a few drops of hydrogen peroxide and then add barium chloride. Have 
 you any proof that sulphuric acid has been formed? Write the re- 
 action. What is the principle upon which the chamber method of 
 making sulphuric acid depends? What is the purpose of the oxide of 
 nitrogen? Why is it called a carrier of oxygen? Is the acid made 
 by the chamber process pure? What is the strength of chamber 
 acid ? Is much sulphuric acid used in the manufacture of fertilizers ? 
 
 Ex. 63. Give the formulas for the two acids of sulphur. When 
 an element forms two acids, how are they named? What are the 
 salts of sulphurous acid called ? What happens to sodium sulphite 
 upon standing exposed to the air? When sulphuric acid is added to 
 sodium sulphite, what change takes place ? Write the reaction. Is 
 this a general method for preparation of acids ? 
 
 Ex. 64. Arrange apparatus as in Fig. 73. Place in the bottle a 
 few pieces of iron sulphide. Through the thistle tube add dilute 
 
 sulphuric acid. Describe the gas which 
 is evolved. Write the reaction. Place 
 the end of the delivery tube in a bottle 
 half full of water and allow the gas to 
 bubble through for some time. Test the 
 solution with litmus paper. Have you 
 any proof that an acid is present? 
 What is it called? Does it contain 
 any oxygen ? How is hydrogen sulphide 
 formed in nature? Where is it found 
 naturally ? To a solution of copper sul- 
 phate (blue vitriol), and to a solution 
 of lead acetate, add a little of the hy- 
 drogen sulphide solution. What hap- 
 pens ? Are most of the sulphides soluble 
 or insoluble ? 
 
 Ex. 65. Explain how you could test 
 for hydrogen sulphide. How could you tell whether a solid was a 
 sulphide? Try the test with lead acetate paper. What test is used 
 to detect sulphur ? A sulphite ? Sulphuric acid and sulphates ? How 
 can you tell whether a gas is hydrogen or oxygen ? 
 
 FIG. 73. Apparatus for the pro- 
 duction of hydrogen sulphide. 
 
CHAPTER XI 
 CARBON 
 
 CAKBON is an element known to everyone in the form of 
 the diamond, graphite or black lead, charcoal, lampblack, 
 and coal. Like sulphur it exists in several allotropic forms. 
 
 89. Diamond and Graphite. The diamond is a brittle 
 crystalline form of pure carbon. It is insoluble in all liquids 
 and is the hardest substance known. If it is heated to a 
 very high temperature in such a way that air is excluded, it 
 swells and is converted into a black mass. Heated to a high 
 temperature in oxygen, it burns completely, yielding only car- 
 bon dioxide. 
 
 Graphite, also called black lead, and plumbago, is a 
 soft, shiny, black solid which is smooth and soapy 
 to the touch. Pure graphite contains nothing but carbon. 
 It exists in crystals, but the crystalline form is different 
 from that of the diamond. Like the diamond, it produces 
 only carbon dioxide when burned. It is used in the manu- 
 facture of lead pencils and stove polish, and as a lubricant 
 where oil cannot well be used. 
 
 90. Wood Charcoal. The diamond and graphite are the 
 only pure crystalline forms of carbon, but the element is 
 known in many impure and amorphous forms. One of the 
 best known of these is ordinary wood charcoal. Wood con- 
 sists largely of carbon united with oxygen and hydrogen. 
 If it is heated without access of air, the oxygen and hydrogen 
 
 111 
 
112 
 
 INORGANIC CHEMISTRY 
 
 and part of the carbon are driven off in various liquid and 
 gaseous compounds, and the remainder of the carbon is left 
 behind in the form of charcoal. It is almost pure carbon, 
 the only impurity being the small amount of mineral matter 
 which it contains. Charcoal is a black, brittle substance, 
 that often retains the form of the wood from which it was 
 made. It is insoluble in water or acids, and burns without 
 flame or smoke. It resists the action of chemicals and of de- 
 cay bacteria ; hence fence posts, and telegraph and telephone 
 poles are often charred before being put into the ground. 
 
 Wood charcoal is now commonly made by heating wood 
 in closed iron retorts, no air whatever being admitted. By 
 
 this method the vola- 
 tile products can be 
 condensed and saved. 
 Among the volatile 
 substances of value 
 produced in this way 
 are wood alcohol and 
 acetic acid. Such a 
 process as this is 
 known as destructive 
 distillation. 
 
 The older method of 
 making charcoal, and 
 the one still largely 
 used, is to construct a 
 
 FIG. 74. The exterior and section of a char- , -IP i 
 
 coal furnace. large pile ot WOOd 
 
 (Fig. 74) so arranged 
 
 as to leave spaces between the pieces. The pile is covered 
 with sods and earth to prevent free access of air, although 
 small holes are left at the bottom and a large one at the 
 
CARBON 113 
 
 top. The wood is lighted at the bottom and the fire is so 
 controlled that it will smolder. The burning of the wood 
 at the bottom of the pile heats the wood above sufficiently 
 to drive off the volatile matter. After some time the holes 
 are all closed to smother the fire, and then the pile is un- 
 covered and the charcoal is removed. A very pure form of 
 charcoal for use in medicine is sometimes produced from 
 white sugar. 
 
 91. Animal charcoal is most commonly made by heating 
 bones in closed retorts. This form is also known as bone 
 black. Unless treated with acid to dissolve the mineral 
 matter of the bone it contains only about 10 per cent of 
 carbon. Animal charcoal is produced also from dried blood, 
 a process by which a much purer form of carbon is obtained. 
 
 All these forms of charcoal have the power of absorbing 
 offensive gases and are, therefore, used as deodorizers. 
 Charcoal filters are used to remove objectionable substances 
 from water. Charcoal also removes certain coloring matters 
 from solutions. This property of charcoal (especially of 
 animal charcoal) is utilized in refining sugar. The colored 
 solution obtained from beet or sugar cane is passed through 
 bone-black filters which remove the color, making possible 
 the production of a white sugar. Charcoal is used also in 
 the manufacture of gunpowder (207). 
 
 92. Coal. The different varieties of coal, which were 
 formed by the gradual decomposition of vegetable matter in 
 an insufficient supply of air, are forms of amorphous carbon. 
 The vegetable origin is often shown by the fossil remains of 
 leaves and stems of plants found in the coal. All forms of 
 coal contain other substances in addition to the carbon. 
 The different varieties of coal are commonly classified as 
 hard and soft coals. Hard coal, or anthracite, is hard and 
 
 EV. CHEM. 8 
 
114 INORGANIC CHEMISTRY 
 
 lustrous. It is ignited with difficulty and burns with little 
 flame, producing an intense heat. It contains about 95 
 per cent of carbon. Soft, or bituminous, coal burns with a 
 smoky flame, and much volatile matter is produced, as can 
 be seen by watching the little jets of flame which dart from a 
 piece of burning soft coal. It contains about 80 per cent of 
 carbon and, therefore, has a larger percentage of other 
 compounds than has hard coal. 
 
 93. Coke is made by heating soft coal in an air-tight ap- 
 paratus. Large quantities of coke are produced in the 
 
 FIG. 75. Beehive coke ovens. 
 
 manufacture of illuminating gas. The bituminous coal is 
 placed in large retorts and heated until all volatile matter 
 is driven off, the material remaining in the retort being coke. 
 It will thus be seen that coke bears the same relation to coal 
 that charcoal does to wood. In addition to gas, referred to 
 above, the heating of soft coal drives off coal tar, ammonia, 
 and other volatile substances, which are utilized in modern- 
 coking plants. Many thousand tons of coke are made in 
 the so-called " beehive " ovens (Fig. 75), where no attempt 
 is made to save the volatile products. Millions of dollars 
 worth of valuable products are wasted annually in this way. 
 
CARBON 115 
 
 94. Lampblack is a very finely divided form of carbon 
 which is deposited on cold objects placed in the flames of 
 burning oils. Oils are very rich in carbon, and to produce 
 lampblack they are burned in a limited supply of air. When 
 the dense smoke arising from them, which is mainly finely- 
 divided carbon, is cooled, the carbon is deposited. Lamp- 
 black is one of the purest forms of amorphous carbon. It 
 is used in making printer's ink and certain black paints. 
 
 Carbon is found also in all organic substances, both animal 
 and vegetable. It is a constituent of all kinds of peat and 
 humus, as well as of natural gas, petroleum, and asphalt. 
 It exists in limestone, chalk, marble, and all other carbon- 
 ates. In the air it is found as carbon dioxide. It forms 
 more different compounds than any other element, and it 
 is said that more than 100,000 carbon compounds have 
 been prepared and analyzed. 
 
 95. Properties of Carbon. Notwithstanding their marked 
 differences in appearance all these forms of carbon have some 
 properties in common. They are insoluble in all ordinary 
 liquids. They are tasteless and odorless. They cannot be 
 melted. They can actually be changed one into the other, 
 for both graphite and diamonds of microscopic size have 
 been prepared artificially from amorphous carbon. At 
 ordinary temperatures carbon is inactive. At high temper- 
 atures all forms can be made to burn, and the prodiict in 
 each case is the carbon dioxide (CO 2 ). Carbon is a strong 
 reducing agent, and when heated with the oxide of a metal, 
 for instance, will unite with the oxygen, leaving the metal 
 free. When copper oxide is heated with charcoal the reaction 
 may be written thus : 
 
 2 CuO + C ^ 2 Cu + CO 2 . 
 
116 INORGANIC CHEMISTRY 
 
 This method is commonly used in the extraction of metals 
 from their ores. If the ore is an oxide, it is heated directly 
 with carbon. If the metal is in the form of a sulphide it is 
 first roasted to change it to the oxide, after which it is reduced 
 by heating it with carbon. The chief use of carbon, however, 
 is as a fuel. 
 
 96. Flames due to a Burning Gas. In Chapter V, com- 
 bustion was defined as " the union of a substance with 
 oxygen with the evolution of light and heat." In the every- 
 day sense, however, combustion consists in the burning, or 
 oxidation, of a material containing carbon ; for all ordinary 
 fuels, whether gaseous, liquid, or solid, contain carbon. A 
 marked difference is noticeable in the manner in which 
 the different fuels burn. Some of them burn with a flame 
 and some do not. The gases all produce flames, and so do 
 the liquid fuels. Of the solid fuels, wood and soft coal burn 
 with a flame, while charcoal and coke do not. Anthracite 
 gives a very feeble flame. Careful study of flames has 
 shown that they always consist of burning gases. That this 
 is true of a gaseous fuel is evident, but it is equally true of 
 kerosene or other burning oils. In the case of the kerosene 
 lamp, for instance, the gas which burns is produced from the 
 oil which is drawn up the wick by capillary attraction and 
 then volatilized by the heat of the flame. 
 
 In the case of the candle the heat first melts the wax, and 
 the liquid thus formed is drawn up the wick and then con- 
 verted into a gas that burns. That gas is actually formed 
 during the burning of a candle can be shown by placing the 
 lower end of a piece of glass tubing in the center of the 
 flame ; the gas passes up the tubing and can be ignited at the 
 upper end A (Fig. 76) . Flames are produced when wood and 
 soft coal are burned, because both these materials contain 
 
CARBON 
 
 117 
 
 FIG. 76. Ignition of 
 gas from the inner zone of 
 a candle flame. 
 
 volatile substances which are converted into gases by the 
 heat. The method of preparing charcoal and coke is such 
 that all these volatile substances are 
 driven off. Charcoal and coke, there- 
 fore, burn without a flame because 
 there is no volatile matter present to 
 be converted into a gas. Anthracite 
 contains very little volatile matter, 
 and so the flaming during its burning 
 is very slight. 
 
 97. Luminosity of Flames. There 
 is a marked difference in the lumi- 
 nosity of flames, the variation de- 
 pending partly on the gas itself and 
 partly on the way in which it is 
 
 burned. Hydrogen burns with a non-luminous flame; 
 natural gas gives more light than hydrogen but not so much 
 as coal gas ; and acetylene burns with a more luminous 
 flame than either natural gas or coal 
 gas. It has been found that when the 
 combustion of a gas is complete the 
 flame is always non-luminous. The 
 Bunsen burner used in the laboratory 
 illustrates this point (Fig. 77). It is 
 constructed with the idea of mixing 
 the gas and the air in such proportions 
 as to bring about the complete com- 
 bustion of the gas. The gas enters at 
 FIG. 77. -section of a Bun- the base of the burner at A and is 
 
 sen burner. m j xed ^^ ^ ^ entermg at t h e side 
 
 holes BB, and the mixture of gas and air is burned at the 
 top C. If the amount of air entering at BB is properly 
 
118 INORGANIC CHEMISTRY 
 
 adjusted, the flame will be blue and non-luminous. If the 
 openings at the bottom of the burner are closed so that no 
 air can enter, the flame becomes yellow in color and luminous. 
 
 The luminosity of the flame is easily explained. A piece 
 of platinum wire placed in the blue flame of the Bunsen 
 burner becomes white-hot and gives off light. If some fine 
 iron dust is blown into it, the flame becomes momentarily 
 luminous. The same effect may be produced with charcoal 
 dust or fine table salt. In these experiments it is evident 
 that the light comes from a solid substance which has been 
 heated to a white heat or to incandescence. The same 
 thing is true of all luminous flames. In the flame produced 
 by any of the ordinary illuminants there is a place in the 
 flame where the combustion is not complete. The heat de- 
 composes some of the gaseous compounds and the carbon 
 is set free. It is this very finely divided carbon heated to in- 
 candescence that gives off the light. A gas like acetylene, 
 which is very rich in carbon, therefore, gives more light than 
 one like natural gas, which is relatively low in carbon. In 
 general, then, it may be said that light is produced by a 
 solid substance which is heated to incandescence. In the 
 Welsbach burner the light comes from the mantle, the 
 material of which is heated by the blue flame of the Bunsen 
 burner. In the limelight the lime is heated to incandescence 
 by the oxyhydrogen flame, and in the electric bulb the fila- 
 ment is heated by the electric current ; but the light in each 
 case comes from the heated solid. 
 
 98. Structure of Flames. The luminous flame has several 
 distinct parts, as can readily be seen in the flame of the 
 candle. A vertical section of the candle flame is represented 
 in Fig. 78. Around the wick there is a dark cone A filled 
 with combustible gases formed from the melted wax, which 
 
CARBON 
 
 119 
 
 FIG. 78. A ver- 
 tical section of can- 
 dle flame showing 
 the three zones. 
 
 do not burn because there is no oxygen present. It was from 
 this cone that the gas was drawn in Fig. 76. Above the dark 
 cone is the luminous part of the flame B. 
 Here the oxygen is insufficient for complete 
 combustion, but the temperature is suffi- 
 ciently high to decompose some of the gas 
 and liberate small particles of carbon. This 
 liberated carbon heated by the burning gas 
 makes the flame luminous. A piece of crayon 
 held in this part of the flame will at once be 
 coated with carbon. The exterior cone C 
 is almost invisible, because here there is 
 plenty of oxygen and combustion is complete, 
 and all the carbon is burned to carbon di- 
 oxide. These three regions will be found 
 in all illuminating flames, 
 whatever their shape, as 
 can be seen by carefully examining the 
 flat flame of the ordinary gas burner or 
 the flame of the kerosene lamp. In the 
 non-luminous flame of the Bunsen burner 
 two principal regions are easily distin- 
 guished, an inner cone A of unburned gas 
 and an outer cone B, where the combus- 
 tion is complete. The hottest part of the 
 flame is just above the inner cone A 
 (Fig. 79). 
 
 99. Kindling Temperature of Gases. 
 Gases, like other substances, must be kept 
 at their kindling temperature in order to 
 burn. If they are cooled below the kindling temperature, 
 the flame is extinguished. If a piece of wire gauze is pressed 
 
 FIG. 79. A verti- 
 cal section of the 
 Bunsen flame show- 
 ing the two zones. 
 
120 
 
 INORGANIC CHEMISTRY 
 
 down on the flame of a Bunsen burner, the flame remains 
 below the gauze, although the gas passes freely through 
 it and escapes. If the gas is now extinguished and then 
 relighted above the gauze, it will burn 
 above but not beneath (Fig. 80). The 
 explanation is that the gauze conducts 
 away the heat rapidly enough to cool 
 the gas below its kindling temperature. 
 100. Davy's Safety Lamp. The 
 miner's feafety lamp depends upon this 
 
 FIG. 80. Showing how wire gauze cools the gas be- 
 low the kindling point. 
 
 FIG. 81. Davy's 
 safety lamp. 
 
 principle. It is an oil lamp surrounded by fine wire gauze 
 (Fig. 81). In a mine where there are explosive gases the 
 lamp will continue to burn, and some of the gas may even 
 enter the lamp and burn inside ; but since the wire gauze 
 prevents the gas on the outside from being heated to its 
 kindling temperature, explosions are often prevented. 
 
 EXERCISES 
 
 Ex. 66. Heat some sawdust, a piece of cotton, a bit of bone, a piece 
 of lean meat, and some sugar or starch in test tubes or in a covered 
 
CARBON 
 
 121 
 
 iron dish. What residue do you get in these experiments? Hold a 
 piece of crayon in the flame of a candle. What is the black coating 
 on the crayon? What do these experiments show as to the distribu- 
 tion of carbon? Name some other substances containing carbon. 
 Give the properties of carbon. What is formed when carbon burns? 
 Tell what you can about the following forms of carbon : (1) diamond, 
 (2) graphite, (3) wood char- 
 coal, (4) animal charcoal, 
 (5) coal, (6) lampblack. 
 
 Ex. 67. Mix a teaspoon- 
 ful of copper oxide with an 
 equal quantity of powdered 
 charcoal and place it in a hard 
 glass test tube. Arrange as 
 in Fig. 82, allowing the end 
 of the rubber tubing to dip 
 into a bottle containing lime- 
 water. Heat the tube cau- 
 tiously until gas ceases to be 
 evolved, and remove tubing 
 from the water. What has 
 happened to the limewater? 
 To the copper oxide? Ex- 
 plain the change in the cop- 
 per oxide and write the reaction. What kind of agent is carbon ? Is 
 any commercial use made of this property of carbon ? 
 
 Ex. 68. Put half a test tube full of bone black into a small flask 
 and pour in about two ounces of water to which have been added a 
 few drops of indigo or litmus. Mix, heat gently for a few minutes, and 
 filter. Has anything happened to the color?,. Name an industry 
 in which animal charcoal is used as a decolorizer. 
 
 Fill a test tube half full of powdered wood charcoal. Add 2 cc. 
 of a solution of hydrogen sulphide. Cork the tube securely and 
 shake it thoroughly for some time. Let it stand for fifteen minutes ; 
 then remove the stopper and note whether the odor is less offensive. 
 Is charcoal ever used as a deodorizer? 
 
 Ex. 69. Place some pieces of soft coal in a small porcelain crucible 
 and connect it with the bowl of a clay pipe, making the connection 
 
 FIG. 82. Heating charcoal and copper 
 oxide and passing the resulting gas into lime- 
 water. 
 
122 
 
 INORGANIC CHEMISTRY 
 
 tight with clay (Fig, 83). Heat in the Bunsen flame. Does any- 
 thing escape through the stem of the pipe ? Will the escaping material 
 burn? When all the volatile matter has been expelled, examine the 
 
 residue in the crucible. What is it? 
 Explain how illuminating gas is manu- 
 factured. How is coke produced ? 
 
 Ex. 70. Does the blue flame of the 
 Bunsen burner give much light ? Hold 
 a piece of platinum wire in the flame. 
 Is more light produced? Sprinkle a 
 little charcoal dust or some fine salt 
 in the flame. Does it make the flame 
 more luminous ? To what is the lumi- 
 nosity of the flame due ? Why is the 
 acetylene flame more luminous than 
 that of natural gas? What makes the 
 light in the Welsbach burner? Draw 
 a diagram of the flame of a candle and 
 indicate the different zones. What 
 makes the flame of the candle lumi- 
 nous? 
 
 Ex. 71. Do all substances burn with a flame? What substances 
 produce flames? How can you show that the flame of a candle is 
 due to a burning gas? Light a candle and allow it to burn a few 
 minutes. Light a match, -blow out the candle, and apply the match 
 to the ascending smoke. Repeat, noting whether the candle can be 
 lighted at a distance from the wick. Explain how this is possible. 
 Why does wood burn with a flame while charcoal does not ? 
 
 Ex. 72. Press a piece of wire gauze halfway down on a Bunsen 
 flame (Fig. 80). Does the flame pass through the gauze ? Does any 
 unburned gas pass through ? Turn off the gas, then turn it on again 
 and light it above the gauze (Fig. 80). Does the gas burn below 
 the gauze ? Explain the results in these two cases. How is the miner's 
 safety lamp constructed? Explain how it prevents explosions. Do 
 gases have a definite kindling temperature ? 
 
 FIG. 83. Apparatus to illustrate 
 the manufacture of illuminating gas 
 and coke. 
 
CHAPTER XII 
 CARBON COMPOUNDS 
 
 101. Carbon Burns to Carbon Dioxide. If a piece of char- 
 coal is ignited and placed in a bottle containing oxygen, it 
 will burn violently, throwing off a shower of sparks, and the 
 bottle will be filled with a gas having a slightly pungent 
 odor. Limewater placed in the bottle becomes milky, and a 
 white precipitate settles out. The carbon has burned to 
 carbon dioxide, which fact may be expressed thus : 
 
 C + 2 O ->- CO 2 . 
 
 This behavior with limewater is a test for carbon dioxide, 
 since no other gas acts in this way. If the products of com- 
 bustion from a gas jet, from burning alcohol, or from the 
 flame of a candle or kerosene lamp are collected. by holding 
 an empty wide-mouth bottle over the flame for a moment, 
 and then tested with limewater, it will be found that the 
 milkiness is produced in each case. In other words, when 
 any substance containing carbon is burned, the carbon is oxi- 
 dized to carbon dioxide. 
 
 102. Carbonic Acid. If a little water is added to a bottle 
 in which charcoal has been burned, the carbon dioxide will 
 dissolve in it. This water will turn blue litmus paper red, 
 and has a very faintly sour taste, which suggests that an acid 
 is present. When carbon dioxide is dissolved in water, it 
 forms a weak, unstable acid according to the equation, 
 
 This compound, H 2 CO 3 , is carbonic acid. It is so unstable that 
 
 123 
 
124 
 
 INORGANIC CHEMISTRY 
 
 even at low tenrpwatures it breaks up into carbon dioxide 
 and water ; thus : 
 
 (Compare with the reaction of sulphur dioxide and water 
 (83).) The instability of carbonic acid makes it impossible 
 to obtain it free from water. Many of its salts, which are 
 called carbonates, are known. The carbonates are stable 
 compounds and most of them are insoluble in water. Lime- 
 stone, marble, and chalk are all calcium carbonate (CaCO 3 ), 
 the salt formed by replacing the hydrogen of carbonic acid 
 with metal calcium. Washing soda, or sodium carbonate 
 (Na 2 CO3), is another well-known salt of carbonic acid. 
 
 103. Preparation of Carbon Dioxide. When a strong 
 acid like sulphuric acid acts on a carbonate, the carbonic 
 
 acid is set free; but since the 
 latter is, for the most part, im- 
 mediately decomposed into car- 
 bon dioxide and water, the reac- 
 tion is usually written thus ; 
 
 Na*C0 3 + H 2 S0 4 -> 
 
 Na*SO 4 + CO 2 + H 2 O. 
 
 This reaction may be used for 
 the preparation of carbon di- 
 oxide, but the more usual labo- 
 ratory method is by the action 
 of hydrochloric acid on marble, 
 or ordinary limestone. Hydro- 
 chloric acid is used because its 
 compound with calcium is soluble in water (Fig. 84), while 
 calcium sulphate is not. The reaction is indicated thus : 
 
 CaCO 3 + 2 HC1 -> CaCl 2 + CO 2 + H 2 O. 
 
 FIG. 84. Production of carbon 
 dioxide from limestone and hydro- 
 chloric acid. 
 
CARBON COMPOUNDS 
 
 125 
 
 104. Properties of Carbon Dioxide. Carbon dioxide is 
 a colorless gas with a slightly pungent odor and acid taste. 
 It is one and one half times heavier than air. 
 It can be poured from one vessel to another. 
 At ordinary temperature and pressure water 
 dissolves its own volume of carbon dioxide. 
 Under increased pressure water dissolves much 
 more of the gas, and as the pressure is re- 
 leased the gas escapes. Soda water is made 
 by forcing carbon dioxide into water under 
 
 FIG. 85. Si- 
 phon bottle used 
 to hold carbon- 
 ated water. 
 
 pressure, and the escape 
 of the gas as the pressure 
 is released accounts for 
 the effervescence and froth- 
 ing when it is drawn from the fountain 
 or a siphon bottle (Fig. 85). Many 
 mineral waters, as well as manufactured 
 beverages, sparkle and effervesce for the 
 same reason. Carbon dioxide is some- 
 what easily liquefied and is sold in large 
 quantities in steel cylinders. Liquid car- 
 bon dioxide is used in the manufacture 
 of soda water and to produce very low 
 temperatures. Many of the small fire 
 extinguishers (Fig. 86) contain baking 
 soda and sulphurio 'acid so arranged 
 that they can be mixed at the moment 
 needed. The mixture of water and CC>2 
 under pressure will often put out a small 
 blaze and prevent a serious fire. Air 
 
 containing 3 to 4 per cent of carbon dioxide will extinguish 
 
 small flames. 
 
 FIG. 86. Section of 
 fire extinguisher. 
 
126 INORGANIC CHEMISTRY 
 
 Carbon dioxide will not burn because it is itself the product 
 of the complete combustion of carbon. Carbon dioxide will not 
 support combustion nor sustain life. It is not poisonous, 
 but animals placed in it die of suffocation. Water contain- 
 ing carbon dioxide will dissolve many substances which are 
 but slightly soluble in pure water. This property of car- 
 bonated water is due to the presence of carbonic acid, which 
 is formed when carbon dioxide dissolves in water. All soil 
 water contains carbonic acid, which is an important factor in 
 changing the insoluble constituents of the soil into soluble 
 forms. 
 
 105. Carbon Dioxide and Plant Life. It has been shown 
 that carbon dioxide comprises about .03 per cent to .04 per 
 cent of the atmosphere, or three to four parts in ten thou- 
 sand. This carbon dioxide is the sole source of the carbon 
 found in green plants, and, since all animals live directly 
 or indirectly upon plants, it is the source of all the carbon 
 found in both animal and vegetable tissues. Green plants 
 have the power of abstracting carbon from carbon dioxide and 
 uniting it with other substances to form the various complex 
 compounds found in the plants. This power of the green 
 plant is dependent upon the green coloring matter, or chloro- 
 phyll, which is found in the leaves. The first visible effect 
 of the action of chlorophyll is the presence of starch in the 
 leaves. The chlorophyll apparently brings about a reaction 
 between carbon dioxide and water, which may be represented 
 by the following equation : 
 
 6 CO 2 + 5 H 2 O > C 6 H 10 O 5 + 12 O. 
 
 starch 
 
 That green leaves decompose carbon dioxide and liberate 
 the oxygen can be shown by a simple experiment. A quan- 
 
CARBON COMPOUNDS 
 
 127 
 
 tity of water is charged with carbon dioxide by running a cur- 
 rent of the gas from a generator through it for a few minutes. 
 Some sprigs of mint, water cress, or some other plant are 
 placed in a glass cylinder and covered 
 with carbonated water. A funnel 
 and a test tube filled with water are 
 arranged, as shown in Fig. 87, so as 
 to collect any gas which may be 
 formed. The apparatus is placed in 
 the strong sunlight, and after a short 
 time bubbles of gas will arise and 
 replace the water in the test tube. 
 When sufficient gas has collected, 
 the test with a glowing splint will 
 show that it is oxygen. 
 
 Sunlight is necessary to furnish 
 the plant with the energy required to 
 decompose the carbon dioxide. When 
 carbon burns to carbon dioxide, a 
 large amount of heat is given off. 
 This heat is known as the heat, of 
 formation. Before such a compound 
 as carbon dioxide can be decomposed, 
 
 an amount of energy must be provided which is equiva- 
 lent to the heat energy which was given off when the com- 
 pound was formed ; or, in other words, an amount of energy 
 equivalent to the heat of formation of the compound. The 
 plant derives this energy from the sunlight, and conse- 
 quently the formation of starch in the plant does not go on 
 at night. It will thus be seen that without sunlight all life 
 would cease, for every living thing is dependent either 
 directly or indirectly upon the decomposition of carbon 
 
 FIG. 87. The decompo- 
 sition of carbon dioxide and 
 liberation of oxygen by plants. 
 
128 
 
 INORGANIC CHEMISTRY 
 
 dioxide by plants (340). The process by which plants 
 utilize the carbon of carbon dioxide to form starch is called 
 photosynthesis (341). 
 
 106. Amount of Carbon Dioxide in the Atmosphere. The 
 percentage of carbon dioxide in the atmosphere is so small 
 that it might be feared that the supply would soon be ex- 
 hausted. So great is the bulk of the atmosphere, however, 
 that it has been calculated that the air contains not less than 
 3,400,000,000,000 tons of carbon dioxide. This amounts 
 to 28 tons over each acre of the earth's surface. 
 
 CARBON; DIOXIDp 
 IN ATMOSPHERE: 
 
 FIG. 38. The cycle of carbon in nature. 
 
 107. Formation of Carbon Dioxide in Nature. The supply 
 of carbon dioxide in the atmosphere is being constantly re- 
 newed in several ways. The burning of fuels of all kinds re^ 
 
CARBON COMPOUNDS 129 
 
 suits in the production of carbon dioxide, as does also the 
 decay of all organic matter. Fermentations, such as take 
 place in wines and cider, and in breweries and distilleries, 
 give rise to carbon dioxide. It is also given off in the vicinity 
 of volcanoes and from mineral springs. It is exhaled by the 
 breathing of all animals as well, for it is the product of the 
 slow combustion of carbon in the animal body. Carbon 
 dioxide sometimes accumulates at the bottom of wells, in 
 silos, and in mines, since it is often formed in such places 
 more rapidly than it can be removed by diffusion. Many 
 deaths have occurred from suffocation in such places. 
 Carbon dioxide is called choke damp by the miners. The 
 production of carbon dioxide in the various ways mentioned 
 is so nicely balanced by the decomposition of this gas by 
 green plants, that the amount of carbon dioxide and of oxy- 
 gen in the air scarcely varies. The cycle of carbon in nature 
 is indicated in Fig. 88. 
 
 108. Carbon Monoxide. When a substance containing 
 carbon is burned in an insufficient supply of air, carbon monox- 
 ide (CO) is formed. If carbon dioxide is passed over highly 
 heated carbon, a reaction takes place which is represented by 
 the following equation : 
 
 CO 2 + C -^ 2 CO. 
 
 Carbon monoxide is formed during the burning of hard coal 
 in a stove or grate. At the lower part of the fire, where there 
 is free access of air, the carbon burns to carbon dioxide, but 
 as it passes up through the heated coal the dioxide is par- 
 tially reduced to carbon monoxide. When the monoxide 
 escapes from the top, it again combines with oxygen and 
 burns with the blue flame always noticed above a mass of 
 EV. CHEM. 9 
 
130 INORGANIC CHEMISTRY 
 
 burning hard coal. Pure carbon monoxide is a colorless, 
 tasteless, and odorless gas, which burns with a pale blue 
 flame. It is exceedingly poisonous. It is the most dangerous 
 gas given off from coal stoves, and great precaution should 
 be taken to prevent its escape into the room. 
 
 109. Water Gas. In the manufacture of coal gas it is 
 customary to take advantage of the fact that highly heated 
 carbon will decompose water. After all the volatile matter 
 has been driven off from coal, and while the coke is still 
 very hot, steam is turned into the retorts with the result that 
 the following reaction takes place : 
 
 H 2 O + C -^ CO + H 2 . 
 
 This mixture of hydrogen and carbon monoxide is known 
 as water gas. Only a limited quantity of the gas can be 
 made, as the coke is soon cooled below the point at which it 
 will decompose water. As both hydrogen and carbon mon- 
 oxide burn with a non-luminous flame, water gas cannot be 
 used as an illuminating gas unless it is first enriched by the ad- 
 dition of some petroleum product high in carbon. Owing to 
 its high percentage of carbon monoxide, water gas is very poi- 
 sonous. 
 
 110. Carbon Bisulphide. Carbon forms one important 
 compound with sulphur. The two elements are made to 
 combine in an electric furnace, the resulting compound being 
 carbon bisulphide, CS 2 . Commercial carbon bisulphide is a 
 yellow liquid with an offensive odor. It is poisonous, volatile, 
 and very inflammable. The equation for its combustion is 
 
 Carbon bisulphide is insoluble in water. It dissolves rubber, 
 
CARBON COMPOUNDS 131 
 
 gums, fats, camphor, and sulphur (60) . The common rubber 
 cement is a solution of rubber in carbon bisulphide. Carbon 
 bisulphide is used as an insecticide and to exterminate bur- 
 rowing animals such as moles, woodchucks, and gophers. 
 As its vapor is much heavier than air it readily sinks to the 
 bottom of the burrow. 
 
 111. Other Compounds of Carbon. It has been stated 
 that more than 100,000 compounds of carbon have been 
 prepared. Most of these compounds are of animal or vege- 
 table origin, and the study of these numerous and complex 
 compounds is commonly called organic chemistry. It was 
 formerly thought that these compounds could be produced 
 only by life processes, but many of them have been produced 
 artificially. It is more convenient, however, to deal with 
 this subject after the chemistry of the other common ele- 
 ments has been studied. The more common and important 
 of the carbon compounds will be discussed in Part II of this 
 text. 
 
 EXERCISES 
 
 Ex. 73. Ignite a piece of Charcoal and place it in a bottle containing 
 oxygen. Note the odor of th gas formed. Place a little limewater 
 in the bottle. What happens to the limewater? What is the gas 
 formed by burning carbon? Hold an empty bottle over the flame of 
 a candle and test it with limewater. What is the result? Take 
 some limewater home with you and test any flames for carbon dioxide. 
 
 Ex. 74. Place a little water in the bottom of a wide-mouth bottle 
 and burn a piece of charcoal in the bottle. Shake the bottle and test 
 the water with litmus paper. Is an acid formed ? Write the equation. 
 What happens when the solution is warmed? Compare with the re- 
 actions for sulphur dioxide. Can carbonic acid be prepared in the 
 pure state? Are its salts (the carbonates) stable? Name a common 
 carbonate. 
 
132 
 
 INORGANIC CHEMISTRY 
 
 Ex. 75. Arrange apparatus as in Fig. 84 and place several pieces 
 of marble or limestone in the bottle and cover with water. Pour 
 dilute hydrochloric acid in the thistle tube and collect the carbon 
 dioxide by downward displacement as shown in the figure. What is 
 the appearance of the gas ? What is its odor and its taste ? Light a 
 candle, place it in a tumbler, and pour a bottleful of carbon dioxide 
 over it (Fig. 89). What happens to the candle? Is CO 2 heavier than 
 air? Place a bottle of air mouth down- 
 ward over a bottle of carbon dioxide. 
 After ten minutes test the contents of the 
 upper bottle for CO 2 . What is the result ? 
 What effect does pressure have on the 
 solubility of the gas in water ? What use 
 is made of this fact ? What use is made 
 of liquid carbon dioxide? How do the 
 small fire extinguishers work? Why will 
 carbon dioxide not burn? Is it poison- 
 ous ? Why do animals die when placed in 
 it? Why does water containing carbon 
 dioxide dissolve some minerals which are 
 insoluble in pure water ? How many sub- 
 stances can you find at home which are carbonates or contain car- 
 bonates ? Test them with hydrochloric acid and note whether CO 2 is 
 given off. 
 
 Ex. 76. Fill a tall glass cylinder with water and cause carbon 
 dioxide to bubble through it for a few rrinutes. Place several sprigs 
 of mint or water cress in the cylinder and arrange a funnel and test 
 tube as shown in Fig. 87. Place the apparatus in strong sunlight 
 and when sufficient gas collects in the test tube test for oxygen with a 
 glowing splint. How do green plants obtain their carbon ? Is chloro- 
 phyll necessary for this process ? Why is sunlight necessary to enable 
 the plant to use the carbon of carbon dioxide ? What is heat of forma- 
 tion? How much carbon dioxide does the atmosphere contain? Is 
 there any danger of the supply being exhausted by plants? How is 
 the supply of CO 2 in the air renewed ? Why is it dangerous to go into 
 a well or a silo that has been closed tightly for some time ? What 
 name do the miners give to carbon dioxide ? 
 
 FIG. 89. Extinguishing 
 a candle by pouring carbon 
 dioxide gas over it. 
 
CARBON COMPOUNDS 133 
 
 Ex. 77. What other oxide of carbon is known ? Explain the forma- 
 tion of this oxide in the coal stove. Reaction? Why should coal 
 stoves and furnaces be gas tight? How is water gas made? Give 
 reaction. Is it a good illuminating gas? How can it be improved 
 as an illuminant? What important compound does carbon form 
 with sulphur? Reaction? In what experiment did you use this 
 substance? For what purposes is carbon bisulphide used? If there 
 is an ant hill at home try the following experiment. With a stick make 
 a hole an inch or two in diameter and a foot deep in the ant hill. Pour 
 in two ounces of carbon bisulphide and cover the hole with earth. 
 Place a piece of carpet or a blanket over the ant hill. Examine after 
 twelve hours and report. 
 
CHAPTER XIII 
 
 LIMESTONE AND OTHER CALCIUM COMPOUNDS 
 
 112. Limestone. One of the 
 
 substances in nature is limestone. 
 
 most widely distributed 
 It is most familiar as the 
 
 , ordinary limestone 
 
 used for building pur- 
 poses ; but marble, 
 chalk, coral, marl, 
 and shells are identi- 
 cal in composition 
 with limestone. They 
 all consist largely of 
 the compound made 
 by the combination 
 of the metal calcium 
 with carbonic acid; 
 namely, calcium car- 
 bonate, GaCO 3 . In 
 marble the calcium 
 carbonate exists as a 
 mass of minute crys- 
 tals. Chalk and 
 most limestone are 
 not crystalline, but often show by their structure that they 
 have been derived from shells. The transparent crystals of 
 calcite and Iceland spar (Fig. 91) are very pure forms of cal- 
 
 134 
 
 FIG. 90. A limestone cliff. 
 
LIMESTONE AND OTHER CALCIUM COMPOUNDS *135 
 
 cium carbonate. Calcium carbonate is insoluble in water. 
 It is decomposed by most acids, with the result that carbon 
 dioxide is given off 
 and the calcium 
 salt of the acid is 
 formed. (See 103.) 
 113. Manufac- 
 ture of Lime. When 
 calcium carbonate 
 is strongly heated, 
 carbon dioxide is 
 driven off and cal- 
 cium oxide remains, 
 thus: 
 
 FIG. 91. Crystals of calcite. 
 
 Calcium oxide, CaO, is the substance known as lime, also 
 called burnt lime, quicklime, or caustic lime. The pro- 
 cess of preparing 
 lime is termed 
 " burning lime," 
 which is a mis- 
 nomer, as burn- 
 ing consists in 
 the uniting of a 
 substance with 
 oxygen, while 
 this process is a 
 decomposition 
 and not an oxi- 
 dation. The 
 
 FIG. 92. A homemade limekiln. " burning " of 
 
136 
 
 INORGANIC CHEMISTRY 
 
 limestone 
 
 lime is one of the oldest of chemical processes and has been 
 carried on for at least fifty centuries. 
 
 In the older method of preparing lime a fire of wood or 
 coal is made at the bottom of the limekiln, which is a 
 
 shaft or chimney quite 
 commonly built in a hill- 
 side. When the limestone 
 which is placed on the fuel 
 is completely burned, it is 
 removed and the kiln is re- 
 filled. At the present time 
 kilns (Fig. 93) are so built 
 that the operation is con- 
 tinuous, limestone being 
 added at the top of the 
 kiln and the lime being 
 removed from the bottom 
 as fast as it is formed. 
 Lime is most familiar in 
 the form of lump, or 
 builder's, lime. It is often 
 ground to a powder and 
 sold as ground lime. 
 
 114. Slaked Lime. 
 When lime is sprinkled 
 
 with water, it becomes very hot, swells, and finally crumbles 
 to a white powder. This process is called slaking the lime, 
 and the white powder is known as slaked lime or hydrated 
 lime. The chemical name for it is calcium hydroxide. The 
 change may be represented thus : 
 
 FIG. 93. A modern limekiln. 
 
 CaO + H 2 O ->- Ca(OH) 2 . 
 
CALCIUM COMPOUNDS 137 
 
 Calcium hydroxide, Ca(OH) 2 , is somewhat soluble in 
 water, and this solution is called limewater. It will thus 
 be seen that calcium oxide behaves toward water in much 
 the same way as do the oxides of sulphur and carbon ; that 
 is, it forms a chemical compound with the water. But when 
 sulphur trioxide, for instance, is added to water, the solution 
 has a sour taste and it turns blue litmus paper red. Lime- 
 water, on the other hand, has an astringent, or alkaline, taste, 
 and does not change the color of blue litmus paper. On the 
 contrary, if the paper which was turned red by the acid is 
 placed in limewater, the blue color will be restored. It will 
 be found that there are other oxides which behave in the 
 same way. Evidently, then, not all oxides form acids with 
 water, but some form compounds with properties the oppo- 
 site of acids. 
 
 Limewater is used in medicine, and as previously men- 
 tioned is used in the chemical laboratory as a test for carbon 
 dioxide, with which it forms the insoluble calcium carbonate, 
 the equation being 
 
 Ca(OH) 2 + CO 2 -^ CaCO 3 + H 2 O. 
 
 When considerable calcium hydroxide is suspended in water, 
 the mixture is called milk of lime. Ordinary whitewash is 
 thin milk of lime. 
 
 Mortar is a thick paste made by mixing slaked lime and 
 sand. It sets or hardens partly owing to the loss of water 
 by evaporation, but also because carbon dioxide is absorbed 
 and the calcium hydroxide is changed into the carbonate. 
 The same change takes place in whitewash when it is spread 
 on a wall. The hardening of plaster may be hastened by 
 burning charcoal in the room so as to increase the amount 
 of carbon dioxide in the air. 
 
138 INORGANIC CHEMISTRY 
 
 115. Air-slaked Lime. When lime is exposed to the air, 
 it absorbs moisture and slakes. It also absorbs carbon diox- 
 ide from the air and changes to the carbonate : 
 
 CaO + CO 2 -> CaCO 3 . 
 
 Lime that has undergone this change to the hydroxide and 
 carbonate is said to be air-slaked and is of no value for 
 making mortar. Fires are known to have been caused by 
 the heat generated by the action of moisture on lump lime. 
 The agricultural uses of lime are discussed in Chapter LV. 
 
 116. Cement. Portland cement is made by mixing lime- 
 stone and clay, in the proper proportions, and heating them 
 strongly until the mass begins to melt. The clinker formed 
 in this way is ground to fine powder, which is the cement. 
 Occasionally an impure limestone is found which contains 
 the right quantity of clay and sand, and this is burned 
 directly to make the so-called natural cement. When cement 
 is moistened it sets to a hard, stone-like mass. Mixed with 
 sand and stone it forms concrete, which is rapidly taking 
 the place of stone in many building operations. The chemi- 
 cal changes which take place in cement are not understood. 
 
 117. Calcium. The element calcium is the fifth most 
 abundant element in nature, but it is never found uncombined. 
 It is seldom seen outside of chemical laboratories. It is a 
 silver-white metal, soft enough to be cut with a knife. It 
 will burn to the oxide (Ca + O ->- CaO), which is the same 
 compound as that formed by heating the carbonate. It 
 decomposes water at ordinary temperatures, forming the hy- 
 droxide and giving off hydrogen, thus : 
 
 Ca + 2 H 2 O ->- Ca(OH) 2 + 2 H. 
 
 When steam was passed over hot zinc, as was seen in Chap- 
 ter II, the metal extracted the oxygen from the water to form 
 
CALCIUM COMPOUNDS 139 
 
 the oxide and set free both atoms of hydrogen. When cal- 
 cium acts upon the water at ordinary temperatures, it liber- 
 ates only one atom of hydrogen from the molecule of water, 
 and the oxygen and the remaining hydrogen atom unite with 
 the metal. The change may be represented thus : 
 
 H O H /OK K 
 
 Ca + -- Ca^ + 
 
 H O H X)H H 
 
 The calcium atom, being bivalent, has replaced one hydrogen 
 atom from each of two molecules of water. The group OH, 
 which may be said to be water with one hydrogen atom re- 
 moved, is of common occurrence in chemical compounds and 
 has been named hydroxyl. 
 
 118. Calcium sulphate occurs in large quantities and is 
 widely distributed in the substance known as gypsum, which 
 has the formula, CaSO4 2 H 2 O. The two molecules of water 
 set off by the period in the formula represent the water of 
 crystallization. Although the water of crystallization can 
 be driven off by heat, there is good reason to believe that it 
 13 in chemical combination with the rest of the compound. 
 Water of crystallization is not apparent as moisture. It is 
 in some way essential to the crystalline form, in which it is 
 always present in a definite proportion. The molecule of 
 gypsum always crystallizes with two molecules of water. 
 
 Gypsum occurs as white masses or as transparent crystals. 
 It is slightly soluble in water, one part dissolving in 400 parts 
 of water. When heated it loses part of its water of crystalli- 
 zation and is known as plaster of Paris. When water is added 
 to plaster of Paris, the lost water is taken up again, and the 
 material is changed back to gypsum and sets as a hard, com- 
 pact mass. Plaster of Paris is used in coating walls, in 
 
140 
 
 INORGANIC CHEMISTRY 
 
 making stucco, and in making casts and reproductions of 
 statuary and small objects. If the gypsum is heated too 
 strongly, the plaster is spoiled and will not set. 
 
 119. Hardness of Water. In Chapter II mention was 
 made of temporary and permanent hardness of water, and it is 
 now possible to explain these phenomena. Temporary hard- 
 ness is caused for the most part by the presence of calcium 
 carbonate in the water. Calcium carbonate will not dissolve 
 in pure water, but will do so to a limited extent in water con- 
 taining carbon dioxide. This is due to the formation of acid 
 calcium carbonate Ca(HCO3)2, thus : 
 
 CaCO 3 + H 2 CO 3 ->- Ca(HCO 3 ) 2 . 
 
 In acid calcium carbonate it is supposed that the atom of 
 calcium replaces one hydrogen atom from each of two mole- 
 cules of carbonic acid. 
 As most natural 
 waters contain car- 
 bon dioxide, this 
 compound is gen- 
 erally present in 
 water. It is very 
 unstable and when 
 heated is decom- 
 posed into ordinary 
 calcium carbonate, carbon dioxide, and water : 
 
 FIG. 94. A cone built up from deposits made by 
 carbonated spring water. 
 
 Ca(HCO 3 ) 2 ->- CaC0 3 + CO 2 + H 2 O. 
 
 This reaction explains why boiling the well water causes a 
 deposit of calcium carbonate and makes the water less hard. 
 On a large scale it is not practicable to boil the water to 
 soften it, and the same result is brought about by adding 
 
CALCIUM COMPOUNDS 141 
 
 just sufficient slaked lime to convert the acid carbonate into 
 the normal carbonate, as shown in the following equation : 
 
 Ca(HCO 3 ) 2 + Ca(OH) 2 ->- 2 CaCO 3 + 2 H 2 O. 
 
 Hardness of water is not entirely due to calcium com- 
 pounds. Magnesium (Chapter XXII) is usually associated 
 with calcium in nature, and part of the hardness of water is 
 usually due to magnesium compounds, which act in much the 
 same way as do the compounds of calcium. 
 
 Permanent hardness of water is due to the presence of 
 gypsum in solution, a compound which is not precipitated by 
 boiling. To remove calcium sulphate ordinary washing soda 
 (sodium carbonate) is added, and the following reaction 
 takes place : 
 
 CaSO 4 + Na 2 CO 3 > CaCO 3 
 
 The calcium carbonate being insoluble is precipitated and the 
 sodium sulphate (N^SC^) which stays in solution is not ob- 
 jectionable. Such a chemical change as the one repre- 
 sented in this reaction is called a double decomposition. It 
 will be noticed that metals have changed places in the salts. 
 The change might be represented thus 
 
 Ca\ x SO 4 
 
 It is a general rule of chemistry that when two compounds 
 in solution are mixed, their component parts rearrange them- 
 selves to form the most insoluble compound possible, and of 
 course the insoluble compound is then precipitated. Cal- 
 cium carbonate, being the most insoluble compound possible 
 in this mixture, is precipitated, and the sodium sulphate, 
 being very soluble, remains in solution. 
 
142 INORGANIC CHEMISTRY 
 
 In the softening of water for technical purposes the water 
 is carefully analyzed and the proper amount of calcium 
 hydroxide is first added to precipitate the carbonates. After 
 a short time the sodium carbonate is added to remove the 
 other calcium and magnesium salts. ' The household methods 
 for softening water are discussed in Chapter XL VIII. 
 
 EXERCISES 
 
 Ex. 78. Place two or three thin chips of marble on a wire gauze 
 and heat them ten minutes in the full flame of the burner. Compare 
 with an unheated bit of marble. What is the composition of the 
 marble ? What change took place upon heating ? Write the reaction. 
 What substances can you name that are calcium carbonate? Can 
 you name anything in your home that is composed of calcium carbon- 
 ate ? How is lime made commercially ? 
 
 Ex. 79. Lay one of the heated chips of marble from the above 
 experiment on a piece of red litmus paper and on another piece of 
 the same paper place a bit of unchanged marble. Moisten both pieces 
 and describe what happens. Is there any difference in the effect of 
 the two pieces of stone on the litmus paper? 
 
 Ex. 80. Place a lump of quicklime in a beaker and moisten with 
 hot water. Watch and describe the result. Write the reaction for 
 the change in the lime. Fill the beaker with water and stir. When 
 the solid settles, decant the clear liquid into a clean bottle. Is the 
 calcium hydroxide soluble? Test a portion of the limewater with 
 blue and red litmus papers. What is the effect? How does the 
 compound of calcium oxide and water compare with the compound of 
 sulphur dioxide and water? What is meant by milk of lime? By 
 whitewash? What is mortar? What makes mortar set? What is 
 meant by air-slaked lime ? Is it of any value for building purposes ? 
 Tell what you can about the manufacture and uses of Portland cement. 
 What are natural cements ? Report on anything at home that is built 
 with Portland cement or concrete. 
 
 Ex. 81. Describe the element calcium. What compound is formed 
 when it burns? Give the equation for the reaction of calcium on 
 
CALCIUM COMPOUNDS 143 
 
 water. (Note to the teacher. Metallic calcium may be obtained at 
 a moderate cost from some of the supply houses. It will be well to 
 perform the experiment of liberating hydrogen from water by means 
 of metallic calcium if possible.) Does calcium replace all the hydro- 
 gen of water? What name is given to the group OH in chemistry? 
 How many hydroxyl groups unite with one atom of calcium ? 
 
 Ex. 82. Examine crystals of calcium sulphate. What is the for- 
 mula ? The common name ? What happens to gypsum when heated ? 
 Mix plaster of Paris to a thick paste with water. Rub a little vaseline 
 or lard over the surface of a button and press the button into the sur- 
 face of the moist plaster. When the plaster has hardened, remove 
 the button and describe the result. What made the plaster of Paris 
 set ? What uses can you give for plaster of Paris ? 
 
 Ex. 83. Dilute a little limewater with an equal volume of distilled 
 water. Pass carbon dioxide into the solution. Does a precipitate 
 form ? Continue the experiment and note if the precipitate disappears. 
 Write two equations, one for each change. Boil a portion of this liquid. 
 What happens? Explain the reappearance of the precipitate. Boil 
 some well water from home. Does a precipitate form? Show how 
 this experiment explains temporary hardness of water. To another 
 portion of the solution formed above by passing carbon dioxide into 
 limewater add a fresh portion of limewater. What result do you 
 obtain? How can lime be used to remove temporary hardness of 
 water ? 
 
 Ex. 84. To the well water which has been boiled to remove the 
 temporary hardness add sodium carbonate (washing soda). Is a 
 precipitate formed? Explain how permanent hardness is removed 
 from water. Give the reaction. What is meant in chemistry by a 
 double decomposition? 
 
CHAPTER XIV 
 SALT: CHLORINE AND SODIUM 
 
 120. SALT is familiar to everyone as a white solid which, 
 upon close examination, is seen to consist of cubical crystals. 
 It is widely distributed. It is found in solution in sea water 
 to the extent of 3.5 per cent, and in some countries all the 
 table salt is obtained from this source. The water of Great 
 
 FIG. 95. The making of salt by the evaporation of sea water in France. 
 
 Salt Lake contains over 20 per cent of salt. The substance 
 occurs in many places as rock salt, and is often mined in 
 large blocks and sold in this form or purified for table use. 
 Much of the salt of commerce is obtained by drilling wells 
 into the salt deposits, and introducing water, which dis- 
 solves the salt, forming a brine which is pumped out and 
 evaporated. 
 
 The appearance and taste of salt are familiar. Water 
 dissolves 35 per cent of its own weight of salt, the substance 
 
 144 
 
SALT : CHLORINE AND SODIUM 145 
 
 being nearly as soluble in cold water as in hot, in which 
 respect it differs from most solids. When it is pure it re- 
 mains dry on exposure to the air, but it usually contains a 
 little calcium or magnesium chloride and hence attracts 
 moisture. In addition to its well-known uses, it is the chief 
 source of the compounds of sodium and chlorine. 
 
 121. Action of Sulphuric Acid on Salt. When sulphuric 
 acid is poured upon common salt, a gas is given off which 
 has a strong, irritating odor. It fumes strongly in the air, 
 and a burning candle thrust into it is immediately extin- 
 guished. This gas is extremely soluble in water, one volume 
 of water dissolving over 500 volumes of the gas. Formerly 
 this gas was called spirit of salt because it was prepared from 
 salt. 
 
 The solution of the gas in water is strongly acid. It is 
 wry sour and turns blue litmus paper red. Its acid properties 
 were early recognized, and it received the name of muriatic 
 acid. This solution will be found, upon comparison, to be 
 identical with the hydrochloric acid of the laboratory, which 
 is in reality a solution of hydrochloric acid containing about 
 40 per cent of the gas. 
 
 122. Composition of Hydrochloric Acid. If the solution 
 of hydrochloric acid is poured upon zinc, hydrogen will be 
 evoked just as it is when sulphuric acid and zinc are used. 
 It is fair to assume, therefore, that hydrochloric acid con- 
 tains hydrogen as one of its elements. 
 
 If another portion of strong hydrochloric acid solution is 
 placed in an apparatus like that shown in Fig. 96, with a 
 quantity of manganese dioxide, and the flask is gently 
 heated, a gas is evolved which has a yellow-green color and 
 an irritating odor. This gas was discovered by Scheele in 
 1774. About 1810 the English chemist Sir Humphry 
 
 EV. CHEM. 10 
 
146 
 
 INORGANIC CHEMISTRY 
 
 Davy proved it to be an element and named it chlorine 
 because of its color. This gas also evidently came from 
 the hydrochloric acid, since the manganese dioxide and 
 
 water alone will not pro- 
 duce it. 
 
 If a mixture of chlorine 
 and hydrogen is exposed to 
 strong sunlight or the light 
 from burning magnesium, it 
 explodes, and the hydrogen 
 and chlorine combine to form 
 hydrochloric acid gas. This 
 method of synthesizing hy- 
 drochloric acid shows that it 
 contains the two elements 
 hydrogen and chlorine and 
 t IG. 96. - Apparatus^ the production of not hi ng else. If the combi- 
 nation were brought about 
 
 in a eudiometer (Fig. 54), it would be found that ex- 
 actly equal volumes of the two gases combine. As chlorine 
 is 35.46 times as heavy as hydrogen, it follows that hydro- 
 chloric acid is composed of 1 part by weight of hydrogen 
 to 35.46 parts by weight of chlorine. Its molecular weight, 
 therefore, is 1 + 35.46 or 36.46. The formula assigned to 
 it is HC1. It is an example of a very important acid that 
 contains no oxygen. 
 
 123. Chlorine is irritating to the lining of the nose and 
 throat and if breathed in large quantities causes inflamma- 
 tion. It is 2.5 times heavier than air, and hence is collected 
 by downward displacement. Chlorine is one of the most 
 active elements and is never found in the free state. It dis- 
 solves in water, the solution being known as chlorine water. 
 
CHLORINE 147 
 
 This solution is frequently used as a substitute for the gas. 
 If the solution is placed in the sunlight, oxygen is liberated 
 and hydrochloric acid is formed : 
 
 H 2 + C1 2 ->- 2 HC1 + O. 
 
 Chlorine is a powerful bleaching agent. This property 
 probably depends upon the above reaction, the bleaching 
 being due to the liberated oxygen, for the chlorine does not 
 act upon colored fabrics unless they are moist. Chlorine 
 combines directly with many metals, forming chlorides : 
 
 Cu + 2 Cl ->- CuCl 2 . 
 
 The chlorides may also be formed by the action of hydro- 
 chloric acid on the metal or on an oxide of the metal : 
 
 Zn + 2 HC1 -- ZnCl 2 + 2 H ; 
 CaO + 2 HC1 -- CaCl 2 - r H 2 O. 
 
 124. Bleaching Powder. Large quantities of chlorine are 
 needed in the bleaching industries, but as it is inconvenient 
 to handle or transport the free gas it is stored in the form of 
 bleaching powder, sometimes called bleach or improperly 
 chloride of lime. It is made by passing chlorine over slaked 
 
 Ca(OH) 2 + 2 Cl ->- CaOCl 2 + H 2 O. 
 
 The formula CaOCl 2 is the one usually given for bleach- 
 ing powder. When needed, the chlorine can be again 
 obtained from the bleaching powder by treating it with 
 sulphuric acid : 
 
 CaOCl 2 + H 2 S0 4 -^ 2 Cl + CaSO 4 + H 2 O. 
 
 In addition to its use in providing chlorine for bleaching, 
 this powder is valuable as a disinfectant. It is slowly de- 
 
148 INORGANIC CHEMISTRY 
 
 composed by the carbon dioxide of the atmosphere, and the 
 chlorine is liberated : 
 
 CaOCk + CO 2 -- CaCO 3 + 2 Cl. 
 
 The disinfecting properties are probably due to the libera- 
 tion of oxygen produced by the action of the chlorine on 
 water. 
 
 125. Sodium. It is comparatively easy, as has been 
 shown, to determine that chlorine is one of the elements 
 found in salt, but there is no method suited to the small 
 laboratory that will show what else is present in salt. If, 
 however, the salt is fused and an electric current is passed 
 through it, chlorine will be given off at the positive pole, 
 while at the negative pole a new substance will be found. 
 It is a soft solid which has a silver-white metallic luster, 
 and becomes covered with a coating of white material when 
 exposed to the air. It is the metal known as sodium (Na). 
 If a bit of sodium is warmed and placed in a bottle full 
 of chlorine, it burns with a dazzling yellow light and a white 
 powder is formed which can be identified as salt. Shavings 
 of cold sodium thrown into a jar of chlorine are slowly con- 
 verted into a white mass of salt. Common salt, then, is 
 the compound formed by the union of the metal sodium 
 and the gas chlorine. It is sodium chloride (NaCl) and is 
 evidently the sodium salt of hydrochloric acid, for it yields 
 that acid when acted upon by sulphuric acid, the, equation 
 
 bemg : 2 NaCl + H 2 SO 4 -- Na^SC* -f 2 HO 
 
 Sodium is very active chemically and combines readily with 
 many other elements, especially with chlorine and oxygen. 
 It is kept in coal oil, as it absorbs oxygen and moisture from 
 the air and quickly tarnishes. It decomposes water more 
 
SODIUM 149 
 
 vigorously than calcium does, liberating one half the hydro- 
 gen and forming sodium hydroxide : 
 
 The water containing sodium hydroxide (NaOH) has a soapy 
 feel when rubbed between the fingers and it exhibits the 
 property of turning red litmus paper blue in a more marked 
 way than does limewater. When burned in the air sodium 
 is changed to sodium oxide (2 Na + O ->- Na^O), which 
 added to water gives the hydroxide : 
 
 126. Sodium hydroxide is better known under the name 
 of caustic soda or soda lye. It is a white solid which readily 
 absorbs water and carbon dioxide if exposed to the air. It 
 has a very corrosive effect on animal and vegetable tissues. 
 The chemically pure hydroxide is usually cast into sticks. 
 Sodium hydroxide is used in many industries, especially in 
 the manufacture of hard soaps. The material sold in cans 
 as potash or lye is usually crude sodium hydroxide. It is 
 sometimes produced by passing the electric current through 
 strong brine, a process which causes hydrogen and chlorine 
 to be given off and which allows the hydroxide to remain in 
 solution. It is also made by boiling sodium carbonate with 
 milk of lime : 
 
 NasCOs + Ca(OH) 2 -- 2 NaOH + CaCO 3 . 
 
 The solution of sodium hydroxide is separated from the 
 insoluble calcium carbonate and concentrated by heating 
 in iron kettles. 
 
 127. Sodium sulphate (Na^SC^ 10 H 2 O) is commonly 
 known as Glauber's salt. It is produced when sulphuric 
 
150 INORGANIC CHEMISTRY 
 
 acid acts upon common salt (121). It forms large crystals 
 which are efflorescent; so the commercial article usually 
 contains some white powder. It is used- in medicine and 
 in the manufacture of washing soda and of glass. 
 
 128. Sodium sulphite (Na^SOa 7 H 2 O) was mentioned in 
 Chapter X. It is prepared by the action of sulphur dioxide 
 on sodium hydroxide. The equation is 
 
 SO 2 + 2 NaOH ^NasSOs + H 2 O. 
 
 When treated with an acid, sodium sulphite yields sulphur 
 dioxide (86). 
 
 129. Sodium carbonate (Na^COs 10 H 2 O) is the substance 
 known as washing soda or sal soda. It crystallizes in large 
 crystals which are strongly efflorescent. When the sulphite 
 and the carbonate are dried until most of the water of 
 crystallization is driven off they are said to be anhydrous. 
 The solution of sodium carbonate is slightly alkaline and 
 will turn red litmus paper blue. It is used to soften water 
 and to make soap, and in the manufacture of glass and 
 many chemical reagents. 
 
 130. Sodium bicarbonate (NaHCO 3 ) or faking soda is 
 carbonic acid with only one of the hydrogen ? corns replaced 
 by sodium. It can be made by passing carbon dioxide 
 through a strong solution of sodium carbonate ; or in other 
 words, by the action of carbonic acid on sodium carbonate. 
 The equation is : 
 
 NasCOs + H 2 CO 3 ->- 2 NaHCO 3 . 
 
 As the bicarbonate is much less soluble than the carbonate, 
 it settles out. When heated it gives off carbon dioxide and 
 water, and changes back to the normal carbonate : 
 
 2 NaHCO 3 -- Na.COs + CO 2 + H 2 O. 
 
SODIUM 
 
 151 
 
 When mixed with any acid material, such as sour milk or 
 tartaric acid, it gives off carbon dioxide. This property 
 accounts for its Use in cooking, the liberated carbon dioxide 
 being the substance that makes bread, pastry, or cake 
 light (427). 
 
 131. Test for Sodium. To test for sodium dip a platinum 
 wire into the substance to be tested and place it in the non- 
 luminous flame (Fig. 97). A deep yellow color given to 
 the flame shows the pres- 
 ence of sodium. As sodium ^ rvv 
 chloride is present nearly 
 
 everywhere, precaution 
 must be taken to prevent 
 the accidental introduction 
 of this material when test- 
 
 FIG. 97. Flame test for sodium. 
 
 ing for sodium. 
 
 132. Test for Hydrochloric Acid or a Chloride. Add to 
 
 the solution of the substance a few drops of the laboratory 
 solution of silver nitrate. A white curdy precipitate, or a 
 milkiness, which does not dissolve in nitric acid, is proof of 
 the presence of hydrochloric acid or a chloride. 
 
 EXERCISES 
 
 Ex. 85. Tell what you can about the distribution of salt in nature. 
 How is salt prepared for use? To what extent fe salt soluble? Is it 
 any more soluble in hot water than in cold? Is that true of most 
 soluble solids? Why does ordinary table salt become moist in the 
 air ? Will pure salt remain dry ? 
 
 Ex. 86. Place some salt in the flask (A) of an apparatus like Fig. 
 96 and add sulphuric acid. Gently warm and collect some of the 
 gas by downward displacement. How does the gas behave in contact 
 with the air? Cautiously note the odor of the gas. Will it burn or 
 support combustion? Is it soluble in water? Hold a piece of moist 
 
152 
 
 INORGANIC CHEMISTRY 
 
 blue litmus paper in the gas. What change takes place ? Dip litmus 
 paper in the aqueous solution of the gas. Compare this solution 
 with the hydrochloric acid of the laboratory. What is the composi- 
 tion of the latter? Can you show that hydrochloric acid contains 
 hydrogen ? (122) 
 
 Ex. 87. Clean out the apparatus used in the last experiment and 
 place some manganese dioxide in the flask (A). Add some strong hydro- 
 chloric acid and heat the mixture. Collect several portions of the 
 gas by downward displacement, allowing as little of the gas as possible 
 to escape into the room. What is the color of the gas? Cautiously 
 note the odor. What is the name of the gas ? Why was it so named ? 
 What was the source of this gas in the experiment? Will it dissolve 
 in water? Place a colored flower and a moist piece of colored calico 
 in a bottle full of the gas. Will chlorine bleach dry materials? To 
 what is the bleaching due ? Write the reaction between chlorine and 
 water. What is formed by the action of chlorine on a metal? In 
 what other ways may chlorides be formed? How may it be proved 
 that hydrochloric acid is composed of hydrogen and chlorine? In 
 what proportions by volume do the gases combine? In what pro- 
 portion by weight ? 
 
 Ex. 88. In a test tube place 
 some bleaching powder. Moisten 
 with water and add sulphuric 
 acid. What gas is given off? 
 Write the reaction. Explain 
 how bleaching powder is manu- 
 factured. Write the reaction. Of 
 what use is bleaching powder ? 
 
 Ex. 89. (Teacher.) Drop a 
 piece of sodium the size of a grain 
 of wheat on the surface of a pan 
 of water. Do not stand too close 
 as the sodium sometimes explodes. 
 Touch the sodium while on the 
 water with a taper. Is an inflammable gas evolved ? Wrap a similar 
 piece of sodium loosely in tin foil (to make it sink) and collect the gas 
 in a test tube previously filled with water as shown in Fig. 98. Test 
 the gas with a lighted splint. Write the reaction. Does the sodium 
 
CHLORINE AND SODIUM 
 
 153 
 
 liberate all the hydrogen of water? Is sodium chemically active? 
 Why is it kept in coal oil ? How is it prepared from common salt ? 
 
 Ex. 90. What compound remains when sodium acts upon water? 
 What effect does the solution of sodium hydroxide have on litmus 
 paper? Compare with limewater and hydrochloric acid. What is 
 the common name for sodium hydroxide ? For what is it used ? What 
 is the substance sold in cans under the name of potash? How is it 
 manufactured ? 
 
 Ex. 91. Examine and describe ordinary washing soda. What is 
 its chemical name and formula ? What is meant by anhydrous sodium 
 carbonate ? Dissolve a little washing soda in water and test with litmus 
 paper. What is a common use for this 
 material ? Make a saturated solution 
 of sodium carbonate and pass carbon 
 dioxide through it. (See Fig. 99.) 
 What happens? What is the compo- 
 sition of the precipitate? Write the 
 reaction. Add hydrochloric acid to 
 washing soda and baking soda. Re- 
 sult? Which would yield the most 
 carbon dioxide, a pound of washing 
 soda or a pound of baking soda? 
 Add baking soda to sour milk. What 
 gas is given off ? How can you prove 
 that a gas is carbon dioxide? 
 
 Ex. 92. Dip a platinum wire in a 
 
 solution of table salt and place it in the non-luminous flame. What 
 happens ? Hold a piece of glass rod in the flame. Have you any evi- 
 dence that there is sodium in the glass ? What is the test for sodium ? 
 Test a solution of common salt with the laboratory solution of silver 
 nitrate. Is this a general test for chlorides ? Ask the teacher to give 
 you several substances and see if you can tell which are chlorides. 
 
 FIG. 99. Passing carbon di- 
 oxide through a solution of sodium 
 carbonate. 
 
CHAPTER XV 
 ACIDS, BASES, AND SALTS 
 
 133. Acids. When sulphur trioxide was added to water 
 (65), the solution had a sour taste and turned blue litmus 
 paper red. The same thing was found to be true in a less 
 marked way of sulphur dioxide (83) and of carbon dioxide 
 (102) ; and the combinations made by these oxides with 
 water were called acids. The oxides of several other ele- 
 ments behave in the same way as those of sulphur and 
 carbon, and these compounds, known as acids, are of great 
 importance. The acids mentioned must, from their method 
 of preparation, contain hydrogen, oxygen, and some other 
 element, but it has been shown that not all acids are formed 
 by the union of an oxide with water. A few acids, one of 
 which is hydrochloric acid, are formed by the union of one 
 other element with hydrogen and contain no oxygen. All 
 acids contain hydrogen, which may be replaced by a metal 
 with the formation of a saltlike substance. Most acids 
 will decompose carbonates, liberating the carbon dioxide 
 with effervescence. 
 
 134. Bases. Not all oxides form acids when united with 
 water. It has been seen that when calcium oxide or sodium 
 oxide unites with water the compound formed has proper- 
 ties quite different from the acids. Solutions of these com- 
 pounds turn red litmus paper blue, have a brackish taste, 
 and do not decompose carbonates. These compounds are 
 
 154 
 
ACIDS, BASES, AND SALTS 155 
 
 known as bases and contain a metal combined with oxygen 
 and hydrogen. 
 
 135. Neutralization. A solution of sodium hydroxide, 
 as has been said, turns red litmus paper blue, and a solu- 
 tion of hydrochloric acid turns blue litmus paper red. If, 
 now, the hydrochloric acid solution is carefully added to 
 the sodium hydroxide and the solution tested from time to 
 time by placing a drop on litmus paper, a point can be 
 found when the solution does not affect litmus paper at all. 
 It will turn neither the red paper blue nor the blue paper 
 red. The solution has neither a sour nor a brackish taste. 
 In fact, all the characteristic properties of both acid and base 
 have disappeared, and the two are said to have neutralized 
 each other, the act being known as neutralization. When an 
 acid and a base neutralize each other the action is quanti- 
 tative; that is, it always takes exactly the same amount 
 of the acid to neutralize a given quantity of the base. If 
 the quantity of either acid or base is known, the other can 
 easily be calculated. 
 
 136. Salts. If the solution resulting from neutralizing 
 sodium hydroxide with hydrochloric acid is evaporated to 
 dryness, it will be found that the white substance remain- 
 ing in the dish is common salt (sodium chloride). If sul- 
 phuric acid is neutralized with sodium hydroxide, the prod- 
 uct is sodium sulphate (Glauber's salt).. Calcium hydrox- 
 ide and sulphuric acid give calcium sulphate (gypsum). 
 These compounds are examples of a class of substances 
 known as salts. When any acid is neutralized by a base one 
 of the products formed is a salt; the other product in every 
 case is water. The formulas for sodium chloride (NaCl), 
 sodium sulphate (Na 2 SO 4 ), and calcium sulphate (CaSO 4 ) 
 indicate that the formation of the salt really consists in the 
 
156 INORGANIC CHEMISTRY 
 
 replacing of the hydrogen of the acid by a metal, such as 
 sodium or calcium. The reaction for the formation of 
 calcium sulphate is typical : 
 
 Ca(OH) 2 + H 2 SO 4 -- CaSO 4 + 2 H 2 O. 
 
 It will be seen that the metallic part of the base (Ca) re- 
 places the hydrogen of the acid, and this hydrogen combines 
 with the hydrogen and oxygen of the base to form water. 
 
 137. Definitions. An acid is a compound containing 
 hydrogen, which may be replaced by a metal, the product 
 formed being a salt. 
 
 A base is a compound which contains hydroxyl combined 
 with a metal (or a basic radical) and which, when treated 
 with an acid, easily exchanges its metal for hydrogen. 
 
 A salt is a compound formed when a metal replaces one or 
 more of the hydrogen atoms of an acid. Salts may be formed 
 also by the action of an acid (1) on a metal, and (2) on an 
 oxide : 
 
 (1) Fe + H 2 SO 4 -*- FeSO 4 + H 2 ; 
 
 (2) FeO + H 2 S0 4 -> FeSO 4 + H 2 O. 
 
 138. Alkali. The bases or hydroxides formed by most 
 of the metals are insoluble in water. The hydroxides of 
 sodium, potassium, calcium, and a few others are soluble in 
 water and show in a marked way the property of producing 
 a blue color with certain vegetable dyes. They are also 
 caustic in their action. These hydroxides are called alka- 
 lies. A substance that turns litmus or other of these vege- 
 table dyes blue is said to have an alkaline reaction. A sub- 
 stance that turns the blue litmus red is said to have an acid 
 reaction, and one that has no effect on litmus is said to be 
 neutral. The organic coloring matter that is used to de- 
 
ACIDS, BASES, AND SALTS 157 
 
 termine whether a substance is alkaline, acid, or neutral 
 is called an indicator. Litmus is the most common indicator. 
 Other important indicators are solutions of phenolphthalein 
 and methyl orange two coal tar compounds, and the 
 aqueous extract of the cochineal insect. 
 
 139. Naming the Acids, Salts, and Bases. Those acids 
 which are composed of only two elements (binary acids) 
 are given the prefix hydio and the suffix ic. The salts of 
 such acids have the suffix ide, and the prefix hydro is dropped ; 
 thus : 
 
 Hydrochloric acid (HC1). Sodium chloride (NaCl). 
 Most acids contain three elements hydrogen, oxygen, and 
 one other element and are known as ternary acids. Such 
 acids are given the ending ic, no prefix being used, and the 
 salt is given the ending ate : 
 
 Sulphuric acid (H 2 SO 4 ). Calcium sulphate (CaSO 4 ). 
 
 In case an element forms more than one acid containing 
 oxygen, the one containing the larger percentage of oxygen 
 is given the ending ic and the other the suffix ous. The 
 salt in this latter case has the ending ite : 
 
 Sulphurous acid (H 2 SO 3 ). Sodium sulphite (Na 2 SO 3 ). 
 All the bases are called hydroxides, the name of the metal or 
 basic radical being prefixed ; for example, potassium hydrox- 
 ide (KOH). 
 
 140. Normal, Acid, and Basic Salts. Some of the acids, 
 as sulphuric acid (H 2 SO 4 ) and carbonic acid (H 2 CO 3 ), con- 
 tain two atoms of hydrogen in the molecule. Sodium has 
 a univalent atom which has the power of replacing only 
 one hydrogen atom. It is possible to bring about a com- 
 bination in which only one hydrogen atom of the acid is 
 
158 INORGANIC CHEMISTRY 
 
 replaced, as for instance, NaHSO 4 , in which half the hydro- 
 gen in sulphuric acid is replaced by sodium. Such a salt 
 is known as an acid salt because it contains hydrogen, the 
 characteristic constituent of acids. The salt in which all 
 the hydrogen is replaced is a normal salt. For example, 
 NaHS04 is acid sodium sulphate, sometimes called sodium 
 hydrogen sulphate; and Na 2 SO4 is normal sodium sul- 
 phate. Baking soda, or sodium bicarbonate, NaHCO 3 , is 
 another example of an acid salt. The acid salts, when 
 treated with a base, are converted into normal salts ; and 
 it has been shown that normal salts can be changed to the 
 acid salts by the action of an acid : 
 
 NaHSO 4 + NaOH -- Na 2 SO 4 + H 2 O; 
 H 2 SO 4 ->- 2 NaHSO 4 . 
 
 (See also sodium bicarbonate and calcium bicarbonate.) 
 The acids which have only one hydrogen atom in the mole- 
 cule obviously cannot form acid salts. There are also a 
 few salts in which the base is not completely neutralized 
 by the acid. Such salts are known as basic salts. 
 
 141. Non-metals and Metals. It has been seen that 
 certain elements form oxides which unite with water to pro- 
 duce acids, while the oxides of other elements form bases 
 with water. The base-forming elements are for the most 
 part metals (sodium, iron, zinc, copper). The acid form- 
 ing elements, with a few exceptions, have no metallic prop- 
 erties. It is customary for the sake of convenience in dis- 
 cussion to divide the elements into two classes non- 
 metals and metals. Those elements that have at least one 
 oxide that unites with water to form an acid are classified 
 as non-metals. Those elements whose oxides form bases 
 are known as metals. Unfortunately for the simplicity of 
 
ACIDS, BASES, AND SALTS 159 
 
 this classification there are " border line " elements that 
 are sometimes acidic and sometimes basic. 
 
 Note. An oxide which forms an acid when added to water is called 
 an anhydride. Sulphur trioxide is sulphuric anhydride ; that is, it is 
 the oxide which forms sulphuric acid when added to water. Formerly 
 the anhydrides were called acids, and even at the present time confu- 
 sion is sometimes caused by the fact that in trade certain anhydrides 
 are listed as acids. 
 
 The following elements are selected for discussion in this 
 text: 
 
 NON-METALS, OB ACID-FORMING ELEMENTS METALS, OB BASE-FOBMINQ ELEMENTS 
 
 Hydrogen Sodium 
 
 Oxygen Potassium 
 
 Nitrogen Calcium 
 
 Sulphur Magnesium 
 
 Carbon Copper 
 
 Chlorine Silver 
 
 Phosphorus Zinc 
 
 Silicon Aluminum , 
 
 Arsenic Lead 
 
 Boron Iron 
 
 Six of the non-metals and two of the metals have already 
 been discussed. The remaining non-metals will next be 
 considered, and afterward the metals and their salts. 
 
 Hydrogen really belongs in a class by itself but for con- 
 venience it is usually classed as a non-metal. 
 
 EXERCISES 
 
 Ex. 93. Dissolve about two grams of sodium hydroxide in 100 
 cubic centimeters of water. Add 5 cubic centimeters of hydrochloric 
 acid to 100 cubic centimeters of water. Test both solutions with red 
 and blue litmus paper. Now carefully add the acid solution to the 
 
160 INORGANIC CHEMISTRY 
 
 sodium hydroxide solution until the mixture will not change the color 
 of either the red or the blue paper. Evaporate the mixture to dryness 
 and determine whether the residue is common salt. What are the 
 characteristics of the acids? What element do they all have in com- 
 mon? What is the characteristic group of the bases? How do bases 
 and acids act on one another? What is meant by neutralization? 
 When an acid neutralizes a base what is formed? How should you de- 
 fine an acid ? A base ? A salt ? Mention three methods of forming 
 salts. 
 
 Ex. 94. What is meant by an alkali? By alkaline reaction? By 
 acid reaction? When is a substance said to be neutral? What is an 
 indicator? Try weak solutions of sodium hydroxide and hydrochloric 
 acid with phenolphthalein indicator ; with cochineal indicator ; with 
 methyl orange. Record the changes in color in each case. If red 
 cabbage is available express some of the juice and determine whether 
 it could be used as an indicator. Make a list of any substances at home 
 that are acid or alkaline in reaction. What is the reaction of your per- 
 spiration ? Of your saliva ? 
 
 Ex. 95. What is meant by a binary acid? How are these acids 
 named ? Give an example. When an element forms two acids how 
 are they named? How are the salts named? How are the bases 
 named ? What is meant by an acid salt ? Give an example. What 
 is meant by an anhydride ? Of the elements studied which are metals 
 and which non-metals? 
 
CHAPTER XVI 
 NITRIC ACID AND OXIDES OF NITROGEN 
 
 142. Chile Saltpeter. In northern Chile there are great 
 beds of the substance commonly known as Chile saltpeter, 
 or nitrate of soda. When pure, this material forms trans- 
 parent, colorless crystals which are very soluble in water. 
 
 FIG. 100. Mining nitrate of soda or Chile Saltpeter. 
 
 In nature it is mixed with common salt and earth, from 
 which it is separated by being dissolved in boiling water 
 and then allowed to crystallize as the water cools. Nearly 
 two million tons of nitrate of soda are exported from Chile 
 each year. The larger part of this is used as a fertilizer; the 
 remainder is utilized in the manufacture of nitric acid. If 
 EV. CHEM. 11 161 
 
162 
 
 INORGANIC CHEMISTRY 
 
 a particle of Chile saltpeter is placed in the flame of a Bunsen 
 burner or an alcohol lamp the flame will be colored an in- 
 tense yellow. This fact shows that this substance is a com- 
 pound of sodium (131). It is evidently a salt, but since 
 Chile saltpeter will not give the test for any of these acids 
 (88, 101, and 132), the acid with which the sodium is com- 
 bined is evidently different from any previously described. 
 If Chile saltpeter is mixed with about its own weight of sul- 
 phuric acid and the mixture is gently warmed, a vapor es- 
 capes which, when condensed to a liquid, proves to be nitric 
 acid, to which the formula HNO 3 has been assigned. Chile 
 saltpeter, then, is the sodium salt of nitric acid ; that is, it 
 is sodium nitrate (NaNOs). 
 
 143. Nitric acid is prepared commercially by heating 
 sodium nitrate with sulphuric acid, upon which the follow- 
 ing reaction takes place: 
 
 2 NaNO 3 + H 2 SO 4 -* Na 2 SO 4 + 2 HNO 3 . 
 
 The apparatus in Fig. 101 is adapted to the preparation of 
 the acid on a small scale. A is a small glass retort in which 
 
 are placed 25 grams of sodium 
 nitrate. About 15 cc. of sul- 
 phuric acid are added and the 
 mixture is gently heated. The 
 nitric acid distills over and is 
 condensed in the test tube B, 
 which is surrounded by cold 
 water, preferably ice water. 
 
 Pure nitric acid is a color- 
 less liquid about one and one 
 
 half times as heavy as water. It gives off colorless fumes 
 when exposed to the air. The concentrated nitric acid of 
 
 FIG. 101. Apparatus used in mak- 
 ing nitric acid. 
 
NITRIC ACID 163 
 
 the laboratory contains 68 per cent of HNO 3 , the rest being 
 water. In the above experiment the acid is slightly colored 
 because, when nitric acid is boiled, a small part of it is de- 
 composed according to the following equation : 
 
 2 HNO 3 -^ H 2 O + 2 NO 2 + O. 
 
 Nitrogen peroxide, NC>2, is a reddish brown gas which dis- 
 solves in the undecomposed nitric acid and colors it. The 
 same decomposition takes place when nitric acid is exposed 
 to strong light, and in consequence, the bottles in which 
 concentrated nitric acid is stored often contain a reddish 
 brown gas above the liquid, which is itself somewhat colored. 
 
 Strong nitric acid acts violently on many substances, 
 especially those of animal and vegetable origin. It causes 
 painful wounds when it comes in contact with the flesh, 
 it eats through clothing, it burns wood and dissolves metals, 
 and is, in fact, one of the most active of chemical substances. 
 Even the dilute acid stains the skin and clothing yellow, and 
 the stain cannot be removed. The greatest care should 
 be exercised in working with nitric acid. 
 
 In dilute solutions, nitric acid has many of the character- 
 istics of the other acids that have been studied. It has a 
 decidedly sour taste, and it turns blue litmus paper red. It 
 reacts with oxides, hydroxides, and carbonates to form salts, 
 as, for example : 
 
 CuO + 2 HNO 3 ->- H 2 O + Cu(NO 3 ) 2 (copper nitrate) ; 
 NaOH + HNO 3 -- H 2 O + NaNO 3 (sodium nitrate) ; 
 CaCO 3 + 2 HNO 3 ->- H 2 O + CO 2 + Ca(NO 3 ) 2 (calcium ni- 
 trate). 
 
 When nitric acid acts on a metal, a salt is formed as would 
 be expected, but no hydrogen is liberated; in this respect 
 
164 INORGANIC CHEMISTRY 
 
 it differs from sulphuric and hydrochloric acids. Instead 
 of hydrogen a gas which is one of the oxides of nitrogen is 
 given off. The reaction with copper is usually written thus : 
 
 3 Cu + 8 HN0 3 -> 3 Cu(NO 3 ) 2 + 4 H 2 O + 2 NO. 
 To explain this action of nitric acid on metals it will be 
 necessary to call attention to another property of nitric acid. 
 144. Nitric Acid an Oxidizing Agent. It was stated in 
 Chapter VI that it is very difficult to make nitrogen combine 
 with oxygen and hydrogen. It is also true that when this 
 combination is brought about as in nitric acid the compound 
 formed is very unstable. The formula for nitric acid (HN0 3 ) 
 shows that it contains f, or over three fourths, of its own 
 weight of oxygen. This oxygen is loosely held in the mole- 
 cule and is freely given off to any readily oxidizable sub- 
 stance. This explains the action of strong nitric acid on 
 animal and vegetable matter ; for the changes caused in 
 such materials by nitric acid are due to oxidation. Indeed, 
 so readily does nitric acid give up its oxygen, that a piece 
 of burning charcoal thrust beneath the surface of the strong 
 acid will continue to burn, all the oxygen for the combus- 
 tion being obtained from the acid. 
 
 When nitric acid acts on a metal, it is supposed that 
 hydrogen is first liberated, as it is with other acids, but that 
 the hydrogen is immediately oxidized to water by another 
 portion of nitric acid which gives up part of its oxygen for 
 that purpose. The first part of this reaction in the case of 
 copper may be written as follows : 
 
 3 Cu + 6 HNO 3 ->- 3 Cu(NO 3 ) 2 + 6 H. 
 The hydrogen thus evolved would then react with two more 
 molecules of nitric acid, thus : 
 
 6 H + 2 HNO 3 -^ 4 H 2 O + 2 NO. 
 
NITRIC ACID 165 
 
 It will be seen that these two steps may be combined into 
 the equation given in the preceding section. 
 
 145. Uses of Nitric Acid. Over 100,000 tons of nitric 
 acid are used annually in the industries. It is used in the 
 manufacture of nitroglycerin, which is the explosive con- 
 stituent of dynamite. It is used also in making gun cotton, 
 another explosive. It is required in the production of sul- 
 phuric acid by the chamber process (84) as well as in the 
 manufacture of dyestuffs. The dilute acid is used in the 
 refining of gold and silver and in the preparation of the 
 copper plates from which etchings are printed. 
 
 146. Aqua Regia. A mixture of nitric and hydrochloric 
 acid is called aqua regia. This expression means " royal 
 water " and it was so named because it is the only acid that 
 will dissolve the " noble metals," namely, gold and plati- 
 num. Its action depends upon the fact that the nitric acid 
 oxidizes the hydrogen of the hydrochloric acid to water, and 
 chlorine is liberated. The chlorine converts the metal 
 into the chloride, which is soluble. In olden times all 
 liquids were considered to be kinds of water. Nitric acid 
 was called aqua fortis, or " strong water." 
 
 147. Nitrates. Nitric acid is monobasic; that is, the 
 molecule contains one hydrogen atom. It forms salts with 
 all the metals* All the nitrates are soluble in water. Most 
 of them are colorless ; copper nitrate, however, is blue and 
 nickel nitrate is green. The nitrates are decomposed by 
 heat. As a general rule the metal remains as the oxide 
 while oxygen and an oxide of nitrogen are evolved, thus : 
 
 Cu(NO 3 ) 2 -* CuO + 2 NO 2 + O. 
 
 In a few cases oxygen only is given off when the nitrate is 
 heated, as for instance, in the case of sodium nitrate : 
 NaNO 3 -> NaN0 2 + O. 
 
166 
 
 INORGANIC CHEMISTRY 
 
 Owing to the ease with which they part with their oxygen, 
 the nitrates, like the acid from which they are made, are 
 good oxidizing agents. 
 
 148. Formation of Nitric Acid from the Air. Nearly 
 all the nitric acid of commerce is manufactured from Chile 
 saltpeter ; but a small amount is now made by bringing about 
 a direct combination of the nitrogen and the oxygen of the 
 atmosphere. This is effected by means of powerful electric 
 currents and is profitable only where water power makes 
 very cheap electrical energy possible. At the present time 
 the method is used to a limited extent in Norway. Most 
 of the nitric acid so produced is treated with lime to form 
 calcium nitrate, Ca(NO 3 ) 2 , which is used as a fertilizer. 
 
 149. Test for Nitric Acid and Nitrates. To test for nitric 
 acid or nitrates, dissolve the substance in water, place it in 
 
 a test tube, and add a small quantity of a 
 solution of copperas (ferrous sulphate). 
 The tube is now inclined and some sul- 
 phuric acid is poured slowly down the 
 side of the tube. The sulphuric acid, 
 being heavier than the other liquids, will 
 sink to the bottom of the tube without 
 immediately mixing with the solution. 
 If the substance being tested contains 
 nitric acid or a nitrate, a dark ring 
 (Fig. 102) will form at the point of con- 
 tact between the sulphuric acid and the 
 solution above it. 
 
 150. Nitrites and Nitrous Acid. It was shown in Sec. 
 147 that when sodium nitrate is strongly heated one third 
 of its oxygen escapes and the compound NaNO 2 is formed. 
 This compound is sodium nitrite. It is more commonly 
 
 FIG. 102. Testing 
 for the presence of 
 nitric acid. 
 
NITRIC ACID 167 
 
 prepared by melting sodium nitrate with lead. The lead 
 extracts one third of the oxygen from the nitrate to form 
 lead oxide, and sodium nitrite results, thus : 
 
 NaNO 3 + Pb ->- NaNO 2 + PbO. 
 
 The nitrite may be dissolved in water, leaving behind the 
 lead oxide, which is insoluble. Sodium nitrite is evidently 
 the salt of an acid having the formula HNO 2 , which should 
 be named nitrous acid. This acid has never been prepared 
 because it is so unstable that when it is liberated from its 
 salts it immediately decomposes into various oxides of ni- 
 trogen. Most of the metals can be made to form nitrites, but 
 none of them are of commercial importance except sodium 
 nitrite, which is used in the manufacture of dyes. It is a 
 solid that forms pale yellow crystals and is very soluble in 
 water. The nitrates can be reduced to nitrites as noted 
 above in the case of sodium nitrate. Likewise the nitrites 
 can be easily oxidized to nitrates 
 
 NaNO 2 + O -- NaNO 3 . 
 
 This reaction is of interest because nitrites are undoubtedly 
 formed as intermediate compounds during the production 
 of nitrates in nature, as will be shown in the next chapter. 
 
 151. Oxides of Nitrogen. Nitrogen forms five different 
 combinations with oxygen. These five oxides of nitrogen 
 are as follows : 
 
 Nitrous oxide N 2 O 
 
 Nitric oxide NO or N 2 2 
 
 Nitrogen trioxide N 2 0s 
 
 Nitrogen peroxide NO 2 or N 2 O* 
 
 Nitrogen pentoxide N 2 O 5 
 
168 INORGANIC CHEMISTRY 
 
 These oxides furnish one of the best examples of the law of 
 multiple proportions. 
 
 152. Nitrous Oxide. Nitrous oxide (N 2 O) is a colorless 
 gas with a slightly 'sweetish taste. When inhaled it causes 
 a slight intoxication which shows itself in the form of hys- 
 terical laughing.. For this reason Sir Humphry Davy 
 named it "laughing gas." Inhaled in larger quantities, it 
 causes unconsciousness and is, therefore, used in certain 
 minor surgical operations, particularly in extracting teeth. 
 For this purpose it is condensed to a liquid and stored in 
 steel cylinders. It is prepared by heating ammonium ni- 
 trate (NH 4 NO3), a substance which will be discussed in the 
 next chapter. The equation is as follows : 
 
 NH 4 NO 3 ->- N 2 + 2 H 2 O. 
 
 153. Nitric Oxide and Nitrogen Peroxide. Nitric oxide 
 (NO), as has been stated, is formed when nitric acid acts 
 on some metals, as zinc or copper (143, 144). It is a colorless 
 gas that is somewhat poisonous. Its most remarkable 
 property is its power to combine directly with oxygen when 
 the two are brought together. The reaction may be repre- 
 sented thus : 
 
 NO + O -> NO 2 . 
 
 The product of this reaction is nitrogen peroxide (NO 2 ), 
 which is a gas that has a reddish brown color and a disagree- 
 able smell. It is very poisonous. If dilute nitric acid is 
 poured upon some pieces of zinc or copper in a flask, the 
 upper part of the vessel is filled with the colorless nitric 
 oxide gas which, as it escapes into the air, takes up oxygen 
 and changes to the reddish brown nitrogen peroxide. The 
 latter will give up one half of its oxygen to any readily oxi- 
 
OXIDES OF NITROGEN 
 
 169 
 
 dizable substance and change back to the colorless nitric 
 oxide. This power of the oxides of nitrogen to absorb 
 oxygen from the atmosphere and transfer it to another 
 substance is utilized in the manufacture of sulphuric acid 
 by the chamber process (84). 
 
 EXERCISES 
 
 Ex.96. Examine crystals of sodium" nitrate (Chile saltpeter). Has 
 the substance the appearance of a salt? Test it in the flame. What 
 metal is present? What is the source of the sodium nitrate of com- 
 merce ? How is it purified ? For what is it used ? 
 
 Ex. 97. In an apparatus as shown in Fig. 103 place a tablespoonful 
 of sodium nitrate and sufficient sulphuric acid to cover the crystals. 
 The bottle (C) should be filled 
 with cold water or ice. Heat 
 gently and examine the liquid 
 that distills. Compare with the 
 nitric acid of the laboratory. Is 
 pure nitric acid colored? Why 
 is the acid colored in this experi- 
 ment ? Why does nitric acid be- 
 come colored when exposed to 
 light ? Write the reaction for the 
 change. Dip a splinter of wood 
 
 and a feather in nitric acid. How does nitric acid act on animal 
 and vegetable tissues ? On metals ? How does its weak solution com- 
 pare with solutions of other acids? How does it act on oxides? Hy- 
 droxides ? Carbonates ? Write the reactions. 
 
 Ex. 98. Heat nitric acid in a test tube with a piece of zinc or copper. 
 Describe the result. What is the colored gas that is formed ? Explain 
 with equations the action of nitric acid on metals. Why is nitric acid 
 said to be a good oxidizing agent ? What uses are made of nitric acid ? 
 What is the mixture of nitric and hydrochloric acids called? What 
 effect does it have on gold and platinum? What acid was formerly 
 called aqua fortis? How is nitric acid made commercially? Can 
 nitric acid be made from the nitrogen of the air ? Where is this done ? 
 
 FIG. 103. Laboratory apparatus for 
 making nitric acid. 
 
170 
 
 INORGANIC CHEMISTRY 
 
 Ex. 99. Heat a nitrate in a hard glass test tube and prove that 
 
 oxygen is evolved. Are the nitrates oxidizing agents? How can you 
 
 test for the presence of a nitrate ? Try the test with a little Chile 
 
 saltpeter. 
 
 Ex. 100. Heat sodium nitrate with lead. What compounds are 
 
 formed ? Write the reaction. What is the formula of nitrous acid ? 
 
 Has it ever been prepared in the pure state ? Why ? What change 
 
 takes place in the nitrites when oxidized ? 
 
 Ex. 101. In a test tube heat a teaspoonful of ammonium nitrate. 
 
 What is the gas which is given off? Give the formula. For what 
 
 purposes is this gas used ? Why is it 
 called " laughing gas " ? 
 
 Ex. 102. Fit a test tube with a cork 
 in which is fitted a small piece of glass 
 tubing (Fig. 104). Place a little nitric 
 acid and a piece of zinc in the test tube. 
 Insert a cork and warm the acid. Is a 
 gas evolved ? What is the color of the 
 gas in the test tube? What change 
 takes place when it comes into contact 
 
 FIG. 104. -Showing the forma- ^ the air? Explain; give reaction, 
 tion of NO 2 . In what commercial process is this 
 
 property of nitric oxide useful ? How 
 
 many oxides of nitrogen are known ? Give the names and the formu- 
 las. How do they illustrate the law of multiple proportion ? 
 
CHAPTER XVII 
 
 AMMONIA AND ITS COMPOUNDS 
 
 154. Ammonia Water. One of the most familiar sub- 
 stances is the liquid so much used in the household under the 
 name of ammonia water or spirits of hartshorn. This 
 material (also called " aqua am- 
 monia ") consists of a gas dis- 
 solved in water, which like most 
 
 other dissolved gases is almost 
 completely driven off when the 
 solution is heated. The gas may 
 be prepared for examination in 
 the apparatus shown in Fig 105. 
 The ammonia water is gently 
 warmed in the flask A and, as 
 some water may escape with the 
 gas, it is passed through the tube 
 B, which contains lumps of lime to 
 absorb the water. As the gas is 
 very soluble in water and is lighter 
 than air, it is usually collected by 
 upward displacement. 
 
 155. Ammonia. The gas prepared in the above experi- 
 ment is ammonia and is a compound having the formula 
 NH 3 . It is colorless and has an exceedingly pungent and 
 penetrating odor. When inhaled it brings tears to the eyes, 
 and in large quantities it may cause suffocation. It is 
 
 171 
 
 FIG. K)5. The production of 
 
 ammonia. 
 
172 
 
 INORGANIC CHEMISTRY 
 
 about half as heavy as air and is very soluble in water, 
 one volume of water dissolving 700 volumes of ammonia 
 gas at ordinary temperatures. Ammonia is easily condensed 
 to a liquid by pressure and cold. It will not burn in the 
 air, nor will it support the combustion of a blazing stick; 
 but in oxygen or in heated air it burns with a yellowish 
 flame. A piece of moist red litmus paper is changed to 
 blue if placed in ammonia gas. 
 
 156. Ammonia from Organic Matter. Whenever any 
 animal or vegetable substance containing nitrogen is heated 
 in a closed vessel so that the air does not have access to it, 
 
 the nitrogen passes out of the 
 compound as ammonia. This may 
 be shown by heating bits of lean 
 meat, horn, hoof, hair, peas, or 
 beans in a hard glass test tube, 
 as illustrated in Fig. 106. The 
 escape of ammonia from the tube 
 may be detected by the odor or 
 by holding a piece of moist red 
 litmus paper in the escaping gas. 
 Ammonia was formerly made by 
 the destructive distillation of the 
 horns of the deer or hart and for 
 FIG. 106. The production of that reason was termed spirits of 
 
 ammonia from organic matter. . . 
 
 hartshorn. Large quantities or 
 
 ammonia are now produced as a by-product in the manu- 
 facture of animal charcoal from dried blood or bones. It 
 should be noted that the nitrogen is not present in the 
 animal or vegetable matter as ammonia, but the ammonia 
 is formed during the decomposition of the organic matter 
 which is brought about by the heat. When animal or 
 
AMMONIA AND ITS COMPOUNDS 173 
 
 vegetable matter decays, the nitrogen present is liberated 
 in combination with hydrogen as ammonia, and, conse- 
 quently, the odor of ammonia is commonly noticed in stables, 
 and in the vicinity of cesspools and manure piles. 
 
 157. Composition of Ammonia. It is very difficult to 
 make nitrogen and hydrogen unite directly, although it 
 can be done to a limited extent by passing electric sparks 
 through a mixture of the two gases. Experiments with 
 this method of production show that one volume of nitro- 
 gen always combines with three volumes of hydrogen, and, 
 as nitrogen is fourteen times as heavy as hydrogen, the pro- 
 portion by weight is 14 parts of nitrogen to 3 parts of hy- 
 drogen. 
 
 158. Manufacture of Ammonia. Bituminous coal con- 
 tains small quantities of nitrogen (one to two per cent) and 
 some hydrogen. When the coal is heated in the manufac- 
 ture of illuminating gas, part of the nitrogen combines with 
 hydrogen to form ammonia, which passes off with the gas. 
 The illuminating gas is " washed " by being made to bubble 
 through water, and the ammonia dissolves and remains 
 behind in the so-called ammoniacal liquor. This liquor 
 is then boiled with lime, and the ammonia is driven off and 
 dissolved in pure water, forming the ammonia water of 
 commerce. This is the most common method of manu- 
 facturing ammonia; and most of the household ammonia 
 comes from this source. 
 
 159. Ammonia Combines with Water. When ammonia 
 is absorbed by water, it is believed that the act is not one 
 of mere solution, but that a chemical combination takes 
 place between the ammonia and the water, thus : 
 
 NH 3 + H 2 O -*- NH 4 OH. 
 
174 INORGANIC CHEMISTRY 
 
 The compound NH 4 OH is named ammonium hydroxide, 
 and the chemist regards ammonia water as a solution of 
 ammonium hydroxide. This compound has never been 
 separated because it is so unstable that any attempt to con- 
 centrate it and free it from water causes it to decompose 
 into ammonia and water, thus : 
 
 NH 4 OH -*- NH 3 + H 2 O. 
 
 This decomposition takes place at ordinary temperatures, 
 and the odor of the solution is due to the escaping ammonia 
 gas. Ammonia water may contain as high as 35 per cent 
 by weight of ammonia gas, which, as has been shown, can 
 be driven off by heat. A solution of this strength is lighter 
 than water, the specific gravity being about 0.9. The solu- 
 tion ordinarily sold as household ammonia usually contains 
 not more than 10 per cent of the gas. 
 
 Ammonia water is a strong alkali. It turns red litmus 
 paper blue, and when rubbed between the finger and thumb 
 has a slippery feel much like a weak solution of caustic 
 soda. It is said to be a volatile alkali because it com- 
 pletely evaporates without leaving a residue; in which re- 
 spect it differs from caustic soda, which is sometimes called 
 a " fixed alkali." The fact that it leaves no residue gives 
 ammonia water an advantage over the fixed alkalies for use 
 in cleaning glassware and clothing. It is used also to soften 
 water in the household and for other purposes where a milder 
 alkali than caustic soda is required. 
 
 160. Ammonia Water Neutralizes Acids. If aqua am- 
 monia is slowly added to a solution of hydrochloric acid, a 
 point may be reached when the solution is neutral and 
 has no effect upon litmus paper. If, now, this solution is 
 evaporated to dryness, a white substance remains in the 
 
AMMONIA AND ITS COMPOUNDS 175 
 
 dish. This substance has much of the appearance and some- 
 thing of the taste of common salt. It is the substance known 
 by the common name of sal ammoniac. Chemical analysis 
 shows that its composition may be represented by the for- 
 mula NH 4 C1, and the reaction that takes place may be ex- 
 pressed in the following equation : 
 
 NH 4 OH + HC1 ->- NH 4 C1 + H 2 O. 
 
 This reaction is much like the one between sodium hy- 
 droxide and hydrochloric acid : 
 
 NaOH + HC1 ->- NaCl + H 2 O. 
 
 Indeed, ammonia water can be used to neutralize any of 
 the acids, and in each case a compound which closely re- 
 sembles the corresponding compound formed from sodium 
 hydroxide and the same acid is formed. The following 
 compounds may be taken as examples : 
 
 
 SODIUM 
 HYDROXIDE 
 
 AMMONIUM 
 HYDROXIDE 
 
 Forms with sulphuric acid 
 
 Na 2 SO 4 
 
 (NH 4 ) 2 SO 4 
 
 Forms with nitric acid 
 
 NaNO 3 
 
 NH 4 NO 3 
 
 Forms with carbonic acid . . . 
 
 NasCOa 
 
 (NH 4 ) 2 C0 3 
 
 These compounds are known as ammonium salts. It 
 will be noted that where the symbol Na appears in the 
 formulas of the sodium salts, the group NH 4 is found in the 
 ammonium salts. A group like this, which acts as a unit 
 in chemical reactions, is sometimes called a radical. The 
 name ammonium has been given to the radical NH 4 , and 
 it is this radical which takes the place of the hydrogen of 
 the acid when the salt is formed. In reality ammonium is 
 an imaginary substance, for no one has succeeded in obtain- 
 
176 INORGANIC CHEMISTRY 
 
 ing it by itself. There is good reason to believe, however, 
 that it exists in ammonium salts and in ammonia water. 
 All ammonium salts are decomposed when treated with 
 the fixed alkalies, and ammonia is given off. When 
 ammonium chloride (sal ammoniac) is heated with cal- 
 cium hydroxide, the following reaction takes place : 
 
 Ca(OH) 2 + 2 NH 4 C1 -- CaCl 2 + 2 NH 3 + 2 H 2 O. 
 
 This reaction is quite commonly used in the preparation of 
 ammonia for study in the laboratory. 
 
 161. Ammonium chloride or sal ammoniac (NH 4 C1) is 
 prepared by passing ammonia gas from the " ammoniacal 
 liquors" (158) into a solution of hydrochloric acid. It is a 
 white, granular, or crystalline solid with a sharp, salty taste. 
 The crude salt is sometimes called muriate of ammonia. It 
 is used in certain kinds of electric batteries, in medicine, in 
 soldering fluids, and in the textile industries. When heated, 
 ammonium chloride is converted into a vapor without melt- 
 ing, and when the vapor comes in contact with a cold sur- 
 face, it condenses in the form of minute crystals. This 
 process of vaporizing and condensing a solid is called sub- 
 limation, and the solid is said to sublimate. All ammonium 
 salts are either volatile or decompose when heated. 
 
 162. Ammonium nitrate (NH 4 NO 3 ), made by passing am- 
 monia into a solution of nitric acid, is a white crystalline solid, 
 chiefly used in the preparation of nitrous oxide (152). 
 
 163. Ammonium sulphate ((NH 4 ) 2 SO 4 ) is made by passing 
 the ammonia of gas works into a solution of sulphuric acid. 
 
 2 NH 4 OH + H 2 S0 4 -- (NH 4 ) 2 SO 4 + 2 H 2 0. 
 
 It is a grayish yellow salt as produced commercially, 
 and is the most widely used of all the ammonium salts. It 
 
AMMONIA AND ITS COMPOUNDS 177 
 
 is the starting point in the production of many of the am- 
 monium compounds, and because of the fact that it is rich 
 in nitrogen it is also largely used as a fertilizer. 
 
 164. Ammonium carbonate as found in commerce is an 
 impure salt, being a mixture of acid ammonium carbonate 
 (NE^HCOs) and a related compound. When fresh it is a 
 transparent solid; but on exposure to the air it gives off 
 ammonia and turns white. Smelling salts consist of lumps 
 of ammonium carbonate covered with alcohol containing 
 a little oil of lavender or other perfume. The commercial 
 carbonate is sometimes used instead of baking powder. 
 When it is heated the acid carbonate dissociates, forming 
 water and the two gases ammonia and carbon dioxide : 
 
 NH 4 HC0 3 -> H 2 O + NH 3 + C0 2 . 
 
 It has an advantage over the baking powders in that it 
 leaves no solid residue ; but considerable experience is nec- 
 essary to handle it. successfully. It is used also in medi- 
 cine and in scouring wool, and, in the household, for soften- 
 ing water. It is sometimes called crystal ammonia or solid 
 ammonia, although the substance sold under the name of 
 solid household ammonia is too often nothing but soda with 
 a little ammonium carbonate added to give it the odor of 
 ammonia. If no residue remains when a piece of the ma- 
 terial is heated it is pure ammonium carbonate. 
 
 165. Ice Making with Ammonia. All liquids absorb heat 
 when they evaporate (8). Ammonia absorbs very large 
 quantities of heat in changing from the liquid to the gaseous 
 form, and this fact is utilized in the manufacture of artificial 
 ice (Fig. 107) . Liquid ammonia is forced into a series of pipes 
 (A) which are submerged in a large tank containing brine. 
 The ammonia vaporizes and in so doing absorbs the required 
 
 EV. CHEM. 12 
 
178 
 
 INORGANIC CHEMISTRY 
 
 heat from the brine, which is thus cooled below the freezing 
 point of pure water. If tin cans containing water are hung 
 in this brine, the water will be frozen. As fast as the am- 
 monia gas is formed in the cooling pipes it is removed by an 
 exhaust pump and is liquefied by pressure and used over and 
 over again. If there were no loss by leakage, the same 
 
 FIG. 107. The manufacture of artificial ice by the ammonia process. 
 
 amount of ammonia could be used indefinitely. When the 
 ammonia condenses, it gives off heat, which is removed 
 by running cold water over the condensing pipes (B). In 
 cold storage warehouses (Fig. 108) the cold brine is made to 
 circulate in iron pipes through the rooms to be cooled; or 
 the pipes in which the ammonia is vaporized may be placed 
 in these rooms instead of in the brine tank. 
 
 166. Occurrence of Ammonia. Although there are so 
 many interesting and important uses for ammonia and its 
 compounds, these substances are found only in very small 
 quantities in nature. Ammonia is always found in minute 
 
AMMONIA AND ITS COMPOUNDS 
 
 179 
 
 traces in the atmosphere, because it is one of the products of 
 the decay of plants and animals. It is dissolved in rain 
 water and carried in- 
 to the soil, where it 
 is changed first into 
 ammonium com- 
 pounds and finally 
 into nitric acid. It 
 is found also in mere 
 traces in most of the 
 natural waters. Its 
 presence in water in 
 larger quantities is 
 an indication that 
 the water is contam- 
 inated by sewage. 
 Owing to the insta- 
 bility of ammonium compounds and the ease with which 
 they are changed to nitrates, there are no large deposits of 
 ammonium salts as there are of nitrate of soda (142). 
 
 167. Test for Ammonium Salts. These salts are readily 
 detected, since ammonia is evolved when they are treated 
 with a dilute solution of caustic alkali, such as sodium 
 hydroxide. The ammonia may be recognized by its odor 
 or by the fact that it turns moist red litmus paper blue. 
 
 168. The Nitrogen Cycle. Although the worker in the 
 laboratory has difficulty in making nitrogen unite with other 
 elements, nature evidently has methods of bringing about 
 this union. Small quantities of nitric acid are formed dur- 
 ing electric storms, and this is carried into the soil by means 
 of the rains. The combined nitrogen added to the soil in 
 this way amounts to only three to eight pounds a year for 
 
 FIG. 108. Room in a cold storage warehouse. 
 
180 
 
 INORGANIC CHEMISTRY 
 
 each acre of ground. The principal factors in causing 
 the formation of nitrogen compounds are the bacteria 
 that live in the soil. An ounce of a good garden soil is said 
 to contain at least one hundred fifty millions of bacteria. 
 These are very small one-celled plants that can be 
 
 FIG. 109. The nitrogen cycle in nature. 
 
 seen only with the strongest microscope. Some of these 
 bacteria have the power of bringing about the union of nitro- 
 gen, oxygen, and water to form nitric acid, which acid 
 (as well as that in the rain water) usually unites with the 
 calcium carbonate in the soil to form calcium nitrate, thus : 
 
 2 HNO 3 + CaCO 3 ->- Ca(NO 3 ) 2 + H 2 O + CO 2 . 
 All plants need nitrogen in order to grow, and most of 
 
AMMONIA AND ITS COMPOUNDS 181 
 
 them obtain their nitrogen from the soil in the form of ni- 
 trates. The nitrogen compounds formed by these bacteria, 
 therefore, are used by the higher plants. Some plants, 
 however, have another way of obtaining the nitrogen they 
 need. They belong to the family of plants known as legumes, 
 which includes the clovers, alfalfa, peas, and beans. On 
 the roots of these plants are found numbers of nodules or 
 tubercles, which consist largely of masses of bacteria. These 
 bacteria, while living on the roots of the legumes, have the 
 power of causing the nitrogen of the air to form a chemical 
 combination which the plant can utilize. Clovers and other 
 legumes are frequently grown by farmers as a means of 
 increasing the nitrogen compounds in the soil. This power 
 of causing free nitrogen to enter into chemical combination 
 is called fixation of nitrogen. Since animals get all the 
 nitrogen in their bodies from the foods consumed, it follows 
 that the bacteria are either directly or indirectly responsible 
 for nearly all the nitrogen compounds found in nature. 
 
 Bacteria are responsible also for other changes in nitrogen 
 compounds. When the plants or animals die, their bodies 
 decay, as do also the waste products of the animal body. 
 The decay is caused by other kinds of bacteria and results 
 in the breaking down of the complex nitrogen compounds 
 found in plants and animals. Sometimes the nitrogen is 
 liberated in the form of pure nitrogen or of ammonia and 
 finds its way into the atmosphere. This change is called 
 denitrification. If the decay takes place in the soil it is 
 more likely to result .in the formation of nitrates, which 
 can again be utilized by growing plants. This change from 
 complex nitrogen compounds to nitric acid and nitrates is 
 termed nitrification. The change is caused by at least 
 three kinds of bacteria and takes place in three steps: 
 
182 . INORGANIC CHEMISTRY 
 
 (1) the formation of ammonium compounds from the or- 
 ganic nitrogen compounds; (2) the change of ammonium 
 compounds into nitrous acid (HNO 2 ), which unites with a 
 base in the soil to form a nitrite probably calcium nitrite, 
 Ca(NOfe)2; (3) the oxidation of the nitrite to a nitrate, 
 
 Ca(N0 2 ) 2 + 20^ Ca(N0 3 ) 2 . 
 
 It will thus be observed that nitrogen passes through a 
 cycle (Fig. 109) much like that described for carbon, 
 although the amount of nitrogen involved in these changes 
 is much smaller than the carbon of the carbon cycle. 
 
 169. Another Method of Fixing Nitrogen. When cal- 
 cium carbide (CaC 2 ) is strongly heated in a current of nitro- 
 gen, a substance is formed which has the formula CaCN 2 : 
 
 CaC 2 + N 2 ->- CaCN 2 + C. 
 
 This new substance is variously named, nitro-lime, lime 
 nitrogen, and calcium cyanamide. It is made on a commercial 
 scale by means of the electric furnace. It is a hard, gray- 
 black mass resembling coke and, as the formula shows, is 
 rich in nitrogen. It is used as a fertilizer, but before the 
 nitrogen can be utilized by plants it must be oxidized to 
 nitrate, a process which readily takes place in the soil (624). 
 
 EXERCISES 
 
 Ex. 103. Perform the experiment described in paragraph 154. 
 Why is the gas collected by upward displacement ? How does the gas 
 affect the eyes and nose ? Test the gas with a piece of red litmus paper. 
 Will the gas burn or support combustion ? Does it dissolve in water ? 
 Can it be condensed to a liquid ? What is its name and formula ? 
 
 Ex. 104. Heat bits of meat, hair, horn, and some beans in hard 
 glass test tubes. Test the vapor from the tubes with moist red litmus 
 paper. What is the source of the ammonia ? Was the nitrogen present 
 in the above materials as ammonia ? Is ammonia formed by the decay 
 
AMMONIA AND ITS COMPOUNDS 183 
 
 of animal and vegetable matter? What is the composition by weight 
 of ammonia ? How is the ammonia water of commerce manufactured ? 
 Ex. 105. Examine a sample of ammonia water from home. How 
 does it feel when rubbed between the fingers ? What is the odor ? 
 The reaction with litmus paper ? Is it an alkali ? Why is it called a 
 volatile alkali? Is its volatility any advantage in cleaning? Does 
 ammonia gas merely dissolve in water or form a chemical compound 
 with it ? Write the reaction. Is this compound stable ? Why does 
 ammonia water always give the odor of ammonia gas? How much 
 ammonia does the ordinary household ammonia water contain ? 
 
 Ex. 106. To a dilute solution of hydrochloric acid, add dilute 
 ammonia water until the mixture is neutral or faintly alkaline. Evap- 
 orate to dryness. What remains? Give the formula. Write re- 
 action between ammonium hydroxide and hydrochloric acid. Will 
 ammonia water form salts with other acids? Compare with sodium 
 salts of the same acids. What is a radical? What is the name of 
 the radical NH 4 ? Does this radical exist ? Mix a little ammonium 
 chloride with lime and heat in a test tube. Try the same experiment 
 with ammonium sulphate and sodium hydroxide. How do ammonium 
 salts act when heated with the fixed alkalies ? 
 
 Ex. 107. Place a teaspoonful of ammonium chloride in a long test 
 tube. Hold the test tube in an inclined position and heat. What 
 happens to the, chloride ? Does it condense again at the top of the 
 test tube? What is meant by sublimation? What are the commer- 
 cial uses of ammonium chloride? 
 
 Ex. 108. Examine some ammonium sulphate. How is it made 
 commercially? What are its uses? Does ammonia combine with 
 carbonic acid? Examine crystals of crude ammonium carbonate. 
 Why is it called sal volatile? What happens to it when heated? 
 Write the reaction. What uses are made of it? f Examine a commer- 
 cial sample of " solid household ammonia " and determine whether 
 it contains soda. How should you test for ammonium salts ? 
 
 Ex. 109. Explain by help of a diagram how liquid ammonia is 
 utilized in ice making. 
 
 Ex. 110. Where and to what extent is ammonia found in nature ? 
 Why is it not more abundant ? Discuss the cycle of nitrogen in nature. 
 What is formed when calcium carbide is strongly heated in a current of 
 n : trogen ? What use is made of calcium cyanamide ? 
 
CHAPTER XVIII 
 
 PHOSPHORUS, PHOSPHORIC ACID, ARSENIC 
 
 170. PHOSPHORUS has already been used in the experi- 
 ments with oxygen (37). It is an element that is never found 
 in the free state, and is usually combined with calcium and 
 oxygen in the form of calcium phosphate. 
 
 Phosphorus is slightly yellow and translucent. It can be 
 cut like wax at ordinary temperatures, and it melts at 44 C. 
 It is insoluble in water but dissolves freely in carbon bisul- 
 phide. It is very poisonous; and in fac- 
 tories where phosphorus is made, the work- 
 men are frequently poisoned by it. 
 
 In contact with the air phosphorus gives 
 off fumes which emit light visible in a dark 
 room. This phenomenon suggested the name 
 phosphorus, which is derived from the Greek 
 and means " light bearer." Although other 
 substances act in the same way, this 
 property was first observed in connection 
 FIG. no. sticks of with phosphorus and the phenomenon is, 
 
 therefore, called phosphor 'esence. 
 
 The streak of light left by a match when rubbed on any 
 surface in a dark room is due to the phosphorus in the match. 
 Phosphorus takes fire when rubbed or cut ; hence it must 
 be handled with great care. It is kept under water, and 
 should be cut under water and never held in the hand, since 
 the heat of the hand is sufficient to ignite it. The burns 
 
 184 
 
PHOSPHORUS 185 
 
 caused by phosphorus are very difficult to heal. In a finely 
 divided state phosphorus ignites spontaneously. If a little 
 phosphorus is dissolved in carbon bisulphide and the solu- 
 tion poured on a piece of filter paper, the phosphorus will 
 take fire as soon as the carbon bisulphide has evaporated. 
 
 171. Red Phosphorus. When ordinary phosphorus is 
 exposed to the light for a long time, it becomes opaque and 
 darker in color, and finally dark red. The change to red 
 phosphorus can be hastened if the yellow variety is heated 
 in a sealed tube to about 250 C. Red phosphorus is strik- 
 ingly different in its behavior from the yellow. It is not 
 very active. It does not change in the air, and must be 
 heated to a comparatively high temperature before it will 
 combine with oxygen. It is insoluble in carbon bisulphide 
 and is not poisonous. Red phosphorus may be changed back 
 to the ordinary variety by heating it to 300 C. in an atmos- 
 phere of nitrogen. 
 
 172. Preparation of Phosphorus. The ash produced by 
 burning bones is the source of most of the phosphorus of 
 commerce. Phosphorus cannot be readily prepared in the 
 laboratory. Commercially it is made by heating bone ash 
 with sand and charcoal. A complicated reaction takes 
 place during which phosphorus is liberated as the element and 
 escapes from the retort as a vapor which is condensed under 
 water. It is purified by redistillation and cast into sticks 
 under water. These sticks are usually about half an inch 
 in diameter and 7.5 inches long. 
 
 173. Matches. The principal use of phosphorus is in 
 the manufacture of matches. The ordinary parlor matches 
 are made by dipping small pieces of wood into melted par- 
 affin and then into a mixture of phosphorus, manganese 
 dioxide, and glue. By rubbing such matches on a rough 
 
186 INORGANIC CHEMISTRY 
 
 surface enough heat is generated by the friction to cause 
 the phosphorus to ignite. This sets fire to the paraffin, 
 which in turn kindles the wood. The manufacture of these 
 matches is prohibited in some countries because they are so 
 liable to take fire and because the workmen in the factories 
 are so often poisoned by the phosphorus. Safety matches, 
 or Swedish matches, contain no yellow phosphorus. The 
 head of this kind is a mixture of potassium chlorate, anti- 
 mony sulphide, and glue. The side of the box is coated with 
 red phosphorus, glue, and powdered glass. When the head 
 of the match is drawn over this prepared surface, a little of 
 the phosphorus is torn off, catches fire, and ignites the match. 
 Safety matches cannot easily be ignited except on the pre- 
 pared surface, although they can be lighted by drawing 
 them rapidly over glass. 
 
 174. Phosphorus burns with the formation of a dense 
 white cloud, which condenses into a white, snowlike solid. 
 Either variety of phosphorus burns readily, but the com- 
 bustion of the yellow is much more violent. The product of 
 combustion, which is the same in either case, has the com- 
 position P2O 5 and is called phosphorus pentoxide. This 
 oxide of phosphorus is very deliquescent, quickly drawing 
 moisture from the air. It combines vigorously with water, 
 with a hissing sound. It is often used in the laboratory to 
 dry gases. 
 
 175. Phosphoric Acid. When phosphorus pentoxide is 
 added to hot water, the solution has a sour taste and turns 
 blue litmus paper red. This is due to the fact that the phos- 
 phorus pentoxide has combined with the water to form phos- 
 phoric acid, H 3 PO4 : 
 
 P 2 O 5 + 3 H 2 O ->- 2 H 3 PO 4 . 
 
PHOSPHORUS AND PHOSPHORIC ACID 187 
 
 Phosphoric acid, also called orthophosphoric acid, when 
 pure is a white solid that is very soluble in water. The 
 commercial article contains a little water and is a thick, 
 sirupy liquid somewhat resembling pure sulphuric acid in 
 appearance and weight. While it can be prepared as in- 
 dicated above, it is usually made by the common method for 
 preparing acids ; namely, by the action of sulphuric acid on 
 one of the salts of phosphoric acid. The salt ordinarily 
 used is calcium phosphate, Ca 3 (PO4) 2 , which is a constituent 
 of bones and of the phosphate rocks. 
 
 Ca 3 (PO 4 ) 2 + 3 H 2 SO 4 ->- 3 CaSO 4 + 2 H 3 PO 4 . 
 
 The calcium sulphate is insoluble and is filtered off. 
 
 176. Salts of Phosphoric Acid. The formula for phos- 
 phoric acid, H 3 PO 4 , shows that each molecule contains three 
 hydrogen atoms. From what was said about normal and 
 acid salts (140) it is evident that one, two, or three of these 
 hydrogen atoms might be replaced by a metal. There are, 
 therefore, three possible phosphates of each metal. The 
 three phosphates of sodium, for example, with their formulas 
 and chemical names are as follows : 
 
 Mono-sodium phosphate, NaH 2 PO ; 
 
 Di-sodium phosphate, Na 2 HPO 4 ; 
 
 Normal or Tri-sodium phosphate, Na 3 PO 4 . 
 
 The second salt, di-sodium phosphate, is the most common, 
 and is the one used in the laboratory and in medicine. It 
 is usually known simply as sodium phosphate. It crystal- 
 lizes with twelve molecules of water of crystallization : 
 
 Na^HPO, - 12 H 2 O. 
 
 In the case of a metal like calcium, which has a valence of 
 two, the manner in which the base and acid combine to form 
 
188 
 
 INORGANIC CHEMISTRY 
 
 the salts is not so apparent. For the bivalent calcium just 
 to neutralize phosphoric acid with its three hydrogen atoms, 
 it must be assumed that three atoms of calcium react with 
 two molecules of phosphoric acid, thus : 
 
 3 Ca + 2 H 3 PO 4 ->- Ca 3 (PO 4 ) 2 + 6 H. 
 The three calcium salts and their formulas are, 
 
 Monocalcium phosphate, CaH 4 (PO 4 ) 2 , 
 Dicalcium phosphate, Ca2H 2 (PO 4 )2, 
 Normal or Tricalcium phosphate, Ca 3 (PO 4 ) 2 . 
 
 177. Occurrence of Phosphorus. The bulk of all the 
 phosphorus found in nature exists in the form of tricalcium 
 
 phosphate. The bones 
 of animals are 80 per 
 cent tricalcium phos- 
 phate. It occurs in 
 large deposits in a 
 mineral known as apa- 
 tite, and in a more 
 impure form it is 
 found in the phosphate 
 rocks of Florida, Ten- 
 nessee, South Caro- 
 lina, Arkansas, Ken- 
 tucky, Idaho, Utah, 
 Wyoming, and Montana. The rocks from which the 
 soils were formed contained some tricalcium phosphate 
 also, and consequently it is present in small quantities in 
 all soils. 
 
 Phosphorus is found in plant and animal tissue. The 
 plants derive it from the phosphate in the soil and build 
 
 FIG. 111. Hydraulic mining of phosphate rock 
 in Florida. 
 
PHOSPHORUS 189' 
 
 it up into complex organic compounds. Animals eat the 
 plants and get their phosphorus in that way. When plant 
 residues and the animal bodies and manures decay, the 
 phosphorus is returned to the soil, where it is again oxidized 
 to phosphates ; thus it completes the phosphorus cycle. 
 
 Some of the iron ores contain phosphorus, which is ob- 
 jectionable in the manufacture of steel. To remove it 
 lime is added, and the phosphorus remains with the calcium 
 in the slag, which is ground to a fine powder and sold as 
 basic slag, Thomas phosphate, or odorless phosphate (236). 
 
 178. Fertilizers. Phosphorus in the form of a phosphate 
 is absolutely essential to plant growth. Very few soils 
 contain sufficient phosphorus for a maximum crop, and as a 
 large part of the phosphorus in the plant is stored in the 
 seeds, which are removed from the land, the amount of 
 phosphorus in the soil is being constantly decreased. A 
 part of the phosphorus is returned to the soil in animal 
 manures, but never a sufficient amount to restore that re- 
 moved by the crops. To maintain a satisfactory crop 
 yield, the farmer must add some form of calcium phosphate 
 to the soil. This is sometimes done by the use of bones, 
 which are ground to a fine powder (bone meal), or by the 
 use of basic slag. The phosphate rocks are also ground 
 to a fine powder called floats and applied directly to the 
 land or mixed with the animal manures. Tricalcium phos- 
 phate, however, is very insoluble in water, and to make 
 it more available it is customary to treat it with sufficient 
 sulphuric acid to bring about the following reaction: 
 
 Ca 3 (PO 4 ) 2 + 2 H 2 SO 4 -*- 2 CaSO 4 + CaH 4 (PO 4 ) 2 . 
 
 Monocalcium phosphate, CaH 4 (PO 4 ) 2 , is soluble in water 
 and can, therefore, be much better distributed in the soil 
 
190 INORGANIC CHEMISTRY 
 
 than the insoluble natural phosphate. The calcium sul- 
 phate (gypsum) and monocalcium phosphate produced by 
 the above reaction are not separated, but the mixture is 
 dried and ground, and sold under the various names of 
 superphosphate, acid phosphate, or acidulated rock (610). 
 
 179. The term phosphoric acid as used in fertilizers 
 does not mean H 3 PO 4 but the anhydride P 2 O 5 (141). For- 
 merly calcium phosphate was considered to be a combina- 
 tion of lime and phosphoric anhydride. The formula was 
 written 3 CaO P<)S. The name phosphoric acid was then 
 given to the oxide P2O5, and although this use of the name 
 has been discontinued by chemists, it has persisted in trade. 
 When a fertilizer, then, is said to contain 14 per cent of 
 phosphoric acid, it means that it contains calcium phosphate 
 equivalent to 14 per cent of P2C>5. 
 
 180. Test for Phosphoric Acid or Phosphate. If the 
 phosphate is insoluble in water, it should be dissolved in 
 dilute nitric acid. To the solution to be tested nitric acid 
 should be added unless it was used to dissolve the substance. 
 Add about 2 cc. of the ammonium molybdate test solution 
 and warm gently. If phosphoric acid is present, a yellow 
 precipitate will be formed. Since the composition of the pre- 
 cipitate depends upon the temperature, however, no formula 
 can be assigned to it. 
 
 181. Arsenic. The name arsenic, which is sometimes 
 used for the white material sold in the drug stores, should 
 be confined to the element arsenic, which is a steel gray, 
 brittle solid, with a metallic appearance. It is found 
 sparingly in the uncombined state, but its compounds with 
 sulphur and with the metals are very abundant. It is not 
 in common use, but it is sometimes added to lead as a 
 hardener in the manufacture of shot. 
 
ARSENIC 191 
 
 182, White Arsenic. When arsenic, or any of its ores, 
 is burned, the arsenic is converted into the oxide : 
 
 2 As + 3 O -*- AssOs. 
 
 Arsenic trioxide (As2O 3 ) is the substance ordinarily called 
 arsenic, or white arsenic. It is found in trade as a white 
 powder which has no odor and a faintly sweet taste. It 
 is a deadly poison and should be handled with great care. 
 It is slightly soluble in water and the solution is poisonous 
 to both plants and animals. Arsenic compounds are used al- 
 most entirely for the destruction of vermin and insect pests. 
 
 183. Arsenites. When arsenic trioxide is boiled with so- 
 dium hydroxide, the following reaction takes place : 
 
 AsaOs + 6 NaOH ->- 2 Na 3 As0 3 + 3 H 2 O. 
 Sodium arsenite, NaaAsOs, is soluble in water and is used as 
 a basis for the preparation of other compounds of arsenic. 
 As it is very soluble it is more intensely poisonous than 
 white arsenic. The corresponding calcium salt, calcium 
 arsenite, Ca 3 (AsO3) 2 , is insoluble and is often used as a spray 
 to kill potato bugs and other insects. It is made by adding a 
 solution of sodium arsenite to calcium hydroxide (slaked lime) . 
 Sodium arsenite upon oxidation is changed to the arse- 
 nate, Na 3 AsO 4 . Evidently this compound is the sodium 
 salt of arsenic acid, H 3 AsO4, while sodium arsenite is the 
 salt of arsenious acid, H 3 AsO 3 . Neither pf these acids is 
 of any importance ; but several of their salts are in common 
 use. The arsenites and arsenates of all metals except sodium 
 and potassium are insoluble. Some of them will be studied 
 in connection with the metals from which they are formed. 
 
 EXERCISES 
 
 Ex. 111. What is the appearance of ordinary phosphorus? Is it 
 ever found in nature in the elemental condition? Is it soluble in 
 
192 
 
 INORGANIC CHEMISTRY 
 
 water? What effect does it have upon the men who work with it? 
 What happens to phosphorus when exposed to the ah*? Why was 
 it named phosphorus? Why is it stored under water? When or- 
 dinary phosphorus is heated in a sealed tube what change takes place ? 
 Is the red phosphorus very active? In what other respects does it 
 differ from ordinary phosphorus? How is phosphorus prepared com- 
 mercially ? How are the safety matches made ? 
 
 (Note. All experiments with yellow phosphorus should be per- 
 formed by the teacher.) 
 
 Ex. 112. Burn a little red phosphorus in a dry wide-mouth bottle 
 (Fig. 112). What is formed? What is the composition of the white 
 fumes ? The name ? Pour a little water into 
 the bottle and shake. Does the white material 
 dissolve? Test solution with blue litmus 
 paper. Write equation for action of phos- 
 phorus pentoxide on water. Examine the phos- 
 phoric acid of the laboratory. How is it pre- 
 pared commercially ? How many atoms of hy- 
 drogen in the molecule? How many sodium 
 phosphates are possible ? Names and formulas ? 
 Ex. 113. Dissolve a little sodium phos- 
 phate in water. Heat and add a few drops of 
 the ammonium molybdate reagent of the lab- 
 oratory. What happens ? This is the test for 
 a phosphate. Mix some rock phosphate with 
 water. Filter and test the filtrate for phos- 
 phates. Moisten another sample of the rock 
 phosphate with sulphuric acid. After ten 
 minutes add water, stir, and filter. Test this filtrate for phosphates. 
 Have you any evidence that the sulphuric acid made the rock phos- 
 phate soluble ? Why is rock phosphate treated with sulphuric acid 
 in making fertilizers ? What is meant by acid phosphate, or acidulated 
 rock? Discuss the occurrence of phosphorus in nature. What is 
 meant by the term phosphoric acid as used in the fertilizer trade ? 
 
 Ex. 114. What is the composition of the substance known as white 
 arsenic? What is its chemical name? What is formed when it is 
 boiled with sodium hydroxide? What is formed when the arsenites 
 are oxidized ? What practical use is made of calcium arsenite ? 
 
 FIG. 112. Burning 
 phosphorus in bottle. 
 
CHAPTER XIX 
 SAND, SILICON, BORAX 
 
 184. Sand. The term sand is sometimes used to desig- 
 nate any gritty material consisting of small angular frag- 
 ments of rocks or minerals. In a more restricted sense 
 sand consists of small particles of more or 
 less pure silica. In its pure form silica 
 crystallizes in beautiful six-sided prisms 
 and is called quartz, or, sometimes, rock 
 crystal. These crystals are often so clear 
 that they can be used for making spectacle 
 lenses or as substitutes for the diamond. 
 Sea sand is often almost exclusively frag- 
 ments of quartz. White sands are prac- 
 tically pure silica, while in the yellow 
 sands, or the variously tinted sandstones, 
 the silica is colored by iron oxide or some 
 other metallic oxide. 
 
 Chemically, silica is an oxide of the 
 element silicon and is called silicon dioxide,, 
 which has the composition represented by 
 the formula SiO 2 . Quartz is the most common of minerals 
 and constitutes 18 per cent of the crust of the earth. In the 
 form of the mineral, quartzite, it forms many mountains, 
 and the sandstones also consist almost entirely of silica. 
 Several of the valuable stones and precious gems, as onyx, 
 or carnelian, agate, jasper, flint, amethyst, rhinestone, and 
 EV. CHBM; 13 193 
 
 FIG. 113. Quartz 
 crystal. 
 
194 INORGANIC CHEMISTRY 
 
 opal, consist of silicon dioxide. Infusorial earth consists of 
 the skeletons of minute aquatic organisms and is nearly 
 pure silicon dioxide. It is employed as a scouring and 
 polishing material, and is used to absorb nitroglycerin in 
 the manufacture of dynamite. Silica also occurs in the 
 leaves and stalks of grasses, cereals, and bamboos and other 
 canes. The plant known as equisetum (horsetail) contains 
 so much silica that it is often used for scouring and is called 
 scouring rush. Silica constitutes about 40 per cent of the 
 ash of the feathers of birds and is found in the hair of animals. 
 
 185. Silicon. The element silicon is never found in the 
 free state, although, next to oxygen, it is the most abundant 
 element. The solid crust of the earth contains 28 per cent 
 of silicon ; for it is found in all varieties of granite, sandstone, 
 gneiss, clay, and shale. It may be prepared by heating 
 the oxide (quartz or white sand) with powdered magnesium. 
 
 SiO 2 + 2 Mg ->- Si + 2 MgO. 
 
 Silicon made in this way is an amorphous brown powder 
 insoluble in water and in all the common acids. It is used 
 to some extent in the steel industry as a reducing agent. 
 When heated to a high temperature, it burns and forms 
 silicon dioxide (SiO 2 ). 
 
 186. Water Glass. When clean white sand is melted 
 with sodium carbonate, carbon dioxide escapes, and a com- 
 pound remains which is called sodium silicate (NaaSiOs). 
 
 NagCOa + SiO 2 *- Na*SiO 3 + CO 2 . 
 
 Sodium silicate is soluble in water and is known as water 
 glass. In commerce it is found as a thick, sirupy solution. 
 It is employed in fireproofing cloth and wood, as a cement, 
 as a " filler " in laundry soaps (462), and in preserving eggs. 
 For the latter purpose the commercial solution is diluted with 
 
SAND AND SILICON 
 
 195 
 
 nine times its own volume of water, and the eggs are kept 
 immersed in the liquid until used. If the eggs are perfectly 
 fresh at the beginning, they can be preserved for several 
 months in this solution. 
 
 187. Silicic Acid. If sulphuric or hydrochloric acid is 
 added to a concentrated solution of water glass, silicic acid 
 separates in the form of a jelly, thus : 
 
 Na 2 SiO 3 + H 2 SO 4 ->- Na 2 SO 4 + H 2 SiO 3 . 
 Silicic acid has never been prepared in a pure state because 
 when evaporated to dryness it decomposes, and pure white 
 sand (silicon dioxide) remains in the dish : 
 
 H 2 SiO 3 -^H 2 O + SiO 2 . 
 
 188. Glass. When limestone is heated at a high tem- 
 perature with sand, calcium silicate is formed and carbon 
 dioxide is given off: 
 
 CaCO 3 + SiO 2 -- CaSiO 3 + CO 2 . 
 
 If both calcium and sodium carbonates are melted with sand, 
 the product is a mixture of sodium and calcium silicates 
 which, upon cooling, 
 forms ordinary win- 
 dow glass. The in- 
 gredients are used 
 in about the fol- 
 lowing proportions : 
 clean sand, 150 
 pounds ; soda, 50 
 pounds ; limestone, 
 25 pounds. Window 
 glass is made by 
 blowing a lump of the glass into a hollow cylinder, which 
 is then cut lengthwise and allowed to spread open upon a 
 
 FIG. 114. Glass blowing. 
 
196 INORGANIC CHEMISTRY 
 
 flat surface. Plate glass has the same composition but is 
 made by pouring the molten glass upon a large table and 
 rolling it with a hot iron roller, and subsequently grinding 
 and polishing it. 
 
 When potash is used in place of the soda, a very hard 
 glass is formed known as Bohemian glass, which is much 
 used for chemical apparatus. Lamp chimneys, lenses, and 
 cut glass are made of flint glass. This is a silicate of lead 
 and potassium, made by melting potassium carbonate and 
 lead oxide with sand. Glass is colored by adding different 
 substances which dissolve in the molten mass. The green 
 color of common glass bottles is due to the iron in the impure 
 sand used; copper and cobalt produce different shades of 
 blue; manganese dioxide gives a pink or violet color, and 
 certain copper compounds and gold make the glass ruby red. 
 
 189. Natural Silicates. The salts of silicic acid are called 
 silicates. They make up a large part of the earth's crust, the 
 silicates of aluminum, calcium, potassium, sodium, mag- 
 nesium, and iron being the most abundant. Nearly all 
 the common rocks, with the exception of limestone and 
 dolomite, are silicates, as well as many of the minerals and 
 a few of the precious gems. Mica, clay, slate, asbestos, 
 soapstone, feldspar, meerschaum, garnet, emerald, topaz, 
 and beryl are all silicates. Some of these silicates are salts 
 of the silicic acid (H 2 SiO 3 ) mentioned above, but many of 
 them are evidently salts of acids which are very much more 
 complex. Silicates are known, for instance, which corre- 
 spond to acids having the formulas H^SiO^ HcSi2O7, H 4 Si 3 O 8 , 
 and many others. None of these more complex acids have 
 ever been isolated, but their salts are well known, and some 
 of them will be described when the metals from which they 
 are formed are studied. 
 
SAND AND SILICON 197 
 
 When the silicic acid contains four or more hydrogen 
 atoms, it is quite common to find that two or more metals 
 have replaced the hydrogen atoms to form a mixed salt. 
 For example, feldspar is a silicate of potassium and alumi- 
 num (KAlSi 3 O 8 ) ; and mica is another silicate of potassium 
 and aluminum (KAlSi0 4 ). 
 
 190. Decomposing the Silicate. All the silicates, with 
 the exception of those of sodium and potassium, are in- 
 soluble in water. Most of them are also quite insoluble or 
 very slightly soluble in acids. If an insoluble silicate is 
 mixed with sodium carbonate and the mixture is heated, 
 it melts or fuses, and sodium silicate and an insoluble car- 
 bonate are formed ; that is, the sodium and the other metals 
 change places. 
 
 CaSiO 3 + N^COs -- CaC0 3 + Na^SiOs. 
 
 The sodium silicate can be dissolved in hot water, leaving 
 the metals of the original silicate behind as carbonates, 
 which can be dissolved in hydrochloric acid. This is the 
 method used in the laboratory to decompose the silicates 
 for purposes of analysis. 
 
 191. Test for Silica or Silicates. If the material is in- 
 soluble in water or acids, it is fused with sodium carbonate 
 and then treated with boiling water as deacribed in the pre- 
 vious paragraph (190). Hydrochloric acid is then added 
 to the hot water solution with the result that the gelatinous 
 silicic acid separates; or the acidulated solution may be 
 evaporated to dryness, upon which a white residue of silica 
 (SiO 2 ) remains which cannot be dissolved in water and hydro- 
 chloric acid. No substance but silicic acid behaves in this 
 way when treated with hydrochloric acid. 
 
198 INORGANIC CHEMISTRY 
 
 192. Carborundum. When quartz sand is strongly heated 
 with coke in an electric furnace, the silicon and carbon 
 combine to form a compound which is silicon carbide : 
 
 SiO 2 + 3 C ->- SiC + 2 CO. 
 
 Silicon carbide, SiC, is the substance known under the trade 
 name of carborundum. It is used as a substitute for emery 
 in hones and whetstones, in grinding wheels, and in polish- 
 ing papers and powders. It is much harder than emery, 
 being almost as hard as the diamond. 
 
 193. Borax. The familiar substance borax is found in 
 California and in Tibet, but most of the commercial borax 
 is prepared from a mineral known as calcium borate. Borax 
 is sodium borate, a compound of sodium, oxygen, and the 
 element boron (Na 2 B 4 O 7 - 10 H 2 O). It is a white crystallized 
 solid, containing ten molecules of water of crystallization. 
 It effloresces in the air. It is employed as a cleansing ma- 
 terial in the laundry and is used in some soaps. It is also 
 used as a preservative in certain canned products, but such 
 use is objectionable. It is used in soldering and welding, 
 since it dissolves any oxide that may be on the metal and thus 
 keeps the surface clean, a condition that is absolutely neces- 
 sary in order that the solder may adhere. 
 
 194. Boric Acid. If dilute sulphuric acid is added to 
 borax, the following reaction takes place : 
 
 H 2 SO 4 + 5 H 2 O ->- NaaSO 4 + 4 H 3 BO 3 . 
 
 Boric acid, HsBOs, forms white scaly crystals that feel greasy 
 to the touch. It dissolves slightly in cold water, but is 
 readily soluble in hot water and in alcohol. Boric acid 
 is sometimes known commercially as boracic acid. It is used 
 as an antiseptic in medicine and surgery. The solution in 
 
BORAX 199 
 
 water is used as an eye wash. It is also illegally used as a 
 preservative in meats, fish, milk, butter, and other food 
 products. 
 
 195. Boron. The element boron is never found in nature 
 in the free state. It is a greenish brown, amorphous powder, 
 without taste or odor. As it has no common uses, it is not 
 prepared in large quantities. Borax and boric acid are the 
 only important compounds of boron. 
 
 196. Test for Boric Acid. To test for boric acid warm 
 the substance with sulphuric acid and alcohol and ignite 
 the alcohol vapor. If boric acid or borax is present, the 
 flame will have a green color. If a sample of food is to be 
 tested for boric acid, it must first be moistened with a strong 
 solution of sodium hydroxide (NaOH), and burned. The 
 ash is then tested for boric acid as above. 
 
 EXERCISES 
 
 Ex. 115. What is the composition of quartz and ordinary sand? 
 What is the chemical name and formula for quartz, or silica ? Discuss 
 the occurrence of silica in nature. What valuable gems are composed 
 of silicon dioxide ? What is infusorial earth ? What uses are made of 
 it? If possible collect some specimens of equisetum and examine 
 them. Burn some of them and note the amount of sand in the ash. 
 How is the element silicon prepared? How widely is the element 
 distributed in nature? What use is made of it commercially? 
 
 Ex. 116. Place a teaspoonful of commercial water glass in an evap- 
 orating dish and dilute it with about an ounce of water. Add some hy- 
 drochloric acid and note the gelatinous precipitate. What is this ma- 
 terial? Write the reaction between the acid and the water glass. 
 Evaporate the material in the dish to dryness and heat the dish cau- 
 tiously over the bare flame. When cool add water and examine the 
 residue. What is this substance ? What reaction took place when the 
 dish was heated ? How is water glass made ? 
 
200 INORGANIC CHEMISTRY 
 
 Ex. 117. Try at home the experiment of preserving eggs in water 
 glass. Dilute the commercial water glass with nine times its volume 
 of water and keep the eggs immersed in the liquid. Cover the jar or 
 crock to prevent evaporation. Only perfectly fresh eggs should be 
 used. The eggs will keep for a year or more. What other uses are 
 made of water glass ? What is ordinary glass and how made ? De- 
 scribe some of the different kinds of glass. 
 
 Ex. 118. What can you say about the distribution of the natural 
 silicates? Give the formulas for the different silicic acids. What 
 are meant by mixed salts ? Do the natural silicates contain more than 
 one metal as a rule ? How are the silicates decomposed in the labora- 
 tory ? What is the chemical test for silica or a silicate ? 
 
 Ex. 119. Examine a crystal of borax. What is its chemical name 
 and formula? Dissolve a crystal in water. How does the solution 
 feel? Test with red litmus paper. What uses are made of borax? 
 Why is it used in soldering? Should it be used as a food preservative? 
 What is boric acid and how is it prepared ? What use is made of it ? 
 
 Ex. 120. Place a crystal of borax in an evaporating dish. Add 
 a little sulphuric acid and some alcohol. Warm gently and ignite the 
 alcohol. Is a color imparted to the flame? How could the presence 
 of borax or boric acid in a food be detected ? 
 
CHAPTER XX 
 RECOGNITION OF SUBSTANCES 
 
 197. Review of the Non-metals. The most important of 
 the non-metallic, or acid-forming, elements and their more 
 familiar compounds, as well as two of the metals, sodium 
 and calcium, have been discussed in the preceding chapters. 
 Before taking up the other important metallic elements it 
 will be well to review some of the facts already learned. In 
 order to present these facts from a new viewpoint this re- 
 view is made in connection with a study of the tests for the 
 recognition of the non-metals and their radicals. To avoid 
 unnecessary repetition references are given to the previous 
 statements of facts, and to understand what is said here the 
 reader should look up every reference and reread the state- 
 ment. 
 
 198. Testing for a Single Substance. The complete 
 analysis of a mixture of substances is a very difficult matter 
 and requires much more knowledge of chemistry than can 
 be obtained from the study of a brief treatise such as this one. 
 Most of the substances that have been studied are either 
 elements or simple compounds, and it is possible to work 
 out a scheme for their recognition that will not be too elab- 
 orate for the purposes of this text. To identify a salt 
 completely it is necessary to investigate the acid and the 
 basic radicals as two separate problems; but at this time 
 only the method of recognizing the acid radical will be 
 
 201 
 
202 INORGANIC CHEMISTRY 
 
 presented, and the detection of the basic or metallic part of 
 the salt will be studied in Chapter XXVIII. 
 
 199. Examination of a Solid. If the substance under 
 examination is an element, it is probably carbon, or sulphur, 
 as these are the only familiar non-metallic elements that are 
 solids'. Carbon may be recognized by its black color (89-94) 
 and by the fact that carbon dioxide is formed when it burns. 
 Ignite the substance and hold over it a glass rod which has 
 been dipped in limewater (101). Sulphur may be recog- 
 nized by its yellow color (59). Verify by dissolving in carbon 
 bisulphide and recrystallizing (60). 
 
 If the material is not one of the above elements, place a 
 small quantity in a test tube, moisten it with sulphuric acid, 
 warm it gently, and note the result. 
 
 (a) A colorless gas may be given off. The odor of sul- 
 phur dioxide indicates that the substance is a sulphite 
 (86 and 88). The odor of hydrogen sulphide indicates a 
 sulphide (87). If the gas is odorless, it is probably carbon 
 dioxide from a carbonate. Test it with a glass rod that has 
 been dipped in limewater (101). A gas may be given off 
 which is colorless but which fumes when breathed upon. 
 This indicates hydrochloric acid from a chloride (121). 
 Verify by dissolving a small portion of the original substance 
 in water and adding a drop of nitric acid and a few drops 
 of silver nitrate (132). It may be nitric acid from a nitrate. 
 Verify by adding a bit of zinc and heating (153), or by testing 
 a water solution of the original substance with ferrous sul- 
 phate and sulphuric acid (149). 
 
 (b) A yellow gas which does not fume may be chlorine 
 from bleaching powder (124) ; in which case the gas will 
 readily bleach litmus paper or a bit of colored cloth or a 
 flower (123). 
 
RECOGNITION OF SUBSTANCES 203 
 
 (c) No gas evolved indicates a sulphate (88), a phosphate 
 (180), a borate (196), a silicate (191), or a basic oxide. 
 
 (d) The substance may be an ammonium salt. Test by 
 heating a small portion with a solution of sodium hydroxide 
 and noting the odor (167). 
 
 EXERCISES 
 
 Ex. 121. Obtain samples of single unknown substances from the 
 teacher and test them carefully according to the plan outlined in this 
 chapter. Read the chapter carefully before beginning the experiment. 
 Look up all cross references. The substances may be any of the follow- 
 ing: 
 
 sulphur carbon 
 
 a sulphide a carbonate 
 
 a sulphite a nitrate 
 
 a sulphate a phosphate 
 
 a chloride a borate 
 
 an ammonium salt 
 
 Make a careful record of the results of each test. 
 
 (Note. The teacher should make this chapter the basis of a 
 thorough review of the preceding chapters.) 
 
CHAPTER XXI 
 POTASSIUM 
 
 200. THE metal potassium resembles sodium in most of 
 its properties. It is a soft solid, which will float on water. 
 The freshly cut surface has a silvery-white metallic luster. 
 It acts upon water even more energetically than does sodium, 
 causing the evolution of hydrogen and forming potassium 
 hydroxide : 
 
 K + H 2 O ->- KOH + H. 
 
 The heat evolved by this reaction is so great that it ignites 
 the liberated hydrogen. Like sodium it must be stored in 
 coal oil to prevent its absorbing moisture and oxygen from 
 the air. 
 
 201. Occurrence of Potassium. The metal is never found 
 free, but its compounds are widely distributed. Many of 
 the rocks from which soils are formed contain potassium 
 compounds, and consequently potassium is present in small 
 quantities in all soils. Potassium is one of the essential 
 constituents of plant food and is always found in plants. 
 When vegetable material is burned, the potassium remains 
 in the ashes as potassium carbonate (K 2 CO 3 ). Formerly 
 wood ashes were the principal source of potassium. The 
 impure potassium carbonate dissolved from the wood ashes 
 is called potash. Some of the giant seaweeds that grow 
 along the Pacific coast contain as much as 35 per cent of 
 
 204 
 
POTASS UM 
 
 205 
 
 their dry weight of potassium chloride. Much potassium 
 is obtained from the potash deposits of Europe. These 
 deposits are made up of sixteen or more different salts, and 
 the beds, which are nearly 3000 feet thick, were probably 
 formed by the evaporation of sea water. 
 
 The element potassium is prepared by electrolysis of its 
 compounds in the manner described under sodium (125). 
 
 FIG. 115. Mining potash salts. 
 
 202. Potassium Hydroxide. Potassium hydroxide (KOH) 
 is a white, brittle substance resembling sodium hydroxide, 
 and is prepared by the same methods (126). It absorbs 
 moisture when exposed to the air and is used for removing 
 both water and carbon dioxide from gases. In chemical 
 behavior it is like sodium hydroxide, and as the latter is 
 much cheaper than potassium hydroxide it is more commonly 
 used commercially. The common name for potassium 
 hydroxide is caustic potash. 
 
 203. Potassium Chloride. Potassium chloride (KC1) re- 
 sembles the corresponding sodium compound in appearance 
 
206 
 
 INORGANIC CHEMISTRY 
 
 and chemical behavior. The chloride is found in large 
 quantities in the European deposits and is used as the start- 
 ing point in the production of most of the other potassium 
 compounds. The crude salt is sold as a fertilizer under the 
 trade name of muriate of potash. 
 
 204. Potassium Carbonate. Potassium carbonate (K 2 CO 3 ) 
 b commonly prepared from wood ashes. The ashes are 
 
 placed in a barrel or 
 other receptacle, and 
 water is poured on 
 them and drawn off 
 at the bottom. The 
 lye thus obtained 
 contains potassium 
 carbonate, or potash, 
 and is often used in 
 making soft soap. 
 The refined potas- 
 sium carbonate is 
 called pearl-ash. It 
 has been stated that 
 the substance sold 
 as potash is very 
 often sodium hy- 
 droxide (126). 
 
 205. Potassium 
 Sulphate. Potassium sulphate (K 2 SO 4 ) occurs in combina- 
 tion with other salts of potassium in the European deposits. 
 It is sold as a fertilizer under the name of sulphate of potash. 
 It is also used in medicine and in preparing ordinary alum. 
 206. Potassium Nitrate. Potassium nitrate (KNO 3 ) is 
 commonly called saltpeter or, sometimes, niter. When or- 
 
 FIG. 116. Leaching potash from wood ashes. 
 
POTASSIUM 207 
 
 ganic matter containing nitrogen decays in the presence 
 of bases, nitrates are formed (168). Advantage was for- 
 merly taken of this fact to produce saltpeter artificially. Ref- 
 use animal matter was mixed with earth and wood ashes 
 and the pile was moistened with liquid manure from the 
 stable. After two or three years the nitrate that had de- 
 veloped in the pile was dissolved out with water and purified. 
 In some hot, dry climates saltpeter is formed in the soil 
 near the villages in quantities sufficient to be extracted on 
 a commercial scale. At the present time, however, most of 
 the potassium nitrate is made by treating a hot solution of 
 sodium nitrate with potassium chloride. 
 
 NaNO 3 + KC1 ->- KNO 3 + NaCl. 
 
 Potassium nitrate is a white solid which occurs in long slender 
 crystals. It gives off oxygen readily when heated and is, 
 therefore, a good oxidizing agent. It is used to some extent 
 in medicine and in the preservation of meat, but its principal 
 use is in the manufacture of black gunpowder. 
 
 207. Gunpowder is a mixture of potassium nitrate (75 
 per cent), charcoal (15 per cent), and sulphur (10 per cent). 
 The ingredients are moistened with water and thoroughly 
 mixed by grinding, and the mixture is then dried. When 
 gunpowder burns in a closed space, a large amount of gas 
 is suddenly formed. One gram of powder yields 280 cc. 
 of gas, and the heat produced causes a great expansion of 
 the gas. The reaction is approximately as follows : 
 
 2 KNO 3 + 3 C + S ->- 3 CO 2 + 2 N + K 2 S. 
 
 The explosion is due to the suddenness with which the gases 
 are generated and the heat is developed. Smokeless powder 
 (314) has now replaced black gunpowder in warfare. 
 
208 INORGANIC CHEMISTRY 
 
 208. Potassium Chlorate. Potassium chlorate (KC1O 3 ) 
 was used in the preparation of oxygen (28). At high tem- 
 peratures it decomposes into oxygen and potassium chloride : 
 
 KC1O 3 ->- KC1 + 3 O. 
 
 Potassium chlorate forms flat white crystals and tastes 
 like saltpeter. It is used to prepare oxygen and in the 
 manufacture of fireworks and matches. In the form of 
 chlorate of potash tablets it is used as a remedy for sore 
 throat. It is prepared by the electrolysis of a hot solution 
 of potassium chloride : 
 
 KC1 + 3 H 2 O -- KC1O 3 + 6 H. 
 
 209. Potassium Cyanide. Potassium cyanide (KCN) 
 is a white solid which smells like bitter almonds. It is 
 extremely poisonous. It is used in photography and in 
 extracting gold from its ores. When acted upon by sul- 
 phuric acid, it yields a gas having the formula HCN : 
 
 2 KCN + H 2 SO 4 ->- K 2 SO 4 + 2 HCN. 
 
 This gas (HCN) is called hydrocyanic acid. Its solution 
 in water is known as prussic acid. Hydrocyanic acid is a 
 deadly poison and is sometimes used in fumigating trees 
 to kill scale insects and also in the fumigation of greenhouses. 
 It must be used with extreme care. 
 
 210. Test for Potassium Compounds. A beautiful violet 
 color imparted to the Bunsen flame is the test for potassium 
 compounds. This test is easily applied to the pure com- 
 pounds, but if sodium is present the yellow sodium flame 
 hides the violet color of- the potassium. If the flame is 
 viewed through a piece of blue (cobalt) glass or through a 
 thin layer of indigo solution, the violet color can readily 
 be seen, while the yellow color is not transmitted. 
 
POTASSIUM 209 
 
 EXERCISES 
 
 Ex. 122. What substance previously studied does potassium re- 
 semble ? How does it react with water ? Is it more or less energetic 
 than sodium ? Discuss the occurrence of potassium in nature. What 
 is potash? What compound of potassium is found in wood ashes? 
 What is the principal source of potassium compounds at the present 
 time ? Try the flame test on a potassium salt. What is the result ? 
 
 Ex. 123. What is caustic potash? Allow a small piece of potas- 
 sium hydroxide to remain exposed to the air on a watch glass. What 
 happens? What substance with which you are familiar does potas- 
 sium chloride resemble in appearance and chemical behavior ? Where 
 is crude potassium chloride obtained ? What use is made of it chemi- 
 cally ? By what common name is it generally known ? 
 
 Ex. 124. Place some wood ashes on a filter and pour on a little 
 water. How does the liquid which runs through the filter feel when 
 rubbed between the fingers? Evaporate the filtrate. What is the 
 composition of the residue ? Have you ever seen soft soap made with 
 lye from wood ashes ? Do wood ashes which have been exposed to the 
 weather contain much potash ? 
 
 Ex. 125. What is the chemical composition of saltpeter? The 
 chemical name and formula ? How was it formerly produced ? How 
 is it produced at the present time ? For what is it used ? How is 
 black gunpowder, or blasting powder, made? What causes the ex- 
 plosion when gunpowder is ignited ? What is the probable reaction ? 
 
 Ex. 126. What is- the formula of potassium chlorate? What 
 changes does it undergo when heated at a high temperature ? Have 
 ready half a teaspoonful of potassium chlorate and a like quantity 
 of manganese dioxide on separate papers. Place the chlorate in a dry 
 test tube and heat cautiously until the chlorate is melted. Test with 
 a glowing splint for oxygen. If not heated too strongly, no oxygen 
 will be evolved. Remove the flame and at once drop the manganese 
 dioxide into the melted chlorate and test for oxygen. Why is the man- 
 ganese dioxide used with potassium chlorate in making oxygen ? Does 
 the manganese dioxide undergo any change ? 
 
 EV. CHBM. 14 
 
CHAPTER XXII 
 MAGNESIUM AND ZINC 
 
 MAGNESIUM 
 
 211. Occurrence of Magnesium. Magnesium is widely 
 distributed and ranks close to calcium in amount. The stone 
 known as dolomite, or magnesian limestone (CaCO 3 MgCOs) 
 is well known. Some mountain ranges are largely of 
 dolomite and beds of it cover thousands of square miles 
 in the Mississippi Valley. Magnesite (MgCOs) occurs fre- 
 quently. Magnesium carbonate is usually found to some 
 extent in all limestones. Magnesium is found in sea water, 
 in many mineral waters, and in several of the European 
 potash salts. It is a component of serpentine, talc soap- 
 stone, asbestos, meerschaum, and some other silicates. 
 
 212. Magnesium is a lustrous, silvery-white metal having 
 a specific gravity of only 1.75. It is -produced from its 
 compounds by electrolysis. It is ductile, and when hot 
 may be drawn into wire or ribbon, the latter being a common 
 commercial form. It burns with a dazzling white light. 
 Magnesium powder is an ingredient of photographic flash- 
 light powders, in which the magnesium is mixed with about 
 twice its own weight of powdered potassium chlorate. 
 
 213. Magnesium oxide (MgO) is the white bulky powder 
 formed when magnesium burns. It is usually manufac- 
 tured by heating the carbonate, just as lime is made from 
 limestone. It is often called magnesia, or calcined magnesia. 
 
 210 
 
MAGNESIUM 211 
 
 It is used in medicine for certain forms of dyspepsia and as 
 an antidote for poisoning by mineral acids. It does not form 
 the hydroxide as readily as calcium oxide does, and the lime 
 made from magnesium limestone is not so desirable for 
 building purposes as that from calcium limestone. 
 
 214. Magnesium sulphate (MgS<V7H 2 O) is the salt 
 known as Epsom salts. It was first recognized in the mineral 
 spring at Epsom, England. It is used in medicine as a 
 purgative ; also as a coating for cotton cloth, and in dyeing. 
 
 215. Magnesium chloride (MgCl 2 ) is even more deli- 
 quescent than calcium chloride. When exposed to the air, 
 it soon absorbs sufficient moisture to dissolve itself. It 
 is present in small quantities in all natural deposits of common 
 salt, and the tendency of table salt to become moist and 
 cake is due to the presence of magnesium chloride. A 
 small amount of sodium bicarbonate added to salt will pre- 
 vent caking. Starch is sometimes used for the same purpose. 
 
 216. Test for Magnesium Compounds. Make a small 
 cavity in a piece of charcoal and fill it with the substance to 
 be tested. Moisten with water and heat strongly in the blow- 
 pipe flame (Fig. 125). Cool, add a drop of cobalt nitrate solu- 
 tion, and heat again. Cool and examine. Magnesium com- 
 pounds leave a pink or pale flesh-colored residue in the 
 charcoal. 
 
 ZINC 
 
 217. Preparation of Zinc. Zinc is found as zinc blende 
 (ZnS) and smithsonite (ZnCO 3 ). From the carbonate ore, 
 zinc oxide (ZnO) is obtained by heating. From zinc blende, 
 the oxide is produced by roasting the ore which removes the 
 sulphur and leaves the oxide : 
 
 ZnS + 3 O ->- ZnO + SO 2 . 
 
212 INORGANIC CHEMISTRY 
 
 The oxide is then reduced by heating with powdered coal : 
 
 ZnO 4- C -> Zn + CO. 
 
 This method of extracting zinc from its ores should be 
 carefully considered. The ores of most metals consist of 
 the carbonates, oxides, or sulphides ; and the method of 
 handling them is in general the same as that described for 
 zinc. In the case of the other metals only the forms of the 
 furnaces and other details vary. The art of extracting metals 
 from their ores is called metallurgy. The metallurgy of 
 zinc involves the roasting of the ores to produce the oxide, 
 which is then reduced with carbon. 
 
 218. Pure zinc (Zn) is a bluish white metal with a specific 
 gravity of 7.1. It can be rolled into thin malleable sheets. 
 When melted and poured into water, it forms thin flakes 
 and in this condition is called mossy zinc. Sheet zinc is used 
 as a lining for tanks and sinks and to protect floors beneath 
 stoves. In sticks or plates it is used in electric batteries. 
 Iron dipped into melted zinc becomes coated with zinc and 
 is called galvanized iron. The zinc protects the iron and 
 prevents rusting. About two thirds of the zinc produced is 
 used in this way. In the laboratory it is used to prepare 
 hydrogen. It is used also in the manufacture of brass, 
 German silver, and other alloys (255). 
 
 219. Zinc oxide (ZnO) is a white powder obtained by 
 roasting the carbonate, or by burning the metal. It is com- 
 monly known as zinc white. It is used as a pigment in white 
 paints and has the advantage over white lead of not darkening 
 from exposure to hydrogen sulphide, as zinc sulphide is white, 
 while lead sulphide is black. Zinc white, however, has only 
 three fourths the covering power of white lead. Zinc oxide 
 is used as a filler in the rubber of automobile tires. It is 
 also a constituent of zinc ointment. 
 
ZINC 213 
 
 220. Other Zinc Compounds. Zinc chloride (ZnCl 2 ) is 
 a white deliquescent solid. The aqueous solution is used 
 for cleaning metal surfaces before soldering. The largest 
 use of the chloride is in wood preservation. Zinc sulphate 
 (ZnSCX 7 H 2 O), commonly known as white vitriol, is used 
 in medicine and in the dyeing and printing of cloth. 
 
 221. Testing for Zinc Compounds. (1) Zinc is the only 
 common metal that forms a white sulphide that is insoluble 
 in water. If the substance is not soluble in water, dissolve 
 in hydrochloric acid, neutralize the acid with ammonia 
 water, and add hydrogen sulphide. A white precipitate 
 indicates zinc. (2) Fill a small cavity in a piece of char- 
 coal with the substance. Moisten it with water and heat it 
 strongly in the blowpipe flame. Cool it and moisten it with 
 a drop of cobalt nitrate solution, then heat it again. Cool 
 and examine. Zinc compounds leave a green incrustation. 
 
 EXERCISES 
 
 Ex. 127. Ignite a short piece of magnesium ribbon and note how 
 it burns. What is the white compound formed? What use is made 
 of metallic magnesium? Discuss the occurrence of magnesium in 
 nature. What is the most abundant compound of magnesium ? What 
 is calcined magnesia? Is magnesium lime as valuable for building 
 as the calcium lime ? What is the common name for magnesium sul- 
 phate ? What is the effect of the presence of a small quantity of mag- 
 nesium chloride in table salt ? What is meant by* the statement that 
 magnesium chloride is very deliquescent ? 
 
 Ex. 128. Test a sample of a magnesium compound (216). Result? 
 
 Ex. 129. Give the properties of zinc. For what is it used ? How 
 does it react with dilute acid ? Write reaction for preparation of hy- 
 drogen from zinc and sulphuric acid. How is zinc separated from its 
 ores? Give reactions in the preparation of zinc from the sulphide. 
 How is zinc oxide prepared ? How used ? Test a sample of zinc oxide 
 according to paragraph 221. Name articles at home that contain zinc. 
 
CHAPTER XXIII 
 ALUMINUM 
 
 222. ALUMINUM is a bluish white metal with a specific 
 gravity of 2.6, which is about one third that of iron. It is 
 ductile and malleable and can be readily drawn into a wire 
 or pressed into thin sheets. Aluminum does not change in 
 the air, and this property, combined with its low specific 
 
 FIG. 117. Lightweight camp cooking outfit of aluminum. 
 
 gravity, makes it useful in the manufacture of articles in 
 which lightness is important. Its attractive appearance has 
 led to its extensive use as an ornamental metal. It is ex- 
 tensively used for the manufacture of cooking utensils. The 
 powdered metal is used in making aluminum paint. It is a 
 good conductor of electricity and is coming into use in elec- 
 tric work as a substitute for copper, especially in long-dis- 
 tance wires. A small quantity of aluminum added to cast 
 
 214 
 
ALUMINUM 215 
 
 iron prevents the formation of bubbles and air holes. The 
 metal is trivalent and readily displaces hydrogen from hy- 
 drochloric acid : 
 
 Nitric acid and dilute sulphuric acid act upon it very slowly. 
 Concentrated sulphuric acid dissolves it, forming the sulphate 
 and sulphur dioxide. The metal also dissolves in strong 
 alkalies. Acids and alkalies should be avoided in using 
 cooking vessels made of aluminum. 
 
 223. Occurrence. Aluminum forms 7 per cent of the 
 earth's crust, and next to oxygen and silicon it is the most 
 abundant element. As the silicate it is found in feldspar, 
 mica, and clay. As the oxide (A1 2 O 3 ), it occurs in corundum 
 and emery, which are used as abrasives. The sapphire, the 
 ruby, the oriental topaz, and the amethyst are aluminum 
 oxide colored by traces of impurities. Cryolite, a fluoride 
 of aluminum and sodium (Na 3 AlF 6 ), is an important com- 
 pound. Aluminum occurs also as the hydrated oxide called 
 bauxite (A1 2 O 3 3 H 2 O) . 
 
 224. Preparation. Although aluminum is very abundant 
 in nature, it is never found in the free state. The cost of 
 the earlier methods 
 
 of separating it from 
 its ores was so great 
 that until recent 
 years it was almost 
 a curiosity. Since 
 aluminum is a 
 
 FIG. 118. Electrolytic production of aluminum. 
 
 stronger reducing 
 
 agent than carbon, the metal cannot be prepared by the 
 
 method used for zinc. It was formerly made by heating 
 
216 INORGANIC CHEMISTRY 
 
 the chloride with metallic potassium. The method now 
 used (Fig. 118) was discovered in 1886 by Charles W. Hall, 
 an American youth, just out of college and only twenty- 
 two years of age. Hall's method consists in passing an 
 electric current through a mass of molten cryolite to which 
 bauxite has been added. Under these conditions the 
 bauxite is decomposed into aluminum and oxygen. This 
 process has reduced the price of the metal from $90 a pound 
 in 1886 to about twenty cents a pound at present. If a 
 cheap method could be discovered to prepare it from ordi- 
 nary clay, the metal could be put to many new uses. 
 
 225. Aluminum sulphate (A1 2 (SO 4 ) 3 - 18 H 2 O) is a white 
 crystalline solid, readily soluble in water. It is used in 
 purifying water and sewage, as a mordant for fixing dye- 
 stuffs on fabrics, and as a sizing material in the manufac- 
 ture of paper. 
 
 226. Ordinary Alum. When solutions of aluminum sul- 
 phate and potassium sulphate are mixed and evaporated, 
 transparent, colorless, glassy crystals are formed. This 
 solid is alum and has the composition represented by the 
 formula KA1(SO 4 ) 2 12 H 2 O. Alum is very soluble in water, 
 and the solution has an acid reaction and a sweetish, puckery 
 taste. When heated it loses its water of crystallization and 
 some sulphuric acid and falls into a white powder or porous 
 mass known as burnt alum, which is used in medicine. 
 
 227. Other Alums. It will be noted that alum is com- 
 posed of a univalent metal (potassium) and a trivalent metal 
 (aluminum) combined with the sulphuric acid radical. Any 
 univalent atom may be substituted for potassium, and any 
 trivalent atom (as the iron or chromium atom) may take 
 the place of aluminum. No matter what the combination 
 may be, the crystalline form, the water of crystallization, 
 
ALUMINUM 
 
 217 
 
 the acid reaction, and the puckery taste are the same. The 
 following are the better known alums : 
 
 KA1(SO 4 ) 2 12 H 2 O potassium alum ; 
 NH 4 A1(SO 4 ) 2 12 H 2 O ammonium alum ; 
 NH 4 Fe(SO 4 ) 2 12 H 2 O iron alum ; 
 KCr(SO 4 ) 2 12 H 2 O chrome alum. 
 
 The aluminum alums are used in the dyeing industry, in the 
 manufacture of paper, and, improperly, in baking powder 
 (426). They are also used in fireproofing wood and cloth. 
 Chrome alum is used in the tanning industry and as a 
 hardener in the fixing bath used in photography. 
 
 228. Clay, Pottery, Porcelain. Clay is an impure 
 aluminum silicate formed by the action of carbon dioxide 
 and water on the 
 feldspars, during the 
 weathering of granite 
 rocks. The products 
 of the decomposition 
 are chiefly an in- 
 soluble aluminum 
 silicate and a soluble 
 alkaline silicate. The 
 latter is largely 
 washed away. The 
 aluminum silicate is 
 pure clay or kaolin 
 (H 4 Al 2 Si 2 4 ). Pure 
 kaolin is a white, 
 powdery mass. Or- 
 dinary clay contains many impurities, such as quartz and 
 compounds of iron, calcium, and magnesium. 
 
 FIG. 119. The interior of a pottery kiln. 
 
218 
 
 INORGANIC CHEMISTRY 
 
 All kinds of clay form a stiff plastic mass which can be 
 molded into any shape. When dried it shrinks consider- 
 ably, and when strongly heated it shrinks still further and 
 forms an infusible mass which is not attacked by water or 
 
 acids, and which can 
 no longer be made 
 into a paste with 
 water. In this way 
 bricks, pottery, and 
 porcelain are made. 
 The red color in 
 bricks and common 
 pottery is due to 
 iron in the clay. 
 
 As burned clay is 
 very porous, pottery 
 is generally glazed 
 by throwing salt into 
 the oven in which 
 
 FIG. 120. Brick making in the old way, India. 
 
 pottery is being 
 
 fired. The steam from the clay decomposes the salt, giving 
 NaOH and HC1, and the alkali combines with some of the 
 clay, forming a fusible silicate, which melts and covers the 
 pottery or brick, and on cooling becomes a hard glassy film. 
 
 For porcelain pure kaolin mixed with feldspar is used. 
 After the porcelain is fired, it is glazed by being covered with 
 a thin cream of powdered feldspar and water and heated 
 to a white heat. The feldspar melts and penetrates the 
 porcelain, forming a thoroughly adherent glaze. 
 
 229. Ultramarine is a deep blue material used as a paint 
 pigment, for laundry blue, in making blue tinted paper, 
 and in correcting the yellow shade of linen, starch, sugar, 
 
ALUMINUM 219 
 
 and paper stock. It is made by heating together kaolin, 
 sodium carbonate, sulphur, and charcoal. Formerly it was 
 prepared by powdering the blue mineral, lapis lazuli. 
 
 230. Test for Aluminum. When an aluminum compound 
 is strongly heated in a blowpipe flame, and the resulting 
 white mass is moistened with a drop of cobalt nitrate solu- 
 tion and again heated, it becomes sky blue. 
 
 EXERCISES 
 
 Ex. 130. Give the general properties of aluminum. Does it rust 
 or tarnish? How does it compare with iron in weight? For what 
 is it used ? Why should acids and alkalies be avoided in using cooking 
 vessels made of aluminum? How does aluminum occur in nature? 
 How is the metal prepared ? Why can it not be reduced with carbon 
 as in the case of zinc? What effect did Hall's discovery have on the 
 price of aluminum ? What aluminum articles can you find at home ? 
 
 Ex. 131. Dissolve about ten grams of aluminum sulphate in the 
 least possible amount of boiling water. Dissolve 3 grams of potassium 
 sulphate in the same way. Mix the clear, hot, saturated solutions 
 in a shallow dish, and allow the mixture to cool undisturbed. Re- 
 move and examine the best crystals which form. Are they aluminum 
 sulphate ? Potassium sulphate ? Has a new compound been formed ? 
 What is this substance? Test to prove that these crystals contain 
 potassium, aluminum, and the sulphate radical. Give the formula for 
 ordinary alum. Test a solution of alum with blue litmus paper. Give 
 names and formulas of three other alums. Mention some uses of the 
 alums. 
 
 Ex. 132. What is clay and how formed ? What is the appearance 
 of pure kaolin ? Why are some clays colored ? Work some clay into 
 a plastic mass with water. Heat a piece of this mass to a high temper- 
 ature. How has the heat affected the plasticity of the clay? How 
 are bricks and common pottery made? What is meant by glazing 
 the pottery ? From what is porcelain made ? How is it glazed ? 
 
 Ex. 133. What is ultramarine and how is it made? For what is 
 it used ? How was it formerly prepared ? Test a crystal of alum for 
 aluminum according to paragraph 230. What is the result ? 
 
CHAPTER XXIV 
 
 IRON 
 
 231. IRON (Fe) is undoubtedly the most useful of all the 
 metals. It rarely occurs in the free state, but as it is easily 
 
 prepared from its ores 
 it has been known 
 from the early ages. 
 The principal ores of 
 iron are the oxides, 
 hematite (Fe 2 O 3 ) and 
 magnetite (Fe 3 O 4 ), 
 and the carbonate 
 (FeCO 3 ). Iron in the 
 metallic state has been 
 found in meteors. 
 
 232. Extraction of 
 Iron from Its Ores. 
 
 chemical process 
 
 FIG. 121. -Mining iron ore, Minnesota. 
 
 of obtaining iron from its ores is a very simple one. What- 
 ever ore is used, it is first converted into the oxide by 
 roasting, if it is not already in the form of the oxide (217), 
 It is then reduced in a blast furnace by carbon in the form 
 of coke or hard coal. The carbon removes the oxygen from 
 the oxide. The blast furnace (Fig. 122) is from 25 to 90 feet 
 high and from 15 to 18 feet wide in the widest part. Alter- 
 nate layers of ore and fuel are introduced at the top of the 
 
 220 
 
IRON 
 
 221 
 
 Coke. 
 
 ft Iron Ore. 
 o Lime5tone. 
 
 D/vpj of 
 flelted Iron. 
 
 furnace. Since many ores of iron contain earthy impurities, 
 limestone is always placed in the furnace with the iron and 
 coke. This combines with 
 the earthy materials to 
 form slag, which is some- 
 what similar to glass. The 
 molten iron, being the 
 heavier liquid, sinks to 
 the bottom and is drawn 
 off and cast into bars 
 about three feet long and 
 six inches thick, which are 
 known as pigs. The slag 
 is sometimes used in the 
 manufacture of Portland 
 cement. 
 
 233. Cast Iron. The 
 pig iron drawn off from 
 the furnace is always im- 
 pure, containing some 
 phosphorus, silicon, sul- 
 phur, and carbon. It is 
 brittle and easily melted, 
 and is used for casting, 
 being known as cast iron. 
 
 234. Wrought Iron. 
 When practically all of 
 the impurities are removed 
 from iron, it is no longer 
 brittle. It becomes mal- 
 leable and at a red or white heat it can be hammered or 
 pressed into any desired shape. It is now known as wrought 
 
 A Drops of 
 tlcKcd Slag. 
 
 A.rtgter/6/ 
 on Convf/or 
 
 FIG. 122. A bkst furnace. 
 
222 
 
 INORGANIC CHEMISTRY 
 
 iron. It can also be welded; that is, two pieces of the 
 metal can be united when hammered or rolled together. 
 
 235. Steel is iron that contains from 0.8 to 2.5 per cent 
 of carbon. Steel can be forged like wrought iron. A very 
 
 important property of 
 steel is its power of 
 being tempered, or 
 rendered hard or soft 
 at will. When heated 
 to redness and sud- 
 denly plunged into 
 cold water, it is ren- 
 dered very hard and 
 brittle. If heated and 
 slowly cooled, it is 
 made soft, and by 
 regulating the tem- 
 perature at which it 
 is tempered, almost 
 
 any degree ^of hardness, toughness, or elasticity may be 
 
 obtained. 
 
 236. Basic Slag. In the manufacture of steel from iron 
 containing phosphorus the converter is lined with dolomite 
 (211), which absorbs the phosphoric oxide produced during 
 the process, and forms a basic calcium phosphate. When 
 the lining has absorbed all the phosphorus it can take 
 up, it is removed, pulverized, and sold as a fertilizer under 
 the name of basic slag, or Thomas phosphate. Phosphorus 
 makes steel brittle ; hence the necessity for removing it. 
 
 237. Rusting of Iron. All kinds of iron oxidize readily 
 in moist air, even at ordinary temperatures. To protect 
 the iron from the air and moisture and thus from rusting, 
 
 FIG. 123. Casting pig iron. 
 
IRON 223 
 
 it is covered by a coat of paint, or it is galvanized (218), 
 tinned, or nickel-plated. 
 
 238. Iron Has Two Valences. One atom of iron may 
 hold two or three atoms of a univalent element in combina- 
 tion. In other words, iron may be bivalent or trivalent, 
 according to chemical conditions. Thus there are two 
 
 (chlorides, FeCl 2 and FeCl 3 ; two nitrates, Fe(NO 3 ) 2 and 
 Fe(NO 3 ) 3 ; two sulphates, FeSO 4 and Fe 2 (SO 4 ) 3 . The com- 
 pounds in which iron appears to be bivalent are called ferrous 
 compounds ; for example, ferrous chloride and ferrous nitrate. 
 The compounds of trivalent iron are called ferric com- 
 pounds ; for example, ferric chloride and ferric sulphate. 
 
 239. Change of Ferrous to Ferric Compounds. Ferrous 
 compounds are changed to ferric compounds by contact 
 with air, and oxidizing agents, such as nitric acid. When, 
 for instance, ferrous hydroxide (Fe(OH) 2 ) is exposed to air 
 while suspended in water, it slowly changes to ferric hy- 
 droxide (Fe(OH)s) : 
 
 2 Fe(OH) 2 + H 2 O + O ^ 2 Fe(OH) 3 . 
 
 So, also, when ferrous chloride is left standing in a solution 
 of hydrochloric acid, it changes to ferric chloride, and the 
 change is rapidly effected by boiling with a little nitric acid, 
 which gives up oxygen : 
 
 2 FeCl 2 + 2 HC1 + O -- 2 FeCl 3 '+ H 2 O. 
 
 240. Ferrous sulphate (FeSO 4 -7H 2 O) is the compound 
 commonly known as copperas or green vitriol. It is formed 
 by the action of sulphuric acid on iron. It crystallizes in 
 pale green crystals. It is used as a purifier of water, as 
 a disinfectant, as a reagent for killing weeds, in the dyeing 
 industry, and in the manufacture of writing ink. 
 
224 INORGANIC CHEMISTRY 
 
 241. Inks. The common black writing inks are made by 
 treating a solution of ferrous sulphate with a solution of tannic 
 acid obtained from nutgalls. A little gum arabic is usually 
 added, and a preservative to prevent the ink from molding. 
 
 242. Sulphides of Iron. When iron and sulphur are 
 heated together, they unite to form ferrous sulphide (FeS). 
 It is a black substance which is used in the laboratory to 
 prepare hydrogen sulphide. A sulphide having the for- 
 mula FeS2 is abundantly found in nature and is known as 
 iron pyrites. It is a yellow crystallized substance sometimes 
 called fool's gold. When strongly heated, the sulphur is 
 oxidized to sulphur dioxide, and the iron is left in the form of 
 the oxide. Iron pyrites is commonly used as a source of 
 sulphur in the manufacture of sulphuric acid (84). 
 
 243. Iron compounds are very widely distributed in 
 nature. All soils contain small quantities of iron. The 
 yellow and red color of clays are due to the presence of iron, 
 as are also the colors of many sandstones. Iron is found in 
 plant and animal tissues in minute traces. The formation 
 of the green coloring matter of plants (chlorophyll) is de- 
 pendent upon the presence of iron. The blood of animals 
 contains traces of iron. In fact, neither plants nor animals 
 can live without iron, although the amount needed by them 
 is exceedingly small. 
 
 244. Test for Iron. Tannic acid or an infusion of nut- 
 galls forms a blue -black color and a very finely divided 
 precipitate, which remains suspended in the liquid. 
 
 EXERCISES 
 
 Ex. 134. What are the more common ores of iron ? What can be 
 said about the usefulness of iron ? Does it ever occur in the free state ? 
 Is its use by man of recent or ancient origin? How is iron extracted 
 
IRON 225 
 
 from its ores ? What is pig iron ? Cast iron ? What is the principal 
 difference between cast iron and wrought iron? What is meant by 
 welding ? What is the purest common form of iron ? In what marked 
 way does steel differ from wrought iron ? Visit a blacksmith shop and 
 ask the smith to illustrate the tempering of steel. 
 
 Ex. 135. Why is the presence of phosphorus in steel objectionable ? 
 How is the phosphorus removed in making steel ? What is basic slag ? 
 j Dissolve a little basic slag in nitric acid and test for phosphorus with 
 molybdate reagent. 
 
 Ex. 136. What causes the rusting of iron? Will iron rust if per- 
 fectly dry? How may it be protected to prevent rusting? What 
 compounds does iron make with sulphur ? What is fool's gold ? 
 
 Ex. 137. Dissolve a small amount of iron in hydrochloric acid. 
 Divide the solution into two parts and to one add ammonium hy- 
 droxide until strongly alkaline. Filter. Explain the change in color 
 of the precipitate when exposed to the air. Write the reaction. To 
 the second part of the above solution add a little hydrogen peroxide. 
 Explain the effect of the peroxide on the solution. Add ammonium 
 hydroxide in excess as above. How does the precipitate compare with 
 that from the first solution? What two classes of compounds does 
 iron form ? 
 
 Ex. 138. What is the chemical name and formula of copperas? 
 How is it made ? For what is it used ? Add a little tannic acid to a 
 solution of copperas. What happens? What is the test for iron? 
 Discuss the distribution of iron compounds in nature. Is iron necessary 
 to plant and animal life ? How many articles can you find at home that 
 are made of iron ? 
 
 EV. CHEM. 15 
 
CHAPTER XXV 
 
 LEAD 
 
 245. Occurrence and Metallurgy of Lead. Lead is found 
 in nature principally as the sulphide (PbS), known as galena, 
 
 or galenite, a heavy black 
 mineral which crystallizes 
 in cubes having a bright 
 metallic luster. In the 
 process of obtaining lead 
 from the ore, the ore is 
 first roasted in order that 
 a part of the sulphide may 
 be converted into the 
 oxide and sulphate : 
 
 PbS + 3 O 
 PbS + 4O 
 
 PbO + S0 2 , 
 PbS0 4 . 
 
 FiG. 124. Galena. 
 
 Air is then excluded from the furnace, whereupon the sul- 
 phide reacts with the oxide and sulphate as follows : 
 
 2 PbO + PbS -> 3 Pb + S0 2 , 
 PbSO 4 + PbS ->- 2 Pb + 2 SO 2 . 
 
 246. Properties and Use of Lead. Lead is the heaviest 
 of the cheaper metals, having a specific gravity of 11.34. 
 It has a bright white luster when freshly cut but tarnishes 
 quickly in the air. The many uses of this metal depend 
 
 226 
 
LEAD 227 
 
 chiefly upon its low melting point, its great density, and its 
 softness. It is so soft that it can be pressed through a die 
 into the form of tubing, which is used by plumbers to make 
 waste pipes for sinks and sometimes even for water pipes. 
 Sheet lead is used for roofing and for lining tanks. Lead 
 foil forms an air-tight package for tea. Mixed with 20 per 
 cent of antimony it furnishes type metal ; with 0.5 per cent 
 of arsenic it is used for small shot ; and equal parts of lead 
 and tin form solder. Lead dissolves easily in nitric acid, 
 forming the nitrate Pb(NO 3 ) 2 . Hydrochloric and sulphuric 
 acids have little effect on it ; hence its use in. lining the 
 chambers and pans used in manufacturing sulphuric acid, 
 
 247. Lead in Drinking Water. Lead pipes are some- 
 times used to convey drinking water, but there is some danger 
 in this use of lead unless the water is hard. Hard water 
 will generally cover lead with a coating of carbonate which is 
 insoluble and which protects the metal from further action. 
 Soft water, however, dissolves some of the lead, which when 
 thus dissolved in water, acts as a poison. Cases of lead 
 poisoning produced by water which has passed through lead 
 pipes are not uncommon. Lead acts as a cumulative poison, 
 so that minute quantities taken daily for some weeks or 
 months may finally produce fatal results. 
 
 248. Oxides of Lead. Litharge, or lead monoxide (PbO), 
 is readily formed by exposing lead at a red. heat to the action 
 of air. It is a buff-colored substance and is used in the prep- 
 aration of boiled linseed oil and in the manufacture of glass 
 and enamels. Red lead, or lead tetroxide (Pb 3 O 4 ), is formed 
 by heating the monoxide to about 350 degrees C. It is used 
 in making flint glass and in the common red paint used on 
 iron work. Mixed with linseed oil it is used in plumbing 
 and gas fitting to make tight joints. 
 
228 
 
 INORGANIC CHEMISTRY 
 
 249. Sugar of lead (PlXQHaC^) is a soluble salt pre- 
 pared by dissolving litharge in vinegar or acetic acid. Sugar 
 of lead is sometimes used in hair dyes, but its use in this way 
 is considered dangerous, as it is likely to produce paralysis. 
 
 250. White lead is a basic carbonate of lead, having 
 the composition 2 PbCO 3 -Pb(OH) 2 . It is one of the most 
 important compounds of lead and is used in the prepara- 
 tion of paints. It is prepared by the action of carbon dioxide 
 on the oxide and acetate of lead. As a pigment for paints 
 it has an advantage over all others in its much greater opacity 
 and covering power. It has the disadvantage that it is 
 readily blackened by hydrogen sulphide, and it is poisonous 
 to the workmen who handle it. House painters are some- 
 times subject to a painful disease known as lead colic, which 
 is caused by the slow absorption of small particles of white 
 lead into the system. White lead is often adulterated with 
 chalk or barium sulphate. It is being replaced for some 
 purposes by zinc white (219), which is not discolored by 
 hydrogen sulphide. 
 
 251. Lead arsenate (Pbs^sO^) is a white substance 
 usually sold in the form of a paste or a powder. It is used 
 
 for poisoning potato bugs and 
 as an insecticide for use in 
 spraying trees and shrubs. 
 It is less soluble than Paris 
 green and adheres more 
 firmly to the plant, and is not 
 so likely to injure the plant. 
 252. Tests for Lead. If a 
 compound of lead is mixed 
 with sodium carbonate and 
 
 FIG. 125. Testing for lead with blow- i , j i_ i 
 
 pipe. heated on a piece or charcoal 
 
LEAD 229 
 
 in the inner flame of a blowpipe (Fig. 125), a small bead of 
 metallic lead is obtained, and the softness of the bead indi- 
 cates the nature of the metal. A solution of potassium 
 chromate added to a solution containing lead gives a pre- 
 cipitate of chrome yellow. Hydrogen sulphide gives a black 
 precipitate of lead sulphide (PbS). 
 
 EXERCISES 
 
 Ex. 139. What is the principal ore of lead ? How is lead prepared 
 from the ore ? Examine a piece of freshly cut lead and state its prop- 
 erties. What happens to lead when heated? When exposed to the 
 air? Is it easily melted and tarnished? What physical properties 
 adapt it for its extensive use? What are some of the uses made of 
 lead ? Why is it used in lining the chambers and pans in making sul- 
 phuric acid ? Is there any lead in lead pencils ? Why should lead pipes 
 be avoided for carrying drinking water? Which dissolves more lead, 
 hard or soft water ? 
 
 Ex. 140. What is the composition of the red lead used in paint? 
 What is litharge and for what is it used ? What is sugar of lead ? Test 
 a sample of hair dye from the local drug store by adding a little hydro- 
 gen sulphide. A black precipitate indicates the presence of lead. 
 
 Ex. 141. Test a lead compound according to paragraph 252. What 
 is the result ? The same test may be applied to the precipitate from 
 the hair dye to confirm the test for lead. 
 
 Ex. 142. What is the substance known as white lead ? How is it 
 manufactured? For what is it used? What advantage and what 
 disadvantage does it have for use in paints ? Test a sample of paint 
 for the presence of lead. Is white lead often adulterated? What 
 advantage does zinc oxide have over white lead? Why does white 
 lead paint become blackened ? 
 
CHAPTER XXVI 
 
 COPPER 
 
 253. COPPER is, industrially, one of f the most important 
 of the metallic elements. It occurs free in nature and for 
 this reason has, together with silver and gold, been known 
 from a very early period. It is characterized by its reddish 
 color. This color, however, is seen only in fresh surfaces 
 since the metal soon becomes covered with a film of oxide, 
 sulphide, or carbonate. Copper is flexible, hard, and tough, 
 and can readily be drawn into wire or rolled into very thin 
 sheets. Next to silver it is the best-known conductor of 
 heat and electricity. Hydrochloric acid and cold sulphuric 
 
 acid have little effect upon cop- 
 per. It dissolves in nitric acid, 
 forming the nitrate (Cu(NO 3 ) 2 ) 
 and various oxides of nitrogen 
 (143). With hot sulphuric 
 acid it forms the sulphate 
 (CuSC>4) and sulphur dioxide. 
 The most common ore of cop- 
 per is copper pyrites (CuFeS 2 ) . 
 Copper is precipitated from 
 solutions of its salts by iron, zinc, and some other metals, 
 as can be shown by dipping a piece of bright iron or steel 
 into a solution of copper sulphate (Fig. 126). Copper will 
 immediately be deposited as a thin, red coating upon the 
 
 230 
 
 FIG. 126. Copper deposited on a 
 knife blade. 
 
COPPER 231 
 
 iron, and a corresponding amount of the iron will go into 
 solution to replace the copper. 
 
 CuSO 4 + Fe ->- FeSO 4 + Cu. 
 
 254. Uses of Copper. Next to iron, copper is the most 
 useful metal. Enormous quantities of copper wire are used 
 in operating the telegraph, the telephone, the electric rail- 
 way, and the electric light. Sheet copper is made into 
 household utensils, boilers, and stills. Copper bolts, nails, 
 and rivets are used in ships because copper rust does not 
 destroy wood as iron rust does. It is used for ornamental 
 and artistic purposes, and in the printing trade for engraving 
 and electrotyping. 
 
 255. Alloys. Some metals intermix when melted to- 
 gether and when cooled form a metal-like substance which 
 has properties somewhat different from either of the separate 
 metals. Such a mixture of two or more metals is called an 
 alloy. Copper is a constituent part of many of the most 
 important alloys. The following are some common alloys : 
 
 Brass .... 63% -73% copper, 27%-37% zinc 
 Bronze . . . 70% -95% copper, l%-25% zinc, 
 
 19&-18% tin 
 
 German silver . 50% -60% copper, 20% zinc, 
 
 20%-30% nickel - 
 
 Gun metal . . 90% copper, 10% tin 
 
 Silver coin . . 10% copper, 90% silver 
 
 Nickel coin . . 75% copper, 25% nickel 
 
 Bell metal . .75% copper, 25% zinc. 
 
 256. Copper-plating and Electrotyping. Copper is de- 
 posited from a solution of its salts by the electric current. 
 
232 INORGANIC CHEMISTRY 
 
 This fact is utilized in copper-plating. The object to be 
 plated is connected with the negative pole of a battery and 
 hung in a solution of copper sulphate. The other pole is 
 connected with a bar of copper which is also immersed in the 
 solution. As the current passes through the solution, the 
 copper salt is decomposed, and the copper is deposited on 
 the object to be plated. A like amount of copper is dis- 
 solved from the bar connected with the positive pole. 
 
 Books are often printed from electrotype plates. These 
 are made by first taking an impression of the type in wax. 
 The inside of the mold thus formed is dusted over with 
 powdered graphite in order to make it conduct electricity. 
 The mold is connected with the negative pole of the battery 
 and suspended in a solution of copper sulphate. As the cur- 
 rent passes, copper is deposited upon the mold in a cohe- 
 rent film, and a perfect copy of the type is obtained. The 
 sheet is strengthened by filling in the under surface with 
 melted lead. For the daily newspaper this process is too 
 slow and the printing is done from stereotype plates, which 
 are made by pouring melted stereotype metal, consisting of 
 lead, antimony, and tin, into a paper pulp cast of the type. 
 This process gives a printing surface much inferior to the 
 electrotype plate. 
 
 257. Oxides of Copper. When copper is heated to red- 
 ness in the presence of plenty of air or oxygen, a black oxide is 
 formed having the formula, CuO. This compound is called 
 cupric oxide. In the absence of sufficient oxygen to form 
 the cupric oxide, another oxide having a bright red color is 
 produced. This is cuprous oxide, Cu 2 O. Two series of salts 
 (cupric and cuprous) of copper can be prepared corresponding 
 to these two oxides, but only the cupric compounds are of 
 any great commercial importance, 
 
COPPER 233 
 
 258. Copper sulphate, CuSO 4 , is the best known of the 
 salts of copper. It crystallizes from water in beautiful 
 blue crystals having the formula CuSO 4 5 H 2 O, commonly 
 called blue vitriol or bluestone. When heated, the crystals 
 lose water and the mass becomes white. The colorless 
 substance becomes blue again in contact with water. It is 
 used in galvanic batteries, in copper-plating, and as a start- 
 ing point for the formation of various compounds of copper. 
 All copper compounds are poisonous to plants and animals. 
 
 259. Copper hydroxide, Cu(OH) 2 , is formed as an in- 
 soluble precipitate when any soluble hydroxide is added to 
 a solution of copper sulphate or to any other soluble salt of 
 copper : 
 
 CuSO 4 + Ca(OH) 2 -^ Cu(OH) 2 + CaSO 4 . 
 
 It is light blue in color. Copper hydroxide formed according 
 to the above reaction from copper sulphate and slaked lime 
 is known as Bordeaux mixture and is used in spraying plants 
 for the control of certain fungous diseases. Bordeaux mix- 
 ture alone is a fungicide merely and has little poisonous ef- 
 fect on insects. To make it an insecticide as well arsenate 
 of lead (251) is commonly added to the mixture. Ammonia 
 water when added to a solution of copper sulphate first 
 precipitates copper hydroxide and then redissolves it, form- 
 ing a deep blue solution. This preparation has been used 
 as a fungicide under the name of ammoniacal copper sulphate, 
 but its use is largely superseded by Bordeaux mixture. 
 
 260. Paris green is a complex compound of copper with 
 arsenious acid and acetic acid. It is a brilliant green material 
 sometimes called emerald green. It is used in paint making, 
 but more largely for the destruction of potato bugs and other 
 injurious insects. It is slightly soluble and if used in too 
 
234 INORGANIC CHEMISTRY 
 
 large quantities kills the plant as well as the insects. To 
 render it more insoluble lime is sometimes added to it (183). 
 261. Tests for Copper. The salts of copper have either 
 blue or green colors. Ammonia water added to a solution 
 of a copper salt produces a pale blue precipitate, which redis- 
 solves in an excess of ammonia water, yielding a beautiful 
 blue solution. A piece of clean iron or steel dipped into a 
 solution of a salt of copper quickly becomes covered with a 
 red layer of metallic copper. This is a conclusive test. 
 
 EXERCISES 
 
 Ex. 143. Examine a piece of copper and state its obvious physical 
 properties. Is copper a good conductor of heat? Of electricity? Is 
 it flexible, malleable, and ductile ? What happens to it when heated ? 
 How is copper found in nature ? Why has it been known for so long ? 
 Mention some of the principal uses for copper. 
 
 Ex. 144. Dissolve a little copper sulphate in water and place a 
 bright nail or the blade of a knife in the solution. What happens? 
 Write the reaction. Try the same experiment with a piece of zinc. 
 This experiment may be used as a test for copper. 
 
 Ex. 145. What is meant by an alloy ? Name some of the common 
 alloys. Of what is brass composed ? Test a piece of brass for copper. 
 Explain how copper-plating and electrotyping are conducted. What 
 is meant by stereotyping ? 
 
 Ex. 146. Examine some crystals of copper sulphate. What is 
 the formula ? Give the common names. Heat a crystal in a test tube. 
 What happens ? Continue heating until no more water escapes. What 
 is the color of the residue ? When cool,add a few drops of water. What 
 change takes place ? What are some of the uses of copper sulphate ? 
 
 Ex. 147. Add limewater to a solution of copper sulphate. What is 
 the precipitate? Write the reaction. What name is given to this 
 mixture and for what is it used ? Add a few drops of ammonia water 
 to a solution of copper sulphate. What happens ? Add an excess of 
 ammonia water. What change has taken place? This reaction is 
 sometimes used as a test for copper. 
 
CHAPTER XXVH 
 SILVER 
 
 262. SILVER has been known from the earliest times, as it 
 occurs free in nature. Most of the silver now used, however, 
 comes from the sulphide, Ag 2 S, which is found in many places 
 associated with lead sulphide (245). The manner in which 
 silver resists oxidation in the air, together with its brilliant 
 luster when polished, has caused it to be used in all ages for 
 articles of ornament and in coinage. 
 
 Nitric acid is the only acid that easily dissolves silver 
 when dilute. It is easily acted upon by hydrogen sulphide 
 and many other compounds of sulphur. Thus silver spoons 
 become blackened from contact with the albumin of egg, 
 which contains sulphur. Silver articles in contact with 
 rubber become black for the same reason. The blackening 
 is caused by the formation of a film of silver sulphide (Ag 2 S). 
 Pure silver is too soft for constant use and is usually hardened 
 by the addition of a small amount of copper. The silver 
 coins of the United States contain 10 per cent of copper. 
 Silver that contains 7.5 per cent of copper as do British silver 
 coins is called sterling silver. 
 
 263. Silver-plating. Metals less expensive than silver 
 may be coated with pure silver, as in the case of copper. 
 Plated silverware has the appearance of solid silver and does 
 not rust so long as the silver coating is intact. The object 
 to be plated is carefully cleaned, is attached to the negative 
 
 235 
 
236 
 
 INORGANIC CHEMISTRY 
 
 pole of a battery, and is then suspended in a solution of silver 
 nitrate and potassium cyanide (209). The positive pole 
 
 is a plate of pure silver. As the 
 silver from the solution is de- 
 posited on the plated object a 
 like amount is dissolved from the 
 silver plate. The deposit of sil- 
 ver is dull and is brightened by 
 rubbing. 
 
 264. Silver nitrate (AgNO 3 ) 
 is the best known salt of silver. 
 It is made by dissolving silver 
 in nitric acid. It is a white 
 crystalline solid which turns dark 
 if exposed to light while in con- 
 It is sometimes cast into small 
 sticks and called lunar caustic. It dissolves the skin and dis- 
 integrates the flesh if applied long enough. It is sometimes 
 used by physicians to cauterize sores and to remove abnormal 
 growths. It is used also in making indelible ink (Ex. 149). 
 
 265. Silver chloride (AgCl) is formed when hydrochloric 
 acid or any chloride is added to a solution of silver nitrate. 
 Thus formed, it is a white curdy solid which turns violet 
 in the light, and finally black. This action of light is more 
 intense if organic matter is present. Silver chloride dis- 
 solves in ammonia water. Silver bromide (AgBr) and silver 
 iodide (Agl) are analogous to the chloride in their properties 
 and methods of formation. They are more readily de- 
 composed by light than is the chloride. 
 
 266. Photography is Jbased on the fact that silver salts, 
 especially the bromide and iodide, change color when mixed 
 with organic matter and exposed to light. The photograph 
 
 FIG. 127. Silver-plating. 
 
 tact with organic matter. 
 
SILVER 
 
 237 
 
 is taken on a glass plate or celluloid film, which is coated on 
 one side with a thin layer of gelatine containing the silver 
 salt. The plate is placed in the camera and exposed. The 
 light that comes from the object being photographed changes 
 the silver salt in proportion to its brilliancy. The plate, 
 however, shows no change until it has been developed. The 
 developer is a reagent that acts readily on that part of the 
 silver salt that has been affected by the light and changes 
 
 NEGATIVE 
 
 FIG. 128. Negative showing reversal of lights and shadows, and positive showing 
 these features in their natural form. 
 
 it to the metallic silver, which remains as a black deposit. 
 Where the intense light falls upon the plate, the deposit 
 is heavier than where little or no light falls. Hence the dark 
 parts of the object appear light on the plate, and the light 
 parts appear dark; and since the image is .the reverse of the 
 object, the plate is called a negative (Fig. 128). After be- 
 ing developed, the plate is placed in a solution of sodium 
 hyposulphite ("hypo") to dissolve out the unchanged silver 
 salts and is then thoroughly washed with water. The treat- 
 ment with hypo is termed fixing. 
 
 The print, or positive, is made on a paper that has a surface 
 prepared in much the same way as the plate used to make the 
 
238 INORGANIC CHEMISTRY 
 
 negative. The negative is placed on the paper and exposed 
 to the light in such a way that light will pass through the 
 negative, which obstructs the light in proportion to the 
 thickness of the silver deposit. The print, therefore, is the 
 reverse of the negative and has the same shading as the object 
 photographed. The print may be developed, fixed, and 
 washed in the same manner as the negative. 
 
 267. Blue prints are produced by the action of light on 
 a salt of iron. A solution of ferric ammonium citrate and 
 potassium ferricyanide is brushed on a sheet of paper and 
 dried in the dark. If a design drawn on tracing cloth, or a 
 photographic negative, is placed over this paper and the 
 two are exposed to the sunlight, the sensitive paper turns to 
 a brownish color where the light penetrates the negative. 
 Under the black parts of the negative where no light strikes 
 it the paper is unaffected. If, now, the paper is washed in 
 water the unchanged iron salt is removed, while that part 
 affected by the light turns to a blue color. The blue color 
 is due to the formation of the insoluble salt of iron known as 
 Prussian blue. Blue print paper is used in large quantities 
 by architects, engineers, and designers. 
 
 268. The test for silver is the presence of the white 
 curdy precipitate of silver chloride formed by the addition of 
 hydrochloric acid to a silver salt. This precipitate is soluble 
 in ammonia water and darkens when exposed to light. 
 
 EXERCISES 
 
 Ex. 148. Give the physical properties of silver. Is it readily 
 oxidized? Why does it turn black when exposed to the air? When 
 in contact with egg, or rubber, or perspiration? Dissolve a ten-cent 
 piece in nitric acid. What does it contain besides silver ? What is the 
 percentage composition of American silver coins? Of British coins? 
 What is meant by sterling silver ? How are other metals silver-coated ? 
 
SILVER 239 
 
 Ex. 149. What is the name and formula of the salt produced by 
 the action of nitric acid on silver? What is the common name for 
 it ? For what is it used ? Take a little of the solution of the coin and 
 add ammonia water until the precipitate which first forms is again 
 dissolved. With a clean pen write your name on a piece of white cloth 
 with this liquid. When dry press a hot iron on the writing. What 
 happens ? This illustrates one method of making indelible ink. 
 
 Ex. 150. Dilute some of the above solution of the coin with water 
 in a test tube and add a little common salt. What happens ? Write 
 the reaction. Expose the test tube and contents to strong sunlight and 
 note what happens. Paint a piece of plain white paper with a weak 
 solution of salt and allow it to dry. Now brush it over with a solution 
 of silver nitrate (in a dark room). Place a fern leaf or other object on 
 the paper and expose it to the sunlight, using a pane of glass to keep the 
 leaf pressed against the paper. What happens ? How is this property 
 of silver salts utilized in photography? 
 
 Ex. 151. (Teacher) Expose and develop a photographic plate so that 
 the class may watch the different steps. If a very slow plate such as a 
 lantern slide plate is used, the development may be done in any welU 
 darkened room, in case a regular dark room is not available. When the 
 negative is dry make a print with any good developing paper. Use 
 developers recommended by the manufacturers. What does the light 
 coming through the lens do to the plate ? What does the developer do ? 
 Why is the hypo used ? What would happen if the plate were not fixed ? 
 Explain the different steps in the production of the print. 
 
 Ex. 152. Dissolve 1 gram potassium ferricyanide in 5 cc. water; 
 in a separate test tube, dissolve 1| grams ferric ammonium citrate in 5 
 cc. water and mix the two solutions. Now paint a piece of paper with 
 the solution in a dark room by candlelight and let .the paper dry. 
 Expose the paper to the sun's rays under a design on tracing cloth, or a 
 photographic negative. When the exposure has continued long enough 
 (five or ten minutes, according to the amount of light) wash the paper. 
 What change has taken place ? What effect did the light have on the 
 iron salt ? Tell about any blue prints which you have seen. 
 
 Ex. 153. To a little coin solution add hydrochloric acid. What 
 occurs? Add an excess of strong ammonia water. Results? This 
 illustrates the test for silver, as no other metal forms a chloride that is 
 insoluble in nitric acid and water and is soluble in ammonia water. 
 
CHAPTER XXVIII 
 
 REVIEW OF THE METALLIC SALTS RECOGNITION 
 OF THE COMMON METALS 
 
 269. IN the foregoing chapters ten of the more important 
 metals have been briefly discussed. Of these not more than 
 seven are commonly met with in the metallic form ; the others 
 are rarely seen outside of the chemical laboratory. Only 
 three or four of the metals are found in nature in the free 
 state ; the others occur in the oxides, sulphides, carbonates, 
 or silicates. A large number of compounds of the metals 
 are of commercial importance, notably the salts, and a few 
 of the oxides and hydroxides. 
 
 270. Metallic Salts. Theoretically at least, every metal 
 should be able to combine with every acid to form a salt, 
 and as there are many acids and metals the possible number 
 of salts is very large. Only the more important of these 
 salts and especially those which are of more or less common 
 use have been mentioned in this text. Descriptions of many 
 others will be found in the larger texts on chemistry. 
 
 271. Preparation of Salts. There are several general 
 methods which may be used for the preparation of salts. 
 
 (1) A salt may be formed by the action of the proper acid 
 on a metal, an oxide, hydroxide, or carbonate : 
 
 Zn + H 2 SO 4 ->- ZnSO 4 + 2 H, 
 CaO + 2 HC1 ->- CaCl 2 + H 2 O, 
 KOH + HNO 3 -> KNO 3 + H 2 0, 
 MgCO 3 + H 2 SO 4 ->- MgSO 4 + H 2 + CO 2 . 
 240 
 
REVIEW OF THE METALLIC SALTS 241 
 
 (2) If a salt is insoluble in water it may be prepared by 
 precipitation. To a solution of a soluble salt of the metal is 
 added a solution of a soluble salt of the desired acid. For 
 example, calcium carbonate may be prepared by adding a 
 solution of sodium carbonate to a solution of calcium chloride, 
 whereupon the calcium carbonate will be precipitated : 
 
 CaCl 2 + Na2CO 3 -- CaCO 3 + 2 NaCl. 
 
 If the desired salt is insoluble in acids, it may be precipi- 
 tated by adding the desired acid itself in place of the salt : 
 
 AgNO 3 + HC1 -- AgCl + HN0 3 . 
 
 (3) Some of the binary salts may be formed by the direct 
 union of the metallic and non-metallic elements : 
 
 Fe + 3 Cl - 
 
 272. Solubility of Salts. A knowledge of the solubility in 
 water of the different salts is of importance when devising 
 a method for the preparation of a salt. It is an aid also in 
 the determination of the basic and acid parts of the salt. 
 The solubility of the salts and of the hydroxides of the metals 
 studied may be summarized as follows : 
 
 (1) Hydroxides are insoluble except those of ammonium, 
 sodium, potassium, and calcium. 
 
 (2) Nitrates are all soluble. 
 
 (3) Chlorides are soluble except silver chloride. Lead 
 chloride is slightly soluble in cold water and quite soluble 
 in hot water. 
 
 (4) Sulphates are soluble except those of lead and cal- 
 cium. Calcium sulphate is slightly soluble. 
 
 (5) Sulphides are insoluble except those of ammonium, 
 
 EV. CHEM. 16 
 
242 INORGANIC CHEMISTRY 
 
 sodium, potassium, calcium, and magnesium. The insoluble 
 sulphides can be divided into two classes : (a) Those soluble 
 in dilute acid, as lead and copper. (6) Those insoluble in 
 dilute acid, as iron, aluminum, and zinc. 
 
 (6) Carbonates, phosphates, and silicates are insoluble 
 except those of ammonium, sodium, and potassium. 
 
 273. Recognition of the Metals. In Chapter XX was 
 given a scheme for the recognition of the acid radicals of salts. 
 Consideration is now given to the methods of recognizing 
 the basic or metallic part of a salt. The methods given here 
 apply only to single substances, as the analysis of a mixture 
 of substances calls for a knowledge of analytical chemistry. 
 The tests will be confined to the ten of the more common 
 metallic elements studied : sodium, potassium, calcium, 
 magnesium, zinc, aluminum, iron, lead, copper, and silver. 
 
 (1) If the substance is one of those studied in connection 
 with Chapter XX and the acid radical has been determined, 
 some idea as to the metal may be gained by comparing with 
 the solubilities given above. For example, if the acid is 
 found to be carbonic or phosphoric acid and the substance 
 dissolves in water, the base must be ammonium, sodium, 
 or potassium ; if the substance is a chloride and is insoluble 
 in water, it must be silver chloride. An insoluble sulphate 
 must be lead or calcium, and so on. 
 
 (2) The usual method of detecting the metals is by the 
 use of reagents that precipitate certain groups of metals, 
 which may again be subdivided until the metal is traced. 
 The substance to be tested is dissolved in water. If it is 
 not soluble in pure water the least amount of nitric acid 
 should be used, and the following procedure carried out. 
 
 (a) Add to the solution a little hydrochloric acid. If 
 a precipitate is formed, it is silver chloride (268), or lead 
 
RECOGNITION OF THE COMMON METALS 243 
 
 chloride. Add ammonia water, which will dissolve silver 
 chloride. Lead chloride if present is not dissolved by am- 
 monia water but will dissolve if the liquid is heated. Con- 
 firm by test (252). 
 
 (6) If no precipitate is produced by hydrochloric acid, take 
 half of the solution and pass hydrogen sulphide gas through 
 it. A precipitate may be copper sulphide or lead sulphide. 
 The first solution may have been too dilute for the lead to 
 precipitate as chloride. Determine -[which is present by 
 testing original substance for lead (252) and copper (261). 
 
 (c) If no precipitation is caused by hydrogen sulphide, 
 make the solution alkaline by adding ammonia water. A 
 brownish precipitate is iron (244), while a white precipitate 
 indicates aluminum (230) or zinc (221). 
 
 (d) If none of these reagents gives a precipitate, evap- 
 orate the reserved half of solution to a small bulk and add a 
 few drops of sulphuric acid. A precipitate indicates calcium. 
 
 (e) If no precipitate is produced by the sulphuric acid, 
 make the solution alkaline with ammonia water and add a 
 solution of sodium phosphate. A precipitate indicates 
 magnesium. Confirm by testing the original substance (216). 
 
 (/) If none of these reagents produces a precipitate, the 
 substance is a salt of sodium or potassium. Determine 
 which by the flame test (131 and 210). 
 
 EXERCISE 
 
 Ex. 154. Obtain from the teacher samples of simple chemical 
 compounds to test for the metal or basic radical. Read this chapter 
 carefully and follow the outline exactly. The metal will be one of the 
 following : Sodium, Potassium, Calcium, Magnesium, Copper, Silver, 
 Lead, Zinc, Aluminum, or Iron. Make a record of the result of each test. 
 
 To the Teacher. This chapter should be made the basis of a thorough 
 review of the chemistry of the metals. 
 
PART II 
 ORGANIC AND APPLIED CHEMISTRY 
 
 CHAPTER XXIX 
 COMPOUNDS OF CARBON WITH HYDROGEN 
 
 274. REFERENCE has been made (107) to the known exist- 
 ence of many thousands of compounds containing carbon. 
 These compounds are for the most part produced as a result 
 of the vital processes of plants and animals ; hence the study 
 of their composition and properties is known as organic 
 chemistry. It was thought formerly that none of these com- 
 pounds could be produced artificially, but in recent years a 
 number of them have been prepared in the laboratory without 
 the aid of living things. While the old reason for making a 
 sharp distinction between inorganic and organic chemistry 
 no longer exists, it is still convenient to study the com- 
 pounds of carbon as a separate branch of chemistry, partly 
 because the number of compounds containing it exceeds the 
 number of all other compounds put together. It is well to 
 remember that many of the substances produced by plants 
 and animals have defied all attempts at artificial preparation, 
 and some of them, perhaps, will never be so produced. 
 
 275. Marsh Gas. When leaves or other organic matter 
 decompose under water, a gas is formed which, when collected 
 and examined, is found to be readily combustible. It is color- 
 less and odorless and about one half as heavy as air, with 
 
 244 
 
COMPOUNDS OF CARBON WITH HYDROGEN 245 
 
 which it forms an explosive mixture. It is called marsh gas, 
 or methane. It has the formula CH*. It is the simplest 
 member of a class of compounds consisting of carbon and 
 hydrogen in different propor- 
 tions, to which the general 
 name of hydrocarbons has 
 been given. 
 
 Methane is the chief con- 
 stituent of natural gas. It is 
 formed also to some extent 
 in coal mines, and the ex- 
 plosions occurring in these 
 mines are often due to a 
 mixture of air and methane. 
 Davy's Safety Lamp (100) 
 was invented to prevent these explosions. The miners call 
 methane fire damp. In the laboratory, marsh gas is pre- 
 pared by heating a mixture of sodium acetate and soda-lime : 
 
 NaC 2 H 3 2 + NaOH -> Na 2 CO 3 + CH4 
 
 (The lime does not enter into the reaction.) 
 276. Higher Hydrocarbons. More than one hundred 
 different combinations of carbon and hydrogen are known, 
 many of which are of great commercial importance. For 
 convenience in study these hydrocarbons , are arranged in a 
 number of groups or series. The following table gives the 
 names and formulas of a few of the hydrocarbons of the 
 methane series. 
 
 FIG. 129. Collection of marsh gas. 
 
 Methane - 
 
 Ethane - 
 
 Propane - 
 Butane 
 
 Pentane - 
 
 CH 4 
 C 2 H 6 
 C 3 H 8 
 C 4 H 18 
 
 Hexane - 
 Heptane - 
 
 Pentadecane 
 Hexadecane 
 
246 
 
 ORGANIC CHEMISTRY 
 
 The first four members are gases at ordinary tempera- 
 tures. From pentane to pentadecane (Ci 5 H 32 ) they are 
 liquids with higher boiling points, and from hexadecane up- 
 ward they are solids with increasingly higher melting points. 
 277. Petroleum is the principal source of the hydrocarbons 
 of the methane series. It is a thick, greenish-brown oil found 
 
 in oil-bearing strata of the 
 earth. The chief oil-pro- 
 ducing areas of the United 
 States are in Oklahoma, 
 California, Texas, Illinois, 
 Louisiana, West Virginia, 
 Pennsylvania, and Ohio. 
 Petroleum is pumped from 
 wells sunk in the ground, 
 and is stored in large tanks 
 or conveyed directly to the 
 refineries. Sometimes when 
 the oil is under great pres- 
 sure of gas, the newly driven 
 well spouts oil from the 
 surface. Such a well is 
 called a gusher (Fig. 130). 
 Petroleum is a very complex 
 mixture of hydrocarbons, 
 and while some of it is used 
 crude condition as 
 
 FIG. 130. -A spouting oil well or gusher. 
 
 a fuel, its principal value lies in the fact that it is the 
 source of many useful products such as gasoline, vaseline, 
 and paraffin. The crude petroleum is placed in large stills 
 and is subjected to distillation. The portion of the liquid 
 that distills between the temperatures of 70 degrees F. 
 
COMPOUNDS OF CARBON WITH HYDROGEN 247 
 
 and 150 degrees is called naphtha ; that between 150 and 
 300 is kerosene; while that which distills between 300 
 and 400 is used for lubricating oil. When the remaining 
 oil is chilled the solid constituents separate and consti- 
 tute ordinary paraffin. Naphtha is again separated into 
 petroleum ether, gasoline, and benzine. In some refineries 
 a semisolid fraction is also obtained which is the vaseline, 
 or petrolatum, of commerce. 
 
 None of these substances is a single chemical compound, 
 but each one is composed of several hydrocarbons. Gasoline 
 consists of hydrocarbons with low boiling points, while paraf- 
 fin contains those with very high boiling points. 
 
 278. Gasoline. The chief uses of gasoline depend upon 
 the fact that it is very volatile and is, therefore, easily con- 
 verted into a gas. The mixture of gasoline vapor and air is 
 explosive, and this quality is utilized in the gasoline engine. 
 When gasoline is used in heating or illuminating, it is first 
 converted into a gas. This is accomplished by heating it 
 or by forcing air through it. The volatile character of gaso- 
 line is also the cause of many accidents. It is to be noted 
 that nearly all the accidents with gasoline stoves have 
 been caused by the fact that the gasoline tanks were filled 
 while the burner was lighted. Gasoline is one of the best 
 solvents for fats and its use in cleaning depends upon this 
 fact. 
 
 279. Acetylene (C 2 H 2 ) is a colorless gas now extensively 
 used for illumination. It is prepared by the action of water 
 on calcium carbide (169) : 
 
 CaC 2 + 2 H 2 O *- Ca(OH) 2 + C 2 H 2 . 
 
 A special form of burner (Fig. 131) is required in burning 
 acetylene to prevent the formation of soot. When the gas 
 
248 
 
 ORGANIC CHEMISTRY 
 
 is used in such a burner the flame is very white and brilliant. 
 
 Acetylene is readily decomposed, and it was formerly dan- 
 gerous to handle when compressed in 
 cylinders. It has been discovered 
 that if the cylinder is filled with a 
 porous material like asbestos and this 
 material is saturated with a com- 
 pound called acetone, acetylene may 
 be forced into the cylinder under high 
 pressure with perfect safety. Acety- 
 lene, when burned with oxygen in an 
 apparatus much like the oxyhydrogen 
 blowpipe, makes the hottest known 
 flame (2700). It is sometimes used 
 in cutting iron, as it melts its way 
 through the iron at the point of 
 
 FIG. 131. Acetylene burner, contact. 
 
 EXERCISES 
 
 Ex. 155. Mix thoroughly a teaspoonful each of sodium acetate and 
 soda-lime. Place in a test tube, arrange as in Fig. 50, and heat. Collect 
 two bottles full of the gas. What is the composition of this gas? 
 The name ? The reaction ? Ascertain whether the gas will burn. Fill 
 a bottle half full of the gas and half full of air and ignite it. Does 
 this mixture explode ? Where is this gas found in nature ? What do 
 miners call it ? If there is a marsh or a pond near the school where 
 leaves and other organic matter are decomposing, try to collect some 
 methane as shown in Fig. 129. Why is this gas commonly called 
 marsh gas ? 
 
 Ex. 156. What is meant by a hydrocarbon ? Are many combina- 
 tions of carbon and hydrogen known ? As the number of carbon atoms 
 in the molecule increases what effect does it have on the boiling point of 
 the hydrocarbon? Are the hydrocarbons with the largest molecules 
 liquids or solids? 
 
COMPOUNDS OF CARBON WITH HYDROGEN 249 
 
 Ex. 167. Examine a sample of crude petroleum ; also samples of 
 gasoline, kerosene, and lubricating oil. What is the original source of 
 all these substances ? What is the chemical nature of petroleum ? 
 Are gasoline and kerosene single chemical compounds? In which do 
 the hydrocarbons have the larger molecules? What are some of the 
 important uses of gasoline ? For what is it used at your home ? 
 
 Ex. 158. Place some calcium carbide in an apparatus as shown in j 
 Fig. 132. The bulb (B) contains water and is fitted with a stopcock so 
 that the water can be slowly 
 run into the flask (A). When 
 ready to collect the gas allow 
 the water to run into the flask 
 a drop at a time. Examine 
 the gas which is evolved. 
 What is its name and for- 
 mula? Give its reaction of 
 formation. Why must it be 
 burned in a special burner ? 
 Are any houses in your 
 neighborhood lighted with 
 acetylene? What gas is in the gas tanks used on automobiles and 
 motorcycles? What temperature is obtained where acetylene is 
 burned with oxygen? What practical application is made of this 
 intense heat ? 
 
 FIG. 132. Laboratory apparatus for the 
 production of acetylene. 
 
CHAPTER XXX 
 ALCOHOLS 
 
 280. Wood Alcohol. When wood is heated in closed 
 retorts in the manufacture of charcoal (90), a distillate con- 
 sisting of a number of substances is obtained. One of these 
 compounds is wood alcohol (methyl alcohol), which* has the 
 formula CH 3 OH. Wood alcohol is a colorless liquid that 
 boils at 65 C. and burns with a colorless and sootless flame. 
 It is a good solvent for resins and is used in making certain 
 varnishes and shellacs. It is burned also in alcohol lamps, 
 although its use for this purpose and for varnishes has de- 
 creased since the introduction of denatured alcohol. Wood 
 alcohol is poisonous and it produces paralysis of the optic 
 nerve. Many cases of blindness have been caused by the 
 drinking of cheap whiskies adulterated with wood alcohol, 
 and by the continued inhaling of its vapor. 
 
 281. Ordinary alcohol, also known as grain alcohol and 
 ethyl alcohol, has the formula C 2 H 5 OH. It is obtained from 
 the fermentation of sugars. The fermentation is brought 
 about by the action of yeast. In the case of grape sugar 
 (CeHtfOe) the reaction may be represented as follows : 
 
 C 6 H 12 O 6 ->- 2 C 2 H 5 OH + 2 CO 2 . 
 
 Alcohol is prepared commercially from substances rich in 
 starch, such as corn or potatoes. The starch is first con- 
 verted into a sugar by means of malt, and yeast is then added. 
 
 250 
 
ALCOHOLS 
 
 251 
 
 Water 
 
 Yeast is a microscopic vegetable organism, which during its 
 growth produces a number of changes resulting in converting 
 the sugar into alco- 
 hol. The resulting 
 alcohol is separated 
 from the fermented 
 liquid by distillation 
 (Fig. 133). The al- 
 cohol of commerce 
 contains about 5 per 
 cent of water. 
 
 Alcohol is a color- 
 less liquid with a 
 characteristic, pleas- 
 ant odor. It boils at 
 
 78 C. It is Some- FIG. 133. A stUl for the production of alcoholic 
 
 times used as a fuel, liquors. 
 
 especially in spirit lamps, as it burns with a colorless and 
 
 sootless flame. It burns according to the following reaction : 
 
 C 2 H 5 OH + 6 O -^ 2 CO 2 + 3 H 2 O. 
 
 It is a solvent for many substances. Pharmacists use it in 
 the preparation of tinctures, essences, and extracts. Many 
 of the better grades of varnishes and shellacs contain ethyl 
 alcohol. When the term alcohol is used without a qualify- 
 ing word, ethyl alcohol is always meant. When taken into the 
 system in small quantities, alcohol produces intoxication; 
 in larger amounts it acts as a more positive poison. 
 
 282. Alcoholic Beverages. Many beverages contain al- 
 cohol in greater or smaller quantity (Fig. 134). In all cases 
 the alcohol is produced by fermentation. Wines are made 
 by the fermentation of the sugars in fruit juices, particu- 
 
252 
 
 ORGANIC CHEMISTRY 
 
 FIG. 134. The percentage of alcohol in distilled 
 liquor, wine, and beer. 
 
 larly of the grape. Wines contain 5 to 15 per cent of 
 alcohol. Hard cider is really a wine produced from apple 
 juice. The yeast plant, since it is always associated with 
 
 the fruits, need not be 
 added in wine making. 
 Beer is made by the 
 fermentation of malt; 
 in this case the yeast is 
 added. Beer contains 
 from 3 to 5 per cent of 
 alcohol. Corn, rice, 
 and glucose are some- 
 times used to replace 
 part of the malt. 
 Whisky, brandy, rum, and gin are known as distilled 
 liquors. They contain from 40 to 60 per cent of alcohol. 
 Whisky is made by distilling a beer made from rye, corn, or 
 barley. Brandy is maole by distilling wine, or the fermented 
 juice of apples, peaches, cherries, or other fruits. Rum is 
 distilled from the liquid obtained by fermenting molasses. 
 Gin is an alcoholic liquor flavored with oil of juniper berries. 
 
 283. Denatured alcohol is ethyl alcohol, to which is added 
 wood alcohol, benzine, or a bad-smelling compound prepared 
 by heating bones and known as pyridine. These substances 
 make its use for beverages or medicine impossible. About 
 four fifths of the cost of ordinary alcohol is due to the internal 
 revenue tax imposed by the government. Denatured alcohol 
 is tax free, to encourage its use in the arts. The denaturing 
 in no way impairs its value as a fuel or for use in varnishes 
 and shellacs. 
 
 284. Alcohols Are Bases. The formulas for methyl alcohol 
 (CH 3 OH) and ethyl alcohol (QjHsOH) are written in such 
 
ALCOHOLS 253 
 
 a way as to show the presence of hydroxyl in the compound. 
 This is done because the alcohols are all bases in the same way 
 that ammonium hydroxide (NHjOH) is a base, although the 
 basic character of the alcohols is less pronounced. They 
 react with acids in a manner similar to ammonium hydroxide : 
 
 NH 4 OH + HC1 -*- H 2 O + NH 4 C1 (ammonium chloride) ; 
 C 2 H 5 OH + HC1 ->- H 2 O + C 2 H 5 C1 (ethyl chloride). 
 
 Methyl and ethyl alcohols are hydroxides made by re- 
 placing one hydrogen atom of methane and ethane with 
 hydroxyl. Similar alcohols can be prepared corresponding 
 to the more complex hydrocarbons, but most of them are of 
 minor importance. 
 
 285. Glycerin. Just as there are inorganic bases with more 
 than one hydroxyl group in the molecule, as, for example, 
 Ca(OH) 2 and A1(OH) 3 , so there are alcohols with more than 
 one hydroxyl group. The most important of these is glycerol, 
 known commercially as glycerin, C 3 H 5 (OH) 3 . Glycerin is 
 a heavy, colorless, sirupy liquid with a sweet taste. It is 
 miscible with water and is so hygroscopic that it will absorb 
 half its weight of water from the moisture, of the air. It is 
 used in cosmetic and medicinal preparations, in ink rollers 
 of printers, in the ink for rubber stamps, and to soften leather. 
 Glycerin is one of the products obtained during the manu- 
 facture of soap (303), and in the preparation of the stearin 
 used in making candles. 
 
 286. Nitroglycerin is trinitrate of glycerin, made by slowly 
 adding glycerin to a mixture of nitric and sulphuric acids : 
 
 C 3 H 5 (OH) 3 + 3 HN0 3 -> C 3 H 5 (N0 3 ) 3 + 3 H 2 O. 
 
 The sulphuric acid does not take part in the reaction, but 
 causes the action to continue by keeping the mixture dehy- 
 
254 ORGANIC CHEMISTRY 
 
 drated. Nitroglycerin is a heavy, colorless, oily liquid. 
 It explodes when heated to 180 C., or when subjected to a 
 shock. Because of the danger in handling pure nitroglycerin, 
 it is mixed with some inert, porous substance, such as 
 infusorial earth or wood pulp. This mixture is called dyna- 
 mite, and the different grades are classified and named accord- 
 ing to the percentage of nitroglycerin they contain. 
 
 287. Formaldehyde. When methyl alcohol is burned in 
 a limited supply of air, or the mixture of air and the vapor of 
 methyl alcohol is passed over heated copper, a gas is formed 
 which is known as formaldehyde (CH 2 O) : 
 
 CHsOH + O -*- CH 2 O + H 2 O. 
 
 Formaldehyde is a gas with a stinging, stifling odor which 
 causes the eyes to smart. It is a powerful germicide and is 
 largely used to disinfect buildings following cases of conta- 
 gious diseases. It is more effective than sulphur dioxide and 
 has no bleaching effect (63). An aqueous solution contain- 
 ing 40 per cent of the gas is sold under the name of formalin. 
 This is used also as a disinfectant, and for the treatment of 
 seed potatoes for the destruction of scab, and of oats and 
 other grain to destroy smut. Formaldehyde is used also 
 lor the preservation of anatomical specimens and to harden 
 gelatin films in photography. It is sometimes improperly 
 ' employed as a food preservative. 
 
 EXERCISES 
 
 Ex. 159. (Teacher) Place a cupful of commercial glucose, com- 
 mon molasses, or Karo sirup, in a two quart bottle (A) and add a 
 quart of lukewarm water. Rub a cake of compressed yeast in half 
 a cupful of water and add it to the mixture in the bottle. Connect 
 the large bottle with a small bottle (B) containing limewater, as shown 
 
ALCOHOLS 
 
 255 
 
 FIG. 135. Producing alcohol in 
 the laboratory. 
 
 in Fig. 135. Set this aside in a warm place for two or three days. 
 
 Bubbles of gas will soon form in A and pass into B. What happens 
 
 to the limewater? What is the gas 
 
 formed in A ? After fermentation has 
 
 ceased, decant about half of the liquid 
 
 in A into a distilling flask. 1 Connect 
 
 with a condenser and distill off 10 to 
 
 15 cc. Compare the odor with the 
 
 alcohol of the laboratory. Put 2 or 3 cc. 
 
 in an evaporating dish and test it with 
 
 the flame. Will it burn? 
 
 Ex. 160. State the properties of ordinary alcohol. What is its 
 chemical name ? How is it made ? Write the reaction for change of glu- 
 cose to alcohol. Name some beverages that contain alcohol. What 
 uses are made of alcohol? What is meant by denatured alcohol? 
 Why is denatured alcohol so much cheaper than the pure alcohol? 
 Does denaturing impair its value for use in the arts ? 
 
 Ex. 161. How is wood alcohol prepared? What is the chemical 
 name for wood alcohol ? For what is it used ? Why is caution neces- 
 sary in using it ? Why are alcohols known as bases ? 
 
 Ex. 162. Examine a sample of glycerin and give its properties; 
 its formula. For what is it used ? What is the source of commercial 
 glycerin ? How is nitroglycerin made ? Write the reaction. What is 
 dynamite ? 
 
 Ex. 163. Examine a sample of formaldehyde. How is it prepared ? 
 Give its formula. For what is it used ? Why is it .preferable to sulphur 
 dioxide for disinfecting after sickness ? 
 
 1 Set the bottle A aside and keep it open for two or three weeks to see 
 whether acetic acid will develop. 
 
CHAPTER XXXI 
 ORGANIC ACIDS 
 
 288. Acetic Acid. It will be recalled that apple juice, upon 
 standing, undergoes a fermentation that results in the forma- 
 tion of alcohol. Hard cider may contain from 4 to 8 per cent 
 of alcohol. Upon longer standing the cider becomes very 
 sour and is then called vinegar. The sour taste of the 
 vinegar is due to the fact that the alcohol has been changed 
 into a substance known as acetic acid (H 
 
 C 2 H 6 OH + 2 O -- H C 2 H 3 O 2 + H 2 O. 
 
 This acid is the most familiar member of a class of compounds 
 known as organic adds. All of them resemble the inorganic 
 acids in their general behavior, but are weaker acids. Only 
 one of the hydrogen atoms of acetic acid has acid properties, 
 that is, can be replaced by a metal ; and that fact is indicated 
 in the formula by separating the replaceable hydrogen from 
 the rest of the molecule. This method of indicating the 
 replaceable hydrogen atoms of the organic acids is used 
 throughout this text. 
 
 The change of alcohol into acetic acid during the forma- 
 tion of vinegar is brought about by the action of a species of 
 bacteria known as Bacterium aceti, and the change is known as 
 acetic fermentation, which is evidently an oxidation process. 
 The slimy substance sometimes found in* vinegar and called 
 mother of vinegar consists of masses of these bacteria. Vine- 
 gar contains from 4 to 6 per cent of acetic acid. 
 
 256 
 
ORGANIC ACIDS 
 
 257 
 
 The old method of producing vinegar from cider, in which 
 the fermentation was allowed to take place in barrels, re- 
 quired many weeks or months, as the oxidation could take 
 place only at the surface of the 
 liquid. In the method known as 
 the quick vinegar process (Fig. 136), 
 tall barrels are loosely filled with 
 beech-wood shavings, which are 
 then moistened with old vinegar to 
 introduce the bacteria. The cider 
 or other liquid containing alcohol 
 is allowed to trickle slowly over the 
 shavings and is thus exposed to the 
 action of bacteria and to the oxy- 
 gen of the air. By this process the 
 vinegar is produced in about ten 
 days. Vinegars are sometimes 
 made from wine, and from fer- 
 mented malt extract (malt vinegar). FIG. 136. vinegar-making by 
 
 f quick process. 
 
 White wine vinegar, or distilled vine- 
 gar, is made by treating solutions of pure alcohol by the 
 process just described. 
 
 289. Acetic Acid from Wood. Acetic acid is one of the 
 products of the destructive distillation of wood (90) . It was 
 formerly called " pyroligneous acid " ; that is, the acid made 
 by heating wood. Much of the acetic acid on the market is 
 made in this way, and some of the cheap vinegar is merely 
 a 4 per cent solution of this acid. 
 
 Acetic acid, when pure, is a colorless liquid with a pungent 
 odor. It solidifies at 17 C. and is soluble in all proportions 
 in water. With metals it forms salts, among the most im- 
 portant of which are sodium acetate (NaC 2 H3()2), and lead 
 
 EV. CHEM. 1? 
 
^58 ORGANIC CHEMISTRY 
 
 acetate (Pb(C 2 H 3 O2) 2 ) commonly called sugar of lead. 
 Copper acetate (Cu(C 2 H 3 O) 2 ) when combined with copper 
 arsenite forms Paris green (260). 
 
 290. Lactic Acid. Milk upon standing gradually becomes 
 sour because of the formation of lactic acid (H-CsHsOa). 
 This acid is produced by the action of lactic-acid bacteria 
 upon milk sugar (310). This process is known as lactic fer- 
 mentation. Lactic acid may also be prepared by the fermen- 
 tation of other sugars, and as it is now of some industrial 
 importance it is produced by the action of the bacteria found 
 in old cheese, upon solutions of glucose, or cane sugar. 
 When pure, it is a colorless, sirupy liquid with an intensely 
 sour taste. 
 
 291. Oxalic acid (H 2 -C 2 O 4 ) exists in many plants. It 
 gives the sour taste to sour grass and to sheep sorrel. 
 It differs from most of the acids so far studied in being 
 a solid instead of a liquid. It forms large, colorless crys- 
 tals containing two molecules of water of crystallization 
 (H 2 C 2 O 4 2 H 2 O) . Oxalic acid is poisonous. Its antidote is 
 calcium carbonate (chalk), which forms with it the insoluble 
 calcium oxalate (CaC 2 O 4 ). Calcium oxalate is found in the 
 clovers and many other plants. Oxalic acid is useful in 
 removing ink and rust spots from floors and fabrics. It is 
 used also in cleaning brass, and in bleaching straw hats. 
 
 292. Tartaric acid (H 2 -C 4 H 4 O 6 ) is the acid of grapes. 
 When pure it forms beautiful, large, prismatic crystals which 
 are readily soluble in water. In grapes it is found as acid 
 potassium tartrate (KH-C 4 H 4 O 6 ). This is the substance, 
 commonly called cream of tartar. When a solution of cream 
 of tartar is neutralized with sodium hydroxide, Rochelle salt 
 (KNaC 4 H 4 O 6 ) is formed : 
 
 KHC 4 H 4 O 6 + NaOH + KNaC 4 H 4 O 6 + H 2 O. 
 
ORGANIC ACIDS 259 
 
 293. Citric acid (H 3 -C 6 H 5 O 7 ) occurs in lemons, oranges, 
 and other citrus fruits. It exists also in currants, gooseberries, 
 and cranberries. Citric acid forms large colorless crystals 
 which are soluble in water. Both citric and tartaric acid are 
 often used as substitutes for lemons in making cheap lemon- 
 ade and other acidulated beverages. Magnesium citrate 
 (Mg3(C6H 5 O 7 )2) is employed as a purgative in medicine. 
 
 294. Tannic acids, or tannins, are substances with an 
 astringent taste. They are widely distributed in the vege- 
 table kingdom. The principal commercial sources are the 
 bark of the oak and hemlock, sumach, nutgalls, and a num- 
 ber of Indian and South American trees. Tannins occur also 
 in smaller quantities in the leaves of many plants. Tannins 
 are used for tanning leather, in dyeing, and in making ink. 
 
 Ink is the black mixture obtained by mixing solutions of 
 tannin with iron salts. One recipe for black ink is as follows : 
 Extract 100 grams of powdered nutgalls with 1.4 liters of 
 water, and add 50 grams of gum arabic and 50 grams of fer- 
 rous sulphate. When the mixture is exposed to the air, a 
 permanent black color is developed. A black or a blue dye 
 is commonly added to give the ink a temporary color. 
 
 The operation of tanning, or the conversion of animal skin 
 into leather, depends on the formation in the skin of an in- 
 soluble compound of tannin and the albuminoid matter of 
 the skin. The tannin is derived from -oak or hemlock 
 bark, which is ground to a coarse powder and piled in 
 layers with the skins in deep vats. The vats are filled with 
 water, and the skins are allowed to soak for a few weeks or 
 months. 
 
 295. Benzoic acid (H-C 7 H 5 O 2 ) and salicylic acid 
 (H-C 7 H 5 O 3 ) are both solid, crystalline acids that are used 
 in medicine and sometimes as preservatives in food. Benzoic 
 
260 ORGANIC CHEMISTRY 
 
 acid exists naturally in gum benzoin, while a compound of 
 salicylic acid is the principal ingredient of oil of wintergreen. 
 Both these acids are now prepared artificially from coal tar 
 compounds. 
 
 Sodium benzoate (NaC7H 5 O 2 ), is frequently used as a 
 preservative in foods. Its use is unnecessary, however, and 
 should be discouraged. Sodium salicylate also is sometimes 
 used as a preservative. Both it and salicylic acid are used in 
 medicine, notably in the treatment of rheumatism. 
 
 296. Organic Salts, or Esters. If to a mixture of ethyl 
 alcohol and acetic acid in a test tube a little sulphuric acid is 
 added and the whole is gently heated, a vapor with a pleas- 
 ant, fragrant odor is given off. This body, ethyl acetate 
 (C 2 H 5 -C 2 H 3 O 2 ), is formed by replacing the acid hydrogen of 
 acetic acid by the basic ethyl radical. The equation is 
 
 C 2 H 5 OH + H . C 2 H 3 O 2 -> C 2 H 5 - C 2 H 3 2 + H 2 O. 
 
 The sulphuric acid absorbs the water as fast as it is formed 
 and permits the reaction to continue. Such salts as ethyl 
 acetate, in which both the basic and the acid parts are organic 
 radicals, are called ethereal salts or esters, the shorter name 
 being preferred. Many of these esters exist naturally in 
 fruits and impart *to them their characteristic flavors. They 
 can be prepared artificially by a process analogous to that 
 discussed for ethyl acetate and many of the flavoring extracts 
 on the market consist of such artificially prepared esters. 
 Oil of wintergreen is methyl salicylate (CH 3 -C7rI 5 O 3 ). 
 Most of the oil of wintergreen on the market is artificial. 
 
 When an ester is gently heated with an alkali, the alkali 
 salt of the acid is formed and the alcohol is set free : 
 
 C 2 H 3 O 2 + NaOH -- NaC 2 H 3 O 2 + C 2 H 5 OH. 
 
 ethyl acetate sodium acetate ethyl alcohol 
 
ORGANIC ACIDS 261 
 
 The esters are also decomposed by heating with steam under 
 pressure into the acid and alcohol : 
 
 C 2 H 5 -C 2 H 3 O 2 + H 2 0-^C 2 H 5 OH + H-C 2 H 3 O 2 . 
 
 ethyl acetate alcohol acetic acid 
 
 EXERCISES 
 
 Ex. 164. What gives the sour taste to vinegar? How is vinegar 
 made commercially? What is meant by the quick vinegar process? 
 Write the reaction for change of alcohol to acetic acid. Give the prop- 
 erties of acetic acid ; the formula. How is acetic acid prepared from 
 wood ? What was the old name for it ? Make a four per cent solution 
 of acetic acid and compare the flavor with cider vinegar. Is the flavor 
 of a good vinegar entirely due to the acetic acid ? 
 
 Ex. 165. What acid is formed when milk sours? Can you prove 
 that an acid is present ? Examine the laboratory sample of lactic acid. 
 Add a drop to a tablespoonful of water and taste it. 
 
 Ex. 166. Examine some crystals of oxalic acid. Where is it found 
 in nature ? Try cleaning an old straw hat with a solution of oxalic 
 acid. Rub the solution on with a sponge or a piece of cloth and place 
 the hat in the sun. 
 
 Ex. 167. Examine some cream of tartar. What is the source of 
 cream of tartar? The formula? Examine crystals of tartaric acid. 
 Give its formula. What is formed when cream of tartar is neutralized 
 with sodium hydroxide ? 
 
 Ex. 168. To what acid is the sour taste of lemons due? What is 
 the appearance of citric acid ? In what other fruits is it found ? How 
 is cheap lemonade made ? 
 
 Ex. 169. Examine some tannic acid. Dissolve a little in water 
 and taste a drop. Does it have an astringent taste ? Where is it found 
 in nature ? Add a little tannic acid solution to a solution of ferric chlo- 
 ride. What is the result ? Steep a little oak bark in water and, add ferric 
 chloride to the solution. Do the same with a little tea. Have you any 
 evidence that oak bark and tea contain tannic acid ? -How is ink made ? 
 Why does it get darker when exposed to the air ? How is tannic acid 
 used in tanning leather ? Soak a piece of lean meat in a strong solu- 
 tion of tannic acid for a few days. What is the condition of the meat ? 
 
262 ORGANIC CHEMISTRY 
 
 Ex. 170. Examine bottles of factory-made catsup or other foods at 
 home or in the local store and see whether any have stated on the label 
 that sodium benzoate was used in their manufacture. Do you think 
 any preservative should be used in canning vegetables or fruits ? 
 
 Ex. 171. Place 1 cc. each of alcohol and acetic acid in a test tube. 
 Add 2 cc. of sulphuric acid and warm the mixture. Note the pleasant 
 odor evolved. What is this substance ? What is the general name for 
 such compounds ? How are they sometimes used ? 
 
 Ex. 172. Place a little wood alcohol and some salicylic acid in 
 a test tube. Add sulphuric acid and warm. What odor is given off? 
 What is the chemical composition of oil of wintergreen ? What happens 
 to esters when heated with an alkali ? When heated with steam under 
 pressure ? 
 
CHAPTER XXXII 
 FATS, OILS, AND SOAPS 
 
 297. Fats and oils are the products of both vegetable 
 and animal life. Oils are liquid fats. The more common 
 animal fats are tallow, lard, and butter. Olive oil, palm oil, 
 cottonseed oil, and linseed oil are good examples of vegetable 
 fats. These fats are all insoluble in water. They are 
 soluble in ether, chloroform, carbon bisulphide, gasoline, and 
 benzine. Hence water will not remove grease spots from 
 clothing, but benzine and other solvents of fats will. 
 
 298. Composition of Fats. When a fat is heated with 
 steam under pressure so as to get a temperature of about 
 200 C. it is decomposed with the formation of glycerin (285) 
 and one or more organic acids. The acids more commonly 
 found in fats are palmitic acid (H CieH 3 iO 2 ) ; stearic acid 
 (H-Ci 8 H 35 O 2 ); and oleic acid (H-Ci 8 H 33 O 2 ). These and 
 other acids found in fats are collectively known as fatty adds. 
 Fats, then, are evidently esters in which the alcohol is glyc- 
 erin and the acid is one of the so-called fatty acids. As 
 glycerin has three hydroxyl groups, its ester with stearic acid 
 must have the formula CsHs^igHssO^?. (Compare with 
 glycerin nitrate (286).) The hydrolysis of glycerin stearate 
 may be represented as follows : 
 
 C 3 H 5 (C 18 H350 2 )3 + 3 H 2 O ^ C 3 H 5 (OH) 3 + 3 H.C 18 H 35 O 2 . 
 
 glycerin stearate glycerin stearic acid 
 
 The glycerin of commerce and many of the fatty acids used in 
 candle and soap making are produced in this way. 
 
 263 
 
264 ORGANIC CHEMISTRY 
 
 The names of the different fats are derived from those of 
 the fatty acids found in them, by changing the ic of the acid 
 to in. Thus the glycerin ester (or fat) of palmitic acid is 
 called palmatin (*Hk(QftHfiQz)*) ; of stearic acid is stearin 
 (C 3 H 5 (C 18 H 35 2 )3) ; of oleic acid, olein (C 3 H 5 . (C 18 H 3 3O 2 ) 3 ). 
 Stearin and palmitin are solids, while olein is a liquid. The 
 natural fats are nearly always mixtures of the different 
 single fats, and the consistency of the fat depends upon the 
 proportion of the different esters present. Beef tallow is a 
 mixture of stearin, palmitin, and olein, with the more solid 
 stearin predominating. Olive oil and cottonseed oil contain 
 large proportions of olein and are therefore liquid. 
 
 299. Butter and Oleomargarine. Butter contains from 
 80 per cent to 85 per cent of a very complex fat consisting of 
 several of the glycerin esters with olein and palmatin pre- 
 dominating. The characteristic flavor of the butter fat, 
 however, is due to the presence of about 5 per cent of butyrin 
 (C 3 H5(C 4 H 7 O2) 3 ), which is the salt of butyric acid (H C 4 H 7 O 2 ). 
 This fat occurs only in butter, and the methods of distinguish- 
 ing true from adulterated butter depend upon this fact. 
 
 The high price of butter has led to the manufacture of 
 certain butter substitutes. Oleomargarine is made from 
 various animal fats, combined with cottonseed, peanut, and 
 palm oils, the different fats being nrxed in such proportions 
 as to give a substance of about the same consistency as butter 
 fat. To give the product a butter flavor, the melted fat is 
 poured into ripened milk, that is, milk that has been soured 
 as cream is in butter making, and is then churned. In 
 butterine a certain proportion of butter fat is added to impart 
 the butter flavor. 
 
 While oleomargarine is a valuable food product, the 
 temptation to sell it for butter has proved so great that 
 
FATS, OILS, AND SOAPS 265 
 
 strict laws regulating its sale are required. Oleomargarine 
 colored to resemble butter is taxed ten cents a pound by the 
 United States government, and the sale of colored oleo- 
 margarine is entirely prohibited in some states. The fraud- 
 ulent substitution of other fats for butter fat is the more 
 reprehensible in view of the recent discovery that butter fat 
 contains certain growth-producing substances, called vita- 
 mines, which are not found in lard and vegetable fats. 
 
 300. Renovated Butter. Much of the butter placed on 
 the market becomes strong or rancid, and the " renovating " 
 of this butter has become an important industry. The 
 butter is melted and the curd and the water are removed 
 as well as the scum on the top. Air is then forced through 
 the melted fat until the disagreeable odors are removed 
 and the fat is nearly tasteless. The fat is then churned 
 with ripened milk as in the case of oleomargarine. 
 
 301. Making Solid Fats from Oils. A comparison of the 
 formulas of the liquid fat olein and the solid fat stearin shows 
 that the latter contains six more hydrogen atoms than olein. 
 By treating olein with hydrogen in the presence of finely 
 powdered nickel, which acts as a catalytic agent, it can be 
 made to absorb hydrogen and thus be changed into stearin. 
 This process is known as hydrogenation of ails. A number of 
 edible lard substitutes are made by hydrogenating cotton- 
 seed oil until it has the consistency of lard. 
 
 Hydrogenation has proved of great value also in soap 
 making. Oils that give soft soaps can be converted into 
 compounds that yield the more valuable hard soaps. Fish 
 oils, which have objectionable odors, can by this process 
 be deodorized and made suitable for soap making. 
 
 302. Drying Oils. Linseed oil consists largely of the fat 
 having the formula C 3 H 5 (Ci8H 3 iO2)3. This fat is linolein, 
 
266 ORGANIC CHEMISTRY 
 
 the glycerin salt of linoleic acid (H'CigHsiC^). It will be 
 noted that linolein has twelve fewer hydrogen atoms in the 
 molecule than stearin. It has the property of absorbing 
 oxygen from the air and thereby of being changed into a hard, 
 solid substance. For this reason linseed oil is called a drying 
 oil and it is this property that makes it valuable for use in 
 paint making. A few other oils, for example, poppyseed oil 
 and corn oil, have this property of drying in a less marked 
 degree than linseed oil. 
 
 303. Soaps. All esters are decomposed when heated with 
 the hydroxides of the alkalies. With stearin and sodium 
 hydroxide the reaction is 
 
 3 NaOH->C 3 H 5 (OH) 3 + 3 NaC 18 H 3 50 2 . 
 
 glycerin stearate glycerin sodium stearate 
 
 Sodium stearate is a soap. Reactions like the above may 
 be made to take place between all fats and the hydrox- 
 ides of sodium or potassium, and in each case a soap is 
 formed. Soaps, therefore, may be said to be the sodium 
 or potassium salts of the fatty acids. Sodium soaps are 
 known as hard soaps, while those containing potassium are 
 soft soaps. 
 
 In soap making the lye solution is gradually added to the 
 oil or melted fat, which is kept warm and stirred by jets of 
 steam. When the reaction appears to be complete, salt is 
 added to the mixture and the soap separates and floats on 
 top, as it is insoluble in a solution of salt. This process is 
 called salting out. In this method of making soap most of 
 the glycerin remains in the solution with the salt and spent 
 lye and is hard to recover. In the old fashioned homemade 
 soft soap (Fig. 137) the alkali used is potassium carbonate 
 obtained by leaching wood ashes. The potassium is present 
 
FATS, OILS, AND SOAPS 
 
 267 
 
 in plants as the salts of organic acids, but all alkali salts of 
 organic acids are changed to carbonates when burned : 
 
 -f O -> K 2 CO 3 + CO 2 . 
 
 The larger soap factories first hydrolyze the fats with 
 superheated steam, and a part of the liberated fatty 
 acids are treated with so- 
 dium hydroxide to make 
 the soap. The reaction 
 between an alkali and a 
 fat resulting in the pro- 
 duction of a soap is 
 known as saponification. 
 
 Calcium and magne- 
 sium salts of the fatty 
 acids are insoluble in 
 water, and these insoluble 
 salts are formed when 
 soap is added to hard 
 water (119). As these 
 insoluble compounds have 
 no cleansing power, that 
 part of the soap which 
 
 reacts with the calcium and magnesium of hard water is 
 wasted. The methods of determining hardness of water 
 depend on the fact that a lather is not produced in water 
 until all of the calcium and magnesium is precipitated (16). 
 
 304. Essential Oils. Many plants contain so-called 
 essential or volatile oils which impart to them their char- 
 acteristic taste or odor. These substances are not true oils 
 and vary in character according to the source. They are 
 completely volatilized when heated and leave no permanent 
 
 FlG 137 _ Making soft soap on the farm 
 
268 ORGANIC CHEMISTRY 
 
 greasy residue on cloth or paper. Oil of lemon, oil of pepper- 
 mint, and oil of cedar are examples of essential oils. The 
 odor of new-mown hay is due to a volatile oil. The clovers, 
 particularly sweet clover, have characteristic essential oils. 
 These oils are lost when the hay is overcured or exposed to 
 leaching rains. Some of the essential oils of foods exert a 
 favorable influence on digestion by imparting palatability 
 to the food and stimulating the flow of the digestive fluids. 
 Some of the essential oils have medicinal value, while others, 
 as oil of bitter almonds, are poisonous. 
 
 EXERCISES 
 
 Ex. 173. Name some of the common fats found in plants and 
 animals. What is produced when fat is heated with steam under pres- 
 sure? Do fats always consist of glycerin united with one or more 
 fatty acids ? What are the three most common fatty acids ? How are 
 the fats themselves named ? Name the three most common fats. Do 
 natural fats consist of one of these fats or of a mixture of two or more ? 
 
 Ex. 174. What gives the characteristic flavor to butter fat ? Does 
 this substance occur in any other natural fat ? What is oleomargarine ? 
 How is the flavor of butter given to it? What is renovated butter? 
 
 Ex. 176. Write out the formulas for olein and stearin. How many 
 more hydrogen atoms are there in stearin than in olein ? Can hydro- 
 gen be added to olein ? What is this process called ? Name a product 
 that is so prepared. Of what value is hydrogenation in soap making? 
 
 Ex. 176. (Teacher) Place 20 grams of lard in an evaporating dish 
 or a granite-ware cup and warm to melt the lard. Dissolve 10 grams of 
 sodium hydroxide in about 40 cc. of water. Add the solution slowly 
 to the melted fat. Heat gently, with constant stirring, until a few drops 
 of the mixture dissolve completely in clear water leaving no globules of 
 fat. When the mixture is cool, add a strong solution of salt and the soap 
 will separate and rise to the top, where it will finally solidify. 
 
 Ex. 177. Explain the changes which take place in soap making. 
 Dissolve some of the soap in water and add hydrochloric acid. The 
 material which floats on the top consists of the fatty acids which were 
 
FATS, OILS, AND SOAPS 269 
 
 present in the lard and the soap. To another portion of the soap solu- 
 tion add a solution of calcium chloride. What is the curd in this case ? 
 Why is more soap necessary with hard water than with soft water ? 
 
 Ex. 178. (Teacher) Half fill a liter distilling flask with chopped 
 green leaves of peppermint, spearmint, wild bergamot, or sweet clover, 
 and add 200 cc. of water. Connect with a condenser and distill until 
 the receiving flask contains about 50 cc. of liquid. A few drops of the 
 essential oil will be found floating on the water. 
 
CHAPTER XXXIII 
 CARBOHYDRATES 
 
 305. THE compounds that are produced most abundantly 
 by growing plants are substances which contain carbon com- 
 bined with hydrogen and oxygen, the latter two being present 
 in the proportion in which they are found in water. Because 
 of this relation between the hydrogen and oxygen these com- 
 pounds are collectively known as carbohydrates. Their 
 importance will be realized when it is said that this group 
 includes the sugars, starches, woods, and all plant fibers. 
 
 ,306. Grape sugar, or glucose, as its name signifies, is the 
 sugar found naturally in grapes. The whitish efflorescence 
 on raisins and dried figs is glucose. When dry, glucose is a 
 waxy mass that can be made to crystallize only with great 
 difficulty. It is sweet to the taste, but its sweetening power 
 is only about three fifths that of cane sugar. It occurs in 
 many fruits. Commercially glucose appears as a heavy 
 sirup and in this case is produced by the action of acids on 
 starch (311). It is the principal constituent of many table 
 sirups, especially those labeled corn sirup. It is also used 
 in preserving fruits and in candy making, largely because 
 the addition of about 10 per cent of glucose overcomes the 
 tendency of cane sugar to crystallize. 
 
 Glucose is a good food and there is no reason for the popular 
 prejudice against it, except that in the past it was used as an 
 adulterant for the much sweeter cane sugar. 
 
 270 
 
CARBOHYDRATES 271 
 
 The formula for glucose is CeH^Oe- When acted upon by 
 yeast it very readily ferments, forming ethyl alcohol and 
 carbon dioxide (281). Glucose is a reducing agent (43) and 
 the chemical test for it and some other sugars depends on 
 this fact. The test reagent is known as Fehling's solution. 
 It is made by mixing solutions of copper sulphate and sodium 
 hydroxide and then adding Rochelle salt (292) until the 
 precipitate first formed is redissolved. This liquid may 
 now be considered as a solution of cupric oxide (CuO). If a 
 reducing agent such as glucose is added to hot Fehling's 
 solution, it abstracts oxygen from the cupric oxide, leaving 
 cuprous oxide, which is precipitated : 
 
 2 CuO -> Cu 2 O + O. 
 
 307. Fruit sugar, or fructose, is a sugar found in some 
 fruits. It occurs also in the nectar of flowers and, therefore, 
 is a constituent of honey, in which it is associated with glu- 
 cose. It is sweeter than glucose. It ferments under the 
 action of yeast but not so readily as glucose. 
 
 The formula for fructose is CeH^Oe, which will be seen to 
 be the same as that assigned to glucose. It often happens 
 in organic chemistry that two or more entirely distinct com- 
 pounds have the same kind and number of atoms in the 
 molecule. The explanation offered is that the properties of 
 a compound depend not solely upon the number and kind of 
 atoms in the molecule, but upon the way in which these atoms 
 are arranged. A child may with the same number of red, 
 white, and blue blocks work out a variety of patterns by 
 different arrangements of the blocks. Likewise the same 
 number of carbon, hydrogen, and oxygen atoms may be 
 arranged in the molecule in a number of ways, and each 
 different arrangement results in a distinct compound with 
 
272 
 
 ORGANIC CHEMISTRY 
 
 some properties peculiar to itself. Two or more compounds 
 that have the same general formula are known as isomeric 
 compounds, or isomers. 
 
 308. Cane Sugar. As ordinarily used the term sugar refers 
 to cane sugar, or sucrose, which has the formula Ci 2 H 22 Oii. 
 This sugar is found in sugar cane (Fig. 138), sorghum, sugar 
 beet, and the sap of the maple tree, as well as in many fruits. 
 
 FIG. 138. - Growing sugar cane. 
 
 There is more of this sugar in nature than any other sugar. 
 About half the sugar of commerce comes from sugar beets, 
 the rest largely from sugar cane. The juice of the cane, or 
 the water extract of the beet, is first treated with milk of 
 lime (114) to neutralize the acids and to precipitate the 
 albuminous substances that are present. The excess of lime 
 is removed by passing carbon dioxide through the liquid, 
 and the clarified liquid is evaporated in vacuum pans until 
 very thick. Upon cooling, the sugar separates and the re- 
 
CARBOHYDRATES . 273 
 
 maining liquid is removed by whirling in a centrifugal 
 machine. The product is a brown sugar which is refined by 
 dissolving it in water and filtering the solution through bone 
 black (91) to remove the coloring matter, and again concen- 
 trating in vacuum pans. This treatment produces the clear 
 crystals sold under the name of granulated sugar. The liquid 
 left after the separation of the brown sugar is called molasses. 
 The annual production of sugar from cane and sugar beets 
 amounts to over ten million tons. Whether produced from 
 cane or beets the sugar is the same compound. The popular 
 notion that cane sugar differs from beet sugar is erroneous. 
 Cane sugar when pure does not reduce Fehling's solution. 
 If the sugar is boiled with dilute acids (sulphuric, for instance) 
 and the acid is neutralized with an alkali, the resulting solu- 
 tion has a strong reducing action. This is due to the fact that 
 the molecule of cane sugar takes on water and is changed into 
 a molecule each of glucose and fructose : 
 
 Ci 2 H 22 On + H 2 O ->- C 6 Hi 2 6 + C 6 H 12 O 6 . 
 
 cane sugar glucose fructose 
 
 The acid apparently acts as a catalytic agent. This 
 change of cane sugar into glucose and fructose is called in- 
 version, and the product (the mixture of glucose and fructose) 
 is known as invert sugar. In jelly making the acid of the 
 fruit always inverts a part of the sugar. ^Vinegar is some- 
 times added in candy making to invert part of the sugar so 
 that the glucose and fructose will check the tendency of the 
 cane sugar to crystallize. 
 
 Cane sugar does not ferment readily. After a time, how- 
 ever, it does undergo alcoholic fermentation, for the yeast 
 contains a substance which slowly inverts the cane sugar, 
 and the resulting glucose and fructose readily ferment. 
 
 EV. CHEM. 18 
 
274 ORGANIC CHEMISTRY 
 
 309. Malt sugar, or maltose, is a sugar having the same 
 formula as cane sugar (isomer) and is formed by the action 
 of malt on starch (311). Malt, which is made by steeping 
 barley in water until it germinates, and then drying it, con- 
 tains a substance called diastase, which has the power of 
 changing starch into maltose (Ci 2 H 22 On). Maltose is a 
 reducing sugar. It is easily fermented and is the inter- 
 mediate product in the formation of alcohol from starch. 
 When heated with dilute acid it is changed into glucose : 
 
 CiaHaQu + H 2 O ^ 2 C 6 H 12 O 6 . 
 
 maltose glucose 
 
 310. Milk sugar, or lactose, is another isomer of cane 
 sugar that is found only in milk. It is produced com- 
 mercially from the whey left in cheese making. It is much 
 less sweet and less soluble than cane sugar. It is the sugar 
 most commonly used in medicine. It is a reducing sugar but 
 does not readily ferment. Its most important reaction is the 
 change into lactic acid (290) : 
 
 C 12 H 22 O n + H 2 -^ 4 H.C 3 H 5 3 . 
 
 lactose lactic acid 
 
 311. Starch is one of the most abundant compounds pro- 
 duced by plants. It forms from 50 per cent to 75 per cent 
 of the dry matter of seeds and tubers, where it is stored 
 as food for the young plant before it is able to obtain its own 
 food. In this country most of the starch of commerce is 
 prepared from corn, while in Europe potatoes are the prin- 
 cipal source. 
 
 Starch is separated from corn by soaking, grinding, and 
 washing the grain in water and then filtering. In the last 
 process, the finely divided starch passes through bolting 
 cloth and then is allowed to settle from the water in which it 
 
CARBOHYDRATES 
 
 275 
 
 is suspended. Starch occurs in the plant as granules, which 
 vary in form and markings according to the plant from which 
 they are derived (Fig. 139). It is possible to tell the 
 source of the starch by examination under the microscope. 
 
 Starch is not soluble in water. When treated with boiling 
 water the granules swell and burst, forming a gelatinous 
 
 FIG. 139. Magnified starch granules. 1. Potato. 2. Wheat. 3. Rice. 
 
 mass known as starch paste. It is colored blue by iodine. 
 It has the composition represented by the formula C 6 Hi O 5 ; 
 but there are good reasons for believing that the molecule is 
 really much larger than this formula suggests. It is quite 
 customary, therefore, to write the formula (C 6 HioO 5 ) x , in 
 which x represents an unknown number. Starch is changed 
 into glucose by prolonged boiling with dilute acids (306) : 
 
 H 2 - 
 
 Large quantities of starch are used for the production of 
 glucose, which is prepared commercially by boiling corn 
 starch under pressure with hydrochloric acid. The acid is 
 then neutralized with sodium carbonate, and after the liquid 
 has been clarified with bone black it is concentrated to a 
 thick sirup containing 30 to 40 per cent of glucose, mixed 
 with dextrin (312). 
 
 Starch is a valuable constituent of many foods. It is used 
 in the laundry, for the making of library or photo pastes, in 
 
276 ORGANIC CHEMISTRY 
 
 the finishing of cotton cloth, and for many other purposes. 
 Sago is a starch prepared from certain palm trees. Tapioca, 
 a starch, comes from the root of a tropical plant called 
 cassava. 
 
 312. Dextrin. When starch is heated to about 200 C. it 
 is changed into a pale yellow powder that is soluble in water 
 and is not colored by iodine. This substance is called dextrin 
 and is represented by the same general formula as starch 
 (CeHioOs),. Its solution is gummy, and dextrin is now used 
 as a substitute for the natural gums in making mucilage. 
 Dextrin is an intermediate product in the formation of glu- 
 cose from starch; consequently commercial glucose usually 
 contains dextrin as well as glucose. In laundry work the 
 heat of the iron converts some of the starch into dextrin, 
 which gives a glossy finish to the cloth. 
 
 313. Cellulose is the substance that forms the basis of the 
 woody fiber of plants. It is found most abundantly in the 
 stems, roots, and leaves of plants, particularly at maturity. 
 It is the structural basis of the vegetable world and forms the 
 framework of every plant cell. In some plants it is the most 
 abundant material present ; in hay and coarse fodder it 
 makes up 30 to 40 per cent of the dry matter. Cotton and 
 linen are examples of almost pure cellulose. When quite 
 pure, cellulose is a colorless material insoluble in water and 
 differing in texture according to its source. It is assigned the 
 same general formula as starch (C 6 Hi O 5 ) a . In the case of 
 cellulose, however, x probably stands for a larger multiple 
 than it does in the formula for starch. It is evident that 
 cellulose plays an important role in providing material for 
 fuel, shelter, and raiment for mankind. It is used in paper 
 making and in the preparation of guncotton, celluloid, and 
 many other useful materials. 
 
CARBOHYDRATES 277 
 
 314. Nitrogen Compounds of Cellulose. Nitric acid 
 unites with cellulose in several proportions, and the resulting 
 compounds are known collectively as nitrocellulose, or gun- 
 cotton. This substance, which is highly explosive, is the basis 
 of smokeless powder, which has supplanted black gunpowder 
 in military operations. Some of the nitrocellulose compounds 
 dissolve in a mixture of alcohol and ether, forming the sub- 
 stance known as collodion. Collodion is used as liquid court- 
 plaster and in the making of photographic films, because on 
 the evaporation of the ether and alcohol a tough, trans- 
 parent film remains. Celluloid is made by combining gun- 
 cotton with gum camphor. It is, therefore, very inflam- 
 mable, and many serious accidents have occurred from care- 
 lessly allowing celluloid to come into contact with a flame. 
 A mixture of guncotton and nitroglycerin is used under the 
 name of blasting gelatin, especially for heavy blasting, as it is 
 a very powerful explosive. 
 
 315. Gums and Pectin Bodies. Closely related to the 
 sugars are the gums, such as gum arabic and those that 
 exude from peach and cherry trees. Gum arabic is an isomer 
 of cane sugar (C^H^On). It is used in making mucilage and 
 in the better grades of gumdrops. Pectin bodies are found 
 in many fruits and some vegetables. They are jelly like sub- 
 stances that are soluble in hot water and are commonly 
 known as fruit jellies. Gums and the pectin bodies are con- 
 sidered to have the same food value as starch and sugar. 
 
 EXERCISES 
 
 Ex. 179. What is meant by the term carbohydrate ? Are the car- 
 bohydrates of much importance? What is the formula for glucose? 
 Where is it found in nature ? How is commercial glucose manufactured ? 
 For what is it used ? 
 
278 ORGANIC CHEMISTRY 
 
 Ex. 180. Heat a little Fehling's solution to boiling and add a few 
 drops of a solution of pure glucose, or of Karo sirup. Heat again. 
 The red precipitate of cuprous oxide is the test for glucose or other 
 reducing sugar. Explain the action of glucose on Fehling's solution. 
 Soak a few raisins in water and test the solution for grape sugar. 
 
 Ex. 181. What is the formula for fructose ? Compare with that for 
 glucose. How do you explain the fact that there are two compounds 
 with the same formula ? What is an isomer ? What sugars are found 
 in honey ? Test a sample of honey with Fehling's solution. 
 
 Ex. 182. What sugar is found most abundantly in nature? Name 
 some of the plants that contain it. From what plants is it prepared 
 on a commercial scale? How is the brown sugar changed to white 
 sugar ? What is molasses ? Is there any difference between sugar from 
 cane and from beets ? What is the formula for cane sugar ? 
 
 Ex. 183. Test a solution of granulated sugar with Fehling's solu- 
 tion. To a little of the solution add a few drops of hydrochloric acid and 
 boil two minutes. Add a pinch of sodium carbonate to neutralize the 
 acid and test with Fehling's solution. What change has taken place in 
 the sugar ? 
 
 Ex. 184. Test a sample of jelly from home for glucose. Fruit 
 juice and cane sugar were used in making the jelly account for the 
 presence of glucose. Why is vinegar or cream of tartar sometimes used 
 in homemade candies ? 
 
 Ex. 185. What is the formula for maltose ? How is it prepared ? 
 What is the formula for milk sugar? Compare this with the formula 
 for cane sugar. Are they isomers ? What is the sole source of milk 
 sugar ? What product is formed from milk sugar when milk sours ? 
 
 Ex. 186. Reduce two large potatoes to a pulp with a vegetable 
 grater. Tie the pulp in a clean thin cloth and squeeze it into a vessel of 
 water, occasionally dipping the bag into the water. Pour the liquid 
 into a tall cylinder and allow the starch to settle. Pour off the clear 
 water, and transfer the starch to a shallow dish and allow it to dry. 
 
 Ex. 187. What can you say about the importance of starch? 
 From what is the starch of commerce produced? Is starch soluble 
 in water ? What happens to it when boiled with water ? What is the 
 formula ? Why is the formula multiplied by x ? Give some important 
 uses for starch. 
 
CARBOHYDRATES 279 
 
 Ex. 188. Put a little of the starch from Ex. 186 into a test tube and 
 boil it with water. Add a drop of a solution of iodine and potassium 
 iodide. What change takes place ? This is the test for starch. Test 
 for the presence of starch in various seeds and vegetables. 
 
 Ex. 189. Boil a little starch in water and test part of the liquid with 
 Fehling's solution. What is the result ? To another part of the boiled 
 starch add a few drops of hydrochloric acid and boil three or four minutes. 
 Test with Fehling's solution. What difference do you note? What 
 change has taken place in the starch ? How is commercial glucose sirup 
 prepared ? 
 
 Ex. 190. How is dextrin prepared? What is the formula? Is it 
 soluble in water ? Is it colored by iodine ? For what is it used ? Why 
 does the crust of bread have a sweeter taste than the crumb ? 
 
 Ex. 191. (Teacher) If a compound microscope is at hand prepare 
 slides of starch from potatoes, corn, and other food products. Have the 
 class observe and make drawings of the different starch grains. 
 
 Ex. 192. What is cellulose ? In what parts of the plant is it most 
 abundant? Is it an important substance? Give two examples of al- 
 most pure cellulose. What is its formula? What explosive materials 
 are prepared from cellulose ? What is collodion ? Celluloid ? 
 
 Ex. 193. What are the substances known as gums? Give the 
 formula of gum arabic. Compare this with the formula for cane sugar. 
 For what is it used ? What are the pectins and where are they found ? 
 Of what importance is pectin in jelly making ? 
 
CHAPTER XXXIV 
 ORGANIC NITROGEN COMPOUNDS 
 
 316. THE organic compounds so far studied, with the ex- 
 ception of nitroglycerin and nitrocellulose, contain not to 
 exceed three elements; namely, carbon, hydrogen, and 
 oxygen. If a piece of lean meat or a bit of dried egg white is 
 placed in a deep test tube and heated, the odor of ammonia 
 can be detected in the escaping gases. A piece of moistened 
 red litmus paper held in these gases will be changed to blue. 
 This formation of ammonia from the meat or egg will take 
 place more rapidly if the material is first mixed with soda- 
 lime. Evidently, then, these substances contain nitrogen, 
 or the ammonia could not have been formed. During the 
 heating, water vapor is given off, and charcoal remains in 
 the tube ; the meat and ^gg, therefore, must contain carbon, 
 hydrogen, and oxygen as well as nitrogen. If a piece of paper 
 moistened with sugar of lead is held in the escaping gases in 
 the above experiment, it will be blackened, showing the pres- 
 ence of hydrogen sulphide, which indicates that sulphur also 
 is found in the egg and meat. Both meat and egg belong 
 to a large class of compounds known as proteins. 
 
 317. Proteins are generally distributed in the animal and 
 vegetable kingdoms. They are not nearly so abundant as 
 the carbohydrates. It is estimated that ten times as much 
 carbohydrate as protein is produced in the vegetable kingdom. 
 All proteins contain the four elements, carbon, oxygen, hy- 
 drogen, and nitrogen, and most of them contain sulphur as 
 well. Some of the proteins contain in addition to the five 
 
 280 
 
ORGANIC NITROGEN COMPOUNDS 281 
 
 elements mentioned, a small amount of phosphorus. No one 
 has been able to determine the formula for any of the proteins, 
 and they are thought to be the most complex of all the chemi- 
 cal compounds. The complexity of the molecule may be 
 inferred from the fact that the most careful experimenters 
 estimate the molecular weight anywhere from 16,000 to 
 50,000. When this molecular weight is compared with that 
 for sugar (C^H^On), which is 342, some idea may be formed 
 of what an enormous number of atoms the protein molecule 
 must contain. Most of the proteins found in nature are in- 
 soluble in water, although there are a number of soluble pro- 
 teins, the white of egg, for example. Some which will not 
 dissolve in water are soluble in weak salt solutions. The 
 proteins unite with dilute acids and alkalies, forming com- 
 pounds that are sometimes soluble in water and sometimes 
 insoluble. Concentrated acids and alkalies dissolve all the 
 proteins. The proteins decay very readily, and their de- 
 composition is accompanied by offensive odors, as for ex- 
 ample that of rotten eggs. 
 
 318. Tests for Proteins. While there are a great many 
 kinds and classes of proteins, there are a few tests that apply 
 to all proteins, which may be used to show the presence of 
 protein in any substance that is being examined : 
 
 (1) Nitric acid gives a permanent yellow color with pro- 
 teins upon warming. The yellow color produced when nitric 
 acid is dropped on the hands is due to* the reaction of the 
 nitric acid with the protein of the skin. If ammonia water 
 is added to the protein which was turned yellow by nitric 
 acid, it will be changed to an orange color. 
 
 (2) A solution of mercury in nitric acid (mercuric nitrate), 
 known as Millon's reagent, gives a brick red color with pro- 
 teins when heated. 
 
282 
 
 ORGANIC CHEMISTRY 
 
 (3) Tannic acid forms a tough, leathery compound with 
 proteins. If the protein is in solution, tannic acid throws it 
 down in the form of a leathery precipitate. The change of 
 animal hides into leather is largely due to the formation 
 of tough, insoluble compounds by the action of the tannin 
 on the proteins of the skin or hide. 
 
 319. Proteins Insoluble in Water. The muscle, or lean 
 meat, of all animals consists largely of insoluble protein, 
 although there is a small amount of soluble protein present, 
 as will be seen later. Another important source of insoluble 
 proteins is the wheat kernel. If a cupful of wheat flour is 
 made into dough with a small quantity of water and then 
 
 wrapped in a thin cloth 
 and kneaded under 
 water (Fig. 140), the 
 starch of the flour will 
 pass through the cloth, 
 leaving a sticky, elastic 
 mass (Fig. 141), which 
 is the protein material 
 known as the gluten of 
 the wheat. Gluten con- 
 sists of two proteins; 
 
 one > 9^dm, IS a glue- 
 
 like body that binds to- 
 
 gether the particles of flour in the dough ; the other, glu- 
 tenin, is a fine, gray material that does not have the bind- 
 ing property of the gliadin. It is the gliadin in wheat that 
 makes possible a light loaf of bread. All the grains contain 
 proteins similar to the gluten of wheat, although rye is 
 the only other grain in which the gluten is of the quality 
 to make a good dough. 
 
 FIG. 140. The separation of gluten from wheat. 
 
ORGANIC NITROGEN COMPOUNDS 283 
 
 Casein, the important protein of milk, seems to be dis- 
 solved but is really held in mechanical suspension. Its im- 
 portant characteristic 
 is its behavior toward 
 acids and rennet. When 
 either an acid or rennet 
 is added to milk, the 
 casein separates in a 
 thick curd. Rennet ex- 
 tract is made by soak- 
 ing the linings of the 
 
 i P FIG. 141. Showing the elasticity of gluten. 
 
 stomachs of young 
 
 calves in a solution of common salt. The young stomach con- 
 tains a substance called rennin which has the property of co- 
 agulating casein. When milk sours naturally, the lactic acid 
 unites with the casein and forms a curd. The curds formed 
 by acids and that by rennet are both used in cheese making. 
 
 320. Albumins are proteins that are soluble in water. The 
 most familiar example is the white of egg. Albumins coagu- 
 late when heated, as is well shown when an egg is boiled or 
 fried until the white becomes hard. If a solution of egg white 
 is boiled, the albumin coagulates and is precipitated. Al- 
 bumin occurs to a limited extent in meat, as can be shown by 
 rubbing chopped raw meat in a mortar with water, filtering 
 it, and then heating the filtrate. When meat is boiled a scum 
 of albumin is often found on the surface of the water, espe- 
 cially if the meat was placed in cold water in the beginning. 
 Albumin is present in milk and is left in solution in the whey 
 when casein is coagulated either by acid or rennet. Albumin 
 is also one of the constituents of the blood. 
 
 321. Peptones are proteins that are soluble in water and 
 are not coagulated by heat. They are usually formed by the 
 
284 ORGANIC CHEMISTRY 
 
 actions of ferments on the other proteins. When gastric 
 juice, for instance, acts on meat or coagulated albumin, the 
 protein disappears, forming a more or less clear solution. 
 Since this solution gives no precipitate when heated, it does 
 not contain albumin ; but by applying the tests 'described 
 above (318) it can be shown that protein is present. Pep- 
 sin, a substance prepared from the stomach of the pig, can 
 be used to perform this experiment in the laboratory. Some 
 of the so-called predigested or peptonized foods contain pep- 
 tones prepared by the artificial digestion of the food by means 
 of pepsin. The proteins of the food must be converted into 
 peptones in the stomach and intestines before they can be 
 absorbed and pass into the blood. Peptones are not present 
 in ordinary foods in appreciable amounts but are formed from 
 the foods during digestion. 
 
 322. Importance of Proteins. Proteins are present in all 
 plant and animal cells. The vital part of the cell, the proto- 
 plasm, consists of protein material, and consequently it will 
 be seen that all life depends on the proteins. The muscles of 
 animals consist largely of proteins ; and the only way in 
 which the muscles can be built up and repaired is by means 
 of the proteins of the food, since the animal body is not able to 
 manufacture proteins from other materials. The proteins, 
 then, have a place that cannot be filled by the carbohydrates, 
 fats, or any other compounds. All parts of the plant con- 
 tain some protein ; but the seeds contain the most, since it 
 is stored there for the use of the plantlet when it begins 
 its growth. It will be seen later that the plant can 
 manufacture these complex proteins from very simple 
 substances. 
 
 323. Gelatin and Other Albuminoids. There is another 
 class of nitrogen compounds, somewhat resembling the pro- 
 
ORGANIC NITROGEN COMPOUNDS 285 
 
 teins, to which the name albuminoids has been given. The 
 best-known example of this class is gelatin, which is obtained 
 from the connective tissue and bones of animals. Commer- 
 cial glue is an impure gelatin. Gelatin dissolves in hot water 
 and forms a jellylike mass upon cooling. While it is a good 
 food product and is easily digested, it will not take the place 
 of protein in the food. Keratin is a hard, horny albuminoid 
 found in the horns, hoofs, hair, nails, and feathers. Mucin, 
 the chief constituent of mucus, gives the sliminess to the 
 secretion of the mucous membrane. It is present in the 
 saliva. 
 
 324. Amines. There is a marked difference between the 
 simple nitrogen compounds that the plants take in from the 
 soil (nitrates and ammonia) and the very complex proteins 
 that they store in their seeds. It is not surprising, therefore, 
 to find that there are intermediate compounds, or, in other 
 words, that the building up of a protein is not a matter of 
 one change but takes place by steps. Some of the inter- 
 mediate compounds are known and have been assigned the 
 name of amines. Their chief interest for the purpose of this 
 text lies in the fact that they are intermediate compounds in 
 the building up of proteins, and that when the protein is 
 broken down during digestion or decay, the amines are pro- 
 duced before the nitrogen is finally changed back to ammonia 
 or nitric acid (168). 
 
 325. Protein Production and Destruction. The plant 
 produces protein by a series of changes about as follows : 
 
 (1) Ammonia or nitrate is taken from the soil. 
 
 (2) An amine is formed from ammonia. 
 
 (3) A protein is finally formed from the amine. 
 
 When animals consume the plant as food the reverse 
 order of changes takes place : 
 
286 ORGANIC CHEMISTRY 
 
 (1) The protein is digested and made over into animal 
 protein. 
 
 (2) The animal protein is finally broken down into amines. 
 
 (3) The amine is expelled from the body as waste matter. 
 
 (4) In the soil the amine is changed into ammonia and 
 nitric acid by the bacteria and is ready to begin again this 
 cycle of changes. 
 
 326. Alkaloids are nitrogenous organic compounds found 
 in many animals and plants, but not to any appreciable 
 amount in true food plants. They somewhat resemble am- 
 monia in their chemical behavior and are, therefore, called 
 alkaloids (like alkalies). They form the so-called active 
 principle of many of the plants used in medicine. The 
 following are some of the principal alkaloids : 
 
 Caffeine (C 8 HioN 4 C^), from coffee and tea. 
 Quinine (201124X202), from Peruvian bark. 
 Strychnine (CaiHa^Qg), from nux vomica bean. 
 Morphine (Ci 7 Hi 9 XO 3 ), from the poppy. 
 Nicotine (Ci Hi 4 N 2 ), from tobacco. 
 
 Alkaloids are also formed at times in the animal body. Some 
 of the alkaloids formed during the decomposition of proteins 
 are extremely poisonous and are known as ptomaines. They 
 sometimes occur in stale meat, fish, and cheese. 
 
 EXERCISES 
 
 Ex. 194. Place a piece of lean meat in a test tube fitted with a 
 cork in which is a small glass tube. Heat over the flame. Note the 
 odor of the escaping gas. Hold a piece of moist red litmus paper in the 
 gas. Test with sugar of lead paper. Repeat the experiment with some 
 peas or beans. Mix a quarter of a test tube full of dry clover with an 
 equal bulk of soda-lime and heat and test as above. Have you any evi- 
 
ORGANIC NITROGEN COMPOUNDS 287 
 
 dence that ammonia was formed? Was sulphur present in the gas? 
 What was the source of these substances ? 
 
 Ex. 196. What can you say about the distribution of proteins in 
 nature ? Are they as abundant as the carbohydrates ? What chemical 
 elements are found in the proteins ? Is the protein molecule very com- 
 plex ? What effect do acids and alkalies have on proteins ? 
 
 Ex. 196. To a little egg white add a few drops of Millon's reagent 
 and warm the mixture. What is the result ? Try the same experi- 
 ment with crushed wheat or corn, milk, or other foodstuffs. Which 
 gave the test for proteins ? 
 
 Ex. 197. (Teacher) Mix a cupful of flour to a dough with water. 
 Place it in a cloth bag and knead it under water (Fig. 140) until all the 
 starch has been washed out. Examine the material left in the cloth. 
 Is it sticky and elastic ? What is this substance ? Make the test with 
 Millon's reagent on a small piece of it. What other substances can you 
 name that belong to the group of insoluble proteins ? 
 
 Ex. 198. Dissolve the white of a raw egg in about a pint of water 
 and use it for the following tests : (1) Heat a part of the solution to 
 boiling in a test tube. What happens? (2) To another portion of 
 the egg-white solution add tannic acid. What is the result ? ^ 
 
 Ex. 199. Place 10 grams of ground oats in a bottle with 50 cc. 
 of water. Cork and shake the bottle vigorously and let it stand for 
 half an hour or until the next period. Filter and test the filtrate with 
 tannic acid. Is there any albumin in the oats ? Mention some other 
 materials which contain albumin. 
 
 Ex. 200. (Teacher) Dissolve five grams of commercial scale 
 pepsin in a quart of water containing 5 drops of hydrochloric acid. 
 Pass the white of a hard-boiled egg through a sieve and place it in a flask 
 with 250 cc. of the above pepsin solution. Place the flask in a water 
 bath and keep at blood temperature for four or five hours. What action 
 did the pepsin have on the congested egg albumin ? Filter some of the 
 solution for use in the next exercise. 
 
 Ex. 201. Heat a portion of the solution from the last exercise to 
 ascertain whether it contains albumin. To another portion add tannic 
 acid. To another add Millon's reagent and heat it. Does the solu- 
 tion contain albumin ? Does it contain some kind of protein ? What 
 are these soluble proteins called ? Are peptones present in large quan- 
 tities in foods ? Are they produced during digestion ? 
 
288 ORGANIC CHEMISTRY 
 
 Ex. 202. Why are proteins vital to plant and animal life ? Where 
 does the animal get the material to build its muscle ? Can the animal 
 manufacture proteins ? In what part of the plant is the most protein 
 found ? Why is the protein stored in the seed ? Can the plants manu- 
 facture protein ? 
 
 Ex. 203. (Teacher) Obtain a package of any of the culinary 
 gelatins and prepare a jelly with the amount of water recommended in 
 the printed directions. To what class of compounds does gelatin 
 belong ? What is the source of gelatin ? What is the difference between 
 gelatin and glue? Name an albuminoid found in bones and hair; 
 one found in mucus. 
 
 Ex. 204. Does the plant form intermediate compounds between the 
 nitrates and the proteins ? What are some of the compounds called ? 
 Outline the cycle of changes in the production and destruction of pro- 
 teins. What are the alkaloids ? Name some of the common alkaloids^ 
 What is meant by a ptomaine ? 
 
CHAPTER XXXV 
 COMPOSITION OF PLANTS 
 
 327. Water. All plants and, indeed, all food materials 
 contain water which in many cases makes up the larger 
 portion of their weight. Green plants, such as the mature 
 corn plant, contain as much as 80 per cent of water, while 
 some of the more succulent plants like cabbages, lettuce, 
 and spinach may contain as high as 90 per cent of water. 
 In general it may be said that the younger the plant the 
 larger the percentage of water it contains, and that as the 
 plant matures the percentage of water is decreased. The 
 stems or woody parts of plants contain less water than 
 the leaves. The juicy fruits, such as oranges, and straw- 
 berries, often contain over 90 per cent of water, while the 
 grains may be as low as 10-15 per cent in moisture con- 
 tent. Many of the plants and plant products are partially 
 dried to remove the water before being used as foods for 
 man or domestic animals, but even well-cured hay, or such 
 a dry substance as wheat flour, still contains about 10 per 
 cent of water. 
 
 The amount of moisture in a substance is determined in 
 the laboratory by heating the material for several hours at 
 the temperature of boiling water. By this means the water 
 in the plant or other substance is converted into steam and 
 thus expelled. The material is usually dried in a water oven 
 EV. CHEM. 19 289 
 
290 
 
 ORGANIC CHEMISTRY 
 
 similar to the one shown in Fig. 142. The walls of this oven 
 are double, the space between them being partially filled with 
 water which is kept boiling by means of a gas burner placed 
 
 beneath the oven. In such an oven 
 the substance being dried may be 
 kept heated without danger of the 
 temperature rising above 100 C. 
 and scorching the material. Ovens 
 heated by electricity are also used, 
 the heat being adjusted by a reg- 
 ulator which prevents too great a 
 rise in temperature. 
 
 328. Dry Matter. The dry mat- 
 ter of a material is the portion left 
 after all the water has been re- 
 moved. The dry matter in plant 
 products varies within wide limits, 
 being as low as 5-6 per cent in some fruits and over 90 per 
 cent in certain cereal products. The amount and composi- 
 tion of the dry matter in a food material determines its value 
 as a nutrient. 
 
 329. Plant Ash. The ash of a plant or of any substance is 
 that portion that remains after the substance is burned at 
 the lowest temperature necessary for complete combustion. 
 It corresponds in a general way to the ashes left in the stove 
 when wood is burned. The ash of the plant is sometimes 
 spoken of as the mineral matter, or as the inorganic matter of 
 the plant, and also as the non- volatile part. It includes all 
 of the material which the plant obtained from the soil with 
 the exception of the water and nitrogen, and possibly part of 
 the sulphur and phosphorus, which disappear when the 
 plant is burned. 
 
 FIG. 142. Water oven for the 
 determination of moisture in plant 
 and animal products. 
 
COMPOSITION OF PLANTS 291 
 
 The percentage of ash is determined in the laboratory by 
 igniting a small quantity of the material (two grams) in a 
 platinum or porcelain dish (Fig. 17) until all the carbon is 
 burned and a white or nearly white ash remains. During 
 the experiment the material must be carefully protected 
 from currents of air, which might blow away the light 
 particles of the ash. The weight of the ash obtained in 
 this way divided by the weight of the material taken for 
 the experiment gives the percentage of ash in the substance. 
 
 330. Composition and Amount of Ash in Plants. The ash 
 of all plants contains measurable quantities of nine chemical 
 elements potassium, calcium, sodium, iron, magnesium, 
 phosphorus, sulphur, chlorine, and silicon. Traces of alu- 
 minum and manganese also are found in the ash. None of 
 the elements of the ash existed in the plant in the elemen- 
 tary or free state ; but they are always in chemical combina- 
 tion forming salts, or are combined with the elements that 
 form the organic part of the plant. It has been shown, for 
 example, that potassium occurs in grapes as acid potassium 
 tartrate (292) and that phosphorus and sulphur are con- 
 tained in certain of the proteins (317). 
 
 Some plants contain much more ash than others, and there 
 is great variation in the percentage composition of the ash 
 of different plants. The ash of clover hay contains nearly 
 four times as much calcium as the ash of^ timothy hay, but 
 only one fifth as much silicon. The ash is not evenly dis- 
 tributed throughout all parts of the plant. In corn the 
 amount of ash in the different parts of the plant is as follows : 
 
 Roots 5.8 per cent 
 
 Leaves . 8.1 per cent 
 
 Stems 6.6 per cent 
 
 Grain 1.4 per cent 
 
292 ORGANIC CHEMISTRY 
 
 331. Organic Matter. That part of the plant which com- 
 pletely burns and passes off in the form of gaseous products 
 is termed organic matter. It is determined in the laboratory 
 by subtracting the percentage of ash from the dry matter. 
 The organic matter includes the proteins, carbohydrates, 
 fats, organic acids, and other so-called organic compounds of 
 the plant. It is customary to divide the organic constituents 
 of the plant into two large classes ; namely, (1) nitrogenous, 
 and (2) non-nitrogenous, the division depending upon the 
 presence or absence of the element nitrogen in the compounds. 
 
 332. Nitrogenous Compounds. The proteins are the most 
 important of the nitrogenous constituents of plants. Most 
 of the proteins found in plants belong to the insoluble class, 
 although the albumins are found to a limited extent. There 
 are doubtless a great number of different plant proteins, 
 but only a few of them have been isolated in the pure state 
 and carefully studied. The proteins are found in all parts 
 of the plant, but are much more abundant in the seeds. 
 The leaves contain more protein than do the stems or roots. 
 
 All parts of a plant are composed of minute cells, lying 
 close together. These cells are so small that the compound 
 microscope must be used in order to see them. The cells 
 contain a clear, granular substance, called protoplasm, which 
 has about the consistency of the white of egg. It is the 
 living substance of the cell, and the growth and functions of 
 the plant depend upon the activity of the protoplasm. It 
 is not known exactly what protoplasm is, but it is un- 
 doubtedly largely composed of proteins. 
 
 To find the amount of protein in a food material the 
 chemist first determines the percentage of nitrogen and then 
 multiplies this by 6.25 to obtain the equivalent of protein. 
 This is because proteins contain, on the average, about 16 
 
COMPOSITION OF PLANTS 
 
 293 
 
 per cent nitrogen, or there is about one part of nitrogen to 
 every 6.25 parts of protein (100 * 16 = 6.25). The method 
 of determining the nitrogen consists in first heating a weighed 
 quantity of the food with sulphuric acid, 
 which converts all the nitrogen into arnmo- 
 nium sulphate. The ammonia from the 
 ammonium sulphate is then liberated by 
 means of sodium hydroxide (167) and its 
 amount determined. The chemist calls the 
 material determined by multiplying the ni- 
 trogen by 6.25 crude protein; because it is 
 not quite true that all the nitrogen in the 
 food is in the form of protein. 
 
 333. The non-nitrogenous compounds 
 of plants are (a) fats ; (6) cellulose, or fiber ; 
 (c) carbohydrates. 
 
 (a) Fats, or oils, are present to some ex- 
 tent in all parts of the plant, but by far the 
 larger portion is found in the seeds. The 
 plant fats are for the most part oils, and the 
 amount present varies greatly in different 
 plants and in different parts of the same 
 plant. Wheat contains about 2 per cent of 
 fat; corn, 5 per cent; and flaxseed, 35 per 
 cent or more of oil. The roots and stems 
 of corn contain only about one half of one 
 per cent of oil or fat. To determine the 
 amount of fat, a weighed sample of food 
 material is repeatedly washed with ether un- 
 til all the fat is extracted ; the ether is then evaporated and 
 the fat weighed. In practice a special apparatus (Fig. 143) 
 is used in which the same quantity of ether is made to pass 
 
 FIG. 143. Appa- 
 ratus used in deter- 
 mining amount of fat 
 or ether extract. 
 
294 ORGANIC CHEMISTRY 
 
 repeatedly through the food material until all the fat is 
 removed. The substance extracted from the food in this 
 way is not pure fat, or oil, as the ether will also dissolve 
 chlorophyll, waxes, and resins if they are present. In the 
 case of the materials ordinarily used as food for man and 
 animals the amounts of these substances present are so small 
 as to cause no serious error in the determination; but to 
 avoid inaccuracy of statement the substance determined as 
 above is quite commonly called ether extract or crude fat. 
 
 (b) Cellulose. Cellulose, which forms the walls of the 
 plant cells, and the closely related woody substances found 
 in plants are commonly called fiber, or crude fiber. The de- 
 termination of the amount of crude fiber in a food consists 
 of three steps : (1) the fat is extracted from the substance 
 with ether ; (2) the material is then boiled with very dilute 
 sulphuric acid to convert the starch into sugar, which is then 
 washed away ; (3) it is then boiled with dilute sodium hy- 
 droxide to dissolve the proteins (317), and the remaining 
 material is washed, dried, and weighed as crude fiber. The 
 roots and stems of plants contain the largest amounts of 
 fiber, as may be surmised from their woody nature. The 
 seeds usually contain very little fiber, only 2 to 5 per cent. 
 
 (c) Carbohydrates. While cellulose is strictly speaking a 
 carbohydrate, this term in food analysis is commonly used to 
 designate the starches and sugars, the cellulose being stated 
 separately as fiber. Starch is the most abundant of the 
 carbohydrates and is found principally in the seeds, roots, 
 and tubers of plants, being stored in those parts which are 
 concerned with new growth. Although the sugars are not so 
 abundant in nature as starch, they are quite widely distrib- 
 uted and are found in large amounts in some fruits and 
 vegetables and in the saps of sugar cane and the maple tree. 
 
COMPOSITION OF PLANTS 295 
 
 The separation and determination of the individual carbo- 
 hydrates is a tedious process, and consequently, since they all 
 have about the same food value, they are usually lumped 
 together in the statement of analysis. In reality the carbo- 
 hydrates are not determined at all, but the percentages of 
 water, ash, crude protein, ether extract, and crude fiber are 
 added together; their sum is then subtracted from 100, 
 and the remainder is the percentage of carbohydrates. 
 Wheat, for example, contains : 
 
 Water 9.25 per cent 
 
 Ash 2.95 per cent 
 
 Crude protein .13.25 per cent 
 
 Ether extract 2.20 per cent 
 
 Crude fiber 2.25 per cent 
 
 Total ! '. ! '. '. ! ! ! . 29.90 per cent 
 100 - 29.90 = 70.10 = per cent of carbohydrates. 
 
 In the statement of analysis of a feeding stuff for domestic 
 animals the expression nitrogen-free extract is used instead of 
 carbohydrates. In the analysis of human foods the latter 
 term is commonly used. In foods or feeding stuffs of vege- 
 table origin the amount of nitrogen-free extract, or carbo- 
 hydrates, usually exceeds that of any other of the groups 
 of compounds. 
 
 334. Analysis of the Corn Plant. If a number of samples 
 of the corn plant are taken for analysis as a feeding stuff at 
 the time the corn is just mature, the ayerage composition is 
 found to be about as follows : 
 
 Water 79.3 per cent 
 
 Ash ".... 1.2 per cent 
 
 Crude protein ........ 1 .8 per cent 
 
 Ether extract 0.5 per cent 
 
 Crude fiber 5.0 per cent 
 
 Nitrogen-free extract 12.2 per cent 
 
 Total 100.0 per cent 
 
293 
 
 ORGANIC CHEMISTRY 
 
 The following table states the composition more in detail. 
 The numbers show the percentage of the various constituents. 
 
 Water / Hydrogen 8.81 
 79.3 1 Oxygen 70.49 
 
 Cora 
 
 Plant 
 
 100 
 
 Dry 
 
 
 ' Crude protein 1.8 
 
 Nitrogen 0.29 
 
 Organic matter 
 19.5 ' 
 
 Ether extract 0.5 
 Crude fiber . 5.0 
 
 Carbon 9.05 
 Oxygen 8.89 
 
 
 Nitrogen-free 
 
 Hydrogen 1.27 
 
 
 . extract . . 12.2 
 
 
 
 Chlorine . . 0.04 
 
 
 
 Potassium . 0.33 
 
 
 
 Phosphorus . 0.05 
 
 
 
 Calcium . . 0.12 
 
 
 
 Magnesium . 0.09 
 
 
 Ash . . 1.2 
 
 Iron . . . 0.02 
 
 
 
 Sulphur . . 0.01 
 
 
 
 Sodium . . 0.03 
 
 
 
 Silicon . . . 0.11 
 
 
 
 Oxygen . . 0.40 
 
 
 It is worth noting that this table shows that over 
 per cent of the green plant is composed of three elements, 
 carbon, hydrogen, and oxygen, while all other elements 
 combined make up only about 1-J per cent of its weight. 
 
 EXERCISES 
 
 Ex. 205. Recall an experiment that shows the presence of water 
 in plants. About how much water do growing plants contain ? Which 
 contain the larger percentage of water, old or young plants ? Is there 
 any water in cured hay and grains ? How is the amount of water in a 
 plant determined in the laboratory ? (Note to the teacher. If a good 
 balance and water oven are available the student should make a deter- 
 mination of the amount of water in a green plant.) 
 
 Ex. 206. Burn some plant material in a porcelain dish. Stir the 
 material until the ash is nearly white. What is included in the ash 
 
COMPOSITION OF PLANTS 297 
 
 of the plant ? How is the exact amount of ash in the plant determined ? 
 What is meant by the dry matter of the plant ? Do the chemical ele- 
 ments exist in the plant in the same compounds in which they are 
 found in the ash ? Are the ash elements evenly distributed in all parts 
 of the plant ? Which part contains the least ash ? The most ash ? 
 
 Ex. 207. What is meant by the organic matter of the plant ? How 
 does it differ from dry matter? Recall an experiment to show the 
 presence of proteins in plants. Which class of proteins is present in 
 plants in largest quantity ? In what part of the plant are the proteins 
 most abundant ? What is protoplasm ? Why are proteins so impor- 
 tant to the plant ? How is crude protein determined in the laboratory ? 
 Why is the nitrogen multiplied by 6.25 ? 
 
 Ex. 208. Place a tablespoonful of corn meal or ground flaxseed in a 
 small bottle and add an ounce of ether. Cork the bottle and shake it 
 at intervals for an hour. Filter the contents through a dry filter into 
 a glass dish and place it in the open window until the ether evapo- 
 rates. (Caution. Do not handle the ether near a flame.) Did the 
 ether extract any fat from the meal ? How is fat in foods determined 
 in the laboratory ? Which part of the plant usually contains the most 
 fat? 
 
 Ex. 209. Place about one gram of ground straw or hay in a beaker 
 and add 200 cc. of water and 20 drops of sulphuric acid. Boil on a 
 sand bath 20 minutes. Allow the material to settle and pour off the 
 liquid. Add 100 cc. of water and when the material again settles pour 
 off as before. Now add 200 cc. of water and 4 cc. of the sodium 
 hydroxide solution of the laboratory (10 %), boil 20 minutes, and wash 
 as before. The material left in the beaker is crude fiber. 
 
 Ex. 210. What is the crude fiber of the plant ? How is the per- 
 centage of crude fiber determined? What parts of the plant contain 
 the most fiber? Are the other carbohydrates of the plant determined 
 directly? How are they calculated? What does "nitrogen-free ex- 
 tract " mean? Discuss the composition of the corn plant. 
 
CHAPTER XXXVI 
 CHEMISTRY OF PLANT GROWTH 
 
 335. Seeds. Most of the crops grown by farmers and 
 gardeners are raised from seeds. A careful examination of 
 a seed shows that it consists of an embryo plant (Fig. 144 pi) 
 surrounded by reserve food materials in the form of mineral 
 matter and nitrogenous and non-nitrogenous organic com- 
 pounds. An analysis would show that 
 while the total amount of ash in the 
 seed is small it is especially high in 
 phosphorus, potassium, and magnesium 
 
 ash elements that are of great im- 
 portance in the nutrition of the young 
 plant. The non-nitrogenous part con- 
 sists in most seeds largely of starch, with some oil and cel- 
 lulose, and a little sugar and gums. In such seeds as flax, 
 rape, mustard, and cotton seed, oil is the principal non- 
 nitrogenous substance. Oil seeds are, as a rule, small in size 
 but concentrated in food materials. The nitrogenous com- 
 pounds of the seed are mainly in the form of insoluble pro- 
 teins, such as the glutens of the cereals. Some other pro- 
 teins, as albumins, are present in small quantities as well 
 as traces of amino-compounds. 
 
 336. Germination of Seeds. When a seed is planted in 
 warm, moist soil it first absorbs moisture and swells, then 
 bursts the seed coat, and begins to sprout (Fig. 145). It 
 
 298 
 
CHEMISTRY OF PLANT GROWTH 
 
 299 
 
 pushes a shoot upward and a root downward, but until the 
 leaf expands and the root has fairly entered the soil, the 
 young plant derives no nourishment other than water, 
 either from the earth or from the air. It lives on the starch, 
 gluten, mineral matter, and other compounds contained 
 in the seed. The seed, therefore, acts as 
 a storehouse of concentrated food to 
 nourish the plant until it is able to draw 
 its nutrition from external sources. But 
 the substances found in the seed are for 
 the most part insoluble; hence they 
 must undergo a chemical change before 
 they can be taken up into the sap and 
 conveyed along the vessels of the young 
 shoot they are destined to feed. It 
 is so arranged in nature that when the 
 seed first sprouts, there is produced at the 
 base of the germ a small quantity of a 
 white soluble substance called diastase. 
 This substance acts upon the starch, making it soluble in the 
 sap, which is thus enabled to take it up and convey it just 
 as it is wanted, to the shoot or to the root. The starch is 
 thus converted into dextrine and maltose (309). In the oily 
 seeds the mucilage and oil take the place of starch in nourish- 
 ing the young sprout. The oil is first decomposed into glyc- 
 erin and fatty acids (303), and these substances are finally 
 converted into carbohydrates. 
 
 As the sap ascends, the dextrin from the starch is further 
 changed into sugar. This sugar is later changed into cellu- 
 lose, or woody fiber of the stem and leaf. By the time that 
 the food contained in the seed is exhausted, the plant is able 
 to live by its own exertions, at the expense of air and soil. 
 
 FIG. 145. Seedlings 
 of corn. 
 
300 APPLIED CHEMISTRY 
 
 In like manner the insoluble protein compounds in the 
 seed are converted into soluble forms similar to the peptones. 
 Some of the soluble proteins are even broken down into 
 amines, which are then in a condition to be transported 
 through the plant tissue and used as building material. 
 These compounds, when they reach the place where they 
 are used, are reconstructed into proteins. 
 
 337. Conditions Necessary for Germination. These re- 
 quirements are the presence of : (1) moisture, (2) oxygen, 
 and (3) heat. If seeds are kept dry, they will not sprout. 
 They will, however, retain their vitality for a long time, and 
 advantage is taken of this fact in the storage of seeds 
 for future use. In the case of agricultural plants, germina- 
 tion is best effected when the soil is moist but not wet. 
 
 Likewise seeds which are kept under the proper conditions 
 of moisture and temperature will not germinate if they are 
 not supplied with oxygen. Seeds often fail to grow because 
 they are planted at too great a depth to obtain the needed 
 oxygen from the air. The necessity of oxygen for germina- 
 tion may be shown by a simple experiment. When seeds are 
 put into water those which float are usually the only ones that 
 germinate. Those which sink cannot germinate for lack of 
 oxygen. If a current of air is kept passing through the water 
 all the seeds will germinate. Seeds kept under the proper 
 conditions of moisture and temperature in bottles in which 
 the air is replaced by any inert gas, such as hydrogen or car- 
 bon dioxide, will not germinate. 
 
 Finally if seeds are supplied with sufficient moisture and air 
 but kept cold, germination will not occur. Seeds sown dur- 
 ing cold weather often remain some weeks before sprouting, 
 while those sown in warm weather may germinate in a few 
 days. Seeds of different plants vary in the amount of heat 
 
CHEMISTRY OF PLANT GROWTH 
 
 301 
 
 they need for germination. Wheat, oats, and peas will 
 sprout while the ground is quite cool and can be sown early 
 in the spring. Corn requires more heat than oats ; while soy 
 beans, cucumbers,' melons, and cotton need still more 
 warmth in the soil. Hence the farmer and gardener arrange 
 the time of planting, waiting until the soil has the proper 
 temperature before planting the various kinds of seeds. 
 
 338. Carbon Dioxide Exhaled during Germination. The 
 sprouting of the seed starts the hitherto dormant cells into 
 active life and growth, and one result of 
 
 all life, whether animal or vegetable, is 
 the production of carbon dioxide through 
 respiration (Fig. 146) . This accounts for 
 the need of oxygen during germination. 
 The production of carbon dioxide is due 
 to the oxidation of some of the carbon 
 compounds of the seeds. 
 
 339. Roots, Bulbs, and Tubers. Some 
 
 i i . i i xi r showing that germinating 
 
 plants do not bear seeds the first year see ds produce carbon 
 but go into a resting stage during the ' 
 winter and produce seeds the following year. Such plants 
 are called biennial. They store the material needed to start 
 growth the second year in enlarged fleshy roots, like the 
 beet ; in underground stems or tubers, like the potato ; or 
 in enlarged stalks called bulbs, like the onion. The food 
 materials in these storage organs are similar to those found 
 in the seeds ; but they are not in such a dry and concentrated 
 form. The chemical changes which these compounds un- 
 dergo when growth begins in the spring are similar to those 
 which occur during the germination of the seeds. 
 
 340. Manufacture of Carbohydrates. If the plantlet 
 produced by the seed is kept in the dark, it remains color- 
 
 FIG. 146. Apparatus 
 
 inating 
 
 carbon 
 
302 APPLIED CHEMISTRY 
 
 less and grows until the food which was stored in the seed is 
 exhausted. Under normal conditions, however, the leaves 
 of the plantlet become green before the food stored in the 
 seed is completely exhausted, and the green plant has the 
 power of preparing its own food from the simple compounds 
 absorbed from the soil and the atmosphere. 
 
 The green coloring material found in the leaves is called 
 chlorophyll, and a microscopic examination of the leaf shows 
 that it is contained in small grains called chlorophyll bodies or 
 chloroplasts , which are imbedded in the protoplasm of the leaf 
 cell. The chemistry of chlorophyll is little understood, but 
 it is of utmost importance to the plant because its pres- 
 ence enables the protoplasm of the leaf to produce all the 
 
 Stomata 
 
 A 
 
 FIG. 147. Leaf structure. A, upper surface. B, under surface. C, cross 
 
 section. 
 
 organic compounds of the plant. Of special interest is the 
 manner in which the plant manufactures its carbohydrates. 
 The carbon dioxide of the air enters the leaves through the 
 tiny openings or stomata, which are found on the under side, 
 and passes into the air spaces between the cells, and finally 
 into the cells themselves. 
 
 In the cell the carbon dioxide unites with the water 
 which the plant has absorbed from the soil and forms car- 
 bonic acid. Under the action of chlorophyll and daylight 
 
CHEMISTRY OF PLANT GROWTH 303 
 
 the carbonic acid probably breaks up into formaldehyde and 
 oxygen : 
 
 H 2 CO 3 ->- CH 2 O + 2O. 
 
 The oxygen is given off through the cell walls into the air 
 spaces and passes out through the stomata into the atmos- 
 phere. The formaldehyde is then probably almost in- 
 stantly changed to glucose, thus : 
 
 6 CH 2 O ->- C 6 Hi 2 O 6 . 
 
 The glucose manufactured in this way is then transported 
 to that part of the plant needing new material for growth, 
 where it is changed into cellulose, starch, oil, or other of the 
 numerous plant compounds. But during the daytime the 
 glucose is produced more rapidly than it can be transported, 
 and the cells would be clogged with soluble food if it were 
 not changed to an insoluble form for temporary storage. 
 The plant, therefore, has the power of changing the glucose 
 into starch, thus : 
 
 C 6 H 12 O 6 -> C 6 HioO 5 + H 2 O. 
 
 At night, when no carbonaceous matter is being formed, 
 the starch is changed back to glucose or other soluble com- 
 pounds and is transported to other parts of the plant. By 
 morning all the starch has disappeared from the leaves. In 
 testing for starch, the leaf is first boiled to kill the protoplasm 
 and then treated with alcohol to extract the chlorophyll. 
 After this it is placed in a dilute solution of iodine, which gives 
 a violet coloration to any starch which may be present. 
 
 341. Daylight Necessary for Carbon Fixation. It has 
 already been stated (105) that daylight is necessary to enable 
 the plant to utilize the carbon of the carbon dioxide. The 
 light waves absorbed by the chlorophyll supply the proto- 
 
304 
 
 APPLIED CHEMISTRY 
 
 FIG. 148. Exclusion of light from 
 part of a leaf. 
 
 plasm with the energy necessary to enable it to split off the 
 oxygen from the carbonic acid (340) . This process of build- 
 ing carbohydrates from water and carbon dioxide is called 
 
 photosynthesis; it is a chemical 
 synthesis (32) by means of light. 
 That light is necessary for the 
 formation of starch can be shown 
 by covering part of a leaf with 
 some opaque substance early in 
 the morning (Fig. 148), and in 
 the afternoon picking the leaf and 
 testing for starch. It will be 
 found that no starch is present in 
 the part that was kept dark, but that starch is abundant in 
 the rest of the leaf. The common garden nasturtium is an 
 excellent plant for this experiment, but any other rapidly 
 growing plant will do. If a few leaves are tested early in the 
 i morning they will generally be found 
 to contain no starch, while those 
 tested toward evening will show 
 starch in abundance. Plants kept 
 in the dark will give no test for 
 starch in their leaves, and if allowed 
 to remain in the dark too long they 
 even lose their green color. 
 
 The light of the electric arc and, 
 indeed, any white light, can furnish 
 energy for carbon fixation, and it 
 has been suggested that plants 
 might be made to grow more rapidly if supplied with light 
 at night. This has been tried in the greenhouse ; but it has 
 been found that while the pl'ants in the houses lighted at 
 
 FIG. 149. The same leaf tested 
 with iodine, showing absence of 
 starch in part excluded from light. 
 
CHEMISTRY OF PLANT GROWTH 305 
 
 night do grow more rapidly, the extra growth does not repay 
 the extra expense of lighting. 
 
 At the time of the most color in plants, there is the greatest 
 cell activity and the largest amount of plant tissue is being 
 produced. When a plant ripens, the decline of activity 
 of the cells may be observed by the change in the color of the 
 plant. In corn the lower joints of the stalk turn yellow 
 first, indicating that growth and activity have ceased in 
 those parts. Then the upper leaves become yellow, and 
 finally the husk becomes yellow and inactive. Chloro- 
 phyll is one of the principal agents taking an active part in 
 plant growth, and whenever it is destroyed, plant growth is 
 checked. 
 
 As the atmosphere contains only 3 parts in 10,000 of 
 carbon dioxide, it may be thought that a larger amount of 
 this gas would enable the plant to make a greater growth. It 
 has been possible, indeed, with plants in small inclosures, 
 to increase the growth by adding carbon dioxide to the air. 
 There is every reason to believe, however, that plants grown 
 in the open never suffer for lack of it and that the size of the 
 crop is always limited by some other factor, and never 
 because of an insufficient supply of carbon dioxide (105-107). 
 
 342. Respiration. Every living cell must breathe during 
 the entire period of its active life. Growing plants, therefore, 
 breathe or respire during all of the twenty-four hours. 
 Through respiration the plant takes in oxygen and gives off 
 carbon dioxide. The statement so often seen that "during the 
 night plants take in oxygen and breathe out carbon dioxide, 
 and in the daytime take in carbon dioxide and breathe out 
 oxygen," is not strictly true. The process of photosynthesis 
 should not be confused with respiration. The latter occurs 
 day and night, while the former, which is strictly a manu- 
 EV. CHEM. 20 
 
306 APPLIED CHEMISTRY 
 
 facturing process and has nothing to do with breathing, takes 
 place only during daylight. It is true that the amount of 
 oxygen given off during photosynthesis is so much greater 
 than that absorbed by respiration that the latter process is 
 obscured during the daytime by the former. The oxygen 
 evolved during six hours of active carbon fixation is as much 
 as would be absorbed by the process of respiration in twenty- 
 four hours. It is evidently true, then, that plants decrease 
 the amount of carbon dioxide in the air during daylight, but 
 that, like animals, they add to it during the night. 
 
 343. Changes in the Carbohydrates. The change of the 
 sugar of the plant sap into cellulose, or woody fiber, is more 
 or less observable in all plants. When they are growing 
 fastest the sugar is most abundant, not, however, in those 
 parts that are actually growing, but in those which convey 
 the sap to the growing parts. Thus the sugar of the ascend- 
 ing sap of the maple disappears in the leaf and extremities of 
 the twig, and sugar cane is sweet only a certain distance above 
 the ground, up to where the new growth is proceeding. In 
 the ripening of the ear, the sweet taste so perceptible in young 
 grain gradually diminishes, and finally disappears. The 
 sugar of the sap is here changed into the starch of the grain, 
 which is destined, when the grain sprouts, to be reconverted 
 into sugar for the nourishment of the growing grain. 
 
 In the ripening of fruits a different series of changes pre- 
 sents itself. The fruit is at first tasteless, then becomes 
 sour, and at last sweet. In this case, either the acid of the 
 unripe fruit is changed into the sugar of the ripened fruit, or 
 some of the other constituents of the fruit are converted into 
 sugar which disguises the acid. 
 
 344. Manufacture of Protein. Carbohydrates are not the 
 only chemical compounds that are produced in the leaf. A 
 
CHEMISTRY OF PLANT GROWTH 
 
 307 
 
 very important work of the leaf is the production of proteins, 
 the most complex compounds known. How these compounds 
 are manufactured is not known. Starting with the carbo- 
 hydrates, and the nitrogen, sulphur, and phosphorus secured 
 from the soil, the leaf cell builds up the very complex protein 
 molecule. Other parts of the plant manufacture protein to 
 some extent ; but its production goes on most actively in the 
 leaf, from which it is transported to other parts of the plant. 
 345. Some Plants Cannot Manufacture Food. Plants not 
 possessing chlorophyll are not able to decompose carbonic 
 acid and produce carbohydrates. Such plants must have 
 their carbonaceous and nitrogenous foods prepared for them. 
 Mushrooms and Indian pipe are examples of such plants. 
 They feed upon the compounds formed by the decaying or- 
 ganic matter in the soil. The fungi that grow on decaying 
 trunks of trees also belong to this class of plants. Some 
 colored plants, like the dodder, are parasites and live on the 
 juices of other plants. 
 
 EXERCISES 
 
 Ex. 211. Rub 50 kernels of barley in a mortar with a .little water. 
 Filter and test the water with Fehling's solution for reducing sugar. 
 What is the result ? Put 50 other barley 
 seeds between two thicknesses of moist 
 cotton flannel and place these between 
 two plates as shown in Fig. 150. Stand 
 the plates in a warm place for two or 
 three days or until the sprouts are about 
 half an inch high. Rub the germinated 
 seeds in the mortar as above and test with 
 Fehling's solution. What is the result? 
 What happened to the starch of the seed 
 during germination? To what was this 
 change due? Do similar changes take 
 place in the proteins of the seed ? 
 
 FIG. 150. A seed tester. 
 
308 APPLIED CHEMISTRY 
 
 Ex. 212. What conditions are necessary for the germination of 
 seeds ? Boil some water and when it is cold place it in a glass tumbler 
 and drop a few radish or wheat seeds on the surface. Note if there is 
 any difference in the seeds which float and those which sink. Explain. 
 
 Ex. 213. (Teacher) Place an inch of moist sawdust in the bottom 
 of three eight-ounce wide-mouth bottles, and drop a few radish or other 
 seeds on the sawdust. Cork one bottle tightly, and set it aside. Fill 
 another bottle with carbon dioxide by downward displacement and cork 
 it tightly. Fill the third bottle with oxygen by downward displace- 
 ment and cork it. Watch the bottles for several days and note any 
 difference in germination. Is oxygen necessary for germination ? Is 
 heat also necessary ? Dp seeds vary in the amount of warmth neces- 
 sary for germination? 
 
 Ex. 214. (Teacher) Place a vial of clear limewater in a wide- 
 mouth bottle and surround the vial with well-soaked seeds (Fig. 146). 
 Cork the bottle tightly and observe the limewater. What change 
 takes place ? How do you account for it ? 
 
 Note. As a check to the above another bottle might be arranged in 
 the same way except that perfectly dry seeds should be used. 
 
 Ex. 216. Pick some leaves from a vigorously growing plant in the 
 afternoon. Boil them in water for a few minutes and then immerse 
 them in hot alcohol to extract the chlorophyll. Dip the leaves in a 
 very dilute solution of iodine. Is there any evidence of starch ? How 
 did the starch get there ? Explain the production of carbohydrates in 
 the leaf. 
 
 Ex. 216. Cover half of a leaf while on the plant on both sides with 
 black paper or tin foil one afternoon and pick the leaf the next afternoon 
 and test for starch. Is there any difference in the two parts of the leaf ? 
 Explain. Pick leaves in the early morning and in the early evening 
 from the same plant. Test for starch in the usual way. Does electric 
 light have the same effect upon plant growth as sunlight ? Is there 
 sufficient carbon dioxide in the atmosphere for plant growth ? 
 
 Ex. 217. Is it correct to say that " plants breathe out oxygen during 
 the daytime " ? Explain what really happens. What is respiration ? 
 
 Ex. 218. Are proteins manufactured in the leaf? Can all plants 
 manufacture their own food? How do the fungi obtain their food? 
 How do the parasites obtain theirs? 
 
CHAPTER XXXVII 
 
 CHEMISTRY OF PLANT GROWTH (Continued} 
 
 346. Importance of Water to the Plant. Analysis of the 
 corn plant (334) shows that it contains nearly 80 per cent 
 water. There is also found in the organic matter an amount 
 of hydrogen and oxygen equal to about 10 per cent of the 
 entire plant, and it has been shown that these elements are 
 derived from water (340). 
 
 It is evident, then, that the plant obtains about 90 per 
 cent of its substance from water. This statement, however, 
 gives but little idea of the amount of water required by the 
 plant during its period of growth. The leaves of the grow- 
 ing plant are constantly exhaling water. This process is 
 known as transpiration. Very large amounts of water are 
 transpired by plants. 
 
 Experiments have shown that while producing one pound 
 of dry matter the plant gives off from 300 to 500 pounds 
 of water by transpiration. A fair crop of corn transpires 
 during the growing season at least 900 tons of water to the 
 acre, or an amount of water that would be equal to a layer 
 that would cover the entire acre about 8 inches deep. The 
 table that appears on the next page gives the average amount 
 of water transpired by some of the common farm crops, as 
 determined at the Wisconsin Experiment Station. 
 
 309 
 
310 
 
 APPLIED CHEMISTRY 
 
 AVERAGE AMOUNT OF WATER USED TO PRODUCE 
 ONE POUND OF DRY MATTER 
 
 CROP 
 
 WATER 
 
 Barley ... .... 
 
 461 1 pounds 
 
 Oats 
 
 503 9 pounds 
 
 
 270.9 pounds 
 
 Clover 
 
 576.6 pounds 
 
 Peas 
 
 477 2 pounds 
 
 Potatoes 
 
 385.1 pounds 
 
 
 
 347. How the Plant Obtains Its Water. All the water 
 used by the plant is absorbed from the soil by the plant roots. 
 The growing ends of the rootlets are 
 clothed with numerous root hairs 
 which are responsible for the absorp- 
 tion of the water needed by the plant. 
 The manner in which the root hairs 
 absorb water from the soil may be 
 illustrated by a simple experiment. 
 Tie a piece of moist animal mem- 
 brane (hog's bladder will serve the 
 purpose) over the end of a thistle 
 tube (Fig. 151), and when dry cover 
 the edge of the membrane with 
 melted paraffin, to make the joint 
 watertight. Fill the enlarged part 
 of the thistle tube with a strong solu- 
 tion of sugar or salt, and place the 
 tube in a glass of water, sinking it 
 until the level of the liquid in the 
 tube stands at the same height as 
 that in the glass. In a short time 
 
 Fl - 
 
CHEMISTRY OF PLANT GROWTH 311 
 
 the water begins to rise in the tube, and in time flows 
 over the top of the tube. The water passes through the 
 membrane by osmotic action, or osmosis. Whenever a mem- 
 brane like this one separates a strong solution from a weak one, 
 there is a decided movement of water from the weaker solu- 
 tion to the stronger, which tends to con- 
 tinue until the liquid is of the same con- 
 centration on both sides of the membrane. 
 
 Under the microscope the root hairs 
 (Fig. 152) are seen to be long tubelike 
 bladders. These root hairs are filled 
 with cell sap, which is a much more 
 concentrated solution than soil water ; 
 hence the water passes into the root 
 hairs by osmotic action. Once in the 
 root hairs the water passes on to the root 
 and stem and leaf, to be utilized in FlG 152 .*_ Root ^ of 
 growth or given off by transpiration. young radish plants. 
 
 348. Functions of Water in the Plant. Water is impor- 
 tant to the plant in several different ways. It is first of all 
 the most essential plant food in the sense that it furnishes the 
 material for 90 per cent of the weight of the plant. Water 
 is necessary to dissolve the plant food in the soil and enable 
 it to enter the plant, as will be noted later. It is also neces- 
 sary for the movement of food within the plant. The food 
 materials absorbed by the roots and those manufactured in 
 the leaves can be transported to the different parts of the 
 plant where they are needed only when in solution in water. 
 Water performs an important function in controlling the 
 temperature of the plant. Chemical processes in the plant 
 cell produce heat, and the excess of heat is removed by 
 transpiration of water through the leaves. 
 
312 
 
 APPLIED CHEMISTRY 
 
 
 Water is needed also to give stiffness or rigidity to the more 
 succulent parts of the plant. This fact is shown by the 
 drooping or wilting of plants during the hot hours of the day 
 when the water is not furnished by the roots with 
 sufficient rapidity to repair the loss by evapora- 
 tion from the leaves. In the experiment with 
 the thistle tube (Fig. 151) it was noted that the 
 water was raised to some height in the tube, and 
 consequently the walls of the tube must have 
 been subjected to some internal pressure. The 
 experiment may be performed in another way. 
 Tie a piece of bladder (A) over one end of a glass 
 tube (Fig. 153) and fill the tube with a strong 
 sugar solution. Over the other end fasten a piece 
 of thin sheet rubber (B), and place the bladder 
 end in a vessel of water. After some time it will 
 be found that the water absorbed has created 
 sufficient pressure to distend the rubber, and if 
 the rubber is punctured with a pin the water 
 will be ejected with some force. The pressure 
 FIG 153 crea ted by osmosis in this way is called osmotic 
 Apparatus to pressure. When the plant cells can obtain all 
 
 demonstrate * 
 
 osmotic pres- the water they need, they are kept distended 
 and rigid by osmotic pressure. When the water 
 is removed faster than it is absorbed, the osmotic pressure 
 is decreased, the cell loses its rigidity and finally the whole 
 plant droops or wilts. The protoplasm does its work 
 properly only when the cell is turgid, and, therefore, wilting 
 is always injurious to the plant. 
 
 349. How the Plant Obtains Its Mineral Matter. The 
 mineral matter, or ash, of the plant is obtained from the soil. 
 Small quantities of the different mineral substances used by 
 
CHEMISTRY OF PLANT GROWTH 313 
 
 the plant are found dissolved in the soil water. These dis- 
 solved materials diffuse into the root hairs by osmosis and 
 then, like the water, pass on to root and stem and leaf to be 
 utilized in plant growth. If none of these substances were 
 used by the plant, this diffusion would continue until there 
 was the same strength of each of the mineral substances in 
 the plant sap and in the soil water. When the plant uses one 
 of these substances, more will come into the root hairs in 
 order to preserve the equilibrium. Thus those substances 
 which are needed by the plant must come in as long as the 
 soil can furnish them in a soluble form. 
 
 350. Essential and Non-essential Elements. Although 
 the plant contains nitrogen and the nine ash elements which 
 it obtains from the soil, it does not follow that all of these ele- 
 ments are necessary to its growth. To determine which ele- 
 ments are essential, plants are grown in sand or by the water 
 culture method in such a way that they are supplied with all 
 the elements occurring in plants, with the exception of the 
 one element under investigation. If the plant grows to 
 maturity, the missing element is deemed non-essential; it 
 the plant fails to develop, that particular element is con- 
 sidered to be essential. These experiments indicate that 
 nitrogen, potassium, calcium, magnesium, iron, sulphur, and 
 phosphorus are absolutely essential to plant growth. Toward 
 chlorine, silicon, and sodium plants seem to be indifferent, 
 as they can grow to maturity in the absence of these elements. 
 
 Another important fact discovered in these experiments is 
 that one chemical element cannot be substituted for another 
 in plant growth, even when both elements are similar in 
 chemical properties. In the laboratory, for example, sodium 
 and potassium compounds are much alike in their action, 
 and one may be used in place of the other in many reactions ; 
 
314 
 
 APPLIED CHEMISTRY 
 
 but sodium cannot take the place of potassium as a plant 
 
 food (Fig. 154). 
 
 351. Roots Dissolve Mineral Substances. The plant not 
 
 only absorbs what is 
 already soluble in the 
 soil water, but it is 
 capable of making sol- 
 uble small quantities 
 of the insoluble sub- 
 stances which are pres- 
 ent in the soil and 
 which may be needed 
 for plant food. The 
 plant accomplishes 
 this result by means of 
 substances excreted by 
 the roots. If a plant 
 
 FIG. 154. Showing the effect of sodium (A) 
 
 and potassium (*) on plant growth. Jg gr()wn 
 
 sawdust placed on a piece of polished marble, it will be 
 found that the prints of the roots are distinctly shown on the 
 surface of the marble 
 (Fig. 155). Pieces of 
 limestone in the soil 
 often show markings due 
 to the solvent action of 
 plant roots. 
 
 352. The Nitrogen of 
 Plants. This element is 
 largely derived from the 
 nitrates in the soil which enter the root hairs by osmosis. 
 The plants known as the legumes obtain part of their nitrogen 
 from the nodules found on their roots. These are the 
 
 FIG. 155. Marble corroded by bean roots. 
 
CHEMISTRY OF PLANT GROWTH 315 
 
 homes of bacteria that have the power of fixing the nitrogen 
 of the air. They cause the nitrogen to combine with other 
 substances to form compounds which can be utilized as a 
 source of nitrogen for the manufacture of protein. Legumes 
 use the nitrates in the soil when they can obtain them, and 
 only fix atmospheric nitrogen when the supply of nitrate is 
 insufficient. 
 
 353. Functions of the Elements in Plant Growth. Car- 
 bon, oxygen, and hydrogen are constituents of all the organic 
 compounds manufactured by the plants. These three ele- 
 ments constitute about 98.5 per cent of the mature plant. 
 
 Nitrogen is a necessary constituent of the proteins, which 
 play an important part in the formation of protoplasm, 
 chlorophyll, and other compounds. Abundance of nitrogen 
 in the soil is indicated by the bright green color of the leaves. 
 
 Potassium is one of the most important elements in plant 
 growth. It is present in greatest amount in the leaves and 
 the actively growing parts of the plant. Apparently it 
 aids in the production of carbohydrates, such as starch and 
 sugar. Abundance of potassium is said to increase the 
 amount of sugar in fruits and in such roots as the sugar beet. 
 
 Calcium takes a prominent part in the production of new 
 tissue and in the development of strong cell walls and nu- 
 merous root hairs. It serves also as a base to precipitate 
 the poisonous oxalic acid which is formed by cell activities. 
 
 Magnesium assists in the formation of chlorophyll and the 
 proteins. It is necessary to seed formation, and seeds grown 
 with an insufficient supply of magnesium are often sterile. 
 
 Phosphorus is a necessary constituent of some proteins. 
 It is found mainly in the seeds. It increases the yield and 
 hastens the ripening of grain. Many proteins insoluble in 
 water are soluble in the presence of phosphorus compounds, 
 
316 
 
 APPLIED CHEMISTRY 
 
 Iron occurs in the smallest amount of any of the ash 
 elements but is always present in plants. It is necessary for 
 the formation of chlorophyll. 
 
 Sulphur is a necessary constituent of most proteins. It is 
 also a part of some of the flavoring oils, such as those found 
 in mustard, onions, cabbage, and horseradish. 
 
 EXERCISES 
 
 Ex. 219. Invert a wide-mouth bottle over a potted plant, first cover- 
 ing the soil with waxed paper. (Fig. 156.) What is the source of the 
 moisture that collects ? How much water do plants 
 transpire in producing a pound of dry matter ? How 
 much water is transpired by an acre of corn ? 
 
 Ex. 220. (Teacher) Perform the experiment 
 described in 347. How does it illustrate the move- 
 ment of water into the plant ? Germinate some 
 radish seeds between two layers of moist cloth 
 (Fig. 150) and examine the root hairs under the mi- 
 croscope. Are they well designed to absorb water ? 
 Ex. 221. (Teacher) Perform the experiment 
 illustrated in Fig. 153. How does water give rigid- 
 ity to the plant? Why do plants wilt? Is tur- 
 gidity of the cell necessary ? What are some of the 
 other functions of water in the plant? 
 
 Ex. 222. How does the plant obtain its mineral 
 matter? Describe an experiment to determine 
 which mineral elements are necessary. Name the essential elements. 
 
 Ex. 223. (Teacher) Place a slab of polished marble in a small box 
 and cover with an inch of moist sand. Plant seeds of peas or beans and 
 keep watered. After growth has proceeded for some time wash the 
 marble. Is there proof that the roots dissolved the marble ? 
 
 Germinate some radish seeds between pieces of blue litmus paper. 
 
 (Fig. 150.) What effect do the root hairs have on the litmus ? Is it 
 
 probable that roots have power of dissolving mineral food in the soil ? 
 
 Ex. 224. What is the source of the nitrogen used by the plant? 
 
 Discuss the functions of the different elements used in plant growth. 
 
 FIG. 156. Exper- 
 iment showing that 
 water is given off 
 from the leaves of 
 plants. 
 
CHAPTER XXXVIII 
 ENZYMES DIGESTION FERMENTATION 
 
 354. Enzymes. In studying the germination of seeds 
 (336) it was found that a substance called diastase which has 
 the power of changing starch into maltose is formed in the 
 seed. Diastase belongs to a group of substances known as 
 enzymes. They are the products of living cells but are not 
 themselves living things. Very little is known of the true 
 nature of enzymes or of their chemical action, as none of them 
 have been obtained in a state of absolute purity. They are 
 very complex substances of a protein character. They are 
 soluble in water and glycerin but are insoluble in alcohol. 
 For the purpose of study an enzyme is obtained by pulveriz- 
 ing the tissue, extracting the enzyme with glycerin, and then 
 precipitating it by the addition of alcohol. The material 
 obtained in this way is not a pure enzyme, but contains the 
 enzyme in a concentrated form. Diastase prepared from 
 malt in this way shows in a marked manner the property 
 of transforming starch into maltose. 
 
 The enzymes are specific in their action. Diastase, for 
 example, converts starch into maltose, but it has no effect 
 on other substances ; and in like manner each enzyme acts 
 on one particular substance, producing in it a definite change. 
 The enzymes behave like catalytic agents in that they them- 
 selves undergo no permanent change, but under proper con- 
 ditions can cause an almost indefinite amount of chemical 
 
 317 
 
318 APPLIED CHEMISTRY 
 
 change in the substance upon which they act. Thus one 
 part of diastase can change at least 2000 parts of starch into 
 maltose without any of the enzyme itself being destroyed. 
 
 355. Malt is a good example of the commercial utilization 
 of enzymic action. Malt is produced from barley by soaking 
 the grain in water for some time and then spreading it in thick 
 layers upon the floor of a warm room. Germination takes 
 place, and when the sprouts are about one half inch long, the 
 grain is heated sufficiently to kill the embryo, and then dried. 
 The sprouts are removed and sold as a cattle feed under the 
 name of malt sprouts. The remaining grain is known as malt. 
 The germinating process makes the diastase active, and if the 
 malt is now placed in warm water, the starch of the grain is 
 converted into maltose, which may be changed by the action 
 of yeast into alcohol, as is done in the manufacture of beer, 
 whisky, and ordinary alcohol. Since the amount of diastase 
 in the barley is capable of changing a large amount of starch 
 into maltose, other starchy materials, such as corn and rice, 
 are frequently added to the " mash." The residual grain, 
 after all the starch has been made soluble and thus removed, 
 is dried and sold as cattle feed under the name of dried 
 brewers' grains, or dried distillers' grains, according to whether 
 it comes from the brewery or the distillery. 
 
 356. Digestion. The process by which the insoluble 
 food materials are made soluble so they can be absorbed into 
 the blood of animals is called digestion. It is in large part, 
 if not wholly, the result of the action of several enzymes. 
 Digestion takes place in various parts of the alimentary canal, 
 notably in the mouth, stomach, and small intestines. 
 
 357. Digestion in the Mouth. The food is first ground into 
 fine particles by mastication so that the digestive juices can 
 act upon it to better advantage. During this process the food 
 
ENZYMES, DIGESTION, FERMENTATION 319 
 
 is thoroughly mixed with the saliva, which contains an en- 
 zyme known as ptyalin. This enzyme is much like diastase 
 in its action and changes the starch of the food into maltose. 
 
 2 C 6 H 10 O 5 
 
 starch 
 
 H 2 O 
 
 C 12 H 22 U . 
 
 maltose 
 
 The normal saliva is slightly alkaline, and ptyalin can act 
 only in an alkaline solution. No constituents of the food 
 other than starch are acted upon in the mouth, and not all 
 the starch is rendered soluble. The food material, thor- 
 oughly moistened, passes into the stomach, where the next 
 change takes place. 
 
 358. Digestion in the Stomach. In man, the horse, and 
 the pig there is but one stomach, but in the ruminants, like 
 cattle and sheep, 
 there are four stom- 
 achs (Fig. 157) or 
 rather four com- 
 partments to the 
 stomach. Animals 
 of the latter class 
 chew the cud. The 
 food is passed from 
 the mouth into the 
 first and second 
 compartments of 
 the stomach, and is then forced back into the mouth for 
 further mastication ; then it is swallowed again and passed 
 through the third stomach into the fourth for final digestion. 
 The storage in the first and second stomach and the re- 
 peated mastication of the food merely serve to grind the 
 food completely and to prepare it thoroughly for digestion. 
 
 FlO. 157 The four main divisions of a ruminant's 
 stomach. 
 
320 APPLIED CHEMISTRY 
 
 In this way these animals are able to digest fibrous material 
 to a much greater extent than other animals, such as the 
 horse. The true gastric digestion in the case of ruminants 
 takes place in the fourth stomach. 
 
 The glands in the wall of the stomach secrete a digestive 
 fluid, called gastric juice, which, unlike the saliva, is acid 
 in reaction and contains about 0.2 per cent of hydrochloric 
 acid. It also contains two enzymes pepsin and rennin. 
 The pepsin acts upon the insoluble proteins and gradually 
 converts them into peptones, which are soluble and diffusible. 
 Pepsin acts only in an acid solution. Rennin, the other 
 enzyme of the gastric juice, acts on the casein of milk, causing 
 it to coagulate or curdle, a process the necessity of which is 
 not understood. The coagulated casein is then dissolved 
 by the pepsin. Rennin is especially abundant in the stomach 
 of the young, and the commercial rennet used in cheese mak- 
 ing is prepared from the stomachs of young calves. No 
 food constituents save the proteins are acted upon by the 
 stomach enzymes, and they are not completely digested but 
 in part pass on into the small intestine. 
 
 359. Digestion in the Intestine. When the food reaches 
 the small intestine it comes in contact with the intestinal and 
 pancreatic juices. These fluids have an alkaline reaction 
 and contain several enzymes. 
 
 Trypsin is an enzyme that acts upon the proteins which 
 escape digestion in the stomach. It is more energetic in its 
 action than is pepsin. It acts only in an alkaline solution. 
 
 Amylopsin is a pancreatic enzyme that acts on starch, 
 converting it into maltose, and is more energetic in its action 
 than ptyalin. 
 
 Steapsin, or lipase, is an enzyme that acts upon the fats 
 of the food. It hydrolyzes fats into glycerin and fatty acids 
 
ENZYMES, DIGESTION, FERMENTATION 321 
 
 (298), which is probably the first step in their digestion. 
 Steapsin and amylopsin are active only in alkaline solution. 
 
 360. Bile is a fluid secreted by the liver and discharged 
 into the small intestine together with the pancreatic juice. 
 It is a thin liquid, with a bitter taste, and is very alkaline. It 
 varies in color from greenish-yellow to reddish-brown, the 
 shade depending on the animal. No enzymes have been dis- 
 covered in the bile, but its presence decidedly increases the 
 power of the pancreatic enzymes. 
 
 The various food materials that have been changed into 
 soluble compounds by the action of the digestive enzymes 
 are absorbed from the small intestines and ultimately find 
 their way into the blood to be transported to the part of the 
 body where they are needed. The part of the food that is 
 not changed into soluble compounds passes on into the large 
 intestine and is finally excreted in the feces, which, there- 
 fore, represent in a general way the undigested food. 
 
 361. Other Enzymes. The enzymes mentioned in this 
 chapter are only a few of the many whose existence is known, 
 and new ones are being constantly added to the list. The 
 pineapple is known to contain an enzyme that digests pro- 
 tein. Some enzymes bring about oxidation by causing the 
 union of substances with the oxygen of the air. Such 
 enzymes are called oxidases. The brown coloration which ap- 
 pears on the cut surface of an apple or other fruit is said to 
 be caused by the action of an oxidase. The enzymes studied 
 herein assist in breaking complex substances into simple 
 bodies, but there are undoubtedly enzymes that produce 
 opposite results. The synthesis of starch in the leaves and 
 the production of proteins, as well as many other processes 
 of the plant and animal body are thought by some investiga- 
 tors to be dependent upon the presence of enzymes. 
 
 EV. CHEM 21 
 
322 APPLIED CHEMISTRY 
 
 362. Fermentation is a term applied to changes in 
 organic substances that are brought about through the 
 growth of microscopic plants, such as yeast, molds, or 
 bacteria. The production of alcohol by the action of yeast 
 is the best-known example of fermentation. The souring of 
 milk, the change of cider to vinegar, and the decay of or- 
 ganic substances are examples of fermentation caused by 
 bacteria. It was formerly thought that the growing cells 
 themselves produced the chemical changes incident to the 
 fermentation, but many investigators now believe that the 
 yeasts, or bacterial cells, produce enzymes that are really 
 responsible for the chemical changes in the fermenting mate- 
 rial. It was found that a sample of yeast, for instance, that 
 was ground in such a way as to rupture every cell and thus 
 destroy its life, still had the power of producing alcoholic 
 fermentation. It is now said that yeast contains at least 
 two enzymes : namely, invertase, which has the power of 
 inverting cane sugar, and zymase, which converts invert sugar 
 or maltose into alcohol and carbon dioxide. 
 
 EXERCISES 
 
 Ex. 225. Crush 20 malted barley grains in a mortar. Transfer to 
 a test tube, add 15 cc. of water, and allow the mixture to stand twenty- 
 four hours. Filter off the solution and add to a bottle containing 
 100 cc. of starch solution made as follows : rub one gram of starch with 
 10 cc. of water until smooth and then pour on 100 cc. of boiling water 
 and allow the liquid to cool. Allow the mixture to stand another 
 twenty-four hours. Test a portion of it for starch. State the result. 
 Test another portion with Fehling's solution. State the result. What 
 change has taken place in the starch? What caused this change? 
 What is the active principle of the malt ? What are enzymes ? Are 
 they specific in their action? Explain. Are they catalytic agents? 
 What commercial use has the enzymic action of malt? What are 
 dried brewers* grains? 
 
ENZYMES, DIGESTION, FERMENTATION 323 
 
 Ex. 226. Fill a test tube one third full of your saliva. If the saliva 
 does not flow freely chew a piece of paraffin. Add to the saliva an equal 
 volume of starch solution prepared as in the last exercise. Place the test 
 tube in a cup of water at blood heat for an hour. Test a portion of mix- 
 ture for starch. If the starch has not all disappeared, allow the mixture 
 to stand another hour. What change has the saliva caused in the 
 starch ? How did you test for starch ? What is the enzyme of the sa- 
 liva ? How is the food affected in the mouth ? Is the saliva acid, or 
 alkaline, or neutral ? 
 
 Ex. 227. What enzymes are found in the stomach ? Review Exer- 
 cise 200. Repeat that experiment, substituting a tablespoonful of 
 ground lean meat for the white of the egg. State the result. Does 
 pepsin act best in an acid or alkaline solution ? Compare with ptyalin. 
 What action does the rennin of the gastric juice have on milk ? 
 
 Ex. 228. What three enzymes are found in the intestines? State 
 the action of each. What effect does the bile have on digestion ? 
 
 Ex. 229. Explain what is meant by fermentation. Give examples. 
 Do enzymes play any part in fermentations ? Are enzymes concerned 
 in any processes other than digestion and fermentations ? What causes 
 the brown coloration of the cut surface of an apple? (Note. If an 
 apple is cut in two and placed in a bottle containing sulphur dioxide 
 for a short time, the cut surface will not turn brown when exposed to the 
 air as the sulphur dioxide destroys the enzyme oxidase.) Are enzymes 
 ever supposed to take part in building up complex compounds ? 
 
CHAPTER XXXIX 
 PRINCIPLES OF NUTRITION 
 
 363. Uses of Food. The animal body uses the foods for 
 the following purposes : (1) to repair the waste of the system ; 
 (2) to supply heat ; (3) to furnish motion ; (4) to provide 
 the materials needed for the increase of flesh by growth or 
 fattening; (5) to make special products, such as. milk, eggs, 
 feathers, wool, and hair. The animal body may in many 
 ways be compared to the gasoline engine or other " prime 
 motor." The gasoline engine requires two things for its 
 operation : (1) sufficient repair material to keep its working 
 parts in running order, and (2) a supply of fuel in proportion 
 to the work to be done. The same two things are needed by 
 the animal ; namely, repair material and fuel. 
 
 364. Repair Material. The repair material for any ma- 
 chine must be of the same kind as that of which the machine 
 is made. Protein is the characteristic ingredient of the ani- 
 mal mechanism ; for the muscles with which the animal does 
 its work are largely composed of protein, and this material 
 is broken down and destroyed at a fairly uniform rate by the 
 operation of the animal machine. Since the bodily machin- 
 ery is running all the time, whether any external work is being 
 done or not, this loss is going on continually. The body 
 differs from the engine in being self-repairing, but as the ani- 
 mal does not have the power to manufacture proteins, it is 
 absolutely dependent for its repair material on the proteins 
 of its food. This protein is needed for two purposes. 
 
 324 
 
PRINCIPLES OF NUTRITION 325 
 
 First, it is necessary for repair material in the strict sense ; 
 namely, to make good the wear and tear of the body machin- 
 ery. The amount needed for the purpose is small, and is not 
 materially greater when the animal is doing work than when 
 it is not. A second purpose for which protein and ash are 
 needed in the growing animal is to furnish the material for 
 enlarging its body. Protein is necessary also to enable the 
 animal to manufacture milk, eggs, hair, wool, and other 
 special products ; for all of these contain proteins, which the 
 animal must obtain from its food. 
 
 365. Food as a Source of Repair Material. The value of 
 a food or feeding stuff as a source of protein evidently de- 
 pends in the first place on the amount of protein which it 
 contains. Beans, containing 23 per cent of protein, are, other 
 things being equal, a better source of protein than corn, which 
 contains only 10 per cent. Since the protein of the food must 
 be capable of being digested by the animal, the most valuable 
 source of repair material is the food or feeding stuff contain- 
 ing the largest amount of digestible protein (368). 
 
 366. Fuel or Energy Materials. The animal requires 
 heat to maintain the body temperature and energy to do 
 its work. The source of this heat and energy is the food 
 which the animal digests, and which is oxidized in its body. 
 Since the animal machinery is running continually, it re- 
 quires a constant supply of fuel material, the amount neces- 
 sary depending upon the amount of work done. This con- 
 sists chiefly of the carbohydrates and fats of the food, 
 although if more protein is fed than is required for repair 
 and construction purposes, it may be used as fuel. The un- 
 necessary use of protein as fuel material is wasteful, as 
 protein is ordinarily much more expensive than are carbo- 
 hydrates and fats. 
 
326 
 
 APPLIED CHEMISTRY 
 
 367. Fuel Value, or Energy Value, of Foods. TKe differ- 
 ent foods and food constituents are not all of equal value as 
 sources of energy. It will be found convenient to have a 
 means of comparing the different foods and feeds, and the best 
 basis for such a comparison is the relative energy values of 
 these materials . Anything which has the capacity to do work 
 is said to possess energy. The fuel of the engine and the food 
 of the animal possess energy, since they enable the engine or 
 the body to do work. This energy is stored up as latent 
 
 energy, and when the fuel is 
 burned in the engine, or the food is 
 oxidized in the body, this latent 
 energy is set free and part of it is 
 converted into the work, the rest 
 escaping as heat. The value of 
 a fuel depends on the amount of 
 this latent energy it contains, and 
 this can be determined by burning 
 the substance to convert the latent 
 energy into heat, and then measur- 
 ing the heat produced. 
 
 The fuel value of a food is de- 
 termined by burning a weighed 
 quantity of the food in a calorim= 
 eter (Fig. 158). This is a metal vessel or bomb, which is 
 immersed in a vessel of water. The heat produced by the 
 burning substance warms the water, and the rise in tempera- 
 ture is determined by a thermometer. Various units have 
 been employed in measuring heat. Perhaps the oldest and 
 most common is the calorie (spelled with a small c) which is 
 the amount of heat necessary to raise the temperature of one 
 gram of water one degree centigrade. This unit is so small 
 
 FIG. 158. A calorimeter. 
 
PRINCIPLES OF NUTRITION 
 
 327 
 
 that it has long been customary in discussing foods to use the 
 large Calorie (spelled with a capital C), which is equivalent 
 to 1000 small calories, or, in other words, is the amount of 
 heat required to raise the temperature of one kilogram (1000 
 grams) of water one degree. In discussing the feeding of 
 farm animals even the large Calorie is found to be an incon- 
 veniently small unit, and some writers make use of the therm, 
 which is equivalent to 1000 large Calories ; that is, it is the 
 amount of heat required to raise the temperature of 1000 
 kilograms of water one degree centigrade. 
 
 A pound of either carbohydrates or protein when burned 
 produces 1860 large Calories of heat, or 1.86 therms. A 
 pound of fat, which is a much more concentrated fuel, pro- 
 duces 4225 Calories, or 4.23 therms of heat. It will be seen 
 that the pound of fat produces approximately two and one 
 fourth times as much heat as an equal weight of carbohydrates 
 or protein. The following examples serve to illustrate the 
 great variation in the energy value of different foods : 
 
 FOOD 
 
 ENERGY VALUE PER 
 POUND 
 
 
 Calories 
 
 C abb a fire 
 
 170 
 
 Potatoes 
 
 380 
 
 Eeers . 
 
 720 
 
 Wheat flour 
 
 1660 
 
 Cheese 
 
 1990 
 
 Butter 
 
 3600 
 
 
 
 It has been shown that only the protein that is digested 
 is of any use to the animal body, and it is equally true that 
 only the digested part of the food can supply the animal with 
 
328 APPLIED CHEMISTRY 
 
 energy. The undigested part, which passes off in the excre- 
 ment, represents that part of the energy that cannot be uti- 
 lized by the animal machine. To determine how much energy 
 a food will furnish, it is necessary to know what proportion 
 of the food is actually digested ; and that can be determined 
 only by experiments with animals. 
 
 368. Digestion Experiments. The digestibility of a food 
 is determined by a carefully conducted digestion experiment. 
 The animal, or man, is fed for a few days on the food to be 
 investigated, the food having been analyzed to determine its 
 content of protein, fat, carbohydrates, fiber, and other 
 constituents; and the amount eaten is carefully recorded. 
 The f eces, which represent the undigested part of the food, are 
 collected, weighed, and analyzed. The difference between 
 the undigested nutrients and the total amounts in the food 
 consumed is the amount digested, which is then calculated 
 on a percentage basis. For example, suppose the analysis 
 of the food shows that the animal consumed four pounds of 
 protein during the experimental period, and that the feces 
 contained one pound of protein. . The animal, then, was able 
 to digest three pounds of protein out of the four pounds con- 
 sumed. In other words, three fourths, or 75 per cent, of the 
 protein was digestible. In the same way the percentage of 
 digestibility may be worked out for the fats, ash, and each of 
 the other nutrients of the food. Some authors use the ex- 
 pression coefficient of digestibility to designate the percentage 
 of a nutrient which can be digested. In the above-assumed 
 example the coefficient of digestibility for protein is 75. 
 
 369. Available Energy of Foods. Only that part of the 
 food which is digested can furnish energy to the animal ma- 
 chine, and not all of this energy can be utilized by the body. 
 Some of the digested portion of the food fails to undergo 
 
PRINCIPLES OF NUTRITION 329 
 
 complete oxidation in the body and is excreted in the licjuid 
 excrement. The energy that can be utilized is called the 
 available energy of the food. It is determined by finding the 
 total number of Calories in the food, and subtracting there- 
 from the caloric value of the feces as well as the caloric value 
 of the compounds found in the liquid excrement. 
 
 370. Net Energy of Foods. In the process of digestion, 
 particularly of coarse fodders, a part of the energy of the 
 food is used to separate the real fuel material from the 
 relatively large proportion of useless material in the food. 
 The energy thus used up in carrying on the process of diges- 
 tion is not available for other purposes. It is possible to 
 determine the approximate amount of energy required by 
 the animal in order to chew the food and digest it, and this 
 amount subtracted from the available energy gives the net 
 energy of the food. In the case of coarse fodders a large part 
 of the available energy is used in digestion, leaving compara- 
 tively little net energy. Less energy is required to digest 
 grains, and thus a larger proportion of their energy can be 
 used fqr other purposes by the body. The total fuel value 
 of one pound of timothy hay, for example, is 1751 Calories, 
 but its net energy value is only 335 Calories. The total fuel 
 value of corn meal is 1709 Calories and its net energy value is 
 888 Calories. Therefore, while the total fuel value of these 
 two substances is not very different, there is a marked con- 
 trast in the amount of net energy which they furnish. 
 
 If the fuel materials supplied in the food are just adequate 
 to the work to be done, they are all burned up as a source 
 of power. If more are supplied than are immediately needed, 
 the body is able to store the surplus for future use. Most 
 of the surplus fuel is converted into fat, which, therefore, is 
 the reserve fuel of the body. In fattening, the body is accu- 
 
330 APPLIED CHEMISTRY 
 
 mulating a surplus against future needs. If the food later 
 becomes insufficient, this store is drawn upon and the animal 
 becomes thin. Similarly, in growth and milk production, 
 the animal sets aside a part of the supply of both repair and 
 fuel material in its food for its own growth or for the use of 
 its young. Man takes advantage of these tendencies of the 
 animal to store fat and meat, and to produce milk, and di- 
 verts the resulting products to his own use as repair and 
 fuel material for his own body. 
 
 EXERCISES 
 
 Ex. 230. What five general uses does the animal make of its food ? 
 Why is the animal body likened to a prime motor engine? What 
 furnishes the repair material for the animal body? What other use 
 does' the animal have for protein? Does the value of food for repair 
 depend on the total protein or upon the digestible protein ? 
 
 Ex. 231. What are the chief energy supplying substances in the 
 food ? How is the total energy value of a food determined ? What is 
 the measure of heat ? What is meant by the small calorie ; the large 
 Calorie ; the therm ? How much heat is produced by burning a pound 
 of protein or carbohydrate ? A pound of fat ? Do foods varv^ greatly 
 in their energy value ? 
 
 Ex. 232. Does digestibility affect the amount of energy which 
 the food will supply to the animal ? How is a digestion experiment con- 
 ducted ? What is meant by the available energy of the food ? How 
 is it determined ? 
 
 Ex. 233. What is meant by net energy ? In what way does it differ 
 from available energy? Can all the available energy be utilized to 
 do work ? Explain. Can all the net energy be used to do work ? Is 
 some energy required to prepare the food and to digest it ? How does 
 the proportion of net energy from seeds compare with that from fodders ? 
 If the net energy supplied is more than is used, what becomes of the ex- 
 cess ? Can the animal use its own body fat to supply energy upon occa- 
 sion ? Is energy needed to produce milk and growth ? 
 
CHAPTER XL 
 FEEDING FARM ANIMALS 
 
 371. Balanced Rations. It has been noted that food sup- 
 plies the animal with repair material and with energy, both of 
 which it needs to carry on its various functions. The amount 
 of repair material and energy required by the animal depends 
 upon the following factors : whether the animal is growing, or 
 is working, or is producing milk. A ration that will supply 
 the animal with protein and energy in just the proportion in 
 which it needs them is called a balanced ration. A knowledge 
 of the food requirements of animals and of the method of cal- 
 culating balanced rations should be of value to the practical 
 feeder. 
 
 372. The maintenance requirement of the animal is used 
 as the basis for calculating the balanced ration. Since the 
 animal machine cannot be stopped when it fe not in active 
 use, it requires a continual supply of food. The amount of 
 food that is required simply to support the animal is desig- 
 nated as the maintenance requirement. It is the amount 
 required simply to maintain the animal when it is doing no 
 work and producing nothing. It represents the least amount 
 on which life can be maintained. A large animal needs more 
 food for maintenance than does a small one, although the 
 difference is not exactly proportional to the weight, but ap- 
 pears rather to be approximately proportional to the body 
 surface of the animal. The proper maintenance require- 
 ments have been determined by experiment for different 
 
 331 
 
332 
 
 APPLIED CHEMISTRY 
 
 kinds of animals, of various ages and weights. The follow- 
 ing table gives the figures for cattle of four different weights. 
 
 MAINTENANCE REQUIREMENTS FOR CATTLE 
 
 WEIGHT 
 
 DIGESTIBLE PROTEIN 
 
 NET ENERGY 
 
 Pounds 
 
 Pounds 
 
 Therms 
 
 750 
 
 0.40 
 
 4.95 
 
 850 
 
 0.45 
 
 5.60 
 
 1000 
 
 0.50 
 
 6.00 
 
 1250 
 
 0.60 
 
 7.00 
 
 373. Requirements for Growth. The amount and nature 
 of the food consumed should vary with the period of growth 
 as well as with the size of the animal. Rations for young 
 growing animals should contain proportionately more digest- 
 ible protein and less energy value than rations for mature 
 animals. This is because more food is required for building 
 purposes in the early stages of growth than in the later stages, 
 when the demand is more for heat and energy. When an 
 excess of fats and starchy foods is given to young animals, 
 there is a tendency to produce poor muscular tissue and 
 premature fattening. The ash of the food is also very im- 
 portant to young animals, for it is during the growing period 
 that the bones are built up. A table showing the protein and 
 energy requirement for growing animals will be found at the 
 end of this chapter. 
 
 374. Requirements for Work. The performance of work 
 by the animal calls for an additional supply of energy in the 
 feed. Animals when doing medium or heavy work also 
 require more protein than do those at light work. 
 
FEEDING FARM ANIMALS 333 
 
 REQUIREMENTS FOR THE WORKING HORSE OF 1000 POUNDS 
 
 CHARACTER OP WORK 
 
 DIGESTIBLE 
 PROTEIN 
 
 NET ENERGY 
 
 
 Pounds 
 
 Therms 
 
 For liffht work 
 
 1 
 
 9 80 
 
 
 1.4 
 
 1240 
 
 
 2.0 
 
 1600 
 
 
 
 
 375. Requirements for Fattening. When the animal con- 
 sumes more energy-making foods than it can utilize, it stores 
 the surplus energy as fat. To fatten animals, then, they are 
 fed abundant rations high in net energy value. It is esti- 
 mated that about 3.5 therms in addition to the maintenance 
 requirement are needed by the animal for each pound of gain 
 in weight during the fattening period. 
 
 376. Requirements for Milk Production. Of all forms of 
 animal production that of milk is the most variable and 
 most influenced in its amount by the feed supply. Milk is 
 the natural food of the young, and, as it is the only food of 
 the very young animal, it contains the protein, the ash, and 
 the energy necessary to its growth. When a cow is produc- 
 ing milk, she must have in addition to her maintenance 
 ration an amount of food sufficient to enable her to put 
 protein and energy materials into her milk. To produce 
 a pound of average milk requires 0.05 pound of digestible 
 protein and 0.3 therm of energy, which must be added 
 to the maintenance ration for each pound of milk the cow 
 produces. 
 
 377. Dry Matter in Rations. It has been found by experi- 
 ment that it is necessary for cattle to have a certain bulk 
 
334 APPLIED CHEMISTRY 
 
 in their feed. They do not thrive so well if the feed is too 
 concentrated, but on the other hand there might be such 
 a thing as having a ration which is too bulky. The best 
 indication of bulk in the feed is the dry matter which it 
 contains. In a general way it may be said that an animal 
 weighing 1000 pounds should be given from 20 to 30 pounds 
 of dry matter a day, the exact amount not being very impor- 
 tant if kept within these limits. On the farm, where hay and 
 fodder are abundant, it is usually easy to obtain a ration 
 that is sufficiently bulky. 
 
 378. The Ash of the Ration. The ash, or mineral matter, 
 of the feed is important ; for the animal could not live 
 very long if there were no mineral matter whatever in the 
 feed. It is especially important to young, growing animals, 
 as they are building up bones which are composed very 
 largely of mineral matter. As the animal grows older, it 
 needs less ash in the feeds, since the bones are no longer 
 growing in size. 
 
 379. Calculating a Balanced Ration. With the data of 
 this chapter at hand it is possible to calculate rations suited 
 to the various needs of the domestic animals. To illustrate 
 the method of calculation, it is assumed that a ration is 
 needed for a cow weighing 850 pounds and producing 20 
 pounds of average milk each day. The feeds are to be 
 selected from the table given at the end of this chapter. 
 
 By referring to page 332 it is seen that a cow weighing 
 850 pounds requires for maintenance 0.45 pound of digestible 
 protein and 5.60 therms of energy. For the production of 
 20 pounds of milk of average quality there would be required 
 according to the figures given in paragraph 376 : 
 
 Digestible protein (0.05 X 20) 1 pound 
 
 Net energy value (0.3 X 20) 6 therms 
 
FEEDING FARM ANIMALS 
 
 335 
 
 The total feed requirements for a day for such a cow are, 
 therefore, 1.45 pounds of digestible protein and 11.60 therms 
 of net energy. 
 
 The problem is to find a mixture of feeds that will give 
 these amounts of protein and energy. As the coarse feeds 
 grown on the farm are usually the cheapest, they should be 
 used as far as possible. First, corn silage and clover hay 
 may be tried for roughage, as the coarse feeds are called, and 
 corn meal and wheat bran for the more concentrated feeds. 
 It is necessary to start with the best guess possible as to the 
 amounts of each feed to use and make a table showing the 
 results as below : 
 
 RATION 
 
 DRY MATTER 
 
 DIGESTIBLE 
 PROTEIN 
 
 NET ENERGY 
 VALUE 
 
 Pounds 
 
 Pounds 
 
 Pounds 
 
 Therms 
 
 
 5.63 
 
 0.26 
 
 364 
 
 Clover hay 6 
 
 5.08 
 
 .32 
 
 208 
 
 Corn meal 5 ..... 
 
 4.46 
 
 .34 
 
 444 
 
 Wheat bran 2 .... 
 
 1.77 
 
 20 
 
 96 
 
 
 
 
 
 Total 
 
 1694 
 
 1 12 
 
 11 12 
 
 
 
 
 
 A comparison of these totals with the requirement of 1.45 
 pounds of protein and 11.60 therms of energy shows that the 
 ration is slightly low. in energy and considerably so in protein. 
 If the addition of some feed high in digestible protein, say 1^- 
 pounds of gluten feed, is made the ration stands thus : 
 
 RATION 
 
 DRY MATTER 
 
 DIGESTIBLE 
 PROTEIN 
 
 NET ENERGY 
 VALUE 
 
 Pounds 
 
 Pounds 
 
 Therms 
 
 In feeds named above . 
 In 1^ pounds gluten feed . 
 
 16.94 
 1.38 
 
 1.12 
 .30 
 
 11.12 
 1.19 
 
 Total 
 
 18.32 
 
 1.42 
 
 12.31 
 
336 
 
 APPLIED CHEMISTRY 
 
 This ration gives more nearly the correct amount of digest- 
 ible protein, but has a surplus of energy, which would prob- 
 ably tend to fatten the cow instead of increasing the flow of 
 milk. The energy in the ration should be reduced without 
 decreasing the amount of protein. If one pound of corn 
 meal, which supplies chiefly energy, is omitted, and replaced 
 by one half pound of gluten feed, the ration is as follows : 
 
 
 RATION 
 
 DRY MATTER 
 
 DIGESTIBLE 
 PROTEIN 
 
 NET ENERGY 
 VALUE 
 
 
 Pounds 
 
 Pounds 
 
 Pounds 
 
 Therms 
 
 Corn silage 
 
 22 .... 
 
 563 
 
 026 
 
 3 64 
 
 Clover hay 
 
 6 
 
 508 
 
 032 
 
 208 
 
 Corn meal 
 
 4 
 
 3.56 
 
 027 
 
 355 
 
 Wheat bran 
 
 2 
 
 1.77 
 
 020 
 
 096 
 
 Gluten feed 
 
 2 
 
 1 84 
 
 040 
 
 1 59 
 
 
 
 
 
 
 Total 
 
 
 1788 
 
 1 45 
 
 11 82 
 
 
 
 
 
 
 The ration now agrees very closely with the computed re- 
 quirements. This example will serve to illustrate the method 
 of calculating all rations ; for the same method will apply to 
 the rations for fattening cattle, for horses, for sheep and 
 swine, and for chickens, if the standards for each kind of ani- 
 mal are known. By proceeding in the manner described, 
 with a little patience a ration corresponding as closely as is 
 necessary to the standard requirements can be calculated. 
 Experience makes it possible to guess pretty closely the first 
 time, and the computation soon becomes easy. 
 
 380. Individuality. The standard requirements, of course, 
 are for average animals, but it is well known that some 
 animals require more feed than the average and some less. 
 The wise feeder, therefore, uses the standards with this fact 
 in mind, and in addition to calculating his standard ration 
 
FEEDING FARM ANIMALS 
 
 337 
 
 makes an individual study of each cow in his herd, feeding 
 her any amounts for which she will give profitable returns. 
 Even such a feeder, however, needs the standard requirements 
 as a starting point in his study. 
 
 381. Palatability of Feeds. There is another factor in 
 feeding animals which is quite as important as that of bal- 
 ancing the ration ; namely, the matter of the palatability 
 of the ration. In order to give the best results the food 
 should be relished by the animal. The experienced feeder 
 strives to compound a ration that carries the proper propor- 
 tion of protein and energy and is pleasing to the animal's taste. 
 
 382. Older Feeding Standards. The feeding standards that 
 have been most commonly used in the past by writers on the 
 feeding of animals are those known as the Wolff-Lehman 
 standards. These standards, instead of being based on the 
 daily requirements of the animal for digestible protein and 
 energy, are based on the theory that the animal must have 
 a given weight of dry matter each day, together with a defi- 
 nite amount of the three digestible nutrients protein, car- 
 bohydrates, and fat. The following table gives a few of 
 the feeding standards according to the Wolff-Lehman tables : 
 
 DAILY REQUIREMENT OF DIGESTIBLE NUTRIENTS FOR 
 EACH 1000 POUNDS LIVE WEIGHT OF ANIMAL 
 
 ANIMAL 
 
 DRY 
 
 MATTER 
 
 PROTEIN 
 
 CARBOHY- 
 DRATES 
 
 FAT 
 
 
 Pounds 
 
 Pounds 
 
 Pounds 
 
 Pounds 
 
 Cows giving 22 pounds of milk 
 daily 
 
 29 
 
 2.5 
 
 13.0 
 
 0.5 
 
 Fattening cattle 
 
 30 
 
 2.5 
 
 150 
 
 0.5 
 
 Sheep 
 
 23 
 
 1.5 
 
 120 
 
 0.3 
 
 Horses, medium work . . . 
 Fattening swine . 
 
 24 
 36 
 
 2.0 
 
 45 
 
 11.0 
 250 
 
 0.6 
 0.7 
 
 
 
 
 
 
 EV. CHEM. 22 
 
338 APPLIED CHEMISTRY 
 
 The method of calculating a ration according to these 
 standards is exactly the same as the one described on page 
 335, except that in the case of the Wolff-Lehman standards 
 there are four factors to be balanced, while in the other case 
 only two items, protein and energy, are considered. In the 
 case of the Wolff-Lehman standards, the best possible guess 
 is made as to the feeds that will fit the standard, and then 
 others are added or subtracted from the ration, as described 
 in the foregoing example, until a mixture is obtained that 
 agrees very closely with the amounts of dry matter, protein, 
 carbohydrates, and fat as stated in the standard. These 
 older standards are being replaced by those based on pro- 
 tein and energy. Tables giving all the Wolff-Lehman 
 standards, as well as the percentages of the different di- 
 gestible nutrients in the common feeding stuffs, may be 
 found in the larger works on the feeding of farm animals. 
 
 383. The nutritive ratio of a feed or a ration is the pro- 
 portion between the digestible protein and the sum of the 
 digestible carbohydrates and fat contained therein. To find 
 the nutritive ratio the fat is multiplied by 2.25, because 
 it has 2.25 times the food value of the carbohydrates, and 
 the result is added to the carbohydrates. The sum is di- 
 vided by the digestible protein, the quotient being the nutri- 
 tive ratio. Thus, the standard for a horse at medium 
 work calls for 2.0 pounds digestible protein, 11.0 pounds 
 carbohydrates, and 0.6 pound of fat. 
 .6X2.25 = 1.350; 1.350 + 11.0 = 12.35; 12.35^2.0 = 6.17 
 
 The nutritive ratio, therefore, is 1 to 6.17. 
 
 Recent investigations indicate that the ratio between pro- 
 tein and the other nutrients is not so important as it was first 
 thought to be, provided that the animal is supplied with 
 sufficient repair material or protein. 
 
FEEDING FARM ANIMALS 
 
 339 
 
 TABLES: ESTIMATED REQUIREMENTS PER DAY AND HEAD 
 FOR GROWING ANIMALS 
 
 CATTLE 
 
 SHEEP 
 
 AGE 
 
 Months 
 
 LlVEWT. 
 
 Pounds 
 
 DIGESTI- 
 BLE 
 
 PKOTEIN 
 Pounds 
 
 NET 
 ENERGY 
 
 Therms 
 
 AGE 
 
 Months 
 
 LIVE WT. 
 Pounds 
 
 DIGESTI- 
 BLE 
 
 PROTEIN 
 Pounds 
 
 NET 
 ENERGY 
 
 Therms 
 
 12 
 
 18 
 24 
 
 425 
 
 650 
 
 850 
 
 1000 
 
 1.30 
 1.65 
 1.70 
 1.75 
 
 6.0 
 7.0 
 7.5 
 
 8.0 
 
 6 
 
 12 
 
 18 
 
 70 
 110 
 145 
 
 0.30 
 0.23 
 0.22 
 
 1.30 
 1.40 
 1.60 
 
 CONSTITUENTS IN 100 POUNDS OF FEEDING STUFFS 
 
 FEEDING STUFFS 
 
 DRY MATTER 
 Pounds 
 
 DIGESTIBLE 
 
 PROTEIN 
 OR REPAIR 
 MATERIAL 
 
 Pounds 
 
 NET ENERGY 
 Therms 
 
 Coarse Feeds 
 
 Corn silage 25.6 
 
 Alfalfa hay 91.6 
 
 Clover hay 84.7 
 
 Corn fodder 57.8 
 
 Corn stover 59.5 
 
 Oat hay . 84.0 
 
 Timothy hay 86.8 
 
 Oat straw 90.8 
 
 Mangels 9.1 
 
 Grains 
 
 Barley 89.1 
 
 Corn 89.1 
 
 Corn and cob meal .... 84.9 
 
 Oats 89.0 
 
 Rye 88.4 
 
 Wheat 89.5 
 
 By-products 
 
 Dried brewers' grains . . . 92.0 
 
 Cottonseed meal . . . . . 91.8 
 
 Distillers' grains 93.0 
 
 Gluten feed 91.9 
 
 Gluten meal 90.5 
 
 Linseed meal 90.8 
 
 Malt sprouts 89.8 
 
 Dried sugar-beet pulp . . . 93.6 
 
 Wheat bran 85.1 
 
 Wheat middlings .... 84.0 
 
 1.21 
 6.93 
 5.41 
 2.13 
 1.80 
 2.59 
 2.05 
 1.09 
 .14 
 
 8.37 
 6.79 
 4.53 
 8.36 
 8.12 
 8.90 
 
 16.56 
 34.41 
 34.74 
 30.53 
 26.53 
 36.97 
 33.56 
 21.21 
 4.62 
 
 80.75 
 88.84 
 72.05 
 66.27 
 81.72 
 82.63 
 
 19.04 
 35.15 
 21.93 
 19.95 
 33.09 
 27.54 
 12.36 
 6.80 
 10.21 
 12.79 
 
 60.01 
 84.20 
 79.23 
 79.32 
 78.49 
 78.92 
 46.33 
 60.10 
 48.23 
 77.65 
 
340 APPLIED CHEMISTRY 
 
 EXERCISES 
 
 Ex. 234. What is meant by a balanced ration? By the mainte- 
 nance requirement of an animal? Do large animals have a greater 
 maintenance requirement than small ones? Do growing animals need 
 proportionately more protein in their foods ? Why is the ash of the 
 food very important to young animals ? When animals are doing work, 
 do they need more energy producing materials than when not working ? 
 Do they also need more protein ? What kind of foods do fattening ani- 
 mals need those high in protein or in energy ? 
 
 Ex. 236. How much protein and energy are needed to produce a 
 pound of milk? Is the bulk of the food of any moment? What can 
 you say about the effect of palatability on the value of the ration? 
 How important is it to study the individuality of the animal in feeding ? 
 
 Ex. 236. How is an animal's daily ration calculated ? 
 
 Ex. 237. Calculate a ration for a 1000-pound dairy cow that gives 
 30 pounds of milk a day. Use corn fodder and alfalfa hay for roughage 
 and any of the foods in the table on page 339 for concentrates. Cal- 
 culate the protein and the energy in any ration used on your home farm 
 and note whether it agrees with the feeding standards given in this 
 chapter. 
 
 Ex. 238. Calculate the ration for a fattening ox weighing 1000 
 pounds according to the Wolff-Lehman tables on page 337, using corn 
 stover and clover hay for roughage. Which method of calculating is the 
 simpler? For analyses of feeding stuffs see Farmers' Bulletin, No. 22, 
 U. S. Department of Agriculture, or any of the larger texts on feeding 
 animals. 
 
CHAPTER XLI 
 
 HUMAN FOODS 
 
 384. Food Requirements of Human Beings. The prin- 
 ciples of human nutrition are exactly the same as those for 
 domestic animals. Men and women need protein for the re- 
 pair of tissue and for energy to enable the body to do its work, 
 and these two necessities are furnished by the food, just as in 
 the case of the lower animals. The food requirements of 
 human beings are indicated by dietary standards that have 
 been worked out by investigators. The following standards 
 of daily requirements have been prepared by Atwater : 
 
 CHARACTER OP WORK 
 
 PROTEIN 
 
 FAT 
 
 CARBO- 
 HYDRATES 
 
 CALORIES 
 
 Pounds 
 
 Pounds 
 
 Pounds 
 
 Man with little exercise . . 
 
 0.20 
 
 0.20 
 
 0.66 
 
 2450 
 
 Man with light work . . . 
 Man with moderate work 
 
 0.22 
 0.28 
 
 0.22 
 0.28 
 
 0.77 
 0.99 
 
 2800 
 3520 
 
 Man with hard work . . . 
 
 0.39 
 
 0.55 
 
 1.43 
 
 5700 
 
 A woman is supposed to require eight tenths of the protein 
 and energy needed by a man ; and children require an amount 
 about proportional to their size and weight. In general 
 terms it may be stated that according to this standard a 
 man of average size and doing average work requires about 
 one fourth of a pound each of protein and fat, one pound of 
 
 341 
 
342 
 
 APPLIED CHEMISTRY 
 
 carbohydrates, and 3200 calories of energy daily. Some 
 writers think this standard too high and hence likely to 
 result in overfeeding. 
 
 385. Calculating a Balanced Ration. The nutritive value 
 of human foods varies just as it does in the case of the feeds 
 for the farm animals. The method of calculating a ration 
 that conforms to the standard is exactly the same as that 
 used in calculating the ration for cattle or horses (382). 
 The following combination given by Snyder serves as an 
 example of a day's ration which would meet the general 
 standard for a man doing average work. 
 
 FOODS 
 
 AMOUNT OF 
 FOODS 
 PER DAY 
 
 PROTEIN 
 
 FAT 
 
 CARBO- 
 HYDRATES 
 
 CALORIES 
 
 
 Ounces 
 
 Pounds 
 
 Pounds 
 
 Pounds 
 
 
 Ham 
 
 4 
 
 0.04 
 
 009 
 
 
 480 
 
 Eggs (2) . . . . 
 
 
 0.03 
 
 0.02 
 
 
 
 136 
 
 Bread 
 
 8 
 
 005 
 
 001 
 
 028 
 
 650 
 
 Butter 
 
 2 
 
 
 0.11 
 
 
 r 450 
 
 Potatoes .... 
 
 12 
 
 0.02 
 
 
 0.14 
 
 ^285 
 
 Milk 
 
 16 
 
 004 
 
 004 
 
 005 
 
 325 
 
 Suffar 
 
 2 
 
 
 
 12 
 
 200 
 
 Beef stew 
 
 4 
 
 0.04 
 
 0.05 
 
 
 250 
 
 Oatmeal .... 
 
 2 
 
 0.02 
 
 0.01 
 
 0.09 
 
 230 
 
 Corn meal . . . 
 
 4 
 
 0.02 
 
 0.01 
 
 0.18 
 
 420 
 
 Totals . . . 
 
 
 0.26 
 
 0.34 
 
 0.86 
 
 3426 
 
 This ration contains somewhat less carbohydrates and 
 more fat than the standard and furnishes a little less energy, 
 but it is close enough for practical purposes. 
 
 386. Practical Use of Dietary Standards. It is neither 
 practicable nor necessary to undertake to prepare the meals 
 each day in exact conformity to a dietary standard. An 
 
HUMAN FOODS 343 
 
 occasional study of the foods served in the family to ascertain 
 how closely they conform to the standard is desirable, be- 
 cause such a study gives a basis for modifying the diet, if 
 necessary to make it supply the proper amount of protein 
 and energy. It is practicable, after a study of the composi- 
 tion of the different foods, to make combinations that will 
 provide in a general way the right proportions of protein and 
 energy, and to avoid combinations that are too high in 
 protein or that carry an excess of energy. In other words, 
 it is practicable to avoid a combination that includes several 
 foods high in protein, or one made up of several foods high in 
 energy value and low in protein. In combining foods to 
 form balanced rations it is well to remember that lean meats, 
 fish, dried beans and peas, oatmeal, and nuts are substances 
 high in protein. Fat pork products and other fat meats, 
 cheese, butter, oils, and lard supply fats in large proportions. 
 Potatoes, rice, corn meal, cereals, sugars, cornstarch, and 
 tapioca are high in carbohydrates. Wheat flour and the 
 other foods prepared from wheat are moderately high in both 
 protein and carbohydrates and low in fat. 
 
 The more recent studies of foods indicate that the subject 
 is much more complicated than was formerly supposed. It 
 is not sufficient merely to balance the food so as to provide 
 the required amount of protein, fat, carbohydrates, and 
 energy. The proteins differ among themselves in character ; 
 hence, the ration should contain a variety of proteins. 
 
 It has been discovered also that most common foods con- 
 tain very small quantities of a water-soluble substance 
 which is essential for the maintenance of normal body con- 
 ditions. This substance has not been isolated and its nature 
 is not understood. It is lacking in certain prepared foodstuffs 
 such as polished rice, commercial starch, pure sugar, and fats. 
 
344 APPLIED CHEMISTRY 
 
 Another of the important discoveries of modern chemistry is 
 the fact that there is a fat-soluble substance, called vitamine, 
 which seems to be absolutely necessary to growth (Fig. 159). 
 The nature of this substance is unknown, but it is known 
 that it is not so widely distributed as is the water-soluble 
 substance mentioned above. It is found in milk, especially 
 in the milk fat, in egg yolk, in some meats, and in the green 
 
 A B 
 
 FIG. 159. (A) Rat without and (5) rat with fat-soluble vitamines. 
 
 leaves of plants. It is not found in seeds except in the germ, 
 nor in oils such as olive and cottonseed oils. A lack of this 
 fat-soluble substance in the food prevents the growth of 
 young animals even when abundantly supplied with food. 
 The fact that it is present in milk is one of the reasons why 
 milk is so valuable a part of the diet of growing children. 
 
 There is a difference in the character of the mineral ele- 
 ments, or ash constituents, of foods. In some foods the acid- 
 forming elements are in excess, while in others the basic or 
 alkaline elements predominate. Recent investigations in- 
 dicate that it is desirable that the diet should contain a 
 slight excess of basic elements. The foods that furnish 
 alkaline mineral substances in relatively large proportions 
 are tubers, leafy vegetables, fruits, and milk. The cereals, 
 
HUMAN FOODS 345 
 
 meat, fish, and eggs contain the acid mineral elements in 
 excess. It would seem, therefore, that such a combination as 
 bread and milk is a logical one, since in this combination the 
 alkalinity of the ash materials of the milk overcomes the 
 acidity of the cereal ash. 
 
 Palatability is even more important in human foods than 
 in animal feeding stuffs. Food should be so prepared as to 
 appeal to the individual by its appearance and flavor, since 
 pleasure in eating undoubtedly plays a part in insuring a 
 regular and normal sequence of digestive process. 
 
 387. Digestibility of Foods. The term digestibility has 
 been used in two different ways by physiologists and chem- 
 ists : (1) to designate the completeness of the process of the 
 digestion of the food ; and (2) to designate the fact that the 
 food is digested without causing distress or discomfort during 
 the process. Some confusion has arisen from this double 
 meaning. Cheese, for example, is very completely digested ; 
 but since it is commonly considered to be hard to digest, 
 that is, to cause distress after eating, it is often said to be indi- 
 gestible. Bread, which is digestible according to the second 
 use of the word, is not so completely digested as cheese. 
 
 Some of the factors affecting the digestibility of foods are 
 the following : (1) Individuality of the person. Some people 
 can easily digest foods that cause great discomfort to others. 
 (2) Mechanical condition of food. When the food is in good 
 mechanical condition it is more easily acted upon by the 
 digestive juices. (3) The combination of foods. The way in 
 which* foods are combined is of importance, as some foods 
 seem to aid in the digestion of others. (4) Method of prepara- 
 tion. The method of preparing or cooking foods exerts an 
 influence on their digestibility. Cooking changes both the 
 physical and the chemical condition of the food, and influences 
 
346 APPLIED CHEMISTRY 
 
 the ease of digestion more than the completeness of the 
 process. The chief advantages of cooking are probably 
 the development of a more pleasing flavor, and, more im- 
 portant still, the complete sterilization of food that may 
 contain injurious bacteria or other organisms. 
 
 388. Food Adjuncts. Spices, such as allspice, nutmeg, 
 cinnamon, and ginger, are not foods, but may or may not be 
 useful adjuncts to the diet. They stimulate the appetite 
 and promote secretion of the gastric juice, which may be 
 beneficial or may induce overeating. Such substances are 
 called condiments. Vinegar is a condiment and is used 
 largely because of the pleasant acidity of its acetic acid. 
 
 Coffee or tea have little or no nutritive value but are used 
 because of the stimulating effect of the alkaloid caffein 
 which they contain. Cocoa contains a similar alkaloid but 
 has some nutritive value as well, because of its fat content. 
 
 389. Fresh Fruits. Considered strictly from the chemical 
 standpoint, fruits seem to have little food value, as they are 
 low in both protein and energy. Fresh fruits contain from 
 85 to 95 per cent water, a fraction of 1 per cent of fat and 
 protein, and only 5 to 10 per cent of carbohydrates. They 
 contain, however, acids, organic salts, and other substances 
 which are believed to have a beneficial effect on the system, 
 and they doubtless often stimulate the appetite for other 
 food. Fruits also add to the attractiveness of the diet, and 
 the appearance of the food is a matter of considerable im- 
 portance. The ash of fruits is rich in potassium, calcium, 
 and iron salts, all of which are valuable to the body. -Dried 
 fruits, such as dates, raisins, and figs, are foods in the more 
 restricted sense, as they furnish a large amount of digestible 
 nutrients. Dates, especially, form a large part of the diet 
 of certain Oriental people. 
 
HUMAN FOODS 347 
 
 390. Dietary Studies. A dietary study takes into con- 
 sideration the cost and amount of nutrients consumed by 
 individuals or families. It is an investigation in which men 
 and women and human foods are used instead of farm an- 
 imals and animal feeds. In a dietary study, the amounts of 
 nutrients in the edible portion of the foods are determined by 
 chemical analysis or calculated from the tables of composition. 
 These studies take into consideration the cost of the material 
 as well as the amounts of protein and energy used by each 
 person or group. Such studies show that lack of knowledge 
 in regard to the values of foods has frequently resulted in 
 whole families being underfed, not from necessity, but from 
 lack of judgment in the selection of foods. It too often 
 happens that choice of foods is made wholly on the basis of 
 palatability, instead of on the cost of the nutrients and the 
 kind of work to be performed. Dietary studies show that 
 for long periods the best results are obtained when the foods 
 are combined in such a way as to furnish the different 
 nutrients in approximately the amounts given in the dietary 
 standards. By studying the diet it is often possible to re- 
 duce the cost of the food without impairing its nutritive 
 value if indeed the nutritive value is not actually increased. 
 
 391. Food Fads. Much of the matter that has been 
 written on the subject of foods is wholly without scientific 
 basis, even when it pretends to be scientifically presented. 
 Vegetarianism, or the exclusive use of vegetable foods, is 
 advocated by some people ; but there is no scientific evidence 
 that mankind is benefited by an exclusively vegetable diet. 
 The long-continued experience of the human family on a 
 mixed diet of cooked meats and vegetables is evidence that 
 such a diet is healthful, and there are many indications that 
 the best diet is one that contains a reasonable amount of 
 
348 APPLIED CHEMISTRY 
 
 animal protein. Many so-called vegetarians obtain this 
 animal protein through the use of milk and eggs; but of 
 course in such conditions the diet is no longer strictly vege- 
 tarian. It is probably true that American families use more 
 animal protein than is necessary, a practice which, while it may 
 not be injurious, results in an unnecessarily expensive diet. 
 
 The exclusive use of raw foods is another food fad that has 
 no scientific basis, and it is not surprising that the cult has a 
 comparatively small following. Unfortunately a large part 
 of the literature on foods has been written by dyspeptics or 
 by people who have prepared foods of some kind to sell. 
 
 392. What to Eat. Probably the only advice that can 
 safely be given is about as follows : (1) make the diet agree 
 approximately with the ratios between protein, fat, and 
 carbohydrates as given in the dietary standard ; (2) provide 
 a part of the protein from animal sources; (3) consume 
 moderate amounts of such a balanced food; (4) avoid all 
 foods that personal experience has shown to produce dis- 
 comfort; (5) have as much variety as possible in the diet, 
 including the use of green and succulent vegetables ; (6) com- 
 bine coarse or laxative foods with those that are more 
 completely digested; (7) use fresh fruits abundantly, if 
 possible; (8) use condiments or the stimulating beverages 
 such as tea and coffee only moderately ; (9) remember that 
 the highest priced foods are often the least nutritious, and 
 that there is no close relation between cost and food value ; 
 (10) use only foods that have been carefully protected from 
 bacterial contamination. 
 
 Millions of dollars have been spent by manufacturers in the 
 last few years in advertising the many brands of breakfast 
 foods on the market. In general, it may be said that these 
 breakfast cereals have no greater nutritive value than the 
 
HUMAN FOODS 349 
 
 grains from which they were prepared. Breakfast cereals 
 made from corn are equal to the same weight of corn meal, 
 for example, and those made from wheat are no more valu- 
 able than the wheat itself. The price paid for each pound 
 of actual nutrients in the breakfast foods is several times 
 the cost of the same nutrients in corn meal or wheat flour. 
 
 EXERCISES 
 
 Ex. 239. What is meant by a dietary standard? What is the 
 approximate dietary requirement of a man doing average work? 
 How should you calculate a balanced ration for a man ? What practical 
 daily use can be made of dietary standards? Name some foods high 
 in protein ; some high in fats ; some high in carbohydrates. 
 
 Ex. 240. Make a list of the foods used on your home table for 
 each meal for a day. Does the combination appear to be too high in 
 protein ? In energy materials ? Would a little change improve it ? For 
 the composition of the common foods, see Farmers' Bulletin 142, or 
 Office of Experiment Station Bulletin 28, U. S. Department of Agricul- 
 ture. 
 
 Ex. 241. In what two ways is the term digestibility used ? What 
 are some of the factors which affect digestibility of foods ? Tell what 
 you can about the food value of fruits. 
 
 Ex. 242. Of what value is a dietary study ? How is it conducted ? 
 What do these studies sometimes show? Study some of the bulletins 
 of the United States Department of Agriculture on dietary studies. 
 
 Ex. 243. State ten practical points to be observed in deciding 
 what to eat. What can you say about food fads ? What can you say 
 about the value of the prepared breakfast foods ? 
 
CHAPTER XLII 
 MILK AND ITS PRODUCTS 
 
 393. Secretion of Milk. Milk is a fluid secreted by 
 the mammary glands of all animals that suckle their young. 
 It contains in a palatable and easily digested form all the 
 nutrients necessary for the nourishment of the young 
 animal. Market milk in this country is almost entirely 
 cow's milk, but the goat and the water buffalo are important 
 sources of milk supply in some other countries. In the wild 
 state the cow produced only sufficient milk to nourish the 
 calf until it could subsist upon other food, but under domesti- 
 cation the secretion of milk by the cow has been greatly 
 increased by careful selection and liberal feeding. 
 
 394. Composition of Milk. The essential constituents of 
 milk are water, fat, protein, sugar, and ash or mineral salts. 
 The average composition of cow's milk is shown in the follow- 
 ing table : 
 
 AVERAGE COMPOSITION OF Cow's MILK IN PER CENTS 
 
 f Water 87.2 
 Cow's milk 100 1 
 
 Solids 
 
 12.8 
 
 Fat. . 
 Protein 
 Sugar . 
 Ash. 
 
 . 3.75 ( . 
 32 Casein . 
 
 _' [Albumin 
 
 o O.lO 
 
 0.7 
 
 . 2.5 
 . 0.7 
 
 There is considerable variation in the composition of the 
 milk from different cows. The most variable constituent of 
 the milk is its fat content. Some cows produce milk with as 
 
 850 
 
MILK AND ITS PRODUCTS 351 
 
 little as 2 per cent of fat, while other cows have been known 
 to produce milk containing as much as 8 or 9 per cent of fat. 
 The other constituents of the milk are fairly constant in 
 amount even in milks that vary greatly in fat content. 
 The quantity and the quality of the milk produced by a cow 
 depend upon a number of factors. Certain breeds, such as 
 the Jersey and Guernsey, as a rule produce a relatively small 
 quantity of milk, which is high in fat ; while the Holstein and 
 Ayrshire breeds give larger quantities of milk, which is low in 
 the percentage of fat. Individual animals within any of 
 these breeds differ in the quantity and the quality of the milk 
 they produce. The kind and the amount of feeds the animal 
 receives have an influence on the amount of milk produced, 
 but apparently have no effect upon the quality of the milk. 
 The richness of a cow's milk seems to be natural to her and is 
 not affected by the feeds she eats, although the quantity of 
 milk she produces may be so affected. A cow usually pro- 
 duces the most milk per day within a month after the calf is 
 born, and the amount gradually decreases until the secretion 
 ceases as the cow goes dry. As the amount of milk decreases, 
 the percentage of fat is slightly increased. The first milk 
 drawn from the udder at any milking is much poorer in 
 quality than the last. The first often tests as low as 1 per 
 cent of fat and the last as high as 8 or 9 per cent fat. 
 
 395. Fat of Milk. This fat occurs in the form of small 
 globules (Fig. 160) which can be seen only under the mi- 
 croscope. The globules average about one six-thousandth 
 of an inch in diameter. The size of the globule averages 
 larger in the milk of Jerseys and Guernseys than in that of 
 Ayrshires or Holsteins. Any sample of milk, however, con- 
 tains globules that vary greatly in size. The fat globules 
 are held in suspension by the other solids of the milk in the 
 
352 
 
 APPLIED CHEMISTRY 
 
 form of an emulsion. The fat of milk is commonly called 
 butter fat. It differs chemically from other fats in that it 
 contains about 5 per cent of butyrin, the glycerin salt of 
 butyric acid, H- C 4 H 7 O 2 (299). The fat has a much higher 
 
 FlG. 160. Appearance of milk under the microscope, showing groups of fat 
 globules. In the circle the fat globules are more highly magnified. 
 
 commercial value than any other part of the milk, and con- 
 sequently the price of milk is usually based on its fat content. 
 396. Casein. The principal protein of milk is casein and it 
 gives skim milk its bluish-white color. When acid is added to 
 milk the casein separates in the form of a curd. The natural 
 curdling of milk is caused by the lactic acid formed in the 
 milk when it sours (290). The casein can also be separated 
 from the milk by means of rennet, which is a preparation 
 made from the stomachs of very young calves and contains 
 the enzyme rennin (358). When this material is added to 
 milk, the casein separates in the form of a sweet curd, which 
 firmly incloses nearly all the fat that the milk contains. 
 This curd forms the starting point in the manufacture of 
 cheese. Junket tablets contain dried rennet. In making 
 junket just enough rennet is used to coagulate the casein 
 
MILK AND ITS PRODUCTS 353 
 
 and change the milk into a jelly like mass without causing 
 the casein to separate. 
 
 397. Albumin of Milk. This is much like the white of egg. 
 Like all albumins it is soluble in water, and as it is not pre- 
 cipitated by acid it remains in solution when the casein is 
 separated either by acid or rennet. Boiling the clear liquid, 
 or whey, which remains after the casein is removed coagulates 
 the albumin and causes it to separate in white flakes. The 
 tough scum which forms on the surface of milk when it is 
 boiled is composed largely of coagulated albumin. 
 
 398. Sugar of Milk. Lactose or milk sugar has the 
 formula C^I^On (310). This sugar occurs only in milk. 
 In commerce it is found as a fine white powder with a mild, 
 sweet taste. It is about one sixth as sweet as cane sugar. 
 It is readily acted upon by the bacteria in the milk and is 
 changed into lactic acid : 
 
 Ci2H 22 On + H 2 O > 4 H- C 3 H 5 O 3 
 
 lactic acid. 
 
 It is this acid that makes milk sour and causes the casein to 
 curdle or separate. When about 0.4 per cent of lactic acid is 
 present the milk acquires a sour taste, and when the amount 
 reaches 0.6 to 0.7 per cent it begins to curdle. Ordinarily 
 the acid will not develop beyond 0.9 per cent. 
 
 399. Ash of Milk. The mineral matter left after burning 
 off the organic matter is the ash of milk. It contains all 
 the compounds necessary to build the bony structure of the 
 growing animal. The most important elements in the ash are 
 calcium, phosphorus, iron, potassium, magnesium, and sul- 
 phur. The mineral matter is probably largely combined 
 with the casein and albumin in the milk. 
 
 400. Milk and Bacteria. Since milk is a complete food 
 and is in a liquid form, it is an ideal medium for the growth 
 
 EV. CHEM. 23 
 
354 
 
 APPLIED CHEMISTRY 
 
 FIG. 161. Showing the rapid development 
 of bacteria in milk, a, a single bacterium ; 
 6, increase in 24 hours when properly 
 cooled ; c, increase when not cooled. 
 
 of bacteria, molds, and other organisms. Bacteria, es- 
 pecially those which cause the souring of milk, are so widely 
 distributed that it is difficult to keep them out of milk, and 
 
 for this reason the pro- 
 duction of milk which is 
 pure enough for human 
 consumption requires 
 more care than any other 
 work on the farm . Care- 
 ful attention should be 
 given to the surround- 
 ings, to the cleanliness 
 of the cow, to the actual 
 process of milking, and to the utensils used, so as to prevent 
 as far as possible the introduction of bacteria into the milk. 
 Disease-producing germs should be especially guarded 
 against, as many of them grow rapidly in milk. Diseases 
 have often been spread 
 in this way. 
 
 It is practically im- 
 possible to keep all acid- 
 forming bacteria out of 
 the milk ; but if the milk 
 is cooled immediately 
 upon being taken from 
 the cow, their growth 
 will be retarded and 
 the milk will keep sweet 
 longer than when this precaution is not taken (Fig. 161). 
 
 Milk that has been boiled to kill the bacteria is said to be 
 sterilized. Such milk if carefully stored will keep a com- 
 paratively long time but has a cooked taste. Sometimes the 
 
 FIG. 162. Pasteurizing apparatus. 
 
MILK AND ITS PRODUCTS 355 
 
 milk is heated to 145 F. for from 20 to 40 minutes and is 
 then rapidly cooled, when it is said to be pasteurized (Fig. 
 162). Such milk does not have the taste of boiled milk 
 and if stored in a cool place will keep sweet for a few days. 
 This process kills most of the active bacteria and thus delays 
 the souring. 
 
 Antiseptic materials, such as boric acid, salicylic acid, and 
 formalin are sometimes added to milk to preserve it ; but this 
 practice is illegal. Any antiseptic that will prevent the growth 
 of bacteria is unfit for use in any food intended for human 
 consumption. Such materials are especially harmful in 
 milk to be used for infant feeding. 
 
 401. Cream and Skim Milk. The fat of milk is lighter 
 than the liquid portion of the milk. The specific gravity of 
 the fat is about 0.9, while the rest of the milk has a specific 
 gravity of about 1.036. The fat globules being lighter tend 
 to rise to the surface, where they form a layer known as 
 cream. The larger the globule the more rapidly it rises ; so 
 the milk of the Jersey and Guernsey breeds creams more 
 easily than that from the breeds with smaller fat globules, 
 such as the Ayrshire and Holstein. The smaller the fat 
 globule, the larger is its surface in proportion to its volume, 
 and, consequently, the greater the resistance to its rise. 
 Cream may contain from 12 to 50 per cent of fat. That part 
 of the milk that remains when the cream ;s removed is known 
 as skim milk. It differs from whole milk in containing only 
 0.1 to 0.4 per cent of fat. When milk is allowed to stand in 
 deep or shallow pans until the cream collects on the surface 
 (24 to 36 hours), the cream is said to have been separated by 
 gravity. Milk held in deep cans which are allowed to stand 
 in cold water creams more completely than when set in 
 shallow pans. 
 
356 APPLIED CHEMISTRY 
 
 402. Cream Separators. At the present time most of 
 the cream is produced by skimming the milk by the cen- 
 trifugal cream separator. In this machine centrifugal force 
 generated by a rapidly revolving bowl takes the place of 
 gravity and acts with a much greater force. As the milk 
 flows into the revolving bowl in a continuous stream, it is 
 acted upon by centrifugal force and flies to the outer wall 
 of the bowl. The skim milk being heavier than the cream 
 is forced out and against the side of the bowl, forcing 
 the cream toward the center. By providing suitable out- 
 lets the skim milk can be directed into one channel and 
 the cream into another. The skimming is more complete 
 if the milk is first warmed to about 85 F. If separated 
 as soon as it is milked the temperature is right without 
 artificial heating. 
 
 The skimming by the separator is much more complete 
 than by any of the gravity methods. A properly working 
 separator will leave not to exceed 0.1 per cent of fat in the 
 skim milk, while gravity creaming may leave from 0.4 to 0.8 
 per cent. The average per cent composition of separator 
 skim milk is about as follows : 
 
 Water 90.54 
 
 Fat 0.10 
 
 Sugar 4.94 
 
 Proteins 3.53 
 
 Ash 0.89 
 
 Skim milk contains all the materials found in whole 
 milk with the exception of fat. It has a high food value, 
 and its use as a human food deserves more consideration than 
 it has received in this country. Its value as a food for farm 
 animals has long been recognized. 
 
 The use of the separator has the added advantage that the 
 
MILK AND ITS PRODUCTS 
 
 357 
 
 skimming is done while the milk is fresh and sweet and that 
 therefore both the cream and the milk are in the best con- 
 dition for use as foods. Separators vary in capacity from the 
 small hand machines that will handle 150 pounds of milk an 
 hour to power machines with a capacity of 4000 pounds or 
 more an hour. 
 
 403. Butter. When cream is agitated for some time at 
 the right temperature, the fat globules unite into larger and 
 larger aggregates, 
 and the fat finally 
 separates in irregular 
 masses of butter. 
 The process of agi- 
 tating the cream is 
 known as churning. 
 Many different kinds 
 of churns are in use, 
 the types varying 
 from the old-fash- 
 ioned dasher churn to 
 the more modern 
 barrel-shaped churns. 
 
 The proper tem- 
 perature for churning 
 ranges from 50 to 58 
 
 degrees F., varying with different samples of cream. Churn- 
 ing should cease when the granules of butter are the size of 
 wheat grains. The butter is then washed with cold water to 
 remove the buttermilk, and is finally worked to remove 
 excess of water. During the working salt is added gradually, 
 although a few American and many European markets demand 
 unsalted butter. American butter contains on the average 
 
 FIG. 163. Churning butter in Palestine. 
 
358 APPLIED CHEMISTRY 
 
 from 83 to 85 per cent of fat, 12 to 15 per cent of water, and 
 from 2 to 4 per cent of salt. 
 
 404. Ripening of Cream. Butter made from perfectly 
 sweet cream is considered by many to have an insipid taste. 
 In order to develop the flavor preferred by the general market 
 and to facilitate the churning, the cream is allowed to become 
 slightly acid before it is churned. This is known as the 
 ripening of the cream. The cream is properly ripened when 
 it contains about one half per cent of lactic acid. Since 
 many of the bacteria that find their way into milk produce 
 undesirable flavors in the cream, in order to insure the proper 
 fermentation it is customary to add a pure culture of the 
 desired bacteria, known as a starter. In many creameries 
 the cream is first pasteurized to kill most of the native bac- 
 teria, and the starter is then added. This method makes it 
 much easier to control the flavor of the butter. 
 
 405. Buttermilk is the liquid remaining in the churn after 
 the separation of the butter from the cream. It contains 
 about 90 per cent water, 3.5 percent proteins, 0.5 per cent fat, 
 4.0 per cent sugar, and 0.5 per cent lactic acid. The finely 
 divided condition of its proteins makes it readily digested. 
 The mildly acid taste of buttermilk is pleasing to some 
 people and very distasteful to others. Buttermilk is growing 
 in popularity as a food and a beverage to such an extent 
 that many factories are now producing large quantities of 
 artificial buttermilk. This is made by adding a starter 
 to skim milk and allowing the proper degree of acidity to 
 develop ; when this acidity is properly developed, the milk 
 is churned to break the curd into fine particles such as 
 exist in natural buttermilk. If, as is sometimes done, a 
 little cream is added, the product is known as creamed 
 buttermilk. 
 
MILK AND ITS PRODUCTS 359 
 
 406. Condensed Milk and Milk Powders. Condensed 
 milk is prepared by evaporating the water from milk in a 
 vacuum pan until the milk is reduced to about one third or 
 one fourth of the original volume. The evaporation is 
 carried on under reduced pressure so that the milk need not 
 be heated to a sufficiently high temperature to impart to it a 
 cooked flavor. The condensed milk is then sealed in cans 
 and sterilized by exposing the can to superheated steam. In 
 some brands of condensed milk the sterilization is omitted, 
 and about 40 per cent of cane sugar is added to prevent 
 fermentation. The unsweetened condensed milk is quite 
 commonly called evaporated milk or evaporated cream to dis- 
 tinguish it from the sweetened condensed milk. 
 
 Milk powders are prepared by evaporating the milk to 
 complete dryness. A good sample of milk powder is as fine 
 as flour, and when stirred up with water makes a mixture 
 having the properties of milk. Most of the milk powders 
 are made from skimmed or partially skimmed milk. It 
 is said that milk powder prepared from whole milk will 
 not keep on account of the large amount of fat that it 
 contains. 
 
 407. Cheese. A great number of varieties of cheese are 
 found in the market, most of which are prepared by the 
 action of rennin (358) on milk. The variety most largely 
 used in this country belongs to the type- known as Cheddar 
 cheese and is commonly known as American cheese. 
 
 In making American Cheddar cheese, after the milk has 
 been allowed to develop about 0.25 per cent of lactic acid a 
 small quantity of rennet extract is added, and the milk is kept 
 at a temperature of about 85 degrees F. In about thirty 
 minutes the milk sets into a firm, jellylike curd. This curd 
 is then cut into small cubes with specially devised knives, and 
 
360 APPLIED CHEMISTRY 
 
 the temperature of the vat is raised to 100 F. At this 
 temperature the curd shrinks quite rapidly and more acid 
 develops and is absorbed by the curd. After one or two 
 hours the whey is drawn from the vat and the curd mats into 
 a solid mass. After some time it is passed through a mill to 
 shred it and is then salted and pressed into molds. The 
 cheese is then placed in the curing room for a period in order 
 to ripen and develop flavor. 
 
 When the cheese is first made, it is tasteless and very 
 tough and rubbery, and is not readily digested. After a 
 period of ripening the cheese becomes soft and plastic and 
 develops a flavor which increases in intensity with the age of 
 the cheese. Practically none of the nitrogenous compounds 
 of the new cheese are soluble in water, while in old cheese over 
 half of these compounds are soluble. In other words the 
 cheese has been partially digested during the ripening process. 
 A good American cheese contains about 26 per cent of pro- 
 teins and 33 per cent of fat. 
 
 Very slight differences in the amount of rennet added, in 
 the temperature at which the milk is set, in the amount of 
 acid developed, or in the temperature and moisture of the 
 curing room produce marked differences in the appearance 
 and flavor of the cheese ; consequently there are almost end- 
 less varieties of cheeses on the market, varying from the very 
 soft Brie and Camembert to the firm Cheddar and Swiss 
 cheeses. In some varieties, such as Roquefort, molds are 
 added to produce a special flavor. Goat's milk and sheep's 
 milk are also sometimes used in cheese making. 
 
 The whey left in cheese making contains most of the albu- 
 min and the sugar originally present in the milk. The 
 albumin is sometimes coagulated by heat and used to make 
 an albumin cheese. In some factories the sugar is recovered 
 
MILK AND ITS PRODUCTS 361 
 
 by evaporation and is sold under the name of lactose, or 
 milk sugar, for use in medicine. 
 
 Cottage cheese, or pot cheese, is made from the curd of 
 sour milk without the use of rennet. The curd is firmed by 
 heat and the whey drained off through a cloth strainer. Salt 
 is added and the product is improved by the addition of 
 cream, and sometimes by the use of nutmeg, caraway, or 
 other spices. A similar cheese is made from buttermilk. 
 
 408. Other Milk Products. In some creameries the skim 
 milk is utilized for the production of dried casein. Sul- 
 phuric acid is used to curdle the milk and the casein is pressed 
 and then dried. The casein thus prepared is used as a sizing 
 for paper and in the manufacture of certain cements. It is 
 used also in massage creams and in some cosmetics. Casein 
 so treated as to make it very hard is used in making billiard 
 balls and knife handles under the name of artificial ivory. 
 
 Koumiss is a beverage made from milk. Yeast and sugar 
 are added to the milk, and the ensuing fermentation results 
 in the production of a small percentage of alcohol. Koumiss 
 was originally made in Russia from mare's milk. 
 
 Bulgaris milk is usually made from skim milk by the action 
 of a species of bacteria, known as Bacillus bulgaricus. 
 These bacteria cause the milk to become sour without the 
 separation of the casein. Bulgaris milk tastes very much like 
 buttermilk, but often has a higher acidity. 
 
 EXERCISES 
 
 Ex. 244. What are the constituents of milk? What constituent 
 is most variable in the amount present? How does the breed affect 
 the amount of fat in the milk? Does the feed change the percentage 
 of fat in a cow's milk ? Can the quantity of milk be changed by vary- 
 ing the feed? Which contains the most fat that first drawn from the 
 udder or the strippings ? 
 
362 APPLIED CHEMISTRY 
 
 Ex. 245. Examine a drop of milk under the microscope. In what 
 form is the fat present in the milk ? How large are these globules ? 
 What eff ect does the breed of cow have on the size of the globule ? What 
 is the characteristic compound of butter fat? Why does the per- 
 centage of fat usually determine the value of the milk ? 
 
 Ex. 246. To some skim milk add a little vinegar or acetic acid. 
 What is the curd which forms ? To another portion of the milk add a 
 little rennet extract or a little pepsin. What happens? How much 
 casein does ordinary milk contain ? 
 
 Ex. 247. Pour off the clear liquid from the milk to which the vine- 
 gar was added in the last exercise and heat nearly to boiling. Does 
 albumin separate ? How does albumin compare with the white of egg ? 
 
 Ex. 248. (Teacher) To a quart of skim milk add just enough acid 
 to coagulate the casein. Heat the whey to coagulate the albumin. 
 Skim off the albumin and evaporate the liquid to dryness to obtain 
 milk sugar. What are the properties of milk sugar ? What change 
 takes place when the milk sours ? How much lactic acid must develop 
 in the milk before it curdles ? 
 
 Ex. 249. What mineral elements are found in milk ? Of what use 
 are they to the young animal ? To obtain the ash from milk place the 
 milk in an evaporating dish, add sufficient nitric acid to coagulate the 
 casein, evaporate to dryness, and burn off the organic matter. 
 
 Ex. 260. Why do bacteria grow so readily in milk? How do the 
 bacteria get into the milk ? What precautions are necessary to produce 
 clean milk ? How does immediate cooling of the milk affect its keeping 
 quality? What is meant by sterilized milk? By pasteurized milk? 
 Why do they keep longer than ordinary milk ? Why should all antisep- 
 tic materials be avoided in milk ? Test a sample of milk for formalde- 
 hyde as follows : place a little milk in a test tube ; incline the tube and 
 pour a little sulphuric acid such as is used in the Babcock test down the 
 side of the tube so that it will underlie the milk. If formaldehyde is 
 present, a purple ring will appear at the junction of the milk and acid. 
 
 Ex. 251. When milk stands why does the cream form at the top? 
 How much fat does cream contain ? What is skim milk ? What is 
 meant by gravity creaming ? Explain the principle of the cream sepa- 
 rator. Does the separator remove more fat from the milk than the 
 gravity process of creaming ? How much fat is left in separator skim 
 milk ? What can you say of the food value of skim milk ? 
 
MILK AND ITS PRODUCTS 363 
 
 Ex. 252. How is butter made ? How much fat does butter contain ? 
 What is meant by the ripening of cream ? Why is cream ripened ? 
 What is buttermilk ? To what is its acid taste due ? How is artificial 
 buttermilk made ? 
 
 Ex. 253. How is condensed milk made ? Examine a can of con- 
 densed or evaporated milk. Dilute with twice its bulk of water. 
 Does it taste like ordinary milk? Why is sugar sometimes added to 
 milk ? How are milk powders prepared ? Why are they usually made 
 from partly skimmed milk ? If possible obtain a sample for inspection. 
 
 Ex. 254. Outline the method of making American Cheddar cheese. 
 Rub a piece of well-ripened Cheddar cheese as large as a walnut with a 
 test tube full of water and filter. To the filtrate add a little tannic acid 
 solution. Are there any soluble proteins in the cheese ? How were they 
 formed ? 
 
 Ex. 255. How many different kinds of cheese are on the local 
 market ? Why can so many kinds of cheese be made from one kind of 
 milk ? How is cottage cheese made ? Is any rennet used in this case ? 
 What other uses are made of casein ? What is koumiss ? Bulgaris milk ? 
 
CHAPTER XLIII 
 TESTING MILK 
 
 409. Need of a Test. It has been stated that the fat is by 
 far the most valuable constituent of the milk. Butter fat, as 
 it is more commonly termed, often sells for over 30 cents a 
 pound while the rest of the milk may be purchased for a 
 fraction of a cent a pound. Since milk varies in fat content 
 from as low as 2 per cent to as high as 8 per cent, it is unfair 
 to pay the same price per hundredweight for all kinds of 
 milk. The creameries and factories now almost universally 
 pay for milk on the basis of its fat content, and consequently 
 a quick, easy, and accurate method of determining the fat 
 in milk is very important. Such a test is also of great value 
 to the farmer in enabling him to determine which cows in his 
 herd are being kept at a profit to him. A test recently made 
 of a dairy herd showed that one cow was yielding a profit of 
 over $80.00 a year, while another was being kept at a loss of 
 $15.00. By testing all the cows and replacing those found 
 to be unprofitable with cows showing a better test the profits 
 of a dairy farm may be increased materially. 
 
 410. The Babcock Test. The most practical method for 
 testing milk for fat is the one invented by Dr. Stephen 
 Moulton Babcock in 1890 and known as the Babcock test. 
 This test has the advantage of being simple and easily manipu- 
 lated, and long use has demonstrated its great accuracy. 
 The principle of the test is the separation of the fat by 
 centrifugal force in such a way that it can be measured. 
 
 364 
 
TESTING MILK 
 
 365 
 
 "5. 
 
 I 
 s 
 
 _ 
 
 1 
 
 <D 
 
 x- 
 ,0 
 
 0) 
 
 I 
 
 Ou 
 
 175 
 C.C. 
 
 Eighteen grams of milk are treated with sulphuric acid, which 
 dissolves the casein -of the milk and thus facilitates the 
 separation of the fat. The mixture is then whirled in a 
 centrifugal machine, and the fat col- 
 lects on the surface of the liquid. 
 To make the test the apparatus 
 shown in Figs. 164 and 165 is 
 necessary. 
 
 The test bottle is so made that the 
 graduations on the neck give the per- 
 centage of fat when the sample of 
 milk weighs 18 grams. The small 
 divisions represent 0.2 per cent. The 
 pipette is graduated at 17.6 cubic 
 centimeters, because experience has 
 shown that when filled to the mark 
 the pipette will deliver just 18 grams 
 of average milk, and it is much easier 
 to measure the milk than to weigh it. 
 
 411. Sampling the Milk. Milk 
 creams so readily that the greatest 
 care is necessary to get a fair sample 
 of the lot to be tested. The entire 
 amount should be thoroughly mixed 
 by pouring several times slowly from 
 one vessel to another, or by stirring J 
 
 the milk and at the same time taking 
 care that no air is introduced into it. 
 Many errors are made by not secur- 
 ing a correct average sample. When 
 the milk is thoroughly mixed, the 
 small end of the pipette should be FIG. 164. 
 
 \ 
 
366 
 
 APPLIED CHEMISTRY 
 
 placed in it and the tester should suck on the upper end until 
 the milk stands in the tube about an inch above the mark. 
 Then he should quickly slip a finger over the upper end of the 
 pipette, easing the finger slightly until the level of the milk is 
 exactly at the mark. Next he should place the lower end of 
 the pipette in the neck of the bottle (Fig. 166), which is 
 
 held in an inclined posi- 
 tion, and allow the milk 
 to run into the bottle. 
 Finally, when the pipette 
 has completely drained, he 
 should blow out the last 
 drop of milk. 
 
 412. Adding the Acid. 
 The acid used should be 
 what is known as commer- 
 cial sulphuric acid and 
 should have a specific 
 gravity of about 1.81 to 
 1.83. The pure acid used 
 in the chemical laboratory is too strong and if used will char 
 the fat. The acid measure should be filled to the mark 
 (17.5 cc.) and the acid should be poured carefully into the 
 test bottle, which is held in an inclined position. If this is 
 done properly, the acid runs down the side of the bottle and 
 stands in a distinct layer beneath the milk. When all the 
 bottles are in readiness, the milk and the acid are mixed by 
 gently rotating the bottle until the curd is all dissolved and 
 the liquid is uniform in color. 
 
 413. Whirling the Bottles. When the milk and acid are 
 thoroughly mixed the bottles are placed in the centrifuge (Fig. 
 165) and whirled for five minutes. Directions are furnished 
 
 FlG. 165. Centrifugal machine. 
 
TESTING MILK 
 
 367 
 
 with most machines which indicate the number of turns of the 
 handle a minute to produce the proper speed for the bottles. 
 With a wheel 20 inches in diameter the correct speed is 
 900 revolutions per minute. If 
 the diameter is greater or less 
 than 20 inches, the speed must 
 be varied so as to produce centrif- 
 ugal force equivalent to 900 
 revolutions of the 20-inch 
 wheel. At the end of the 
 five minutes the bottle is 
 filled with hot water to 
 the base of the neck and 
 Then it is filled with hot 
 
 column is near the 
 neck of the bottle, 
 Experience has 
 and two addi- 
 
 whirled for two minutes, 
 water until the top of the fat 
 top of the graduation on the 
 and whirled for one minute, 
 shown that the three whirlings 
 tions of water are necessary to 
 insure a clear column of fat 
 which will permit of accurate 
 reading. Unless there are suf- 
 ficient bottles to fill the ma- 
 chine, care must be taken to 
 balance the weight exactly by 
 arranging the bottles evenly on 
 opposite sides of the machine. 
 FIG. 166. Transferring milk If the number of tests made 
 
 from pipette to test bottle. . 
 
 is odd, an extra bottle filled with 
 
 water is used to preserve the balance. Usually two tests 
 are made of each milk, one to check the other. 
 
 414. Reading the Fat. The fat must be in a liquid con- 
 dition in order to make an accurate reading. After the 
 
 \ 
 
368 
 
 APPLIED CHEMISTRY 
 
 whirling is completed the bottle should be allowed to stand 
 for a few minutes in water at 150 F. The fat should then 
 be read from the lowest to the highest point, the difference be- 
 tween the bottom and top readings being the percentage of 
 fat in the milk. Each of the smaller divisions is two tenths 
 
 of a per cent, and as the 
 fat can be read between 
 the divisions, it is pos- 
 sible to state the per- 
 centage to one tenth of 
 one per cent. Read- 
 ings may be more accu- 
 rately made by the use 
 of a small pair of di- 
 viders. The dividers 
 should be so set that the points are at the 
 extreme top and bottom of the fat column 
 (Fig. 167) ; then if the lower point of the 
 divider is placed at the zero mark, the upper 
 part will indicate the percentage of fat. Ac- 
 curately graduated test bottles and pipettes 
 can usually be easily obtained. In some 
 states, however, all the glassware for the 
 Babcock test is required by law to be veri- 
 fied by the experiment station or other 
 agency designated by the legislature of the state. 
 
 415. Testing Skim Milk and Buttermilk. The skim milk 
 from the separator should frequently be tested to make sure 
 that the separator is thoroughly skimming the milk. Like- 
 wise the buttermilk is tested to guard against losses of fat 
 due to incomplete churning. The tests for these products are 
 made in the same way as for whole milk, except that a special 
 
 FIG. 167. 
 Reading the amount 
 of butter fat. 
 
TESTING MILK 
 
 369 
 
 double-neck bottle (Fig. 168) is used. The milk and acid are 
 poured into the bottle through the larger side neck. The 
 smaller neck in the center of the bottle is 
 graduated to read 0.05 per cent and may be 
 estimated between the marks to 0.01 per cent. 
 If the separator is working properly, the test 
 will not show more than 0.05 per cent of fat 
 in the skim milk, and good churning should 
 leave not to exceed 0.2 to 0.3 per cent of fat in 
 the buttermilk. 
 
 416. Testing Cream. It is much more diffi- 
 cult to make an accurate test of butter fat in 
 cream than in milk. Cream varies in fat con- 
 tent from about 12 per cent to over 40 per 
 cent. As the test bottle for milk reads to 10 
 per cent only, it is necessary to have a special 
 bottle for cream (Fig. 169). The 
 bottle in common use has a much 
 wider neck than the milk bottle 
 and is graduated to 30 per cent. 
 The cream cannot be accurately 
 measured, since the pipette will skim milk and 
 
 *; buttermilk. 
 
 not deliver 18 grams or cream. 
 The larger the percentage of fat, the lower the 
 weight of cream delivered by the pipette. To 
 make an accurate test it is necessary to weigh 
 the cream instead of measuring it. This may 
 FIG 169 - ke done on any balance, but when a great 
 Bottle for test- many tests are to be made the specially de- 
 
 ing cream. 
 
 signed balance (Fig. 170) will be found con- 
 venient. The bottle is first balanced; then an 18-gram 
 weight is placed on the side opposite to the bottle, and cream 
 EV. CHEM. 24 
 
 FIG. 168. 
 Test bottle for 
 
370 
 
 APPLIED CHEMISTRY 
 
 is slowly run into the bottle until it just balances the weight. 
 The test is then made in the same manner as for milk. If 
 the cream runs over 30 per cent fat, 9 grams are used and 
 nine cubic centimeters of water are added to the cream 
 in the bottle before the acid is introduced. The reading is 
 
 then doubled to give the 
 correct percentage of fat. 
 A fairly accurate test 
 of the fat in cheese may 
 be made by weighing out 
 9 grams of the sample 
 and placing it in the 
 cream bottle with 17.6 
 cubic centimeters of 
 warm water. The cheese 
 should be allowed to soak 
 
 FIG. 170. Scales used in cream test. 
 
 for an hour or more, after 
 
 which the acid should be added, and the test should be con- 
 ducted in the usual way. To obtain the percentage of fat in 
 the cheese the reading should be doubled. 
 
 417. Composite Tests. Where large herds of cows are to 
 be tested, or in the case of creameries with a large number of 
 patrons, the daily testing of the milk is expensive and time 
 consuming. In such cases very good results may be obtained 
 by use of the composite test. A small sample from each 
 milking is placed in a bottle with a preservative such as 
 potassium bichromate or mercuric chloride (corrosive sub- 
 limate), and a test of the composite sample is made at the end 
 of a week or ten days. To make such a composite sample 
 represent the true average of the various milkings, the amount 
 added to the bottle each time should be proportional to the 
 weight of the milk at that milking. The entire sample 
 
TESTING MILK 371 
 
 should be well mixed after each addition of milk. The test 
 is made as described for ordinary milk. Various devices 
 have been invented for taking proportional samples of the 
 milk. The desired result may be obtained also by taking 
 2 cubic centimeters of the milk for the composite sample 
 for each pound in weight of the milk at each milk- 
 ing. 
 
 418. Use of the Lactometer. By the use of the lactometer 
 and the Babcock test it is possible to make a fairly accurate 
 estimate of the other solids in the milk in addition to the fat. 
 In the laboratory, the creamery, and the cheese factory it is 
 customary to speak of all the solids of milk exclusive of the 
 fat as solids not fat (S. N. F.). 
 
 The lactometer is an apparatus for determining the specific 
 gravity of the milk. It consists of a glass spindle with a long 
 slim neck, which will float in milk or other liquid. The lower 
 the specific gravity of the liquid, the deeper the spindle sinks 
 in it, and the heavier the liquid, the higher the spindle floats. 
 All the solids found in milk with the exception of the fat are 
 heavier than water and, therefore, increase the specific 
 gravity of the milk. Since butter fat, on the other hand, is 
 lighter than water (specific gravity about 0.9), the presence 
 of fat counteracts the increase of specific gravity due to the 
 other solids. Milk varies in specific gravity from 1.029 to 
 1 .034. The lactometer most commonly used is the Quevenne 
 lactometer (Fig. 171). This instrument is so graduated that 
 the figures on the neck represent the second and third 
 decimal places of the specific gravity; that is, 32 on the 
 lactometer is equivalent to a specific gravity of 1.032. 
 These figures of the scale on the neck of the instrument are 
 called for convenience lactometer degrees. The lactometer 
 reading is made by placing the milk in a tall cylinder and 
 
372 
 
 APPLIED CHEMISTRY 
 
 floating the lactometer in it. When the lactometer has 
 come to rest, the reading is taken at the level of the milk's 
 surface. The lactometer gives the correct 
 reading only when the temperature of the 
 milk is 60 F. If it is not at that tem- 
 perature, 0.1 should be added to the lactom- 
 eter reading for each degree of temper- 
 ature above 60, or the same number 
 should be subtracted for each degree below. 
 In no case should readings be made if the 
 temperature varies more than ten degrees 
 from the normal (60 F.). 
 
 It has been found by experiment that 
 the percentage of solids not fat in a milk 
 is equal to one fourth of the lactometer 
 reading plus two tenths of the percentage 
 of fat. This statement is briefly expressed 
 1 1 111! in what is known as the Babcock formula 
 
 for solids not fat : 
 
 In the formula L stands for the lactometer 
 reading and / for the percentage of fat. 
 For example, if the lactometer reading is 
 34 and the fat is 3.5 per cent, then 
 
 FIG. 171. Lactom- 
 eter. 
 
 The sample of milk, therefore, contains 9.2 
 per cent of solids not fat. 
 
 The variations in the solids other than 
 fat in milk are not very great even when 
 the different breeds of cows are con- 
 
TESTING MILK 
 
 373 
 
 sidered. Adding water to milk decreases the percent- 
 age of solids not fat. The above formula, therefore, 
 may be used to detect watered milk. Many states have 
 established by law a standard for fat and total solids in 
 milk. A common legal requirement is a minimum of 
 3.25 per cent of fat and 9 per cent solids not fat. If the 
 solids not fat in a milk are below 9 per cent, the milk is 
 assumed to be watered. If the fat falls below 3.25 per 
 cent, the milk is declared to be skimmed. By the use of the 
 Babcock test and the lactometer it is possible, therefore, to 
 determine whether the milk has been skimmed or watered, 
 or both skimmed and watered. 
 
 419. Acid Test. It is often desirable to know the amount 
 of acid in a sample of milk or cream. This can easily be 
 determined by the use of the 
 Farrington alkali tablets. These 
 tablets consist of a carefully 
 weighed quantity of sodium car- 
 bonate mixed with a little phe- 
 nolphthalein indicator (138). To 
 make the test, dissolve 5 tablets in 
 97 cubic centimeters of water. 
 Measure 17.6 cc. of the milk into 
 
 , FIG. 172. Graduated cylin- 
 
 a White CUp and add the alkali der and white cup used for a test 
 i , i i . . . .-, . n of milk or cream. 
 
 solution slowly, stirring the milk 
 
 thoroughly after each addition. The acid in the milk will 
 at first destroy the color of the indicator. The alkali solu- 
 tion is added until a pink color is imparted to the milk which 
 does not immediately disappear upon stirring. Each cubic 
 centimeter of the alkali used is equivalent to 0.01 per cent of 
 lactic acid ; for example, if 35 cc. of the alkali solution are 
 used the acidity of the milk is said to be 0.35 per cent. 
 
374 APPLIED CHEMISTRY 
 
 EXERCISES 
 
 Ex. 256. Read carefully paragraphs 409 to 413 and test a sample of 
 milk from home according to the method described. Why is it desirable 
 for the purchaser to know the amount of fat in milk ? What use can the 
 farmer make of a simple method of testing milk ? Is the Babcock test 
 thoroughly practical ? 
 
 Ex. 257. If possible make a week's test of each cow in a herd in the 
 neighborhood of the school. Have a pint bottle for each cow. Place in 
 it as much powdered potassium bichromate as will stand on a dime. 
 Arrange for some student to be present at each milking, to weigh the milk 
 from each cow and place the sample in the proper bottle. Use 2 cc. 
 of milk for each pound the cow produces. Read paragraph 417 on com- 
 posite test. At the end of the week test each composite sample and 
 calculate how much butter fat each cow produced during the week. 
 
 Ex. 258. If the school has the proper apparatus, make tests of skim 
 milk, cream, and cheese as described in the text. 
 
 Ex. 259. Determine the fat in a sample of milk by the Babcock test, 
 and take the lactometer reading as described in paragraph 418. Calcu- 
 late the solids not fat in the milk. \ Assuming that the standard for 
 milk is 3.25 per cent fat and 9 per cent solids not fat, is a sample with a 
 lactometer reading of 32 and a fat content of 3.4 per cent watered ? 
 
 Ex. 260. Dissolve 5 Farrington alkali tablets in 97 cc. of water in a 
 100 cc. graduated cylinder and test a sample of milk from home for 
 acidity according to paragraph 419. If possible test a sample of butter- 
 milk in the same way. 
 
CHAPTER XLIV 
 LEAVENING AGENTS 
 
 420. Wheat Bread. Bread of some kind has been used by 
 mankind from the earliest times. During the earlier periods 
 it consisted chiefly of powdered meal and water, baked in 
 the sun or on hot stones. This kind of bread has the same 
 characteristics as modern hard-tack or hoe-cake, so far as 
 digestibility is concerned. It has great density, is difficult 
 to masticate, and presents but little surface to the action of 
 the digestive juices. Such bread is said to be unleavened. 
 
 Very early in the history of the human race leavened 
 bread seems to have been used. Experience must have 
 taught the semicivilized tribes that a light and porous loaf 
 was more palatable and more digestible than a dense one, 
 for nearly all peoples now have some method of " raising" 
 bread and making it light. 
 
 421. To Make a Light Loaf. The incorporation into the 
 dough of bubbles of some kind of gas is necessary to make 
 a light loaf. The possibility of a light, porous loaf of 
 wheat bread is due to the gluten of the wheat (319). 
 This substance, when moistened, forms a sticky elastic mass, 
 which incloses the gas bubbles and prevents their escape. 
 When the bread is heated in baking, the gluten loses its elas- 
 ticity, and becomes stiffened, and retains its light porous 
 condition. Three general methods are used to introduce the 
 gas, namely, mechanical, biological, and chemical methods. 
 
 The best known example of the mechanical methods is the 
 " beaten biscuit" of the South. In this case air is introduced 
 
 375 
 
376 
 
 APPLIED CHEMISTRY 
 
 into the dough by long-continued beating, which makes it 
 somewhat porous. When the dough is heated in the oven, 
 the air expands and increases the porosity of the product. 
 
 The so-called aerated bread is made by mixing the dough 
 with carbonated water such as is used in soda-water foun- 
 tains. The mixer is so constructed that the carbon dioxide 
 is kept under high pressure during the mixing. When the 
 mixing is completed, the pressure is released and the expan- 
 sion of the gas makes the dough light, as does the further 
 expansion of the gas when the dough is placed in the oven. 
 The use of eggs for making light cakes, such as sponge cake 
 and angel cake, is another example of the mechanical method. 
 The air which is beaten into the egg albumin supplies the 
 
 bubbles of gas needed to make 
 the cake light. 
 
 422. Use of Yeast in Making 
 Bread Light. Yeast is the sub- 
 stance most commonly used to 
 make bread light. Condensed 
 yeast consists of a mass of 
 microscopic plants (Fig. 173) 
 which grow or multiply rapidly 
 in the moist dough or sponge, 
 especially if some sugar has been 
 added. During its growth the 
 yeast plant secretes enzymes 
 which bring about the fermen- 
 tation of the sugars with the formation of alcohol and carbon 
 dioxide (362) : 
 
 FlQ. 173. Yeast plants. 
 
 CeH^Oe 
 
 glucose 
 
 2 C 2 H 5 OH 
 
 alcohol 
 
 2 CO 2 . 
 
 carbon 
 dioxide 
 
LEAVENING AGENTS 
 
 377 
 
 When yeast is added to the dough, and the mixture is put in 
 a warm place, the yeast grows and carbon dioxide is produced. 
 The gas permeates the dough, but cannot escape because of 
 the tenacious character of the mass. As a result the dough 
 rises, that is, it swells up because of the bubbles of gas that 
 have been formed within it. 
 
 After the dough has risen, it is kneaded for the purpose of 
 breaking up the large bubbles and distributing the gas evenly 
 
 FIG. 174. Cross sections of light loaves of bread. The variation in size is due 
 to differences in the quality of the gluten in the two flours. 
 
 throughout the mixture. When the dough is shaped into 
 loaves, the fermentation continues because the yeast is still 
 growing, and the further evolution of carbon dioxide causes 
 the dough to rise again. 
 
 When the loaves are placed in the oven, the first action of 
 the heat expands the bubbles of carbon dioxide and the loaf 
 is made more porous and light. The yeast is killed, fermen- 
 tation stops, and the alcohol and part of the water are vapor- 
 
378 
 
 APPLIED CHEMISTRY 
 
 ized and driven off. At the same time the starch grains are 
 ruptured by the heat, and the gluten is stiffened and loses its 
 elasticity. The heat of the oven (350 to 400 F.) converts 
 part of the starch on the outer edge of the loaf into dextrin 
 (312), which is one reason why the crust of the bread is 
 sweeter than the crumb. The interior of the loaf never gets 
 much above 212 F., because the water in the interior of the 
 loaf is being continually changed into steam. 
 
 423. Salt-rising Bread. This is another example of a bread 
 which is made light by a biological process. To make salt- 
 rising bread, corn meal 
 and a little baking soda 
 are mixed with warm 
 milk. After some hours 
 this batter begins to fer- 
 ment and carbon dioxide 
 is produced. Dough- is 
 made as for ordinary 
 bread and this mixture 
 is used in the place of 
 yeast. The process of 
 handling is from this 
 point the same as that 
 described for yeast bread. 
 For a long time the cause 
 of the fermentation in 
 salt-rising bread was not 
 understood. It has been discovered recently, however, that 
 it is due to certain gas-forming bacteria that are found 
 associated with the corn meal. 
 
 The ancient method of preserving a little of the dough 
 from each batch of bread to act as the leaven for the next is 
 
 FIG. 175. Making bread in the Orient. 
 Kneading dough with leaven. 
 
LEAVENING AGENTS 379 
 
 still followed in some countries. This small bit of old dough 
 carries a sufficient number of yeast plants to start the fermen- 
 tation when it is mixed with a new lot of dough, and thus 
 " a little leaven leaveneth the whole lump." 
 
 424. Ammonium Bicarbonate. The use of ammonium 
 bicarbonate is the simplest of the chemical methods of raising 
 bread. The ammonium salt is dissolved in the water used 
 in making the dough. When the mass is heated, the bi- 
 carbonate decomposes into gaseous products : 
 
 NH 4 HCO 3 -> NH 3 + H 2 O + CO 2 . 
 
 The evolution of ammonia and carbon dioxide and their 
 expansion when heated make the bread porous and light. 
 In skillful hands this method is very successful and has the 
 advantage of leaving no solid residue. The ammonia is 
 driven off by the heat of baking. 
 
 425. Sour Milk and Soda. These leavening agents have 
 long been used. The lactic acid in the sour milk reacts with 
 sodium bicarbonate, also called baking soda, or saleratus, 
 and liberates carbon dioxide : 
 
 NaHCO 3 ->- Na.C 3 H 5 O3 + H 2 O + CO,. 
 
 lactic acid sodium lactate 
 
 When properly followed, this method of leavening is very 
 successful, but it has the disadvantage that it is sometimes 
 difficult to adjust the proportions of the sour milk and soda. 
 If too much sour milk is used, the product has a sour taste. 
 If too much soda is used, the excess of bicarbonate is changed 
 by the heat of the oven into the normal carbonate, which 
 gives a soapy taste to the bread : 
 
 2 NaHCO 3 -^ Na 2 CO 3 + CO 2 + H 2 O. 
 
380 APPLIED CHEMISTRY 
 
 Occasionally baking soda and hydrochloric acid are used as 
 leavening agents. In this case the soda is mixed with the 
 flour and the hydrochloric acid is added to the water which is 
 used in mixing the dough : 
 
 NaHCO 3 + HC1 -- NaCl + H 2 O + CO 2 . 
 
 426. Baking Powders. The difficulty of measuring the 
 exact amounts of acid and bicarbonate when the above 
 methods are used has led to the manufacture of commercial 
 baking powders. In baking powders an acid salt is used 
 instead of the free acid. 
 
 Tartrate baking powder is composed of baking soda and 
 cream of tartar. These substances do not react with 
 each other while dry, but when moistened the following 
 reaction takes place : 
 
 NaHCO 3 + KH CJ^O, ->- KNa C 4 H 4 O 6 + H 2 O + CO 2 . 
 
 Phosphate baking powders consist of baking soda and 
 calcium mono-phosphate, the same compound that occurs in 
 the fertilizers known as acid phosphate or superphosphates. 
 The reaction in this case is as follows : 
 
 2 NaHCO 3 + CaH 4 (PO 4 ) 2 
 
 -> CaHPO 4 + Na 2 HPO 4 + 2 H 2 O + 2 CO 2 . 
 
 Alum baking powders are made from baking soda and 
 ammonium alum. The reaction here is a deep-seated one : 
 
 2 NH4A1(SO 4 ) 2 + 6 NaHCO 3 
 
 -^2 A1(OH) 8 + 3 Na2SO 4 + (NH 4 ) 2 SO 4 + 6 CO 2 . 
 
 Starch is added in the manufacture of all baking powders to 
 keep the materials dry, and to coat each particle of the acid 
 salt and the carbonate in order to prevent their acting upon 
 
LEAVENING AGENTS 381 
 
 each other while stored. From 20 to 25 per cent of starch is 
 sufficient for this purpose. 
 
 427. Healthfulness of Baking Powders. It will be seen 
 from the above equations that one or more products of 
 chemical reaction remain in the food after baking. The 
 possible harmful action of these substances has been the 
 subject of much discussion, but there are few reliable ex- 
 perimental data on the subject. There is no reason to 
 believe that the sodium lactate produced when soda and 
 sour milk are used has any harmful effects. Cream of tartar 
 and soda produce Rochelle salt, which is a laxative, but 
 which probably has no effect in the small quantities consumed 
 with the food. The same statement may be made regarding 
 the sodium phosphate produced by the phosphate baking 
 powders. More has been said against the alum baking 
 powders than any of the others, and many physicians believe 
 that the residue of aluminum hydroxide left by them is inju- 
 rious to health. Since nothing is to be gained by their use 
 except a very small saving in expense, it would be well to 
 avoid these powders, so long as there is a question about it. 
 
 428. Homemade Baking Powder. A baking powder can 
 be prepared at home from the following ingredients : 
 
 Cream of tartar, dried .' . . 1 pound 
 
 Baking soda | pound 
 
 Starch ^ pound 
 
 Thoroughly dry the starch and cream of tartar in a warm 
 (not hot) oven, Divide the starch into two parts, and mix 
 the soda with one part, and the cream of tartar with the 
 other. Then mix the whole thoroughly and keep the mixture 
 in cans or bottles in a dry place. 
 
 429. Shortening. Pie crust and similar forms of pastry 
 are not leavened. Instead the flour is so treated that when 
 
382 APPLIED CHEMISTRY 
 
 heated it crumbles readily into thin flakes. This is accom- 
 plished by the method known by the housewife as shortening, 
 and consists in mixing a fat, such as butter, lard, or oil, with 
 the flour in making the dough. The fat destroys the elas- 
 ticity of the gluten, making it break off short when worked 
 instead of allowing it to remain tenacious, as it is in ordinary 
 dough. The result of this treatment is a flakiness that has 
 the effect of exposing a large surface to the digestive fluids ; 
 but this good effect is counteracted by the presence of the 
 large amount of fat, which produces a greasy surface that 
 interferes with the action of the digestive juices upon the 
 proteins and carbohydrates. Because of its expansion under 
 the heat of the oven, the air folded into the dough is probably 
 another factor in making the pastry light and flaky. 
 
 EXERCISES 
 
 Ex. 261. Is the use of wheat bread of modern origin? How was 
 the first bread probably made ? Why is a light loaf desirable ? What 
 is necessary to make a light loaf ? What is the function of the gluten 
 in bread making? What change takes place in the gluten when the 
 bread is baked ? 
 
 Ex. 262. .What is the principle underlying the making of beaten 
 biscuits? How is aerated bread made? What makes it light? Ex- 
 plain how eggs make possible the production of a light cake such as 
 sponge cake. 
 
 Ex. 263. Explain how the use of yeast makes a light loaf possible. 
 Devise an experiment to show that carbon dioxide is given off by the 
 sponge in bread making. Explain the formation of the numerous holes 
 in a loaf of bread. Why does the baked loaf retain its shape when the 
 dough will not? 
 
 Ex. 264. What makes the bread light in the case of salt-rising bread ? 
 Why is the corn meal added? Explain the ancient method of saving 
 the leaven from one baking to another. 
 
 Ex. 265. When ammonium carbonate is used to raise bread, what 
 chemical change takes place ? What advantage has ammonium carbon- 
 
LEAVENING AGENTS 383 
 
 ate over other baking powders ? Explain the use of baking soda with 
 sour milk. Add some baking soda to sour milk at home and prove that 
 carbon dioxide is given off. What is the chief difficulty in using these 
 materials ? What happens if too much soda is used ? 
 
 Ex. 266. Moisten samples of 'baking powder with water and de- 
 termine whether carbon dioxide is evolved. What are the three general 
 types of baking powders on the market? Obtain several samples of 
 baking powder and test to see if they are tartrate, phosphate, or alum 
 powders, as follows : 
 
 (a) Test for phosphate by burning the powder to destroy the starch, 
 and then heat with a little nitric acid and add ammonium molybdate 
 reagent. 
 
 (6) Test for alum. Dissolve in water and filter. To the filtrate add 
 a little hydrochloric acid and some bafium chloride solution. A white 
 precipitate indicates alum. (Note. This is really a test for sulphates, 
 but as alum is the only sulphate used in baking powders it serves the 
 purpose.) 
 
 (c) There is no easy test for tartrate, but if the powder is not a phos- 
 phate nor an alum powder, it is undoubtedly made with tartrate. 
 
 Ex. 267. What is the residue left in the food when sour milk and 
 soda are used? When cream of tartar and soda are used? When a 
 phosphate powder is used ? In case of an alum powder ? Is any objec- 
 tion raised to any of these powders ? What type of baking powder do 
 you use at home ? 
 
 Ex. 268. Have the class make a baking powder according to the 
 directions in paragraph 428. Divide among the members of the 
 class and have it tested in their homes. Call for reports. 
 
 Ex. 269. (Teacher) From a cupful of flour prepare gluten as in 
 exercise 197. Note the elasticity of the gluten. Now work thoroughly 
 into the gluten a good-sized piece of lard. What effect does the fat 
 have on the elasticity of the gluten? What is meant by shortening? 
 How does it make pastry light and flaky? Why is pastry hard to 
 digest? 
 
CHAPTER XLV 
 
 FOOD PRESERVATION, ANTISEPTICS, AND DISIN- 
 FECTANTS 
 
 430. Why Foods Spoil. The fermentation and decay of 
 foods, which render them unfit for consumption, are due to 
 the growth of molds and microorganisms such as yeast and 
 bacteria (Fig. 176). These organisms act upon the carbo- 
 hydrates and produce alcohol, carbon dioxide, and various 
 organic acids. Some of the bacteria cause the decay or pu- 
 trefaction of the proteins, with the production of the foul 
 
 FIG. 176. Bacteria. 1. Typhoid fever. 2-5. Forms of bacteria found 
 
 in milk. 
 
 odors so noticeable in decaying meat and other high 
 protein foods. Some of these organisms produce from 
 the proteins poisonous substances which are known as 
 ptomaines (326). Without some method of preserving 
 food the human diet would at least lack the variety that 
 is now possible. Molds, yeast, and bacteria are present 
 everywhere in the air, especially when the air is dust 
 laden. While foods should be protected from dust and 
 dirt, which always contain bacteria, it is practically impos- 
 sible to prevent entirely their entrance into the food ma- 
 
 384 
 
FOOD PRESERVATION AND DISINFECTANTS 385 
 
 terials. Hence if food is to be preserved, some method must 
 be used to destroy these organisms or to prevent their growth. 
 
 431. Preservation by Drying. The conditions necessary 
 for the growth of the organisms that cause foods to spoil are 
 the presence of moisture and warmth. Materials that are 
 
 Very dry, such as 
 flour and crackers, 
 will keep indefinitely 
 if not allowed to be- 
 come damp. The 
 drying of meats, 
 fruits, and vegetables 
 has been practiced 
 from early times. 
 Formerly these food 
 products were all 
 dried in the sun ; but 
 now many devices 
 are in use for the 
 artificial drying of 
 these materials. 
 
 432. Refrigeration. 
 
 FIG. 177. The preservation of foods by diying. 
 
 A low temperature 
 retards the growth 
 of the organisms that produce fermentation and decay, and 
 consequently the lower the temperature at which foods are 
 held the longer they will keep. The cold storage business, 
 which has grown to enormous proportions, is based upon this 
 principle. Food substances that can be frozen without 
 injury can be kept almost indefinitely in the frozen state. 
 Since cold and freezing do not kill the bacteria outright but 
 merely prevent their growth, perishable substances when 
 EV. CHEM. 25 
 
386 APPLIED CHEMISTRY 
 
 removed from cold storage will, of course, spoil the same as 
 fresh materials. The temperature produced in the home 
 ice box or refrigerator is not low enough to retard the decom- 
 position of food for very long periods. 
 
 433. Preserving in Strong Solutions. Yeasts and bacteria 
 cannot grow in concentrated solutions. When the solution 
 contains more than 20 per cent of solids, the osmotic action 
 of the solution is so great that it extracts water from the living 
 cell and causes the protoplasm to collapse, resulting in the 
 death of the cell. The method of preserving meats and vege- 
 tables by placing them in strong brine depends upon this fact. 
 If the brine is too weak, the organism can grow and the food 
 spoils. Dry salting of meats is another instance of the same 
 method of preservation. The salt rubbed into the meat dis- 
 solves in the moisture present and forms a brine which is 
 strong enough to prevent the growth of bacteria. 
 
 Approximately fifty per cent of jelly and jam consists of 
 the sugar added in their manufacture. Sugar is a food for 
 bacteria and yeast when in dilute solution, but in the con- 
 centration used in jellies and jams it destroys these organisms 
 by its great osmotic action. The heating incident to pre- 
 paring these foods also assists in destroying these organisms. 
 
 434. Preservation by Heat. The organisms that cause 
 fermentation and decay in foods are killed at the temperature 
 of boiling water if the heating is continued for some time. 
 Foods that are boiled or otherwise heated to this temperature 
 will, therefore, keep indefinitely if properly protected from 
 further infection. The canned vegetables which occupy 
 such a large place in the modern dietary are preserved by this 
 method. The vegetables are placed in cans and heated and 
 the . cans are sealed while very hot. The heating is commonly 
 done under pressure to make the temperature still higher and 
 
FOOD PRESERVATION AND DISINFECTANTS 387 
 
 the destruction of the organisms more certain. If the ends 
 of the can bulge outward or if gas escapes under pressure 
 when the can is punctured it is a sign that the food in the can 
 has fermented. Such goods should be rejected. 
 
 Bottled fruits and vegetables prepared at home depend 
 upon the same principle for their preservation. If the bottles 
 and the tops and the rubbers are sterilized and the foods are 
 completely sterilized by cooking, they will keep indefinitely. 
 If any of the germs are undestroyed, fermentation will subse- 
 quently take place. Some bacteria form spores with very 
 thick cell walls which are resistant to heat. Unless all 
 these are killed they may later germinate and cause the food to 
 ferment. They may be killed by long-continued heating, 
 or by the very high temperature produced under pressure. 
 As too long a period of boiling injures the quality of some 
 of the food products, the method of intermittent heating is 
 sometimes used. In this method the food is heated for short 
 periods at three different times, a day or two apart. The 
 spores germinate in the intervals between the heatings and 
 thus may easily be killed. Small pressure heaters suitable 
 for use in the home are now on the market, and their use 
 makes the canning process more reliable. 
 
 A modification of the canning procedure known as the 
 cold pack method (Fig. 178) is growing in favor and is largely 
 used by the members of the girls' canning clubs. In this 
 method the material is first blanched, that is, cooked for a 
 short time in boiling water or steam. It is quickly dipped 
 into cold water, and afterward packed into hot jars which 
 are then filled with boiling water, immersed in hot water, 
 and boiled for periods of from ten minutes to three hours, 
 depending upon the material that is being canned. 
 
 It has been stated that temperatures of 140 to 150 F. will 
 
388 
 
 APPLIED CHEMISTRY 
 
 kill most of the germs and delay the spoiling of foods. About 
 the only practical application is the pasteurizing of milk. 
 
 435. Chemical Preservatives. Sometimes chemicals are 
 added to foods to prevent their fermentation. The chem- 
 icals most commonly used are borax, boric acid, benzoic acid, 
 sodium benzoate, salicylic acid, sodium salicylate, formalde- 
 hyde, sulphur dioxide, and sodium sulphite. The use of some 
 of these substances is illegal, while others may be legally used 
 
 vw kft> 
 
 ilfisK 
 
 FIG. 178. Preserving by the cold pack canning method. 
 
 if their presence is indicated on the package. The harmful- 
 ness of some of these preservatives is a matter of dispute ; but 
 as their use is unnecessary, it is best to avoid all canned or 
 bottled products containing any preservative. The use of 
 these chemicals makes it possible to can poor products under 
 careless and unsanitary conditions. With good vegetables 
 or fruits and clean factory conditions the use of chemical 
 preservatives is absolutely unnecessary, and it seems reason- 
 able to believe that any chemical that will prevent the 
 growth of bacteria will also interfere with digestion. The 
 
FOOD PRESERVATION AND DISINFECTANTS 389 
 
 use of formaldehyde in milk is especially pernicious, as milk 
 is so largely used in feeding babies and young children. A 
 sample of milk or moist food product which keeps a long time 
 when exposed to the air probably contains a chemical pre- 
 servative. Such products should not be used as foods. 
 
 436. Antiseptics are substances that check the growth of 
 bacteria. They may not kill all the bacteria present, how- 
 ever. Some of the same substances that are used as food 
 preservatives are also employed as antiseptics. Most of the 
 antiseptic mouth washes, such as listerine, have borax and 
 boric acid as their basis, associated usually with thymol or 
 some other aromatic antiseptic. A solution of boric acid is 
 often used also as an antiseptic eye wash. Various anti- 
 septics are used also as a wash or dressing for wounds in order 
 to destroy any bacteria which may have found their way into 
 the wounds. Such bacteria as the tetanus germ that pro- 
 duces lockjaw are often present in dirt and may be introduced 
 into a wound. Hydrogen peroxide, a weak solution of 
 carbolic acid, listerine, or even alcohol may be employed as 
 antiseptic applications in such cases. Every cut or other 
 break in the skin should be immediately washed with one of 
 the above solutions, especially if any dirt is known to have 
 entered the wound. Physicians often dress wounds with 
 iodoform, which is another antiseptic. 
 
 437. Disinfectants, or germicides, are substances that will 
 kill all bacteria. Some of these materials are antiseptics 
 in dilute solutions and disinfectants in greater concentration. 
 Disinfectants are used to destroy bacteria and thereby 
 remove the danger of infection. A solution of mercuric 
 chloride (corrosive sublimate) is quite commonly used as a 
 disinfectant, as is also strong carbolic acid. Bleaching 
 powder, or chloride of lime (124), has strong germicidal 
 
390 
 
 APPLIED CHEMISTRY 
 
 properties because of the chlorine liberated from it. All 
 articles used in cases of contagion should be immersed in a 
 disinfectant solution before being removed from the sick 
 room. Heat is one of the best disinfectants, and articles that 
 will stand boiling in water can best be sterilized in that way. 
 Sulphur dioxide has long been used for disinfecting bed- 
 rooms after cases of contagious diseases. It is often formed 
 by burning sulphur in the room; or the liquid sulphur 
 dioxide, which may be purchased in small metal cylinders, 
 is used. Both chlorine and sulphur dioxide are bleaching 
 agents, and their use as household disinfectants is largely 
 superseded by the use of formaldehyde, which is a powerful 
 germicide and has no bleaching action (287). Specially 
 
 devised machines for man- 
 ufacturing formaldehyde 
 on the ground are used 
 when large areas are to be 
 fumigated. 
 
 For use in disinfecting 
 on a smaller scale, the 
 solid substance sold under 
 such names as formacone 
 or paraform is convenient. 
 This is a condensation 
 product of formaldehyde. 
 Under certain conditions several molecules of formalde- 
 hyde can be made to combine to form the white solid sub- 
 stance mentioned above, which is known to the chemist 
 as paraformaldehyde. This substance is made into tablets 
 or candles and when heated or boiled with water it is changed 
 back into gaseous formaldehyde, and thus provides an easy 
 and efficacious method of disinfecting a room after sickness. 
 
 FIG. 179. A formacone candle. 
 
FOOD PRESERVATION AND DISINFECTANTS 391 
 
 EXERCISES 
 
 Ex. 270. What causes foods to spoil ? How generally are molds and 
 bacteria distributed? How does a knowledge of food preservation 
 affect our dietary? What conditions are necessary for the growth of 
 molds and bacteria ? Why do not perfectly dry foods spoil ? What can 
 you say of drying as a method of food preservation ? What effect has 
 cold on the keeping of food ? Does freezing kill the bacteria outright ? 
 
 Ex. 271. How does a strong brine prevent the fermentation of 
 foods ? If the brine is too weak what happens ? Explain the preserva- 
 tion of meat by dry salting. Why are jellies and jams so easily kept ? 
 Would fruits keep if only a little sugar was added to them ? 
 
 Ex. 272. Explain the theory of keeping fruits and vegetables by 
 canning. Why do factories heat them under pressure? Why should 
 canned goods be discarded if the can bulges outward ? Why are vege- 
 tables sometimes heated on three different days ? Does anyone in your 
 neighborhood use a pressure heater in canning fruits and vegetables ? 
 What is meant by the cold pack method? Write to your Agricultural 
 College for bulletins describing the cold pack method and try canning 
 some kind of vegetable by this method. 
 
 Ex. 273. What chemicals are sometimes used as food preservatives ? 
 What do you think of the policy of using these chemicals ? Are they 
 necessary with good materials ? Examine the cans and bottles that come 
 into your home and see if any of them state that a preservative is used. 
 
 Ex. 274. To a pint of milk add two or three drops of formaldehyde. 
 Set the bottle aside and see how long it takes the milk to sour. Why 
 should milk be regarded with suspicion if it keeps too long ? Test sus- 
 pected milk for formaldehyde as follows : Fill a test tube one third full 
 of the milk. Hold the tube in an inclined position and carefully pour 
 down the side of the tube a little sulphuric acid to which has been added 
 a drop of ferric chloride solution. If formaldehyde is present a violet 
 color forms, where the acid and milk came into contact. 
 
 Ex. 275. What is meant by antiseptics ? Of what are most of the 
 antiseptic washes made ? Why is it dangerous to get dirt into a wound ? 
 How should cuts be treated ? Name some of the more common anti- 
 septics. What is a disinfectant ? In what way does it differ from an 
 antiseptic ? Name some disinfectants. Why is formaldehyde now used 
 in place of sulphur dioxide and chlorine? 
 
CHAPTER XLVI 
 TEXTILES, DYEING, AND BLEACHING 
 
 438. ALL the fabrics ordinarily employed in making cloth- 
 ing are composed of one or more of the four commonly 
 used fibers : cotton, linen, wool, or silk. Of these fibers, cot- 
 ton and linen are of vegetable origin, while wool and silk are 
 derived from animal sources. 
 
 439. Cotton. Cotton fibers are the seed hairs of the cotton 
 plant. Each seed hair is a long, tubular, single plant cell, 
 which during growth is full of protoplasm. As the seed 
 ripens, the protoplasm disappears, the tube collapses, and the 
 hair becomes twisted into a spiral as shown in Figure 180. 
 
 Cotton 
 
 Wool 
 FIG. 180. Textile fibers. 
 
 Silk 
 
 Cotton when pure consists almost wholly of cellulose. It is 
 not readily attacked by alkalies, but is easily destroyed by 
 acids (313). Cotton fabrics are used in larger quantities 
 than those made from any other fiber. 
 
 440. Mercerized Cotton. When cotton is treated with a 
 concentrated solution of sodium hydroxide, it contracts to 
 about three fourths of its original length, and is converted 
 
 392 
 
TEXTILES, DYEING, AND BLEACHING 393 
 
 into a new substance called alkali cellulose. If this material 
 is now stretched to the original length of the cotton and then 
 thoroughly washed and dried, the fiber takes on a silky 
 sheen. Mercerized cotton is stronger than ordinary cotton 
 and has a greater affinity for dyes. 
 
 Cotton is treated also in a number of ways to give the 
 fiber the appearance of silk. Most of the artificial silks, 
 such as near silk, chardonnet silk, and viscose silk, are manu- 
 factured from cotton fiber by special treatments. 
 
 441. Linen also is almost pure cellulose. It is made from 
 the fibers of the straw of the flax plant. The straw is placed 
 in stagnant water where it partially decays, this decay making 
 it possible to separate the fibers from the other parts of the 
 plant by mechanical means. This process is known as 
 retting. Natural retting is sometimes replaced by so-called 
 chemical retting, a process in which the fibers are separated 
 by means of dilute acids instead of by the slower process of 
 decay. The fiber of linen is longer and stronger than that 
 of cotton; it has more luster, and is a better conductor of 
 heat. Linen is also more readily destroyed by strong alkalies 
 and by chlorine and other oxidizing agents. 
 
 442. Wool is the hair of the sheep or goat. There are 
 several varieties of wool, the kind depending upon the animal 
 from which it is obtained. Cashmere comes from the Tibet 
 goat, mohair from the Angora goat, and alpaca from the 
 llama. Not all dress goods bearing these names come from 
 the proper sources, however, since the peculiar characteristic 
 of each can be imitated in common wool. 
 
 Wool is composed of nitrogenous substances containing sul- 
 phur and when burned gives off the peculiar odor of burned 
 hair. All wool fibers have an outer layer of flat cells the 
 edges of which project outward, making a saw-tooth appear- 
 
394 
 
 APPLIED CHEMISTRY 
 
 ance under the microscope (Fig. 180). When the wool 
 fibers are beaten together, this peculiar structure causes them 
 to interlock, and thus makes possible the manufacture of such 
 materials as felt. Wool is readily attacked by alkalies ; even 
 dilute solutions of sodium hydroxide cause it to dissolve. 
 On the other hand, acids affect cotton much more readily 
 
 than they do wool. 
 Much of the cloth that 
 is sold as woolen goods 
 is a mixture of wool 
 and cotton fibers. It 
 is a simple matter to 
 detect such a mixture ; 
 for if the cloth is placed 
 in a dilute solution of 
 sodium hydroxide, the 
 wool will dissolve, 
 while the cotton will 
 remain. An all wool 
 cloth will dissolve com- 
 pletely (Fig. 181). 
 As wool is comparatively expensive, old worn woolen cloth 
 is picked to pieces, woven again into yarn, and used to make 
 new cloth. A fabric made in this way is called shoddy. It 
 has a short fiber and, consequently, is weak and will not wear 
 as well as new wool. 
 
 443. Silk is obtained from the cocoon of the silkworm. 
 The cocoons are heated to 70 C. to kill the worms and then 
 are washed in warm water to soften the silk glue so that the 
 fibers may be reeled. The fibers from several cocoons are 
 twisted together in the reeling process and thus a silk thread 
 is obtained. Silk thread has a beautiful luster and a high 
 
 FIG. 181. Test for all wool fabrics with sodium 
 hydroxide. The all wool cloth appears on the left ; 
 that of mixed wool and cotton on the right. 
 
TEXTILES, DYEING, AND BLEACHING 395 
 
 tensile strength. It is a nitrogenous substance containing 
 no sulphur, differing in this respect from wool. Silk is some- 
 what more resistant than wool to the action of alkalies, but 
 is more readily attacked by acid and is very sensitive to the 
 action of chlorine and other oxidizing agents. 
 
 444. Dyeing. The animal and plant fibers differ greatly 
 in their behavior toward dyestuffs. Many of the substances 
 used to dye cloth are either acid or basic in character. The 
 animal fibers resemble the proteins in chemical behavior and 
 like the proteins have the power of uniting chemically with 
 the acid or basic dye and forming a colored compound that is 
 insoluble in water. It is, therefore, a comparatively easy 
 matter to dye silk or woolen goods. 
 
 Cotton and linen, on the other hand, are largely cellulose, 
 which has no chemical affinity for the dyes. Cellulose is 
 stained by the dyes, but the color is not fast. Cotton and 
 linen are dyed by first introducing into the fiber an insoluble 
 substance that will unite with the dye and hold the color fast. 
 A common method of procedure is first to immerse the cloth 
 in a solution of aluminum chloride or sulphate, or a bath of 
 ordinary alum; then when the cloth is placed in ammonia 
 water, the following reaction takes place : 
 
 A1C1 3 + 3 NH 4 OH -*- A1(OH) 3 + 3 NH 4 C1. 
 
 The aluminum hydroxide (Al(OH)j) is. insoluble and ad- 
 heres to the fibers of the cloth. If the cloth is now immersed 
 in the dye solution, the aluminum hydroxide unites with the 
 dye and holds the color fast. Materials used in this way to 
 fasten the color in fabrics are called mordants. Salts of 
 aluminum are the more common mordants, although salts 
 of tin, iron, and chromium are largely used, as well as tannic 
 acid, the latter especially for the basic dyes. 
 
396 APPLIED CHEMISTRY 
 
 445. Direct Dyes. A few years ago it was thought to be 
 impossible to dye cotton and linen without the use of a 
 mordant to hold the color to the fiber. Recently, however, 
 a number of dyes have been discovered that adhere to the 
 cotton and linen, and some of them possess a satisfactory 
 permanence. These direct dyes are used extensively in 
 dyeing mixed goods consisting of cotton and wool or cotton 
 and silk. The colors are not so fast as those used with a 
 mordant, and they are much more readily affected by strong 
 soaps and alkalies. 
 
 446. Bleaching. The differences in the chemical com- 
 position of the various textile fibers and of the coloring 
 materials to be destroyed make it impossible to use a single 
 method for bleaching cotton, linen, wool, and silk. 
 
 Cellulose is capable of withstanding the action of chlorine, 
 as well as that of weak acids and alkalies. Cotton, therefore, 
 is almost universally bleached by means of chlorine derived 
 from bleaching powder (124). The chlorine is liberated 
 from the bleaching powder by a weak solution of sulphuric 
 acid, and the chlorine reacts with water to liberate oxygen 
 as follows : 
 
 H 2 O + 2 Cl -^ 2 HC1 + O. 
 
 The bleaching is really due to the destruction of the coloring 
 matter by the nascent oxygen (81) and is, therefore, an 
 oxidation process. 
 
 Linen fibers are more sensitive to the action of chlorine 
 than are those derived from cotton. Great care, therefore, 
 must be exercised not to weaken unduly the fiber when 
 bleaching with chlorine. The ancient method of bleaching 
 linen, which is still in use in many parts of the Old World, 
 consists in steeping the cloth in a weak alkaline solution and 
 
TEXTILES, DYEING, AND BLEACHING 397 
 
 then spreading it on the grass to bleach in the sunlight. The 
 cloth is sprinkled from time to time with water. It is finally 
 dipped into buttermilk and then washed with soap and water. 
 
 Wool and silk should never be bleached with chlorine. 
 The bleaching is usually accomplished by means of sul- 
 phurous acid or sodium peroxide. When sulphurous acid 
 is used, the goods are moistened and then subjected to the 
 action of sulphur dioxide produced by burning sulphur (63). 
 
 When sodium peroxide is used, the goods are first immersed 
 in a dilute solution of sulphuric acid, and then the sodium 
 peroxide is added. This substance reacts with the acid to 
 produce hydrogen peroxide (45) thus : 
 
 Na2O 2 + H 2 SO 4 ->- Na 2 SO 4 + H 2 O 2 . 
 
 The hydrogen peroxide readily decomposes, liberating 
 oxygen (81), which is the bleaching agent. 
 
 EXERCISES 
 
 Ex. 276. Examine cotton fibers under the microscope and make a 
 drawing of them. What is the chemical composition of pure cotton? 
 Pour 20 cc. of sulphuric acid into 10 cc. of water. When the mixture 
 is cool, place a piece of cotton cloth in it for a few minutes. Wash the 
 cloth in water and note what effect the acid has on the strength of the 
 fiber. 
 
 Ex. 277. Cover a piece of cotton cloth with a 30 per cent solution of 
 sodium hydroxide for 10 or 15 minutes. Wash the cotton in water, 
 dip it in vinegar, and wash it again. Compare with the untreated 
 cotton. How did the sodium hydroxide affect its strength? Com- 
 pare this with the effect of the acid in Ex. 276. 
 
 Ex. 278. Stretch a small piece of white cotton cloth on a frame 
 and dip it in a 30 per cent solution of sodium hydroxide for 15 minutes. 
 Wash it thoroughly and note the effect of the treatment on the strength 
 and luster of the cotton. Why was the cloth stretched on a frame? 
 What is cotton treated in this way called ? 
 
 Ex. 279. Examine fibers of linen under the microscope. Note the 
 absence of twist and the presence of "knots" at the junction of the 
 
398 APPLIED CHEMISTRY 
 
 cells. What is the source of linen ? What is meant by retting the flax ? 
 How does the strength of linen compare with cotton ? Which is more 
 resistant to alkalies and chlorine ? 
 
 Ex. 280. Burn some woolen cloth and note the odor. Place bits of 
 woolen cloth in a test tube and heat. Hold a piece of moist red litmus 
 paper in the escaping vapor. Result? Hold a piece of lead acetate 
 paper in the vapor. Result? Does wool contain nitrogen and sul- 
 phur ? What are the sources of wool for cloth making ? 
 
 Ex. 281. Examine fiber of wool under the microscope. Note the 
 saw-tooth appearance. Of what advantage is this structure ? What is 
 meant by shoddy ? Is shoddy as strong as the original woolen cloth ? 
 
 Ex. 282. Boil a piece of pure woolen cloth and a piece of mixed 
 wool and cotton in a 10 per cent solution of sodium hydroxide. What 
 happens ? How is it possible to distinguish between pure woolen goods 
 and mixed goods ? Try the experiment on goods from home. 
 
 Ex. 283. Examine fibers of silk under the microscope and compare 
 with wool. Heat some bits of silk in a test tube and test for ammonia 
 and sulphur. Results ? Compare with wool. 
 
 Ex. 284. Dip a piece of cotton cloth in a solution of alum. After 
 a few minutes take out the cotton, wring it out and dip it in a dilute 
 solution of ammonia water. Now dip this piece of cloth and an un- 
 treated piece into a solution of logwood and boil it. After a few min- 
 utes withdraw the two pieces of cloth and wash them thoroughly in 
 clear water. Is there any difference in the two pieces ? Which holds 
 the color better ? How do you explain this ? What is meant by a 
 mordant? (Note. If logwood is not available a strong solution of 
 litmus may be substituted with fairly good results.) 
 
 Ex. 285. Dip pieces of colored cotton cloth in a dilute solution of 
 bleaching powder. Transfer from this solution to a dilute solution of 
 hydrochloric acid. Note the effect on the color. Should bleaching 
 powder be used for wools or silks ? How are wools and silks usually 
 bleached? 
 
CHAPTER XLVII 
 PAINTS AND VARNISHES 
 
 447. ALL paints consist of two parts : (1) an opaque solid, 
 and (2) a liquid that holds the solid in suspension while the 
 paint is being spread on a surface, and which causes it to 
 adhere firmly to the substance that it covers. The solid is 
 called the pigment, and the liquid the vehicle. 
 
 448. Linseed Oil the Best Vehicle. The most commonly 
 used and the best vehicle for paint making is linseed oil, 
 which is made from flaxseed. The oil is extracted by press- 
 ing the ground seed. If the oil is extracted in the cold, it 
 is very light colored, but a more abundant yield of a 
 darker colored oil is obtained if the seeds are subjected to heat 
 while being pressed. Linseed oil, as has been shown (302), 
 absorbs oxygen from the air and is changed into a tough, 
 solid substance. This change takes place readily when the 
 oil is spread in a very thin layer. This property of linseed 
 oil causes it and the pigment to adhere closely to the surface 
 to which the paint is applied. The pigment fills the pores 
 that form in the film of oil and helps to cover the surface 
 more completely than would be done by the oil alone. 
 
 449. Boiled Oil and Driers. Linseed oil that has been 
 heated with lead oxide or the oxides of manganese will dry 
 more quickly than the raw oil. Such oil is called boiled oil. 
 The more rapid drying is probably due to the catalytic action 
 of the oxides absorbed by the oil in the process of boiling. 
 The paint can also be made to dry more quickly by adding 
 small quantities of so-called driers. These are substances 
 that absorb oxygen from the air and then give it off to the 
 oil, thus hastening the oxidation or drying of the oil itself. 
 
 399 
 
400 APPLIED CHEMISTRY 
 
 Turpentine is a substance of this kind, and is commonly 
 added to paint when quick drying is desired. 
 
 Japan driers are made by boiling a little oil with a large 
 amount of lead or manganese oxides, and dissolving the mix- 
 ture in turpentine. By adding a small quantity of this drier 
 to the paint it is made to dry more rapidly. Too much drier 
 is objectionable as any such substance really tends to make 
 the paint less durable. Much of what is sold as boiled oil 
 is merely raw linseed oil to which drier has been added. 
 
 450. Adulterated Linseed Oil. The comparatively high 
 price of linseed oil has led to its frequent adulteration. Such 
 materials as cottonseed oil or corn oil are substituted in part 
 or in whole for the linseed oil. These substitutes are not 
 drying oils, and paints made with them will not dry. As a 
 consequence such paints are not durable, especially when 
 exposed to the weather. Paints that remain sticky long after 
 application have been mixed with other than linseed oil. 
 The best test is to brush a thin layer on a pane of glass 
 and place it outdoors for forty-eight hours. If the oil has 
 not dried to a hard film with no stickiness, it is not true 
 linseed oil, and is not suitable for use in mixing paints. 
 
 451. Common Pigments. Those used to form the body of 
 paints are white lead (250) and zinc oxide (219). White lead 
 is the oldest of the white pigments and is still probably used 
 more than any other. It has good covering quality but has 
 the fault that it rubs off or chalks after a time. It also 
 darkens with age because of the formation of lead sulphide. 
 
 Zinc oxide does not cover so well as white lead but is more 
 durable and does not chalk or darken with age. Probably 
 the best white pigment is a mixture of white lead and zinc 
 oxide, which combines to a large extent the covering power 
 of the white lead and the durability of the zinc oxide. The 
 
PAINTS AND VARNISHES 401 
 
 highest grades of mixed paints are made from white lead, zinc 
 oxide, and pure linseed oil. Many substances are added to 
 both lead and zinc paints as adulterants; such as chalk, 
 barites, lead sulphate, kaolin, and a mixture of zinc sulphide 
 and barites known as lithophone. High-grade paints should 
 be free from such adulterants and from benzine or gasoline. 
 
 452. Colored Paints. These are made by adding some 
 colored pigment to the mixture of white lead and zinc oxide. 
 Some of the more common are yellow ocher and red ocher, 
 which are oxides of iron and are comparatively inexpen- 
 sive; chrome yellow, which is lead chromate; vermilion, 
 a sulphide of mercury ; Prussian blue ; Paris green ; chrome 
 green, and so on. Shades of gray are produced by adding 
 small quantities of lampblack to white paint. 
 
 453. Water Paints. These consist of a pigment suspended 
 in water and held in place by some cementing substance such 
 as glue or casein. These paints dry by evaporation. Most 
 of the water paints are unsuited to outside work, although 
 some of those made with casein have a fair degree of per- 
 manency when so used. Most of the kalsomines consist of 
 chalk and some tinting pigment suspended in a thin solution 
 of glue. Some of them, however, contain plaster of Paris, 
 which forms a hard coating as it dries. 
 
 Whitewash is slaked lime mixed with water. When the 
 mixture is spread on a surface the lime absorbs carbon dioxide 
 from the air and forms calcium carbonate. Ordinary white- 
 wash lasts only a short time when exposed to the weather. 
 The preparation which is given below, known as Government 
 whitewash, is fairly durable even for outdoor work. 
 
 454. Government Whitewash. Slake half a bushel of 
 lime in warm water and cover it during the process to keep 
 in the steam. Strain the liquid through a fine sieve or 
 
 EV. CHEM. 26 
 
402 APPLIED CHEMISTRY 
 
 strainer. Add a peck of salt previously dissolved in warm 
 water, three pounds of ground rice boiled to a thin paste and 
 stirred in boiling hot, a half-pound of powdered Spanish 
 whiting, and a pound of glue which has been previously dis- 
 solved over a slow fire. Then add five gallons of hot water, 
 stir well, and let it stand for a few days protected from 
 dust and dirt. It should be put on hot with small brushes. 
 One pint of the mixture will cover a square yard. 
 
 455. Varnishes are used to provide protecting coats that 
 are transparent and reveal the grain of the wood. As with 
 mixed paints, there is a great variation in the quality of the 
 varnishes on the market. A good varnish should stand 
 water, and should not " dust" when scratched. Two general 
 types of varnishes are oil varnishes and spirit varnishes. 
 
 The oil varnishes are made by melting a resin or gum and 
 dissolving it in hot linseed oil, and then thinning the mixture 
 to the proper consistency with turpentine. When made from 
 pure linseed oil and a good gum such as opal, amber, or 
 dammar, a varnish is produced that gives a tough, water- 
 resisting film. Cheaper furniture varnishes, consisting of 
 common rosin dissolved in oil, lack wearing quality. 
 
 Spirit varnishes are made by dissolving gums or resins in 
 denatured alcohol or wood alcohol. These dry by simple 
 evaporation of the solvent, and the gum is left unchanged 
 except that it has been spread out in a thin film. The most 
 common varnish of this kind is the well-known shellac. 
 Spirit varnishes are not so durable as the oil varnishes. 
 
 456. Enamel Paints. These are made by grinding pig- 
 ments in a good varnish instead of in linseed oil. The best 
 white enamel paints consist of zinc oxide ground in a dammar 
 varnish. Many of the enamel paints, however, are made 
 from cheap varnishes and inferior pigments and fillers. 
 
PAINTS AND VARNISHES 403 
 
 457. Black Varnishes. Varnishes used for coating iron are 
 prepared by dissolving coal tar, pitch, or asphaltum in tur- 
 pentine or benzine. They give excellent protecting surfaces 
 where the black color is not objectionable. A very thin 
 solution of these materials in benzine is often used as a stain 
 for wood. The creosote stain often used on shingles is a 
 coal-tar product, which preserves as well as stains the wood. 
 
 EXERCISES 
 
 Ex. 286. What is meant by the pigment in paints ? By the vehi- 
 cle? What is the best vehicle? How is linseed oil prepared? What 
 happens to it when exposed to the air ? What is meant by boiled oil ? 
 Why is the oil so prepared ? What is meant by a drier and how does it 
 act ? Why is turpentine used in paints ? What is Japan drier ? 
 
 Ex. 287. Obtain a sample of linseed oil (from home if possible) and 
 brush a little out into a very thin layer on a pane of glass. Examine 
 this at the end of 24 hours and 48 hours. Does the oil harden com- 
 pletely ? Is it suitable for paint making ? 
 
 Ex. 288. What are the two best pigments for paint making ? State 
 advantages of each. Why is a mixture of both most desirable ? How 
 are colored paints made ? 
 
 Ex. 289. Test a sample of paint from home for purity of the pig- 
 ments as follows: (1) Remove all the oil from a tablespoonful of the 
 solid sediment of the paint, by washing it several times by decantation 
 with gasoline. Spread the residue out to dry. (2) Boil a portion of 
 the dry material with strong acetic acid. A residue indicates barites 
 or other adulterants. (3) Test another portion on charcoal for lead 
 according to paragraph 252. (4) Test another portion for zinc accord- 
 ing to paragraph 221. Record the results of your test. 
 
 Ex. 290. Of what do water paints consist? What is whitewash? 
 Are water paints usually durable for outside work ? Try the Govern- 
 ment whitewash any place about the home where whitewash is used. 
 
 Ex.291. How are varnishes made ? What are the characteristics of 
 a good varnish ? What are spirit varnishes ? Compare the finish from 
 the two kinds of varnish. How are enamel paints made ? What is the 
 black varnish that is often used in coating iron ? 
 
CHAPTER XLVIII 
 CLEANING MATERIALS 
 
 458. THE operations of cleaning involve both physical and 
 chemical processes. Dirt can sometimes be removed by 
 means of brushing, shaking, or simple agitation under water. 
 The dirt is first loosened by friction and then carried away by 
 currents of air or water. It is usually held in place, how- 
 ever, by particles of grease or some sugary or gummy ma- 
 terial and cannot be removed by strictly mechanical means. 
 Sugary spots may be removed by warm water alone, but 
 when the dirt is held by a film of grease, some substance 
 must be used that will remove the grease. Soap is ordi- 
 narily employed to accomplish this end. 
 
 459. Soaps. It has been explained (303) that soaps are 
 the sodium or potassium salts of the fatty acids, and are 
 made by boiling fats or oils with the carbonates or hydroxides 
 of sodium or potassium. Most of the soaps on the market 
 are sodium 'soaps and belong to the class known as hard 
 soaps. Soft soaps are made with potassium compounds but 
 are not commonly found on the market. About the only 
 familiar example of soft soap is the old-fashioned homemade 
 soap which is manufactured from waste fats and lye. 
 
 The cleaning power of soap is to some extent due to the 
 fact that it partially dissociates when dissolved in water, 
 liberating a little free alkali which acts upon the grease to be 
 removed. Probably its most important action is its power 
 to emulsify the grease of the dirt spot. Dirt and small 
 
 404 
 
CLEANING MATERIALS 405 
 
 particles of the emulsified fat become thoroughly mixed 
 with the suds, and upon rinsing are removed with the soap. 
 
 460. Pure Soap. Such a soap should contain no excess 
 of alkali or of unchanged fat. A good test for free alkali is 
 made by dropping a little phenolphthalein indicator on the 
 freshly cut surface of a bar of soap. A coloration of the 
 indicator shows the presence of free alkali. Unsaponified 
 fat can be determined by drying a portion of the soap in 
 the oven and then extracting the dry material with gasoline. 
 If the gasoline leaves a greasy film upon evaporation, the 
 presence of unchanged fat is indicated. 
 
 Toilet soaps especially should contain no free alkali, as the 
 latter is injurious to the skin. Even in laundry soaps any 
 large amount of free alkali is objectionable if the soaps are to 
 be used for washing woolen or silk goods or any kind of 
 colored material. Strong perfumes are so often used to 
 cover the odor of the lye and other objectionable materials 
 that it is advisable in general to avoid all highly scented soaps. 
 
 461. Hard Water Wastes Soap. When soap is used in 
 hard water a scum appears on the surface of the water. 
 This is due to the fact that the calcium and magnesium salts 
 in the hard water react with the soap, forming calcium and 
 magnesium salts of the fatty acids of the soap. These 
 calcium and magnesium salts are insoluble in water and are 
 so light that they float. As these salts are insoluble they 
 have no emulsifying or cleaning power; hence the amount 
 of soap that reacts with calcium and magnesium is wasted. 
 Soap does not begin to lather until all the lime and mag- 
 nesia have been removed from the water. In this case soap 
 itself softens the water before it begins the real cleaning 
 process ; but it is an expensive method of softening water. 
 
 462. Foreign Ingredients in Soaps. Many of the soaps 
 
406 APPLIED CHEMISTRY 
 
 found on the market are adulterated. Washing soda, or 
 sodium carbonate, in excessive quantities is present in many 
 laundry soaps. The soaps especially recommended for hard 
 water usually contain a large amount of sodium carbonate. 
 While such a soap may not be objectionable for use on cotton 
 goods in hard water, washing soda bought in this way is very 
 expensive. Another common adulterant of laundry soap is 
 sodium silicate, or water glass. This substance has some 
 cleansing power, but its use results in an inferior soap. A 
 few soaps contain a small percentage of borax. 
 
 Common rosin when boiled with an alkali forms a sub- 
 stance resembling soap. The yellow laundry soaps are 
 usually made from a mixture of rosin and fats and are in- 
 ferior to soaps made wholly from fats. Rosin soaps are 
 not particularly objectionable for washing cotton goods, but 
 with woolens they are likely to deposit rosin in the fiber and 
 make the goods harsh to the touch. 
 
 Some soaps for use in cold water contain naphtha or 
 kerosene. These substances are added for the specific 
 purpose of assisting in dissolving the grease so that heat will 
 not be necessary, and are not, therefore, to be considered 
 as adulterants. Soaps are also frequently adulterated with 
 substances of no cleaning value called fillers, which are 
 added solejy to increase the weight of the soap. Sodium 
 sulphate, gypsum, whiting, chalk, and almost anything else 
 that is cheap and bulky are used as fillers. 
 
 Water in excess of 25 per cent is also considered an adulter- 
 ant. Too much water makes the soap soft so that it dis- 
 solves rapidly. A dry soap does not waste so readily; 
 hence it is economy to buy laundry soap in quantities, 
 unwrap the bars, and pile them loosely, so that the soap can 
 dry as thoroughly as possible before being used. 
 
CLEANING MATERIALS 407 
 
 463. Washing Soda and Other Alkalies. Where hard 
 water must be employed, a judicious use of sodium carbonate 
 results in a saving of soap. Just enough soda should be 
 added to precipitate the lime and magnesia in the water. 
 The soda should first be dissolved in a small quantity of 
 water and this solution should be gradually added to the laun- 
 dry water, care being taken to avoid any great excess. Caus- 
 tic soda (soda lye) is sometimes used for the same purpose ; 
 but its use requires more care than ordinary washing soda. 
 The use of either substance with silk or woolen goods is at- 
 tended with risk, and colored goods of all kinds are likely to 
 be injured by a slight excess of alkali in the wash water. 
 Borax is occasionally used when a milder alkali than washing 
 soda is needed, but it is much more expensive than soda. 
 
 Ammonia water is also used to soften hard water. It is 
 the safest alkali to use in many cases because it evapo- 
 rates very rapidly and does not remain in contact with the 
 goods long enough to injure the fiber. The alkalies will 
 destroy any materials made from oils or resins, hence 
 strongly alkaline solutions should never be used on paints 
 or varnishes. 
 
 464. Soap Powders and Scouring Soaps. Many of the 
 washing powders on the market are nothing but washing 
 soda. Others contain a small percentage of soap shavings 
 mixed with a large amount of soda. It is probably more 
 economical to buy the washing soda ahd soap separately 
 than to purchase them in the form of washing powders. 
 
 Scouring soaps and powders consist for the most part of a 
 small amount of soap mixed with washing soda and some 
 scouring powder, such as whiting, chalk, powdered pumice, 
 fine sand, or infusorial earth. The scouring material should 
 not be so coarse as to scratch the article to be cleaned. 
 
408 
 
 APPLIED CHEMISTRY 
 
 465. Solvents for Fats. When a grease spot occurs in a 
 fabric which for any reason cannot be washed, it is necessary 
 to use some substances that will dissolve the grease and carry it 
 away. The most commonly used materials are gasoline and 
 benzine. These liquids dissolve all the fats and are largely 
 used in what is known as the dry-cleaning process. To get 
 the best results some absorbing material must be placed 
 beneath the fabric to be cleaned so that the grease can be 
 washed through by the gasoline or other solvent. To add a 
 little gasoline and rub the spot, merely spreads the grease into 
 a larger and thinner film. Sometimes the goods are rinsed 
 
 in several changes of 
 gasoline to remove the 
 grease. 
 
 Ordinary ether is 
 even better than gaso- 
 line for removing fats ; 
 but its high cost pre- 
 vents its use except for 
 certain special pur- 
 poses. All the solvents 
 ordinarily used for re- 
 moving grease from 
 clothing are highly in- 
 flammable, and their 
 vapors make explosive 
 mixtures with air. Great care should be exercised in using 
 any of these materials, and they should never be used in a 
 room in which there is a fire. Whenever possible the cleaning 
 should be done out of doors. 
 
 A comparatively- new substance known as carbon tet- 
 rachloride (CClj) is sometimes used to remove grease 
 
 FIG. 182. Cleaning clothing with gasoline. 
 
CLEANING MATERIALS 409 
 
 from fabrics. It has the advantage of not being in- 
 flammable. 
 
 Both gasoline and kerosene dissolve the calcium and 
 magnesium soaps. Probably for this reason it is advan- 
 tageous to place a little kerosene in the boiler in which cloth- 
 ing is boiled. For the same reason either substance is useful 
 in cleaning bath tubs and basins where hard water is used. 
 
 466. Spots and Stains. These come from such a variety 
 of causes that no remedy can be suggested unless the cause 
 of the stain is known. At the best, however, it is practically 
 impossible to remove stains from delicately colored fabrics 
 without destroying the color of the dye as well. 
 
 Fruit juices and other acid substances frequently discolor 
 dyed materials, especially the blues. The color can some- 
 times be restored by weak ammonia water if applied in time. 
 Many fruit stains can be removed by hot water when fresh 
 but are resistant to treatment when old. 
 
 Alcohol will remove grass stains (chlorophyll), and spots 
 of varnish, and some paints. Consequently care should 
 be exercised to avoid spilling alcohol, perfume, or other 
 substance containing alcohol on any varnish finished 
 surface. 
 
 Ink was formerly always made from iron tannate. This 
 compound is soluble in weak acids, and can be removed, 
 when not too old, by lemon juice and salt, oxalic acid, or 
 even very dilute hydrochloric acid. The acid substance 
 should be added cautiously and the material should be washed 
 as soon as the color of the ink spot disappears. Many of the 
 inks now on the market are made from aniline dyes and are 
 not affected by the weak acids. For them there is no method 
 of removal that will not affect the dye of the cloth as welL 
 White goods can often be bleached to remove such ink spots. 
 
410 APPLIED CHEMISTRY 
 
 EXERCISES 
 
 Ex. 292. Review Exercises 176 and 177. What is the chemical 
 composition of a soap ? How do soaps clean ? 
 
 Ex. 293. Test several samples of both white and yellow soaps for 
 free alkali by putting a drop of phenolphthalein indicator on the freshly 
 cut surface of the soaps. Which show free alkali ? Would they make 
 good toilet soaps ? Were any of the soaps especially recommended for 
 hard water ? Why should strongly perfumed soaps be avoided ? 
 
 Ex. 294. Do you use hard or soft water at home for washing ? Ex- 
 plain how hard water wastes soap. What is the curd that floats on the 
 top of hard water when soap is used in it ? 
 
 Ex. 295. Name some of the foreign ingredients sometimes found in 
 soap. Why is it objectionable to have large quantities of sodium car- 
 bonate in soap ? Why is rosin objectionable ? What is meant by fillers 
 in soap ? What are naphtha soaps ? 
 
 Ex. 296. Dissolve a small piece of scouring soap in hot water. 
 What is the nature of the residue ? On a sample of any washing pow- 
 der pour a little hydrochloric acid. Is sodium carbonate present ? 
 
 Ex. 297. Explain the softening action of sodium carbonate on hard 
 water. Why should it be used cautiously with silks and wools ? What 
 advantage has ammonia water for use on woolens ? Why should strong 
 alkalies be avoided on paints and varnishes? 
 
 Ex. 298. What kinds of spots can be removed by gasoline or ether ? 
 Upon what does their action depend ? How are the best results ob- 
 tained? What precautions are necessary in using gasoline or ether? 
 
 Ex. 299. Make various spots on cotton or woolen goods, or use 
 clothing already spotted, and attempt to remove the spots by the various 
 methods mentioned in this chapter. 
 
CHAPTER XLIX 
 
 INSECTICIDES AND FUNGICIDES 
 
 467. Losses due to Insects. It has been estimated that 
 ten per cent of the value of farm crops is lost through the 
 destruction caused by injurious insects, and that this loss 
 amounts to four times 
 that due to all destruc- 
 tion of property by fire. 
 The farmer and the gar- 
 dener, therefore, are in- 
 terested in the .methods 
 of controlling injurious 
 insects. These insects 
 are divided into two 
 general classes : those 
 that eat the tissues of 
 the plant, and those 
 that suck out the plant 
 juices and so injure the 
 plant. Insects that bite 
 may be killed by cover- 
 ing the plant with a 
 so-called stomachic 
 poison, which the insect 
 swallows. The insects FlG ' 183 ' ~" Spraying trees> 
 
 which merely suck the sap cannot be killed by the stomachic 
 poison but are destroyed by contact poisons, which cause 
 death by their caustic action on the body of the insect. 
 
 411 
 
412 APPLIED CHEMISTRY 
 
 468. Stomachic Poisons. These poisons usually contain 
 arsenic in some form. The oldest of these is Paris green (260), 
 which is a compound of copper with arsenious acid and 
 acetic acid. From one half to one pound of Paris green is 
 used to fifty gallons of water. Paris green even in this 
 dilute solution will sometimes scorch the leaves, and to pre- 
 vent this action two pounds of slaked lime are added. 
 
 Ar senate of lead (251) is rapidly replacing Paris green as 
 an insecticide. It is purchased either in the form of a paste 
 or a powder and is used at the rate of from 2 to 4 pounds in 
 50 gallons of water. It is more adhesive than Paris green 
 and does not injure the foliage. 
 
 Powdered hellebore is used to a limited extent by garden- 
 ers, especially for ornamental plants. The powder is mixed 
 with hot water and then diluted and sprayed on the plants. 
 
 469. Contact Poisons. The first used of the contact 
 poisons was kerosene emulsion. The kerosene is vigorously 
 agitated with soapsuds until a jellylike emulsion is formed 
 which can then be diluted with water without separating. 
 It kills the insect by inclosing its body with a film of oil. If 
 properly made, the emulsion is not injurious to the foliage. 
 
 470. Lime sulphur is probably used more than any other 
 contact poison. Some of the insects, the San Jose scale for 
 example, have the power of covering their bodies with a 
 protecting scale and consequently a penetrating spray 
 mixture is necessary to reach them. Lime-sulphur mixture 
 seems to give the best results with these insects. It is made 
 by boiling together lime and flowers of sulphur. The lime 
 and sulphur unite to form the polysulphides of calcium, 
 probably largely CaS 4 and CaS 5 . When exposed to the air 
 the polysulphides decompose, setting free sulphur. The 
 insecticidal action of this spraying mixture is due partly to 
 
INSECTICIDES AND FUNGICIDES 413 
 
 its caustic action on the insect, and partly to the poisonous 
 effect of the nascent sulphur which is liberated. Lime- 
 sulphur solution is now made commercially on a large scale 
 and is not so generally manufactured on the farm as formerly. 
 To kill the scale a strong solution is used when the trees are 
 dormant. After the leaves appear, a weak solution is used 
 for certain other insects and diseases. 
 
 471. Whale Oil Soap. This and other soaps made from 
 fish oils are frequently used to destroy scale insects. The 
 soap is dissolved in boiling water at the rate of two pounds 
 to the gallon of water and is applied while hot. It is used 
 principally for the winter treatment of scale-infected trees. 
 
 Common laundry soap dissolved in water at the rate of 
 one bar of soap to two bucketfuls of water makes an effective 
 contact insecticide for the small garden. A white soap free 
 from rosin is to be preferred. 
 
 472. Tobacco is sometimes used for the destruction of 
 insects on house plants. The stems or other refuse parts of 
 the tobacco plant are steeped in water and the solution is 
 sprayed on the plant. Sometimes in place of this decoction 
 of tobacco a solution of nicotine sulphate is used. -It will be re- 
 membered that tobacco contains an alkaloid known as nico- 
 tine (326). The salt formed by this alkaloid and sulphuric 
 acid is the basis of such insecticides as Black Leaf-40. It 
 is used especially to kill the aphis or plant louse. 
 
 473. Pyrethrum Powder. This powder, also known as 
 Buhach and Persian insect powder, is composed of the pul- 
 verized flower heads of certain plants of the genus pyrethrum. 
 It is a valuable insecticide for use in a small way when fresh, 
 but soon loses its strength, especially if it is exposed to the 
 air. It is used by dusting it on the plant or by steeping it 
 in water and using the resulting liquid. The fumes of the 
 
414 APPLIED CHEMISTRY 
 
 burning powder are useful also in destroying insects in a 
 confined space. 
 
 474. Gaseous Insecticides. Hydrocyanic acid (209) is 
 sometimes used as an insecticide in greenhouses and in the 
 orange groves of California. It is used in greenhouses in the 
 following manner : the operator places dilute sulphuric acid 
 in suitable vessels and then drops into each vessel a quantity 
 of potassium cyanide wrapped in paper. He immediately 
 steps outside and closes the house tightly. After a few hours 
 the house is opened from the outside and thoroughly ven- 
 tilated before any one ventures inside. In the orange groves 
 each tree is covered with a tent for fumigation purposes. 
 Hydrocyanic gas is a deadly poison and should be handled 
 only by persons skilled in its use. 
 
 475. Carbon Bisulphide (110). This is used for killing 
 weevils and other insects in stored grains. The liquid is 
 placed in dishes at a number of places on the surface of 
 the grain, about a teaspoonful being used for each cubic foot 
 of space. The carbon bisulphide vaporizes, and the vapor, 
 which is heavier than air, settles down through the grain. 
 Carbon bisulphide is used also to exterminate rodents (110). 
 It is inflammable and should not be used near a flame. 
 
 476. Sheep Dips and Fly Repellents. The materials 
 used in dipping sheep for the purpose of killing their insect 
 parasites are largely coal-tar products, cresol being the 
 substance most commonly used. Light coal-tar oils and 
 other coal-tar products are sometimes sprayed on cattle to 
 repel flies. These repellents should be made of materials 
 which, when they evaporate, leave no sticky or gummy sub- 
 stance on the hair of the cattle. 
 
 477. Insecticides for the Household. The common 
 method of control for the common house fly is by means of 
 
INSECTICIDES AND FUNGICIDES 415 
 
 some kind of fly paper. The sticky fly papers are coated 
 with a mixture of common rosin and castor oil. The ordi- 
 nary poison fly paper is impregnated with a dilute solution 
 of sodium arsenite. Care should be exercised in using it, 
 since children have been known to be poisoned by drinking 
 the sweetened water in which the paper is placed. 
 
 A two per cent solution of formaldehyde (a teaspoonful 
 of formalin to a cupful of water) is said to be as effective in 
 killing flies as the poison paper and has the advantage of not 
 being poisonous to human beings. A little honey or milk is 
 added to the solution to attract the flies. If many flies are 
 present, they may be killed by burning pyrethrum powder 
 in the tightly closed room. 
 
 The favorite breeding places of flies are the garbage can, 
 the manure pile, and other places where decomposing or- 
 ganic matter is found. Such materials should, when possible, 
 be so handled as to prevent the flies from having access to 
 them. It is said that hellebore, borax, or acid phosphate 
 scattered on manure piles prevents the breeding of flies. 
 
 Sodium fluoride, NaF, is recommended for the extermina- 
 tion of cockroaches and red ants. It is scattered over the 
 tables, sinks, or pantry shelves where these insects are found. 
 
 No insects cause the housewife more worry than the 
 clothes moth which is so destructive to woolens and furs 
 especially. The moth balls so commonly used consist of 
 naphthalene (Ci H 8 ), a substance prep'ared from coal tar. 
 It repels the moth and prevents it from laying the eggs on 
 the clothing. If the eggs have already been deposited, the 
 naphthalene has no value. The caterpillar which hatches 
 from the eggs and does the real damage may be destroyed 
 by dusting the garment heavily with pyrethrum powder. 
 Sometimes the infected clothing is placed in a tight box and 
 
416 APPLIED CHEMISTRY 
 
 treated with carbon bisulphide as described for the treat- 
 ment of grains (475). In the cities furs are sometimes 
 placed in cold storage during the summer at a temperature 
 so low that the eggs cannot hatch. 
 
 The common bedbug is destroyed by applying gasoline 
 freely to every crack and crevice in which it is possible for 
 the bug to hide. Repeated treatments of this kind will 
 effectively control this pest. Fleas on dogs and other ani- 
 mals may be exterminated by the free use of pyrethrum 
 powder. This powder is not poisonous to the higher animals, 
 and its use, therefore, is attended with no danger. 
 
 Old houses occasionally become so overrun with insect 
 pests that all ordinary methods fail. In such cases a resort 
 to fumigation with hydrocyanic acid gas is justified. The 
 same general method as that described for fumigating green- 
 houses is used. This gas destroys all animal life which is in 
 the house, and is such a deadly poison that the greatest 
 precaution should be observed in using it. 
 
 Fungicides. Plants are often injured by fungi that grow 
 parasitically upon them. Some of these disease-producing 
 fungi can be destroyed by spraying with a proper fungicide. 
 
 478. Bordeaux Mixture. Probably the best known of the 
 fungicides is made by mixing a solution of copper sul- 
 phate with milk of lime (259) and diluting the mixture with 
 water. It is the most common spray used on apple trees. 
 As trees are attacked by insects at the time that they are 
 suffering from fungus diseases, it is customary to add ar- 
 senate of lead or Paris green to the Bordeaux mixture so as 
 to make the one mixture both an insecticide and fungicide. 
 
 479. Lime sulphur has marked fungicidal properties, and 
 a dilute solution of lime sulphur is used in place of, or in 
 addition to, the Bordeaux mixture for summer spraying. 
 
INSECTICIDES AND FUNGICIDES 
 
 417 
 
 Arsenate of lead is sometimes mixed with the lime-sulphur 
 mixture. 
 
 480. Formaldehyde, or formalin, is commonly used to 
 kill the smut fungus on oats and other grains. The com- 
 mercial 40 per cent solution of formaldehyde is used at the 
 rate of one pint to 20 gallons of water. Seeds are immersed 
 in this solution for 10 minutes and then spread out to dry. 
 
 FIG. 184. Treating seed potatoes with formalin to prevent scab. 
 
 A new method for treating oats for smut, which avoids the 
 necessity of drying the seeds, has recently been reported by 
 the New York State College of Agriculture. This method 
 in brief is as follows : one pint of the 40 per cent solution of 
 formaldehyde is diluted with one pint of water and placed in 
 a quart hand sprayer. The oats are placed on a clean barn 
 floor or on a tight wagon box. While the oats are being 
 shoveled from one pile to /another each shovelful is sprayed 
 with the solution, giving one movement of the handle for each 
 shovelful. After the oats are all treated in this way, they are 
 EV. CHBM. 27 
 
418 APPLIED CHEMISTRY 
 
 piled in a heap and covered with blankets, canvas, or grain 
 sacks which have been sprayed inside and out with the 
 solution. They are allowed to stand for at least five hours, 
 after which they may be bagged and drilled. The above 
 amount of solution is sufficient to treat 50 bushels of oats. 
 
 Formaldehyde is also used in a similar way to kill the scab 
 fungus on the seed potatoes (Fig. 184), as is also a weak 
 solution of corrosive sublimate. More or less complete 
 descriptions of all these insecticides and fungicides are pub- 
 lished by many of the state experiment stations and by the 
 United States Department of Agriculture. 
 
 481. Bacterial Diseases. The fungus diseases that are 
 readily affected by sprays are those which grow on the surface 
 of leaves and stems. Many of the diseases of plants are 
 caused by bacteria and are so deep-seated as to be beyond 
 the reach of the spray materials. Some of these can be 
 eradicated by careful pruning. Still other diseases have, 
 thus far, defied all treatments, and when they appear the 
 tree must be destroyed to check the spread of the disease. 
 
 EXERCISES 
 
 Ex. 300. To what extent are crops injured by insects ? Into what 
 two classes may these insects be divided according to their manner of 
 feeding ? What two classes of poisons are necessary to destroy them ? 
 What is the more common constituent of the stomachic poisons ? What 
 are the two more important arsenic preparations used as insecticides? 
 Why should lime always be used with Paris green ? 
 
 Ex. 301. How do contact poisons act ? How is kerosene emulsion 
 made? What is a good contact poison for a small garden? What 
 tobacco preparations are used as insecticides? What is pyrethrum 
 powder and how is it used ? By what other names is it known ? What 
 methods can you suggest for controlling the house fly ? How can you 
 rid the house of cockroaches or ants ? How can you protect clothing 
 from moths ? 
 
INSECTICIDES AND FUNGICIDES 419 
 
 Ex. 302. Slake 25 grams of lime and add to 200 cc. of water. Add 
 50 grams of flowers of sulphur. Heat gradually to boiling, with constant 
 stirring, and boil half an hour. Allow to settle and decant the clear 
 liquid. What is the color of the liquid ? What is this substance called ? 
 Of what does it probably consist ? To what are its insecticidal proper- 
 ties due ? At what season is it used to kill the scales ? 
 
 Ex. 303. Explain the use of hydrocyanic acid as an insecticide. 
 Why is it so Dangerous to work with it ? How is it used in the orange 
 groves? Wtyat is carbon bisulphide? Explain its use to kill weevil. 
 Review Ex. 77. Why should carbon bisulphide never be used near 
 afire? 
 
 Ex. 304. Dissolve half a pound of copper sulphate in a quart of hot 
 water. Slake half a pound of lime in a quart of water. Strain the 
 milk of the lime through a cheesecloth. Pour the copper solution into 
 the limewater with constant stirring. What is this mixture called? 
 For what is it used ? Why should the copper sulphate solution never 
 be put into an iron vessel ? Read the bulletins for a description of the 
 method of making Bordeaux solution on a large scale. What is meant 
 by a 4-4-50 Bordeaux mixture ? 
 
 Ex. 305. Try an experiment in your locality by treating some oats 
 seed for smut according to paragraph 480 (formaldehyde). Plant this 
 seed on a plot adjacent to one on which untreated seed is used and note 
 results at harvest time. Send to your Experiment Station for bulletins 
 on treatment of oats for smut, and of potatoes for scab. 
 
PART III 
 
 SOILS AND FERTILIZERS 
 
 CHAPTER L 
 SOIL FORMATION 
 
 482. Soil. If soil is examined with the aid of a micro- 
 scope, it is found to consist of particles of rock coated with a 
 dark substance, which has been derived from the decomposi- 
 tion of organic matter. There is also present more or less 
 vegetable matter consisting of fine roots and other parts of 
 plants. The rock particles vary from stones of consider- 
 able size to grains of clay that are less than one five-thou- 
 sandth of an inch in diameter. Every one is so familiar 
 with the existing soil that it is hard to realize that nature 
 required ages to form it and that numerous agencies con- 
 tributed to the process of soil formation. 
 
 483. Weathering of Rocks. All soils have been formed 
 by the decay or weathering of solid rock. One agency in 
 the formation of the soil is change of temperature. A rock 
 like granite, for instance, consists of different minerals 
 cemented together. These minerals expand and contract 
 at different rates when heated or cooled, and the result 
 is that changes in temperature split the minerals apart. 
 Indeed, even a mass of one kind of material is disintegrated 
 by heat if the changes of temperature take place suddenly 
 so that the surface and the interior of the mass are unevenly 
 heated. The surface of a plate or of a piece of crockery, 
 
 420 
 
SOIL FORMATION 
 
 421 
 
 which has been used repeatedly in the oven, becomes covered 
 with fine cracks caused by the uneven heating and cooling. 
 The same thing happens in the case of some of the soil- 
 forming recks. More- 
 over, rocks are more 
 or less porous and 
 absorb water during 
 the rains. In cold 
 weather the water 
 freezes and expands 
 with great force and 
 tends to break the 
 rocks into pieces (6). 
 
 484. Running water 
 is an important agency 
 in the weathering of 
 rock. The water al- 
 ways carries some rock 
 particles, and these 
 rubbing upon the bed 
 of the stream grind 
 the stone to powder, 
 which is carried away 
 
 and deposited somewhere to form a soil. The more rapid 
 the stream the greater its wearing effect. 
 
 485. Glaciers help to grind the rocks to powder. The 
 action of the glaciers in Greenland, Alaska, and other 
 countries, which may be studied at the present time, illus- 
 trates what happened in past geologic ages. Many thousand 
 years ago a large area of the northern part of North America 
 was covered with an immense glacier that pushed its way 
 slowly down from northern Canada. As it moved south- 
 
 FlG. 185. The disintegration of rocks by 
 heat, cold, and frost. 
 
422 
 
 SOILS AND FERTILIZERS 
 
 ward it carried with it large quantities of rocks, grinding 
 them against one another until they were reduced to parti- 
 cles of varying degrees of fineness. Such great force had 
 
 this mass of ice with 
 the rocks imbedded in 
 it that it planed off 
 the tops of the hills 
 and carried the debris 
 with it to the south. 
 Later, when the climate 
 became warmer, the 
 ice melted, and this 
 rock material remained 
 
 FIG. 186. The formation and transportation behind to become a 
 
 part of the soil. In 
 
 some sections large masses of this material were left as long 
 ridges called moraines. 
 
 486. Action of Winds. In some parts of the world 
 winds have played an important part in soil formation. 
 Wind acts chiefly in 
 transporting materials ; 
 but in localities where 
 it blows with great 
 violence it gathers up 
 and sweeps along even 
 coarse sand which, 
 striking against rocks, 
 slowly wears them 
 away and is itself 
 made finer. In the western part of this country may be 
 seen instances of rock carving due to wind-driven sand 
 (Fig. 187). 
 
 FIG. 187. Peculiar rock forms carved by the 
 action of wind and sand. 
 
SOIL FORMATION 
 
 423 
 
 487. Chemical Weathering. Chemical changes in rocks 
 take place at the same time that rocks undergo mechanical 
 weathering, or pulverization. While the original rocks 
 contain all the mineral elements required by the plant, 
 these elements are present in unavailable forms. Such 
 rocks as the granites are extremely insoluble. The rains 
 that fall on these rocks contain carbon dioxide in solution, 
 and the continued action of this weak acid results in a par- 
 tial decomposition of the rock and a change of some of the 
 material into soluble compounds. In this way some of the 
 mineral matter finally becomes available as plant food. 
 
 488. Plants and Soil Formation. Plants play an im- 
 portant part in soil formation. The roots act both me- 
 chanically and chem- 
 ically. Nearly every 
 
 one has seen examples 
 
 of the enormous force 
 
 exerted by plant roots 
 
 in breaking apart rocks 
 
 (Fig. 188), when the 
 
 plant gets started in a 
 
 crevice or fissure. The 
 
 same mechanical action 
 
 is doubtless exerted by 
 
 the roots on the rocks underlying some soils. The roots also 
 
 secrete an acid substance, which acts' on the rocks with 
 
 which they come in contact ; and when the plants die and 
 
 the roots decay they leave in the soil numerous little channels 
 
 which allow the passage of air and of water laden with 
 
 carbonic acid. 
 
 489. Decaying organic matter produces humus, and 
 this substance in its turn becomes an important factor in 
 
 FlG. 188. Growing roots of tree assisting in 
 soil formation. 
 
424 
 
 SOILS AND FERTILIZERS 
 
 FIG. 189. Decaying organic matter assists 
 in soil formation. 
 
 soil formation. The humus increases the power of the soil 
 to retain water and to supply it to the plant ; and since all 
 the chemical changes by which plant food is made avail- 
 able take place more readily in the presence of sufficient 
 
 moisture, it will be seen 
 that this moisture- 
 holding power of humus 
 is a very important fac- 
 tor in soil fertility. 
 During the decay of 
 the organic matter, car- 
 bonic acid and other 
 acid substances are pro- 
 duced, and these help to 
 dissolve the mineral in- 
 gredients of the soil and 
 change them into substances that can be absorbed by plants. 
 
 490. Legumes in Soil Building. Plants belonging to 
 the clover family, the so-called leguminous plants, through 
 the bacteria that grow in the nodules or tubercles on their 
 roots, are able to use the free nitrogen of the air as a source 
 of food supply. When these plants die and become incor- 
 porated with the soil, the nitrogen which they have fixed 
 becomes a part of the soil and is made available to suc- 
 ceeding plants. It has been estimated that from 50 to 150 
 pounds of nitrogen to the acre may be fixed in this way in 
 a year. This power of the leguminous plants to accumulate 
 nitrogen is probably nature's most important method of in- 
 creasing the nitrogen content of the soil (168). 
 
 491. Animal Life in the Soil. In addition to the processes 
 described above, the action of the earthworms and other 
 forms of animal life found in the soil should be mentioned. 
 
SOIL FORMATION 425 
 
 These organisms are supposed by some authorities to play 
 a very important part in the working over of the soil and 
 in its preparation for plant growth. 
 
 EXERCISES 
 
 Ex. 306. Examine a sample of soil under a magnifying glass or 
 a microscope. What material can you distinguish in the soil? What 
 can you say about the sizes of the rock particles ? 
 
 Ex. 307. What is meant by the weathering of rock ? Heat and 
 cool a piece of granite repeatedly and note whether any change takes 
 place. Heat a piece of granite in a flame and drop it into cold water. 
 Does the sudden change of temperature affect the granite ? Notice a 
 plate at home which has been repeatedly heated in the oven. What 
 causes the cracks on the surface? Explain how heat and cold help 
 to pulverize the rock. 
 
 Ex. 308. Recall Ex. 5. What can you say about the expansive 
 force of freezing water? In what way does it help in soil formation? 
 
 Ex. 309. Explain how running water helps in pulverizing the 
 rocks. Do slow or rapid streams grind the rocks more readily? How 
 do the streams form their valleys? What becomes of the materials 
 which are ground to powder ? 
 
 Ex. 310. Explain the action of glaciers in forming soils. What 
 part of North America was covered by the great glacier? What 
 effect did the glacier have on the topography of the country? What 
 is a moraine? Did the glacier cover your locality? If so, what evi- 
 dence of that fact can you point out? Explain the action of winds in 
 rock pulverization. 
 
 Ex. *311. Explain how the insoluble silicates are made more 
 soluble during soil formation. What is the original source of the nitro- 
 gen in soils ? What can you say of the first plants which grew on the 
 newly-formed soils? In what ways is organic matter important in 
 soil formation ? How do the roots assist in disintegration of the rocks ? 
 What is the chief function of the legumes in building soils ? 
 
 Ex. 312. How do earthworms affect the formation of soils? Can 
 you find lichens growing on any of the rocks in your vicinity? What 
 is the appearance of the rock under the lichen ? How do you explain 
 this appearance? 
 
CHAPTER LI 
 
 KINDS OF SOILS 
 
 492. Physical Make-up of Soils. From the last chapter 
 it will be seen that the completed soil consists of rock parti- 
 cles mixed with decaying vegetable matter, the decomposing 
 remains of animals, and the various substances formed by 
 chemical action from the rocks and organic matter. The 
 rock particles are classified according to their size into 
 gravel, sand, silt, and clay. Gravel is subdivided into 
 coarse and fine gravel, and at least four grades of sand are 
 recognized : coarse, medium, fine, and very fine. Silt also 
 is divided into two classes : silt and fine silt. 
 
 The individual rock particles of clay are the smallest 
 recognized by the soil physicist. They are so small that 
 they cannot be distinguished by the naked eye, nor, indeed, 
 can they be felt between the fingers. In other words the 
 clay is entirely without grit, and when it is rubbed between 
 the fingers only the smooth mass of clay can be felt, the 
 individual particles being indistinguishable. As, clays 
 are very adhesive when moist, they adhere to tillage imple- 
 ments. Moreover, they absorb large amounts of water; 
 and yet the individual particles lie so close together that 
 water poured upon the surface of a clay often remains there 
 a long time, soaking into it with extreme slowness. Silt 
 is somewhat coarser than clay and the various grades of 
 sand are still coarser. The gravels include the largest 
 particles that are recognized as belonging to a true soil. 
 
 425 
 
KINDS OF SOILS 
 
 427 
 
 493 . Classification of Soils. Soils are classified in two ways : 
 (1) as to the method of their formation, and (2) as to their 
 composition. According to formation, soils are divided into 
 sedentary soils, or those that were formed where they now 
 exist ; and transported soils. Sedentary soils are subdivided 
 into residual and cumulose soils. Transported soils include 
 alluvial, colluvial, drift, and ceolian soils. According to 
 composition, soils are classified into clay, sand, loam, and 
 peat soils. 
 
 494. Residual soils, which have been made from the decay 
 of the rocks on which they lie (Fig. 190), partake more or 
 less of the composition of the underlying rocks. They have 
 usually lost considerable of their soluble constituents through 
 
 RESIDUAL 
 ^ 
 
 SSSSS'-S^ 
 
 .hiehrr*^^ ?^%* 
 
 FIG. 190. The formation of residual, colluvial, and alluvial soils. 
 
 the solvent action of rains. These soils are not generally 
 very deep, the underlying rock being comparatively close to 
 the surface. Residual soils may be fertile or not, their 
 degree of fertility depending upon the kind of rock from 
 which they were formed. 
 
 495. Cumulose soils are those formed in swamps and 
 marshes. They consist largely of organic matter which 
 has come from the partial decay of the marsh plants. They 
 
428 
 
 SOILS AND FERTILIZERS 
 
 FIG. 191. The formation of cumulose soil. 
 
 contain also the earth which has been washed down from 
 the surrounding higher lands. Muck and peat are examples 
 
 of cumulose soils. 
 
 496. Alluvial soils 
 are those that have 
 been carried by water 
 and deposited some 
 distance from their 
 original source. They 
 commonly show more 
 or less distinct layers 
 as a result of the fact 
 that the coarser parti- 
 cles naturally settle first, while the finest particles are the 
 last to be deposited. The soils in river valleys are alluvial 
 and have been carried down by the stream during the flood 
 season and deposited as the velocity of the current de- 
 creased. Alluvial soils are usually fertile, but it will be seen 
 that the character of these soils varies with the character 
 of the rock material of the uplands from which they are 
 derived. 
 
 497. Colluvial soils are formed on the lower slopes of 
 hillsides. They are composed of particles of various sizes 
 that have moved down the hillside under the force of grav- 
 ity. (See Fig. 190.) 
 
 498. Drift soils are those that have been transported by 
 glaciers. A large part of the northern United States is 
 covered by drift soils that were carried down from the north 
 by the great glaciers which at one time covered this region. 
 Drift soils are characterized by the presence of bowlders 
 and rounded pebbles. They vary considerably in char- 
 acter, and many different kinds of soil may be found in a 
 
KINDS OF SOILS 429 
 
 single farm located in the glaciated region. Drift soils 
 are usually very productive. 
 
 499. ^Eolian soils, or loess, are those that are composed 
 of particles transported by the wind, and are, therefore, 
 sometimes called wind-formed soils. It is supposed that 
 considerable areas of soils in the central United States are 
 wind-formed. They vary in thickness from a few feet to 
 over 100 feet, and are of considerable agricultural value. 
 
 500. A clay soil is one that contains over sixty per cent 
 of clay particles. It is the hardest soil to work, since it is 
 sticky when wet and so hard that it can hardly be pulverized 
 when dry. In very dry weather clay soils crack and form 
 openings that allow excessive evaporation of water, a condi- 
 tion which dries and injures the roots, sometimes breaking 
 them. Clay soils, unless well drained, are likely to be cold 
 and unresponsive. These soils are usually high in potential 
 plant food, especially potash, but require careful handling 
 to enable the plant to make use of this food material. They 
 are usually retentive of added plant food and are, there- 
 fore, soils that can be liberally fertilized without fear of 
 great loss of the applied material. 
 
 501. Sandy soils are those containing a very large pro- 
 portion of sands (75 per cent or more). They are just the 
 opposite of clay soils, being too open and porous, while the 
 clays are too compact and impervious. They hold but 
 little water, and crops growing on them* are likely to suffer 
 in hot, dry weather. These soils are usually low in fertility 
 and have little power to retain added plant food, since the 
 soluble material in manures and fertilizers used on them is 
 likely to leach through them. No soil is so poor that it 
 cannot be made to grow a crop, and even sandy soils can be 
 made productive by the liberal use of organic matter, and the 
 
430 
 
 SOILS AND FERTILIZERS 
 
 addition, if necessary, of lime, phosphoric acid, and potash. 
 They are warm, easily worked soils, and if properly handled 
 are often profitably used, especially for early truck crops. 
 
 502. Peat and muck soils contain very large amounts 
 of organic matter, some of them having as much as 80 per 
 cent of such matter. They are found in the beds of former 
 lakes or swamps, and since they are formed by the partial 
 
 decay of vegetable 
 matter under water, 
 they usually contain 
 but little earth. Peat 
 is an intermediate prod- 
 uct between vegetable 
 matter and coal, and 
 perhaps in course of 
 time it would be con- 
 verted into coal. The 
 name muck is some- 
 times applied to a soil 
 in which the organic 
 matter is in a more advanced state of decay than it is in 
 true peat. A muck contains more earth than the peat does 
 and is more compact. These soils are high in potential 
 nitrogen, but are usually exceedingly low in potash. When 
 they are well drained and are fertilized with phosphorus and 
 potash they are generally fertile soils. Many of the black 
 onion soils belong to this type. 
 
 503. Loam is a soil consisting of a mixture of clay, silt, 
 sand, and organic matter and for most purposes is the 
 most desirable type of soil. Loam soils are usually well 
 balanced, since they hold moisture well, are well supplied 
 with plant food, and have considerable ability to retain 
 
 FIG. 192. Blocks of peat being dried for use 
 as fuel. 
 
KINDS OJ 1 SOILS 431 
 
 such soluble plant food as may be added to them. They 
 allow the air to circulate through them more freely than 
 clay soils do, but they are not so objectionably open as are 
 sandy soils. They are easily worked and have compara- 
 tively little tendency to bake or crust on the surface. They 
 are well suited to most crops and respond well to fertiliza- 
 tion. Several subtypes are recognized : (1) heavy clay 
 loam, (2) clay loam, (3) silt loam, (4) sandy loam, (5) light 
 sandy loam. Taken in the order given above they contain 
 from first to last decreasing quantities of clay, and increas- 
 ing quantities of sand, the heavy clay loam having the 
 most clay and the light sandy loam the most sand. These 
 subtypes naturally partake of the characteristics of their 
 components, so that the heavy clay loam shows in a large 
 measure the properties of a clay, and the light sandy loams 
 are only a step removed from the sandy soils. The others 
 are intermediate between the two extremes. The loams as 
 a whole represent the more common types of farm soils. 
 
 504. Light and heavy soils are names which do not, as 
 might be supposed, refer to the actual weight of soils, but 
 to the ease with which they may be worked with tillage 
 implements. A sandy soil, for instance, is called a light 
 soil, although it actually weighs more per cubic foot than 
 any other type of soil. 
 
 EXERCISES 
 
 Ex. 313. What are the four general classes of rock particles in 
 soils? How are these classes subdivided? Which particles are the 
 smallest ? Work up a little pure clay with water and rub it between 
 the fingers. Do you feel any grit? Do the same with a sandy soil, 
 and note the difference. Place about two tablespoonfuls of fine soil in 
 a quart fruit /jar three fourths full of water. Shake the jar vigorously 
 for several minutes, let it stand for one minute, and pour the muddy 
 
432 
 
 SOILS AND FERTILIZERS 
 
 water into a second jar. The sediment remaining in the first jar is 
 composed almost entirely of sand. Examine it carefully. When the 
 second jar has been standing five minutes pour off the muddy water into 
 a third jar ; add more water, shake this jar vigorously, and after it has 
 stood five minutes pour off the water. The sediment remaining 
 in the second jar is largely silt. Let the third jar stand at least two 
 hours and then pour off the water. The residue in this case is largely 
 clay. Note how fine the particles are. Examine them under a micro- 
 scope. Can you find samples of clay, silt, and gravel in your vicinity? 
 Ex. 314. What are the two general classes of soils according to 
 formation? Are the soils in your vicinity sedentary or transported 
 or both? What are residual soils? Cumulose soils? Can you find 
 either type near the school ? What is meant by allu- 
 vial, colluvial, drift, and aeolian soils? How many 
 of these can you find near your home? How can 
 you tell a drift soil ? Walk along a stream and note 
 how the rock particles of varying sizes are deposited 
 by the stream as the current becomes less rapid. 
 
 Ex. 315. What are the chief characteristics of 
 a clay soil? Of a sandy soil? Of a muck soil? 
 Why are clay soils more difficult to cultivate than 
 sandy soils ? Which hold more water ? Which 
 contain more plant food? Are there any areas of 
 muck soils in your locality ? For what are they used ? 
 Ex. 316. What is meant by a loam ? Why are 
 loam soils desirable ? What general classes of loam 
 soils are recognized ? How many of them can you 
 find in your locality? Bring samples of as many 
 different kinds of soil as you can find to the school 
 and classify them according to this chapter. (The 
 best method of obtaining a sample of soil is by 
 means of the soil auger (Fig. 193), which is made by 
 welding a three-eighths inch gas pipe to a one and 
 one-fourth inch wood auger. The class should take 
 an excursion over the neighboring farms and by the means of the soil 
 auger locate as many soil types as possible.) 
 
 FIG. 193. A soil 
 auger. 
 
CHAPTER LIT 
 
 RELATION OF THE SOIL TO PLANTS 
 
 505. Permeability to Plant Roots. The soil furnishes 
 an anchorage for the plant roots and enables them to hold 
 the plant in an upright position. Since the roots of the 
 ordinary farm crops must penetrate into the soil to a dis- 
 tance of from two to ten feet in order to obtain the necessary 
 amount of plant food, the permeability of the soil is a matter 
 of great importance. A soil that is so compact as to hinder 
 the growth of the roots, or one that has near the surface a 
 hardpan through which the roots cannot penetrate, seri- 
 ously interferes with the full development of the plant. 
 Since the cells of the growing points of the roots need oxygen 
 for respiration, it follows that the soil must be permeable 
 to air as well as to the plant roots. 
 
 506. Water-holding Capacity. Attention has already 
 been called to the enormous amount of water required for 
 plant growth (346). The plant needs water during the 
 entire growing season, and as the rains are irregular and 
 often come weeks apart, the soil must act as a reservoir for 
 moisture. The water-holding capacity 'of the soil, then, is 
 a factor of great importance. The proper condition of 
 moisture in the soil is the most important single factor in 
 determining the fertility of the land, and the failure of soils 
 to produce good crops is more often due to lack of available 
 water than to any other one cause. Any plan that will 
 increase the capacity of the soil to store water is desirable <> 
 
 EV. CHEM. 28 433 
 
434 SOILS AND FERTILIZERS 
 
 507. The Soil Supplies Nitrogen. All plants except the 
 legumes are dependent upon the nitrates in the soil for 
 their supply of nitrogen. Although a good soil may con- 
 tain from three to five thousand pounds of nitrogen to the 
 acre in the surface foot, only a few pounds of it is in the form 
 of nitrates. Nearly all the nitrogen is present in organic 
 matter ; but in these complex organic compounds it 
 cannot be utilized by plants. Nitrification (168), therefore, 
 is necessary to the maintenance of the fertility of the soil. 
 Nitrification takes place only when the temperature of the 
 soil is more than five degrees above freezing, and becomes 
 more rapid with rise of temperature. Hence, it ceases 
 during the winter months and is most vigorous during the 
 hot months of midsummer. The nitrifying bacteria cannot 
 live without a sufficient supply of oxygen, and for this 
 reason stirring the soil to introduce air increases the rate 
 of nitrification. Moreover, these bacteria cannot thrive 
 in a soil that is acid, hence carbonate of lime is essential 
 to nitrification. So vital is the process of nitrification to 
 the growing crop that successful agriculture depends largely 
 upon providing proper conditions for rapid nitrification. 
 
 508. Denitrification. While the nitrifying bacteria may 
 be said to be the farmer's friends, there are, unfortunately, 
 other organisms in the soil that produce evil results. One 
 class of these, known as denitrifying bacteria, decomposes the 
 nitrates, and, perhaps, some other nitrogenous compounds, 
 with the final result that the nitrogen is set free and returned 
 to the air in its elemental condition. This process, of course, 
 robs the soil of a part of its nitrogen, and is especially un- 
 fortunate because it removes the part that was most readily 
 available to the crop. Denitrification can be prevented by 
 providing the conditions that favor rapid nitrification. 
 
RELATION OF THE SOIL TO PLANTS 
 
 435 
 
 509. Fixation of Nitrogen. Leguminous plants are not 
 absolutely dependent upon the nitrates of the soil. These 
 plants use the nitrates as long as they are available; but 
 when the soil fails to supply nitrates in sufficient quantity, 
 they depend upon the nodule-forming bacteria, and thus 
 indirectly make use of free nitrogen. The fixation of nitro- 
 gen is not a function of the legume itself, but of the bac- 
 teria that produce the 
 
 nodules; and in the 
 absence of these organ- 
 isms the legumes are 
 quite as dependent up- 
 on the supply of ni- 
 trates as are the other 
 families of plants. In 
 soils very rich in ni- 
 trogen the root tuber- 
 cles may not be formed 
 on legumes even when 
 the proper bacteria are 
 present. In ordinary 
 soils a crop of clover 
 obtains one third of the 
 nitrogen from the soil 
 and two thirds from the 
 air. 
 
 510. Inoculation of 
 Soils. Experience has 
 shown that not all soils 
 contain the bacteria 
 
 necessary to the fixation of free nitrogen by legumes. . These 
 bacteria may be introduced into a field by scattering on it 
 
 FIG. 194. Effect of inoculation of soil on 
 growth of soy bean. The plant on the left was 
 grown in inoculated soil ; that on the right, 
 without inoculation. 
 
436 SOILS AND FERTILIZERS 
 
 a small quantity of soil from a field in which the same 
 legume has been successfully grown, and then harrowing 
 it in. Nitrogen-fixing bacteria that grow on one kind of 
 legume will not thrive on all other legumes. Therefore the 
 soil from a red clover field is not suitable for inoculating soil 
 for soy beans or alfalfa. Soils on which sweet clover grows, 
 however, may be used to inoculate for alfalfa. 
 
 Inoculation of the soil is of undoubted use in some cases ; 
 but there is danger of overestimating its value. It must 
 not be regarded as a panacea for all the ills of the soil. Inocu- 
 lating a soil simply introduces the nodule-forming bacteria, 
 and if the failure of a leguminous crop was due only to 
 absence of these bacteria, inoculation will be beneficial. It 
 will in no wise overcome failure resulting from bad seed, 
 improper preparation of the ground, adverse weather condi- 
 tions, or acidity of the soil; and the farmer should assure 
 himself that the soil conditions are as favorable as possible 
 before he attempts inoculation. 
 
 511. Mineral Elements. It has been shown that seven 
 elements are necessary to plant growth (350). Of these, 
 only phosphorus, potassium, and calcium need be consid- 
 ered, since experience seems to show that the others are 
 present in all soils in sufficient quantities for maximum 
 crop production. The amounts of nitrogen, phosphorus, 
 and potassium removed by crops seem insignificant when 
 compared with the total quantities of these elements that 
 are present in a good soil. The grain and straw of a thirty- 
 bushel crop of wheat, for example, remove from an acre 
 60 pounds of nitrogen, 10 pounds of phosphorus, and 35 
 pounds of potassium. The first foot of a good loam soil, 
 however, contains to each acre about 5000 pounds of nitro- 
 gen, 2200 pounds of phosphorus, and 35,000 pounds of po- 
 
RELATION OF THE SOIL TO PLANTS 437 
 
 tassium. Such a soil, therefore, has sufficient nitrogen for 
 80 crops of wheat of 30 bushels each, phosphorus enough 
 for 220 such crops, and potassium enough for 1000 crops. 
 Yet it is well known that such a soil would not produce even 
 eighty such crops of wheat in succession. 
 
 512. Chemical Analyses. A chemical analysis gives the 
 total amounts of nitrogen, phosphoric acid, and potash 
 in the soil, but does not indicate what part of these 
 substances is available to the plant. The greater propor- 
 tion of these substances is locked up in insoluble compounds, 
 in which form the plant is incapable of using them. Smaller 
 quantities have been changed by the forces of nature into 
 a condition in which they are available to plants. While 
 the amounts of these materials removed by the crop seem 
 insignificant when compared with the total plant food in 
 the soil, they may be very large in comparison with the avail- 
 able* part. The unavailable, or potential, plant food is 
 gradually being made available, but not with sufficient 
 rapidity to replace that removed from the field at harvest. 
 It will thus be seen that the present fertility of the soil de- 
 pends not upon the potential plant food it contains but 
 upon that which is immediately available to the plant. A 
 chemical analysis is of value, however, in showing the po- 
 tential possibilities of a soil. 
 
 513. Limiting Factors. Since a definite amount of each 
 element of plant food is required for a certain yield, and 
 since none of the elements can be replaced by another (350), 
 it follows that the crop produced will be limited by the quan- 
 tity of the essential element present in least proportion, 
 compared with the requirements of the crop. In other 
 words, if a field of corn can obtain phosphorus sufficient for 
 only half a crop, no more than this can be produced no matter 
 
438 SOILS AND FERTILIZERS 
 
 how much of the other elements of plant food is present. 
 The substance which thus limits the crop production is 
 said to be the limiting factor for that soil. The maximum 
 yield of a particular field is often determined by some one 
 factor, and it is important to discover what that limiting 
 factor is and to apply a remedy. The lack of sufficient water 
 is the most common limiting factor; phosphorus probably 
 ranks second ; and either calcium carbonate or nitrogen 
 ranks third. Potassium is the usual limiting factor in peat 
 and muck soils. 
 
 514. Nature's Methods Contrasted with Those of Man. 
 The amount of vegetation which the soil can produce has 
 been constantly increasing. Under natural conditions this 
 growth is not removed from the ground, and the plant food 
 therein is again made available, so that the land is con- 
 stantly increasing in fertility. Thus the fertility of virgin 
 soils is the result of accumulations due to a variety of forces 
 acting through countless ages, during which little has been 
 removed from the soil while much has been added thereto. 
 
 Man, on the contrary, has reversed this process, and while 
 adding little to the soil has removed much therefrom. 
 Through the constant harvesting of crops, and the leaving 
 of the ground bare and exposed to the action of the elements, 
 he is rapidly depleting nature's store of food, and the yield 
 steadily becomes smaller. To prevent exhaustion of the 
 soil it becomes necessary, therefore, for him to assist nature 
 in making potential plant food available and to return to 
 the soil at least a part of that which he removes in the crops. 
 
 EXERCISES 
 
 Ex. 317. Why must the soil be permeable to plant roots ? What 
 does the plant obtain from the soil? Must the oxygen of the air 
 penetrate into the soil ? Examine a section of soil in an excavation. 
 
RELATION OF THE SOIL TO PLANTS 439 
 
 Ex. 318. Place 100 grams of a thoroughly dried soil in a beaker, 
 add 100 cubic centimeters of water, and stir for several minutes. Place 
 a folded filter paper in a funnel and moisten the filter. When water 
 no longer drips from the filter, place a 100 cc. graduated cylinder under 
 the funnel and pour the mixture of soil and water into the filter. When 
 water ceases to drip from the funnel measure the water which has run 
 through. The number of cubic centimeters of water in the cylinder 
 subtracted from 100 represents in percentage the water-holding capacity 
 of the soil. Repeat the exercise with a sandy, clay, and loam soil. 
 Compare results. Why is the water-holding capacity of the soil im- 
 portant ? 
 
 Ex. 319. In what form do most plants use nitrogen? Is the pro- 
 cess of nitrification very important? At what time of the year is 
 nitrification most active? What are the soil conditions necessary 
 for nitrification? Why is denitrification undesirable? Under what 
 soil conditions does denitrification proceed most rapidly ? 
 
 Ex. 320. Dig up a clover plant or other legume and wash the 
 dirt from the roots. (Do not shake dirt loose.) What connection 
 have the nodules on the roots with the nitrogen supply ? Will legumes 
 form nodules in soils rich in nitrogen? Is the fixation of nitrogen a 
 function of the legume or of the nodule bacteria ? 
 
 Ex. 321. What proportion of its nitrogen does clover obtain from 
 the air and what proportion from the soil? Make a collection 
 for the school of the different root nodules in your neighborhood and 
 preserve them in water with a 10 per cent solution of commercial form- 
 aldehyde. 
 
 Ex. 322. Do all soils contain the proper bacteria for the fixation 
 of nitrogen by legumes? Do the same kind of bacteria work 
 with all legumes? How may the bacteria be introduced into a soil 
 in which they are lacking? To what extent *is inoculation of soils 
 valuable ? Will inoculation take the place of other preparation of the 
 ground ? 
 
 Ex. 323. Which of the elements of plant food are likely to be 
 deficient in the soil? What does a chemical analysis tell about the 
 fertility of the soil ? Explain what is meant by available and potential 
 plant food ? What is meant by a limiting factor in plant growth ? 
 What are the more common limiting factors in plant growth? Con- 
 trast nature's methods in regard to the soil with those of man. 
 
CHAPTER LIII 
 
 SOIL WATER 
 
 515. Structure of Soil. A careful examination of the soil 
 shows that it is made up of grains of various sizes fitted 
 somewhat loosely together, with spaces between them which 
 are as variable in size as the grains themselves. In a loam 
 soil in good tilth the spaces between the grains represent 
 about half the total volume of the soil. 
 
 516. Ground Water. In the surface soil the spaces be- 
 tween the grains are usually filled with air, but at some dis- 
 tance below the surface the spaces are entirely filled with 
 water. This water is known as ground water. The upper 
 surface of the ground water is called the water table. The 
 exact height of the water table may be ascertained by sink- 
 ing a hole to such a depth that water will stand in it, the 
 level of the water in the hole being practically that of the 
 water table. It is ground water that supplies wells and 
 springs. 
 
 517. Free Water and Film Water. After a rainy period 
 the ground may become saturated with water. In such a 
 case the water table is at the surface. The water table 
 gradually sinks, and after a few days of dry weather it may 
 be a foot or more below the surface. The soil water that has 
 drained downward by the pull of gravity is called free, or 
 gravitational, water. The water that remains above the 
 water table is called film water. The following experiment 
 will make clear the difference between free water and film 
 
 440 
 
SOIL WATER 
 
 441 
 
 WATER 
 TABLE 
 
 GROUND 
 WATER 
 
 water. Cork tightly the opening at the bottom of a flower 
 pot. Add soil to the pot until it is nearly full. Then pour 
 in water until the soil is saturated. When this condition is 
 reached the water table is at the surface of the soil. Now 
 remove the cork, and much of the soil water will drain off. 
 This is free water. The 
 water that remains in 
 the soil exists as thin 
 films of moisture around 
 the grains of soil. These 
 films join where the soil 
 grains touch one another 
 and really make one con- 
 tinuous film of moisture 
 throughout the soil. This 
 film moisture is also 
 called capillary water be- 
 cause it moves through 
 the soil by capillary at- 
 traction as oil moves up- 
 ward through a lamp wick. 
 
 518. Movement of Film Water. The tendency in the 
 soil is to maintain an even thickness of film water over all 
 the soil grains ; consequently if anything happens to decrease 
 the thickness of the film in one part of the soil, water will 
 move toward that point to restore equilibrium. When 
 water evaporates from the surface of the soil, more water 
 moves upward to replace the loss. This movement is known 
 as the capillary rise of water. It will thus be seen that 
 evaporation not merely dries the surface of the soil but 
 actually pumps up water from the lower layers and affects 
 the water content of the soil for some distance below the 
 
 FIG. 195. Sectional view of soil showing 
 ground water and film moisture. 
 
442 
 
 SOILS AND FERTILIZERS 
 
 surface. The rate and the amount of capillary movement 
 depend upon the structure of the soil. The coarser the soil 
 the more rapid the rise of water by capillarity, but the finer 
 the soil the higher the water will be lifted. A very coarse 
 sand may raise the water only a few inches, a fine sandy 
 
 FIG. 196. Relation of the water table to contour of the land. 
 
 loam will lift it a few feet, while in a clay soil the water will 
 rise at least twenty-five feet. If the soil is made more com- 
 pact, the capillary rise of water is increased. 
 
 519. How Plants Get Their Water. The roots of the 
 plant push their way down between the soil grains, branch- 
 ing more or less and spreading throughout the soil. The 
 root hairs at the growing points of the roots, which are the 
 absorbing organs of the plant, work their way in between 
 and around the small soil grains, adhering very closely to 
 them. The root hairs absorb the water of the film moisture, 
 and as they reduce the thickness of the film, more water 
 diffuses to the point of absorption. Since the root hair gets 
 all its water and food from the film on the surface of the 
 soil grains, film moisture is a desirable form in which to have 
 water in the soil. 
 
 520. High Water Table Objectionable. The crops are sure 
 to suffer when the level of the ground water is near the sur- 
 face of the soil (Fig. 197). A high water table limits the feed- 
 ing space available to the plant and, consequently, the amount 
 
SOIL WATER 443 
 
 of food it can obtain. The plants that are of agricultural 
 importance must have their roots supplied with air, and 
 such plants do not send their roots below the water table 
 because the spaces between the soil grains below this level 
 are filled with water, a condition which prevents the entrance 
 of air. The depth to which the roots will go, then, depends 
 upon the position of the water table. 
 
 Free water near the surface is also objectionable because 
 it makes the soil cold. It requires much more heat to warm 
 water a certain number of degrees than to raise the tempera- 
 ture of an equal weight of the dry matter of the soil the 
 same number of degrees. Hence a soil that contains much 
 water is harder to heat than one that is comparatively dry. 
 
 A very wet soil causes plant food to become locked up in 
 unavailable forms, and in some cases brings about the pro- 
 duction of compounds that are actually poisonous to the 
 desirable plants. An excessive amount of water in the 
 soil also dilutes the plant food in solution and makes it 
 more difficult for the plant to procure sufficient nourishment. 
 
 One of the most important considerations in this connec- 
 tion is the fact that the presence of free water in the soil 
 prevents nitrification and promotes denitrification. In 
 water-logged soil, nitrates are rapidly decomposed, the nitro- 
 gen being given off to the air in the free, or elemental, con- 
 dition; and for this reason not only is nitrogenous food 
 in the soil destroyed, but the application of nitrogen ferti- 
 lizers to such a soil results in great waste of this valuable 
 element. 
 
 521. Underdrainage. When the water table, during 
 much of or all the growing season, is nearer than three feet 
 to the surface of the ground, some system of underdrainage 
 becomes necessary, if the best results in crop production 
 
444 
 
 SOILS AND FERTILIZERS 
 
 are to be achieved. This is best accomplished by means 
 of drain tile. The benefits of tile drainage are summarized 
 in the following paragraphs. 
 
 The water table is lowered to the level of the drain tile, 
 the water running off through the tile instead of remaining 
 in the soil as stagnant water. The plant roots can now pene- 
 trate the soil to a greater depth, since air follows the water 
 
 FIG. 197. Effect of lack of drainage on root growth. The high water table 
 shown on the left limits the feeding space of the roots, and in time'of drought, 
 as shown on the right, the plant suffers because of its shallow roots and lack 
 of moisture. 
 
 as it percolates downward, thus ventilating the soil. This 
 ventilation is of great importance and it is continuous, since 
 each rain forces some of the old air out of the soil, and the 
 new air following the rain takes its place. 
 
 In a well-drained area, more of the rain will soak into the 
 soil instead of running off the surface ; thus surface washing 
 of the soil will be prevented to some extent. Ideal conditions 
 demand that there shall be no run-off at all, and the farmer 
 should strive to attain as nearly to this ideal as is practicable. 
 
SOIL WATER 
 
 445 
 
 In some countries, where terrace farming is followed, the run- 
 off is almost entirely eliminated. 
 
 The spring rains are usually warm, and it is desirable 
 to have them percolate through the soil. Tile-drained 
 soils warm up earlier in the spring, stay warm later in the 
 fall, and maintain a higher temperature throughout the grow- 
 ing season than do undrained soils. This is partly due to 
 
 FiQ. 198. Effect of proper drainage on root growth. 
 
 the fact that more evaporation takes place from the surface 
 of the undrained soil (8). For these reasons crops on well- 
 drained soils have a longer season for growth. 
 
 Tile drainage promotes nitrification and prevents denitri- 
 fication. The decay of organic matter, resulting in the 
 production of nitric acid, is an oxidizing process and can 
 take place only in a well- ventilated soil. 
 
 Many thousands of square miles of waste land have been 
 reclaimed by means of tile drainage. In the case of swamps, 
 marshes, and ponds the water table is actually at or above 
 
446 SOILS AND FERTILIZERS 
 
 the surface of the ground, and such lands will not produce 
 the ordinary farm crops at all until they are drained. 
 
 522. Drainage Reduces Injury from Drought. Para- 
 doxical as it may seem, underdraining increases the amount 
 of water available to the plant. The crop depends almost 
 entirely on the capillary or film moisture for its supply of 
 water, and the roots do not enter that part of the soil con- 
 taining free water. Lowering the water table greatly in- 
 creases the total amount of film moisture, as all that part of 
 the soil from which the free water has been removed is 
 capable of holding capillary water. Thus it will be seen that 
 while the total amount of water in the soil is decreased by 
 drainage, that amount which is of use to the plant is made 
 much greater. Drainage prevents injury from drought also, 
 by allowing plants to make deeper root growth, hence they 
 are not so easily affected by the extreme drying of the sur- 
 face of the ground that takes place in times of scanty rainfall. 
 
 523. No Useful Water Lost Through Tiles. It will 
 readily be seen that tile draining determines the highest 
 point the water table can reach, but in dry weather the level 
 of the ground water may be much below the drain. It is 
 sometimes feared that for this reason a part of the water 
 from summer rains may be lost through the tile. Experi- 
 ence has shown, however, that the water does not percolate 
 into the drain, as some suppose, but that the drains remove 
 water only when there is sufficient rain to raise the water 
 table to the level of the tile. It is simply the excess of water 
 that is removed by the underdraining, and not the part 
 that is of importance to the plant. 
 
 524. Drainage Sometimes Beneficial on High Lands. 
 Strangely enough, experience has shown that it is not merely 
 low-lying soils that are benefited by underdraining. In 
 
SOIL WATER 
 
 447 
 
 many cases heavy clay soils in elevated positions, especially 
 if underlaid by rather impervious subsoils, are greatly im- 
 proved by tiling. In such soils the percolation is so slow 
 that practically the same effect is produced as would be 
 expected if the general level of the ground water were near 
 the surface. These soils are made more mellow by drainage 
 and respond more readily to early tillage. In fact, it may 
 be said that it will pay to tile drain any soil that has a clay 
 subsoil, no matter what the elevation or slope of the land. 
 
 525. Draining the Farm. The laying out of a complete 
 system of drainage calls for the services of a skilled drainage 
 
 FIG. 199. A, Drainage system for level land. B, Drainage system where 
 there is much variation in the slope of the land. 
 
 engineer, especially if the farm is very level. The more 
 fall there is to the land, the easier it is for an unskilled person 
 to lay drains that will work. Since the tile must be se laid 
 
448 
 
 SOILS AND FERTILIZERS 
 
 as to give a uniform fall from the highest point to the out- 
 let, the planning of the system should be preceded by a 
 survey of the farm for that purpose. When the field to 
 be drained is broad and level (Fig. 199^1), the main drains 
 and laterals are uniformly spaced ; but often the ground has 
 natural drainage lines (Fig. 199 B) along which it is usually 
 best to run the ditches, especially the main lines. 
 
 The size of the tile should vary with the area to be 
 drained and with the grade at which the tile is laid. With 
 an average fall of one inch to one hundred feet, a four- 
 inch tile will drain ten acres. With a greater fall this size 
 of tile would remove the water from a larger area. 
 
 The depth at which the 
 tile is placed and the 
 distance between the lines 
 of tile depend upon the 
 character of the soil. The 
 more compact the soil the 
 nearer together the lines 
 of tile and the less the 
 depth. In very heavy 
 clays the drains should 
 not be farther than two 
 rods apart, while in lighter 
 soils the distance apart 
 may be twice as great. 
 Clay soils should have the 
 drains placed about thirty 
 inches deep ; but in light soils the tile may be as much as 
 four feet below the surface. 
 
 Unglazed clay tile are the more common. Glazed tile 
 may be used, however, since all the water enters at the joints 
 
 FIG. 200. Drainage machine at work. 
 
SOIL WATER 
 
 449 
 
 and there is no advantage in having porous tile. Machines 
 are now on the market for making tile from cement. 
 
 The ditches for laying the tile are often dug by hand, 
 and various special tools have been devised for use in ditching 
 as well as for laying the 
 tile. Machines worked 
 by horse power and by 
 tractors (Fig. 200) are 
 used in ditching, when 
 the character of the soil 
 permits. 
 
 526. Irrigation. There 
 are sections of this coun- 
 try and of other countries 
 that receive no rainfall or 
 such a limited amount 
 that crop production is 
 impossible without the 
 aid of some system of 
 irrigation. The last few 
 decades have seen thou- 
 sands of square miles of the earth's surface that were 
 formerly barren made productive by means of irrigation. 
 Water for this purpose is sometimes obtained from wells 
 and springs, but most of it comes from running streams. 
 In sections where the streams become too low during the 
 summer months the water is collected in reservoirs from 
 which it is drawn as needed. In some cases where there is 
 a plentiful supply of water it is merely diverted from the 
 river into canals from which the fields are supplied. 
 
 Irrigation farming has one advantage over farming in 
 humid climates, namely, that the farmer has the water supply 
 EV. CHEM. 29 
 
 FIG. 201. Laying tile in ditch. 
 
450 
 
 SOILS AND FERTILIZERS 
 
 for the crops directly under his control. Water can be added 
 at the time it is needed by the plants and in the right quan- 
 tity, without dependence upon the uncertainties of natural 
 rainfall. Under favorable conditions the expense of provid- 
 ing the water is more than repaid in the larger crop pro- 
 duced. 
 
 527. Methods of Irrigation. Two general methods of 
 distributing the water over the field are used in the arid 
 sections of this country. In the first method the water 
 
 FIG. 202. Irrigation by furrows. 
 
 is flooded over the ground in as even a layer as possible. 
 For best results with this system the ground must be quite 
 level. This method is used on such crops as alfalfa or other 
 hay crops. On cultivated ground it is not so desirable. 
 
 The second method is more commonly used, and consists 
 in distributing the water by means of furrows (Fig. 202). 
 These furrows are opened at distances varying with the 
 character of the soil. They have sufficient fall to cause the 
 
SOIL WATER 
 
 451 
 
 water to run slowly through them and so soak into the ground 
 as it passes along the furrow. This method seems to be the 
 most economical of water and labor for use on cultivated 
 lands. The western fruit orchards are irrigated in this way. 
 528. Irrigated Soils Must be Underdrained. Even in arid 
 climates, soils which are irrigated must be tile drained after 
 a few years of irrigation. One reason for this is that the 
 
 FIG. 203. Irrigation by sprinkling. 
 
 wonderful yields produced by the application of water have 
 in some instances led to overdoing irrigation, with the result 
 that the soil becomes water-logged. Ma*ny areas on the delta 
 of the Nile, for example, have become water-logged since the 
 introduction of perennial irrigation, and many of these tracts 
 are now being underdrained. 
 
 Another reason why drainage is necessary in arid sections 
 is that irrigation without drainage brings about the accumu- 
 lation of an injurious quantity of alkali salts near the surface 
 
452 SOILS AND FERTILIZERS 
 
 of the soil. The water dissolves the salts and brings them 
 to the surface by capillarity ; and then as the water evapo- 
 rates the alkalies become concentrated near the surface. 
 By putting in tiles and using plenty of water the excess of 
 alkalies can be washed out of the soil. 
 
 529. Irrigation in Humid Climates. Although there is 
 no doubt about the value of irrigation in arid climates, its 
 usefulness in that part of this country that lies east of the 
 Mississippi River is not so generally recognized. Eastern 
 market gardeners find, however, that it pays in most seasons 
 to do some irrigating. Some of them use a plan much like 
 the furrow system, but many have adopted a sprinkling 
 system similar to the one shown in Fig. 203. This method 
 of applying water appears to be very successful for market 
 gardens in the central and eastern states, where it merely 
 serves to supplement a naturally good rainfall. Moreover, 
 the gains in yield through irrigation of certain field crops 
 at the Wisconsin Experiment Station indicate that even in 
 the Middle West it might pay to irrigate such crops on farms 
 where water could be obtained at little cost. 
 
 EXERCISES 
 
 Ex. 324. Fill two glass tumblers to within one half inch of the 
 top, one with a clay soil and the other with a sandy soil. Compact 
 the soil by gently tapping the tumblers on the desk. Pour water on 
 slowly from a graduated cylinder until it stands just at the level of 
 the top of the soil. Note the difference in the amount of water required 
 by the two soils. The water absorbed represents the pore space of 
 the soils. Which has the more pore space, a coarse-grained or a fine- 
 grained soil ? How much pore space does a good loam soil contain ? 
 
 Ex. 326. Perform the experiment described in 517. What is 
 meant by film moisture in soils ? By ground water ? By the water 
 table ? At what depth is the water table where you live ? How can 
 you tell? 
 
SOIL WATER 
 
 453 
 
 Ex. 326. Tie pieces of 
 cheesecloth over the ends of 
 two tall glass tubes, or two long 
 chimneys, and fill one with a 
 clayey soil and the other with a 
 sandy soil .(Fig. 204). Place 
 the lower ends of the tubes in 
 a pan of water. Does the water 
 rise in the tubes? In which 
 will it rise to the greater 
 height? Explain how evapo- 
 ration from the surface of the 
 soil brings water up from be- 
 low. From what water in the 
 soil do plants get their supply ? 
 Will water in the soil move 
 toward the plant roots ? Why 
 is film water important ? 
 
 Ex. 327. What effect does 
 
 FIG. 204. Apparatus to illustrate the capillary 
 rise of water in clayey and sandy soils. 
 
 a high water table have on the root development of the plant ? Will 
 the roots of the agricultural plants penetrate below the water table? 
 Why? Why does free water make the soil cold ? What effect does a 
 
 wet soil have on the plant food? How 
 does free water affect nitrification and 
 denitrifi cation ? 
 
 Ex. 328. Grow two plants in tin 
 cans, one of which has holes in the bot- 
 tom while the other has not. Keep the 
 soil in the can without the perforations 
 saturated with water, and add the same 
 amount of water to the other can. What 
 difference do you note in plant growth ? 
 Explain the various ways in which un- 
 derdrainage is beneficial to soils. Ex- 
 plain how drainage decreases the danger 
 of injury from drought. 
 
 20 . 5 -- p ' rforat <; d f arth - Ex. 329. Make three holes in a tall 
 showing how water leaves 
 
 the soil by drainage. can as shown in Fig. 205. Fill the can 
 
454 
 
 SOILS AND FERTILIZERS 
 
 with soil and pour water on the top. Through which hole does the 
 water escape? Is there any danger of losing good water through 
 drainage ? The apparatus shown in Fig. 206 is convenient in perform- 
 ing this experiment and gives condi- 
 tions more nearly conforming to those 
 in a tile-drained field. 
 
 Ex. 330. How should you lay out 
 a system of drainage for your home 
 farm ? Is your farm tile drained ? In 
 which kind of soil sandy or clayey 
 should you lay tile deeper and 
 farther apart? How does the water 
 enter the tile ? Why should the outlet 
 of the tile be protected ? 
 
 Ex. 331. In what sections is irri- 
 gation most commonly practiced? 
 Has irrigation farming any advantage 
 over the system which depends on the 
 natural rainfall? What are the two 
 more common methods of applying the water? 
 
 Ex. 332. Mix a little soda with a sandy loam soil and place it in a 
 pot. Keep the pot standing in a pan of water. After some days 
 note whether the soda has collected at the top of the soil. How do you 
 explain it? Why should irrigated lands be underdrained ? Remove 
 the pot from the pan of water and pour water repeatedly on top of 
 the soil. Does drainage remove the alkali ? 
 
 Ex. 333. What can you say about irrigation in humid climates? 
 Do any of the farmers or gardeners in your locality use irrigation? 
 Describe the system used by them. Are there any fields on your farm 
 which could be irrigated at small cost ? 
 
 FIG. 206. Graham McCall 
 drainage apparatus. 
 
CHAPTER LIV 
 TILLAGE 
 
 530. Tillage Increases Feeding Ground for Roots. Good 
 tillage is the most efficient means of assisting nature in the 
 conversion of unavailable plant food into forms that the 
 plant can use. Tillage, in the sense in which it is used here, 
 signifies any operation of stirring and pulverizing the soil 
 by means of plows, harrows, cultivators, or any other imple- 
 ments, either before or after the seed is sown. 
 
 The most noticeable result of tillage is that it makes 
 the soil finer by breaking the large lumps into smaller 
 particles. Pulverizing the earth is beneficial in many ways. 
 In the first place, loosening the soil makes it easier for the 
 plant roots and root hairs to penetrate it. Mention has 
 been made of the fact that all soils are composed of particles 
 of rock separated by air spaces. The tender root hairs 
 must push their way in between these soil grains, since it is 
 impossible for them to penetrate the solid particles them- 
 selves. It must be evident that the more the soil is pulver- 
 ized the larger the number of the openings between grains, 
 and, consequently, the greater room for' root growth. 
 
 Good tillage increases the amount of surface exposed to 
 the roots by breaking the large lumps into small grains ; and 
 the more complete the pulverization, the larger the area 
 from which the plant can obtain its food. An example 
 will serve to illustrate what is meant. A cube 2 inches on 
 a .side presents a surface of 24 square inches. If this 
 
 455 
 
456 SOILS AND FERTILIZERS 
 
 cube is cut once in each direction, 8 cubes are formed, each 
 one inch on a side, giving a total of 48 square inches of sur- 
 face, so that cutting only once in each direction doubles 
 the amount of surface. Thus, theoretically, a plant should 
 be able to derive twice as much food from the eight small 
 cubes as from the large one. 
 
 531. Tillage Aerates the Soil. One of the most advan- 
 tageous results to be obtained from tillage is the aeration 
 of the soil. The introduction of the oxygen of the air into 
 the soil is of benefit in many ways. It makes possible the 
 growth of the plant roots ; it enables the seeds to germinate ; 
 it aids nitrification ; and it prevents denazification. 
 
 The oxygen of the air also has a direct chemical action 
 upon the mineral matter of the soil and tends to make it 
 soluble. In addition it prevents the formation of certain 
 injurious compounds, notably certain ferrous compounds. 
 
 The bacteria that enable leguminous plants to use free 
 nitrogen are also dependent upon the air in the soil ; for not 
 only do they need oxygen, but experiments have shown that 
 it is only from the air in the soil that they can draw their 
 supply of nitrogen. It is necessary, therefore, in order that 
 leguminous plants may profit by the nodule-forming bac- 
 teria, to have the soil in such condition of tilth that the air 
 may freely circulate through it. 
 
 532. Tillage Increases Amount of Available Water. 
 Tillage not only increases the amount of surface on which 
 the plants can feed, but at the same time enlarges the water 
 supply by giving the soil greater capacity for holding mois- 
 ture. Attention has been called to the fact that each soil 
 grain is surrounded by a film of water which is called capillary 
 water or film moisture. The plant is dependent upon this 
 film moisture for its supply, and it is readily seen that the 
 
TILLAGE 457 
 
 \ 
 
 amount of capillary water that the soil can retain depends 
 upon the aggregate surface area presented by the particles 
 of which it is composed. 
 
 The following quotation from King illustrates in a strik- 
 ing way the rate at which the film moisture in the soil 
 increases as the soil particles decrease in size. " Suppose 
 we take a marble exactly one inch in diameter. It will 
 just slip inside a cube one inch on a side, and will hold a 
 film of water 3.1416 square inches in area. But reduce 
 the diameters of the marbles to one tenth of an inch, and at 
 least 1000 of them will be required to fill the cubic inch, 
 and their aggregate surface will be 31.416 square inches. 
 If, however, the diameters of these spheres are reduced to one 
 hundredth of an inch, then 1,000,000 of them will be required 
 to make a cubic inch, and their total surface area will then 
 be 314.16 square inches. Suppose again the soil particles 
 to have a diameter of one thousandth of an inch. It will 
 require 1,000,000,000 of them to fill completely the cubic 
 inch, while their aggregate surface must measure 3141.6 
 square inches." 
 
 It will be noted that the smallest particle mentioned in 
 the foregoing paragraph has five times the diameter of the 
 clay particle (492) . It has been estimated that a cubic 
 foot of clay has 150,000 square feet of surface, while a cubic 
 foot of coarse sand has 40,000 square feet of surface. 
 
 533. Tillage to Conserve Moisture. 'From what has been 
 said regarding the importance of water to the plant it must 
 be apparent that one of the chief problems of agriculture 
 is to maintain a proper degree of moisture in the soil. It 
 seldom happens that a crop can obtain from the soil the 
 amount of water necessary for a maximum yield, and great 
 skill is required to keep it from suffering for lack of moisture 
 
458 
 
 SOILS AND FERTILIZERS 
 
 during the hot summer period of scanty rainfall. While 
 man can do nothing in the way of distributing the rainfall 
 throughout the growing season, he can, by a judicious use 
 of tillage methods, do much toward saving the excess of 
 moisture precipitated in the early 
 spring for the use of the plant during 
 the drier weather of the summer. One 
 way in which tillage accomplishes this 
 end is by increasing the capacity of the 
 soil for storing water as described in 
 the preceding paragraph. It must also 
 be evident that the loosening of the 
 ground incident to tillage makes it 
 easier for the rain to enter the soil and 
 tends to prevent loss by surface wash- 
 ing, as the water sinks into the soil 
 instead of running away. 
 534. The Earth Mulch to Conserve Moisture. During 
 dry weather water is constantly being evaporated from the 
 surface of the ground. Under ordinary conditions, where 
 the soil is somewhat firm, water is drawn up from below by 
 capillary attraction to replace that removed by evapora- 
 tion. As this may be very rapid in the hot dry weather of 
 midsummer, the result is that the water is virtually pumped 
 out of the soil until the soil is too dry for plant growth. 
 
 The soil under a board which has been lying in the garden 
 for some days is usually moist, no matter how dry the sur- 
 rounding soil may be, because the board has prevented the 
 evaporation of the capillary moisture. Gardeners often save 
 the moisture of the soil by the use of a thick mulch of straw 
 to prevent evaporation. This method is not applicable 
 to extensive farming, but the same results may be obtained 
 
 FIG. 207. The soil 
 mulch prevents loss of mois- 
 ture from the soil. 
 
TILLAGE 459 
 
 by the use of the earth mulch, which is simply a layer of 
 soil two or three inches deep so dry and loose that it cannot 
 take up the capillary water from the soil beneath it. To 
 make an effective earth mulch the cultivation should be 
 shallow and frequent, the aim being to make the layer as 
 dry as possible. A rain, of course, will again compact the 
 loose earth and renew capillarity, so that cultivation should 
 be repeated as soon as possible after a rain. Even in absence 
 of rain the mulch will sooner or later become compact if 
 left too long without stirring. A mulch about three inches 
 deep has been found to be most effective in conserving 
 moisture. 
 
 The surface of irrigated soils should be cultivated as soon 
 after each application of water as possible, so that an earth 
 mulch may be formed 
 and the water retained. 
 This practice results in 
 a great saving in the 
 amount of water that 
 has been applied. 
 
 535. Early Spring 
 Plowing to Conserve 
 
 Moisture. Plowing the FIG. 208. Large amounts of water are lost 
 
 ground very early in the 
 
 spring is a desirable practice, for there, is no other season 
 when tillage is so effective in conserving the moisture of the 
 soil. King reports one experiment in which early-plowed 
 ground seven days after plowing contained an amount of 
 water equal to 1.75 acre inches in excess of an adjoining 
 plot which was not plowed. An acre inch of water is the 
 amount of water that would make a layer an inch deep over 
 an acre of ground. An experiment on early and late plowing 
 
430 SOILS AND IERTILIZERS 
 
 for corn in Ohio showed that the moisture content of the 
 early-plowed plots was higher throughout the season than 
 that of the late-plowed plots. It showed also that the 
 available nitrogen was much higher in the early-plowed 
 plot and that the yield of corn was greater. Therefore the 
 soil should be stirred as early in spring as possible without 
 injury to its texture, either by plowing or by the use of some 
 form of cultivator or harrow. 
 
 536. Fall plowing as well as spring plowing increases 
 the water supply of the soil, because it leaves the ground 
 with a loose uneven surface, in which condition it more 
 readily absorbs the water of the winter rains. An experi- 
 ment reported from Wisconsin shows that a plot plowed 
 in the fall contained 1.15 inches more water than an adjacent 
 plot not so plowed. Many soils in the northern states are 
 improved by fall plowing, because the freezing and thawing 
 brings about disintegration of the clods and leaves the soil 
 in better tilth. The greatest advantage of fall plowing, how- 
 ever, is that it decreases the amount of plowing that must 
 be done during the rush of spring work. Soils that are sub- 
 ject to washing cannot safely be plowed in the fall. 
 
 637. Tillage to Destroy Weeds. Weeds should not be 
 allowed to grow, because they rob the crop of the moisture 
 and plant food that it needs. Since weeds are usually 
 broad-leaved, vigorous plants that transpire large quantities 
 of water, and since there is seldom water to spare in the 
 soil, weeds are injurious to the growing crop. 
 
 While it is probable that weeds work the greatest injury 
 to the crop by depriving it of water, they also rob it of 
 mineral food. Some farmers argue that if the plants remain 
 on the ground they remove no plant food. It must be 
 remembered, however, that they use that portion of the 
 
TILLAGE 461 
 
 plant food that would be available to the crop and that 
 the weeds must decay before this food is again rendered 
 available. In so far as any one crop is concerned the plant 
 food is as completely removed by a growth of weeds imme- 
 diately preceding it as it would be if it were actually taken 
 from the field. In an experiment in New Hampshire corn 
 was grown with and without cultivation, so that in one plot 
 
 FIG. 209. A well-prepared seed bed is important in the production of large crops. 
 
 the weeds were allowed to grow, while in the other the weeds 
 were all destroyed. The first plot produced only 17 bushels 
 to the acre, while the cultivated plot yielded 80 bushels. 
 
 The destruction of weeds was formerly regarded as the 
 only reason for tillage after seeding. It is now known, 
 however, that stirring the soil has a distinct value in itself. 
 If the farmer tills his soil, so as to reap the maximum benefits 
 of this process, he will have no need to worry about the weeds. 
 
 538. Dry Farming. It has been estimated that one 
 half of this country has a rainfall of less than twenty inches. 
 
462 
 
 SOILS AND FERTILIZERS 
 
 FIG. 210. Barley grown three years in 
 succession in a dry fanning district. Yield 
 5.33 bushels per acre. 
 
 Such a rainfall is not sufficient to produce a good crop 
 each year. In some of these semi-arid sections the land is 
 
 , ; , so located that it can be 
 
 irrigated, and it is being 
 rapidly reclaimed by the 
 irrigation projects of the 
 national government as 
 well as by those of pri- 
 vate enterprise. 
 
 Much more of the 
 land in these semi-arid 
 sections, however, is be- 
 yond the reach of irri- 
 gation, and must be 
 handled in an entirely 
 different manner if it is to produce profitable crops. On 
 some of these lands dry farming is followed. This is prac- 
 ticable on land receiv- 
 ing an annual rainfall 
 of 12 to 14 inches or 
 more, and consists in 
 utilizing the moisture 
 of two years to produce 
 a crop, instead of trying 
 to grow one each year. 
 It is a broad application 
 of the earth mulch. 
 In dry farming a crop 
 
 is produced in each FIG. 211. Barley grown after fallow on land 
 
 field once in two years, adjacent toFig ' 2I0 ' Yield31 - 27 busnels P eracre - 
 so that a farmer who, for example, owns 320 acres has crops 
 growing on 160 acres but nothing growing on the other 160 
 
TILLAGE 463 
 
 acres. Immediately after a crop is harvested the ground is 
 plowed and harrowed to produce an earth mulch which is 
 maintained by thorough cultivation for the remainder of 
 that year and all through the second year. The principle of 
 the mulch is carried still farther, for the ground after seeding, 
 and even after the crop is up, is harrowed as long as it can 
 be done without injury to the growing crop. 
 
 This system of tillage permits all the rain water to 
 soak into the soil and prevents its subsequent evaporation, 
 a condition which is very necessary because the dry air and 
 winds of the semi-arid regions cause rapid evaporation. The 
 soils in these regions are high in available plant food because 
 very little of it has been leached out, and the only requisite 
 for a good crop is an adequate supply of water. 
 
 Some of these soils settle so slowly after plowing that a 
 special implement known as the subsurface packer has been 
 invented for use on them. This implement packs the soil 
 below without destroying the loose condition of the surface. 
 In this way capillary connection is renewed between the 
 plowed soil and that beneath, while evaporation from the 
 surface is prevented by the mulch. 
 
 539. Summer Fallowing. A practice similar to dry farm- 
 ing was formerly followed in humid climates and is still 
 advocated by some people. This practice, which is knov/n 
 as summer fallowing, consists in allowing the field to go 
 through one summer without growing a crop, the surface 
 of the soil being frequently cultivated to produce a mulch. 
 
 This method came into use at a time when the tillage 
 implements were very crude and it was possible to control 
 the weeds in no other way. The crop following a summer 
 fallow is always larger than it would be otherwise, but in 
 sections with an annual rainfall of over thirty inches, dis- 
 
464 SOILS AND FERTILIZERS 
 
 tributed throughout the year, the increase of crop seldom 
 pays for the loss of a crop during the fallow year. There 
 is also danger in this method of excessive loss of nitrogen 
 by leaching. In an experiment at the New York Experi- 
 ment Station over 300 pounds of nitrogen were lost in a year 
 in the drainage of water from an acre of fallow ground, an 
 amount equal to that removed by four 50 bushel crops of 
 corn. No nitrogen was lost from an adjoining plot on 
 which grass was growing, because the plants utilized the 
 nitrates as fast as they were formed. 
 
 540. Short Fallows Desirable. Although the long sum- 
 mer fallow is to be recommended only when the soil has 
 been abused and has become so foul with weeds that no 
 other method will remove them, frequent use should be made 
 between crops of the short fallow. It will be found advan- 
 tageous in many instances to plow the land immediately 
 after the removal of one crop and keep it well stirred until 
 the planting of the next plot. By this means loss of moisture 
 from the soil is prevented, the decomposition of the organic 
 matter is hastened, and a large supply of available plant 
 
 food is prepared for 
 the succeeding crop. 
 This method is es- 
 
 W ^^ygjjjjjj pecially to be recom- 
 mended in preparation 
 
 .i^^Sffr- *- -~. for fall - se f ed CT P S in 
 
 sections of scanty sum- 
 mer rainfall. 
 
 F,0.212.-Plowmgin a ,eOrient. 
 
 plow is one of the oldest 
 
 tillage implements, its use antedating history. From a 
 crooked stick (Fig. 212) drawn by an ox, a donkey, or even 
 
TILLAGE 
 
 465 
 
 a slave, the plow has developed into the steel mold- 
 board plow (Fig. 213) of to-day. There are many kinds 
 of plows, a kind for every purpose, the principal differ- 
 ences in them being the shape of the moldboard. The 
 
 MOLDBOARD 
 SHARE 
 
 POINT 
 
 BEAM 
 
 FIG. 213. General purpose plow. 
 
 breaking plow (Fig. 214) has a long moldboard with a 
 slight curve that turns the sod without breaking it. The 
 stubble plow has a steep moldboard with a sharp, bold 
 
 LTEIR 
 
 FIG. 214. Breaking plow. 
 
 outward curve at its upper extremity, which gives the 
 furrow slice a twist, causing it to break and crumble as 
 it falls. There is a plow (Fig. 215), that has a revolving 
 steel disk in place of the moldboard. The advantage 
 EV. CHEM. 30 
 
466 
 
 SOILS AND FERTILIZERS 
 
 claimed for this plow is that it overcomes the danger of 
 developing a hardpan, which may happen when the land 
 is plowed repeatedly at the same depth with the ordinary 
 
 FIG. 215. Disk plow. 
 
 plow. The disk plow does not work well in heavy clay 
 
 soils, but is better adapted to lighter soils. 
 
 542. Plowing is the most laborious, but at the same 
 
 time the most effective, tillage operation, and should be 
 
 so conducted as to 
 leave the least pos- 
 sible amount of work 
 for the tillage im- 
 plements that fol- 
 low. The plowing 
 should completely 
 cover all vegetation 
 
 and manure and incorporate it as completely as possible 
 
 with the soil. 
 The depth to plow depends upon the soil, the climate, the 
 
 crop to be grown, and the time of the year. In general it may 
 
 FlG. 216. Subsoil plow. 
 
TILLAGE 
 
 467 
 
 be said that light sandy soils should be plowed from five to six 
 inches, while clay soils should be plowed eight or nine inches 
 deep. In case of a clay soil that has previously had shallow 
 plowing, the soil should be gradually deepened by setting 
 the plow an inch deeper each time until the desired depth 
 has been reached. 
 , Plowing deeper 
 than eight to ten 
 inches requires more 
 power and raises 
 the question as to 
 how deep the soil 
 may be plowed with 
 profit. Special deep- 
 tillage implements 
 (Fig. 217) have 
 lately been devised 
 that will turn the 
 soil to a depth of 
 from twelve to four- 
 teen inches ; but 
 since they require 
 nearly twice the 
 power of an ordi- 
 nary plow running FIG. 217. Deep-tillage machine. 
 
 nine or ten inches, it remains to be seen whether the extra 
 labor outlay is profitable. The subsoil plow (Fig. 216), 
 which follows after the ordinary plow and loosens the subsoil 
 in the bottom of the furrow; has been known for some years 
 but never has been popular ; and its use is seldom advocated. 
 One of the most difficult things to judge is the proper 
 time to plow clay soils. This can be learned only by experi- 
 
468 SOILS AND FERTILIZERS 
 
 ence. If the soil is too wet, the working of it puddles the 
 clay so that upon drying the soil is left hard and lumpy. If 
 the soil is too dry it will be so hard that the draft on the plow 
 is very great and the furrow slice breaks into large, hard 
 clods. Plowed at the right time, the soil will crumble 
 into a loose mass and be left in good tilth. 
 
 543. Harrows and Harrowing. As soon as possible 
 after the ground is plowed the soil should be completely 
 
 FIG. 218. Spike-tooth harrow. 
 
 pulverized by means of the harrow. In this way a better 
 seed bed is prepared, and a soil mulch is formed on the sur- 
 face to conserve moisture. Many farmers delay the har- 
 rowing too long, with the result that the soil becomes dry 
 and does not readily pulverize. In case a crust forms on 
 the ground before planting it should be harrowed again. 
 In fact, the modern practice is to harrow the ground even 
 after the crop is up, especially in the case of corn. There 
 is no more effective and economical method of destroying 
 weeds than by these repeated harrowings in the spring. 
 For use on light soils the harrow is sometimes replaced by 
 the weeder. 
 
TILLAGE 
 
 469 
 
 The most common form of harrow is the spike-tooth har- 
 row (Fig. 218) with either the wooden or metal frame. A 
 lever is commonly attached so that the spikes may be set at 
 different angles and 
 thus be made to go at 
 varying depths. 
 
 The spring-tooth 
 harrow (Fig. 219) is 
 also used to pulverize 
 the top soil. It is rec- 
 ommended for stony 
 ground, since the teeth 
 can spring back and 
 
 . FIG. 219. Spring-tooth harrow. 
 
 release themselves 
 
 when they catch upon an obstruction. It is also some- 
 times used to cultivate alfalfa and other growing crops in the 
 spring. The Acme harrow (Fig. 220) consists of a row of 
 
 FIG. 220. Acme harrow. 
 
 curved knife-teeth and cuts and pulverizes the soil in such 
 a way as to prepare a good seed bed. 
 
 The disk harrow (Fig. 221) is one of the most useful im- 
 plements of the farm. It is effective for loosening and pul- 
 
470 
 
 SOILS AND FERTILIZERS 
 
 FIG. 221. Disk harrow. 
 
 verizing the soil ; for as the disks cut the clods they also mix 
 the surface soil. The two sets of disks are set at an angle and 
 push the dirt away from the center; hence it is customary 
 
 in disking the 
 ground to lap one 
 half the distance 
 in order that the 
 ground may be 
 left more level. 
 The disk harrow 
 is often used to 
 loosen the ground 
 before plowing as 
 well as to cut 
 cornstalks and 
 rubbish to make them more easily covered. The disk harrow 
 is often used in place of the plow in preparing the ground 
 in the spring for oats when they follow corn in rotation. 
 When spring plowing is delayed, it is often advisable to go 
 over the ground with 
 the disk harrow so as 
 to loosen the surface 
 and prevent evapora- 
 tion. 
 
 544. Use of the Roll- 
 er. It is seldom neces- 
 sary to use the roller 
 (Fig. 222) after spring 
 plowing in humid cli- 
 mates. If the soil is moist or the plowing is followed by 
 rains, a good contact is formed between the plowed ground 
 and the subsoil, and capillarity is renewed. In dry weather 
 
 FIG. 222. Roller. 
 
TILLAGE 
 
 471 
 
 or in case much organic matter is plowed under, the heavy 
 roller may be useful in pressing the plowed ground down 
 upon the soil beneath. 
 As a means of break- 
 ing the clods and pul- 
 verizing the soil the 
 roller is not very effi- 
 cient. When used it 
 should be followed by 
 the harrow to restore 
 the surface mulch. 
 
 The plank drag (Fig. 
 223) is frequently used FlG ' 223 ' ~ plank drag " 
 
 by gardeners to break the clods and make the soil fine. 
 
 545. Intertillage. Some crops, like corn, are intertilled, 
 or cultivated between the rows, during at least a part 
 of the growing season. Many implements have been 
 
 devised for this pur- 
 pose, the kinds vary- 
 ing from the one-horse 
 cultivator to the two- 
 row riding corn culti- 
 vator (Fig. 224). The 
 cultivating teeth of 
 these implements are 
 of all sizes and forms. 
 The cultivation should 
 
 FIG. 224. -Two-row riding corn cultivator. ^ fallow. It should 
 
 be frequent enough to maintain a good soil mulch. The 
 scil should be left level, and all ridging should be avoided, 
 as uneven ground exposes more surface for evaporation of 
 water. 
 
472 SOILS AND FERTILIZERS 
 
 EXERCISES 
 
 Ex. 334. Describe the effect of tillage in pulverizing the soil. Why 
 can plants obtain more food from a fine-grained soil ? In what ways 
 is aeration of the soil by means of tillage beneficial ? 
 
 Ex. 335. Explain how tillage and pulverizing increase the water- 
 holding capacity of soils. 
 
 Ex. 336. Fill two cans to within one inch of the top with moist 
 soil. On top of the soil in one can place one half inch of fine dry earth. 
 Place the cans on opposite pans of a balance and add weights or sand 
 to the pan on the lighter side until the indicator of the balance is at 
 zero. Note which can loses moisture more quickly. Explain. Will a 
 layer of straw do the same thing ? How is the soil mulch prepared 
 and maintained? Explain the effect of late fall plowing and early 
 spring plowing upon the moisture content of the soil. Why should 
 the surface of irrigated soil be cultivated ? 
 
 Ex. 337. Why should all weeds be destroyed? How do they 
 affect the water supply of the plant ? The food supply ? The yield of 
 the crops ? Would it pay to cultivate if there were no weeds ? 
 
 Ex. 338. Under what climatic conditions is dry farming practiced ? 
 How is it conducted ? Explain use of the subsurface packer. 
 
 Ex. 339. What is meant by summer fallowing? Is it advisable 
 in humid climates? What is the danger connected with it? Ex- 
 plain how short fallows might be used to advantage. 
 
 Ex. 340. Compare the breaking plow and the stubble plow. How 
 does the disk plow work? Why should the plow be made to pulverize 
 the soil as much as possible? What determines the depth to plow? 
 How can you deepen a clay soil which has always been shallow plowed ? 
 Why is deep plowing more expensive than shallow plowing? What 
 is a good depth to plow clay soils? What is meant by subsoil plow- 
 ing ? Why is it difficult to tell when to plow stiff clay soils ? 
 
 Ex. 341. What operation usually follows plowing? Name dif- 
 ferent kinds of harrows used in your neighborhood. Note all the 
 different uses made of the disk harrow. 
 
 Ex. 342. Is it often advisable to use the roller ? What should be 
 done immediately after rolling? Explain the use of the plank drag. 
 Describe different kinds of cultivators for corn. State some general 
 rules for jntertillage. Why is level cultivation best ? 
 
CHAPTER LV 
 KEEPING THE SOIL SWEET 
 
 546. Soil Acidity. Many soils fail to produce good 
 crops because they are acid, or sour. It was formerly 
 supposed that only low-lying or marshy soils ever became 
 sour, but it is now known that there are large areas of up- 
 lands where an acid condition of the soil exists. These 
 acid soils are widely distributed and are found in all parts 
 of the world, but especially in humid climates. 
 
 547. Cause of Acidity. Soil acidity is due to a lack of 
 limestone (calcium carbonate) in the soil. Acids are con- 
 stantly being formed in the soil, and unless these acids are 
 neutralized they cause the soil to become sour. When the 
 soil contains an abundance of calcium carbonate these 
 acids are neutralized as rapidly as they are formed, but 
 in this action, of course, some of the carbonate itself is 
 destroyed. The more thorough the cultivation the more 
 rapidly organic matter is oxidized and acid substances are 
 formed, and consequently the greater is the destruction of 
 the limestone in the soil. Moreover, the growing crop uses 
 some of the calcium of the limestone in making its growth 
 and thus removes it from the soil. Manures and fertilizers 
 also temporarily produce acidity of the soil and thus destroy 
 the limestone, and, finally, large quantities of calcium car- 
 bonate are removed from the soil in the drainage water. 
 The carbonic acid of the soil water acts upon the limestone, 
 
 473 
 
474 
 
 SOILS AND FERTILIZERS 
 
 forming calcium bicarbonate (119), as is shown by the hard- 
 ness of the drainage water in limestone countries. 
 
 548. Soil acidity is injurious to most of the crops that 
 are grown in ordinary farming or gardening. Clover, alfalfa, 
 and other important legumes are particularly sensitive to 
 the lack of limestone in the soil. This is due in part to the 
 
 fact that these legumes 
 use comparatively large 
 quantities of calcium 
 during their growth, 
 but apparently it is 
 true also that the bac- 
 teria that enable these 
 legumes to fix the free 
 nitrogen of the air do 
 not thrive in a sour 
 soil . At any rate these 
 legumes will not grow 
 in acid soils, and ordi- 
 nary farming cannot be successful without the growth of 
 legumes to furnish a cheap supply of nitrogen by the fixa- 
 tion of that element from the atmosphere. 
 
 549. Acidity Prevents Nitrification. It has been shown 
 that the process of nitrification in the soil is essential to the 
 successful production of the common field crops. One of 
 the requirements for nitrification is that there is present 
 in the soil some basic substance with which the nitrous 
 acid may unite as rapidly as it is formed. Limestone is the 
 most important basic substance in the soil, and when it is 
 exhausted the soil becomes acid and nitrification is no longer 
 possible. The bacteria that cause denitrificatioh, on the 
 other hand, seem not to be sensitive to acidity ; hence this 
 
 FIG. 225. Effect of limestone on growth of 
 sweet clover. The strip in center received no 
 limestone. 
 
KEEPING THE SOIL SWEET 475 
 
 injurious action is likely to be accelerated in sour soils. It 
 is of utmost importance, therefore, that acidity of the soil 
 should be corrected. 
 
 550. How to Recognize a Sour Soil. The character of 
 the vegetation gives some indication as to whether or not 
 the soil is acid. Where such plants as common sorrel, 
 horsetail, rushes, and mosses take possession of the land, 
 it is a strong indication of acidity, because these plants 
 can withstand a large amount of acid and hence persist 
 after the soil has become too sour for the growth of more 
 desirable plants. Sometimes an acid soil becomes so covered 
 with sorrel as to give a reddish tinge to the entire field. 
 
 The persistent failure of clover is an indication of soil 
 acidity, while a good growth of clover shows that the soil 
 contains sufficient limestone. On acid soils the clover fre- 
 quently starts growth with promise in the early spring, 
 but later becomes sickly in appearance and finally dies out 
 completely. Such behavior is practically always due to a 
 sour condition of the soil. 
 
 551. The Litmus Test for Acidity. One of the best 
 methods of testing the soil for acidity is known as the litmus 
 paper test, In the laboratory the test may be applied by 
 moistening the soil with distilled water and placing a piece 
 of blue litmus paper on the moist mass. If the litmus paper 
 turns pink within ten minutes, the soil is acid. 
 
 Owing to the difficulty of obtaining pure distilled water 
 it is generally best to make the test on the moist soil direct 
 from the field. A handful of the soil is pressed into a ball, 
 which is then broken in two, and the litmus paper is placed 
 between the two halves of the ball. After ten minutes the 
 paper is examined. 
 
 Care should be exercised hi using the litmus paper, as 
 
476 
 
 SOILS AND FERTILIZERS 
 
 fit"\ WF 
 
 the perspiration of the hands is usually acid in reaction. 
 The safest way is to use a pair of small forceps in handling 
 the paper. Only a sensitive litmus paper, such as is used 
 in the chemical laboratory, should be employed in making 
 the test. The cheap blue litmus papers so often found in 
 the drug stores are strongly alkaline and will not change 
 color even in soil which is sour enough to prevent entirely 
 the growth of clover. 
 
 552. The Truog test for acidity consists in mixing the 
 soil to be tested with a small quantity of calcium chloride 
 and a very little zinc sulphide. Water is added and the 
 
 mixture is heated to 
 boiling. A strip of lead 
 acetate paper is held 
 over the mouth of the 
 flask for two minutes 
 while the boiling pro- 
 ceeds. If the soil is 
 acid it reacts on the 
 zinc sulphide and forms 
 hydrogen sulphide, 
 which darkens the lead 
 acetate paper (87). If 
 no acid is present in 
 the soil no darkening 
 of the paper will occur. When the directions are carefully 
 followed the color of the lead paper gives some idea of the 
 degree of acidity in the soil. A small outfit including an 
 alcohol lamp for heating water so that the test may be used 
 in the field is now on the market (Fig. 226) . 
 
 553. Hydrochloric acid is used to show the presence of 
 an abundance of limestone in the soil. A handful of soil 
 
 FIG. 226. Apparatus for Truog test. 
 
KEEPING THE SOIL SWEET 
 
 477 
 
 is pressed into a ball, and then a depression is made in it to 
 hold a little dilute hydrochloric acid. If a considerable 
 amount of limestone is present, it will be shown by efferves- 
 cence caused by the action of the acid on the calcium car- 
 bonate. A decided effervescence indicates that the soil 
 contains sufficient limestone for all purposes. The small 
 amount of air which is forced out of the soil by the liquid 
 must not be mistaken for effervescence from the carbonates. 
 This test is of limited application only, since a soil may be 
 neutral in reaction and able to produce clover and yet not 
 contain enough carbonate to give a noticeable evolution of 
 carbon dioxide. 
 
 554. Correcting Acidity. When any of the tests indicate 
 that the soil is sour, it is necessary to add to it some substance 
 that will neutralize and thus destroy the acid . The cheapest 
 material that can be 
 used for this purpose 
 is ordinary limestone. 
 The stone is pulverized 
 by crushers (Fig. 227) 
 and rollers until it is 
 fine enough to be ap- 
 plied with a lime drill. 
 A powder that will all 
 pass through a sieve 
 having ten meshes to 
 the linear inch is suf- 
 ficiently fine, although 
 the finer the stone the quicker it will act on the soil. 
 
 The ordinary application of ground limestone to acid 
 soils is two tons to the acre. It is best applied by means of 
 especially devised lime spreaders (Fig. 228) which can be set 
 
 FIG. 227. A small portable pulverizer for 
 ' grinding limestone. 
 
478 
 
 SOILS AND FERTILIZERS 
 
 to distribute from five hundred pounds to four or five tons 
 to the acre. A manure spreader may be used by covering 
 the bottom with straw and placing the powdered limestone on 
 top, or a skilled worker may even spread it from the wagon 
 
 FIG. 228. Applying ground limestone with a spreader. 
 
 by means of a shovel. If much limestone is to be used, 
 the special spreader will soon pay for itself. 
 
 It sometimes happens that a farm that has an acid soil 
 also has outcroppings of limestone. Small portable lime- 
 stone crushers are on the market at a low price, which make 
 it possible under such conditions for the farmer to crush his 
 own limestone at a small expense. It is to be noted that 
 even in limestone sections acid areas are frequently found, 
 especially on the high lands that have been under cultiva- 
 tion for a long period. 
 
 555. Other Forms of Lime. Although under ordinary 
 circumstances ground limestone is the cheapest and best 
 material to use for correcting the acidity of soils, it may 
 
KEEPING THE SOIL SWEET 479 
 
 happen that the land is so far removed from any source 
 of limestone that the freight charges are excessive. In such 
 a case it might be more economical to use quicklime (CaO) 
 in place of the limestone. In burning 100 pounds of calcium 
 carbonate 56 pounds of lime are produced ; but the latter has 
 the same power to neutralize acids as the former. Thus it 
 will be seen that not much more than one ton of quicklime 
 will do the same work as two tons of limestone. 
 
 Hydrated lime, which is merely another name for slaked 
 lime (Ca(OH) 2 ), is often recommended for use on the soil. 
 It is effective in neutralizing acidity, but is usually too high 
 in price for that purpose. 
 
 Air-slaked lime (115) is formed when quicklime is exposed 
 to the air. If it stands for a long time the calcium is all 
 converted into the carbonate, with the result that the ma- 
 terial is practically the same as very finely ground limestone. 
 One ton of quicklime is equivalent in neutralizing power 
 to 2640 pounds of hydrated lime, or 3570 pounds of carbonate 
 of lime; and these relations should be kept in mind when 
 determining which substance is most economical to buy. 
 
 556. Marl. In many places beds of marl of considerable 
 size are found. Most of the marls are formed from shell 
 deposits, and consist of carbonate of lime of more or less 
 purity. As marl is practically the same as ground lime- 
 stone, it has the same effect upon the soil, and is a convenient 
 form in which to use lime when obtainable at reasonable 
 cost. Some of the European/ marls contain appreciable 
 quantities of potash and phosphoric acid as well, but the 
 American marls are of value only for the lime they contain. 
 
 557. When to Apply Limestone. The principal reason 
 for using limestone or the other forms of lime is to enable 
 the soil to produce clover or other legumes; consequently 
 
480 SOILS AND FERTILIZERS 
 
 the limestone should be used far enough in advance of the 
 leguminous crop to insure the neutralizing of the acidity 
 of the soil before the legume is planted. If corn is grown 
 in the rotation, it is advisable to spread the limestone on 
 the ground immediately after plowing, and to harrow it in. 
 In this way the limestone is thoroughly mixed with the 
 soil and has time to destroy the acids before the legume 
 is seeded. 
 
 558. Field Test with Limestone. The tests for acidity 
 already described are all good in their way ; but the impor- 
 tance of having right conditions for the growth of clover is 
 so great that a practical test of limestone in the field should 
 be made in every case where the growth of clover is unsatis- 
 factory. A strip across the field should be dressed with 
 limestone at the rate of forty pounds to the square rod, 
 and its effect upon the growth of clover noted. 
 
 559. Lime Improves the Physical Condition of Soil. 
 Lime also has a very marked effect on the physical condition 
 of the soil. When added to a sandy soil it tends to make 
 the soil more compact by partially cementing together the 
 particles of sand and thus making the soil capable of retain- 
 ing larger quantities of water. When used on clay lands, 
 on the other hand, lime makes the soil more mellow. A clay 
 soil containing very little lime is made fine with the greatest 
 difficulty; it adheres to the implements used when wet, 
 and cracks when allowed to dry. A soil rich in lime crumbles 
 more easily than one lacking it, is readily brought into good 
 tilth, and does not adhere to any appreciable extent to the 
 implements. The addition of lime to a soil containing much 
 clay makes the soil more friable, makes it possible for the 
 rains to percolate more easily through the soil, and over- 
 comes the danger of puddling. The puddling of clay soils 
 
KEEPING THE SOIL SWEET 481 
 
 is due to the fact that the clay is composed of very small 
 granules which fit so closely together that the water cannot 
 pass between. When lime is added to the soil a number 
 of these small particles become cemented together to form 
 a much larger granule, and as the granules increase in size 
 the spaces between them also become larger. 
 
 This effect of lime may readily be shown by taking a 
 sample of clay, adding a little water, working it thoroughly, 
 and then allowing it to dry. As a result of this treatment 
 it becomes as hard as a brick. If to another portion of the 
 clay a little lime is added (say one per cent) and this is mois- 
 tened, mixed thoroughly, and allowed to dry, it will be found 
 that a mere touch will cause it to crumble to pieces. This 
 granulated condition of clay soils, so easily accomplished 
 by liming, is not readily destroyed but will last for some 
 years. This mechanical effect on soils is more marked 
 in the case of quicklime than it is with limestone. 
 
 560. Lime Makes Potential Food Available. Lime is 
 useful in liberating the unavailable food materials of the 
 soil. Most of the potassium of the soil, for instance, is 
 locked up in insoluble silicates and is not available to plants. 
 Lime decomposes some of these silicates and converts the 
 potassium into forms that the crop can use. Experiments 
 have proved that when lime is applied to a soil originally 
 poor in this substance, the plants grown are not only richer 
 in lime but also in potash. The use of lime then may for 
 a time have a similar effect to that of potash-containing 
 manures, but it must be remembered that the lime does not 
 supply potash ; it merely makes available the potash that is 
 present in the soil; and if the store of potash originally 
 present is small, it will probably need liberal potash manur- 
 ing at an earlier date because of liming. 
 
 EV. CHEM. 31 
 
482 SOILS AND FERTILIZERS 
 
 Lime is also beneficial in preventing the formation of the 
 very insoluble iron and aluminum phosphates, or in chang- 
 ing them to calcium phosphate if they are already formed. 
 Another effect of adding lime or limestone to an acid soil 
 is to make the phosphates of the soil available. 
 
 561. Lime not a Universal Remedy. So much has been 
 written about the use of lime that there is danger of creat- 
 ing the impression that lime or limestone is the universal 
 remedy for all unproductive soils, and that no other treat- 
 ment than liming is necessary. It must be remembered 
 that lime adds no plant food save calcium to the soil, but 
 simply brings about conditions that enable the crop to use 
 larger quantities of the food already present, so that if used 
 alone it makes the exhaustion of the soil more rapid. Lime 
 can in no way take the place of good tillage, drainage, manure, 
 or fertilizers. There is an old saying that " lime makes the 
 father rich, but the son poor," and this is undoubtedly true 
 if lime is used alone. It has, however, a legitimate place 
 in agriculture, and if used in connection with green crops, 
 barnyard manure, and commercial fertilizers will in many 
 cases produce beneficial results. 
 
 562. Acid Resistant Plants. Not all crops are seriously 
 injured by an acid condition of the soil. Such plants as 
 the cranberry and blueberry actually require an acid soil 
 and will not grow on one that is alkaline. Other crops, 
 while not preferring an acid soil, are injured but little by 
 acidity. The potato may be grown very successfully on an 
 acid soil and under such conditions is less subject to the 
 attacks of the scab fungus than when grown in neutral or 
 alkaline soils. The potato scab fungus grows more readily 
 in an alkaline soil ; consequently lime should never be added 
 to the soil immediately preceding the potato crop. 
 
KEEPING THE SOIL SWEET 483 
 
 EXERCISES 
 
 Ex. 343. What is meant by a sour soil ? What is the cause /of 
 acidity in soils? What effect does soil acidity have on plant growth? 
 What plants are especially sensitive to acidity? What effect does 
 acidity have on the fixation of nitrogen? How does acidity affect 
 nitrification? Why is limestone necessary for nitrification? 
 
 Ex. 344. Explain how the character of the vegetation indicates 
 whether or not soil is acid. See if you can find sorrel growing abundantly 
 anywhere in the vicinity of the school. What should you suspect re- 
 garding the soil when clover fails ? 
 
 Ex. 345. Test a number of soils with litmus paper (551). Are any 
 of the soils acid ? Mix a little limestone thoroughly with the soil and 
 make the litmus paper test again on the following day. Give the result. 
 Why should the litmus paper never be handled with perspiring fingers? 
 Are there any acid soils on your home farm ? 
 
 Ex. 346. Test a soil for acidity by the Truog test as follows: 
 (1) Prepare the lead acetate paper by dipping a piece of white filter 
 paper into a 10 per cent solution of lead acetate. Spread the paper 
 on a pane of glass to dry. (2) Prepare the zinc sulphide and calcium 
 chloride mixture by dissolving 50 grams of neutral calcium chloride 
 in 250 cc. of water, and then adding 5 grams of finely pulverized zinc 
 sulphide. (3) To perform the test place 10 grams of soil in a boiling 
 flask, adding 5 cc. of the zinc sulphide-calcium chloride mixture and 
 95 cc. of distilled water. Heat to boiling and boil one minute, then 
 place a strip of the lead acetate paper over the mouth of the flask, and 
 boil two minutes. A darkening of the acetate paper indicates the 
 presence of acid, the degree of acidity being approximately shown by 
 the depth of the color. What causes the paper to darken? Why does 
 it not change color if the soil is neutral ? Why is it essential that the 
 calcium chloride should be neutral ? 
 
 Ex. 347. Test some soils for limestone (553) . Is limestone present ? 
 Is this test of general application? Would there be any need of liming 
 a soil that showed the presence of limestone by this test? 
 
 Ex. 348. What method is used to correct the acidity of soils? 
 How much limestone is ordinarily used to the acre ? How finely should 
 the limestone be pulverized? How may it be applied to the soil? 
 
484 SOILS AND FERTILIZERS 
 
 What other forms of lime are used to correct acidity ? What is marl ? 
 Is it suitable for use on the soil ? 
 
 Ex. 349. What is the principal reason for using limestone ? Why 
 should it be used in advance of clover ? Why is it advisable to apply 
 it to the ground that has been plowed for corn? How should you con- 
 duct a field test with limestone ? Is such a test advisable ? 
 
 Ex. 350. Take a handful of wet clay and thoroughly knead it 
 into a ball and dry it in the oven. Add one per cent of lime to another 
 handful of the clay and knead it into a ball and dry it in the oven. 
 How do the two samples behave when broken with a hammer ? What 
 effect does lime have on the physical condition of soils ? 
 
 Ex. 351. Place a tablespoonful of clay soil in each of two tall 
 glass cylinders or bottles. Shake the cylinders to get the clay in sus- 
 pension. To one cylinder add a little slaked lime and stir. What 
 difference is there in the behavior of the clay in the two cylinders? 
 How do you account for it ? Why do clays puddle ? How does lime 
 prevent puddling ? 
 
 Ex. 352. What effect does lime have on the potential plant food 
 of the soil ? Why do acid soils seem to contain more phosphorus after 
 liming ? In what form is the phosphate in acid soils ? If a farmer uses 
 lime alone, what effect will it eventually have on the fertility of his land ? 
 
 Ex. 353. Are all plants injured by acidity? Are there any that 
 prefer an acid soil ? Why should care be used in liming potato soils ? 
 
CHAPTER LVI 
 ORGANIC MATTER 
 
 563. Old and New Soils Compared. If a soil that has 
 grown crops continuously for many years without the addi- 
 tion of plant food is compared with an adjacent plot of virgin 
 soil, a marked difference will be found in the amounts of 
 organic matter that the two soils contain. Soils that have 
 been under cultivation for periods of twenty to thirty years 
 with no provision for maintaining the organic matter are 
 found to contain less than two thirds as much organic matter 
 as the original soil. There can be no doubt that, in a great 
 many instances, the loss of fertility is due to the rapid 
 decrease in the amount of organic matter. 
 
 564. Organic matter in soils is largely derived from the 
 remains of the plants that have grown on them. Under 
 natural conditions the entire plant becomes a part of the soil 
 and furnishes it with an abundance of organic matter. 
 When the crop is removed from the fiejd, only the stubble 
 and roots remain to supply the vegetable matter, but the 
 quantity supplied in this way is not sufficient for the best 
 results. Some of the organic matter of the soil is of animal 
 origin, but the amount so derived is insignificant as compared 
 with that derived from vegetation. 
 
 Organic matter exists in the soil in all stages of decomposi- 
 tion. Decay begins as soon as the plants die or other organic 
 
 485 
 
486 SOILS AND FERTILIZERS 
 
 matter is added to the soil, and is due to the action of the 
 bacteria that are always present in the soil. The soil con- 
 tains, therefore, fresh vegetable material that has not begun 
 to decay ; partially decayed material that still retains a part 
 at least of the original form ; and organic matter that has 
 so completely decomposed that it has entirely lost the physi- 
 cal structure of the material from which it was derived. 
 The black waxy material coating the soil grains, giving the 
 dark color to some soils, is organic matter in a very advanced 
 state of decomposition, and is known as humus. The term 
 humus is often used as a synonym of the term organic 
 matter. Such usage, however, is incorrect, as much more 
 than the humus is included in organic matter. All forms 
 of organic matter are of importance in the soil ; but prob- 
 ably that part which is undergoing active decay is the most 
 beneficial. 
 
 565. Organic Matter Increases the Amount of Soil 
 Water. Organic matter has a high absorptive power for 
 water. A sponge, for instance, which is a good example 
 of organic matter, will absorb and retain more than ten 
 times its own weight of water. Cellulose and other forms 
 of vegetable matter will hold practically the same amount 
 of water. It will readily be seen, therefore, that the more 
 organic matter the soil contains the greater will be its power 
 to store water. In one experiment the addition of one 
 per cent of organic matter to the soil increased its water- 
 holding capacity a little over eight per cent. The water 
 retained by the organic matter is in large part so loosely 
 held that it can be utilized by growing plants. The follow- 
 ing table gives the amount of water held in a cubic foot 
 of three different soils with varying amounts of organic 
 matter : 
 
ORGANIC MATTER 487 
 
 KIND OF SOIL 
 
 POUNDS OF WATER IN 
 ONE CUBIC FOOT 
 
 Sand 
 
 27.3 
 
 Sandy loam 
 
 38.8 
 
 Loam 
 
 41.4 
 
 
 
 It will be seen that the quantity of water increases with 
 the amount of organic matter present, the sand containing 
 the least, and the loam, which has the largest percentage of 
 organic matter, containing much inore. It is evident from 
 the above that one of the best ways to enable the soil to 
 store water from the spring rains for the use of the growing 
 crop during the hot summer months is to keep the soil well 
 supplied with organic matter. 
 
 566. Organic Matter a Storehouse for Plant Food. 
 The organic matter of the soil contains part of the plant 
 food that was utilized by plants formerly grown on the 
 soil. It has been shown that most of the nitrogen in the 
 soil is present in the organic matter and that this becomes 
 available through the gradual decay of the plant. It is fortu- 
 nate that most of the nitrogen is stored in organic matter ; 
 for if it were all immediately converted into nitrates, there 
 would be great loss by leaching, since the nitrates are very 
 soluble and the soil has little power of retaining them. 
 
 567. Organic Matter Makes Potential Food Available. 
 The presence of decomposing organic matter in the soil is 
 an important factor in making the mineral elements of plant 
 food available. During decay certain acids, such as lactic, 
 acetic, and nitrous acids, are produced, and these undoubtedly 
 have a solvent action on the mineral matters of the soil, 
 tending to make them more available to the plant. Perhaps 
 
488 SOILS AND FERTILIZERS 
 
 quite as important a factor is the large amount of carbonic 
 acid formed during the prpcess of decay. This carbonic 
 acid dissolved in the soil water is of prime importance in 
 the production of soluble plant food, and it also has a bene- 
 ficial effect on the physical condition of the soil, especially 
 if the soil contains a large amount of clay. 
 
 568. Organic Matter Improves Soil Texture. Organic 
 matter is also valuable in improving the physical condition 
 of the soil. Sandy soils are made more compact by its 
 presence and better able to supply a crop with food and 
 moisture. Clay soils, on the other hand, are made more 
 mellow by the addition of organic matter. Clay is likely 
 to become too compact unless there is a certain amount of 
 organic matter present to prevent it. The better tilth of a 
 soil due to the presence of organic matter facilitates drain- 
 age and ventilation, both of which are necessary to the pro- 
 motion of soil sanitation. 
 
 Organic matter is an essential part of all true soils. In 
 most soils there is a marked difference in color and texture 
 between the surface, or true, soil and the subsoil. The sur- 
 face soil is darker in color, less compact, and more easily 
 worked by tillage implements than is the subsoil. The 
 difference is due largely to the greater amount of organic 
 matter contained in the surface soil. The darker color of 
 the soil is due largely to humus, the very black soils con- 
 taining large quantities of humus. Organic matter, more 
 especially humus, also affects the temperature of the soil, for 
 the darker-colored soils absorb more heat from the sun's 
 rays than do the lighter-colored ones. 
 
 569. Loss of Organic Matter. Investigations have shown 
 conclusively that as the organic content of the soil is de- 
 creased by constant cultivation and cropping, the nitrogen 
 
ORGANIC MATTER 
 
 489 
 
 content of the soil, the amount of moisture that it contains, 
 and the crop production are likewise decreased. 
 
 All the methods so far discussed for making potential 
 plant food available tend to decrease the amount of organic 
 matter in the soil. Tillage, drainage, bare fallowing, and 
 liming the soil all increase the amount of food available to 
 the crop, because they present ideal conditions for the de- 
 composition of organic matter in the soil ; but dependence 
 upon these methods alone will eventually result in injury 
 through loss of organic matter. The loss of nitrogen and 
 organic matter is strikingly shown in the following table : 
 
 
 NATIVE SOIL 
 PER CENT 
 
 CULTIVATED 23 
 YEARS 
 PER CENT 
 
 Loss 
 PER CENT 
 
 Organic matter .... 
 
 3.97 
 
 2.59 
 
 1.38 
 
 Nitrogen 
 
 0.36 
 
 0.19 
 
 0.17 
 
 Capacity to hold water 
 
 62.00 
 
 54.00 
 
 8.00 
 
 The foregoing statements should not be construed as argu- 
 ments against tillage, drainage, and liming, because the de- 
 struction of organic matter is an essential part of good farm- 
 ing. It is the farmer's business to bring about in the soil 
 the proper conditions for the rapid decay of organic matter 
 so that the crops may utilize the plant food therein contained. 
 However, if he is to have continued success in producing 
 crops, the farmer must at the same time return organic 
 matter to replace that which has been destroyed. 
 
 670. Restoring Organic Matter. Under farm conditions 
 where most of the crops must be removed from the field, 
 the maintenance of the supply of organic matter is a serious 
 problem. A certain amount of organic matter is left behind 
 in the stubble and the roots. This material should be utilized 
 
490 SOILS AND FERTILIZERS 
 
 to the fullest extent. The practice of burning over the 
 field to destroy the stubble before plowing is to be condemned, 
 because large quantities of organic matter are destroyed in 
 this way. The straw, cornstalks, and any similar material, 
 if not used for feeding, should be incorporated into the soil. 
 The burning of any of the organic matter of the farm or 
 garden is never justified except when necessary to prevent 
 the spread of plant diseases. 
 
 Large amounts of organic matter may be restored to the 
 soil by a careful use of the stable manure. The manure 
 from the domestic animals contains nearly one half of the 
 organic matter of the feeds, the rest having been oxidized 
 in the animal body and given off largely as carbon dioxide 
 and water. If the manure is properly handled, therefore, 
 about one half of the organic matter in all feeds used may 
 be added to the soil. The precautions necessary to obtain 
 these results are discussed in Chapter LVIII. 
 
 The plowing under of grass sods adds organic matter to 
 the soil. Such grasses as Kentucky blue grass, especially, 
 fill the soil full of small, fibrous roots and when the sod is 
 plowed the roots and the stubble begin to decay. In one 
 instance the first six inches of soil in a field of timothy and 
 redtop were found to contain nearly four tons of roots and 
 stubble to the acre. Pasture lands, if well fertilized so as 
 to grow an abundance of grass, may be used as a means of 
 maintaining the organic matter of the farm. 
 
 571. Green Manuring. On many farms even the com- 
 plete utilization of the various methods outlined in the last 
 section will not suffice to maintain the necessary amount of 
 organic matter in the soil for the production of maximum 
 crops. Under such conditions it is necessary to grow a 
 crop for the express purpose of plowing it under to increase 
 
ORGANIC MATTER 
 
 491 
 
 FIG. 229. Plowing under a green manure 
 crop. 
 
 the organic matter of the soil. Such a practice is known as 
 green manuring. Plowing under green crops raised for 
 that purpose is one of the oldest means of improving the 
 fertility of the soil. It was advocated by Roman writers 
 more than two thousand years ago, and has been in more 
 or less common use among progressive farmers ever since. 
 
 The value of green 
 manuring depends pri- 
 marily on the fact that 
 it increases the amount 
 of organic matter in the 
 soil. Several kinds of 
 crops may be used as 
 green manures, but the 
 most valuable for this 
 purpose are the legumes. 
 The discovery that the leguminous plants can, through 
 the nodule-forming bacteria, fix the free nitrogen of the air, 
 has thrown a new light on green manuring and the plants 
 adapted to this purpose. The legumes have all the advan- 
 tages of the other plants in providing organic matter, and at 
 the same time they increase the amount of nitrogen in the soil. 
 They are, as a rule, deeper-rooted plants and are supposed 
 to bring up mineral food from the subsoil, and leave it where 
 it will be within reach of the more shallow-rooted plants. 
 Of the legumes the crops most often recommended are red 
 clover, sweet clover, cowpea, crimson clover, the lupines, 
 soy bean, and the ordinary field bean, and field pea. Of 
 these, red clover is probably the one most generally used. 
 
 572. Green Manuring and Type of Farming. Such crops 
 as red clover, which make the best green manures, also have 
 great value as feeds for live stock, and it may be found more 
 
492 
 
 SOILS AND FERTILIZERS 
 
 profitable to feed them to animals and return the manure 
 to the soil than it is to turn them under. But even on stock 
 farms it is often advisable to plow under the second growth 
 of clover instead of cutting it for hay. 
 
 In any system of farming in which the crops are sold from 
 the farm, some provision for green crops to plow under is 
 absolutely necessary, and the rotation used should include 
 a green manure crop. The increase in the other crops from 
 this practice will more than make up for the fact that there 
 is no crop to sell from the green manure field. 
 
 573. Catch Crops for Green Manuring. Where it is in- 
 advisable to devote an entire season to the growth of a 
 crop for green manuring, good results may often be ob- 
 tained by the use of 
 what is known as a 
 catch crop, or a crop 
 grown between two 
 main crops. Rye is 
 often planted in the 
 corn land at the time 
 of the last cultivation 
 and allowed to grow 
 until the ground is 
 plowed the following 
 spring, thus adding or- 
 ganic matter to the 
 soil. In the southern states crimson clover and other leg- 
 umes are used in a like manner, but in the north the legumes 
 are uncertain as catch crops. A mixture of rye and hairy 
 vetch is very satisfactory as a catch crop after corn. The 
 use of cover crops in orchards is another example of a 
 catch crop. 
 
 FIG. 230. Crimson clover as an orchard 
 cover crop. 
 
ORGANIC MATTER 493 
 
 574. Danger from Green Manuring. While green manur- 
 ing is a valuable method of increasing the humus supply 
 of the soil, it is not unattended by danger. In a dry season, 
 for instance, the growth of a crop to plow under may result 
 in lowering the moisture content of the soil to a point that 
 is detrimental to the succeeding crop. There is also danger 
 in such a season that there may not be sufficient moisture 
 in the soil to bring about the decomposition of the organic 
 matter that is turned under, the result being serious injury 
 to the physical condition of the soil. Such injury, however, 
 does not frequently occur, and its bad effects are only tem- 
 porary. If a crop is plowed under during a dry season, the 
 ground should be rolled with a heavy roller so as to renew 
 the capillary movement of moisture between the surface 
 and the subsoil. 
 
 EXERCISES 
 
 Ex. 354. If possible, obtain a sample of soil from the center of a 
 field that has been under cultivation for a long time, and another 
 sample from the fence row of the same field. What difference do you 
 note in the two samples? Does the soil from the fence row contain 
 more organic matter than the other ? What is the source of the organic 
 matter in soils? What is meant by humus? Is humus identical with 
 organic matter? What gives the black color to some soils? 
 
 Ex. 355. Weigh a large sponge after it has been thoroughly dried. 
 Now dip the sponge in water, hold it up until dripping has ceased, 
 and weigh it again. How many times its own weight of water will the 
 sponge hold? What can you say about the power of organic matter 
 to increase the water-holding capacity of the soil ? 
 
 Ex. 356. Determine the water-holding capacity of a soil as de- 
 scribed in Ex. 318. Add to another sample of the soil one per cent of 
 ground moss or wheat bran and determine the water-holding capacity. 
 How much does the organic matter increase the water in the soil ? 
 
 Ex. 357. Explain what is meant by the statement that organic 
 matter is a storehouse of plant food. How is this plant food made 
 
494 SOILS AND FERTILIZERS 
 
 available? How does organic matter make the mineral food of the 
 soil available ? 
 
 Ex. 358. Note the difference in appearance between the surface 
 soil and the subsoil. What makes the surface soil darker in color and 
 more friable than the subsoil ? What effect does organic matter have 
 on the texture of a sandy soil ? Of a clay soil ? 
 
 Ex. 359. Explain how organic matter is lost from the soil. Show 
 how some of it may be restored by the plant residues, by the use of 
 stable manure, and by plowing under sods. 
 
 Ex. 360. What is meant by green manuring? Is it a modern 
 practice ? What advantages have the legumes as green manure crops ? 
 What are the crops most commonly used as green manures? In what 
 type of farming is green manuring desirable ? 
 
 Ex. 361. What are catch crops and how may they be used to 
 increase the organic matter of the soil? Give an example of the use 
 of catch crops. Are there any dangers connected with green manur- 
 ing? Why should the roller be used when a heavy crop is plowed 
 under? 
 
CHAPTER LVII 
 ROTATION OF CROPS 
 
 575. Origin of Rotations. It is the common knowledge 
 of farmers in those parts of the world where the land has 
 been cultivated for a long time that the fertility of the 
 soil is maintained for a much longer time by growing a variety 
 of crops than by producing one crop continuously. The 
 adoption of a system of rotation of crops has been the out- 
 growth of accident rather than the result of an understand- 
 ing of its underlying principles. The system of alternating 
 years of bare-fallow and wheat may be said to be a two-year 
 rotation and was the first to be adopted. History teaches 
 us that this was later followed by a three-year rotation con- 
 sisting of fallow, wheat, beans, or oats ; and still later, when 
 the value of clover and fallow crops became evident, this 
 rotation gave way to the now famous Norfolk rotation of 
 turnips, barley, clover, and wheat, the typical English 
 rotation. The Norfolk four-year course represents the 
 more common type the world over, consisting as it does of 
 cereals alternating with hoed crops and leguminous crops. 
 
 576. Plants Differ in Food Requirements. There are 
 many arguments to be advanced in favor* of growing a variety 
 of crops on the soil. The different crops vary in their food 
 requirements and in their ability to procure this food from 
 the soil. When one crop is grown continuously on the same 
 field, nearly all the plant food that it finds available may 
 become exhausted, although the soil will still contain large 
 quantities of food in forms that could be assimilated by plants 
 
 495 
 
496 SOILS AND FERTILIZERS 
 
 of another class. Some crops evidently require the mineral 
 matter to be in a readily soluble form, while others can use 
 less available forms of plant food. Other crops make an 
 especial drain on one element of plant food. By growing 
 plants with different food requirements the different ele- 
 ments are more evenly used, and there is less likelihood 
 of any one element becoming exhausted. 
 
 577. Plants Differ in Manner of Growth. The various 
 crops differ widely in their systems of root growth. Some 
 plants, as wheat, for example, are comparatively shallow- 
 rooted and must obtain their food from the surface soil. 
 Others, as the clovers, are very deep-rooted and are able 
 to use food that is not within the reach of the more shallow- 
 rooted plants. The deep-rooted plants are not only able 
 to procure the low-lying food, but probably bring a part 
 of it to the surface, where it remains, upon their decay, for 
 the use of the succeeding crop. It is well known that the 
 shallow-rooted plants do better when preceded by a deep- 
 rooted crop. 
 
 578. Rotation Improves the Soil and Economizes Labor. 
 When plants of different varieties are grown, the soil receives 
 different treatment for each crop ; so that the faults of one 
 year are likely to be corrected the next year. Thereby the 
 soil is kept in much better physical condition. As a general 
 rule the ground can be better prepared for the succeeding 
 crop if a judicious rotation is practiced than if the same crop 
 is grown continuously. The roots and stubble of clover 
 and grasses are also factors of some importance in improv- 
 ing the texture of the soil. Everything considered, the tilth 
 of the soil will be found to be much improved by rotation. 
 
 The growing of a variety of crops on the farm results 
 in economy of labor ; for the work of caring for them is dis- 
 
ROTATION OF CROPS 497 
 
 tributed throughout the season instead of all coming at one 
 time. In this way it is possible to secure cheaper and better 
 help than when only a few kinds of plants are raised. 
 
 579. Rotation Aids in Controlling Diseases, Insects, 
 and Weeds. Rotation also enables the farmer to control 
 plant diseases and to head off the injurious insects. Most 
 of the plant diseases are caused by bacteria or fungi that 
 live only on one genus of plants, or, at any rate, are more or 
 less restricted in the number of crops that they can use as 
 host plants. Where one crop is grown continuously, these 
 disease-producing fungi have every opportunity to be car- 
 ried over from one year to another. Most of the injurious 
 organisms are comparatively short-lived, so that if three 
 or four years of crops that are not suitable host plants inter- 
 vene, these organisms are likely to be destroyed. 
 
 In the same way it may be said that the injurious insects 
 are limited to certain plants for their food supply, and if 
 these plants are not grown on the field for a number of years, 
 the insects may die from starvation. These remarks do 
 not apply, of course, to those insects that have migratory 
 powers. There is no doubt that both diseases and insects 
 can be more easily suppressed if rotation is practiced. 
 
 Where one crop is grown continuously, the soil becomes 
 infested with certain weeds that are not destroyed by the 
 system of tillage necessary for that crop. The varying 
 treatment to which a soil is subjected in a well-planned rota- 
 tion makes this condition impossible ; so that the destruction 
 of weeds may be considered as one of the very desirable 
 results of a rotation of crops. In lands badly infested with 
 particular weeds it may even be desirable to omit from the 
 rotation for a while the crop whose growth presents the best 
 condition for the propagation of these weeds. 
 
 BV. CHEM. 32 
 
498 
 
 SOILS AND FERTILIZERS 
 
 CONTINUOUS CROPPING' 
 
 IZTPfRIOD 2QPERIOD 3? PERIOD 
 25.258U. I&75 BU. /0.43 8U 
 
 FIVE-YEAR ROTATION 
 
 1 5 J PERIOD ^ 9 PERIOD 39 PERIOD 
 3/ 89 BU. 30.82 BU 3I.O4 BU. 
 
 FlG. 231. Showing the advantage of rotation in corn production. 
 
 580. Rotation Increases Crop Yields. When crops are 
 grown in rotation, each crop gives a higher yield than when 
 it is grown continuously on the same field. This is true 
 whether the crops are grown with or without manures or 
 fertilizers. The effect of rotation upon the yield is shown 
 in the following table, which gives the average yield for the 
 third five-year period of three different crops grown con- 
 tinuously, and in a five-year rotation at the Ohio Experi- 
 ment Station. 
 
 CROP 
 
 UNFERTILIZED 
 
 STABLE 
 MANURE 
 
 COMMERCIAL 
 FERTILIZERS 
 
 Corn 
 Grown continuously . . 
 Grown in rotation . . . 
 
 10 bu. 
 31 bu. 
 
 24 bu. 
 50 bu. 
 
 39 bu. 
 54 bu. 
 
 Oats 
 Grown continuously . , 
 Grown in rotation . . . 
 
 22 bu. 
 33 bu. 
 
 35 bu. 
 42 bu. 
 
 45 bu. 
 53 bu. 
 
 Wheat 
 Grown continuously . .; 
 Grown in rotation . 
 
 6bu. 
 14 bu. 
 
 12 bu. 
 25 bu. 
 
 17 bu. 
 33 bu. 
 
ROTATION OF CROPS 499 
 
 581. Planning a Rotation. In planning a rotation the 
 farmer must be guided by his own conditions and his re- 
 quirements in the way of crops. A rotation for a dairy 
 farm, for example, might be quite different from one for a 
 farm devoted to the production of grain for the market. 
 A few general rules, however, will apply to all rotations. 
 Every rotation should include one intertilled or hoed crop, 
 such as corn, potatoes, or cotton, in order that the soil may 
 receive the benefit of such a crop in the way of destroying 
 weeds, improving the tilth, and setting free potential plant 
 food. At least one leguminous crop should be included. 
 A crop that is exacting in its food requirements should be 
 followed by one less exacting. In general terms, the crops 
 should vary as much as possible in their food requirements, 
 manner of growth, root systems, and the season of the year 
 in which they occupy the ground. Whenever possible, the 
 rotation should include a catch crop or provide some other 
 method of insuring an adequate supply of organic matter. 
 Fertilizers should be applied to the particular crop or crops 
 that will give the most profitable returns for their use. 
 
 582. Some Typical Rotations. Rotations are in use that 
 cover periods varying from two to seventeen years. In 
 general, short rotations of three to five years are more in 
 favor than very long ones. A few examples will exemplify 
 the principles of rotation. 
 
 A common five-year rotation is as follows: Corn, oats, 
 wheat, clover, and timothy, each one year. Rye may be 
 seeded as a catch crop in the corn. 
 
 Corn, wheat, and clover form a common three-year rota- 
 tion, the ground being plowed for the corn, and the wheat 
 seeded in the corn stubble after disking. 
 
 Potatoes, wheat, and clover are popular as a rotation 
 
500 SOILS AND FERTILIZERS 
 
 in some of the good potato sections. The clover is plowed 
 under for potatoes and a heavy application of fertilizers 
 is used. 
 
 A rotation often used on dairy farms consists of corn, 
 oats, and clover, besides timothy for pasture. A catch 
 crop may be used in the corn. 
 
 A rotation that has been recommended for grain farming 
 in the Middle West is corn, oats, clover, and wheat. The 
 clover is plowed for wheat and all the straw and cornstalks 
 are plowed under. A catch crop of clover is also grown 
 between the wheat and corn. Ground rock phosphate 
 (609) is plowed under with the clover. 
 
 A rotation advocated for the cotton-growing sections 
 consists of cotton, corn, oats, and cowpeas, the last named 
 crop being plowed under as a green manure. 
 
 Over forty different rotations are in use in one state, 
 many of which, however, do not meet the requirements sug- 
 gested above for planning the rotation. 
 
 EXERCISES 
 
 Ex. 362. Explain the evolution of the rotation of crops. Is 
 rotation of crops desirable? Outline the reasons in favor of rotation 
 under these headings : (1) Food requirements of plants. (2) Manner 
 of growth. (3) Effect upon soil and economy of labor. (4) Effect 
 upon diseases, insects, and weeds. 
 
 Ex. 363. Are the yields of the various crops increased by rotat- 
 ing? Give the general rules for planning a rotation. What rota- 
 tion is used on your home farm? Do you use catch crops? Do you 
 grow any crop to plow under ? How many different rotations can you 
 find in use in your community ? How do they accord with the sugges- 
 tions for planning a rotation? 
 
CHAPTER LVIII 
 STABLE MANURE 
 
 583. IF the crop yields are not to decrease, some way 
 must be provided to replace in the soil the plant food re- 
 moved by the crops. This is done by the use of stable 
 manure and commercial fertilizers. 
 
 584. Importance of Stable Manure. Stable manure is 
 the oldest and is still the most used of all fertilizers. It has 
 stood the test of long experience, and has proved its posi- 
 tion as one of the most important manures. The fact that 
 the application of the excrement of animals to the soil 
 results in increased crop production is mentioned by the 
 early Roman writers, and from that time to the present 
 the majority of farmers have placed their main reliance on 
 this class of manures for maintaining fertility of the land. 
 
 The importance of manure is shown by the fact that the 
 quantity produced annually by the domestic animals of the 
 United States contains an amount of nitrogen, phosphorus, 
 and potassium that would cost $2,458,470,000 if pur- 
 chased in the cheapest forms of commercial fertilizers. 
 More than one third of the value of the manure is lost 
 through improper handling, and this loss is replaced only 
 in small part by the one hundred million dollars' worth of 
 commercial fertilizers purchased annually by the farmers 
 of this country. This loss of plant food is the more unfor- 
 tunate because it could in great measure be prevented. 
 
 585. Valuation of Manure and Fertilizers. Since some 
 way of stating the value of manure is desirable, it is custom- 
 
 501 
 
502 SOILS AND FERTILIZERS 
 
 ary to use the same method that is employed in calculating the 
 value of commercial fertilizers ; namely, to base the valua- 
 tion on the quantities of nitrogen, phosphorus, and potas- 
 sium that the manure or fertilizer contains, ignoring any 
 other constituents that may be present. The fertilizer 
 trade has always stated phosphorus not as the element but 
 as the anhydride, P 2 O 5 , which is termed phosphoric acid in 
 the trade (179). Likewise potassium is stated as the oxide, 
 K 2 O, under the trade name of potash. One pound of phos- 
 phorus is equivalent to 2.3 pounds of phosphoric acid 
 (P 2 O 8 ). One pound of potassium is equivalent to 1.2 pounds 
 of potash (K 2 O) . Nitrogen is sometimes stated as ammonia 
 (NH 3 ) , but this term is not so commonly used as are the terms 
 phosphoric acid and potash. One pound of nitrogen is the 
 equivalent of 1.2 pounds of ammonia. As these names are 
 used almost exclusively in the fertilizer trade, and most 
 commonly in the writings on manures and fertilizers, and 
 are also recognized by law in nearly all the states, it seems 
 best to employ them in this text. The term phosphoric acid 
 as used in discussing fertilizers does not mean true phos- 
 phoric acid (H 3 PO 4 ) (175) nor does the potash of the fer- 
 tilizer trade mean true potash (K 2 CO 3 ) (204). 
 
 For purposes of valuation nitrogen is given a price of 15 
 cents a pound, and phosphoric acid and potash are quoted at 
 5 cents a pound each. These are average prices for the past 
 decade and will be used in all the calculations in this text. 
 
 586. Composition of Manure from Different Animals. 
 The manures produced by the various classes of animals 
 differ in their composition and in their physical properties. 
 The following table gives the amount and value of the 
 plant food in one ton of manure of the common domestic 
 animals. 
 
STABLE MANURE 
 
 503 
 
 ANIMAL 
 
 NITROGEN 
 
 PHOSPHORIC 
 ACID 
 P 2 O 6 
 
 POTASH 
 K 2 
 
 VALUE PER 
 TON 
 
 Cow 
 
 91b. 
 
 3 Ib. 
 
 8 Ib 
 
 $1 89 
 
 Pig 
 
 9 Ib. 
 
 4lb. 
 
 12 Ib 
 
 2 14 
 
 Horse . . . . . . 
 
 12 Ib. 
 
 61b. 
 
 11 Ib 
 
 255 
 
 Sheep .... . . 
 
 17 Ib. 
 
 51b 
 
 13 Ib 
 
 3 39 
 
 Chicken ... 
 
 28 Ib 
 
 18 Ib 
 
 7 Ib 
 
 544 
 
 
 
 
 
 
 The difference in the value per ton of the manures is 
 largely due to the varying amounts of water which they 
 contain. Chicken manure, sheep manure, and horse manure 
 contain less water than the manure from pigs and cows. 
 
 While the table shows that there is a decided difference 
 in the value of a ton of the different manures, it is also true 
 that the value of the total amount of manure produced from 
 the same feeding stuffs does not vary much for the different 
 animals. If the same kinds and amounts of feeds were 
 given to cows and to sheep, for instance, the cows would 
 produce more tons of a wetter manure than the sheep ; but 
 the total value would be about the same in either case. 
 
 587. Factors Affecting the Value of Fresh Manure. 
 The value of stable manure as produced, and before it has 
 been subjected to any of the losses to be discussed later, is 
 largely determined by five principal factors: namely, (1) 
 the kind of feeds, (2) the age of the animal, (3) the kind of 
 animal, (4) the products from the animal, (5) the kind and 
 amount of litter used. 
 
 588. Kind of Feeds. The total value of the manure 
 produced by a given live weight of animals depends upon 
 the quality and the quantity of the feeding stuffs used in 
 the ration. Feeds vary greatly in the amount of plant food 
 
504 SOILS AND FERTILIZERS 
 
 that they contain. The fertilizing value of a ton of timothy 
 hay, for example, is $5.21 ; of clover hay, $8.79 ; of wheat 
 bran, $12.52 ; and of cottonseed meal, $23.20. Animals 
 fed on food substances low in fertilizing value will produce 
 manure of a correspondingly low value. In one experiment 
 with two lots of pigs, one of which was fed on corn meal and 
 bran, and the other on corn meal and meat scraps, the 
 manure produced by the latter had twice the value of that 
 from the pigs fed corn and bran. 
 
 589. Age of the Animal. Young animals use some of 
 the nitrogen compounds of the ration to build their muscles, 
 and a part of the phosphoric acid and calcium is utilized in 
 forming bone. Mature animals, whose bones and muscles 
 are already developed, retain in their bodies very little of 
 the fertilizing constituents of the feeds. Manure from young 
 and growing animals, therefore, has a lower value than that 
 from mature animals. 
 
 590. Kind of Animal. The kind of animal, as has been 
 stated, affects the value per ton of the manure more than it 
 does the total value of the manure produced from the same 
 feeds. Pigs and cows, however, consume more food in 
 proportion to their weight than do horses and sheep, and, 
 consequently, produce manure of a greater total value dur- 
 ing the year. 
 
 591. Product of the Animal. Milch cows use a portion 
 of the nitrogen and phosphorus of the feeds in producing 
 milk, and in that way some of the fertility value of the ma- 
 nure is lost. The value of the plant food in 5000 pounds 
 of average milk is $4.98. 
 
 592. Kind of Litter Used. Manure consists of the excre- 
 ments of animals mixed with the litter or bedding material 
 that is used to absorb the liquids. These materials vary 
 
STABLE MANURE 
 
 505 
 
 in the amount of plant food that they contain. The fertiliz- 
 ing value of a ton of wheat straw is $2.40, and of an equal 
 quantity of sawdust it is only $1.60. 
 
 593. Proportion of Plant Food Recovered in Manure. 
 Taking into consideration the different kinds of live stock 
 maintained on the average farm and the proportion of grow- 
 ing and mature animals, 
 
 it may be assumed that 
 three fourths of the 
 nitrogen and phos- 
 phoric acid of the feeds 
 and over nine tenths of 
 the potash are re- 
 covered in the manure. 
 In a general way it may 
 be said that the manure 
 contains eighty per 
 cent of the fertilizing value of the ration fed and the full 
 value of the materials used for bedding. According to 
 these figures the total value of the manure for a year from 
 a herd of fifty dairy cows fed a daily ration of 10 pounds of 
 grain (corn meal, ground oats, and bran), 35 pounds of corn 
 silage, and 15 pounds of clover hay, and bedded with wheat 
 straw amounts to $2,094.20. 
 
 594. Losses in Manures. The foregoing statements 
 refer to fresh manure which has suffered no loss of its valuable 
 constituents. On the average farm, unfortunately, because 
 of lack of care in preventing the losses to which manure 
 is subject, not more than half this value is realized. It will 
 be well to consider these losses and the means by which they 
 may be prevented. The principal ways in which plant 
 food is lost from the manure are as follows : (1) by neglect- 
 
 FIG. 232. Manure pile on the island of Jersey 
 with cistern below to collect liquid manure. 
 
506 
 
 SOILS AND FERTILISERS 
 
 ing to save the liquid manure; (2) by loss of ammonia in 
 the stable; (3) by leaching in the barnyard; (4) by hot 
 fermentation. 
 
 595. Value of the Liquid Manure. The liquid part of 
 the manure, which is commonly allowed to run away, con- 
 tains two thirds of the nitrogen and four fifths of the potash 
 excreted by the animal. The following table shows the 
 distribution of the plant food in the manure from the fifty 
 dairy cows mentioned in Section 593. 
 
 Value of the solid part . $716.88 
 
 Value of the liquid part . , . 1,200.20 
 
 Value of the bedding . . ;,.;.. 177.12 
 
 Total value of the manure $2,094.20 
 
 It will be seen that if the liquid is lost, the value of the 
 manure will be less than $900 instead of $2,094.20 as 
 calculated. It is evident, therefore, that the stable floors 
 
 , ., should be made of 
 
 cement or other water- 
 tight material, and 
 that sufficient bedding 
 should be used to ab- 
 sorb all the liquid. In 
 many parts of Europe 
 cisterns are built in 
 connection with the 
 stables to collect the 
 liquid manure ; but un- 
 der American conditions it is best to keep the liquid and 
 solid manures together by the plentiful use of bedding. 
 
 596. Loss of Ammonia in the Stable. Manure contains 
 enormous numbers of decay bacteria that cause its rapid 
 decomposition. One class of these bacteria liberates am- 
 
 FIG. 233. Outfit for the distribution of 
 liquid manure on the island of Jersey. 
 
STABLE MANURE 507 
 
 monia from the liquid manure. Most of the nitrogen in the 
 liquid excrement is in the form of an organic compound 
 called urea (CON 2 H 4 ). The bacteria cause the urea to 
 take on water and change to ammonium carbonate, thus : 
 
 CON 2 H 4 + 2H 2 O-KNH 4 ) 2 CO 3 . 
 
 The ammonium carbonate dissociates and gives off ammonia 
 and carbon dioxide (164), resulting in loss of nitrogen from 
 the manure. The odor of ammonia frequently noticed in 
 the stable is due to this chemical change. 
 
 The decomposition does not take place so readily if the 
 liquid is completely absorbed by the bedding. The use of 
 dried muck soil or peat with the bedding is effective in pre- 
 venting this change. If muck soil is easily obtained, it will 
 pay to dry a few wagon loads of it for use in the stable. 
 
 Chemical preservatives are sometimes used in the stable 
 to prevent loss of ammonia. The best material for this 
 purpose is acid phosphate (178). The acid phosphate 
 unites with the ammonia, forming the double salt, calcium 
 ammonium phosphate, which is not volatile; hence this 
 change prevents the escape of ammonia. The calcium sul- 
 phate (gypsum) which is always present in commercial 
 acid phosphate is also supposed to be effective in preventing 
 loss of ammonia from the manure, by changing the ammo- 
 nium carbonate into ammonium sulphate, which is not 
 volatile and does not so readily decompose : 
 
 Oa + CaSO 4 ->- CaCO 3 + (NH 4 ) 2 SO 4 . 
 
 The acid phosphate should be dusted over the manure 
 gutter at the rate of one pound a day for each animal. 
 This use of acid phosphate is to be recommended, because, 
 in order to obtain the best results in the field, some phos- 
 
508 
 
 SOILS AND FERTILIZERS 
 
 phate fertilizer should always be used in connection with 
 
 stable manure (612). 
 
 597. Losses in Manure from Leaching. Next to improper 
 
 absorption of the liquid, the greatest loss in manure comes 
 
 from leaching by rains. 
 As ordinarily handled 
 the manure is thrown 
 out each* day into the 
 open yard to lie for 
 months subjected to 
 washing by the summer 
 or winter rains. In 
 
 FIG. 234. Great losses result from leaving 
 manure exposed to the weather. 
 
 many cases it is even 
 deposited under the 
 eaves of a large barn, 
 and thus , the washing 
 
 process is made more complete. It is absurd to go to the 
 trouble of absorbing all the liquid excrement by means of bed- 
 ding, and then allow it to be washed out of the manure. The 
 losses in manure due to leaching by rains in the open yard 
 are much greater than most people imagine. Many experi- 
 ments have been carried on to determine these losses, and 
 the following table gives the results of four such experiments : 
 
 LOSSES IN MANURE FROM LEACHING 
 
 PERIOD 
 Days 
 
 NITROGEN 
 Per Cent 
 
 PHOSPHORIC ACID 
 P 2 5 
 Per Cent 
 
 POTASH 
 K 2 O 
 Per Cent 
 
 131 
 
 57.0 
 
 62.0 
 
 72.0 
 
 70 
 
 44.0 
 
 16.0 
 
 28.0 
 
 76 
 
 39.0 
 
 63.0 
 
 56.0 
 
 50 
 
 69.0 
 
 59.0 
 
 72.0 
 
 Average 
 
 52.2 
 
 50.0 
 
 57.0 
 
STABLE MANURE 
 
 509 
 
 The table shows that the average loss amounted to more 
 than half the plant food in the manure during rather short 
 periods, the longest time being a little over four months. 
 
 On many farms the manure is exposed to the weather for 
 a much longer period of time. These losses vary with the 
 climatic conditions and with the quality of the rations. 
 During heavy rains, especially if they occur in warm weather, 
 the losses are much greater than in dry or cold weather. 
 In the experiments noted above, the rainfall was as great 
 during the 50 days of the last experiment as it was in the 
 case of the 131 days of the first one. The relative decrease 
 in value is larger for manures produced from rations of high 
 nutritive value. In other words, the more valuable the 
 manure, the greater will 
 be the percentage of 
 loss from leaching. It 
 is conservative to say 
 that manure exposed 
 to the weather for six 
 months loses fully half 
 its value. 
 
 It is worthy of note 
 also that the plant food 
 that is washed out of 
 the manure is the part 
 that is most available, 
 as it is soluble in water and is in the condition in which it 
 can be immediately used by the plants. The manure that 
 remains, on the other hand, represents the tougher and more 
 slowly decomposed material, hence it contains the least 
 available part of the plant food. 
 
 Manure is never so valuable as when perfectly fresh. 
 
 FIG. 235. Covered manure shed with cemented 
 bottom. 
 
510 SOILS AND FERTILIZERS 
 
 Even the best methods of handling and care, if the manure 
 is stored, cannot prevent more or less loss of the valuable 
 constituents. For this reason it is advisable to haul the 
 manure directly from the stable to the field each day, when- 
 ever the conditions permit. 
 
 There are always times on every farm when it is not 
 possible to haul the manure directly to the field, and some 
 
 suitable place should 
 be provided for its 
 temporary storage (Fig. 
 235). The essential 
 requisite of such a 
 storage place is that 
 it shall have a cemented 
 bottom to prevent any 
 loss of the liquid ma- 
 
 FIG. 236. Cattle in a covered barnyard. 
 
 nure. A cover to pro- 
 tect it from the rains is desirable. A small manure shed 
 would pay for itself in a single season on a farm maintaining 
 much live stock. 
 
 Some farmers store the manure in what is called a covered 
 barnyard (Fig. 236), which is usually one large room in the 
 barn in which the cattle are allowed to run during the 
 greater part of the day. The floor is cemented and bedding 
 material is liberally used. The cattle tramp the manure 
 into a solid mass and it is allowed to accumulate until it is 
 convenient to remove it to the field. Protected in this way, 
 the manure suffers very little loss of fertilizing constituents. 
 
 598. Open Yard Feeding a Wasteful Practice. It is 
 probably true that upon a majority of the farms in America 
 cattle are fed during the winter in open lots, the manure 
 not being hauled away until the following summer or fall, 
 
STABLE MANURE 
 
 511 
 
 if indeed it is removed at all. This method of feeding pre- 
 sents conditions that result in excessive losses from leaching, 
 and it is safe to say that more than half the fertilizing value 
 of the manure is lost where this practice is followed. In 
 the corn .belt of this country, for instance, large numbers 
 of cattle are fed during the winter, and it is not unusual 
 to' see a large feeding 
 lot covered to a con- 
 siderable depth with 
 manure which is spread 
 out and exposed to the 
 weather in such a way 
 that the maximum ef- 
 fects of leaching must 
 take place. There is 
 no doubt that, con- 
 sidered from the fertility 
 point of view alone, 
 these farms would be better off if the corn were sold from 
 the farm and the stover plowed under. The feeding of the 
 future must be done under cover if the fertility of the soil is 
 to be economically maintained. 
 
 599. Hot Fermentation. Manure that has been thrown 
 into a loose heap, especially if it contains much horse or 
 sheep manure, soon becomes very hot. The heating some- 
 times proceeds so far that part of the manure becomes white, 
 or fire-fanged as it is popularly called. An examination 
 will show that ammonia is being evolved in large quantities 
 from the heating manure. This fermentation is caused by 
 certain bacteria that bring about oxidation of the organic 
 matter, the nitrogen being converted into ammonia. The 
 loss of nitrogen in this way is very large, the amount vary- 
 
 FlG. 237. Open yard feeding greatly reduces 
 the fertilizing value of manure. 
 
512 SOILS AND FERTILIZERS 
 
 ing in different experiments from 20 per cent to over 80 per 
 cent. In the case of the white fire-fanged material all 
 the nitrogen is driven off. Since the bacteria that cause 
 this rapid oxidation of the organic matter cannot exist in 
 the absence of free oxygen, no heating will take place if the 
 manure pile is so compact that no air can enter it. In a 
 moist, compact manure pile a cold fermentation takes place, 
 which is caused by an entirely different class of bacteria 
 and which does not result in the formation and loss of am- 
 monia. It is evident, therefore, that the stored manure 
 should be carefully compacted as well as protected from 
 leaching. It will be seen that the covered barnyard presents 
 almost ideal conditions for storing manure. A method of 
 storage very similar to the covered barnyard plan has been 
 in use in Europe for many years and is known as the deep 
 stall method. The manure accumulates in the stall in such 
 a way that it is thoroughly packed by the feet of the cattle, 
 and is said to lose very little of its fertilizing value. 
 
 600. Composting Manures. Any method of storing 
 manure requires considerable labor, and for that reason 
 storing it is 'to be avoided in general farming whenever it is 
 possible to use it in the fresh condition. In market garden- 
 ing, on the other hand, such quantities of manure are used 
 that it is necessary to have it thoroughly rotted before 
 applying, as otherwise the crop would suffer from the heat- 
 ing effect that the large amount of raw manure would have 
 on the soil. While the manure may be rotted by keeping 
 it in a moist, compact heap, it must be remembered that the 
 manure commonly used by market gardeners is the horse 
 manure from the city stables. This heats so rapidly that 
 special care is necessary to prevent hot fermentation, and 
 the pile must be moistened frequently. 
 
STABLE MANURE 513 
 
 Many market gardeners prefer to compost the manure 
 with earth, peat, or muck. This is done by making a founda- 
 tion of about six inches of dirt and placing on top of this 
 alternate layers of manure and soil, moistening the mass as 
 the heap grows. The sides and the top should be smoothed 
 off and the mass covered with a thin layer of earth to 
 prevent loss of nitrogen. After about two months the 
 pile should be turned over, the materials thoroughly 
 mixed, and more water added, if necessary, to keep the 
 compost moist. A compost in great favor with green- 
 house men is one made of manure and sod, these materials 
 bsing piled in alternate layers as described above. This 
 gives the fibrous compost so desirable for bench and pot 
 work. 
 
 Any of the refuse organic materials of the farm or garden 
 may be used in composts. Weeds, refuse parts of plants, 
 dead animals, and kitchen wastes may be added to the 
 manure-earth mixture, or composted separately ; for handled 
 in this way they decompose rapidly and without offensive 
 odors. The presence of the earth decreases the loss of am- 
 monia where highly nitrogenous materials are used. In 
 using composts a good practice is to add bone meal to the 
 heap. In this way the plant food in the bone meal is 
 made available to the plants, and the compost is made more 
 valuable. 
 
 601. Applying Manure. Two general methods for the 
 application of manure are in common use : one is to throw 
 it into heaps, where it is allowed to remain some time before 
 being spread ; the other is to broadcast it directly from the 
 wagon. The first method is objectionable for several rea- 
 sons. In the first place it increases the work necessary to 
 spread the manure, since it must be handled twice, and it 
 
 EV. CHEM. 33 
 
514 SOILS AND FERTILIZERS 
 
 takes no more labor to spread it from the wagon than from 
 the heap on the ground. The leachings from these heaps 
 make the 'spots directly beneath more fertile than the rest 
 of the field, and hence produce a rank growth at those 
 places (Fig. 238). This uneven growth is undesirable, be- 
 cause in the case of grains it increases the danger of lodging 
 in the more fertile spots ; and in any case it results in un- 
 evenness in the maturity of the crop. A crop that has a large 
 supply of plant food, for instance, has a longer period of 
 
 FIG. 238. Showing the uneven growth due to allowing manure to remain 
 in heaps before spreading. 
 
 growth than one with a meager supply and consequently is 
 later in maturing. If, therefore, the field is very uneven in 
 fertility, a part of the crop will be ready to harvest some 
 time before the rest has matured. On the other hand, if the 
 manure is spread directly from the wagon, not only is the 
 labor lessened, but the danger of unevenness in growth is 
 to some extent avoided. Moreover there is no likelihood of 
 loss in the value of the manure when it is spread in a thin 
 layer on the ground. 
 
 Manure spreaders (Fig. 239) are coming into general use. 
 Some recent experiments seem to indicate that manure gives 
 
STABLE MANURE 
 
 515 
 
 FIG. 239. The best way to apply manuie is 
 by means of the manure spreader. 
 
 better returns when spread by the machine than it does 
 when applied by hand. Whatever method is used to spread 
 the manure, it will readily be seen that the finer the material 
 the easier it will be to 
 distribute it evenly. 
 
 602. Where to Use 
 Manure. There is some 
 difference of opinion as 
 to which of the ordinary 
 farm crops give the best 
 returns for the use of 
 stable manure. Prob- 
 ably more farmers use 
 it on the land plowed 
 for corn than in any 
 
 other way. Corn is especially adapted to utilize the plant 
 food of manure, since it makes the greater part of its growth 
 in midsummer, when nitrification is at its height and the 
 nitrogen of the manure is being made available most rapidly. 
 It is always safe to manure corn heavily. 
 
 Many farmers prefer to use manure as a top dressing for 
 grass lands, since such use increases the organic matter of 
 the soil by stimulating the growth of the fibrous roots of the 
 sod. This method gives good returns for the manure used. 
 The permanent pastures should not be neglected, but should 
 be occasionally top dressed with manure and commercial 
 fertilizers. 
 
 603. Amount to Apply. Market gardeners use very 
 large quantities of manure, sometimes as much as forty 
 tons to the acre, but they probably use the manure for its 
 physical effect upon the soil even more than for the plant 
 food that it contains. This is partly due to the fact that 
 
516 SOILS AND FERTILIZERS 
 
 the gardener cannot conveniently make extended use of 
 green manures as a source of organic matter. For ordinary 
 farm crops, on the other hand, it is not customary to use 
 more than eight to ten tons to the acre, and on general 
 principles it may be stated that somewhat frequent light 
 dressings pay better than very large ones given at long inter- 
 vals. On the other hand, the amount of manure produced 
 on the average farm is so small when compared with the 
 land to be fertilized that it would be impossible to spread 
 it over all the farm yearly. For this reason, it is a good 
 plan to apply the manure to one or two crops in the rota- 
 tion, thus covering only a part of the farm each year. 
 
 604. How Manure Improves Soils. Stable manure adds 
 all the elements of plant food to the soil, and while some of 
 it is not in forms immediately available to the plant it 
 becomes so during a period of years. Manure adds to the 
 soil enormous numbers of bacteria that attack not only 
 the manure itself but the organic matter already in the soil. 
 Manure also improves the physical condition of the soil, 
 and during its decay the acid products formed act upon 
 the potential plant food and make some of it available. 
 Attention has already been called to the fact that when 
 properly handled the manure returns to the soil nearly one 
 half the organic matter of the feeds. Everything considered, 
 manure is probably the best fertilizer the farmer can use, 
 especially when it is reenforced with acid phosphate. 
 
 605. Results with Manure. The good results in crop 
 yields from the use of stable manure are known to every 
 farmer and gardener. In one experiment in England the 
 use of manure has maintained the yield of wheat at 34 
 bushels to the acre for seventy-five years, while the average 
 for the unmanured field was only 13 bushels. At the Ohio 
 
STABLE MANURE 
 
 517 
 
 FIG. 240. The field on the left received ten 
 tons of manure while the one on the right was 
 
 unmanured. 
 
 Experiment Station stable manure has given a profit in 
 increased yields of $3.22 for each ton of manure used over 
 a period of twenty years. 
 Manure differs from 
 other fertilizers in its 
 lasting effects when ap- 
 plied to the soil. In 
 one experiment manure 
 was used on a plot 
 for twenty years, after 
 which ks use was dis- 
 continued. The gooi 
 effect was noticeable for 
 more than thirty years after the last application. Every 
 farmer knows that the effects of a single application of manure 
 are evident five or six years after its use. 
 
 606. City Sewage. Large quantities of plant food are 
 lost in the sewage of the cities. City sewage contains nitro- 
 gen, phosphorus, and 
 potassium to the annual 
 value of one dollar for 
 each inhabitant. In 
 China and Japan, two 
 countries noted for their 
 high crop production, 
 the sewage of the cities 
 has been used as a fer- 
 tilizer for thousands of 
 years. The sewage is 
 carried out to the farms 
 and gardens, diluted with water, and used on the growing 
 crops. Such a procedure is repulsive to the occidental mind ; 
 
 FIG. 241. Using city sewage as a fertilizer 
 in Japan. 
 
518 SOILS AND FERTILIZERS 
 
 but it would be a great thing for agriculture if some unob- 
 jectionable method could be discovered to make use of the 
 large amount of plant food now being lost in the city sewage. 
 
 EXERCISES 
 
 Ex. 364. Is the use of stable manure as a fertilizer of recent or 
 ancient origin? What is the value of the manure produced annually 
 in the United States ? Is much of this value lost ? Why is a well- 
 kept manure heap an indication of thrift ? How is the value of manure 
 stated ? What is meant in trade by phosphoric acid ? By potash ? 
 
 Ex. 365. How do the values of the manure from different kinds 
 of animals compare ? Which is the most valuable per ton ? To what 
 is this difference in value per ton largely due ? Is there much difference 
 in the total value of the manure produced by the different animals 
 from the same feeds ? 
 
 Ex. 366. What are the five factors affecting the value of fresh 
 manures? Explain how the value of the manure is affected by the 
 kind of feeds ; by the age of the animal ; by the kind of animal ; 
 by the animal products ; by the kind of litter. What proportion of 
 the plant food in the ration is recovered in the manure ? 
 
 Ex. 367. If fifty animals were fed the ration given on page 336, 
 what would be the value of the manure produced in a year, assuming 
 that ten pounds of wheat straw were used daily as bedding for each 
 animal? (For the fertilizing constituents of the feeds and bedding 
 see tables in Vivian's First Principles of Soil Fertility.) 
 
 Ex. 368. In what four principal ways is plant food lost from the 
 manure? What proportion of the different elements of plant food is 
 found in the liquid manure ? In the solid manure ? What proportion 
 of the value of the manure is lost if the liquid is not saved ? 
 
 Ex. 369. In what form is the nitrogen in the liquid excrement? 
 What compound do the bacteria form from the urea? Write the 
 reaction. To what is the odor of ammonia in stables due ? How may 
 the loss of ammonia in the stable be prevented? Write the equation 
 for the reaction between gypsum and ammonium carbonate. How 
 should acid phosphate be used to prevent loss of ammonia ? 
 
 Ex. 370. How much of the plant food is lost when manure is ex- 
 posed to the weather ? How do climatic conditions affect the amount of 
 
STABLE MANURE 519 
 
 loss? Explain the statement that the most available part of the plant 
 food is lost by leaching. Why should manure be hauled directly to the 
 field when possible? What are the essentials of a storage place for 
 manure ? What is meant by a covered barnyard ? Is there much loss 
 in manure stored in a covered barnyard ? Are there any farms in your 
 neighborhood where manure is being wasted? Do any of the farms 
 near the school have manure sheds or covered barnyards ? 
 
 Ex. 371. Explain why open yard feeding is wasteful of manure. 
 What is meant by L Dt fermentation of manure ? What losses occur 
 from hot fermentation ? How may hot fermentation be prevented ? 
 What is meant by composting manure ? How is a compost heap pre- 
 pared ? What other materials beside manure may be composted? 
 
 Ex. 372. Why should manure never be placed in heaps on the 
 field before spreading? Why is a manure spreader desirable on a 
 farm ? Upon what crop is manure most commonly used ? What 
 crops do the farmers of your locality manure ? Why does corn re- 
 spond so well to treatment with stable manure ? What are the advan- 
 tages of using manure on grass lands? 
 
 Ex. 373. How much manure is used to the acre by market gar- 
 deners? In ordinary farming? Which is the more desirable, heavy 
 applications at long intervals or frequent light applications? Explain 
 how manure improves the soil. Discuss the lasting effect of manure. 
 How much plant food is lost in city sewage? In what countries is 
 the city sewage all saved and used on the crops ? 
 
CHAPTER LIX 
 COMMERCIAL SOURCES OF PLANT FOOD 
 
 PHOSPHORUS 
 
 607. Phosphorus must be Purchased. Phosphorus is the 
 one element that must be purchased on practically every 
 farm if its fertility is to be maintained. It is the element 
 that is the limiting factor on nearly every farm. Phosphorus 
 is present in small quantities, some of the soils containing 
 as little as 0.01 per cent and very few having as much as 
 0.15 per cent. From two thirds to three fourths of the 
 phosphorus taken from the soil by the plants is stored in 
 the seeds, and is, therefore, removed from the farm when 
 grain is sold. Animals use phosphorus in making bone 
 and milk ; hence the sale of milk or live stock also removes 
 phosphorus from the farm. While the loss of phosphorus 
 from the sale of animal products is much less than that 
 from the sale of the crops, it is sufficiently large to be a 
 decided drain on the phosphorus supply of the soil, especially 
 if the manure produced by the animals does not receive 
 better care than is given to it on the average farm. There 
 is no natural method of increasing the phosphorus of the soil, 
 such as there is in the case of nitrogen, by the fixation due 
 to the nodule-forming bacteria. The farmer, therefore, 
 must purchase phosphorus to replace that which is removed 
 from the farm. 
 
 When feeds are purchased in large quantities, as they are 
 on some dairy farms, phosphorus is brought on to the farm 
 
 520 
 
COMMERCIAL SOURCES OF PLANT FOOD 521 
 
 in them and may be put into the soil through the manure. 
 In this case, however, much more nitrogen than phosphorus 
 is purchased, and additional phosphorus is necessary if 
 maximum yields are to be obtained. Recent investigations 
 make it clear that a certain balance between the elements of 
 plant food in the soil is essential to the best results in plant 
 growth. In other words, a balanced ration for plants is 
 quite as desirable as a balanced ration for animals. 
 
 608. Bone Phosphates. The commercial sources of 
 phosphorus for fertilizers are the bones of animals and the 
 various deposits of mineral phosphates; and, as has been 
 mentioned, the phosphorus is stated in fertilizer trade not 
 as the element, but as phosphoric acid (P2O 5 ). The bones 
 of animals have been used as fertilizers for several centuries, 
 and many farmers still prefer them to any other form of 
 phosphorus fertilizers. The mineral matter of bone consists 
 almost entirely of tricalcium phosphate, which is thoroughly 
 permeated by the organic matter of the bone. The bones 
 used in making fertilizers come from the packing houses, 
 and from the reducing establishments which use the animals 
 that die from accident or disease. 
 
 Before being used as a fertilizer the bones are ground to a 
 fine powder. If they are ground in the natural condition, 
 the powder *is known as raw bone meal; if they are ground 
 after they have been steamed to remove the fat, the product 
 is steamed bone meal. Raw bone meal contains about 
 22 per cent of phosphoric acid (9.5 per cent phosphorus) 
 and 4 per cent of nitrogen, while steamed bone meal con- 
 tains about 28 per cent of phosphoric acid (12 per cent 
 phosphorus) and 2 per cent of nitrogen (179). 
 
 The steamed bone meal is the better product to use, since 
 it contains more phosphorus and is more readily decomposed 
 
522 SOILS AND FERTILIZERS 
 
 in the soil. The fat in the raw bones interferes with the 
 decay of the bone and has itself no fertilizing value, 
 but can be used to advantage in other ways. Steamed 
 bone meal, too, is usually lower in price than the raw 
 bone meal. 
 
 609. Mineral Phosphates. Deposits of tricalcium phos- 
 phate are found in several places in this country and in 
 Canada. Most of that used in fertilizers at the present 
 time comes from Tennessee, South Carolina, and Florida. 
 The mineral phosphate has the same chemical composi- 
 tion as that found in the mineral matter of bones, but 
 since it is not permeated with organic matter, as is the bone 
 phosphate, it is less soluble in the soil moisture than is the 
 other. 
 
 There is some difference of opinion as to whether plants 
 can utilize the phosphorus of the rock phosphates even when 
 the material is finely ground. It is generally agreed that 
 these phosphates are of practically no value when used on 
 soils that are very low in, organic matter ; but it is held by 
 many that when mixed with manure or turned under with 
 clover or other green manure crops they are valuable sources 
 of phosphorus. The theory has been advanced that the 
 carbon dioxide evolved by the decaying organic matter 
 makes enough of the phosphate soluble to supply the needs 
 of the growing crop. The advocates of rock phosphate 
 recommend that, as the material is comparatively cheap, 
 it be applied in large quantities (1000 pounds or more every 
 four years) with a green manure crop, and that the soil be 
 kept well supplied with organic matter. 
 
 The finely ground rock phosphate is known in some 
 sections of the country as floats. A good sample contains at 
 least 28 per cent of phosphoric acid, but as the rock phos- 
 
COMMERCIAL SOURCES OF PLANT FOOD 523 
 
 phates vary greatly in purity, floats should be purchased only 
 on a guaranteed analysis. 
 
 610. Acid Phosphate. It has long been the custom to 
 treat the rock phosphates with sulphuric acid to make the 
 phosphorus more available. The proportions of acid and 
 phosphate used should be such as to convert the tricalcium 
 phosphate into monocalcium phosphate (176 and 178), thus : 
 
 Ca 3 (P0 4 ) 2 + 2 H 2 S0 4 -^ CaH 4 (P0 4 ) 2 + 2 CaSO 4 . 
 
 The monocalcium phosphate is soluble in water and hence 
 is available for plant growth. The soluble phosphate is not 
 separated from the calcium sulphate, but the whole mixture 
 resulting from the treatment of the rock phosphate with the 
 acid is sold under the different names of acid phosphate, 
 superphosphate, and acidulated rock. 
 
 If not enough acid is used to convert all the phosphate 
 into the monocalcium form, the following reaction may 
 take place : 
 
 Ca 3 (PO 4 ) 2 + CaH 4 (PO 4 ) 2 ->- 2 Ca 2 H 2 (PO 4 ) 2 . 
 
 This new compound is dicalcium phosphate, and as it is 
 regarded as an intermediate step in the reversion, or changing 
 back, of monocalcium to tricalcium phosphate, it is known 
 in the trade as reverted phosphate. Dicalcium phosphate is 
 not soluble in water, but is readily dissolved by very weak 
 acids and is supposed to be as available to the plants as the 
 monocalcium phosphate. For that reason the phosphoric 
 acid of these two compounds, monocalcium and tricalcium 
 phosphates, is termed available phosphoric acid. 
 
 Acid phosphates as found on the market contain from 
 12 to 18 per cent of available phosphoric acid (P 2 O 5 ) in 
 the two forms of monocalcium phosphate and dicalcium 
 
524 
 
 SOILS AND FERTILIZERS 
 
 phosphate. In all probability more phosphorus is purchased 
 by farmers in the form of acid phosphate than in all other 
 materials combined. 
 
 611. Basic slag is used in large quantities in Europe and 
 to some extent in this country as a source of phosphorus 
 for plant food. It is made from certain European iron ores 
 that contain considerable quantities of phosphorus (236). 
 Basic slag contains about 18 per cent of phosphoric acid in 
 a form that is readily available to the crops. 
 
 612. Phosphates with Manure. A ton of average stable 
 manure contains about 9 pounds of nitrogen, 2 pounds of 
 
 FIG. 242. Showing the increase in yield from one ton of manure. 1. Yard 
 manure. 2. Stable manure. 3. Stable manure with forty pounds of floats. 
 4. Stable manure with forty pounds of acid phosphate. 
 
 phosphorus, and 8 pounds of potassium. Manure, therefore, 
 is evidently deficient in phosphorus, and it is not surprising 
 that the addition of a phosphate to it materially increases 
 its crop-producing power. 
 At the Ohio Station an experiment has been running for 
 
COMMERCIAL SOURCES OF PLANT FOOD 525 
 
 twenty yea s in which stable manure alone has been compared 
 with manuies to which acid phosphate and floats have been 
 added. All manures were used at the rate of eight tons to 
 the acre on the corn in a three-year rotation of corn, wheat, 
 and clover. In one case forty pounds of acid phosphate and 
 in another forty pounds of floats were added to each ton of 
 manure. As an average for the entire period the stable 
 manure alone gave an increase of crops worth $3.22 for 
 each ton of manure. A ton of stable manure and forty 
 pounds of floats gave a net profit of $4.56, and a ton of 
 manure and forty pounds of acid phosphate gave a net profit 
 of $4.80. It will probably always pay to add some form of 
 phosphate to the manure, and the best way to use it is to 
 scatter it over the manure in the stable. Floats do not 
 have the power of fixing ammonia that was noted in the 
 case of acid phosphate (596). 
 
 POTASSIUM 
 
 613. Need of Potassium. Most soils are more abundantly 
 supplied with potassium than with phosphorus, and for 
 that reason potassium is less frequently the limiting factor 
 of plant growth. Fully three fourths of the potassium of 
 the mature crop is found in the stems and the leaves, which 
 are not so generally sold from the farm as are the seeds. 
 Likewise the animal retains very little of the potassium 
 of its food ; hence most of the potassium of the ration is 
 recovered in the manure. 
 
 In the case of peat soils and some sandy soils, however, 
 potassium is the limiting factor and it must be supplied 
 to make them productive. Some plants, such as tobacco, 
 potatoes, and cabbage, require large quantities of potassium, 
 
526 SOILS AND FERTILIZERS 
 
 and their successful culture for long periods on most soils 
 necessitates the use of some commercial form of potassium. 
 
 614. Potassium Salts. For many years practically all 
 the potash used in fertilizing came from the European 
 potash mines. These mines contain immense deposits of 
 salts, containing various percentages of potash. Only three 
 or four of these products have been commonly used in this 
 country and they are the only ones that will be discussed here. 
 
 615. Kainit. This is one of the crude salts which has 
 been ground to a powder. It looks somewhat like com- 
 mon salt, but is darker in color and contains about 12.5 
 per cent of potash (K 2 O) in the form of sulphate, mixed 
 with sulphate and chloride of magnesium. 
 
 616. Muriate of potash is manufactured from the crude 
 minerals of the mines by concentration, and contains about 
 50 per cent of potash in the form of potassium chloride. At 
 the present price the muriate supplies potash at a cheaper 
 price than any of the other materials. 
 
 617. Sulphate of potash is another concentrated product 
 of the European mines. What is known as high-grade 
 sulphate contains about 53 per cent of potash in the form of 
 the sulphate (K 2 S0 4 ). The actual potash in this compound 
 costs a trifle more per pound than in the muriate. A lower 
 grade sulphate containing 26 per cent of potash mixed 
 with magnesium sulphate is sold under the name of double 
 manure salt. 
 
 A relatively small quantity of potash is produced from 
 the ash of the giant kelps which are S3 abundant on the 
 Pacific coast. There are also certain alkali lakes in this 
 country from which some potash is obtained, notably 
 those in Nebraska. The potash (K 2 O) produced from these 
 lakes in 1917 was about 20,000 tons, while the amount 
 
COMMERCIAL SOURCES OF PLANT FOOD 527 
 
 annually used in this country previous to 1914 was nearly 
 300,000 tons. 
 
 618. Wood ashes at one time were the sole source of 
 potash for fertilizing purposes, but at present ashes supply 
 only a very small proportion of this element of plant food. 
 Wood ashes vary greatly in composition, the ash from soft 
 woods containing less potash than that from hard woods, 
 the content of potash ranging from 2 to 8 per cent. Potash 
 as found in wood ashes is in a form that is very soluble 
 in water; so that ashes exposed to the weather may have 
 practically all the potash leached out of them (204). 
 Leached ashes as a rule contain less than 2 per cent of potash. 
 As it is not possible to distinguish between leached and un- 
 leached ashes by mere physical examination, it is evident that 
 this material should be purchased only from guaranteed 
 analysis. 
 
 NITROGEN 
 
 619. Importance of Nitrogen. In some ways nitrogen 
 is the most important element of plant food. The more 
 common farm crops use more nitrogen than they do phos- 
 phorus and potassium combined. Nitrogen is the most 
 expensive fertilizing material to buy, as it costs about three 
 times as much a pound as either phosphorus or potassium. 
 It is, unfortunately, more easily lost from the farm than 
 any other element of plant food. Approximately two thirds 
 of the nitrogen of the cereal crops is in the seeds and is 
 removed from the farm when grains are sold. It is also lost 
 from the soil in the drainage water and sometimes by deni- 
 trification. The ease with which it is lost from manure 
 has been discussed. It has been said that profitable agri- 
 culture depends upon an economical method of conserving 
 
528 SOILS AND FERTILIZERS 
 
 and renewing the nitrogen supply of the soil. The power of 
 legumes to fix the nitrogen of the air should be utilized as 
 far as possible, and nitrogen should be ^urchased only as a 
 last resort. Nitrogen fertilizers are so expensive that the 
 matter of their purchase should receive very careful con- 
 sideration. 
 
 The principal sources of nitrogen for fertilizers are: 
 (1) the by-products of the packing houses and rendering 
 establishments, (2) ammonium sulphate from the gas and 
 coke works, (3) nitrate of soda, and (4) cyanamide. 
 
 620. Packing House By-products. The more common of 
 the by-products of the rendering, packing, and canning 
 establishments that handle meat and fish are as follows : 
 
 Dried blood containing from 7 to 10 per cent of nitrogen 
 Meat meal containing from 12 to 14 per cent of nitrogen 
 Hoof meal containing from 11 to 12 per cent of nitrogen 
 Tankage containing from 4 to 9 per cent of nitrogen 
 Dried fish containing from 8 to 11 per cent of nitrogen 
 
 The first three names are self-explanatory. Tankage 
 consists of the refuse material that cannot be used as human 
 food, and which has been placed in a tank and heated with 
 steam under pressure. The heating extracts the fat, which 
 is used in soap making. Tankage is, therefore, variable in 
 character, and in addition to its nitrogen contains from 3 
 to 12 per cent of phosphoric acid in the form of bone meal. 
 
 Most of the fish fertilizers are made from menhaden, a 
 fish that is caught in large numbers along the Atlantic coast. 
 The fish are steamed and pressed to extract the oil and the 
 remaining pomace is dried and ground. This material 
 contains from 8 to 11 per cent of nitrogen and about 3 per 
 cent of phosphoric acid. Some of the fish fertilizers consist 
 
COMMERCIAL SOURCES OF PLANT FOOD 529 
 
 of the residue of the canning factories, but these are not so 
 valuable as those derived from menhaden. 
 
 621. Ammonium sulphate is a by-product in the manu- 
 facture of coal gas, animal charcoal, and coke (93). It is 
 richest in nitrogen of all fertilizing materials, containing 
 from 20 per cent to 23 per cent. It gives excellent results 
 on soils that contain plenty of calcium carbonate. 
 
 622. Nitrate of soda or Chile saltpeter is a crystalline 
 substance somewhat resembling coarse salt in appearance 
 and is entirely soluble in water. It comes from large deposits 
 in Chile which supply over one million tons of nitrate a year 
 to be used as a fertilizer. Chile saltpeter contains from 15 
 per cent to 16 per cent of nitrogen in a form that is immedi- 
 ately available to the plant, and for this reason it is the most 
 desirable nitrogenous fertilizer to use when immediate results 
 are desired. It is not held by the soil and consequently 
 should be supplied only as it can be used by the crop. 
 
 Calcium nitrate as made at the present time in Norway 
 (148) promises to be an important fertilizing material of 
 the future. 
 
 623. Calcium cyanamide (CaCN 2 ) is a new fertilizing 
 material. It is produced by heating calcium carbide (169) 
 to a high temperature in a current of nitrogen until the 
 following reaction takes place : 
 
 CaC 2 + 2 N ->- CaCN 2 + C. 
 
 Calcium cyanamide, called also nitro-lime and lime 
 nitrogen, is a hard gray-black substance resembling coke 
 in appearance and containing about 20 per cent of nitrogen. 
 It decomposes in the soil as follows : 
 
 CaCN 2 + 3 H 2 O -> 2 NH 3 + CaCO 3 . 
 
 EV. CHEM. 34 
 
530 SOILS AND FERTILIZERS 
 
 Because calcium cyanamide has an injurious effect upon 
 the germination of seeds, it should be applied to the soil 
 some time in advance of seeding, so as to permit the 
 change to ammonia to be completed before the seeds 
 germinate. 
 
 624. Low-grade Nitrogen Fertilizers. The high price of 
 nitrogen materials has led to the substitution in some cases 
 of inferior materials for the nitrogen fertilizers described 
 previously. Leather and horn meal, hair and wool wastes, 
 shoddy, dried peat and muck, and garbage tankage all 
 contain nitrogen, but in a condition in which it resists nitrifi- 
 cation and is made available very slowly. 
 
 625. Relative Availability of Nitrogenous Fertilizers. 
 The percentage of nitrogen present in the different fertilizing 
 materials does not properly indicate their relative fertilizing 
 value. Mention has been made repeatedly of the fact 
 that the plant can make use of the nitrogen only when it is 
 present in the form of nitrates. Nitrate of soda is the only 
 fertilizer on the list that contains nitrogen in the nitrate 
 condition, and consequently is the only one that adds 
 nitrogen to the soil in a form which, without further change, 
 is available to the plant. All the other materials must have 
 their nitrogen converted into nitrates before it can be used 
 by the crop. It must be apparent, therefore, that the value 
 of a nitrogenous fertilizer depends upon both its content of 
 nitrogen and the ease with which it is nitrified. 
 
 Of the list mentioned, sulphate of ammonia is the most 
 easily converted into nitrates, provided the soil is abundantly 
 supplied with lime. Next in order comes dried blood. 
 
 The nitrogen in dried fish, tankage, hoof meal, and bone 
 meal is readily changed by nitrification and ranks next to 
 blood meal. Horn meal, on the other hand, decomposes 
 
COMMERCIAL SOURCES OF PLANT FOOD 531 
 
 very slowly, and the nitrification of leather is so slow as to 
 make it practically worthless as a fertilizer. 
 
 Experiments up to date indicate that if nitrate of soda is 
 rated at 100 per cent, the availability of the other materials 
 is as follows : 
 
 Nitrate of soda 100 
 
 Blood 70 
 
 Fish, hoof meal ....... o ... 65 
 
 Bone and tankage 60 
 
 Leather and wool waste 2-10 
 
 626. Suggestions for Using Nitrogen Fertilizers. Two 
 
 or three suggestions for the selection of nitrogen fertilizers 
 may be drawn from this discussion. For those crops that 
 begin their growth early in the spring, the best results will 
 follow the use of Chile saltpeter, as the soil is likely to be 
 low in nitrates and the process of nitrification is slow at 
 that time. Crops that have very short periods of growth 
 will respond best to nitrogen in nitrates. On the other 
 hand, corn and the other crops that make their growth 
 after the season is well advanced can use the slower acting 
 fertilizers, as can also those crops that occupy the ground 
 permanently. Some farmers prefer to use a fertilizer con- 
 taining nitrogen in three forms for the crops that grow during 
 the greater part of the season : a little nitrate of soda for 
 immediate use, sulphate of ammonia to supply the nitrogen 
 a little later, and tankage to carry the plant to maturity, 
 these materials being mixed and applied at one time. 
 
 EXERCISES 
 
 Ex. 374. Explain why phosphorus must be used on every farm. 
 In what ways is phosphorus removed from the farm ? Why is a phos- 
 phorus fertilizer needed even when large quantities of feeds are pur- 
 chased ? Do plants need a balanced ration ? 
 
532 SOILS AND FERTILIZERS 
 
 Ex. 375. What are the commercial sources of phosphorus ? What 
 is meant by raw bone meal ? By steamed bone meal ? Why is steamed 
 bone meal the more valuable ? 
 
 Ex. 376. What are the sources of the mineral phosphates? Why 
 are the mineral phosphates less available than the bone phosphates? 
 What is the theory regarding the use of floats with organic matter ? 
 
 Ex. 377. What is meant by acid phosphate? By what other 
 names is it known? Write the equation for the action of sulphuric 
 acid on mineral phosphate. What may happen if insufficient sul- 
 phuric acid is used? What is meant by reverted phosphate? By 
 available phosphoric acid? How much available phosphoric acid do 
 the acid phosphates contain ? 
 
 Ex. 378. What is basic slag? How much phosphoric acid does 
 it contain ? Is it in an available form ? Why is it desirable to use a 
 phosphate with the stable manure ? Discuss the results obtained with 
 phosphated manure at the Ohio Experiment Station. How is the 
 phosphate best added to the manure ? 
 
 Ex. 379. Why is potassium less likely to be a limiting factor than 
 phosphorus ? What soils are most likely to need potassium ? Discuss 
 the European salts as a source of potassium for fertilizers. What can 
 you say of the value of wood ashes? Why should wood ashes be 
 protected from the weather ? 
 
 Ex. 380. Why is nitrogen sometimes said to be the most important 
 element of plant food ? What are the principal sources of nitrogen for 
 fertilizers? Tell what you can about the packing house by-products. 
 What is the source of ammonium sulphate? What is Chile saltpeter? 
 Calcium cyanamide ? 
 
 Ex. 381. Are all nitrogen materials equal in value? What is 
 meant by the relative availability of nitrogenous fertilizers? What 
 is the order of their availability? Give some suggestions for using 
 nitrogen fertilizers. 
 
A 
 
 CHAPTER LX 
 MIXED FERTILIZERS 
 
 627. Complete Fertilizers. By far the larger part of the 
 commercial fertilizers used by farmers in this country are 
 purchased in the form known as complete fertilizers. A 
 complete fertilizer, in the sense in which the word is used, is 
 one that contains nitrogen, phosphoric acid, and potash, in 
 proportions that are supposed to be suited to the require- 
 ments of farm practice. Almost all these fertilizers are 
 made by mixing two or more of the basic materials heretofore 
 described, the different ingredients being so combined as to 
 give the desired percentage of nitrogen, phosphoric acid, and 
 potash. In case the basic materials alone yield a product 
 that is richer in the essential ingredients than is desired by 
 the manufacturer, sufficient gypsum, dry earth, peat, or other 
 inert matter is added to bring the percentage of these ingre- 
 dients down to the desired point. Materials added in this 
 way are known as fillers. 
 
 628. Home-mixed Fertilizers. If the farmer wishes to 
 do so, he may buy the separate materials previously described 
 and mix them on the farm, and in that way save part of the 
 expense of the manufacture of a complete fertilizer.* There 
 are obvious advantages other than economy in home mixing 
 over the purchase of mixed fertilizers. The usual analysis 
 of a mixed fertilizer gives no clew as to the condition or 
 source of the nitrogen, and it is difficult to determine its 
 availability; while in the homemade mixture the condition 
 
 533 
 
534 
 
 SOILS AND FERTILIZERS 
 
 of the nitrogen can always be known. Home mixing permits 
 the uniting of the different elements in the proportions that 
 have been found best to mejet the requirements of the crop 
 and the soil on which it is to be raised, something that is 
 not easily managed with factory mixed fertilizers. By 
 buying the basic materials separately it is possible to apply 
 
 the different elements 
 at different times, a 
 point that is sometimes 
 of great advantage in 
 feeding a crop, es- 
 pecially if it is one that 
 needs large quantities 
 of nitrogen. In fact 
 the only advantage that 
 can consistently be 
 claimed for the mixed 
 goods is that they are 
 
 FIG. 243. Mixing fertilizers on the farm. ,-, v , M 
 
 more generally distrib- 
 uted in the market than the basic materials and can, 
 therefore, be more easily purchased in such amounts and at 
 such times as are convenient. 
 
 A tight barn floor, a straight-edged shovel, and a wire 
 screen, such as is used for screening ashes, are the only 
 requisites for the home mixing of fertilizers (Fig. 243). The 
 mixer weighs the materials and spreads them upon the floor 
 in layers one upon the other. Then beginning at one end 
 he shovels the whole through the screen, repeating the 
 operation three or four times, or until he attains a fairly 
 uniform mixture. 
 
 629. Buying Fertilizers. In order to protect the pur- 
 chaser, most of the states have passed laws compelling the 
 
MIXED FERTILIZERS 535 
 
 manufacturer to guarantee the amount of plant food in 
 each brand of fertilizer offered for sale. The enforcement 
 of these laws and the chemical examination of the fertilizers 
 to determine if they agree with the guarantee are intrusted 
 to the experiment stations in some states, while in others 
 they are in the hands of the State Department of Agriculture. 
 The results of the analyses are published in bulletins for 
 free distribution, and these should be generally consulted 
 by farmers using fertilizers. 
 
 Fertilizers should be purchased absolutely on the basis 
 of the plant food that they contain, and no attention should 
 be paid to the name of the brand, which usually bears no 
 relation to the usefulness of the fertilizer. For the sake of 
 simplicity the analysis of a fertilizer is stated briefly in the 
 following manner: as a 3-10-4, the figures meaning that 
 the fertilizer contains 3 per cent of nitrogen, 10 per cent 
 of available phosphoric acid, and 4 per cent of potash, the 
 ingredients always being stated in the same order. 
 
 630. Need of Knowing What Fertilizer Is Required. To 
 buy fertilizers intelligently the farmer must first know the 
 requirements of the crop and the condition of the soil. A 
 soil that is deficient in phosphorus, for instance, will not be 
 much benefited by a fertilizer very low in phosphorus, even 
 though such a fertilizer may be valuable on other land. Un- 
 fortunately there is no easy way of determining accurately 
 the immediate fertilizer requirements of a given soil for a 
 particular crop. 
 
 631. Need of Studying the Growing Crop. In a general 
 way, the crops themselves may give some valuable suggestions. 
 
 (a) As a rule, lack of nitrogen is indicated when plants 
 are pale green, or when there is small growth of leaf and 
 stalk, other conditions being favorable. 
 
536 SOILS AND FERTILIZERS 
 
 (b) A bright, deep green color with a vigorous growth of 
 leaf or stalk is, in the case of most crops, a sign that nitrogen 
 is not lacking ; but such conditions do not necessarily indicate 
 that more nitrogen could not be used to advantage. 
 
 (c) An excessive growth of leaf or stalk, accompanied by 
 an imperfect bud, flower, and fruit development indicates 
 too much nitrogen for the potash and phosphoric acid 
 present. 
 
 (d) When such crops as corn, cabbage, grass, and potatoes 
 have a luxuriant, healthful growth, an abundance of potash 
 in the soil is indicated. When fleshy fruits of fine flavor 
 and texture can be successfully grown, the same condition 
 is indicated. 
 
 (e) When a soil produces good, early maturing crops of 
 grain, with plump and heavy kernels, phosphoric acid will 
 not generally be lacking. A good growth of straw with a 
 small yield of grain, on the other hand, shows that the soil 
 does not contain sufficient phosphorus to balance the nitrogen 
 and potash. 
 
 Such general indications may often be helpful, and crops 
 shojild be studied carefully with these facts in mind. 
 
 632. Field Experiments. The only reliable way of ascer- 
 taining the proper fertilizer to use on a given field is to 
 compel the soil itself to answer the question. This may be 
 done by an easily conducted field experiment. This experi- 
 ment consists in dividing a small portion of the field into 
 small plots (Fig. 244) on each of which a different kind of 
 fertilizer is used, the yield being compared with the yield of 
 check plots to which no fertilizing material has been added. 
 Since the different crops vary in their power to extract plant 
 food from the soil, these experiments should cover the entire 
 rotation. 
 
MIXED FERTILIZERS 
 
 537 
 
 633. Conducting the Experiment. The first important 
 consideration in an experiment of this kind is the selection 
 of the location for the plots. The spot selected should rep- 
 resent as nearly as possible the average condition of the 
 entire field. The soil should be uniform in quality over the 
 entire area devoted to the experiment, so that one may be sure 
 that any difference in yield from the several plots is not due 
 to variation in the composition of the soil. Plots one rod 
 
 FlG. 244. View of a field plot test with fertilizers. 
 
 wide and eight rods long will be found a convenient size 
 for this purpose, but those of any size may be used. The 
 simplest experiment that will give any, reliable information 
 calls for a row of at least seven plots, with a space of at least 
 2 feet between each plot. The ground is first plowed and 
 harrowed and then the plots are measured out, each corner 
 being marked by a stake driven well into the ground. The 
 fertilizers for each division are mixed and applied by hand, 
 care being used not to scatter the material beyond the plot 
 for which it is intended. The diagram (Fig. 245) shows the 
 
538 SOILS AND FERTILIZERS 
 
 arrangement of the plots and the kind and quantity of fer- 
 tilizing material to be used on each. 
 
 1 
 
 No Fertilizer 
 
 
 2 
 
 15 Ib. Nitrate of Soda 
 15 Ib. Sulphate of Potash 
 30 Ib. Acid Phosphate 
 
 
 3 
 
 30 Ib. Acid Phosphate 
 15 Ib. Sulphate of Potash 
 
 
 4 
 
 No Fertilizer 
 
 
 5 
 
 15 Ib. Nitrate of Soda 
 15 Ib. Sulphate of Potash 
 
 
 C 
 
 15 Ib. Nitrate of Soda 
 30 Ib. Acid Phosphate 
 
 
 7 
 
 No Fertilizer 
 
 FIG. 245. Arrangement of plots and quantity of fertilizer used in conducting 
 a field experiment. 
 
 The plots may be seeded separately, but it saves labor 
 and gives practically as good results if they are planted with 
 the rest of the field. In any case the seeder must be run 
 lengthwise of the plots so as to avoid dragging any of the 
 fertilizer from one plot to another. 
 
 634. Harvesting the Crop. The area devoted to the 
 experiment should receive exactly the same treatment 
 during the growing season as the rest of the field, except that 
 
MIXED FERTILIZERS 539 
 
 in no case is cross cultivation of the plots allowable. If the 
 crop is one that is planted in rows and intertilled, it will 
 be best to harvest the same number of rows from the center 
 of each plot, discarding the outer rows. In the case of small 
 grains, a cord is stretched from stake to stake to outline 
 the plots and the grain is first removed from the intervening 
 spaces. This leaves each plot standing out so distinctly 
 that it can be readily observed and the crop can easily be 
 harvested. The weight of both grain and straw from each 
 plot should be determined. 
 
 635. Interpreting the Results. The yield from each of the 
 check plots should be practically the same. If this is the 
 case, it shows that the soil in the area devoted to the experi- 
 ment is uniform in character. A little thought will show 
 how to decide from the experimental data what elements of 
 fertility give satisfactory results with the crop and soil 
 under investigation. If the yield on all the plots is about the 
 same, for instance, it will be evident that no beneficial 
 results can be expected on that soil from the use of commercial 
 fertilizers. If plot number 2 gives higher results than any of 
 the others, it is to be concluded that nitrogen, phosphoric 
 acid, and potash are all required. If plots 2, 3, and 6 
 give larger yields than the checks, and 5 does not, the indi- 
 cation is that phosphoric acid alone is necessary. An 
 increased yield on 2, 3, and 5 but not on. 6 indicates need of 
 potash. A larger crop on 2, 5, and 6 but not on 3 shows need 
 of nitrogen. A large increase in yield over the checks on 2 
 and 6 and a smaller increase on 3. and 5 suggest that both 
 nitrogen and phosphoric acid are beneficial but potash is 
 not ; and so on. 
 
 Experiments similar to these are being conducted by many 
 of the state experiment stations on the different types of soil 
 
540 SOILS AND FERTILIZERS 
 
 found in the several states, so as to assist the farmer in 
 determining what kinds of fertilizers are needed for his 
 particular farm. 
 
 636. Commercial Fertilizers Not All-sufficient. Absolute 
 dependence should not be placed on commercial fertilizers 
 alone to maintain the fertility of the land. Commercial 
 fertilizers add little or no humus to the soil, and to obtain 
 the best results it is absolutely necessary to provide humus, 
 either by plowing under green crops or by the use of barnyard 
 manure. Numerous experiments have shown that com- 
 mercial fertilizers give much better returns when used in 
 connection with barnyard manure than if used alone, and 
 they are coming into use in this manner more and more as 
 the subject is more thoroughly investigated. 
 
 It may be said in this connection that commercial fertilizers 
 are not merely stimulants, as is frequently imagined, but 
 that they actually supply plant food. If rationally used, 
 they will leave the soil more fertile than before their use, 
 instead of decreasing its fertility, as would happen if a mere 
 stimulant were used. Commercial fertilizers have an im- 
 portant place in the rural economy ; but they should not be 
 used to do the work that can better be accomplished by 
 proper husbanding of home rssources. 
 
 EXERCISES 
 
 Ex. 382. What is meant by a complete fertilizer? How are 
 complete fertilizers made? What is meant by a filler? Find the 
 brand names and the analyses of the fertilizers used by the farmers 
 in your locality. 
 
 Ex. 383. What are the advantages of the home mixing of ferti- 
 lizers? How should you proceed to make a home-mixed fertilizer? 
 How could you make a 3-10-4 fertilizer from the following materials : 
 Nitrate of soda containing 16 % nitrogen, acid phosphate containing 
 
MIXED FERTILIZERS 541 
 
 16 % phosphoric acid, and muriate of potash containing 50 % potash? 
 How much filler would be required ? 
 
 Ex. 384. What does a farmer need to know before buying a fer- 
 tilizer? Upon what basis should the fertilizer be purchased? How 
 much attention should be paid to the name of the fertilizer? Explain 
 how the crop may indicate what fertilizer is needed. 
 
 Ex. 385. Describe a field experiment to determine the fertilizer 
 requirements of a soil. The following results were obtained in an actual 
 experiment similar to the one described : plots 1, 4, and 7 yielded 10 
 bushels of wheat to the acre. Plots 2, 3, 5, and 6 yielded 26, 19, 13, 
 and 23 bushels in the order named. Were all three elements of fer- 
 tility needed? Can you tell which element was most needed? Does 
 the experiment show whether there was more need of potash or nitrogen ? 
 
 Ex. 386. In another actual experiment plots 1, 4, and 7 produced 
 only 6 bushels of wheat to the acre. Plots 2, 3, 5, and 6 produced 19, 
 16, 9, and 19 bushels in the order named. What elements are needed 
 in this soil ? Which element appears to be most needed ? 
 
CHAPTER LXI 
 TYPES OF FARMING AND FERTILITY 
 
 637. Some Fertilizer Always Needed. While soils vary 
 greatly in their original fertility, so that it is customary to 
 speak of rich and poor soils, it is also true that none of them 
 can long produce crops without the addition of some kind of 
 fertilizing material. Any system of farming that is to 
 succeed through a long period of years must provide some 
 method of replacing practically all the plant food removed, 
 no matter how rich the soil was in its virgin condition. 
 
 Each farm is in a measure a special study ; but the work 
 done by the various agricultural experiment stations makes 
 it possible to formulate a few important generalizations. 
 If the farms are properly drained, if tillage is thorough and 
 rational, if limestone has been added where necessary, and 
 if crops are rotated, the system of fertilization necessary for 
 best results in the various types of farming would be about 
 as outlined in the following sections. 
 
 638. All Crops Sold. Where all the crops, including 
 straw and hay, are sold from the farm, the fertility of the 
 soil is quickly exhausted unless fertilizers are freely used. 
 In this case dependence must be placed upon fertilizers 
 that supply nitrogen, phosphorus, and potassium, and a 
 sufficient quantity -must be used to replace practically all 
 the plant food removed from the soil. Some difference of 
 opinion exists as to whether the fertilizer should be used 
 wholly on the cereals, or on the hay crop as well. An 
 
 542 
 
TYPES OF FARMING AND FERTILITY 543 
 
 experiment on this type of farming which has been running 
 for twenty years at the Ohio Experiment Station, an 
 experiment in which the rotation followed was corn, oats, 
 wheat, clover, and timothy and in which the fertilizer 
 was used on the corn, oats, and wheat, gave an annual 
 profit for the use of the fertilizer of $3.53 an acre over 
 and above the cost of the application. The total fertilizing 
 materials used on the three grain crops during each rotation 
 consisted of 480 pounds of nitrate of soda, 320 pounds of 
 acid phosphate, and 260 pounds of muriate of potash. Later 
 experiments indicate that less nitrogen and potassium and 
 more phosphorus would have given greater profit. Under 
 the best of circumstances, however, the total possible profit 
 from this type of farming is comparatively small. 
 
 639. Grains Only Sold. In the end it will probably be 
 found more profitable to sell the grain only and return the 
 straw and clover for their manurial effects. A four-year 
 rotation of corn, oats, wheat, and clover will serve as an 
 example. In this type of farming the only loss is in phos- 
 phorus, provided the clover, straw, and cornstalks are 
 plowed under ; for in this case the fixation of nitrogen by the 
 clover should make up for that sold in the grain. The only 
 commercial fertilizer that need be purchased, therefore, is 
 acid phosphate or some other carrier of phosphoric acid. 
 This type of farming is being recommended for the great 
 grain-growing and cotton-growing sections. 
 
 640. Dairy Farming. The type of farming in which 
 fertility is most easily maintained is the one devoted wholly 
 to dairying, in which only such crops are raised as can be 
 fed on the farm. The dairy farmer finds it profitable in 
 milk production to purchase quantities of concentrated 
 feeds, and thereby bring plant food to the farm. To reen- 
 
544 SOILS AND FERTILIZERS 
 
 force the manure he should purchase acid phosphate which 
 is preferably used in the stable at the rate of one pound a 
 day for each animal (612). Under these conditions the farm 
 will increase in fertility if the manure is properly preserved. 
 One run-down farm that was producing only 30 bushels of 
 corn to the acre was made to yield 85 bushels to the acre 
 within eight years by this method of farming. 
 
 641. Fat Stock Farming. The same general principles 
 apply in this case as in dairy farming; but as the stock 
 feeder usually does not buy as much feeding stuffs as the 
 dairyman, the farm is not so easily maintained in a high state 
 of fertility. 
 
 642. Mixed Farming. Most of the farms of this country 
 are managed by the system known as mixed farming, in 
 which some of the crops are sold directly and the rest fed 
 to the animals and marketed as animal products. Under 
 this system all the manure should be carefully saved, ree'n- 
 forced with some phosphate material, and applied to the 
 land that is to be plowed for corn, provided that crop ap- 
 pears in the rotation. Additional phosphorus should be 
 used on the small grains, especially upon wheat if grown, 
 since they respond readily to such treatment. In case the 
 land is not in a high state of fertility it may also be found 
 profitable to use small quantities of nitrogen and potassium 
 on the wheat. At the Ohio Experiment Station there is a 
 tract of forty acres which is being managed according to 
 this system. The rotation is corn, oats, wheat, and clover, 
 with ten tons to the acre of phosphated .manure applied to 
 the corn, and chemical fertilizers to the wheat. In the 12 
 years that this plan has been in operation the yields of the 
 several crops have increased as follows : corn from 34 to 78 
 bushels, oats from 30 to 60 bushels, wheat from 15 to 34 
 
TYPES OF FARMING AND FERTILITY 545 
 
 bushels, and clover hay from 2000 to 6400 pounds to the 
 acre, with indications that the maximum yields have not 
 yet been reached. 
 
 A great many of the farms devoted to mixed farming do 
 not produce sufficient manure to make possible the applica- 
 tion of ten tons to each acre once in four years. In such 
 cases it will probably be necessary to resort to the occasional 
 use of some form of green manuring if the yields are to be 
 maintained at a high level. 
 
 643. Special Crops. There are certain so-called special 
 crops on which it has long been customary to use large 
 quantities of commercial fertilizers. These crops, among 
 which are tobacco, sugar beets, potatoes, onions, cotton, and 
 celery, bring relatively high prices per acre, and consequently 
 are more likely to give profitable returns for heavy fertili- 
 zation than are the ordinary farm crops. It is quite a com- 
 mon practice to use from 1000 to 2000 pounds to the acre 
 of a high-grade chemical mixture containing all the elements 
 of fertility upon these special crops. While this practice 
 gives good profits under favorable conditions, there is need 
 of much more experimental work with these plants before 
 it can safely be assumed that this is the most economical 
 and profitable scheme of fertilization even for these high- 
 priced crops. Onions and celery, it should be noted, are 
 frequently grown on a muck or peaty, soil, in which case 
 the need of potassium in the fertilizer is evident. 
 
 644. Market gardening may be said to be one of the most 
 intensive forms of farming. The areas farmed are small, 
 and a large amount of hand labor is involved. The money 
 returns for each acre are relatively large, and the gardener is 
 justified in making large expenditures to maintain fertility. 
 The mechanical condition of the soil is of prime importance, 
 
 EV. CHEM. 35 
 
546 SOILS AND FERTILIZERS 
 
 especially in the production of the root crops, such as radishes, 
 carrots, parsnips, and beets. The best practice is to use 
 composted manure in large quantities, supplementing it 
 with green manures, if the supply of stable manure is not 
 sufficient to maintain a high percentage of organic matter 
 in the soil. The Chinese, who are excellent gardeners, grow 
 clovers and other legumes which they compost with earth 
 and use in lieu of composted stable manure. Since it is 
 becoming increasingly difficult for most gardeners to secure 
 stable manure, this practice of the Chinese gardener may 
 be found to be useful in this country under some conditions. 
 Phosphoric acid and potash fertilizers should be used in 
 abundance, preferably in the compost, since they are re- 
 tained by the soil, and extra nitrogen should be supplied in 
 the form of nitrate of soda as needed by the crops. Nitrate 
 of soda is especially valuable for the leafy crops that make 
 their growth in the early spring, such as spinach, lettuce, early 
 cabbage and cauliflower, asparagus, and rhubarb. The prices 
 obtained from these crops depend largely upon their earliness, 
 and nitrate of soda forces them into rapid growth. Peter 
 Henderson tells of one case in which an acre of very early 
 cauliflower sold for $1000, while an adjoining acre which, 
 because of improper fertilization, was two weeks later in 
 reaching the market brought only $200. 
 
 645. Orcharding. In too many cases the orchard receives 
 no fertilizer of any kind, and yet on many soils the orchard 
 fruits give handsome returns for fertilization. Either manure, 
 commercial fertilizers, or both may be used with good results. 
 Cover crops, which can be plowed under or used around the 
 trees as a mulch, are of assistance in fertilizing an orchard. 
 The frontispiece shows how readily apple trees respond to 
 fertilizers on some soils. 
 
TYPES OF FARMING AND FERTILITY 547 
 
 646. Permanent Pastures. The most neglected part of 
 the average American farm is the area devoted to the per- 
 manent pasture. It seems to be assumed that the soil 
 can produce pasture grasses indefinitely without fertiliza- 
 tion, and these areas in the older parts of the country show 
 the effect of such neglect. The pastures should be as care- 
 fully fertilized as any part of the farm. The best fertilizer 
 to use when it is available is phosphated stable manure 
 applied with the manure spreader. Permanent pastures 
 have a tendency to become acid and, therefore, should 
 receive occasional applications of limestone. When stable 
 manure is not available chemical fertilizers may be used to 
 advantage. Acid phosphate or bone meal should be used 
 freely with a moderate amount of potash salts. The addition 
 of nitrate of soda will encourage the growth of the true 
 grasses, such as blue grass, but if it is desired to promote 
 the growth of the clovers rather than the grasses the nitrate 
 should be omitted. The pastures should be dragged from 
 time to time to distribute the droppings of the animals, and 
 they are also benefited by an occasional clipping with the 
 mowing machine. 
 
 EXERCISES 
 
 Ex. 387. Will any soil produce crops indefinitely without fertiliza- 
 tion ? Name four things that are fundamental to soil fertility. How 
 can fertility be maintained if all the crops' are sold from the farm? 
 What can you say of the probable profit of this type of farming if long 
 continued? Could the fertility be more readily maintained if only 
 the grains were sold? What fertilizer would need to be supplied in 
 that case? Explain. Under what circumstances is this type of farm- 
 ing recommended ? 
 
 Ex. 388. How may the fertility be maintained on dairy farms? 
 Why is it desirable to add a phosphate to the manure even when con- 
 centrates are purchased? Are there any dairy or stock farms near 
 
548 SOILS AND FERTILIZERS 
 
 the school ? Is the manure properly cared for on these farms? Ascer- 
 tain whether any of the farmers use phosphate with the manure. 
 
 Ex. 389. What is meant by mixed farming? If a farm used a 
 rotation of corn, oats, wheat, and clover, and all the wheat and half 
 the corn and oats were sold, and the other materials were used on the 
 farm, what plan of fertilization should you recommend for the farm ? 
 Explain why. When is green manuring advisable in mixed farming ? 
 
 Ex. 390. Tell what you can about fertilizers for special crops. 
 If any of the special crops named in the text are grown in your neigh- 
 borhood report on the fertilizer used on them. Why is the mechanical 
 condition of the soil of prime importance in market gardening ? What 
 is the best way to improve the mechanical condition of the soil ? Why 
 is nitrate of soda especially valuable to the market gardener ? In case 
 stable manure cannot be procured how may the amount of compost 
 be increased? 
 
 Ex. 391. Does it pay to fertilize the orchard ? What method may 
 be used ? What is meant by a cover crop ? Are there any orchards 
 in your vicinity in which cover crops are used ? What kinds ? What 
 can you say about the need of fertilizing the permanent pastures? 
 What is the best fertilizer for pastures? What chemicals should you 
 recommend if blue grass was especially desired? What other treat- 
 ment should you suggest for the pastures? 
 
APPENDIX 
 
 (a) LIST OF CHEMICALS NEEDED FOR A CLASS OP 
 TWELVE 
 
 These chemicals may be of the grade known as "Pure" and need 
 not be of the more expensive C. P. grade. 
 
 2 Ib. Acid, acetic 
 
 4 oz. Acid, arsenious 
 
 2 oz. Acid, benzoic 
 
 4 oz. Acid, boric 
 
 4 oz. Acid, carbolic 
 
 4 oz. Acid, citric, crystals 
 
 6 Ib. Acid, hydrochloric 
 
 2 oz. Acid, lactic 
 
 6 Ib. Acid, nitric 
 
 4 oz. Acid, oxalic, crystals 
 
 4 oz. Acid, phosphoric 
 
 1 oz. Acid, salicylic 
 
 18 Ib. Acid, sulphuric, commercial 
 9 Ib. Acid, sulphuric, pure 
 
 2 oz. Acid, tannic 
 
 4 oz. Acid, tartaric, crystals 
 
 1 gal. Alcohol, denatured 
 
 1 pt. Alcohol, grain 
 
 1 qt. Alcohol, wood 
 
 8 oz. Alum, ammonium 
 
 8 oz. Alum, chrome 
 
 8 oz. Alum, ferric 
 
 8 oz. Alum, potassium 
 
 1 Ib. Aluminum sulphate 
 
 1 Ib. Ammonium carbonate 
 
 1 Ib. Ammonium chloride 
 
 8 Ib. Ammonium hydroxide 
 
 2 oz. Ammonium molybdate 
 1 Ib. Ammonium nitrate 
 
 1 Ib. Ammonium sulphate 
 8 oz. Barium chloride 
 8 oz. Barium hydroxide 
 8 oz. Barium nitrate 
 1 can Bleaching powder 
 
 1 Ib. Calcium carbide 
 8 oz. Calcium carbonate, precipi- 
 tated 
 
 1 Ib. Calcium chloride 
 1 Ib. Calcium fluoride 
 1 oz. Calcium metal 
 1 Ib. Calcium phosphate 
 
 1 Ib. Calcium sulphate 
 
 2 Ib. Carbon bisulphide 
 
 1 Ib. Carbon tetrachloride 
 1 Ib. Carborundum 
 1 Ib. Charcoal, animal 
 1 Ib. Charcoal, wood 
 8 oz. Chloroform 
 
 1 oz. Cobalt nitrate 
 
 2 oz. Cochineal bugs 
 4 oz. Collodion 
 
 4 oz. Copper oxide, coarse 
 
 5 Ib. Copper sulphate 
 8 oz. Copper turnings 
 
 4 oz. Cresol 
 
 1 Ib. Dextrose, lump 
 1 Ib. Ether 
 
 5 Ib. Formaldehyde 
 8 oz. Gfall nuts 
 
 1 Ib. Glycerin 
 
 4 oz. Gum arabic 
 4 oz. Gum damar 
 4 oz. Hydrogen peroxide 
 
 2 oz. Iodine 
 
 4 oz. Iron ammonium citrate 
 1 Ib. Iron pyrites 
 1 Ib. Iron sulphate 
 1 Ib. Iron sulphide 
 
 549 
 
550 
 
 APPENDIX 
 
 (a) LIST OF CHEMICALS NEEDED (Continued) 
 
 1 Ib. Kaolin 
 
 4 oz. Lampblack 
 
 1 Ib. Lead acetate 
 1 Ib. Lead arsenate 
 1 Ib. Lead metal 
 1 Ib. Lead oxide, red 
 
 1 Ib. Lead oxide, yellow 
 
 5 vials Litmus paper, blue 
 5 vials Litmus paper, red 
 4 oz. Litmus solution 
 
 4 oz. Logwood extract 
 4 oz. Magnesium chloride 
 
 2 oz. Magnesium powder 
 2 oz. Magnesium ribbon 
 
 8 oz. Magnesium sulphate 
 
 1 oz. Maltose 
 
 2 Ib. Manganese dioxide 
 2 Ib. Mercury 
 
 2 oz. Mercury bichloride 
 1 Ib. Naphthalene 
 1 Ib. Oil, cottonseed 
 1 Ib. Oil, linseed, boiled 
 1 Ib. Oil, linseed, raw 
 8' oz. Oil, olive 
 1 oz. Oil, wintergreen 
 
 1 oz. Pancreatin 
 
 2 Ib. Paraffin 
 
 8 oz. Paris green 
 2 oz. Pepsin, scale 
 1 Ib. Petrolatum 
 
 1 oz. Phenolphthalein 
 
 2 oz. Phosphorus, red 
 
 2 oz. Phosphorus, yellow 
 
 1 oz. 5% sol. Platinum chloride 
 
 1 Ib. Potassium bichromate 
 
 1 Ib. Potassium bitartrate 
 
 2 oz. Potassium bromide 
 
 1 Ib. Potassium carbonate 
 
 2 Ib. Potassium chlorate 
 8 oz. Potassium chloride 
 
 2 oz. Potassium cyanide 
 
 4 oz. Potassium ferricyanide 
 
 8 oz. Potassium hydroxide, sticks 
 
 2 oz. Potassium iodide 
 
 1 oz. Potassium metal 
 
 1 Ib. Potassium nitrate 
 
 8 oz. Potassium permanganate 
 
 1 Ib. Potassium sulphate 
 
 2 Ib. Rochelle salts 
 
 1 Ib. Rosin, common 
 4 oz. Shellac 
 
 2 oz. Silver nitrate 
 1 Ib. Soda lime 
 
 1 Ib. Sodium acetate 
 4 oz. Sodium arsenite 
 
 2 oz. Sodium benzoate 
 
 1 Ib. Sodium bicarbonate 
 1 Ib. Sodium borate 
 
 1 Ib. Sodium carbonate 
 
 4 Ib. Sodium hydroxide, sticks 
 
 2 Ib. Sodium hyposulphite 
 2 oz. Sodium metal 
 
 2 Ib. Sodium nitrate 
 
 4 oz. Sodium nitrite 
 
 8 oz. Sodium peroxide 
 1 Ib. Sodium phosphate 
 1 gal. Sodium silicate 
 1 Ib. Sodium sulphate 
 
 1 Ib. Sodium sulphite 
 
 2 Ib. Sulphur, flowers of 
 
 8 oz. Sulphur, precipitated 
 2 Ib. Sulphur, roll 
 1 Ib. Turpentine 
 1 oz. Vermilion 
 
 5 Ib. Zinc, mossy 
 8 oz. Zinc chloride 
 1 Ib. Zinc dust 
 
 1 Ib. Zinc oxide 
 1 Ib. Zinc sulphide 
 
APPENDIX 
 
 551 
 
 (6) SUBSTANCES WHICH MAY BE OBTAINED LOCALLY 
 AS REQUIRED 
 
 Absorbent cotton 
 
 "Ammo" solid ammonia 
 
 Ammonia, household 
 
 Candles 
 
 Chloride of lime 
 
 Coal, hard 
 
 Coal, soft 
 
 Coke 
 
 Cream of tartar 
 
 Dry cells 
 
 Fertilizing materials 
 Gasoline 
 Gelatin, Jello 
 Grain products : 
 
 Barley 
 
 Corn meal 
 
 Dextrin 
 
 Flaxseed 
 
 Malt 
 
 Oats 
 
 Various starches 
 
 Wheat flour 
 Graphite 
 
 Insect powders pyrethrum 
 Insecticides, nicotine 
 Iron, cast 
 Iron, wrought 
 Karo sirup 
 Kerosene 
 Lime 
 
 Limestone and marble 
 Milk products : 
 
 Butter 
 
 Buttermilk 
 
 Condensed milk 
 
 Powdered milk 
 
 Renovated butter 
 
 Skim milk 
 
 Whole milk 
 Miscellaneous fats : 
 
 Cocoanut oil 
 
 Cottolene 
 
 Crisco 
 
 Lard 
 
 Oleomargarine 
 
 Tallow 
 
 Paints and varnishes 
 Paraform or formacone 
 Petroleum, crude 
 Picture frame wire 
 Plaster of Paris 
 Portland cement 
 Raisins 
 
 Rennet extract 
 Salt 
 
 Sapolio and scouring soaps 
 Soap powders 
 Soaps, various 
 Steel 
 Sugar 
 Textiles : 
 
 Cotton cloth 
 
 Linen cloth 
 
 Mixed cotton and wool 
 
 Silk cloth 
 
 Woolen cloth 
 Vinegars 
 Wood ashes 
 Yeast, compressed 
 
552 
 
 APPENDIX 
 
 (c) APPARATUS FOR GENERAL USE 
 
 Figure numbers refer to illustrations of the apparatus in the text. 
 Homemade apparatus may be prepared as substitutes for many of 
 the articles in lists c and d. 
 
 Balance Capacity 2 pounds sen- 
 sitive to 0.1 gram (Fig. 59) 
 
 Apparatus for electrolytic dissocia- 
 tion of water (Fig. 49) 
 
 Eudiometer (Fig. 54) 
 
 Air pump (Fig. 31) 
 
 Microscope 
 
 Water oven (Fig. 142) 
 
 Babcock testing outfit with glass- 
 ware for milk, skim milk, and 
 cream (Figs. 164-170) 
 
 Quevenne lactometer (Fig. 171) 
 
 Truog soil tester (Fig. 226) 
 
 Graham-McCall drainage appara- 
 tus (Fig. 206) 
 
 Soil auger (Fig. 193) 
 
 Gasoline blast torch (Fig. 5) 
 
 Magnet 
 
 Set of cork borers (Fig. 13) 
 
 2 matched F. thermometers (Fig. 
 
 40) 
 
 1 centigrade thermometer (Fig. 3C) 
 Separatory funnel (50 cc.) (Fig. 84) 
 Small piece platinum wire 
 Large glass tubes or lamp chimneys 
 
 (Fig. 204) 
 One quart sprayer for oat smut 
 
 exercise 
 
 Tall glass cylinder 
 Small combustion burner (Fig. 44) 
 Mortar and pestle 
 
 (d) APPARATUS REQUIRED FOR EACH STUDENT WHO 
 IS TO PERFORM THE EXPERIMENTS 
 
 10 ft. small glass tubing, 5 mm. 
 Bunsen burner or alcohol lamp 
 
 (Figs. 1, 2) 
 
 Corks, common and 2-hole rubber 
 6 test tubes, common 
 Test tube, hard glass 
 Test tube brush 
 
 Evaporating dish, 2 in. (Fig. 27) 
 Florence flask, 500 cc. (Fig. 25) 
 Florence flask, 1000 cc. (Fig. 12) 
 Condenser (Fig. 28) 
 Bottles of various sizes 
 Watch glass, 2| in. (Fig. 37) 
 
 1 ft. hard glass tubing, 1| cm. 
 
 2 beakers (500 cc. and 250 cc.) 
 
 (Fig. 15) 
 
 Pinchcock 
 
 CaCl 2 drying tube (Fig. 48) 
 
 Thistle tube (Fig. 46) 
 
 Funnel, 2 in. (Fig. 20) 
 
 Crucible, porcelain (Fig. 83) 
 
 Graduated glass cylinder, 100 cc. 
 
 (Fig. 172) 
 Triangular file 
 Rat-tail file 
 Blow pipe (Fig. 125) 
 Ring stand with rings and clamps 
 
 (Fig. 20) 
 Wire gauze 
 
 Glass plates, 3 in. x 3 in. 
 Asbestos paper 
 
INDEX 
 
 Numbers immediately following titles refer to pages of the text. Those 
 following the abbreviation "Ex." refer to numbers of the experiments. 
 
 Acetic acid, 256, Ex. 164 
 
 from wood, 257 
 Acetylene, 247, Ex. 158 
 Acid phosphate, 190, Ex. 113 
 Acid resistant plants, 482 
 Acids, 154, 156, 157 
 Affinity, chemical, 101 
 Air, 70 
 
 a mechanical mixture, 71 
 
 contains carbon dioxide, 73, Ex. 44 
 
 contains warter vapor, 72, Ex. 43 
 
 liquid, 75 
 
 Albumin, 283, Ex. 198, Ex. 199 
 Albuminoids, 284 
 Alcoholic beverages, 251 
 Alcohols, 250-254 
 
 are bases, 252 
 
 denatured, 252 
 
 grain, 250 
 
 wood, 250 
 Alkali, 156, Ex. 94 
 
 in cleaning, 407 
 Alkaloids, 286 
 Allotropy, 81 
 Alloys, 231, Ex. 145 
 Aluminum, 214 
 
 occurrence of, 215 
 
 preparation of, 215 
 
 test for, 219 
 
 Aluminum sulphate, 216 
 Alums, 216, Ex. 131 
 Amines, 285 
 Ammonia, 171, Ex. 103 
 
 composition of, 173 
 
 from organic matter, 172, Ex. 104 
 
 in ice making, 177 
 
 manufacture of, 173 
 
 occurrence of, 178, Ex. 110 
 
 test for, 179 
 
 Ammonia water, 171 
 
 neutralizes acids, 174, Ex. 106 
 Ammonium carbonate, 177 
 Ammonium chloride, 176 
 Ammonium hydroxide, 174 
 Ammonium nitrate, 176 
 Ammonium sulphate, 176 
 Amylopsin, 320 
 Analysis, 56 
 Anhydride, 159 
 Antiseptics, 389 
 Aqua ammonia, 171 
 Aqua fortis, 165 
 Aquaregia, 165 
 Arsenates, 191 
 Arsenic, 190 
 Arsenites, 191, Ex. 114 
 Ash, in plants, 290 
 Atomic theory, 91, 92 
 
 applied, 93 
 Atomic weights, 93 
 
 Babcock formula, 372 
 Babcock test, 364 
 
 composite test, 370 
 
 for buttermilk, 368 
 
 for cheese, 370 
 
 for cream, 369 
 
 for milk, 365 
 
 for skim milk, 368 
 Bacterial diseases of plants, 418 
 Baking powders, 380, Ex. 266 
 
 homemade, 381, Ex. 268 
 Baking soda, 150, 380 
 Balanced rations, 331 
 
 calculating, 334 
 
 for human beings, 342 
 Bases, 154, 156, 157 
 Basic slag, 189, 222, 524 
 
 553 
 
554 
 
 INDEX 
 
 Beehive coke oven, 114 
 
 Benzine, 247 
 
 Benzoic acid, 259, Ex. 170 
 
 Bile, 321 
 
 Bleaching, 396, Ex. 285 
 
 Bleaching powder, 147, Ex. 88 . . 
 
 Blue prints, 238, Ex 152 
 
 Blue vitriol, 233 
 
 Boiled oil, 399 
 
 Bone black, 113, Ex. 68 
 
 Borax, 198, Ex. 119 
 
 Bordeaux mixture, 233, 416, Ex. 304 
 
 Boric acid, 198 
 
 test for, 199, Ex. 120 
 Boron, 199 
 Bread, 375 
 Brick making, 218 
 Buhach, 413 
 Bulgaris milk, 361 
 Butter, 264, 357 
 
 renovated, 265 
 Buttermilk, 358 
 Butyric acid, 264 
 
 Caffeine, 286 
 Calcite, 134 
 Calcium, 138, Ex. 81 
 Calcium carbonate, 134 
 Calcium cyanamide, 182, 529 
 Calcium hydroxide, 136 
 Calcium oxide, 135 
 Calcium phosphates, 188 
 Calcium sulphate, 139, Ex. 82 
 Calories, 327 
 Calorimeter, 326 
 Carbohydrates, 270 
 
 changes in plant?, 306 
 
 formation in plants, 301, Ex. 
 
 215 
 Carbon, 111-120 
 
 in organic matter, 115, Ex. 66 
 
 properties of, 115 
 
 reducing agent, 115, Ex. 67 
 Carbon bisulphide, 130, 414, Ex. 77, 
 
 Ex. 303 
 
 Carbon compounds, 123, 244 
 Carbon cycle, 128 
 Carbon dioxide, 123 
 
 in atmosphere, 73, 128, Ex. 44 
 
 in nature, 128 
 
 in plant life, 126 
 
 preparation of, 124, Ex. 75 
 
 Carbon dioxide (Continued) 
 
 properties of, 125 
 
 test for, 123, Ex. 73 
 Carbon fixation, 126, 303, Ex. 76, 
 
 Ex. 216 
 
 Carbon monoxide, 129 
 Carbon tetrachloride, 408 
 Carbonated water, 125 
 Carbonic acid, 123, Ex. 74 
 Carborundum, 198 
 Casein, 352, Ex. 246 
 Cashmere, 393 
 Cast iron, 221 
 Catalysis, 84 
 Catch crops, 492 
 Celluloid, 277 
 Cellulose, 276 
 Cement, 138, Ex. 80 
 Chalk, 134 
 Charcoal, animal, 113, Ex. 68 
 
 wood, 111, Ex. 68 
 Cheese, 359 
 
 Chemical changes, 57, 103 
 Chemical compounds, 58 
 Chemical tests, 109 
 Chile saltpeter, 161, 529, Ex. 96 
 Chlorine, 146, Ex. 87 
 Chlorophyll, 126 
 Choke damp, 129 
 Citric acid, 259 
 City sewage, 517 
 Clay, 217, Ex. 132 
 Cleaning materials, 404-409 
 Coal, 113 
 Coke, 114, Ex. 69 
 Cold pack method, 387, Ex. 272 
 Collodion, 277 
 Combustion, 62, Ex. 39 
 
 spontaneous, 66 
 Composts, 512 
 Compounds, 56 
 Condensed milk, 359 
 Contact poisons, 412 
 Copper, 230-234 
 
 alloys of, 231 
 
 oxides of, 232 . 
 
 test for, 234 
 
 uses of, 231 
 
 Copper hydroxide, 233, Ex. 147 
 Copper sulphate, 233, Ex. 144, Ex. 
 
 146 
 Copperas, 223 
 
INDEX 
 
 555 
 
 Copper-plating, 231 
 Coral, 134 
 
 Corn plant, analysis of, 295 
 Cotton cloth, 392, Ex. 276 
 mercerized, 392, Ex. 278 
 Covered barnyard, 510 
 Cream, 358 
 Cream of tartar, 258 
 Cream separators, 356 
 Crop rotation, 495-500 . 
 Crude fiber, 294, Ex. 209 
 
 Dairy farming, 543 
 
 Davy's safety lamp, 120, 245 
 
 Deep-tillage machine, 467 
 
 Definite proportions, 57 
 
 Deliquescence, 39 
 
 Denitrification, 181, 434 
 
 Destructive distillation, 112 
 
 Dextrin, 276 
 
 Diamond, 111 
 
 Dietary standards, 341 
 
 Dietary studies, 347 
 
 Diffusion of gases, 74, Ex. 45 
 
 Digestion, 318 
 in intestine, 320 
 in mouth, 318, Ex. 226 
 in stomach, 319, Ex. 227 
 
 Digestion experiments, 328 
 
 Disinfectants, 389 
 
 Distillation, 22 
 
 Double decomposition, 141 
 
 Drainage, 443-449 
 
 Dry farming, 461 
 
 Dry matter in rations, 333 
 
 Drying oils, 265 
 
 Dyeing, 395, Ex. 284 
 
 Dynamite, 254 
 
 Earth mulch, 458, Ex. 336 
 Efflorescence, 39 
 Electrolysis of water, 48, Ex. 29 
 Electrotyping, 231 
 Elements, 56 
 
 essential, 313 
 Enamel paints, 402 
 Energy, available, 328 
 
 net, 329 
 
 Energy materials, 325 
 Energy value of foods, 326 
 Enzymes, 317, 321, Ex. 225 
 Epsom salts, 211 
 
 Equations, 98 
 Essential oils, 267, Ex. 178 
 Esters, 260, Ex. 171 
 Ether extract, 293, Ex. 208 
 Ethereal salts, 260 
 Eudiometer, 54, 55 
 
 Fall plowing, 460 
 Fallows, 463 
 Farrington tablets, 373 
 Fats, 263, 265 
 
 solvents for, 408 
 Fatty acids, 263, Ex. 177 
 Feeding farm animals, 331-339 
 Feeding standards, old, 337 
 Feeds, composition of, 339 
 
 fattening requirements of, 333 
 
 growth requirements of, 332, 339 
 
 maintenance requirements of, 331 
 
 nutritive ratio of, 338 
 
 palatability of, 337 
 
 work requirements of, 332 
 Fermentation, 322 
 Ferrous sulphate, 223 
 Fertilizers, 189, 530, 533-540, 542 
 Fire damp, 245 
 Fixing photographs, 237 
 Flames, 116, Ex. 71 
 
 luminosity of, 117, Ex. 70 
 
 structure of, 118 
 Fly repellents, 414 
 Food adjuncts, 346 
 Food fads, 347 
 Food preservation, by drying, 385 
 
 by heat, 386 
 
 by refrigeration, 385 
 
 chemical, 388, Ex. 274 
 
 cold pack, 387, Ex. 272 
 
 in strong solutions, 386 
 Foods, 341-349 
 
 ash of, 344 
 
 digestibility of, 345 
 
 net energy of, 329 
 
 palatability of, 345 
 
 requirements of, 341 
 
 uses of, 324 
 
 vitamines in, 344 
 Formaldehyde, 254, 417 
 Formation, heat of, 127 
 Formulas, chemical, 97 
 Fructose, 271, Ex. 181 
 Fruit stains, 409 
 
556 
 
 INDEX 
 
 Fruits, food value of, 346 
 Fungicides, 416 
 Fusion, heat of, 27 
 
 Galvanizing, 212 
 
 Gases, are substances, 75, Ex. 46 
 
 diffusion of, 74, Ex. 45 
 
 kindling temperature of, 119, Ex 
 72 
 
 liquefaction of, 75 
 Gasoline, 247 
 
 for cleaning, 408 
 Gelatin, 284, Ex. 203 
 Glaciers, 421 
 Glass, 195 
 
 Glucose, 270, Ex. 184 
 Glutens, 282, Ex. 197 
 Glycerin, 253 
 Grain farming, 543 
 Graphite, 111 
 Green manuring, 490^93 
 Gums, 277, Ex."l93 
 Guncotton, 277 
 Gunpowder, 207 
 
 Harrows, 468 
 Hartshorn, 171 
 Hellebore, 412 
 Human foods, 341-349 
 Hydrated lime, 136, Ex. 80 
 Hydrocarbons, 245 
 Hydrochloric acid, 145, Ex. 86 
 
 test for, 151, Ex. 92 
 Hydrocyanic acid, 208, 414 
 Hydrogen, 45-50 
 
 from water, 41 
 
 occurrence of, 47 
 
 preparation of, 45 
 
 properties of, 46 
 Hydrogen peroxide, 67, 102 
 Hydrogen sulphide, 108, Ex. 64 
 
 test for, 109 
 
 Hydrogenation of oils, 265 
 Hydrosulphuric acid, 108 
 Hypo, 237 
 
 Ice making, 177 
 Iceland spar, 134 
 Illuminating gas, 114, Ex. 69 
 Indelible ink, Ex. 149 
 Indicator, 157, Ex. 94 
 
 Ink stains, 409 
 Inks, 224, 259, Ex. 149 
 Inoculation of soils, 435 
 Insecticides, 411-416 
 
 gaseous, 414 
 
 household, 414 
 Intertillage, 471 
 Invert sugar, 273, Ex. 183 
 Iron, 220-224 
 
 extraction from ores, 220 
 
 rusting of, 222 
 
 sulphides of, 224 
 
 test for, 224 
 
 valence of, 223 
 Irrigation, 449-452 
 
 in humid climates, 452 
 
 methods of, 450 
 
 Japan driers, 400 
 
 Kaolin, 217 
 
 Keeping soil sweet, 473-482 
 Kindling temperature, 63 
 Koumiss, 361 
 
 Lactic acid, 258, Ex. 165 
 Lactometer, 371 
 Lactose, 274 
 Lampblack, 115 
 Lapis lazuli, 219 
 Laughing gas, 168, Ex. 101 
 1/avoisier, 49 
 Lead, 226-229 
 
 occurrence of, 226 
 
 oxides of, 227 
 
 properties of, 226 
 
 sugar of, 108, 228 
 
 tests for, 228 
 
 white, 228 
 
 acetate, 108, 228 
 arsenate, 228, 412 
 ravening agents, 375-382 
 ..egumes in soil building, 424 
 Lime, 135 
 
 air-slaked, 138; Ex. 80 
 
 chloride of, 147 
 
 milk of, 137 
 
 slaked, 136, Ex. 79 
 ime nitrogen, 182, 529 
 -irne sulphur, 412, 416, Ex. 302 
 Limekiln, 136 
 
INDEX 
 
 557 
 
 Limelight, 54, 118 
 Limestone, 134 
 for soils, 473 
 Limewater, 137 
 Liming soils, 477 
 Limiting factors, 437 
 Linen, 393 
 
 Linseed oil, 265, 399, Ex. 287 
 Lipase, 320 
 Litmus paper, 86 
 Litmus test for soils, 475, Ex. 345 
 Luminosity of flames, 117 
 
 Magnesium, 210 
 
 occurrence of, 210 
 
 test for, 211 
 
 Magnesium chloride, 211 
 Magnesium citrate, 259 
 Magnesium oxide, 210 
 Magnesium sulphate, 211 
 Malt, 318 
 Malt sugar, 274 
 Manure shed, 510 
 Marble, 134 
 Market gardening, 545 
 Marl, 134, 479 
 Marsh gas, 244, Ex. 155 
 Matches, 185 
 Mechanical mixture, 58 
 Metals, 158, 240 
 
 recognition of, 242 
 Methane, 244, Ex. 155 
 Milk, bacteria in, 353 
 
 composition of, 350 
 
 condensed, 359 
 
 evaporated, 359 
 
 powder, 359 
 
 testing of, 364 
 Milk and products, 350-361 
 Mineral matter in plants, 312 
 Mineral waters, 38 
 Miner's safety lamp, 120 
 Mixed farming, 544 
 Mixed fertilizers, 533-540 
 
 buying, 534 
 
 field experiments, 536 
 
 home-mixing, 533 
 Mohair, 393 
 Molecules, 92 
 Mordants, 395, Ex. 284 
 Morphine, 286 
 Mortar, 137 
 
 Multiple proportions, 87 
 Muriate of potash, 526 
 
 Naphtha, 247 
 Negative, 237, Ex. 151 
 Net energy of foods, 329 
 Neutralization, 155, Ex. 93 
 Nicotine, 286 
 Niter, 206 
 Nitrates, 165, Ex. 99 
 
 test for, 166 
 Nitric acid, 162, 164 
 
 test for, 166 
 
 uses of, 165 
 Nitrification, 181 
 Nitrites, 166, Ex. 100 
 Nitrocellulose, 277 
 Nitrogen, 70 
 
 fixation of, 182, 435 
 
 in air, 70 
 
 in fertilizers, 527 
 
 in plants, 314 
 
 occurrence of, 71 
 
 oxides of, 167, Ex. 101, 102 
 
 properties of, 70 
 Nitrogen cycle, 179 
 Nitrogen-free extract, 295 
 Nitroglycerin, 253 
 Nitro-lime, 182, 529 
 Nitrous acid, 166 
 Non-metals, 158, 201 
 Nutrition, principles of, 324-330 
 Nutritive ratio, 338 
 
 Oils, 263 
 
 essential, 267 / 
 Oleic acid, 264 
 Oleomargarine, 264 
 Orcharding, 546 
 Organic acids, 256-261 
 Organic 'chemistry, 131, 244 
 Organic matter in soils, 423, 485 
 
 functions of, 486-488 
 
 loss of, 488 
 
 restoring, 489 
 
 Organic nitrogen compounds, 280-286 
 Organic salts, 260 
 Osmosis, 310, 312, Ex. 220 
 Oxalic acid, 258 
 Oxides and oxidation, 61 
 Oxygen, 49, 52-68 
 
 occurrence of, 67 
 
558 
 
 INDEX 
 
 Oxygen (Continued) 
 
 preparation of, 48, 52, Ex. 30 
 properties of, 53, Ex. 31, Ex. 32 
 proportion in air, 67, Ex. 41 
 
 Oxy-hydrogen blowpipe, 54 
 
 Paints, 399-402 
 
 Palmitic acid, 264 
 
 Paris green, 233, 412 
 
 Pasteurizing, 354 
 
 Pectins, 277, Ex. 193 
 
 Pepsin, 320 
 
 Peptones, 283, Ex. 201 
 
 Permanent pastures, 547 
 
 Persian insect powder, 413 
 
 Petroleum, 246 
 
 Phosphate, acid, 190, 523, Ex. 113 
 
 bone, 521 
 
 mineral, 522 
 
 rock, 188, 522 
 
 Thomas, 222 
 
 with manure, 524 
 Phosphorescence, 184 
 Phosphoric acid, 186, 190, Ex. 112 
 
 salts of, 187 
 
 test for, 190 
 Phosphorus, 184 
 
 m fertilizers, 520 
 
 occurrence of, 188 
 
 preparation of, 185 
 
 red, 185 
 
 Physical changes, 57, 103 
 Pigments, 400 
 Plant growth, 298-307 
 Plants, composition of, 289 
 
 parasitic, 307 
 
 Plaster of Paris, 139, Ex. 82 
 Plows, 464 
 Porcelain, 217 
 Positive, 237, Ex. 151 
 Potash, 206, Ex. 124 
 
 muriate of, 526 
 Potassium, 204-208 
 
 in fertilizers, 525 
 
 occurrence of, 204 
 
 test for, 208 
 Potassium carbonate, 206, Ex. 
 
 124 
 
 Potassium chlorate, 208, Ex. 126 
 Potassium chloride, 205 
 Potassium cyanide, 208 
 Potassium hydroxide, 205, Ex. 123 
 
 Potassium nitrate, 206 
 Potassium sulphate, 206, 526 
 Potato scab, 417, Ex. 305 
 Pottery, 217 
 Priestley, 49 
 Proteins, 280, Ex. 194 
 
 albumins, 283, Ex. 198 
 
 importance of, 284 
 
 in human diet, 343 
 
 insoluble, 282, Ex. 197 
 
 manufacture of, 306 
 
 peptones, 283, Ex. 201 
 
 repair material, 324 
 
 tests for, 281, Ex. 196 
 Ptomaines, 286 
 Ptyalin, 319 
 Pyrethrum powder, 413 
 
 Quartz, 193 
 Quinine, 286 
 
 Rations, calculating, 334 
 
 Reactions, 98 
 
 Reagents, 98 
 
 Reducing agent, 115 
 
 Reduction, 67, Ex. 40 
 
 Refrigeration, 385 
 
 Rennin, 320 
 
 Repair material, 324 
 
 Respiration of plants, 305, Ex. 214 
 
 Rollers, 470 
 
 Roots, bulbs, and tubers, 301 
 
 Roots dissolve mineral matter, 314, 
 
 Ex. 223 
 Rotation of crops, 495-500 
 
 Sal soda,' 150 
 
 Salicylic acid, 259 
 
 Salt, 144, 145, Ex. 85, Ex. 86 
 
 Saltpeter, 161, 206, 529, Ex. 96 
 
 Salts, 155, 156, 157 
 
 Sand, 193, Ex. 115 
 
 Saponification, 267 
 
 Scheele, 49 
 
 Scouring soaps, 407, Ex. 296 
 
 Seeds, germination of, 298, Ex. 211, 
 
 Ex. 213 
 
 Sheep dips, 414 
 Shells, 134 
 Short fallows, 464 
 Shortening, 381, Ex. 269 
 Silica, 193 
 
INDEX 
 
 559 
 
 Silicates, decomposing, 197 
 
 natural, 196, Ex. 118 
 
 test for, 197 
 
 Silicic acid, 195, Ex. 116 
 Silicon, 194 
 Silk, 394 
 Silver, 235-238, Ex. 148 
 
 test for, 238, Ex. 153 
 Silver chloride, 236 
 Silver nitrate, 236 
 Silver sulphide, 235 
 Silver-plating, 236 
 Skim milk, 355 
 
 Slaked lime, 136, Ex. 79, Ex. 80 
 Slow oxidation, 64, Ex. 38 
 Soap powders, 407 
 Soaps, 266, 404-406, 407 
 Soda water, 125 
 Sodium, 145, 148-151, Ex. 89 
 
 test for, 151 
 
 Sodium benzoate, 260, Ex. 170 
 Sodium bicarbonate, 150, Ex. 91 
 Sodium borate, 1S8, Ex. 119 
 Sodium carbonate, 150, Ex. 91 
 Sodium fluoride, 415 
 Sodium hydroxide, 149, Ex. 90 
 Sodium sulphate, 149 
 Sodium sulphite, 150 
 Soils, 420-500 
 
 acidity of, 473-478 
 
 animal life in, 424 
 
 chemical analysis of, 437 
 
 classification of, 427 
 
 formation of, 420-425 
 
 inoculation of, 435 
 
 keeping sweet, 473-482 
 
 liming of, 477 
 
 limiting factors in, 437 
 
 litmus test of, 475 
 
 mineral elements in, 436 
 
 physical make-up of, 426 
 
 Truog test of, 476, Ex. 346 
 
 water in, 440-452 
 Specific heat, 29 
 Spontaneous combustion, 66 
 Spots and stains, 409 
 Spring plowing, 459 
 Stable manure, 501-517 
 
 applying, 513 
 
 composition of, 502 
 
 composting of, 512 
 
 factors affecting value of, 503 
 
 Stable manure (Continued) 
 
 importance of, 501 
 
 leaching of, 508 
 
 liquid, value of, 506 
 
 losses in, 505 
 
 phosphates with, 524 
 
 preservatives with, 507 
 
 results with, 516 
 
 sheds for, 510 
 
 valuation of, 501 
 Starch, 274, Ex. 186 
 Steapsin, 320 
 Stearic acid, 264 
 Steel, 222 
 Stereotyping, 232 
 Stomachic poisons, 412 
 Strychnine, 286 
 Sublimation, 176, Ex. 107 
 Sugar, cane, 272, Ex. 184 
 
 fruit, 271, Ex. 181 
 
 grape, 270, Ex. 184 
 
 invert, 273, Ex. 183 
 
 malt, 274 
 
 milk, 274 
 
 Sugar of lead, 108, 228 
 Sulphides, 81, Ex. 51 
 Sulphur, 78-88 
 
 occurrence of, 81 
 
 preparation of, 79 
 
 properties of, 79 
 
 two acids of, 106, Ex. 63 
 Sulphur dioxide, 82, Ex. 52 
 Sulphur trioxide, 83, Ex. 53 
 Sulphureted hydrogen, 108 
 Sulphuric acid, 85, 105, 107, Ex. 
 54, Ex. 55 
 
 test for, 109 
 Sulphurous acid, 104, Ex. 61 
 
 test for, 109 
 Summer fallows, 463 
 Superphosphate, 523 
 Symbols, 94 
 Synthesis, 56 
 
 Tannic acid, 259, Ex. 169 
 Tartaric acid, 258 
 Textiles, 392-395 
 Thomas phosphate, 222 
 Tillage, 455-471 
 
 aerates soil, 456 
 
 conserves moisture, 457, Ex. 336 
 
 destroys weeds, 460 
 
560 
 
 INDEX 
 
 Tillage (Continued") 
 
 harrowing s 468 
 
 increases feeding ground, 455 
 
 increases water, 456 
 
 plowing, 464 
 
 rolling, 470 
 
 Tobacco insecticides, 413 
 Truog test, 476, Ex. 346 
 Trypsin, 320 
 Types of farming, 542-547 
 
 all crops sold, 542 
 
 dairying, 543 
 
 fat stock, 544 
 
 grain, 543 
 
 market gardening, 545 
 ' mixed, 544 
 
 orcharding, 546 
 
 special crops, 545 
 
 Ultramarine, 218 
 Urea in manure, 507 
 
 Valence, 102 
 
 Vaporization, heat of, 27 
 Varnishes, 402 
 
 black, 403 
 
 Vehicles for paints, 399, Ex. 287 
 Vinegar, 256 
 
 quick process, 257 
 Vitamines, 344 
 
 Washing soda, 150, 407, Ex. 91 
 Water, 21-44 
 
 accelerates chemical action, 35, 
 Ex. 16 
 
 amount used by plants, 309 
 
 boiled for drinking, 36 
 
 boiling point changed, 35, Ex. 15 
 
 composition of, 54 
 
 contamination of, 36, Ex. 17 
 
 decomposition of, 40, Ex. 22 
 
 distillation of, 22, Ex. 2 
 
 effect of pressure on, 25, Ex. 6, 
 Ex. 7 
 
 electrolysis of, 48, Ex. 29 
 
 freezing of, 24, Ex. 5 
 
 functions of, in plant, 311, Ex. 221 
 
 hard, 37, 140, 405, Ex. 18, Ex. 83, 
 Ex. 84 
 
 heat of fusion, 27, Ex. 9 
 
 Water (Continued') 
 
 heat of vaporization, 27, Ex. 10 
 
 hydrogen from, 41, Ex. 22 
 
 importance to plants, 309, Ex. 219 
 
 in organic matter, 38, Ex. 19 
 
 maximum density of, 24 
 
 mineral, 38 
 
 mineral matter in, 22, Ex. 1 
 
 never pure in nature, 21 
 
 of crystallization, 39, Ex. 20 
 
 poor conductor, 28, Ex. 11 
 
 potable, 35, Ex. 17 
 
 properties of, 23, Ex. 3 
 
 rain, 22, Ex. 1 
 
 solvent action of, 34, Ex. 12, Ex. 13, 
 Ex. 14 
 
 three states of, 24 
 
 used to establish standards, 25 
 
 vapor in air, 72, Ex. 43 
 Water gas, 130 
 Water glass, 194, Ex. 117 
 Water paints, 401 
 Water table, 440 
 Water-soluble vitamines, 343 
 Weathering of rocks, 420, 423, Ex. 
 
 307 
 
 Weeds destroyed by tillage, 460 
 Welding, 222 
 Welsbach burner, 118 
 Whale oil soap, 413 
 What to eat, 348 
 White lead, 228, 400 
 White wine vinegar, 257 
 Whitewash, 137, 401 
 Wind action, 422 
 Wintergreen, oil of, 260, Ex. 172 
 Wood ashes, 206, 527 
 Wool, 393, Ex. 280, Ex. 282 
 
 test for, 394 
 
 Work, food requirements for, 332 
 Wrought iron, 221 
 
 Yeast, in bread making, 376, Ex. 263 
 
 Zinc, 211-213 
 
 metallurgy of, 212 
 
 preparation of, 211 
 
 properties of, 212 
 
 tests for, 213 
 Zinc oxide, 212, 400 
 
HDYYUOY 
 
 Alfrled 
 
 Everyday chemistry 
 
 Educ. 
 
 LID. 
 
 UNIVERSITY OF CALIFORNIA LIBRARY 
 
YB 36027 
 
 INTERNATIONAL ATOMIC WEIGHTS (1914) 
 O-16 
 
 Aluminum . . . . Al 
 
 Antimony Sb 
 
 Argon A 
 
 Arsenic As 
 
 Barium Ba 
 
 Beryllium .... Be 
 
 Bismuth Bi 
 
 Boron B 
 
 Bromine Br 
 
 Cadmium Cd 
 
 Casium Ca 
 
 Calcium Ca 
 
 Carbon C 
 
 Cerium Ca 
 
 Chlorine Cl 
 
 Chromium . . . . Cr 
 
 Cobalt ; Co 
 
 Columbium . . , Ob 
 Copper. ... 
 Dysprosium . . 
 Erbium . . . 
 Europium . . . 
 Fluorine ... 
 
 Gadolinium .... Ud 
 
 Gallium ..... Ga 
 
 Germanium . ... Go 
 
 Gold 
 
 Helium -' 
 
 Holmium 
 
 Hydrogen BL 
 
 Indium In 
 
 Iodine I 
 
 Indium IT 
 
 Iron Fe 
 
 Krypton Kr 
 
 Lanthanum .... La 
 
 Lead Pb 
 
 Lithium ..... Li 
 
 Lutecium Lu 
 
 Magnesium .... Mg 
 
 Manganese .... Mn 
 
 Mercury Hg 
 
 27.1 Molybdenum .... Mo 96.0 
 
 120.2 Neodymium .... Nd 144.3 
 
 39.88 Neon Ne 20.2 
 
 74.96 Nickel Ni 58.68 
 
 137.37 Niton (radium emanation) Nt 222.4 
 
 9.1 Nitrogen N 14.01 
 
 208.0 Osmium Os 190.9 
 
 11.0 Oxygen O 16.00 
 
 79.92 Palladium Pd 106.7 
 
 112.40 Phosphorus . . . . P 31.04 
 
 132.81 Platinum Pt 195.2 
 
 40.07 Potassium K 39.10 
 
 12.00 Praseodymium . . . Pr 140.6 
 
 140.25 Radium Ra 226.4 
 
 35.40 Rhodium Rh 102.9 
 
 62.0 Rubidium Rb 85.45 
 
 iuthenium . . . . Ru 101.7 
 
 marium Sa 150.4 
 
 <**iri Sc 44.1 
 
 So 79.2 
 
 37.7 3i 28.3 
 
 52.0 . . . . Ag 107.88 
 
 19.0 S . . . . Na 23.00 
 
 157.3 St . . . . Sr 87.63 
 69.9 . . . . S 32.07 
 72.5 j. Ta 181.5 
 
 197.2 n Te 127.5 
 
 m Tb 159.2 
 
 im Tl 204.0 
 
 am Th 232.4 
 
 114.6 urn Tm 168.5 
 
 126.92 Tin Sn 119.0 
 
 193.1 Titanium Ti 48.1 
 
 65.84 Tungsten W 184.0 
 
 82.92 Uranium U 238.5 
 
 139.0 Vanadium V 61.0 
 
 207.10 Xenon Xe 130.2 
 
 6.94 Ytterbium (Neoytter- 
 
 174.0 bium) Yb 172.0 
 
 24.32 Yttrium Yt 89.0 
 
 54.93 Zinc Zn 65.37 
 
 200.6 Zirconium Zr 90.6