LEME . i rtirniu<' (HEMISTRY E PER Cdl/R SE BohooT Of LIBRARY OF THE UNIVERSITY OF CALIFORNIA. OIKT OK l -C -Heath &CO-. 331 Sansome S't. S.F. Cal. Received Accession No. . Class No. BRIEFER COURSE. ELEMENTS OF CHEMISTRY, DESCRIPTIVE AND QUALITATIVE. BY JAMES H. SHEPARD, ii PROFESSOR OF CHEMISTRY, SOUTH DAKOTA AGRICULTURAL COLLEGE, AND CHEMIST TO THE UNITED STATES EXPERIMENT STATION, SOUTH DAKOTA. W7B11SIT7 BOSTON, U.S.A.: D. C. HEATH & CO., PUBLISHERS. 1895. Entered according to Act of Congress, in the year 1890, by JAMES H. SHEPARD, in the Office of the Librarian of Congress, at Washington. TYPOGRAPHY BY J. S. GUSHING & Co., BOSTON, U.S.A. PKESSWOBK BY BERWICK & SMITH, BOSTON, U.S.A. PREFACE. THIS briefer course follows, in general, the plan of SheparcTs Elements of Chemistry ; but the reader will notice that the student is told, to a still less extent than in the larger book, what he may expect to see while working. Directions for preparing reagents, and equipping the laboratory, and discussions of methods of presentation are not given here, since these matters are fully treated in the larger book, which is now so generally used that it is readily accessible to all. The subject-matter of this text is so arranged, and the experiments are so simplified, that the laboratory work will come within the time available in those schools where but part of the year is allotted to the study of chemistry. The text will also be found accept- able in many schools where a special or a technical course is offered. Data for chemical computations given at the begin- ning of the chapters, numerous exercises for review or advanced course, a close adherence to inductive methods, and, wherever possible, careful experimental illustrations iii iv PREFACE. of all important facts not readily understood by analogy, are features of this briefer course which will, it is hoped, commend themselves to the many truly scientific educa- tors of the youth in all parts of our land. In the chapters devoted to the carbon compounds, owing to the unsatisfactory results usually to be had at the hands of beginners working with organic substances, it seemed best to limit the work to the preparation and discussion of the more important compounds and at the same time dwelling upon the general laws governing the origin of the derivatives belonging to the different series. The author takes pleasure in acknowledging the valu- able assistance rendered during the preparation of this work by Mr. H. Ellsworth Call, of the Des Moines, la., High School ; Miss Ada J. Todd, of the Bridgeport, Conn., High School ; Mr. H. N. Chute, of the Ann Arbor, Mich., High School ; Prof. I. P. Bishop, State Normal and Train- ing School, Buffalo, N. Y. ; Mr. J. T. Draper, Pueblo High School, Col. ; and by many other prominent educators in all parts of the country. J. H. S. BROOKINGS, March 30, 1891. co INTRODUCTION. PAGE ORIGIN OP CHEMISTRY. Experimentation. Solution. Evapo- ration. Precipitation. Filtration. Decantation. Reduction. Elements. Table of the Elements. Atoms. Symbols. Compounds. Law of Definite Proportions. Dalton's Atomic Theory. Atomic Weights. Molecules. Molecular Formulae. Chemism or Chemical Affinity. Exercises 1-11 CHAPTER I. OXYGEN. Data for Computations. Occurrence. Preparation and Properties. Crystallization. Ozone. Tests for Oxygen and Ozone. Exercises 12-18 CHAPTER H. HYDROGEN. Data for Computations. Occurrence. Preparation and Properties. Water. Occurrence. Preparation and Prop- erties. Analysis and Synthesis of Water. Solvent Action of ' Water. Heat Capacity of Water. Exercises 19-28 CHAPTER m. NITROGEN. Data for Computations. Occurrence. Preparation and Properties. Ammonia. Occurrence. Preparation and Properties. Tests for Ammonia. Oxides of Nitrogen. Nitro- gen Monoxide : its occurrence, properties, and tests. Washing of Gases. Determination of Molecular Weights. Law of Multiple Proportions. Avogadro's Hypothesis. The Nitrogen Oxacids. Nitric Acid. Occurrence, etc. Oxidizing Re- agents. Exercises 29-42 V VI CONTENTS. CHAPTER IV. PAGE THE HALOGENS: Data for Computations. CHLORINE. Occur- rence, etc. Hydrochloric Acid. Occurrence, etc. A Group Reagent. Oxides of Chlorine. The Chlorine Oxacids. BROMINE. Occurrence, etc. The Bromine Acids. IODINE. Occurrence, etc. The Iodine Acids. FLUORINE. Occur- rence, etc. Hydrofluoric Acid. Exercises 43-56 CHAPTER V. BINARY COMPOUNDS. Higher Compounds. Acids. Bases. Salts. Normal, Acid, and Basic Salts. Valence. Substi- tuting Power and Valence. Determination of Atomic Weights by Avogadro's Hypothesis. Exercises 57-64 CHAPTER VI. CARBON. Data for Computations. Occurrence, etc. Stone Coal. Charcoal. Graphite. Diamonds. Lignite. Car- bon and Hydrogen. Methane. Ethylene. Acetylene. Carbon and Oxygen. Carbon Monoxide. Carbon Dioxide. Occurrence, Properties, etc. Exercises 65-78 CHAPTER VII. SULPHUR, SELENIUM, AND TELLURIUM. Data for Computations. SULPHUR. Occurrence, etc. Hydrogen Sulphide . its occur- rence, etc. Oxides of Sulphur. The Sulphur Oxacids. Sul- phurous Acid : its occurrence, etc. Sulphuric Acid : its occur- rence, etc. Nordhausen or Fuming Sulphuric Acid. Test for Thiosulphates. Carbon Disulphide. SELENIUM and TELLU- RIUM. Exercises 79-91 CHAPTER VIII. SILICON: its occurrence, etc. Tests for the Silicates. BORON: its occurrence, etc. Tests for Boric Acid and its Compounds. PHOSPHORUS: its occurrence, eta 3 3 hosDhorus and Hydro- gen. The Pliospnorus uxacias. rnospnonc ACIQ, ana its Tests, Exercises . . 92-99 CONTENTS. Vll CHAPTER IX. PAGE INTRODUCTORY TO THE METALS. Properties of the Metals. Alloys. Classification of the Metals. The First Group Metals. The Second Group Metals. The Third Group Metals. The Fourth Group Metals. The Fifth Group Metals . . 100-103 CHAPTER X. THE FIRST GROUP METALS. Data for Computations. LEAD. Occurrence and Preparation. Properties and Compounds. Tests for Lead. SILVER. Occurrence and Preparation. Prop- erties and Compounds. Tests for Silver. MERCURY. Oc- currence, etc. Separation and Identification of Lead, Silver, and Mercury. Exercises 104-113 CHAPTER XI. THE SECOND GROUP METALS. Data for Computations. ARSENIC. Occurrence and Preparation. Properties and Compounds. Tests for Arsenic. ANTIMONY. Occurrence and Preparation. Properties and Compounds. Tests for Antimony. TIN. Occurrence, etc. BISMUTH. Occurrence, etc. COPPER. Occurrence, etc. CADMIUM. Occurrence, etc. Analysis of the Second Group Metals. Exercises 114-130 CHAPTER XH. THE THIRD GROUP METALS. Data for Computations. IRON. Occurrence and Preparation. Steel. Properties and Com- pounds of Iron. Tests for Iron. Tests for Ferro- and Ferri- Cyanic Acids. CHROMIUM. Occurrence, etc. ALUMINIUM. Occurrence, etc. NICKEL. Occurrence, etc. COBALT. Occurrence, etc. MANGANESE. Occurrence, etc. ZINC. Occurrence, etc. Analysis of the Third Group Metals. Exer- cises 131-147 CHAPTER Xni. THE FOURTH GROUP METALS. Data for Computations. BARIUM. Occurrence and Preparation. Properties and Compounds. Tests. STRONTIUM. Occurrence, etc. CALCIUM. Occur- rence, etc. MAGNESIUM. Occurrence, etc. Analysis of the Fourth Group Metals. Exercises 148-155 yiii CONTENTS. CHAPTER XIV. PAGE THE FIFTH GROUP METALS. Data for Computations. POTASSIUM. Occurrence and Preparations. Properties and Compounds. Test. SODIUM. Occurrence, etc. AMMONIUM. ANALYSIS OF AN UNKNOWN SUBSTANCE. Solution. Detection of Bases. Detection of Acids 156-167 CHAPTER XV. INTRODUCTORY TO THE CARBON COMPOUNDS. Organic and Inor- ganic Substances. Homology. Table of the Hydrocarbon Series. Names of the Members of the Hydrocarbon Series. Elementals and Derivatives. Substitution. Addition Prod- ucts. Unsaturated Radicals of the Paraffin Series. Isomerism. Uniformity among Derivatives 168-175 CHAPTER XVI. THE PARAFFIN SERIES, C n H 2n+2 . Occurrence and Preparation. Properties. METHANE AND ITS DERIVATIVES. I. HALOGEN DERIVATIVES. Chlor-Methane, or Methyl Chloride. Trichor- Methane, or Chloroform. Tri-iodo-Methane, or lodoform. OXYGEN DERIVATIVES. Methyl Alcohol, or Wood Alcohol. Methyl Ether. Methyl Aldehyde, or Formic Aldehyde. For- mic Acid. NITROGEN DERIVATIVES. The Methylamines. Cyanogen and Hydrocyanic Acid. Nitro-Methane. DERIVA- TIVES WITH SULPHUR, ARSENIC, PHOSPHORUS, etc. The Mercap- tans, Phosphines, Arsines, and Stibines. METALLIC DERIVA- TIVES. ETHANE AND ITS DERIVATIVES. OXYGEN DERIVATIVES. -Ethyl Alcohol. Ethyl Ether. Ethyl Aldehyde. Acetic Acid, Soap, Ethyl Nitrate 176-200 CHAPTER XVII. THE. OLEFINE DERIVATIVES. Ethylene. Lactic Acid. Oxalic Acid. Succinic Salt. Malic Acid. Tartaric Acid. Citric Acid. Glycerine, Glycerol, or Propenyl Alcohol. Oleic Acid. ACETYLENE DERIVATIVES. Linoleic Acid. Mannite, or Manitol . . 201-207 CONTENTS. IX CHAPTER XVIII. PACK THE CARBOHYDRATES. THE SUCROSES. Milk Sugar, Lactose. THE GLUCOSES. Grape Sugar, Dextrose, or Glucose. THE AMYLOSES. Starch, or Amylum. The Gums. Cellulose. Gun-Cotton. The Glucosides 208-217 CHAPTER XIX. THE TERPENES. THE BENZENES. Benzene. Phenol, Phenyl Alcohol, or Carbolic Acid. Resorcin, and Pyragallol. Nitro- benzene. Aniline, Amidobenzeiie, or Phenylamine. The Tol- uenes. THE STYRENES, OR CINNAMINES. THE NAPHTHALENES. THE ANTHRACENES 218-227 CHAPTER XX. THE ALKALOIDS AND THE ALBUMINOIDS . . 228-230 TH* TJHI7BRSIT7 INTRODUCTION 1. Origin of Chemistry. The rudiments of the science of Chemistry may be traced back to the ancient Egyptians. About 640 A.D. the Arabs invaded Egypt, where they obtained a knowledge of the sciences practised there. Dur- ing the Middle Ages they preserved this knowledge, and from their academies in Spain as centres, it gradually spread over all parts of the civilized world. Up to this time the main inducement for studying and practising chemistry was a hope of discovering the Philosopher's Stone, a stone that should change the baser metals into gold. During these researches many important facts in inorganic chem- istry were discovered. From the fifteenth to the seventeenth century the Elixir Vitce, or Elixir of Life, a cordial that should cure all the ills of mankind and give perpetual youth, was the chief object sought. In this search many valuable medicines were discovered. During the seventeenth century the properties of gases were investigated, and in both this and the succeeding century other important advances were made. Notwithstanding all previous advancement, however, the modern science of Chemistry is emphatically a product of the present century. 2. Experimentation. The greatest hindrance to chemical progress in the past lay in the fact that the science of ex- 1 INTRODUCTION. perimenting was not well understood. Erroneous theories were advanced and believed in for centuries. These theo- ries were finally overthrown by the rigid test of experiment, and thus progress and improvement were made possible. When we experiment with a substance, we so treat it that we may ascertain its properties and behavior. In experimenting with substances, the chemist finds fre- quent .use for such processes as Solution, Evaporation, Precipitation, Filtration, Decantation, Reduction, Distilla- tion, and Electrolysis. Excepting the two latter, which will be explained hereafter, these processes may be illus- trated by experiments. 3. Solution, EXPERIMENT 1. Place about a gram of com- mon salt (Nad) in a test-tube, and then fill the test-tube half full of water. Now gently heat the tube in the Bunsen flame (Fig. 1) ; frequently cover the mouth of the tube with the thumb and shake. EXERCISE. What becomes of the salt ? Define the process called " solution." What is a solu- tion ? Define solids ; liquids ; gases. 4. Evaporation, EXP. 2. Place a few drops of the salt solution obtained in Exp. 1 on a piece of tin or in an iron spoon. Now warm gently till the water has disap- peared. FIG- 1. Ex. What became of the water ? What remains on the tin ? Define evaporation. What is the object of evaporation ? 5. Precipitation. EXP. 3. To about one-half of the salt solution (Exp. 1) add nearly an equal volume of a solution of silver nitrate (AgNO 3 ). INTRODUCTION. 3 FIG. 2. Ex. What takes place ? (The silver of the silver nitrate has united with the chlorine of the common salt to form the solid silver chloride, AgCl, thus removing the chlorine from the salt solution, or the silver from the silver nitrate solution.) What is the object of precipitation ? Why would not evaporation do instead ? Define precipitation ; precip- itate. 6. Filtration. EXP. 4. Support a funnel on a ring-stand, and place a beaker underneath the funnel ; fold a round filter-paper twice "(Fig. 2), making the folds at right angles to each other ; place the point of the paper in the funnel, and open one of the pockets formed by folding the paper : into this pocket pour the contents of the tube used in Exp. 3. Ex. What occurs ? What is the object of nitration ? Would evapo- ration have answered as well ? Try it. Define filtration ; filtrate. How can you wash the precipitate while it is on the filter-paper ? 7. Decantation. EXP. 5. Precipitate the remainder of the salt solution (Exp. 1) with silver nitrate ; warm gently, and allow the tube to stand for a few minutes. Now pour off the solution, leaving the solid precipitate in the tube. Ex. What have you ' accomplished ? Define decantation. How can you wash a precipitate by decantation ? Compare decantation with filtration. 8. Reduction. EXP. 6. Into a piece of charcoal bore a hole with the point of a penknife, and in this hole place the precipitate obtained in Exps. 4 or 5. Now heat this precipitate in the blow-pipe flame (Fig. 3). Ex. What is the bead you thus obtain ? What became of the chlo- rein? What does * * reduction ' ' mean ? FIG. 3. 4 INTRODUCTION. 9. Elements, In the last experiment silver was obtained from a substance that did not at all resemble silver. In fact, silver was reduced from its chlorine compound. Chem- ists have found, however, that neither the silver nor the chlorine can be further divided; hence these substances are called elements. DEFINITION. A chemical element is a substance that cannot be divided, or at least has not been divided, into simpler substances. At the present time about seventy different elements are known. Of course it has not been possible to examine every portion of the earth's crust for elements, but such elements as are now discovered from time to time occur only in very small quantities. Again, it is possible that some substances now known to us as elements may prove to be compounds as our appli- ances for chemical investigation are improved. The following table gives a list of the elements. The first column contains the names of the elements ; the signi- fication of the other columns will be explained further on. INTRODUCTION. 10, A Table of the Elements. Names. Symbols. Atomic Weights. Physical condition at ordinary temperature. Specific Gravity. Aluminum Al"" 27. Solid 2.60 Antimony Sb'"- v 120. u 6.71 Arsenic As'"- v 75. 5.73 Barium Ba" 137. (C 3.75 Beryllium Be" 9. ( 2.07 Bismuth Bi'".v 208. 11 9.80 Boron B'" 11. n 2.5? Bromine Br'' v 80. Liquid 3.187 Cadmium Cd" 112. Solid 8.60 Caesium Cs' 133. K 1.88 Calcium Ca" 40. u 1.57 Carbon C"" 12. <( 3.5-.6 Cerium Ce'"'"" 141. 6.68 Chlorine Cl'- v 35.5 Gas 2.450 Chromium Cr""- vi 52. Solid 6.50 Cobalt Co"-"" 59. ti 8.5-.7 Copper Cu" 63.3 it 8.95 Didymium D" f 142.3 a 6.54 Erbium E'" 166. u Fluorine F' 19. Gas 1.313 Gallium G"" 69. Solid 5.95 Gold Au''"' 196.5 a 19.32 Hydrogen H' 1. Gas 0.069 Indium In"" 113.6 Solid 7.42 Iodine I'- v 127. 4.948 Iridium j r M, nn,\i 193. n 22.42 Iron F e ","",vi 56. (C 7.86 Lanthanum La"' 138.2 (( 6.10 Lead Pb"' "" 207. (( 11.37 Lithium Li' 7. (( 0.59 Magnesium Mg".'"'. 24. tc 1.74 Manganese Mn" 55. (( 8.03 Mercury Hg" 200. Liquid 13.55 Molybdenum Mo"- ""' vi 96. Solid 8.60 Nickel Ni","" 58. K 8.90 a r s *V INTRODUCTIONS Names. Symbols. Atomic Weights. Physical condition at ordinary temperature. Specific Gravity. Niobium Nb v 94. Solid 7.06 Nitrogen N 'ff,v 14. Gas 0.971 Osmium Os".""' vi 199. Solid 22.48 Oxygen O" 16. Gas 1.105 Palladium Pd"'"" 106. Solid 11.40 Phosphorus -pi, til, v 31. -" ! Colorless 1.83 Red 2.20 Platinum Pt rr, nn 195. (C 21.50 Potassium K' 39. ti 0.87 Rhodium Ro"'""' vi 104. 12.10 Rubidium Rb' 85. u 1.52 Ruthenium R u fU"f,Ti 103.5 (( 12.26 Samarium Sm 150. It Scandium Sc 44. It Selenium Se"-"" vi 79. u 4.50 Silicon Si"" 28. (( 2.39 Silver Ag' 108. u 10.53 Sodium Na' 23. 1 1 0.978 Strontium Sr" 87.5 u 2.54 Sulphur $n,ttn,vi 32. (( 2.05 Tantalum Ta v 182. u 10.40 Tellurium Te"'"" >vi 125.? C (, 6.40 Terbium Tb 148.5? l.t Thallium Xl'-'" 204, tl 11.85 Thorium Th"" 232. it 11.00 Tin Sn""" 118. It 7.29 Titanium T^"' "" 48. (( Tungsten W/f,vi 184. (( 19.12 Uranium U'" f vi 239.8 ( i 18.70 Vanadium V'/' v 51.5 u 5.50 Ytterbium Yb 173. u Yttrium Y"' 89. u Zinc Zn" 65. u 7.15 Zirconium Zr"" 90. l 4.15 INTRODUCTION. 11. Atoms. It is the prevailing belief that matter is made up of extremely minute, indivisible particles called atoms. Many reasons lead to the conclusion that all the atoms of the same element are alike, but that they are unlike the atoms of any other element. 12. Symbols. It is often convenient to represent the name of an element by some letter or letters, as H for hydrogen, O for oxygen, Cd for cadmium, etc. In the second column of the table (Art. 10) are given the symbols commonly employed. These symbols are also used for other purposes, thus : H also stands for an atom of hydrogen, O for an atom of oxygen, etc. When we wish to represent more than one atom, figures are used, thus : 2 H means two atoms of hydrogen ; 3 H, three atoms ; etc. Subscript figures are used for the same pur- pose when more than one symbol is needed to represent certain substances; thus: H 2 O, water; NH 3 , ammonia; C 2 H 4 , ethylene ; etc. Some elements have symbols derived from their Latin names. This is perplexing to the student, but this list will explain : Antimony, Sb, from Stibium. Copper, Cu, " Cuprum. Gold, Au, u Aurum. Iron, Fe, " Ferrum. Lead, Pb, " Plumbum. Mercury, Hg, " Hydrargyrum. Potassium, K, from Kalium. Silver, Ag, " Argentum. Sodium, Na, " Natrium. Tin, Sn, " Stannum. Tungsten, W, " Wolframium. NOTE. At the right of the symbols in the table the indices and numer- als are used to indicate the valence (Art. 76) of the elements. The symbols are commonly written without these. 13. Compounds. EXP. 7. Mix thoroughly 0.56* very fine jron filings and 0.32 s flowers of sulphur. Place this mixture 8 INTRODUCTION. in an iron spoon, and heat it to redness in the Bunsen flame. The iron and sulphur combine, forming the chemical compound, ferrous sulphide (FeS). Ex. Define a chemical compound. Compare the ferrous sulphide with the iron and sulphur of which it is composed. 14, Law of Definite Proportions, When elements unite, as in the case of iron and sulphur, it has been proven that they always unite in fixed and definite proportions. For example : 56 parts, by weight, of iron always unite with 32 parts of sulphur, to form ferrous sulphide (FeS). Again : 23 parts of sodium always unite with 35.5 parts of chlorine to form common salt (NaCl), etc. The law may be stated in this form : Any given chemical compound always contains the same elements in the same proportions by weight. 15, Atomic Theory, To account for the union of ele- ments in definite proportions by weight, the supposition has been made that the atoms of the elements are the units between which the union takes place. The simplest case is where one atom of one element unites with one atom of another, as in common salt (NaCl), where one atom of sodium unites with one atom of chlorine. The next case is where two atoms of one ele- ment unite with one atom of another, as in water (H 2 O), where two atoms of hydrogen unite with one of oxygen. Other relations also exist with which the student will soon become familiar. 16, Atomic Weights. It is evident that, however small atoms may be, they must still have some weight. It is true that the weight of the heaviest atom is so slight that INTEODUCTWMj^ ' -flVV ^ it could not be determined by the mo^^fSsffieDalance ever constructed, but it is also true that it is not neces- sary to know the absolute weights of the atoms. If we can determine their relative weights, all purposes will be suffi- ciently answered : and this has been done. For this pur- pose the hydrogen atom has been taken as unity, and the relative weights of the atoms of the other elements, as compared with the hydrogen atom, have been determined. How this has been accomplished will be explained here- after ; for the present it must suffice to say that the atom of oxygen has been estimated to be 16 times as heavy as the hydrogen atom, the atom of iron 56 times as heavy, and the atom of mercury 200 times as heavy ; and so, like- wise, certain numbers have been assigned to the atoms of all the known elements. Now, these numbers are called the atomic weights of the elements. Moreover, since these numbers fix the ratios in which the elements combine, they are also called Combining Numbers ; e.g. 56 and 32 are respectively the combining numbers of iron and sulphur. The atomic weights now assigned to the elements are given in the third column of Art. 10. 17. Molecules. We have already learned (Exp. 3) that the atoms of silver unite with the atoms of chlorine to form silver chloride. If we consider a quantity of silver chloride containing but one atom each of silver and chlorine, it is evident that no smaller quantity of silver chloride could exist, since the atoms themselves are indivisible ; and if we take away, for example, the atom of chlorine, free silver is obtained (Exp. 6). To such a smallest possible quantity of a chemical compound that can exist as such the term Molecule is applied. 10 INTRODUCTION. 18. Molecular Formulae. In representing the molecules of compound bodies, the symbols of the elements composing those bodies are written side by side, thus : silver nitrate, AgNO 3 ; sulphuric acid, H 2 SO 4 ; potassium nitrate, KNO 3 ; etc. If we wish to write any number of molecules of a substance, figures are used : thus, 3 KNO 3 means three molecules of potassium nitrate ; 2 H 2 O, two molecules of water; etc. In the case of the molecules of the elements it is cus- tomary to write the number of atoms in the molecule by means of a subscript figure : thus, H 2 , O 2 , N 2 , etc., represent molecules. NOTE. It has been a very difficult task to determine the molecular for- mulae of the compounds. How this may be done will be explained in a subsequent chapter. Ex. Determine the number of oxygen atoms represented in the fol- lowing : 3 H 2 S0 4 ; 8 HN0 3 ; 16 K 2 Cr 2 O 7 ; 24 H 2 ; 5 Ca(N0 3 ) 2 . 19. Chemism, or Chemical Affinity. The force causing atoms to unite with one another to form molecules is called Chemism. Between the atoms of any two elements this force is always a constant quantity ; but it varies for the atoms of any other element when taken with either of these two elements. EXERCISES. (For Review or Advanced Course.) 1. Attach threads to the four corners of a small square of wire gauze, and then place on the gauze a crystal of copper sulphate, CuSO 4 . Now suspend the crystal on the gauze in a beaker of water. Note the phenom- enon of solution. 2. Will alcohol dissolve in water ? Will sulphuric acid ? Will oil ? Will camphor gum dissolve in water ? in alcohol ? What will dissolve rubber gum ? 3. Place a beaker of fresh well-water in a warm place, and allow it to remain quiet for some time. What collects on the sides of the glass ? Is INTRODUCTION. 11 air soluble in water ? Is ammonia gas ? Name some other gases that are soluble in water. 4. Define a solvent ; a menstruum ; a tincture ; a fluid extract ; a sat- urated solution ; a dilute solution. 5. Carefully weigh an evaporating- dish, and then place in it exactly 0.65s zinc. Place the evaporating-dish on the sand-bath, and cover the zinc with hydrochloric acid, HC1. Heat the sand-bath gently, and add more hydrochloric acid, if necessary, till the zinc is all dissolved. You thus obtain a solution of zinc chloride, ZnCl 2 . Now carefully evaporate this solution to dryness, and then place the evaporating-dish under a small bell-glass till the dish and its contents are cool. Rapidly weigh the dish and its contents, and from this weight subtract the weight of the dish. This gives the weight of the zinc chloride. From this last weight subtract the weight of the zinc, and thus obtain the weight of the chlorine that united with the zinc. From the formula ZnCl 2 it appears that 0.71 parts of chlorine should unite with 0.65 parts of zinc ; hence the zinc chloride should weigh 0.65s + 0.71g= 1.36s. What does this experiment show ? NOTE. Owing to experimental errors and to the influence of moisture, these results will only be approximated. 6. Moisten with water a pine splinter or a partly burned match, and dip it into dry powdered sodium carbonate, NajCO 3 . Heat the match in the Bunsen flame till dry and charred. If the match be not coated with the carbonate, moisten, and proceed as before. With the warm match take up a small bit of silver chloride (Exp. 3), which is to be heated hi the Bunsen flame. Do you thus obtain a bead ? Compare with Exp. 6. Try in this way some compounds of lead and copper. CHAPTER I. OXYGEN. DATA FOR COMPUTATIONS. Symbol, O ; Molecular Formula, O 2 ; Atomic Weight, 10 ; Specific Gravity, 1.1056 ; Weight of I 1 at C. and 160 m , 1.430*. 20, Occurrence. Oxygen is the most abundant of all the elements. It occurs free in the atmosphere, of which it constitutes about 23 per cent by weight. In its com- pounds oxygen occurs most plentifully, since from 44 to 48 per cent by weight of the earth's crust, and 88 to 89 per cent by weight of water, consists of oxygen. Every element except fluorine unites with oxygen to" form compounds. 21, Preparation and Properties. Since oxygen occurs free in the atmosphere, we have all had some experience with it in that form. As it thus occurs it is largely diluted with nitrogen and other gases. Notwithstanding our familiarity with atmospheric oxygen, it will be well, in this connection, to make one or two experiments. EXP. 8. Ignite a common match, and when burning freely hold the tip upward. Note the flame, and how the match is consumed. When a portion of the match is charred, extinguish the flame, and note the behavior of the glowing coal which remains. EXP. 9. Cease breathing for about fifteen seconds, and note the effect upon the system. Ex. When the flame is extinguished, does the match still continue to waste away ? How does the flame differ from the slow burning of the 12 OXYGEN. 13 coal ? What remains after the charcoal has burned away ? Is wood an element or a compound ? For how long a time would it be safe to " hold the breath " ? Define suffocation ; strangulation ; asphyxiation. The two great uses of free atmospheric oxygen are to support respiration and combustion. All animals consume free oxygen during respiration. In the case of air-breathing animals the blood, while passing through the lungs, is thoroughly brought into contact with the air ; and thus is the blood purified. In water-breathing animals, like fishes, gills take the place of lungs ; while in the still lower orders, pores and spiracles, distributed over the surface of the body, serve a like purpose. When we say a body burns, it is equivalent to saying that it unites with oxygen. In fact, when wood, coal, gas, oils, etc., are burning, these substances are entering into chem- ical combination with the oxygen of the air. A flame is a burning gas ; hence solids must be heated to a temperature (the kindling-point) high enough to convert them into gases before flames are produced. Substances may oxidize or burn at high or low temperatures. When flames are produced, the temperature is high ; but when iron is rust- ing, or wood rotting, or oxygen combining with the im- purities of the blood, the temperature is low. It matters not, however, at what temperature the oxidation may oc- cur ; a given weight of a substance, when oxidized, always produces the same quantity of heat. Ex. Define combustion ; oxidation. Why can a lump of coal not be ignited by means of a match? Explain the philosophy of ''kindling- wood." Why does blowing a fire hasten combustion, while the same treatment would extinguish a candle flame ? Explain the use of chim- neys, drafts, and dampers in stoves and furnaces. Pure oxygen varies much from the diluted gas in the phenomena which it exhibits during combustion. There 14 OXYGEN. are several ways of preparing pure oxygen, but trie best ones are by decomposing its compounds, such as red oxide of mercury or mercuric oxide, HgO, and potassium chlo- rate, KClOo, by means of heat. EXP. 10. Place a small quantity of mercuric oxide in a test- tube. Heat the test-tube just under the oxide in the Bunsen flame for a short time, frequently inserting a glowing match. Ex. Compare with Exp. 8. What collects on the sides of the tube ? Into what substances has the oxide of mercury been separated ? Has oxygen an odor ? any color ? Why are these two latter facts wise provisions ? This method of preparing oxygen would be too expensive when large quantities of that gas are needed for laboratory purposes. In the latter case potassium chlorate is used. In order to have the gas liberated at as low a temperature as possible, one-fourth part, by weight, of black oxide of manganese or manganese dioxide, MnO 2 , is mixed with the potassium chlorate. The manganese dioxide under- goes no change, but the potassium chlorate is reduced to potassium chloride, KC1. EXP. 11. Place a small quantity of this mixture in a test- tube, and proceed as in Exp. 10. Compare the results with that experiment. EXP. 12. Place (say) 100 g potassium chlorate and 25 g man- ganese dioxide in an oxygen generator. Be sure that the chemicals are pure. Heat carefully, and collect the gas in gas-bags or in jars over the pneumatic trough, or in gas- holders. Now prepare the materials for the following exper- iments, which are best shown in a darkened room. EXP. 13. Make a pencil of bark charcoal, and tie around it an iron wire. Ignite the charcoal, and by means of the wire lower it into a jar of oxygen. Note the scintillations. OXYGEN. 15 EXP. 14. Draw the temper from a watch-spring by heating it in the Bunsen flame, and uncoil it. File one end thin, and bend it into a loop. Now heat the loop, and make a sulphur tip for the spring by dipping the heated loop into flowers of sulphur. Ignite the sulphur, and carefully place the spring in a jar of oxygen. Note the sulphur flame and the combustion of the spring (Fig. 4). EXP. 15. Make a small pencil by twisting together fine iron wires; tip it with sulphur, and proceed as in the last experiment. NOTE. A large bottle with its bottom removed, and resting on a dinner-plate containing water, makes a good and cheap appara- tus for the last three experiments ; and it will also answer for the next experiment if no globe be at hand. EXP. 16. Place a bit of dry phosphorus as large as a pea in a deflagrating-spoon, always remembering to handle the phos- phorus with pincers, and not with the fingers ; ignite the phosphorus, and lower it into a globe of oxygen gas. Note the color of the flame. This experiment produces what is known as the " Phosphorus Sun." Ex. All these experiments furnish examples of what ? Write a short description of each experiment. Why do these phenomena not occur in atmospheric oxygen ? Enumerate the properties of oxygen. 22. Crystallization. EXP. 17. Place the residue remain- ing in the oxygen generator (Exp. 15) in a large beaker-glass, and add about a litre of hot distilled water. Agitate the con- 16 OXYGEN. tents of the beaker with, a glass rod until the lumps have all disappeared; the potassium chloride is now dissolved, while the manganese dioxide is unaltered. Pour the contents of the beaker on a large filter-paper fitted to an appropriate funnel, and receive the filtrate in a large evaporating-dish. Now evaporate the contents of the dish down to less than J 1 , and then set the dish away to cool, leaving it for several hours un- disturbed. Crystals of potassium chloride will form in the dish. These crystals may be removed from the solution by filtering through a fresh filter-paper ; and they may be dried by simply allowing them to remain on the filter-paper, exposed to the air. A second crop of crystals may be had by concen- trating the remaining solution ("mother liquor"), and cooling as before. NOTE. The manganese dioxide may be dried on the filter-paper and put away for future use. Ex. What processes were employed in obtaining the crystals ? Define crystallization ; " mother liquor " ; a crystal. 23. Ozone. Oxygen exists in a peculiarly modified and unstable form called ozone. In this form three volumes of ordinary oxygen are condensed to two volumes ; accord- ingly the formula of its molecule is written O 3 . Ozone occurs free in the atmosphere in minute quan- tities, probably being produced through the agency of electricity and by the vaporization and condensation of atmospheric moisture. EXP. 18. Fill a test-tube about one-third full of a satu rated solution of potassium permanganate, K 2 Mn 2 8 , and then cautiously add a few drops of sulphuric acid, H 2 S0 4 . Test the escaping gas by a glowing match. Note the odor. Sus- pend in the tube a strip of paper moistened in a solution of starch paste and potassium iodide, K. Ex. Compare ozone with pure oxygen. OXYGEN. 17 Ozone is much more energetic in its action than the ordinary oxygen, and especially is this held to be true concerning its action upon organic matter and noxious exhalations from unhealthy localities. It is also believed that ozone is capable of destroying many kinds of disease germs. 24. Tests for Oxygen and Ozone. 1. Free oxygen gas is detected by its lack of odor, taken together with its action upon a glowing match. If the gas be dilute, the coal barely continues to glow; but if pure, the match bursts into flame. 2. Ozone is detected by its odor, by its kindling a glow- ing match, and by its coloring blue a strip of paper moist- ened in a solution of starch paste and potassium iodide. EXERCISES. (For Review or Advanced Course.) 1. The molecular weight of a compound substance is equal to the sum of the atomic weights of the elements forming that substance. Compute the molecular weights of the following : HgO ; KC1O 3 ; KC1 ; H 2 SO 4 ; AgN0 3 . 2. How much oxygen is there in 100s HgO ? SUGGESTION. The molecular weight of HgO is (Hg) 200 + (O) 16 = 216. Now ^ T \ of any weight of HgO is oxygen. 3. How many litres of oxygen at C. and 760 mm are there in 484s of oxygen ? See data for computations. 4. How many litres of oxygen at C. and IGQ 1 * may be had from 150s KC10 3 ? 5. How many pounds of oxygen are there above one square foot of the earth's surface at the level of the sea ? SUG. At the sea-level the atmosphere weighs about fifteen pounds to the square inch. 6. Hold a short piece of stick phosphorus by means of a pair of pin- cers, and scrape it clean under water. Loop a thread around the phos- phorus, and suspend it in a bottle containing a few drops of water. Set 18 OXYGEN. the bottle in a moderately cool place (15 to 20 C.). Now suspend in the bottle a strip of paper prepared for testing ozone. Note from time to time the color of the paper. 7. Set a Toepler-Holtz machine in motion, and after a few sparks have passed, note the odor. Test the vicinity of the poles with ozone paper. 8. Explain the construction of the Bunseii burner. Why is the Bunsen flame colorless ? 9. Examine the blow-pipe flame. Note the inner bluish cone and the outer slightly luminous layer. This latter portion of the flame contains an excess of oxygen, heated to a very high temperature. Substances placed in this part of the flame are oxidized, hence the name Oxidizing flame. The best place to hold a substance to be oxidized is just beyond the bluish tip. The central part of the flame contains an excess of highly heated carbon and hydrogen, and substances placed within the cone loose their oxygen or are reduced, hence the name Reducing flame. 10. Bend a small loop on a piece of platinum wire. Heat the loop, and dip it into powdered borax. Fuse the borax on the wire to a colorless bead. Now slightly moisten the bead with ferrous sulphate, FeSO 4 , and heat it in the oxidizing flame. The bead becomes reddish in color when hot, light yellow when cold. Again heat this bead in the reducing flame ; it becomes colorless. Why ? CHAPTER H. HYDROGEN AND ITS OXYGEN COMPOUNDS. DATA FOR COMPUTATIONS. Symbol, H ; Molecular Formula, H 2 ; Atomic Weight, 1 ; Specific Gravity, 0.0692 ; Weight of I 1 at C. and 760 mm , 0.0896. 25. Occurrence. Free hydrogen occurs only in insignifi- cant quantities, being found chiefly in volcanic gases. In its compounds, however, hydrogen occurs plentifully. Thus, of water, H 2 O, it constitutes 11.1 per cent by weight ; while it is always present in ammonia, acids, and organic com- pounds. 26. Preparation and Properties. Hydrogen is readily ob- tained from its compounds, such as water, H 2 O, and from acids, such as hydrochloric acid, HC1, and sulphuric acid, H 2 SO 4 . EXP. 19. Place about & mercury in a porcelain mortar ; on the mercury place about 0.5 g metallic sodium. Now, by means of a pestle, bear the sodium down through the mercury to the bottom of the mortar, and then twist the pestle till the sodium and mercury unite to form an amalgam. Fill a test-tube half full of water, and into this drop a piece of the amalgam. Xote the bubbles of gas escaping, and note their color and odor, if any. Hold the tube firmly, and care- fully bring a lighted match near its mouth. Ex. What became of the mercury used in making the amalgam? Kub some of the water in the test-tube between the thumb and finger, and note the feeling. Has the water changed ? Dip a strip of red litmus 19 20 HYDROGEN AND ITS OXYGEN COMPOUNDS. paper in the water, and note the change in the color of the paper. Is an alkali present ? (Suo. Alkalies turn red litmus paper blue.) Is hydrogen inflammable ? Has it an odor or a color ? Define an amalgam. In this experiment hydrogen was obtained from water. One atom of sodium displaced or set free one atom of hydrogen, and formed the alkali, caustic soda, or sodium hydroxide. The reaction that is, the changes that took place can best be shown by means of an EQUATION. Thus, Na + H 2 = NaOH + H. This equation is read, "Sodium and water give sodium hydroxide and hydrogen." Equations are further useful, since they enable us to tell what proportions, by weight, of substances take part in chemical reactions. This is accomplished by means of the weights of the atoms and of the molecules represented in the equation. For example, 23 (Na) + 18 (H 2 0) = 40 (NaOH) + 1 (H). That is, 23 parts, by weight, of sodium react with 18 parts of water to give 40 parts of sodium hydrox- ide and 1 part of hydrogen. Ex. Explain these equations : HgO (heated) = Hg+0, and KC10 3 (heated) = KC1 + 3 O. EXP. 20. Arrange a jar filled with water, as in Fig. 5. Wrap a piece of sodium amalgam in wire gauze, and place it under the mouth of the jar. Hydrogen rises in the jar. Test the gas by raising the jar, mouth downwards, and thrusting a lighted taper up into the jar. The hydrogen will burn around the mouth of the jar, while the taper will be extinguished. The taper may be relighted in the burning gas. A slight but harmless explosion usually terminates the experiment. EXP. 21. Half fill an evaporating-dish with warm water, and then drop in a small piece of pure metallic sodium (Fig. 6). Also try in this way a small piece of metallic potassium. FIG. HYDROGEN AND ITS OXYGEN COMPOUNDS. 21 NOTE. This experiment may terminate with a slight explosion. Ex. What advantage is gained by using sodium or potassium amal- gam ? Is the water in the evaporat- ing- dish alkaline after adding the metals ? Write the equation for the reaction between K and EXP. 22. Fit a cork with a straight-jet delivery-tube to a generating-flask. In the flask .._-.-_-. place (say) 10 g granulated zinc. Now fill the flask one-third full of dilute sulphuric acid, made by adding one part of acid to five parts of water. Place the cork and jet in position, and when the air is expelled from the apparatus, light the jet of escaping gas. Note the color of the flame. Hold a piece of small iron wire in the flame. Ex- tinguish the flame, and collect the gas in a gas-bag. NOTE. In case the gas is not given off freely, add to the contents of the flask a few nails or a few small crystals of copper sulphate. In this experiment the hydrogen is obtained from sul- phuric acid by means of a reaction with zinc, thus, Zn + H 2 S0 4 = ZnS0 4 + H 2 . No note is taken of the water added, since this merely serves to dissolve the zinc sulphate, ZnSO 4 , as fast as that salt is formed. Ex. What is the color of the hydrogen flame ? Has the flame a high temperature ? By means of a rubber tube fit a common clay pipe to the gas-bag filled with hydrogen, and blow a few hydrogen soap-bubbles. Is hydrogen lighter than air ? Touch a bubble with a candle- flame. Write the equation for Exercise 5 at the close of the Introduction, where zinc and hydrochloric acid react. EXP. 23. Fire the hydrogen pistol to illustrate the explo- siveness of a mixture of hydrogen and oxygen. EXP. 24. Fill a collodion balloon with hydrogen gas, and then release the balloon in the laboratory. After some hours 22 HYDROGEN AND ITS OXYGEN COMPOUNDS. the balloon will settle to the floor. When this has occurred, test the gas in the balloon for hydrogen. Some or all of the hydrogen in the balloon has passed out into the air through the pores of the balloon, and air has entered through the same channels. This illustrates what is termed Diffusion of gases through porous parti- tions. It is in this way that oxygen passes through the delicate membranes of the pulmonary capillaries to purify the blood in its passage through the lungs. FIG. 7. EXP. 25. Arrange a delivery-tube for a hydrogen appa- ratus, as shown in Fig. 7. Using the same materials as in Exp. 22, fill a jar with hydrogen. Then carefully lift up the jar, keeping its mouth downwards. Now slowly bring the mouth of the jar upward, underneath the mouth of a second jar, held mouth downward. When the first jar has reached an upright position, remove it, and test its contents for hydrogen. Also test the contents of the second jar for the same gas. Ex. What has occurred ? Enumerate the properties of hydrogen. 27. Test for Hydrogen. Hydrogen may be detected by its flame and by its behavior, as in the preceding experi- ments. COMPOUNDS OF HYDROGEN WITH OXYGEN. 23 COMPOUNDS OP HYDROGEN WITH OXYGEN. 28. Hydrogen and oxygen unite to form but two chem- ical compounds : water, H 2 O ; and hydrogen dioxide, H 2 O 2 . Of these compounds, water is by far the most important. WATER. 29. Occurrence. Water occurs widely distributed in nature. Permeating the atmosphere and soil, flowing in streams and forming lakes and oceans, water is everywhere found. Although the properties of water are familiar to all, nevertheless, since this is the first chemical compound to be studied in detail, it will be necessary to make a few experiments illustrating some of the methods employed by chemists in investigating the composition and properties of bodies. 30. Preparation and Prop- erties. Let us first make a qualitative experiment in order to learn if water can be produced synthetically. EXP. 26. Arrange an ap- paratus as shown in Fig. 8. G is a hydrogen generator, containing zinc and dilute sulphuric acid. B is a dry- ing-bulb, containing granu- lated calcium chloride, CaCL. Introduce the acid through the funnel-tube, and when the apparatus is free from air, ignite the hydrogen gas escaping through the jet, and place the bell-jar, E, over the flame. Note what collects on the sides of the jar. FIG. 8. 24 COMPOUNDS OF HYDROGEN WITH OXYGEN. Ex. Why, in this experiment, should the hydrogen gas be perfectly dry ? When the hydrogen is burning, with what constituent of the air does it unite ? What substances, then, enter into the composition of water? Next let us make a quantitative experiment to determine synthetically in what proportions, by volume, hydrogen and oxygen unite to form water. This may be accom- plished by means of the apparatus (lire's eudiometer) shown in Fig. 9. EXP. 27. The graduated limb and a part of the plain limb are to be filled with mer- cury. Then, by means of a curved glass tube, 10 divisions of the graduated limb are filled with pure oxygen; 25 divisions of pure hy- drogen are next to be added. Now bring the mercury to the same level in both limbs, and while firmly holding the thumb over the plain limb, pass an electric spark through the wires attached to the graduated limb. 20 di- visions of hydrogen will p unite with 10 divisions of oxygen to form water. It thus appears that these gases unite in the proportion of 2 volumes of hydrogen to 1 volume of oxygen. These two experiments illustrate how the composition of certain bodies may be determined by Synthesis. An- other and more extensively employed method is termed Analysis. In the case of water, the analysis may be made by a process termed Electrolysis. The apparatus (Hoff- mann's apparatus) used is shown in Fig. 10. FIG. 9. FIG. 10. COMPOUNDS OF HYDROGEN WITH OXYGEN. 25 EXP. 28. Add one part, by weight, of sulphuric acid to 20 parts of distilled water. Open the stop-cocks S and S', and then pour the acidulated water into the tube B until it issues from the tubes and H. Close the stop-cocks, and fill B up to the bulb. Connect the platinum wire Z, which is melted through the tube H and terminates in a platinum strip, with the zinc pole of a Grove's battery, consisting of five or six cells. Also connect the platinum wire P (which is like Z in every respect) to the platinum pole of the battery. Hydrogen collects in the tube H, and oxygen in the tube 0. Note the comparative volumes of the gases collected. The hydrogen may be tested by slightly opening the stop- cock S' and igniting the escaping gas. Open the stop-cock S, and test the oxygen by means of a glowing match. Ex. What relative volumes of hydrogen and oxygen were liberated ? Compare the results of this experiment with those obtained in Exp. 27. Define synthesis ; analysis ; a qualitative experiment ; a quantitative experiment ; qualitative analysis ; quantitative analysis ; electrolysis ; an electrolyte. The proportions, by weight, in which oxygen and hydro- gen unite to form water may now be determined. The preceding experiments show conclusively that in water 2 volumes of hydrogen are united with 1 volume of oxygen. Now let us assign some absolute value to each volume, so that the weights of the volumes may be deter- mined. For example : take 2 1 of hydrogen and I 1 of oxy- gen ; then, multiplying the number of litres of each gas by the weight of I 1 of that gas, the proportion, by weight, becomes 2 x 0.0896 : 1 x 1.430 or 0.1792 : 1.430. This ratio reduced to its lowest terms becomes very nearly 1:8; i.e. 1 part, by weight, of hydrogen unites with 8 parts, by weight, of oxygen. One way of determining the molecular formula of water is as follows : 26 COMPOUNDS OF HYDROGEN WITH OXYGEN. It must be remembered that the symbols of the elements represent both atoms and the weights of the atoms. Now, since the atomic weight of oxygen is 16, the ratio of 1 : 8 would only require \ an atom of oxygen to 1 atom of hydrogen, which is not supposable; but if we multiply the ratio by 2, it becomes 2 : 16, or 2 atoms of hydrogen to 1 of oxygen. Now these are the fewest number of atoms that could possibly form water. Moreover, experi- ment has shown that the molecular weight of water is 18. Hence there is but one conclusion: no larger number of 9,toms enter into the molecule, and water is H 2 O. How molecular weights are determined will be explained here- after. The solvent action of water upon many substances is well understood. Sugar, salt, and similar substances, as well as many liquids and gases, are readily soluble in water. But the solvent powers of water are greater than superficial observation would indicate. EXP. 29. Place a few clean pine shavings in an evaporat- ing-dish half full of ordinary well water. Boil the contents of the dish for a short time, and then filter. Note the taste and odor of the filtrate Ex. Has the water dissolved a portion of the pine ? What makes water that has stood in wooden pails " taste " ? Limestone, or calcium carbonate, CaCO 3 , and ferrous carbonate, FeCO 3 , are insoluble in pure water ; but in water charged with carbonic acid gas, CO 2 , these sub- stances are readily soluble. When the carbonic acid is expelled by boiling, they both become insoluble again and are precipitated. In the case of many other substances, such as certain organic compounds, and metals like lead and copper, impure water will act as a solvent where pure water would have no action. COMPOUNDS OF HYDROGEN WITH OXYGEN. 27 EXP. 30. Fill a beaker with ordinary well-water. Place the beaker on the sand-bath, and boil the water for a short time. Note any cloudiness or precipitate that may appear in the water. Ex. Why did the precipitate form ? Why is a crust formed on the inside of a tea-kettle in which hard water is boiled ? Explain the forma- tion of fossils. Knowing that the coloring-matter of vegetation is partly composed of iron, explain why the waters of springs and creeks deriving their supplies from marshy lands contain iron. Why do these waters deposit iron ores ? Explain the formation of sedimentary rocks. How did the deposition of sandstone differ from that of limestone ? Which will dissolve more common salt, hot or cold water ? Why is water flow- ing through lead pipes dangerous to drink ? Why is drinking-water liable to contain organic matter ? In what ways is water useful to plants and animals ? Besides acting as a solvent, water fulfils another ex- tremely important office : it acts as a heat regulator. In changing l kg of ice from a solid at C. to a liquid at the same temperature, 79 heat-units, or calories, are ren- dered latent; while into l kg of water, in passing from a liquid at 100 C. to steam at 100, 536 calories disap- pear. When water freezes, or when steam condenses, the latent heat is again given up to the atmosphere or -to surrounding objects. Moreover, water receives and parts- with its heat very slowly, and thus it modifies climatic extremes. Water is at its maximum density at + 4 C. When its temperature passes either above or below this point, water expands. Consequently, ice is lighter than water; and forming, as it does, at the surface of lakes and rivers, it acts as a protection to the water underneath. Snow serves as a protection to the ground, and clouds prevent a rapid loss of heat by radiation from the surface of the earth. 28 COMPOUNDS OF HYDROGEN WITH OXYGEN. FIG. EXERCISES. (For Review or Advanced Course.) 1. How many litres at C. and 760 mm are there in 4.326s hydrogen ? 2. How many litres of oxygen would be required to form water with the hydrogen in the preceding exer- cise ? What would the oxygen weigh ? How much water would be formed ? 3. Bearing in mind that one calorie of heat will raise l k s of water through 1 C., how many calories would be required to convert 10 k B of ice at into steam at 100 ? 4. Name 10 substances that are soluble in water, and 10 that are insoluble. 5. Prepare and test hydrogen di- oxide, H 2 2 , thus : Make a mixture of 2 CC sulphuric acid and 20 CC water. Place the mixture in a beaker, and when cool, add, with constant stir- ring, 6s finely pulverized barium dioxide, Ba0 2 . Filter the contents of the beaker, or allow the white precipitate to subside, thus obtaining a clear solution of hydrogen dioxide : BaO 2 + H^SO^ = H 2 O 2 + BaSO 4 . The white precipitate is barium sulphate. Test the hydrogen dioxide thus: To about a half of a test-tube of the solution add successively 2 or 3 drops of sulphuric acid, 5 or 6 drops of potassium dichromate, K 2 Cr 2 O 7 , and about 2 CC ether, FIG. 12. (C 2 H 5 ) 2 O. Now shake the tube thoroughly, and note the blue-colored solution obtained. 6. Determine the total residue in a sample of drinking-water, thus : Weigh an evaporating-dish, and in it carefully evaporate to dryness over a water-bath one-half litre of the sample. Place the dish and its contents over a dish containing strong sulphuric acid, and cover the whole with a small bell-jar. When cool, weigh the dish and its contents ; from this weight subtract that of the dish, and multiply the difference by 2. The result is the total residue per litre sought. 7. Explain the principles involved in the oxyhydrogen blow-pipe (Fig. 11). The tip is shown in Fig. 12. CHAPTER III. NITROGEN AND ITS COMPOUNDS WITH HYDROGEN AND OXYGEN. DATA FOR COMPUTATIONS. Symbol, N ; Molecular Formula, N 2 ; Atomic Weight, 14 ; Specific Gravity, 0.971 ; Weight of I 1 at C. and TeO 11 " 11 , 1.256*. 31. Occurrence. Nitrogen is found free in the atmos- phere, of which it constitutes nearly four-fifths part by volume, or 77 per cent by weight. In compounds, nitro- gen occurs in such substances as ammonia, NH 3 ; potassium nitrate, or saltpeter, KNO 3 ; sodium nitrate, or Chili salt- peter, NaNO 3 ; and in many organic compounds. 32. Preparation and Proper- ties. EXP. 31. Float an iron sand-bath or a tin cup on the water of the pneumatic trough, or of any convenient vessel. Into the cup drop a bit of ^ phosphorus. Ignite the phos- jB phorus, and then carefully ! place down over it a bell-jar (Fig. 13). White fumes of phosphorus pentoxide, P 2 O 5 , and perhaps of the trioxide, P 2 3 , quickly fill the jar. These fumes soon subside, and dissolve in the water, leaving the nitrogen nearly pure. Ex. What substance was removed from the air in the jar by the burning phosphorus ? Are the fumes formed solid or gaseous ? Why would gaseous products in this experiment be objectionable ? 29 FIG. 13. 30 NITROGEN AND ITS COMPOUNDS. EXP. 32. Lower a burning taper into a jar of nitrogen. Try a glowing match. Compare the phenomena observed with those obtained in oxygen. EXP. 33. Place a live mouse in a jar of nitrogen. Ex. Is nitrogen a supporter of combustion ? of life ? What purpose does nitrogen serve in the atmosphere ? Is nitrogen poisonous ? Would a mixture of air and nitrogen explode ? Has nitrogen any color or odor ? Enumerate the properties of nitrogen. Nitrogen possesses a very feeble chemism for the other elements, in consequence of which it does riot enter directly into combination with them. Indirectly, however, it forms many important compounds, as will appear further on. Owing to its passive nature, nitrogen in small quantities is not easily detected. AMMONIA, NH 3 . 33. Occurrence. Ammonia, which is a chemical com- pound of nitrogen and hydrogen, is a very important sub- stance. It occurs widely distributed in the atmosphere and in nearly all waters. Rain, snow, ice, and the waters of springs, deep and shallow wells, lakes, streams, and seas, all contain considerable quantities of ammonia. It is a wise provision that ammonia is thus distributed, since from it plants build up the nitrogen-bearing portions of their tissues, the albuminoids, found in seeds, roots, and leaves. Animals, in turn, consume these tissues, and thus acquire the material for building up the nitrogen- bearing portions of their bodies, the proteids, found in muscles and in other parts of the body. Ammonia compounds occur but sparingly in nature, although they are important manufactured articles of com- merce. NITROGEN AND ITS COMPOUNDS. 31 34. Preparation and Properties. EXP. 34. In one hand place a little powdered quicklime, CaO, and in the other put an equal bulk of powdered ammonium chloride, or sal-am- moniac, NH 4 C1. Note that neither has an odor. Rub these substances between the palms of the hands, and carefully smell the gas produced : CaO + 2 NH 4 C1 = 2 NH 3 + CaCl 2 + H 2 0. The residue in the hands is chiefly calcium chloride, Ex. Has ammonia a color ? Place a strip of moistened red litmus paper in the fumes, and note whether they are alkaline. In this experiment, ammonia was liberated from one of its compounds by means of a stronger, or "fixed" alkali. Since ammonia and its compounds are vaporized by the action of heat, it is called the " volatile " alkali ; while all other alkalies are not readily vaporized, and are designated as the " fixed " alkalies. All the fixed alkalies will liberate ammonia from its compounds. EXP. 35. To a solution of any ammonium salt in a test- tube add a solution of potassium hydroxide, KOH. Warm the tube gently, and test as usual the properties of the gas evolved. Test the alkalinity of the gas by means of a moist red litmus paper. Ammonia gas dissolved in water is sold in every drug store as aqua ammonice. Aqua ammonise is prepared from about the same materials used in Exp. 34. The ammonium chloride or sulphate is procured from gas-works, where it is obtained as a by-product by passing the crude gas from the retorts through dilute hydrochloric or sulphuric acid. The interesting process of manufacturing aqua ammonise is illustrated in Exp. 36, which also shows a general pro- cess of dissolving gases in water. Sometimes the gas is forced iuto the water by means of its own pressure, ol> 32 NITROGEN AND ITS COMPOUNDS. tained by closing air-tight the generator, the washing- apparatus, and the receiver. EXP. 36. Arrange an apparatus as in Fig. 14. Then take (say) 50 g powdered quicklime and 100 g ammonium chloride, and moisten each separately with water until thick pastes are formed. Disconnect F, and rapidly introduce these pastes into it, and join immediately with the wash-bottle A, which acts as FIG. 14. a safety apparatus to prevent any water from flowing back into the generating-flask F. B and C are here used as condensers, and the ammonia in passing through them is dissolved in the water they contain. It is best to surround B and C with pounded ice and salt. Aqua ammonise is found in these two bottles at the conclusion of the experiment. Ammonia is very soluble in water. l cc of water, at C., dissolves 1148 CC of ammonia. Atmospheric ammonia is produced by the decay of nitrog- enous organic matter ; and through the agency of atmos- pheric moisture it finds its way into the waters of all localities. Ammonia was formerly prepared by distilling hoofs, NITROGEN AND ITS COMPOUNDS. 33 hides, and horns, whence arose the name of "spirits of hartshorn." EXP. 37. Place a few drops of ammonia on a piece of por- celain or platinum foil, and carefully evaporate to dry ness. Next treat in a similar manner a few drops of hydrochloric acid, HC1. Does either give a residue ? Now make a mixture of the two, and proceed as before. Note the residue. Ammonia unites with acids to form salts, as shown in the foregoing experiment : The salt is called ammonium chloride, and the group of atoms, NH 4 , is called Ammonium, owing to some resem- blances which it bears to the metals. Under a pressure of seven atmospheres, at 15.5 C., am- monia condenses to a liquid. When this liquid vaporizes, as in the case of water, large quantities of heat are rendered latent. Advantage has been taken of this to manufacture ice. Liquid ammonia is simply allowed to evaporate in closed iron pipes over which water is slowly trickling. Since ammonia neutralizes acids, it may be applied when acids are spilled on the clothes or on the flesh. Again, when poisonous or irritating gases have been inhaled, ammonia vapors act as an antidote. When ammonia is inhaled, it produces a stimulating effect upon the system. 35. Tests for Ammonia. To a solution supposed to con- tain ammonia add a solution of potassium hydroxide, KOH, and warm gently. If ammonia be present, it may be recog- nized (1) By its odor. (2) By its turning moistened red litmus paper blue. By holding a warm glass rod, which has been mois- 34 NITROGEN AND OXYGEN. tened in hydrochloric acid, over the tube, white fumes of ammonium chloride, NH 4 C1, may be seen, and the rod when dry will be found coated with the same salt. NITROGEN AND OXYGEN. 36. There are five compounds of nitrogen and oxygen known : Nitrogen monoxide, N 2 0. Nitrogen dioxide, N 2 2 , or NO. Nitrogen trioxide, N 2 3 . Nitrogen tetroxide, N 2 4 , or NO 2 . Nitrogen pentoxide, N 2 5 . Of these compounds, the first is of most practical im- portance. All are gases except the last, which is a crys- talline solid. The last four will receive but a passing notice. The second oxide is formed when a metal and nitric acid, HNO 3 , react. When the gas thus produced escapes into the air, it absorbs oxygen, producing varying amounts of the next two higher oxides, and thus giving rise to the brownish red fumes always noticed when nitric acid is acting on metals, thus : EXP. 38. Place a bit of copper in an evaporating-dish, and add enough nitric acid to cover the copper. Warm the dish gently, and note the colored fumes above the dish : 3 Cu + 8 HN0 3 = 3 Cu(N0 3 ) 2 + 2 NO + 4 H 2 0. Portions of the nitrogen dioxide unite with the oxygen of the air thus : NO-f = N0 2 and 2NO + = N 2 3 . The blue salt formed is copper nitrate, Cu(N0 3 ) 2 . NITROGEN AND OXYGEN. 35 NITROGEN MONOXIDE, N 2 O. 37. Preparation and Properties. This gas is known as nitrous oxide, and also as " laughing-gas." It never occurs free, but it is manufactured by dentists and by others for anaesthetic purposes. There are several methods of obtain- ing nitrogen monoxide, but the one always used consists in decomposing ammonium nitrate, NH 4 NO 3 , by means of heat : - NH 4 N0 3 (heated) = N 2 + 2 H 2 O. EXP. 39. Place in a test-tube a small quantity of ammonium nitrate, and heat it carefully in the Bunsen flame. Note the odor of the gas produced, and test it with a glowing match and then with a blazing match. Compare the results with those obtained in oxygen. For generating large quantities of nitrous oxide, com- mercial ammonium nitrate is often employed. Coming from this source, the gas is apt to contain impurities dan- gerous to inhale, such as nitrogen dioxide, NO, and per- haps some chlorine or chlorine compounds. In order to remove these impurities, the gas is washed, as shown in the following experiment, which also illustrates the usual method of washing gases : EXP. 40. Arrange an apparatus as shown in Fig. 15. The generator is fitted with a bent, one-bulb, thistle-top tube, con- taining a small quantity of mercury. This makes a safety- valve. The first wash-bottle contains a warm solution of fer- rous sulphate, FeSO^ to remove any nitrogen dioxide. The second bottle contains a warm solution of potassium hydrox- ide, KOH, to remove any chlorine. The third bottle contains warm water. Use about 50 g of ammonium nitrate in the gen- erator, and employ a moderate heat. Collect the gas in gas- bags, as it is soluble in water, and more especially in cold than 36 NITROGEN AND OXYGEN. in warm water. Inhale some of the gas thus prepared, and note the odor and the sweetish taste. When inhaled in considerable quantities, nitrogen mon- oxide produces its effects upon the system in the following order : intoxication, and singing in the ears ; insensibility ; and finally, if the inhalation be continued long enough, death. FeSO 4 KOH FIG. 15. At C., 30 atmospheres' pressure condenses this gas to a liquid ; and if this liquid be mixed with carbon bisul- phide, CS 2 , and evaporated in vacuo^ the very low temper- ature of 140 C. is produced. 38, Tests for Nitrogen Monoxide, This gas closely re- sembles oxygen, from which it is easily distinguished by its sweetish taste and odor, and by its solubility in cold water. 39. The Law of Multiple Proportions, By inspecting the formulae of the oxides of nitrogen, it will be seen that the quantities of oxygen that are umtedwlQk 'IH "KTllo one another as 1:2:3:4:5, while the nitrogen remains con- stant. Such relations as these are frequently found in the com- pounds of elements. In every case the ratio is a simple one, and the element that increases does so by whole num- bers, and not by fractions. This is in strict conformity with the atomic theory. The law of multiple proportions may be stated thus : If two elements, A and B, form several compounds with each other, and if we take any fixed amount of A, then the different quantities of B which combine with this fixed amount of A bear a simple ratio to one another. 40. Determination of Molecular Weights. The molecule of any substance has been defined as the smallest particle of that substance which can exist in a free state. If now we take a molecule of a gas like hydrochloric acid, HC1, that molecule must have at least one atom each of hydro- gen and chlorine, and its molecular weight will be the sum of the weights of these two atoms. Thus, for hydro- chloric acid we have 1 + 35.5 = 36.5. Therefore in such simple gases, where the atomic weights are known, the problem presents no difficulties. But when the constitu- tion of a gas is more complex, as in the second and fourth oxides of nitrogen, difficulties arise. But it has been found that when the molecular weight of a gas is divided by its specific gravity, a nearly constant quantity is ob- tained, i.e. about 28.88. Hence it follows that in any gas the molecular weight = the specific gravity X 28.88. In such cases, then, the specific gravity of the gas gives a key to the molecular weight. Thus, in the second 38 THE NITKOGEN OXACIDS. oxide of nitrogen, the specific gravity found is 1.03845. Now 1.03845 x 28.88 = 29.99, or practically 30. This would make the molecular formula NO, and not N 2 O 2 . In the same way the molecular weight of the fourth oxide of nitrogen was found to be about 46, and its formula NO 2 . There is no certain method of determin- ing the molecular weights of substances which cannot be vaporized. 41. Avogadro's Hypothesis, Avogadro explained the re- lation existing between the molecular weight and the spe- cific gravity of a gas by the following hypothesis : Under the same conditions of temperature and pressure, equal vol- umes of all gases contain the same number of molecules. Thus if one cubic centimetre of one gas has (say) 1000 molecules, then a cubic centimetre of any other gas under the same conditions will also have 1000 molecules. This hypothesis has been of the greatest importance to a cor- rect conception of some facts in theoretical chemistry. See pp. 41 and 42. THE COMPOUNDS OF NITROGEN, OXYGEN, AND HYDROGEN; OR, THE NITROGEN OXACIDS. 42. These three elements unite to form three com- pounds, called acids : Hyponitrous acid (hypothetical), HNO. Nitrous acid, HN0 2 . Nitric acid, HN0 3 . Only the last two acids have been isolated, and none of them occur free in nature in any considerable quantity. Nitric acid is the most important acid of this series, THE NITROGEN OXACIDS. 39 Nitrous acid may be prepared by dissolving nitrogen trioxide in water : This acid is unimportant, but its salts the nitrites occur in impure well-water, being produced during the decay and nitrification of organic nitrogenous substances. NITRIC Aero, HNO 3 . 43. Occurrence. The compounds of nitric acid, potas- sium nitrate, KNO 3 , and sodium nitrate, NaNO 3 , occur quite plentifully in nature, and it is from these substances that this very important acid is obtained. 44. Preparation and Properties. EXP. 41. Place a small quantity of powdered potassium nitrate, KN0 3 , in a test-tube, and then add a few drops of sulphuric acid. Warm the con- tents of the tube gently, and note the fumes given off. Test the fumes with moist blue litmus paper. In this experiment, nitric acid was liberated from one of its compounds thus : KN0 3 + H 2 S0 4 = HKS0 4 + HNOs. Commercial nitric acid, enormous quantities of which are consumed annually, is obtained by treating Chili saltpetre, NaNO 3 , with sulphuric acid in large iron retorts. The vapors of nitric acid are condensed in earthenware con- densers. This process may be illustrated in the laboratory by means of the apparatus shown in Fig. 16. One method of condensation is also illustrated by the experiment. EXP. 42. Place in the retort A (Fig. 16) equal parts, by weight, of potassium nitrate, KNO 3 , and sulphuric acid. Sur- 40 THE NITROGEN OXACIDS. round the receiver R with snow or ice, or allow a stream of cold water to flow over it. Heat the retort gently, when fumes of nitric acid will be given off and condensed in the receiver R. EXP. 43. Heat to redness some powdered charcoal in an iron spoon, and then cautiously add a few drops of the nitric acid, prepared as above. Also treat a fresh portion of charcoal with powdered potassium nitrate, KN0 3 . Nitric acid and its compounds contain much oxygen, which is quite readily given up to other substances under the influence of heat. Hence both the acid and its com- pounds are called oxidizing agents. FIG. 16. / Substances containing carbon and other inflammable constituents are capable of burning in the absence of air when mixed with potassium nitrate. Hence this com- pound is extensively used in the manufacture of gun- powder, which is simply a mechanical mixture of sulphur, charcoal, and saltpetre. Again, gun-cotton is made by treating cellulose, or pure vegetable fibre, with a mixture of sulphuric and nitric acids. Nitro-glycerme is made by treating glycerine with the same acids. EXEKCISES. 41 An efficient explosive owes its power to the large volume of gas that is suddenly liberated during its combustion. Nitric acid unites with most metals to form a class of compounds called nitrates. Now these nitrates are all soluble in water ; hence nitric acid is largely used in the laboratory as a solvent. In the arts this acid also finds many important uses. 45. Test for Nitric Acid. Make a mixture of the sub- stance to be tested with a solution of ferrous sulphate, FeSO 4 , in a test-tube. Now carefully add a small quan- tity of sulphuric acid, without mixing with the contents of the tube. The sulphuric acid will sink to the bottom of the tube, and where the two liquids meet a brown ring will appear. Sometimes the formation of the ring will be aided by tapping the test-tube lightly with the finger. If the contents of the tube be now mixed, the ring will dis- appear and the solution become colorless. NOTE. Bromides and iodides will give nearly this same test, but the solution will not lose so much of its color when shaken when either of these substances is present. But it is always best to test for these sub- stances, when working an unknown, before reporting nitric acid. EXERCISES. (For Revieio or Advanced Course.) 1. How many grammes of laughing-gas may be had from 100& NH 4 N0 3 ? If one litre of this gas at C. and 760 mm pressure weighs 1.972e, how many litres of this gas will be obtained ? 2. By adding one molecule of water to the first, third, and fifth oxides of nitrogen, the following results will be obtained : N 2 O + H 2 = 2 HNO ; N 2 3 + H^ = 2 HNO 2 ; X 2 O 3 + H.,0 = 2 HNO 3 . What acids are thus produced ? Can the first one be actually produced in that way ? Oxides which behave thus are called Anhydrides. Define anhydrides. 42 EXERCISES. 3. The specific gravities of three of the nitrogen oxides are respectively 1.527 ; 1.038 ; 1.5909. What are the corresponding molecular weights of these oxides, and what their molecular formulae ? 4. The specific gravities hitherto given refer to air as the standard, or air = 1. Sometimes hydrogen is used as the standard. Now it is evident that the hydrogen molecule, H 2 , weighs twice as much as the hydrogen atom. Knowing the atomic weights, it is easy to find the density (which is numerically equal to the specific gravity) of gases when referred to the hydrogen unit. Thus, in ammonia, NH 3 , the molecular weight is 14 + 3 = 17. Now, according to Avogadro's hypothesis, equal volumes of hydrogen and of ammonia under like conditions contain the same number of molecules. Whence it follows that if hydrogen be taken as 1, the den- sity of ammonia is 17-^2 = 8.5. A like manner of reasoning will show that the density of any gas referred to the hydrogen unit may be found by dividing the molecular weight by 2. Determine the densities of N 2 ; N 2 3 ; N 2 4 . 5. Read Remsen's Theoretical Chemistry, pp. 32-38, for a fuller dis- cussion of Avogadro's hypothesis and the determination of the molecular weights of the elements and of compounds. Also see Meyer's Modern Theories of Chemistry, pp. 7-17. 6. Write a sketch of the chemist Rutherford, who discovered nitrogen in 1772. 7. How many grammes of ammonia can be obtained from 100s of NH 4 C1 ? 8. Read the experiment wherein you prepared nitrogen. Now, why can you not prepare oxygen from the air by using some substance to combine with the nitrogen ? 9. Measure the laboratory, and calculate its cubic contents. Now, if one litre of air, under standard conditions, weighs 1.2932s, how much nitrogen does the room contain ? How many grammes of ammonia would be produced if the whole of the nitrogen were combined with hydrogen ? 10. Determine approximately the amount of nitrogen in a given volume of air thus : Make a small wooden saucer-shaped boat, and on it place a small pile of fine iron filings which has been moistened with a solution of ammonium chloride. Now float the boat on some water in a convenient vessel, and place down over the whole a tall graduated glass jar. Support the jar so that it may be left standing for a few days. When the water ceases rising in the jar, measure the volume of the residual gas, and make the proper computations. The iron unites with the oxygen, and thus forms a solid. Test the residual gas for nitrogen by means of a burning match. CHAPTER IV. CHLORINE, BROMINE, IODINE, AND FLUORINE, AND THEIR COMPOUNDS WITH HYDROGEN AND OXYGEN. DATA FOR COMPUTATIONS. CHLORINE : Symbol, Cl ; Molecular Formula, Ci, ; Atomic Weight, 35.5 ; Weight of I 1 at C. and 760 mm , 3.173s. BROMINE : Symbol, Br ; Molecular Formula, Br a ; Atomic Weight, 80 ; Specific Gravity ( Water = 1), 3.1872. IODINE : Symbol, I ; Molecular Formula, I 2 ; Atomic Weight, 127 ; Specific Gravity ( Water = 1), 4.048. - FLUORINE : Symbol, F ; Atomic Weight, 19. CHLORINE. 46. Occurrence. Chlorine never occurs free in nature, owing to its intense chemism for other elements. Its com- pounds, however, are plentiful, and occur in large quanti- ties. The most important compound of chlorine is sodium chloride, or common salt, NaCL The chlorides of potas- sium, calcium, and magnesium also occur native, but in much smaller quantities than the sodium compound. 47. Preparation and Properties. EXP. 44. Place a mix- ture of sodium chloride, NaCl, and manganese dioxide, Mn0 2 , in a test-tube, and add a few drops of sulphuric acid. Note the gas which is liberated, and hold in it a strip of moist blue litmus paper. After the color of the paper has disappeared, moisten the strip in ammonia, and note that the color cannot be restored. In fact, the paper is bleached. Also try to bleach a strip of moist unbleached cotton cloth. Ex. Try to obtain chlorine from hydrochloric acid by acting upon it \vith manganese dioxide, MnO 2 . Describe the experiment in detail. 43 44 CHLOBINE. Chlorine is a heavy, greenish yellow gas, possessing remarkably active chemical properties. It was discovered in 1774 by Scheele. It is extensively used for bleaching purposes and in the manufacture of bleaching-powder (Art. 53). It seems that chlorine in the presence of moisture is capable of effecting the following chemical reaction : 2 Cl + H 2 = 2 HC1 + 0. Now the oxygen thus liberated, while in a nascent state or at the instant of its liberation, possesses a stronger chem- ism than when in its ordinary molecular condition ; thus it is enabled to combine with the coloring-matter and destroy it. It may be well to note in this connection that all elements when in a nascent state possess far more active properties than when in their ordinary conditions. Chlorine water finds many useful applications in the laboratory. The best method of preparing a solution of chlorine in water is illus- trated by the following experiment : EXP. 45. In the generat- ing-flask A (Fig. 17) place equal weights of common salt and manganese dioxide which have been pulverized and mixed. To this mixture add twice its weight of dilute sulphuric acid, consisting of equal weights of water and FlG 17 acid. Now apply a gentle heat, when chlorine gas will be given off abundantly. The wash-bottles B and C, which contain simply cold water, will secure the desired solution. CHLORINE. 45 By disconnecting the wash-bottles, and joining instead a long glass tube, the gas may be delivered at the bottom of a tall glass jar, and thus collected by what is termed "Displacement." The reaction which takes place in this experiment is as follows : 2NaCl + Mn0 2 + 3 H 2 S0 4 = 2 NaHS0 4 + MnS0 4 + 2 H 2 0+ 2 Cl. This equation is a typical one, since bromine and iodine may be prepared in the same way by substituting a bro- mide or an iodide for the chloride. In testing for bromine or iodine, chlorine water is used to liberate these elements from their compounds. Chlorine water, as prepared in Exp. 45, will answer for this purpose, but a solution of chlorine may be made more quickly and more conveniently thus : EXP. 46. In a test-tube place a few crystals of potassium chlorate, KC1O 3? and add sufficient hydrochloric acid to cover the crystals half an inch deep. Now warm the contents of the tube until chlorine is escaping freely, when the tube is to be filled nearly full of cold distilled water. The gas is dis- solved by the water. The reaction is : 4 HC1 + 2 KC10 3 = 2 KC1 + 2 H 2 + C1 2 4 + 2 Cl. The compounds KC1 and C1 2 4 are dissolved in the water, as well as the chlorine gas, but they do not impair the efficiency of the solution. Ex. In how many different ways have you prepared chlorine ? Try the effect of an acid upon bleaching-powder. The goods to be bleached are drawn through a tank of weak acid after they have been passed through a solution of the bleaching-powder. Why ? 48. Test for Chlorine. Free chlorine gas may be recog- nized by its odor, color, and its bleaching effects upon organic colors. 46 CHLORINE AND HYDROGEN. CHLORINE AND HYDROGEN; OR, HYDROCHLORIC ACID, HC1. 49. Occurrence, Hydrochloric acid occurs in small quan- tities in volcanic gases. But its compounds, the chlorides, as previously noticed, occur in great quantities. 50. Preparation and Properties. EXP. 47. Place a small quantity of sodium chloride, Nad, in a test-tube, and then add a few drops of sulphuric acid. Note the fumes that are given off when the contents of the tube are gently warmed. The reaction is : NaCl + H 2 S0 4 = NaHS0 4 + HC1. Test the fumes of this acid with a moist blue litmus paper. Will ammonia restore the color? Is hydrochloric acid a bleaching reagent? Hydrochloric acid is an important article of commerce, and it is prepared as a by-product from the same chemicals used in the preceding experiment while treating salt with sulphuric acid in the manufacture of soda ash. EXP. 48. Take three test-tubes, and into the first put a solution of silver nitrate, AgN0 3 ; into the second, a solution of mercurous nitrate, Hg 2 (N0 3 ) 2 ; and into the third, a solution of lead acetate, Pb(C 2 H 3 O2)2. Now to each of these tubes add a few drops of hydrochloric acid. Note the heavy white pre- cipitates which are thrown down in each tube. Hydrochloric acid is used extensively in the laboratory for analytical purposes, as exemplified in the preceding experiment. The lead, silver, and mercury unite with the chlorine of the hydrochloric acid to form the insoluble chlorides of these metals. Now, since these three metals are the only ones that thus form insoluble chlorides, they CHLORINE AND HYDROGEN. 47 may be considered as forming a group which may be re- moved from a solution containing any or all the other metals. From this use of hydrochloric acid it is often spoken of as a group reagent. Again, since most of the compounds formed by hydrochloric acid are soluble in water, this acid is extensively used as a solvent. When three volumes of hydrochloric acid are mixed with one volume of nitric acid, Aqua Regia, or Nitro-Hydro- chloric Acid, the most powerful solvent known, is formed. This compound owes its efficiency to the fact that it fur- nishes large quantities of nascent chlorine to act upon the substance to be dissolved. Only a gentle heat should be employed while using this solvent, otherwise the chlorine will be driven off to waste. It has appeared in the last experiment that hydrochloric acid is a gas. But this gas is soluble in water, one volume of water dissolving 505 volumes of the gas. The acid em- ployed for various purposes is a solution of the gas in water. Sometimes this acid is called by one of its old names, "Muriatic Acid." 51. Test for Hydrochloric Acid. Hydrochloric acid, either free or in any of its combinations, may be detected by add- ing to the solution to be tested a few drops of silver nitrate, AgNO 3 . If hydrochloric acid be present, a white precipi- tate is formed, which is to be divided into two parts. To one part add nitric acid : the precipitate does not dissolve. To the second part add ammonia, and the precipitate will dissolve readily. NOTE. Since the precipitates formed with silver nitrate by the bromides and iodides are liable to be mistaken for that of hydrochloric acid, the student must never report hydrochloric acid from this test without first testing for bromides (Art, 59) and iodides (Art. 64). 48 CHLORINE AND OXYGEN. CHLORINE AND OXYGEN. 52. Chlorine and oxygen unite to form three compounds, viz. : Chlorine monoxide C1 2 0. Chlorine trioxide C1 2 3 . Chlorine tetroxide C1 2 4 . These compounds never occur in nature, and have not been prepared by the direct union of chlorine and oxygen. They are unimportant, and dangerous to prepare, owing to their liability to explode. CHLORINE, OXYGEN, AND HYDROGEN; OR, THE CHLORINE OXACIDS. 53. There are four acids in this series, but none of them are of importance in the arts or in commerce. But they serve well to illustrate some principles in chemical nomen- clature, as will appear in the next chapter. The names and formulae of these acids follow : Hypochlorous acid .... HC10. Chlorous acid HC10 2 . Chloric acid HC10 3 . Perchloric acid HC10 4 . The salts of some of these acids are of importance. Thus, hypochlorous acid unites with calcium to form bleaching-powder. In reality, this useful compound is manufactured by passing chlorine gas into large chambers containing slaked lime, when the following reaction is supposed to take place : 2 Ca(OH) 2 + 4 Cl = 2 H,O + (CaCl s + Ca(C10) 2 ). CHLORINE, OXYGEN, AND HYDROGEN. 49 If this be the correct explanation, bleaching-powder is a mixture of calcium chloride and calcium hypochlorite. Chloric acid forms a class of compounds that are some- what important, the chlorates. Potassium chlorate, the most useful of these compounds, is prepared by passing chlorine gas into a warm concentrated solution of potas- sium hydroxide, thus : 6 Cl + 6 KOH = 5 KC1 + 3 H 2 + KC10 3 . The chlorates are liable to explode when brought in con- tact with any combustible substance, owing to the ease with which they give up oxygen. It is not safe even to grind a chlorate in a mortar with a combustible substance. When such mixtures are to be made, as when making colored fires, the materials must be ground separately, and carefully mixed afterwards on a sheet of paper. Some idea of the behavior of the chlorates may be obtained by the following experiment, which is safe if carefully con- ducted : EXP. 49. Place two small crystals of potassium chlorate in a dry iron mortar. Add a few grains of dry sugar. Now wrap a towel about the hand, and grasp the pestle in the towel. Kub the material in the mortar lightly until a good mixture is made, and then strike the pestle sharply down upon the mixed substances. A sharp explosion will ensue. If sul- phur, gum shellac, or any combustible substance be used in place of the sugar, an explosion will occur. 54. Test for Chloric Acid or the Chlorates. A chlorate, when treated with hydrochloric acid in a test-tube, will yield free chlorine gas (Exp. 46). Further, if a few crys- tals of a chlorate be placed in a test-tube, and sulphuric acid be added, a sharp explosion will follow. 50 BROMINE. NOTE. In making this test, a bit of cloth should be put around the tube, and the cloth is to be taken firmly in a pair of pincers. Thus the tube may be held firmly, and its mouth must not be pointed towards any apparatus or in the direction of any person in the room. BROMINE. 55. Occurrence. Bromine never occurs free in nature. It is chiefly obtained from the mother liquor remaining after removing the crystals of common salt in salt factories. Balard discovered bromine in the year 1826, in sea-water. Bromine is an article of .commerce, but it is by no means a plentiful element. 56. Preparation and Properties. EXP. 50. Place a mix- ture of potassium bromide, KBr, and manganese dioxide, Mn0 2 , in a test-tube, and add a few drops of sulphuric acid. Note the heavy dark-colored fumes given off. Ex. Using the equation under Exp. 45 as a model, and substituting KBr for NaCl, write out the reaction which occurs in this experiment. For the method of preparing bromine water and liquid bromine, see Shepard's Elements, p. 109. Bromine is a dark-colored liquid at ordinary tempera- tures, which always gives off pungent, irritating fumes. It is used to some extent as a disinfectant, but it is not so energetic in its action in this respect as chlorine. Bromine of commerce is prepared by the action of chlo- rine on its compounds. The chlorine is generated in the mother liquor by means of the chemicals employed in Exp. 44. 57. Test for Free Bromine. Free bromine, even in dilute solutions, when shaken in a test-tube with carbon disul- phide, CS 2 , colors the disulphide brownish red. BROMINE, HYDROGEN, AND OXYGEN. 51 BROMINE, HYDROGEN, AND OXYGEN. 58. The compounds of bromine with oxygen and hydro- gen closely resemble those of chlorine. Thus we have Hydrobromic acid HBr. Hypobromous acid .... HBrO. Bromic acid HBr0 3 . Perbromic acid HBrO 4 . None of the oxides of bromine have been prepared. None of these compounds, except hydrobromic acid, are of importance ; and of the compounds formed by them, the bromides corresponding to the acid, HBr, are the only ones much used in the arts. Thus, potassium bromide, KBr, is used in medicine ; silver bromide, AgBr, is used in photography ; while magnesium bromide, MgBra, occurs in some mineral waters. Hydrobromic acid itself is used to some extent in organic analysis. 59. Test for Hydrobromic Acid or the Bromides. Place the solution to be tested in a test-tube, and add a small quantity of chlorine water, to liberate the bromine. Now add a few drops of carbon disulphide, CS 2 , and shake the contents of the tube thoroughly. If the substance tested be hydrobromic acid or any of its compounds, the carbon disulphide will be colored brownish red by the free bromine liberated by means of the chlorine water. IODINE. 60. Occurrence. Iodine never occurs free in nature. It is mostly obtained from sea-water, from which it is taken up by sea-weeds. These weeds are gathered along the 52 IODINE. coasts of some countries, especially Ireland and Scotland, where they have been washed up by storms. The weeds are then dried, and burned in shallow trenches at a low temperature, so that the iodides of sodium, potassium, etc., may not be volatilized. Now these iodides are soluble in water, so they are removed from the "kelp," as the ashes of the plants are popularly called, by solution in water. Plantations of these weeds are cultivated in some parts of the ocean, and at proper times vessels are sent out to gather the weeds. Again, a considerable portion of the iodine that now comes to market is obtained from sodium iodide, Nal, found occurring along with Chili saltpetre. 61. Preparation and Properties. EXP. 51. Place a mix- ture of potassium iodide, KI, and manganese dioxide, Mn0 2 , in a test-tube, and add a small quantity of sulphuric acid. Note the vapors evolved. Ex. Compare this method of preparing iodine with the processes used in obtaining chlorine and bromine, and write the reaction. Commercial iodine is prepared by the method given in the preceding experiment. The materials are placed in iron retorts, and the vapors of iodine are condensed in black, shining crystals upon the sides of suitable condensers. Iodine is much used in medicine, especially in reducing swellings and in checking the spread of eruptive diseases like erysipelas. When thus applied, it is brought into solution by dissolving 20 parts of iodine with 30 parts of potassium iodide in 900 parts of water. 62. Test for Free Iodine. Free iodine colors carbon di- sulphide, CS 2 , violet. IODINE AND ITS COMPOUNDS. 53 IODINE AND ITS COMPOUNDS WITH HYDROGEN AND OXYGEN. 63. The compounds formed by iodine resemble very closely those formed by chlorine and bromine. This will appear by inspecting the formulae of the following com- pounds : Hydriodic acid HI. Iodine pentoxide I 2 5 . lodic acid HI0 3 . Periodic acid HIO 4 . None of these compounds are used excepting hydriodic acid, which has a limited application in analytical work. None of the compounds formed by these substances and the metals are of importance excepting potassium iodide, KI. This is much used in medicine as a sedative. 64. Test for Hydriodic Acid or an Iodide. Add chlorine water to the substance, in order to liberate iodine. Now add to the solution a few drops of carbon disulphide, and shake the contents of the tube thoroughly. If this acid or one of its compounds be present, the disulphide is colored violet. NOTK. The iodides give a precipitate with silver nitrate, which may be mistaken for that of chlorine or bromine. See Art. 61. FLUORINE. 65. Fluorine is a gaseous element which has but recently been prepared. It was obtained by electrolyzing perfectly dry hydrofluoric acid, HF, in platinum tubes. Its chief compound is with calcium, as found in the mineral fluor- spar, CaF 2 . Fluorine forms no compounds with oxygen, 54 EXERCISES. and but one with hydrogen, hydrofluoric acid, HF. This acid possesses the remarkable power of combining with glass. It may be prepared by acting on fluor-spar with sulphuric acid : - CaF 2 + H 2 SO 4 = CaS0 4 + 2 HF. The preparation and behavior of this acid may be shown by the following experiment : EXP. 52. Cover both sides of a sheet of glass with a coating of beeswax. With a sharp, soft point cut through the wax some design or some written characters. Now place some powdered fluor-spar in an evaporating-dish, and then pour on enough sul- phuric acid to cover the fluor-spar. Support the glass a short distance above the dish, and warm the contents of the dish gently. Keep the whole apparatus where the fumes will not escape in the room, and in a short time the design or writing will be etched into the glass. This is best seen when the wax is removed. The fumes of hydrofluoric acid are poisonous, and must not be inhaled. What takes place may be shown by this equation : Si0 2 + 4 HF = 2 H 2 O + SiF 4 . Glass is a compound of sand, SiO 2 , and metals, usually sodium or potassium. The silicon tetrafluoride, SiF 4 , is a gas which escapes as fast as formed : the fumes may be seen during the experiment. The best test for fluorine is the etching test, as shown in the preceding experiment. EXERCISES. (For Review or Advanced Course.) 1. Make a table showing the atomic weights and physical conditions at ordinary temperatures of chlorine, bromine, and iodine. Also make a table showing the formulae of their compounds with hydrogen and oxygen. What similarities and what differences do you find ? EXERCISES. 55 2. Which possesses the stronger chemism, chlorine or bromine ? Chlorine or iodine ? (Sue. See the tests for bromine and iodine.) 3. How many grammes of chlorine may be obtained from 1008 NaCl ? How many litres would this make under standard conditions ? 4. The volume of a given mass of any gas varies according to the tem- perature in the ratio of 273 + t : 273 -f t f , in which t is the given tempera- ture, and t' the required temperature. Now let V be the given volume, and V the required volume, and we have the proportion : F: V : : 273 + t : 273 + t'. By suitable transformations this proportion gives an equation suitable for solving problems concerning gases in which variations of temperature are involved : CD F = ^ 273 + t 273 + t 1 Solve the following problem : PROBLEM. 5 l of chlorine gas at 15 C. become how many litres at 20 C.? 5. The volume of a given mass of gas varies inversely as the pressure or height of the barometer. Letting H be the given height of the barom- eter, and H' the required height, we have this proportion : F: V : : H' : H. This gives the equation (2) VH= VH', an equation useful in solving problems in gases involving variations in pressure. Solve this PROB. 10 1 of oxygen gas under 760 pressure become how many litres under 758 mm ? 6. By combining equations (1) and (2), we have : (3) 273 + t 273 + t' This equation is used when both temperature and pressure vary. Solve this PROB. The barometer reads 755 mm and the thermometer 15 C. when 10 1 of hydrogen gas were generated ; how many litres will this hydrogen become when the pressure is 762 mm and the temperature 18 C.? 7. "What per cent of KBr is bromine ? Potassium ? Give a rule for determining the percentage composition of any chemical compound. 8. How much silver nitrate would be required to precipitate the chlorine 56 EXERCISES. in 108 of sodium chloride ? (Suo. AgNO 3 + NaCl = AgCl + NaNO 3 . By taking the molecular weights of these compounds, we find that 170s of AgN0 3 will precipitate the chlorine in 58.5s of NaCl.) How much AgCl will be produced ? How much NaNO 3 ? 9. WRITING EQUATIONS. It is desirable to know how to write equa- tions. This may be understood from the following explanation : Place the formulae of the known substances, or the substances to be experi- mented upon, in the first member of the equation, and connect them by the sign +. Now determine (by experiment or otherwise) what sub- stances are produced, and write their formulae in the second member, and connect them also by the sign +. If the equation now balances, it is complete. If not balanced, this rule applies : There must be an equal number of atoms of each element in both members of the equation. For example, take the reaction between H 2 SO 4 and KN0 3 . Since these sub- stances are known, we commence the equation thus : H 2 SO i +KNO 3 = Experiment has shown that under certain conditions HN() 3 and K 2 S0 4 are produced. Therefore we place these formulae in the second member, and our equation reads : H 2 SO 4 + KN0 3 = K 2 S0 4 + HN0 3 . By inspection, it appears that the hydrogen atoms do not balance, so we multiply the HNO 3 by 2. Again, the potassium atoms do not balance, so we multiply KNO 3 by 2, and the equation now balances, and reads : H 2 SO 4 + 2 KN0 3 = K 2 SO 4 + 2 HN0 3 . Form equations from these data : 1. When BaCl 2 and K 2 SO 4 react, BaS0 4 and KC1 are produced. 2. When Hg 2 (N0 3 ) 2 and HC1 react, Hg 2 Cl 2 and HN0 3 are produced. CHAPTER V. BINARY COMPOUNDS ; HIGHER COMPOUNDS ; ACIDS, BASES, SALTS ; ACID AND NORMAL, SALTS ; VALENCE ' DETERMI- NATION OF ATOMIC WEIGHTS : CHEMICAL NOMENCLA- TURE ; ETC. 66. Binary Compounds. We have now studied a num- ber of chemical compounds, and it will be profitable to con- sider these substances from a theoretical standpoint before proceeding farther, for the purpose of arranging them in classes and of explaining some of the principles of chemi- cal nomenclature. We have had a number of substances like H 2 O, HC1, HI, HBr, HF, etc., which consist of but two elements com- liined in definite proportions. Now these substances, and all others which consist of but two elements, are called Binary Compounds. The principal elements which form binary compounds are oxygen, sulphur, chlorine, bromine, and iodine. It is a general rule that the names of all binary com- pounds shall end in " ide." Thus the binary compounds containing oxygen are called oxides, while the names sul- phides, chlorides, iodides, etc., readily suggest what element enters into the compound named. Now, since any of the " ide "-forming elements may unite with any of the metals to form an " ide " compound, it is necessary to distinguish between the compounds thus formed. This is done by prefixing the name of the metal 57 58 BINARY COMPOUNDS. to that of the " ide "-forming element. Thus, KC1 is called potassium chloride, NaBr is called sodium bromide, CaF 2 is called calcium fluoride, etc. Sometimes an " ide "-forming element unites in more than one proportion with another element. In such cases the prefixes " mon," " di," " tri," " tetr," " pent," etc., sig- nifying respectively one, two, three, four, five, etc., are prefixed to the name of the " ide "- forming element. Thus we have chlorine monoxide, C1 2 O ; chlorine trioxide, C1 2 O 3 ; etc. The nitrogen oxides also furnish further examples. Ex. Student name the following : CaO ; I 2 O 5 ; SiF^ ; KF ; HBr ; CaS: LiCl: NaBr. There are some of the metals which form two classes of compounds. In such cases the name of the metal is mod- ified by the suifixes " ous " and " ic." Thus we have Hg 2 Cl 2 , mercurous chloride, and HgCL, mercuric chloride. The principal metals forming such distinct classes are mer- cury, iron, copper, tin, and lead. Examples of these will appear further on in their appropriate places. When more than two classes of compounds are formed, other means of distinguishing them are employed. Thus manganese forms the oxides MnO, manganous oxide ; Mn 2 O 3 , manganic oxide : Mn 3 O 4 , manganoso - manganic oxide, i.e. consisting of manganous and manganic oxides ; and MnO 2 , manganese dioxide. Sometimes the relation of 2 to 3 is indicated by the word " sesqui " ; thus, Fe 2 O 3 , sesqui-oxide of iron. But the most recent name for this compound is ferric oxide. It will be noticed that in the cases of iron, copper, tin, lead, and some other metals, the Latin names are used when naming the two classes of salts. Acros. 59 67. Higher Compounds are those containing more than two elements combined in definite proportions. Examples of these are already familiar to the student. 68. Acids, In the preceding pages the word acid has been used many times, and several acids have been pre- pared and tested. It is difficult to give a concise definition of an acid, but in general we may say that it is a hydrogen compound usually having a sour taste and corrosive prop- erties ; it is capable of changing vegetable colors, as in turning blue litmus red ; and it can give up some or all of its hydrogen and take a metal instead. There are both binary and higher acids. The principal binary acids have already been studied. Thus we have had HC1, hydrochloric acid, or hydrogen chloride ; HBr, hydrobromic acid, or hydrogen bromide ; etc. We shall also see that sulphur and some other elements form with hydrogen binary acids. This class of acids is often called the hydrogen acids, or the hydracids, to distinguish them from the higher acids, which contain oxygen. We have also had experience with a goodly number of the higher, or better, the oxygen acids. Thus, HNOg, nitric acid; HC1O 3 , chloric acid; HBrOg, bromic acid; etc. In naming these acids, it is a rule that the most common, the most important, or the one first discovered, shall have a name ending in " ic," and that this suffix shall be joined to the name of the acid-forming element, thus : Nitric acid, Chloric acid, HC10 3 , Sulphuric acid, H 2 S0 4 , etc. The acid having one less atom of oxygen than the " ic " acid has " ous " prefixed to the name of the acid-forming 60 BASES. SALTS. element ; the acid with one less atom of oxygen than the " ous " acid is called the " hypo-ous " acid ; while that with one atom of oxygen more than the " ic " acid is called the " per-ic " acid. All this will become apparent by an exam- ination of the formulae of the chlorine oxacids. When more acids than those just enumerated appear in a series, other means of naming them are employed, as will become apparent in the sulphur oxacids. 69. Bases. The word base is used differently by differ- ent chemists. Some define a base as being any substance that will unite with an acid, to remove part or all of the hydrogen of that acid, and to form a substance called a salt. This is a sweeping definition, and would include at least three different classes of substances, viz. : (1) the metals ; (2) the metallic oxides ; (3) the hydroxides, which are compounds of the metals and the radical hydroxyl, OH. As examples of the hydroxides, we may mention potassium hydroxide, KOH ; sodium hydroxide, NaOH ; calcium hydroxide, Ca(OH) 2 ; barium hydroxide, Ba(OH) 2 ; etc. Many chemists apply the word base to the hydroxides only. 70. Salts. When an acid and a base react, the acid parts with all or a part of its hydrogen, and forms a compound called a salt. Thus, when a metal like zinc reacts with hydrochloric acid, the hydrogen of the acid is set free, and the salt, zinc chloride, is produced thus : Zn + 2 HC1 = ZnCl 2 + 2 H. This is generally true of acids and metals, with a few exceptions. Nitric acid forms an important exception, since under ordinary conditions, while salts called nitrates are formed, no hydrogen is liberated, but, instead, water, NORMAL, ACID, AND BASIC SALTS. 61 H 2 O, and nitrogen dioxide, NO, are produced. The follow- ing equation is a typical one for nitric acid and a metal : 3 Cu + 8 HN0 3 = 3 Cu(N0 3 ) 2 + 4 H 2 O + 2 NO. When an oxide and an acid react, a salt and water are produced, thus : BaO + H 2 S0 4 = BaS0 4 + H 2 O. When the reaction is between a hydroxide and an acid, a salt and water are also formed : - KOH + HC1 = KC1 + H 2 0. Thus it appears that a fair definition of a salt would be : A salt is an acid in which all or a part of its hydrogen has been replaced by a metal. 71. Normal, Acid, and Basic Salts. When all of the hydrogen of an acid has been replaced by a metal, a normal salt is obtained ; thus, K 2 SO 4 , potassium sulphate, is a normal salt. When only a part of the hydrogen has thus been replaced, an acid salt is produced ; thus, HKSO 4 , acid potassium sulphate, is an acid salt. An oxide or a hydroxide of a metal may unite with a normal salt to form a basic salt. Thus : In this case basic mercuric sulphate is formed. Again : Pb(N0 3 ) 2 + Pb(OH) 2 = 2 PbOHN0 3 . Water may also produce a basic salt thus : Bi(N0 3 ) 3 + 2 H 2 = Bi(OH)2N0 3 + 2 HN0 3 . We will now explain how the salts derived from the different acids are named. In the case of the salts from the binary acids what has been said under binary com- 62 VALENCE. pounds will apply, and no further explanation is neces- sary. But when we come to the salts from the oxacids, further explanation is necessary. It is a rule that when the name of the oxacid ends in u ic," the name of the salt shall end in " ate " ; and when the acid ends in " ous," the salt shall end in " ite." This will be understood by examining the potassium salts of the chlorine oxacids, as follows : Hypochlorous acid, HC10, forms potassium hypochlorite,KC10. Chlorous acid, HC10 2 , forms potassium chlorite, KC10 2 . Chloric acid, HC10 3 , forms potassium chlorate, KC10 3 . Perchloric acid, HC10 4 , forms potassium perchlorate, KC10 4 . In naming the acid salts it is best to indicate the number of atoms of the metal present by the usual prefixes. Thus, sodium and phosphoric acid form two acid salts, NaH 2 PO 4 , monosodium phosphate, and Na 2 HPO 4 , disodium phosphate. The normal salt is called simply sodium phosphate, Na 3 PO 4 . 72. Valence. Let us examine the following f ormulse : HC1 ; H 2 O ; H 3 N ; H 4 C. Now these actually represent com- pounds, and in them we see that chlorine, oxygen, nitrogen, and carbon differ in the number of hydrogen atoms that each holds in combination. This is explained by saying that each of the elements named has a different valence. In order to measure the valence of an element, we may take a simple atom like the hydrogen atom. Let this be the standard, and it follows that chlorine is univaleiit, oxygen is bivalent, nitrogen is trivalent, and carbon is tetravalent. If we wish to measure the valence of an ele- ment that does not unite with hydrogen, we may take some other univalent element, like chlorine, which does unite with the element in question. SUBSTITUTING POWER AND VALENCE. 63 It must not be inferred that valence is an unvarying property, since many elements appear to have different valences in different compounds. Thus, in HC1 chlorine is univalent, while in HC1O 3 it is pentavalent. Likewise, phosphorus in PC1 3 is trivalent, while in PC1 5 it is pentav- alent. The most common valences of the elements are indicated in the table, Art. 10, by small Roman numerals or by indices written to the right and above the symbol. Usually the symbols are written without these. 73. Substituting Power and Valence. We have already noticed how the hydrogen of an acid is replaced by a metal to form a salt. This replacement takes place according to fixed laws, depending upon the valence of the metal. Thus a univalent metal will replace one atom of hydrogen, a bivalent metal will replace two atoms of hydrogen, etc. If the acid molecule does not contain a sufficient number of hydrogen atoms to equal the valence of the metal, the acid must be multiplied by some figure to make them equal. Thus, Ca" is bivalent ; when it unites with HNO 3 , the acid must be multiplied by 2 in order to satisfy the require- ments of the bivalent calcium. Ca(NO 3 ) 2 is produced. Other cases arise, but they will offer no difficulty. 74. Determination of Atomic Weights by Avogadro's Hypoth- esis. Elements that form compounds that are gases or may be converted into gases may have their atomic weights determined by means of Avogadro's hypothesis. First the molecular weight of each available compound of that ele- ment is ascertained. Then each compound is analyzed, and the proportions noted in which its constituents com- bine. Then the smallest number which occurs in any of the compounds analyzed is taken as the atomic weight. 64 EXERCISES. EXERCISES. (For Review or Advanced Course.) 1. If to the number which represents the valence of an element we assign a positive or negative sign, the sum of these numbers in any stable chemical compound will always equal 0, provided we let H = + 1, O = 2 ; and the metals are to be assigned + indices, except such as form binary compounds with hydrogen. These data may be utilized to determine the valence of an element in any compound ; e.g. What is the valence of Cl in HC1O 4 ? Now H = + 1 and O 4 8. What is needed to add to the + 1 to make a number suf- ficiently great so that when it is added to a 8, the sum shall be ? That number is evidently -f 7, which equals the valence of Cl in this particular compound. Ex. Determine the valence of chlorine in all its oxacids. 2. Many chemists prefer to write what are called molecular equations. Most of those already given are what might be termed atomic equations, since they are supposed to indicate what takes place when the elements of a molecule are torn apart and thus brought into the atomic or nascent state. But atoms probably do not remain in this state, but immediately seek out other atoms with which they may unite to form new molecules. When a simple gas like hydrogen or oxygen is liberated, the hydrogen atoms unite to form hydrogen molecules ; thus, H + H = H 2 . So, like- wise, with oxygen or any element. Molecular equations, then, represent what has taken place after this re- arrangement is effected. In writing mo- lecular equations it is only necessary to have each free gaseous element appear as a molecule ; thus K + H 2 O = KOH + H is written 2 K + 2 H 2 O = 2 KOH + Hj. Ex. Rewrite in molecular equations all suitable atomic equations previously given. Read Meyer's Modern Theories of Chemistry, pp. 195-204. CHAPTER VI. CARBON AND SOME OF ITS COMPOUNDS WITH HYDROGEN, OXYGEN, AND NITROGEN. CARBON. DATA FOR COMPUTATIONS. Symbol, C ; Atomic Weight, 12 ; Specific Gravity: Diamond, 3.5 to 3.6; Graphite, 2.25; Charcoal, 1.57. 75. Occurrence. Carbon occurs widely distributed. In the free condition it is found in transparent crystals as Diamonds, and in opaque, six-sided slabs as Graphite. In impure forms it constitutes the greater portion of Coal, Soot, and Lampblack. But the largest quantities of carbon are found combined with hydrogen, oxygen, nitrogen, and a few other elements, in plants, and in all living structures. Again, large quantities of carbon occur in the carbonates and in carbon dioxide. 76. Preparation and Properties. EXP. 53. Ignite a match, and hold in the flame a bit of cold glass. What is deposited on the glass ? Extinguish the match, and dip the glowing coal in water. What kinds of carbon have you thus prepared ? Where is soot deposited ? Lampblack is prepared on the large scale by burning resins or oils in a limited supply of air. The lampblack is collected on suitable condensers. Charcoal is made by burning wood in a limited supply of air in coal kilns, or by distilling wood in large closed retorts. When distil- 65 66 CARBON. lation is used, valuable products, such as tar and acetic acid, are obtained by condensing the vapors. EXP. 54. Color about 50 CC of water with any organic color, such as cochineal or litmus solution. Place in a generating- flask some freshly burned charcoal which has been finely pul- verized, or, better, some good boneblack, and then add about half of the colored solution. Shake the contents of the flask for some time, and then filter. Compare the color of the fil- trate with that of the solution which was not treated. What change do you notice ? FIG. 18. Charcoal is very porous, and it has a wonderful power of absorbing gases. Its pores therefore contain much atmos- pheric oxygen. Now when certain vegetable or animal substances are brought in contact with this oxygen, they are oxidized and thus destroyed. This property of char- coal is largely utilized in refining sugar, in making water- filters, and for disinfecting purposes. Charcoal made from blood is best for these uses, but sugar-refiners mostly use Boneblack, which is made by charring bones. Charcoal from wood is principally used in water-filters. Wood charcoal is prepared by burning wood in charcoal kilns (Fig. 18). CARBON. 67 Ex. Why should a water- filter be cleaned and renewed frequently, and why often allowed to run dry ? How can you obtain carbon from kero- sene oil ? From illuminating-gas ? What makes a lamp smoke ? For what purposes is charcoal used in the arts ? Stone Coal is the remains of a magnificent vegetation which flourished during the carboniferous age and some of the periods following. Heat and pressure are the prob- able agents which converted this vegetation into stone coal. When the heat and pressure were great, Anthracite, or " hard " coal, was produced ; and when these agencies were less intense, Bituminous, or " soft " coal, was formed. Lignite is a soft coal of more recent origin, being derived from deciduous trees similar to those now living. Peat and Turf consist largely of the roots and stems of low-growing herbs such as grasses and weeds. Ex. For what purposes are the different kinds of coal employed ? Where is peat largely used ? Grraphite, also known as "plumbago" and "black lead," has been artificially produced in insignificant quantities in iron furnaces. But it occurs native quite plentifully in many localities. It is largely used for making lead-pencils and crucibles. For these purposes it is mixed with clay. Graphite is also used for polishing purposes, in coating powder and shot, in electrotyping, and in the manufacture of stove-blacking. G-as Carbon is found in the retorts used for distilling coal in the manufacture of illuminating-gas. This form of carbon is much employed in making plates for galvanic- batteries and for making carbon pencils for electric lamps. Diamonds are found in Africa, India, South America, and in some of the United States. They occur in earthy detritus or in clayey shales : the method of their formation is not understood. 68 CAEBON. The primary form of the diamond crystal is octahedral (Fig. 19), but it occurs also in many other forms derived from this primary form. Diamonds vary in color from the pure, limpid variety to the black diamond, or Carbonado. The colorless diamond is highly prized as a jewel, while the yellowish variety is less esteemed. Blue and green diamonds are beautiful and rare, and consequently high in price. The diamond is insoluble in acids and in alkalies; it refracts light strongly, whence arises its brilliancy; it is FIG. 19. Crystals of Diamond. the hardest substance known and does not tarnish under any circumstances, and it is to these properties that it owes its value as a jewel. At high temperatures the diamond will burn in an atmosphere of oxygen, forming carbon dioxide, CO 2 , and leaving a small amount of ash ; in fact, it is almost pure carbon. Low-grade diamonds are used for cutting glass and for writing on glass. Diamond dust is used in polishing hard and refractory substances, including the rough diamond itself. Black diamonds are extensively used for drill- points. Equipped with these drills, the miner bores CARBON. 69 through the hardest rock with ease ; and thus he is enabled to explore the earth to a depth of thousands of feet while searching for its hidden treasure. EXP. 55. Heat a few grains of sugar in an iron spoon or on a bit of porcelain. Do you obtain carbon ? Thus try starch, beeswax, paraffin, tallow, and gum arabic. If the substance burns with a flame, hold a cold piece of metal or glass in the flame. Are all these carbon compounds ? In this way it may be shown that all substances of veg- etable and animal origin are compounds of carbon. In short, so great is the number of these compounds that they are usually treated under a separate heading or in a book devoted exclusively to them. This branch of Chemistry is called The Chemistry of the Carbon Compounds, or Organic Chemistry. 77. Tests for Carbon. Free carbon is readily recognized in any of its forms by its physical properties. CARBON AND HYDROGEN. 78. Carbon and hydrogen unite to form a multitude of compounds. In this chapter we shall note but three of these compounds, reserving further notice to a succeeding chapter. The names and formulae of the three to be con- sidered here are : Methane, or marsh gas .... CH 4 . Ethylene, or olefiant gas . . . C 2 H 4 . Acetylene C 2 H2. METHANE, CH 4 . 79. Preparation and Properties. EXP. 55. Mix 2 g sodium acetate, NaC 2 H 3 2 , which has been thoroughly dried, with 8 g 70 CARBON AND HYDROGEN. sodium hydroxide, NaOH, and 2 g finely powdered quicklime, CaO. Fit a jet delivery-tube to a hard glass test-tube ; place the mixture in the test-tube, and heat the contents in the Bunsen flame. When the gas issues freely, hold moistened strips of red and blue litmus paper in it, and finally ignite it. The reaction is NaC 2 H 3 2 + NaOH = ]S T a 2 C0 3 + CH 4 . Ex. Is methane an acid ? An alkali ? Is it inflammable ? Deliver a small quantity of the gas in a large test-tube, and mix it thoroughly with air ; apply a match to the mouth of the tube. Is methane explosive ? Methane occurs in nature very plentifully, especially in connection with coal and in the oil regions. Natural G-as, which has lately risen to such a degree of usefulness, consists largely of methane. In coal mines it forms the miner's dreaded "fire damp," which is respon- sible for the numerous mine explosions that frequently occur. Methane also occurs in marshy places and in stagnant pools, being produced by the decay of organic substances. From this fact it derived the name Marsh Gas. Methane is neither an acid nor an alkali ; but as we shall see further on, it is important, in that it is the lowest member of a series of hydro- carbon compounds, many of which are of the greatest utility. Methane is not readily acted on by reagents > hence it affords no common test other than the color of its bluish yellow, non-luminous flame, taken together with its explosive properties. FIG. 20. Ex. Write a short sketch of Sir Humphry Davy, who invented the miner's safety-lamp (Fig. 20.) CARBON AND HYDROGEN. 71 ETHYLENE, OR OLEFIANT GAS, C 2 H 4 . 80. Ethylene is formed by the destructive distillation of coal ; consequently it always forms a valuable constituent of coal gas. EXP. 56. Place 10 g ethyl alcohol, C 2 H 6 0, in a generating- flask which has been provided with a jet delivery-tube ; add 50 g sulphuric acid ; heat gently, and note the gas which escapes. Finally ignite the jet, and note the flame, which is the same as the ordinary luminous gas-flame. The sulphuric acid simply deprives the alcohol of one molecule of water : C 2 HO - H 2 = Oft. EXP. 57. Nearly fill the bowl of a common clay pipe with powdered bituminous coal, and then close the mouth of the bowl by a covering of wet clay. Now dry the clay, and heat the bowl of the pipe in the Bunsen flame, and ignite the gas escaping from the stem of the pipe. It is Illuminating-Gas. When the gas is all driven out, examine the contents of the bowl. Coke remains. Illuminating-gas is a mixture of hydrogen, methane, ethylene, carbon monoxide, CO, and small quantities of various other gases. One of the by-products formed in distilling coal is Coal Tar. From this remarkable sub- stance many useful products have been obtained, among which are many beautiful dyes. 81. Test for Ethylene. If through a jar of ethylene chlorine gas be passed, a heavy oily liquid, ethylene chloride, C 2 H 4 C1 2 , often called "Dutch liquid," will be formed ; the odor of this substance resembles that of chloroform. 72 CARBON AND OXYGEN. ACETYLENE, C 2 H 2 . 82. Acetylene is also a gas possessing a disagreeable odor. It is formed when an ordinary Bunsen burner strikes back and burns at the base. This gas is remarka- ble, since it is the only compound of hydrogen and carbon that has been prepared by the direct union of these ele- ments. The method of its synthesis is extremely simple : powerful electric sparks are passed between carbon termi- nals in an atmosphere of hydrogen. The odor of acetylene betrays its presence. CARBON AND OXYGEN. 83. Two oxides of carbon are known : Carbon Monoxide, CO ; Carbon Dioxide, C0 2 . Of these gases, the latter is the most important. The monoxide is formed when carbon is burned in a limited supply of air : - C + = CO. This is an inflammable, poisonous gas burning with a blu- ish flame, as seen in the flickering flames above the burning coal in coal stoves and grates. When carbon monoxide burns, it is oxidized to the dioxide thus : CO + = C0 2 . CARBON DIOXIDE, CO 2 . 84. Occurrence. This important gas, often called car- bonic acid gas, occurs very plentifully in nature. It occurs free in the atmosphere in small but almost unvary- ing proportions, and it is from this source that plants ob- tain nearly all their supply of carbon. Limestone, CaCO 3 , CABBON AND OXYGEN. 73 and other mineral carbonates form a large proportion of the earth's crust. Shells and many coral formations are almost pure limestone. 85. Preparation and Properties. EXP. 58. Place a small quantity of calcium hydroxide solution in a small beaker. Using a glass tube, force the breath through this solution. Note the white precipitate formed : Ca(OH) 2 + C0 2 = CaC0 3 + H 2 0. The carbon dioxide comes from the breath. Continue to pass the breath through the solution, and the precipitate dissolves. Carbon dioxide is one of the waste products of the body. Every air-breathing animal exhales this gas at every breath. EXP. 59. Place a burning taper in a wide-mouthed bottle, and cork the bottle loosely. When the taper is extinguished, remove it, and pour into the bottle a little calcium hydroxide solution. Shake thoroughly. Do you obtain a white precipi- tate ? Is carbon dioxide present ? Whence came it ? What equation applies ? Every carbon-bearing compound when burned in the air produces carbon dioxide. Volcanoes also send out large volumes of this gas. EXP. 60. Make a dilute solution of sugar, and add a little baker's yeast. Fill a test-tube with this solution ; also place a small quantity of the same in an evaporating-dish. Invert the test-tube, and place its mouth below the solution in the dish, and allow the whole to stand in a warm place. Fermen- tation soon sets in ; bubbles of gas rise and fill the tube. Turn this gas out into a clean test-tube, pouring the gas as if it were a liquid, and then test the contents of the second tube for carbon dioxide. 74 CARBON AND OXYGEN. During fermentation and in the natural decomposition of all organic substances, carbon dioxide is liberated. The atmosphere contains by volume from 2.7 to 3.5 parts of carbon dioxide in 10,000. Ex. In what ways is carbon dioxide liberated in a living-room ? In the atmosphere ? Water containing carbon dioxide in solution can dis- solve limestone ; explain the disappearance of the precipitate formed in Exp. 58. EXP. 61. Place about 10 g of coarsely pulverized limestone or marble, CaC0 3 , in a generating-flask, fitted with a V-shaped delivery-tube. Cover the limestone with dilute hydrochloric acid, and warm gently if necessary. The following reaction occurs : CaC0 3 + 2 HC1 = CaCl 2 + H 2 + C0 2 . The gas may be collected by delivering it at the bottom of any deep and narrow vessel, or it may be stored in gas-bags. EXP. 62. Fill a wide test-tube with carbon dioxide, and then lower into it a burning taper. What occurs ? EXP. 63. Place a mouse in a jar of carbon dioxide. Note the rapidly fatal effects of the gas. EXP. 64. Attach a common clay pipe to the uozzle of a gas-bag filled with carbon dioxide. Dip the bowl of the pipe in a soap-bubble solution, and allow the gas to escape, forming a bubble. Shake the bubble loose. Does it rise or fall ? Is carbon dioxide heavier or lighter than air ? EXP. 65. Place the tip of the delivery-tube into the bottom of a test-tube filled with cold water. Allow the gas to bubble up through the water for some time. Test the water as fol- lows : (1) Taste it. Is it acid ? Also test it with blue litmus paper. (2) To a portion of the water add calcium hydrox- ide solution. Did the water dissolve any carbon dioxide? (3) Boil the remainder of the water, and test as before. What effect does boiling have upon solutions of carbon dioxide in water ? CARBON AND OXYGEN. 75 When large supplies of carbon dioxide are required, they are obtained by acting on some of the metallic carbon- ates by means of an acid. Thus soda-water fountains are charged by treating powdered marble with sulphuric acid. In baking-powders carbon dioxide is liberated by the reac- tion between sodium carbonate and cream of tartar, or acid potassium tartrate, KHC 4 H 4 O 6 . Sometimes alum is inju- riously employed instead of the cream of tartar. Carbon dioxide is heavier than air, having a specific gravity of 1.529, while one litre weighs 1.965 g . In conse- quence of its high specific gravity, it collects in wells, caves, and mines , and many persons lose their lives by going down into places filled with this gas. It seems to produce its fatal effects by suffocation. Carbon dioxide is a very stable compound, but its separa- tion can be effected by the method shown in -the following experiment : EXP. 66. Hold a piece of burning magnesium ribbon in a jar of carbon dioxide. Is carbon liberated? Since we have a series of salts, the carbonates, the exist- ence of a corresponding acid would be suggested. Thus if we regard carbon dioxide as the anhydride of that acid, we have : C 2 + H 2 = H 2 C0 3 . And we might suppose that the metals unite with this acid to form the carbonates. Again, a solution of carbon diox- ide in water has a weak acid reaction to test paper. But notwithstanding all these facts, carbonic acid has not been prepared in a pure, concentrated state. 86. Tests for Carbon Dioxide and the Carbonates, 1. If the free gas he led through a solution of calcium hydroxide, Ca(OH) 2 , a white precipitate of calcium carbonate is formed. 76 CARBON AND OXYGEN. 2. If the free gas be in a water solution, it may be placed in a geiieratiiig-flask fitted with a delivery-tube, and boiled out and passed through calcium hydroxide as before. 3. Any of the mineral carbonates will effervesce with hydrochloric acid, yielding' free carbon dioxide which may be generated in a flask and tested as in 1. CYANOGEN, CN OR Cy. 87, But one compound of carbon and nitrogen has been prepared, and that is the gas, Cyanogen. When mercuric cyanide, Hg(CN) 2 , is heated, cyanogen is liberated; but the gas is too poisonous for the beginner to prepare. HYDROCYANIC OR PRUSSIC ACID, HCN. 88. Prussic acid is one of the most deadly poisons known. It occurs in minute quantities. It can be prepared by treat- ing mercuric cyanide, Hg(CN) 2 with hydrogen sulphide, H 2 S, thus : Hg(CN) 2 + H 2 S = HgS + 2 HCN. The acid has a faint and peculiar odor resembling peach blossoms. The beginner may omit its preparation. An important class of compounds may be regarded as derived from this acid. These are the cyanides, among which is the well-known potassium cyanide, KCN, which is used in silver electroplating and as an insecticide. 89 Test for the Cyanides. The cyanides always emit a peculiar odor resembling that of the acid. But in case of doubt a good test follows : Add to the solution potassium hydroxide, KOH, and then add ferrous sulphate, FeSO 4 . Now shake thoroughly and acidulate the contents of the tube with hydrochloric acid. If a cyanide be present, a deep blue precipitate (Prussian blue) will be formed. EXERCIS EXERCISES. (For Review or Advanced Course.) 1. Test as many different kinds of shells as you can find for carbonates. Also test several specimens of rocks for carbonates. Usually it will be sufficient to add hydrochloric acid, HC1, and note the effervescence, with- out passing the gas through lime-water. 2. Read in some text on Geology a description of the carboniferous age. 3. Read all the authorities at hand on the topic of ventilation. 4. Procure a stoppered bell- jar, or a large bottle from which the bottom has been evenly cut off and ground so that it will set on a board or on the desk nearly air-tight. Let this represent a school- room. Now let a lighted taper represent the pupils sitting hi the room. Make the following exper- iments, and show what principles they illustrate in ventilation : (a) Place the bell-jar on the desk, and insert the stopper. This now represents a room with no ventilation. Remove the stopper, insert the lighted taper, and then return the stopper. You now have a representa- tion of a room with no ventilation, and with the pupils sitting in it. What occurs ? What lesson does this teach ? (6) Most country school-houses have a hole in the ceiling for a venti- lator. The jar sitting on the desk, with the stopper removed, will repre- sent such a room. Let the air in the jar be pure, and insert the burning taper, leaving out the stopper. This arrangement represents such a room with the pupils sitting in it. What occurs, and what lesson is taught ? (c) Now put the stopper hi place, and let one edge of the jar project slightly over the edge of the desk. This represents a room with a venti- lating opening at the bottom. Insert the burning taper when the jar is so placed. What occurs, and what is the deduction therefrom ? (d) Now leave the stopper out, and let the edge of the jar project as before. We now have two openings for ventilation. Insert the lighted taper, and note the results. WTiat is the course taken by the air ? What is the course of the circulation in the other arrangements ? What lesson have you learned ? 5. What weight of CO 2 can you obtain from 100* of CaCO 3 ? How many litres would this be under standard conditions? At 14 C. and 758 mm , how many litres ? 6. How could you test a well for CO 2 ? If one man loses his life in a well containing choke damp, why does another person almost invariably lose his life in the same well also ? What ought always to be done before venturing into a well ? 78 EXERCISES. 7. Hold a piece of fine wire gauze down over the Bunseii flame, Fig. 22. Explain what takes place. 8. Explain the action of the miner's safety-lamp, Fig. 20. 9. Generate some sulphuretted hydrogen (Art, 95), and pass the gas ;hrough a test-tube of cold water. Place the solution thus formed in a FIG. 21. FIG. 22. flask. Add some powdered charcoal, and shake. Has the odor disap- peared ? Explain. 10. What substances are produced during the combustion of hydro- carbon compounds ? 11. Fill a tumbler or beaker-glass with carbon dioxide, and then pour the gas into a similar vessel containing a lighted taper (Fig. 21). Explain what occurs. CHAPTER VII. SULPHUR, SELENIUM, AND TELLURIUM, AND THEIR COMPOUNDS. SULPHUR. DATA FOR COMPUTATIONS. Symbol, S ; Atomic Weight, 32 ; Specific Gravity (crystals), 2.05; Melting- Point, 115 O.; Boiling-Poiut, 447 C. 90. Occurrence. Sulphur occurs native in volcanic regions. Its compounds are also widely distributed. Iron pyrites, FeS 2 , or fool's gold ; galena, PbS ; cinnabar, HgS ; gypsum, CaSO 4 -f 2 H 2 O, and heavy spar, BaSO 4 , are among the most plentiful compounds. 91. Preparation and Properties. Native sulphur is read- ily separated from its impurities by fusion. It is afterward distilled, and the vapors are conducted into suitable con- densing chambers. If the chamber be cold, flowers of sul- phur are obtained. If the temperature of the chamber is at about the melting-point of sulphur, it is obtained as a liquid which is drawn off and cast into sticks known as roll sulphur or brimstone. But the greater part of the sul- phur used in the arts is simply the crude product obtained by fusion. EXP. 67. Dissolve 1 slaked lime in 13 of water. Add 2 g flowers of sulphur, and boil. Now filter the solution, and acidify with hydrochloric acid. A white precipitate of finely divided sulphur is obtained. At first calcium pentasulphide, 79 80 SULPHUR. CaS 5 , is obtained ; "this is decomposed by the acid which is finally added. Write the equation. The product obtained in the preceding experiment is the lac sulphuris, or milk of sulphur, of the Pharmacopoeia. It is used in medicine. EXP. 68. Place a small quantity of flowers of sulphur in a test-tube, and add carbon disulphide, CS 2 ; close the tube with the thumb, and shake till the sulphur is dissolved^ Now pour the solution into a small beaker, and allow it to evaporate in the air without heat. Note the sulphur crystals obtained. FIG. 23. The primary form of the sulphur crystal is the octahe- dron (Fig. 23). But in all there are no less than thirty different forms derived from the primary crystal. EXP. 69. Melt sulphur in a test-tube, and then heat until it becomes black and fluid. Now turn the molten mass into cold water (Fig. 24). Examine the product. This experiment furnishes plastic sulphur, which strongly resembles caoutchouc. When rubber gum is heated with sulphur at moderate temperatures, a better material for some purposes is obtained than the pure gum SULPHITE AND HYDKOGEN. 81 itself. When higher temperatures are employed, vulcanite or ebonite is obtained. Large quantities of sulphur are thus consumed. EXP. 70. Heat a pine splinter, and dip it in flowers of sulphur. Now ignite, and note the fumes, S0 2 . Sulphur is largely employed in making matches, in bleaching straw goods and hops, in preparing sulphuric acid, and in the manufacture of gun-powder. 92. Tests for Free Sulphur. Free sulphur can be recog- nized by its physical properties and by its fumes when ignited. SULPHUR AND HYDROGEN. 93. Sulphur and hydrogen form two compounds : Hydrogen sulphide, H 2 S. Hydrogen persulphide, H 2 S 2 (?). Of these compounds, the first is the more important. The second has no industrial use. HYDROGEN SULPHIDE, H^. 94. Occurrence. This substance is a gas commonly called Sulphuretted Hydrogen. It occurs in large quanti- ties, both free and combined. It is sulphuretted hydrogen that gives the offensive odor to many " sulphur springs " and mineral waters ; it is a product of volcanic action, and of the decomposition of albuminous substances, as noticed in the odor of rotten eggs. It is produced periodically in some surface wells by the action of organic substances, such as wooden curbing and wooden pumps, on iron pyrites in the presence of mineral ingredients dissolved in the waters of the wells. 82 STTLPHTJK AND OXYGEN. 95. Preparation and Properties. EXP. 71. Place two or three small pieces of ferrous sulphide, FeS, in a generating- flask fitted with a V-shaped delivery-tube. Cover the lumps with water, and then add a few drops of sulphuric acid. Insert the delivery-tube, and the apparatus is now ready for use. The reaction is : FeS + H 2 S0 4 = FeS0 4 + H 2 S. Note the odor of the gas, and finally ignite it. Extinguish the flame, and allow the gas to bubble up through a solution of copper sulphate, CuS0 4 , in a test-tube. Note the precipitate formed. Thus pass the gas through a solution of lead acetate, Pb(C 2 H 3 2 ) 2 . Hydrogen sulphide forms a series of salts, the sulphides. As in the case of hydrochloric acid, this acid is also much used in analytical work as a group reagent. In such work, it is prepared precisely as in the preceding experiment. 96. Tests for Hydrogen Sulphide, Free or Combined. 1. The free gas may be detected by its odor and by its blackening a strip of paper moistened with lead acetate, Pb(C 2 H 3 2 ) 2 . 2. A sulphide is tested thus : Pulverize the substance to be tested, mix it with sodium carbonate, Na 2 CO 3 , on a bit of porcelain or platinum foil, and fuse it in the Bunsen flame. Place the fused mass on a clean silver coin and add a drop of water. If a sulphide be present, a black spot will appear on the silver. SULPHUR AND OXYGEN. 97. We shall notice two oxides of sulphur : Sulphur dioxide, S0 2 . Sulphur trioxide, S0 3 . SULPHUR AND OXYGEN. 83 Both these oxides are important from a chemical point of view, since they are respectively the anhydrides of sulphu- rous acid, H 2 SO 3 , and sulphuric acid, H 2 SO 4 . They unite with water thus : SO 2 + H 2 = H 2 SO 3 ; and SO 3 + H 2 O = HO<. The trioxide is prepared by passing a mixed stream of sul- phur dioxide and oxygen over finely divided platinum in a highly heated porcelain tube. The dioxide deserves a more extended notice. SULPHUR DIOXIDE, SO 2 . 98. Preparation and Properties. EXP. 72. Place a small quantity of powdered galena, PbS, in a hard glass tube open at both ends, and heat strongly in the Bunsen flame. Note the gas escaping from the tube. EXP. 73. Place some fine copper filings in a test-tube, and cover with strong sulphuric acid. Heat gently, and note the escaping gas. Hold a piece of moist wheat straw in the vapors. Also try the effect upon bits of unbleached silk or woollen yarn. What occurs ? The copper and acid react thus : Cu + 2 H 2 S0 4 = CuS0 4 + 2 H 2 + SO* Sulphur dioxide occurs free in volcanic gases. It finds many useful applications in the arts, and is manufactured in enormous quantities. For bleaching purposes it is pre- pared by burning sulphur in the air. In sulphuric acid manufacture it is prepared in the same way, and also by roasting iron pyrites or some other sulphide. Of late this gas is used in manufacturing paper from wood by the sul- phite process. For this purpose, the gas is run into tanks of lime-water or calcium hydroxide solution. The liquor thus prepared is used for reducing the chipped wood to paper pulp. 84 THE SULPHUR OX ACIDS. 99, Test for Sulphur Dioxide. Free sulphur dioxide may be recognized by its odor, which is well known, resembling that of burning matches. THE SULPHUR OXACID3. 100, There are eight acids in this series, as shown in the following list : Hyposulphurous acid .... H 2 S0 2 . Sulphurous acid H 2 S0 3 . Sulphuric acid H 2 S0 4 . Thiosulphuric acid H 2 S 2 3 . Dithionic acid H 2 S 2 6 . Trithionic acid H 2 S 3 6 . Tetrathionic acid H 2 S 4 O 6 . Pentathionic acid H 2 S 5 6 . Of these acids, but three are of importance to the beginner, sulphurous, sulphuric, and thiosulphuric acids. The last has not been prepared, but its salts are used for some purposes, as in photography. Only the test for this acid will be given. By inspection it will be seen that in this series of acids each contains two atoms of hydrogen. One or both of these atoms is replaceable by a metal ; thus each of these acids may give rise to acid or normal salts. For example, we have acid or monosodium sulphate, NaHSO 4 , or sodium sulphate, Na 2 SO 4 . When an acid has one replaceable hydrogen atom, it is called a monobasic acid ; when it has two, it is called diba- sic, ; three, tribasic ; and with four, it is tetrabasic. We have had examples of the first two; and illustrations of the others will appear further on. THE SULPHUR OXACIDS. 85 SULPHUROUS Aero, 101. Preparation and Properties. EXP. 74. Pass sulphur dioxide gas (Exp. 73) into a test-tube of cold water. Free sulphurous acid will be obtained. Write the equation. EXP. 75. Pass sulphur dioxide gas into a solution of potas- sium hydroxide, KOH. Potassium sulphite will be formed : 2 KOH + S0 2 = K 2 S0 3 + H 2 0. Save the acid and the salt for the tests in the next article. Both the free acid and its salts are used to a limited extent in commerce. They both act as bleaching reagents. On standing, they absorb oxygen, passing into sulphuric compounds. When the sulphites are treated with acids, sulphur dioxide is liberated, thus : K 2 S0 3 + 2 HC1 = 2 KC1 + H 2 O + S0 2 . 102. Tests for Sulphurous Acid and the Sulphites. 1. Free sulphurous acid may be detected by its odor of burning matches. 2. A sulphite is detected by adding hydrochloric acid to its solution. The solution remains clear and gives off the odor of the free acid. 3. A sulphite in solution yields a white precipitate, BaSO 3 , with barium chloride, BaCl 2 . This precipitate is soluble in hydrochloric acid. If a portion of the barium precipitate is treated with nitric acid, the insoluble barium sulphate, BaSO 4 , is obtained. SULPHURIC ACID, H^O^ 103. Occurrence. Small quantities of free sulphuric acid occur in some volcanic waters. Its compounds, the sul- 86 THE SULPHUR OXACIDS. phates, occur plentifully in nature. Thus gypsum or land plaster, CaSO 4 + 2 H 2 O, occurs in vast deposits. It is safe to say that this is the most important acid known to chemistry and to commerce. Although the student has this acid on his table and has used it from the very beginning of his work, it will be well, in view of its great importance, to illustrate the method of its manufacture. 104. Preparation and Properties. Sulphuric acid is man- ufactured on the large scale by oxidizing sulphur dioxide in the presence of moisture thus : S0 2 + + H 2 = H 2 S0 4 . Oxygen from the air is used in oxidizing the dioxide. But sulphur dioxide cannot take up atmospheric oxygen directly. There is a substance, however, that can unite directly with the oxygen of the air, and that is nitrogen dioxide, NO. The reaction in this case is NO + = N0 2 . Now sulphur dioxide can take the atom of oxygen just taken from the air by the nitrogen dioxide thus : It will be noticed that the NO 2 has gone back to its origi- nal form, NO, and is again ready to take another atom of oxygen from the air, after which it will be able to oxidize another molecule of SO 2 , when the same changes will be repeated in the same order an indefinite number of times. But we had a molecule of SO 3 . This unites with a molecule of water thus : THE SULPHUR OXACIDS. 87 And so we have a molecule of sulphuric acid, and the his- tory of this one molecule is the history of all. Ex P. 76. Fig. 25 shows an apparatus for making a small quantity of sulphuric acid. B is a generator containing copper filings and sulphuric acid to generate the sulphur dioxide. D is a tube leading from a bellows to supply the necessary air. C is a flask containing water to furnish steam. A contains copper filings and nitric acid to furnish the nitrogen dioxide. E is an escape-pipe for waste gases. G is a globe used as a FIG. 25. condensing-chamber. A clear glass carboy or large bottle will answer as well. It is perhaps needless to say that all the gases are delivered into the globe simultaneously, and that farther directions for manipulation are unnecessary. In actual practice the manufacturer varies the details of the foregoing description but slightly. He generates the sulphur dioxide by roasting pyrites or by burning crude sulphur. The steam is generated in a boiler, and lead-lined 88 THE SULPHUK OXACIDS. chambers are used for condensing purposes. Sometimes nitric acid is used in place of the nitrogen dioxide. This acid is generated from sodium nitrate and sulphuric acid, as previously explained. In this case what takes place may be represented by the following equation : 2 HN0 3 + 3 S0 2 + 2 H 2 = 3 H 2 S0 4 + 2 NO. Of course it is impossible to tell precisely what the exact changes are, or in what order they occur, but as to the final results there can be no doubt. It will be noticed that nitrogen dioxide, NO, also appears when the nitric acid is used. The acid formed in the leaden chambers is weak, having a specific gravity of 1.55. It is concentrated in leaden pans until it reaches a specific gravity of 1.71, when it is withdrawn and further concentrated and purified in glass or platinum stills until its specific gravity is 1.84, when it is ready for the market. EXP. 77. Moisten a pine splinter with strong sulphuric acid. What occurs ? Thus try a lump of sugar and a grain of starch. Sulphuric acid chars vegetable substances. It abstracts water, or at least hydrogen and oxygen. This acid eagerly absorbs moisture, and thereby becomes dilute. When the union is taking place, much heat is evolved ; therefore it should be an unvarying rule when diluting sulphuric acid to add the acid to the water, and not the water to the acid. .The uses of sulphuric acid in the manufactures are many and important. Thus it is used in bleaching fac- tories, in soda factories, in paper mills, and in manufac- turing artificial fertilizers and in many other important operations. SULPHUR AND .CARBON. 89 NORDHAUSEN OR FUMING SULPHURIC ACID, HaSO^ SO 3 . 105. Fuming sulphuric acid is made by distilling ferrous sulphate containing but one molecule of water : 4 FeS0 4 + H 2 = 2 Fe 2 O 3 + 2 S0 2 + H 2 SO 4 , SO 3 . This acid is used in dissolving indigo in the process of dyeing Saxony blue, and in making the coal-tar colors. It is converted by means of water into ordinary sulphuric acid with the evolution of much heat. 106. Tests for Sulphuric Acid and the Sulphates. 1. Free sulphuric acid or a soluble sulphate in solution is tested by adding barium chloride, BaCL, which throws down the white insoluble precipitate, barium sulphate, BaSO 4 . Add hydrochloric acid to test the solubility of the precipitate. 2. An insoluble sulphate is fused on charcoal with sodium carbonate, the fused mass placed on a silver coin and moistened : a black spot is obtained. Now fuse a fresh portion of the substance with sodium carbonate on porcelain, place on silver and moisten: no black spot is obtained if the substance is a sulphate. 107. Tests for the Thiosulphates. If not in solution, dis- solve the substance in water and add hydrochloric acid : a white precipitate of sulphur is obtained, and sulphur diox- ide set free if a thiosulphate be present. SULPHUR AND CARBON. 108. Carbon Bisulphide, CS 2 , is the only known compound of sulphur and carbon. It is prepared by passing vaporized sulphur over charcoal heated to redness in a cylinder. This substance is a limpid liquid in its pure form and 90 SELENIUM AND TELLURIUM. possesses a pleasant ethereal odor. But in an impure state it is colored and possesses a powerful, sickening odor. Its fumes are poisonous ; hence it is much used for destroying vermin and as an insecticide. In optics it is used for fill- ing prisms, while in the arts it is used as a solvent for rubber gum. Its use in the laboratory has already been exemplified. The odor of the disulphide will serve as a test. SELENIUM AND TELLURIUM. 109. Selenium : Symbol, Se ; Atomic Weight, 79 ; Specific Gravity, 4.3. Selenium is a rare element closely resem- bling sulphur. Berzelius discovered it in 1817 in the resi- due collected from the sulphuric acid chambers at Gripsholm. In a finely divided state and viewed by transmitted light, selenium has a reddish color. It exists in three modifica- tions : viz. amorphous, vitreous, and crystalline selenium. 110. Tellurium: Symbol, Te ; Atomic Weight, 128 ; Spe- cific Gravity, 6.24. Tellurium is a rare element. It is a brittle, bluish white solid, possessing a decided metallic lustre. In its chemical compounds it resembles selenium and sulphur. The following table, given simply for in- spection, will reveal how closely related these three ele- ments are. ATOMIC WEIGHT. SPECIFIC GRAVITY. SOME COMPOUNDS. Sulphur .... 32 2.05 H 2 S S0 2 S0 3 H 2 S0 4 Selenium .... 79 4.30 H 2 Se SeO 2 Se0 3 H 2 Se0 4 Tellurium . . . 128 6.24 H 2 Te Te0 2 TeO 3 H 2 Te0 4 EXERCISES. 91 EXERCISES. (For Review or Advanced Course.) 1. How much sulphur would be required to produce 82 pounds of sulphuric acid ? 2. Test a piece of vulcanized rubber for sulphur by fusing with sodium carbonate, etc. 3. Test a sample of drinking-water for a sulphate. 4. Place some iron filings in a test-tube ; add dilute sulphuric acid, and heat gently. What gas is given off ? (Suo. Test with a match flame.) Evaporate the contents of the tube to dry ness in an evaporating- dish after the iron has dissolved, and test the residue for a sulphate. What sub- stances were obtained ? Write the equation. 5. How can you distinguish between a sulphite and a thiosulphate ? 6. What impurities would one expect to find in commercial sulphuric acid, when the material employed and the process of manufacture are taken into consideration ? CHAPTER VIII. SILICON, BORON, AND PHOSPHORUS, AND THEIR COMPOUNDS. DATA FOR COMPUTATIONS. SILICON : Symbol, Si ; Atomic Weight, 28 ; Specific Gravity, 2.49. BORON: Symbol, B; Atomic Weight, 11; Specific Gravity, 2.5. PHOSPHORUS : Symbol, P; Atomic Weight, 31 ; Specific Gravity, 1.83. SILICON. 111. Occurrence, etc. Silicon is a very abundant ele- ment, which, however, never occurs free. It forms from 22.8 to 36.2 per cent of the earth's crust. With oxygen it forms the abundant compound, silica, SiO 2 . Silica is known to us in many different forms. Thus sand, sand- stone, quartz, quartzite, agate, opal, chalcedony, flint, chert, and hone-stone are almost pure silica. They owe their dif- ferent appearances sometimes to traces of coloring-matter, and sometimes to their physical conditions only. Tripoli consists of the minute, siliceous shells of microscopic plants, the diatoms. Siliceous conglomerates are coarse pebbles that have been joined by deposited silica. The silicates, such as feldspar, mica, and certain clays, are also silicon compounds. Silicon is not used in the arts, and its preparation may be omitted. It has been obtained in three modifications, amorphous, graphitoidal, and crystalline. Of its compounds there are many. Silica is the most abundant. The silicates are a series of compounds of very complex constitution not very well understood. Orthosilicic 02 BORON. 93 acid, H 4 SiO 4 , has not been separated. Silicon unites with hydrogen to form the compound, SiH 4 , which somewhat resembles a gaseous compound formed by phosphorus and hydrogen, in that it is spontaneously inflammable. 112. Tests for Silicon Compounds. Natural forms of sil- ica, as quartz, etc., are readily recognizable by their phys- ical properties. 2. Silicates in solution are first acidulated with hydro- chloric acid, and then carefully evaporated to dryness. The dry mass is then dissolved in hydrochloric acid. If a silicate was present, it will now be reduced to a white insoluble powder, SiOg, which is insoluble in acids, but soluble in potassium hydroxide, KOH. 3. An insoluble silicate is first fused with sodium car- bonate on charcoal and then treated as in 2. BORON. 113. Occurrence, etc. Boron is a quite plentiful element which occurs only in compounds. The principal boron compounds are boric acid, H 3 BO 3 ; borax, Na 2 B 4 O 7 + 10 H 2 O ; and boracite, 2 Mg 3 B 8 O 15 , MgCl 2 . Boric acid occurs in the waters of certain lagoons in Tuscany. Close by are jets of volcanic steam which are employed to evaporate the water, from which crystalline boric acid is deposited. The acid is purified by recrys- tallization. California has several beds of native borax. These beds are on the sites of ancient lakes, long since dried up. Boric acid is obtained from this borax by treatment with hydrochloric acid, after which the boric acid is obtained by crystallization. 94 PHOSPHORUS. 114. Tests for Boric Acid and its Compounds. 1. Free boric acid is detected in solutions by dipping in it a strip of turmeric paper. The strip, when dried, turns brown, and this color is not affected by dilute hydrochloric acid. Alkalies also affect the color of this paper, but hydrochlo- ric acid changes the color produced. 2. A borate may be treated with hydrochloric acid, which frees boric acid. The next step is the same as in 1. 3. A solid borate may be tested by the flame test thus : Make a bead of the substance on a loop of platinum wire and strongly ignite in the Bunsen flame. Now moisten the bead with sulphuric acid and ignite again. Finally moisten the bead with glycerine and heat strongly : a green flame is produced. PHOSPHORUS. 115. Occurrence, etc. Phosphorus is an element which occurs widely distributed, but never in the free state. It occurs in the older igneous rocks, from which all our fer- tile soils are derived. It forms with calcium the minerals phosphorite, Ca 3 (PO 4 ) 2 , and apatite, 3 Ca 3 (PO 4 ) 2 + CaFCl. With iron it forms vivianite, Fe 3 (PO 4 ) 2 + 8 H 2 O. Sombre- rite, an impure form of calcium phosphate, furnishes a part of the phosphorus of commerce. But most of our phos- phorus is obtained from bones. Animals obtain phosphorus from plants, and plants get it from the soil. Phosphorus is prepared from bone-ash. The first step is to convert the ash into acid calcium phosphate, which is accomplished by using sulphuric acid : Ca 8 (P0 4 ) 2 + 2 H 2 S0 4 = CaH 4 (P0 4 ) 2 + 2 CaS0 4 . The solution of acid phosphate is evaporated to dryness and ignited, when calcium metaphosphate is obtained : PHOSPHORUS. 95 CaH 4 (P< > 4 ), = Ca(P0 3 ) 2 + 2 H 2 O. The metaphosphate is now mixed with sand and charcoal, and put in earthen retorts that are placed in tiers in a furnace, and so arranged that their necks extend outside and dip under water (Fig. 26). When heat is applied, phosphorus is liberated, thus: 2 Ca(P0 3 ) 2 + 2 SiO, + IOC = 2 CaSii >, + 10 CO + 4 P. The phosphorus thus ob- tained is melted under wa- ter, and strained through chamois leather, to remove coarse impurities : it is further purified by treat- ing it with sulphuric acid and potassium dichromate, when it is cast in sticks of the form found in market. In addition to the ordi- nary waxy form of phos- phorus found in the ordi- nary sticks of commerce, two other modifications are known. When common phosphorus is dissolved in carbon disulphide and the FIG. -o. solution is allowed to evap- orate slowly, octahedral crystals are obtained. Again, when ordinary or crystalline phosphorus is heated to 240 C. in the absence of oxygen, red or amorphous phosphorus is obtained. Phosphorus is a highly inflammable substance, igniting at low temperatures. In consequence of this property it 96 PHOSPHORUS AND HYDROGEN. is used in large quantities as an ingredient of match-tips. The inflammable nature of phosphorus may be safely shown thus : EXP. 78. Place in a test-tube a bit of phosphorus as large as a kernel of wheat. Dissolve in carbon disulphide, and pour the solution over a piece of filter-paper. Place the paper on a metallic support, and in a short time the disulphide will evap- orate, leaving the phosphorus in a finely divided state, and the paper will soon ignite spontaneously. Phosphorus is a substance that should be handled with care. It should always be taken up with a pair of pincers and should be cut under water. Upon the flesh its burns produce deep and dangerous wounds, often penetrating to the bone. The peculiar odor and the physical characteristics of phosphorus serve to identify it. PHOSPHORUS AND HYDROGEN. 116. Phosphorus and hydrogen form three compounds which are respectively, gaseous, liquid, and solid sub- stances: PH 3 , PH 2 , and P 2 H(?). The first of these is often called phosphine, and its preparation will be given. None of these compounds are of great importance to the beginner. EXP. 79. Place in a generating-flask (Fig. 27) a strong solu- tion of potassium hydroxide. Drop in a few small pieces of phosphorus ; and, lastly, add a small quantity of ether, for the purpose of expelling the air from the apparatus. Insert the delivery-tube, heat gently, and allow the bubbles of phosphine to come up through the water. On striking the air, the gas will be found to be spontaneously inflammable, forming by its PHOSPHORUS AND OXYGEN. 97 combustion rings of phosphorus pentoxide having a peculiar vortex motion. The formation of the gas is as follows : 4 P + 3 KOH + 3 H 2 = 3 KH 2 P0 2 + PH 3 . PHOSPHORUS AND OXYGEN. 117. There are two oxides of phosphorus : viz. P 2 O 3 and P 2 O 5 . The first is obtained when phosphorus is burned in FIG. 2; a limited supply of air, and the second when the air-sup- ply is not limited. These oxides are the anhydrides of phosphorous and phosphoric acids. THE PHOSPHOROUS OXACIDS. 118. There are three primary acids in this series and two others that are derived from phosphoric acid : Hypophosphorous acid . . . H 3 P(X. Phosphorous acid H 3 P0 3 . Phosphoric acid H 3 PC>4. 98 THE PHOSPHOROUS OX ACIDS. When phosphoric acid is heated, water is driven out; and by employing suitable temperatures two derived acids are to be had : Metaphosphoric acid .... HP0 3 . Pyrophosphoric acid .... H 4 P 2 7 . The basicity of hypophosphorous and phosphorous acids merits notice. Hypophosphorous acid is monobasic, only giving up one of its hydrogen atoms. Its formula might, therefore, well be written, HH 2 PO 2 . Phosphorous acid is dibasic, and might be represented by the formula, H 2 HPO 3 . The potassium salts of these acids are, for example, KH 2 PO 2 and K 2 HPO 3 . Phosphoric acid merits further notice. EXP. 80. Place a small quantity of red phosphorus in an evaporating-dish, and cover with reagent nitric acid. Warm gently, adding more nitric acid from time to time, until the phosphorus disappears and red fumes cease to come off. Now expel the excess of nitric acid by heating gently, when phos- phoric acid is obtained as a syrupy liquid. This is a tribasic acid which gives up one, two, or three of its hydrogen atoms. Its sodium salts serve as exam- ples: NaH 2 PO 4 , Na 2 HPO 4 , Na 3 PO 4 . 119. Tests for Phosphoric Acid. 1. To the solution to be tested add ammonia and ammonium chloride. A clear solution is obtained. Now add magnesium sulphate, MgSO 4 , and a white crystalline precipitate, MgNH 4 PO 4 , is obtained, usually after standing some time. 2. Add silver nitrate to the solution to be tested. A light yellow precipitate is obtained, which is soluble in ammonia, nitric acid, and in acetic acid. NOTE. Make both tests before reporting phosphoric acid, and also be sure that no arsenic acid is present. EXERCISES. 99 EXERCISES. (For Review or Advanced Course.) 1. Test a sample of drinking-water for silicates thus : Acidulate with hydrochloric acid one half-litre of the water to be tested. Now evaporate strictly to dryness. Again dissolve the residue in hydrochloric acid, and then examine the contents of the dish used for evaporating the water, for the white powder, SiO 2 . 2. Collect some of the sediment from the bed of a small stream and examine with a microscope for the shells of diatoms. 3. Collect as many forms of silica as possible and describe each form. 4. Why are siliceous pebbles mostly rounded and smooth ? 5. For what household purposes is borax used ? 6. Burn a bit of bone and then dissolve the ash in hydrochloric acid. Now add ammonia, and note the precipitate of calcium phosphate. 7. Test the salts of several different acids for their acids. Does the salt give the test for the acid from which the salt was derived ? CHAPTER IX. INTRODUCTORY TO THE METALS. 120. Properties of the Metals. Formerly the elements were divided into two groups, the Metals and the Non- metals. But it has become apparent that the distinction is not well founded. The elements form a series so closely graded in properties that it is difficult even to define a metal. But in general we may say that a metal is an element which possesses, when in a coherent condition, a peculiar lustre, termed a metallic lustre. Moreover, the oxides of the metals, excepting a very few of the higher ones, are not acid-forming. The specific gravities of the metals vary from that of osmium, 22.48, to that of lithium, 0.59. The specific heat of a metal is always less than unity. It has been found that when the specific heat of an ele- ment is multiplied by the atomic weight of that element a nearly constant quantity is obtained, viz. 6.4. This prod- uct is termed the atomic heat of an element. From an inspection of the results so obtained, Dulong and Petit announced the law : The specific heat of an element varies inversely as the atomic weight of that element. While the law is but approximately true, it has never- theless been utilized in determining the atomic weights of some of the rarer elements. In order to do this, the spe- cific heat of the element was first determined. Some of its compounds were then analyzed, and that 'atomic weight 100 INTRODUCTORY TO THE METALS. 101 was selected which would give a product of about 6.4 when multiplied by the specific heat. The melting-points of the metals vary widely. Thus mercury melts at --40 C., while the most intense heat obtainable has not sufficed to melt osmium. Metals unite in definite and in indefinite proportions to form alloys. Thus brass consists of zinc and copper in varying proportions. Pewter contains four parts tin and one part lead. Alloys are found extremely useful, since in them some particular requirement may be obtained which a single metal does not possess. An amalgam is an alloy of a metal with mercury. 121. Classification of the Metals. In the following pages the metals are classified according to some requirements in analytical work. The method of classification may be made clear by supposing a solution containing a salt of each of the common metals. To this solution hydrochloric acid, HC1, is to be added. With certain of these metals the acid forms insoluble chlorides. These metallic chlo- rides are accordingly precipitated and may be removed from the solution containing the remaining metals by fil- tration. The metals thus precipitated are called the FIRST GROUP METALS. Lead Pb. Silver Ag. Mercury Hg(ous). If through the acid filtrate from which the first group metals have been removed, sulphuretted hydrogen, H 2 S, now be passed, we obtain as precipitates, insoluble in dilute acids, the sulphides of the 102 INTRODUCTORY TO THE METALS. SECOND GROUP METALS. Arsenic As. Antimony Sb. Tin Sn. Bismuth Bi. Copper Cu. Cadmium Cd. Mercury . Hg(ic). These sulphides can now be filtered out, and by a little judicious treatment, to be explained further on, the filtrate is readily prepared for the separation of the next group. The third group metals are precipitated as hydroxides and sulphides insoluble in the presence of an alkali by adding ammonia, NH 3 , ammonium chloride, NH 4 C1, and ammonium sulphide, (NH 4 ) 2 S. Following are THE THIRD GROUP METALS. Iron Fe. Chromium . Cr. Aluminum Al. Nickel Ni. Cobalt Co. Manganese Mn. Zinc Zn. These metals, now in an insoluble compound, may be removed from the solution by filtration, and the filtrate by appropriate treatment may be made ready for the separation of the next group. In the fourth group the metals are precipitated as carbonates insoluble in alkalies by adding ammonia, NH 3 , ammonium chloride, NH 4 C1, and ammonium carbonate, (NH 4 ) 2 CO 3 . INTRODUCTORY TO $HE METALS. 103 THE FOURTH GROUP Barium ........ Ba. Strontium ..,,,.. Sr. Calcium ........ Ca. Magnesium ....... Mg. NOTE. In practice, the magnesium is removed from the solution from which the carbonates of the first three metals of this group have been separated by adding disodium phosphate, Na.jHPO 4 . This precipitates the magnesium as a double salt, magnesium ammonium phosphate, MgNH 4 PO i . Magnesium carbonate is soluble even in alkalies. If now the insoluble compounds of the fourth group be removed by filtration, we have in the filtrate only the fifth group metals. These do not give precipitates with ordi- nary reagents. These are the FIFTH GROUP METALS. Potassium ...... K, Sodium . ..... Na, and the radical Ammonium ...... NH 4 . By following the plan just outlined, the metals are sep- arated into groups. Now each of these groups can be taken up, and the individual metals therein can be sepa- rated from one another, as will be explained in appropriate places. This process of separation and identification is termed Qualitative Analysis. When the weights of the substances present in a compound are determined, the process is termed Quantitative Analysis. We are now ready to study the metals in detail. CHAPTER X. THE FIRST GROUP METALS. DATA FOR COMPUTATIONS. LEAD: Symbol, Pb'' ; Atomic Weight, 207 ; Specific Heat, 0.0315; Melting-point, 334; Specific Gravity, 11.37. SILVER : Symbol, Ag' ; Atomic Weight, 108 ; Specific Heat, 0.0570 ; Melting-point, 1000; Specific Gravity, 10.53. MERCURY : Symbol, Hg'- "; Atomic Weight, 200; Specific Heat, 0.0319 ; Melting-point, -40: Boiling-point, 357.25; Specific Gravity, 13.55. LEAD. 122. Occurrence and Preparation. Metallic lead occurs only in insignificant quantities. Its principal ore is galena, PbS, which occurs in dark, shining cubes, and in other forms belonging to the regular system. Nearly every ore of lead is argentiferous, i.e. silver bearing. c EXP. 81. Place a bit of galena (or a little of any compound con- taining lead) in a shallow cavity which has been prepared in a piece of charcoal (Fig. 28). Cover the substance with sodium carbonate, Na 2 C0 3 , and moisten with a few drops of water. Now heat the sub- stance before the blow-pipe reducing flame. Bright metallic beads will be obtained. Test these beads thus : Place oue on an anvil or on a piece of iron, and strike it lightly with a hammer. Is it malleable ? Brittle ? Cut one of the beads with a knife. Is it hard ? Note the lustre of 104 28. LEAD. 105 the beads, and draw one across a piece of white paper. Does it leave a streak ? Metallic lead is largely used in the arts. It is prepared by heating galena in a limited supply of air. Sometimes a reducing agent like coal-dust is used in its reduction. Ex. Show how the preceding experiment illustrates these processes. Name the uses of metallic lead. 123. Properties and Compounds of Lead. Lead is a sil- very white metal which soon tarnishes in the air. It is much used for lead pipes. It is insoluble in pure water, but natural waters are never pure. Hence lead pipes should never be used for conveying water intended for drinking or for domestic purposes. Lead salts act upon the system as a virulent, cumulative poison. Lead dissolves readily in nitric acid, forming the soluble salt, Pb(NO 3 ) 2 . This salt and the acetate, Pb(C 2 H 3 O 2 )2, when dissolved in water make good solutions for labora- tory practice. Some of the compounds of lead are used in the arts. We notice the following: (a) Lead Oxide or Massicot, PbO, is a yellow powder. Litharge is an impure form of lead oxide. These are pre- pared by heating lead in the air. Litharge is used in mak- ing flint glass and in glazing earthenware. Red lead, or minium, Pb 3 O 4 , is used as a pigment. (5) White lead is a mixture of the carbonate and hy- droxide of lead. This is the best white paint, and is pre- pared by the action of crude acetic acid on sheets of lead that are placed in earthen crocks and covered with ma- nure or spent tan bark. The decomposing manure fur- nishes the carbon dioxide necessary to convert the acetate, first formed, into white lead. 106 SILVER. (c) Lead Acetate, Pb(C 2 H 3 O 2 ) 2 , is much used in medi- cine. It is also used as a reagent in the laboratory. It may be obtained by the action of acetic acid on metallic lead. Lead acetate is used in dyeing, as shown in the following experiment : EXP. 82. Moisten a strip of white cotton cloth in a solu- tion of lead acetate. Now moisten in potassium dichromate solution, K 2 Cr 2 7 . What color is the strip dyed ? (d) Lead Chloride, PbCL, is a precipitate met with in the course of analysis. It is a white crystalline substance, soluble in hot water. () Tartar Emetic, C 4 H 4 KSbO 7 , is used in medicine. It is prepared by dissolving antimony trioxide in potassium tartrate, KHC 4 H 4 O 6 . (c~) Antimony Trisulphide, SboSs, is the orange-colored precipitate obtained in the course of analysis. It is solu- ble in yellow ammonium sulphide. 138. Tests for Antimony. 1. Any antimony compound when heated on charcoal with sodium carbonate yields a bright, brittle bead of metallic antimony. 2. Any solution of an antimony salt gives with hydro- gen sulphide an orange-colored precipitate, Sb 2 S 3 . 3. Antimony compounds may be placed in a generating- flask with zinc and sulphuric acid, and the escaping gas, SbH 3 , may be ignited as soon as the apparatus is free from air and the flame directed against a cold porcelain surface. Black or velvety brown spots of antimony are obtained. These spots may be distinguished from arsenic thus : - (a) An antimony spot with yellow ammonium sulphide turns orange. (b) With hot nitric acid it turns white. () Disodium phosphate gives a white precipitate, A1 2 (PO 4 ) 2 , soluble in potassium hydroxide, insoluble in acetic acid. NICKEL. 163. Occurrence and Preparation. Nickel never occurs free. Its ores occur in connection with the cobalt ores. The most important ore is kupfer-nickel, NiAs. Metallic nickel is obtained mostly in the wet way. The ore is first roasted, and then dissolved in hydrochloric acid. This solution usually contains the chlorides of other metals as well as nickel chloride. These foreign metals are precipi- tated by the addition of proper reagents, leaving the nickel in solution, from which it is precipitated by adding sodium hydroxide. The nickel hydroxide, Ni(OH) 2 , thus obtained is reduced by the action of charcoal at high temperatures. 164. Properties and Compounds of Nickel. Nickel is a white, hard metal, susceptible of a high polish and scarcely tarnishing in the air. It is accordingly used for coinage and for nickel-plating other metals, especially iron. Ger- man silver is an alloy of copper, 5 parts ; nickel, 2 parts ; and zinc, 2 parts. Nickel resembles iron in that it can be welded and can be attracted by the magnet. . S COBALT. S 141 Nickel is soluble in dilute nitric acid, yielding nickel nitrate, Ni(NO 3 )2, which affords a good working solution. The chloride and sulphate are also to be had by using the proper acids. The salts of nickel are used but little. The sulphide, NiS, is the black precipitate obtained in analysis. It is soluble in nitro-hydrochloric acid. 165. Tests for Nickel. A solid supposed to contain nickel is brought into solution by means of nitro-hydrochloric acid, if water will not dissolve it, and tested thus : (a) Ammonia, when added to a solution short of an excess, produces an apple-green precipitate, Ni(OH) 2 . An excess of ammonia gives a blue solution. To this blue solution add potassium hydroxide, when the apple-green hydroxide again appears. (5) Potassium hydroxide added directly to a nickel solution gives the same apple-green precipitate. 2. Any nickel compound in a borax bead in the oxidiz- ing flame colors the bead brownish red while hot, yellow when cold. In the reducing flame the bead becomes gray, metallic nickel being reduced. Cobalt interferes with this test. COBALT. 166. Occurrence and Preparation. Cobalt does not occur free, neither is the metal used in the arts. Speiss co- balt, Co(Ni,Fe)As2, Skutterudite, CoAs,, and cobalt glance, CoFeAs 2 S 2 , are the more important ores. Metallic cobalt is obtained as a gray metallic powder by ' heating the oxide or chloride in an atmosphere of hydrogen. The compounds of cobalt are used in the arts, and they are prepared directly from a cobalt ore, usually speiss cobalt. 142 MANGANESE. 167. Properties and Compounds. Cobalt resembles iron in color and in being attracted by the magnet. The com- pounds of cobalt are useful as furnishing valuable pig- ments. Some compounds follow : (a) Cobalt Oxide, CoO, is an article of commerce. It is used in coloring glass blue and in preparing the cobalt pigments. It may be dissolved in acids, forming salts of the acids used. This oxide is prepared from speiss cobalt. The ore is first roasted, then dissolved in hydrochloric acid, and then the accompanying metals are precipitated by adding successively chlorine, limestone, and hydrogen sulphide. The oxide is now precipitated by the addition, of bleaching-powder. (b) Cobaltous Chloride, CoCl 2 , is used as a sympathetic ink. Its action depends on the fact that when moist the salt is a light pink, but when dry it is violet. Thus the writing becomes visible when the paper is warmed. (c) Cobaltous Nitrate, Co(NO 3 ) 2 , is used in the labora- tory as a reagent. It can be made by dissolving the metal or the carbonate of the metal in nitric acid. (d) Cobaltous Sulphide, CoS, is the precipitate obtained in analysis. It is soluble in nitro-hydrochloric acid. (e) Smalt is a silicate of cobalt used as a pigment. 168. Tests for Cobalt. 1. Any cobalt compound colors the borax bead blue. If an excess of cobalt be present, the bead may be almost black. When powdered, the dust from this bead is blue in all cases. MANGANESE. 169. Occurrence and Preparation. Manganese never oc- curs free nor is it used in the arts. Its chief ore is pyro- MANGANESE. 143 lusite, MnO 2 . It is obtained in the metallic state by fusing one of its oxides mixed with charcoal at a white heat in a closed crucible lined with graphite. 170. Properties and Compounds. Manganese is a red- dish white metal, oxidizing so readily that it is necessary to preserve it under naphtha or coal oil. Some of the man- ganese compounds follow : (a) Manganese Dioxide, MnO^ is the most important of the oxides of manganese. It is used with hydrochloric acid in large quantities for generating chlorine gas in the manufacture of bleaching-powder. Its use in the labora- tory has already been exemplified. (>) Potassium Permanganate, K 2 Mn 2 O 8 , is used in the laboratory, and an impure form of sodium permanganate is used as a disinfecting fluid under the name of Condy's Disinfecting Liquid. These salts may be regarded as originating from the acid, HMnO 4 , or permanganic acid. Manganic acid, H 2 MnO 4 , has not been isolated, but the manganates are known. (c) Manganese Sulphide, MnS, is the flesh-colored pre- cipitate obtained in analysis. It is soluble in cold dilute hydrochloric acid. 171. Tests for Manganese. 1. Manganese compounds in the oxidizing flame give the borax bead a violet color while hot, amethyst-red when cold. In the reducing flame the bead becomes colorless. 2. A solid may be fused on platinum or on porcelain with sodium carbonate and potassium nitrate to a bright green mass, a manganate. Dissolve this mass in nitric acid, and a permanganate is obtained in a red solution. 144 ZINC. ZINC. 172. Occurrence and Preparation. Zinc does not occur free in significant quantities. Smithsonite, ZnCO 3 , is one of the principal ores. Franklinite, (Zn,Fe)O + Fe 2 O 3 ; zinc blende, ZnS ; Willemite, Zn 2 SiO 4 , and a reddish oxide owing its color to an oxide of manganese, are the principal ores employed in the United States. The ores are first roasted and then ground fine ; then they are mixed with half their weight of coal-dust. Now the mixture is placed in clay retorts and heated until the zinc issues in the form of a vapor, which is condensed in iron condensers. Commercial zinc as thus prepared is seldom pure, as it contains small quantities of other metals. 173. Properties and Compounds. Zinc is a malleable, ductile, bluish-white metal which finds many uses. Sheet zinc and galvanized iron, which is sheet iron coated with zinc, are familiar to all. Zinc alloyed with copper forms the useful alloy, brass. For batteries and in the laboratory, zinc is used extensively. Zinc dissolves in most of the acids to form salts that are applicable for working purposes. When taken internally the salts of zinc are poisonous. (a) Zinc Chloride, ZnCl 2 , is obtained when the metal is dissolved in hydrochloric acid. This salt is used as a caus- tic in surgery ; and in organic chemistry it is used for removing the elements of water from many substances. It is used in weighting cotton goods, and in tin-shops as a soldering-fluid. (&) Zinc White, ZnO, is used as a paint. SEPARATION OF THE THIRD GROUP METALS. 145 (c) Zinc Sulphate, or white vitriol, ZnSO 4 + 7 H 2 O, is used in medicine and in dyeing. (c7) Zinc Sulphide, ZnS, is the white precipitate ob- tained in analysis. 174. Tests for Zinc. 1. Solids, when heated on charcoal in the oxidizing flame, give a coating around the assay, yellow while hot, and white when cold. If now the mass and the coating be moistened with cobaltous nitrate and heated again, the pigment, Rinnman's green, is obtained. 2. A solution gives a white precipitate, ZnS, when am- monia and ammonium sulphide are added. SEPARATION OF THE THIRD GROUP METALS. 175. Precipitate the iron, chromium, and aluminum as explained in Art. 153. Filter out the precipitate obtained, wash with water, and then proceed by I. Precipitate the remaining metals of this group by add- ing ammonium sulphide. Warm the solution until the sulphides settle, then filter, wash the precipitate, and proceed by II. I. IRON, CHROMIUM, AND ALUMINUM. 1. Pierce the point of the filter-paper and wash the pre- cipitate through into an evaporating-dish. Take a small portion of this precipitate and dissolve it in nitric acid with heat. Divide the solution thus obtained in two parts and test directly for iron. Potassium sulphocyanide gives a red solution ; potassium ferrocyanide gives a deep blue precipitate. (See Art. 156.) The presence of chromium and aluminum will not interfere with the tests for iron. 146 SEPARATION OF THE THIRD GROUP METALS. If iron be found, test a portion of the original solution to determine whether the iron in it is in the ferrous or ferric condition. 2. For chromium, take a second portion of the hydrox- ides in the evaporating-dish, fuse it on charcoal with sodium carbonate, etc., as in Art. 159, 1. 3. To the remainder of the precipitate in the evapora- ting-dish add potassium hydroxide and boil. The alumi- num will dissolve. Filter, and barely acidify the filtrate with hydrochloric acid; and then add ammonia in excess. A white precipitate, A1 2 (OH) 6 , identifies aluminum. II. NICKEL, COBALT, MANGANESE, AND ZINC. 1. Wash the sulphides of these metals through into a test-tube and add cold, dilute hydrochloric acid; shake frequently. The sulphides of nickel and cobalt do not dissolve, but manganese and zinc are brought into solution. Filter, and treat any residue for nickel and cobalt by 3. Treat the filtrate for manganese and zinc by 2. 2. Boil this filtrate to expel hydrogen sulphide, then add a decided excess of potassium hydroxide. Allow the tube to stand, and shake frequently. Any manganese will be precipitated as Mn(OH) 2 . Filter, and test the precipitate by Art. 171. Test the filtrate for zinc by acidifying with acetic acid and adding ammonium sulphide. Any zinc will give the white precipitate, ZnS. Farther test this precipitate by Art. 174, 1. 3. This residue contains some sulphur obtained from the sulphides that dissolved. Test a portion of the residue by the borax bead. A blue bead identifies cobalt. EXERCISES. 147 If both nickel and cobalt are present, it is somewhat dif- ficult to obtain the tests for nickel, but it may be accom- plished thus : dissolve the remainder of their sulphides in nitre-hydrochloric acid, and add to the solution an excess of potassium hydroxide. A precipitate may be Co(OH) 2 and Ni(OH) 2 . Filter out this precipitate and dissolve it in acetic acid. To this solution add potassium nitrite, KNO 2 . Allow the tube to stand twenty-four hours. Any precipitate will be potassium cobaltic nitrite ; this leaves the nickel in solution. Precipitate it by adding potassium hydroxide, and thus obtain the apple-green hydroxide, Ni(OH) 2 . EXERCISES. (For Review or Advanced Course.) 1. Compute the atomic heat for each of the third group metals. 2. Determine by trial if any of the third group metals can be reduced from compounds to the metallic state by means of the blow- pipe, charcoal, and sodium carbonate. 3. Write the equations for the separation of the third group metals. 4. Obtain a bit of alum from the drug store, and test it for aluminum. 5. Dissolve a bit of iron in hydrochloric acid. Write the reaction. Do you obtain ferrous or ferric chloride ? Test by Art. 156. CHAPTER XIII. THE FOURTH GROUP METALS. DATA FOR COMPUTATIONS. BARIUM: Symbol, Ba ' ; Atomic Weight, 137 ; Specific Heat, ; Melting-point, higher than cast iron ; Speci- fic Gravity, 3.75. STRONTIUM : Symbol, Sr" ; Atomic Weight, 87.2 ; Melting-point, a red heat; Specific Heat, ; Specific Gravity, 2.54. CALCIUM : Symbol, Ca" ; Atomic Weight, 40 ; Specific Heat, 0.1804 ; Melting-point, a red heat; Specific Gravity, 1.57. MAGNESIUM : Sym- bol, Mg" ; Atomic Weight, 24 ; Specific Heat, 0.2450 ; Melting-point, 750 ; Specific Gravity, 1.74. 176. The fourth group metals, often called the " Metals of the Alkaline Earths," are obtained from the nitrate from which the third group has been removed, as explained in Art. 153. This nitrate needs preliminary treatment. It is loaded down with reagents after passing through the operations required in the preceding groups. It is best, therefore, to evaporate it strictly to dryness, and even to ignite the residue gently in order to expel these reagents as far as possible. Then dissolve the residue in water, when it will be ready for the fourth group reagents. Barium, strontium, and calcium are precipitated as the carbonates, BaCO 3 , SrCO 3 , and CaCO 3 , by the addition of ammonia, ammonium chloride, and ammonium carbonate. These metals are then filtered out, and magnesium is ob- tained directly from a portion of the filtrate by adding disodium phosphate, which gives the double phosphate, MgNH 4 PO 4 . It is evident that the remaining portion of the filtrate 148 BARIUM. 149 contains, beside the magnesium that may be present, the fifth group metals. Now since magnesium does not inter- fere with the flame-tests for these metals, this portion of the nitrate is retained for work in the fifth group. BARIUM. 177. Occurrence and Preparation. Barium occurs only in compounds, the chief of which are heavy spar, BaSO 4 , and Witherite, BaCO 3 . This metal is not used in the arts. It is prepared by electrolyzing a thick paste of barium chloride and hydro- chloric acid in the presence of mercury. The barium amalgam thus obtained is heated to expel the mercury, thus yielding a porous mass of metallic barium. 178. Properties and Compounds. Barium burns in the air with great brilliancy. It forms some useful com- pounds. (a) Barium Oxide, BaO, or baryta, is obtained by heat- ing the nitrate until nitrous fumes cease to escape. From this oxide barium hydroxide, Ba(OH) 2 , is prepared by the addition of water. Barium hydroxide is largely used in refining cane-sugar. Baryta water is the solution of this substance in water, which is used as a reagent. (#) Barium Chloride, Bad.*, is used in the laboratory as a reagent. It is prepared by dissolving barium carbonate in hydrochloric acid. () To the filtrate from (a) add potassium sulphate. A white precipitate, SrSO 4 , indicates the presence of stron- tium. Filter. Test the precipitate by Art. 182, 1, to make sure strontium is present. (C 5 H 12 = CM ~ 3 T V. . 108. Methyl-propyl-carbinol Secondary hexyl alcohol CYV V P ~H P -I ^*^*~9 1 Q0 f- \j 6 n u \J = O \ TT . . loo . Methyl-butyl-carbinol iBecondary octyl alcohol nr v r 1 P n _ r 1 ^6 iA is -10-10 f L-xrl^U = \j \ TT . . lol . Methyl-hexyl-carbinol , , 194 OXYGEN DERIVATIVES. Beginning with butyl alcohol there is, in addition to the two classes of alcohols already described, a third class, called tertiary alcohols, made by replacing three hydro- gens from methyl alcohol, with alcohol radicals. LIST OF TERTIARY ALCOHOLS. Boiling-point. Tertiary butyl alcohol "1 { //nTT N I r TT n n J W^a coo > C 4 H 10 O j < Q H Trimethyl-carbinol Tertiary amyl alcohol 1 f (CH 3 ) 2 or > C 5 H 12 = C < C 2 H 5 . . 100. Dimethyl-ethyl-carbinol J I OH Tertiary hexyl alcohol 1 f (CH 3 ) 2 or f C 6 H 14 = CH 4 . This important gas has already been mentioned as forming the most important constitu- ent of illuminating gas produced by the distillation of coal. In this connection it is of interest since it is the lowest member of the olefine series. The members of this series belong to that class of compounds called unsaturated com- pounds. They form addition products in which they act like bivalent radicals. The alcohols, often called G-lycols, and the acids are the most important of the olefine deriva- tives. The alcohols of this series yield two classes of acids. In the first class, the Lactic Acid Series, the acids are mono- basic, and they are derived from their corresponding alco- hols by displacing two atoms of hydrogen and taking up one atom of oxygen. In the second, or Oxalic Acid Series, the acids are dibasic and are derived from their correspond- ing alcohols by the displacement of four atoms of hydrogen and the addition of two atonis of oxygen. Among these acids are found some of the best known of the organic acids. They occur quite widely distributed in nature. They form well-defined series of salts with the metals, some of which are of frequent and extended use. The following table will show the relations between the olefine alcohols and their acids : 201 202 THE OLEFINE DERIVATIVES. Hydro- carbons. Alcohols, or Glycols. Acids (Monobasic). Acids (Dibasic). C 2 H 4 Ethylene, C 2 H 4 (OH) 2 Glycollic, C 2 H 4 3 Oxalic, C 2 H2O 4 C 3 H 6 Propylene, C 3 H 6 (OH) 2 Lactic, C 3 HgO 3 Malonic, C 3 H 4 O 4 C 4 H 8 Butylene, C 4 H 8 (OH) 2 Butylactic, C 4 H 8 3 Succinic, C 4 H 6 O 4 C 6 H 10 Amylene, C 5 H 10 (OH) 2 Valerolactic, C 5 H 10 3 Pyrotartaric, C 3 H 8 O 4 C 6 H 12 Hexylene, C 6 H 12 (OH) 2 Leucic, C 6 H 12 O 3 Adipic, C 6 H 10 4 232, Lactic Acid, C 3 H 6 3 , Lactic acid occurs in sour milk, where it is produced by the action of a lactic acid ferment, Penicillum glaucum, on the sugar of milk. It also occurs in the juices of vegetables that have turned sour. It has not been prepared in the anhydrous condi- tion. It forms a series of salts with the metals that are almost all uncrystallizable and very deliquescent. Lactic acid has two isomers. 233, Oxalic Acid, C 2 H 2 4 . This acid occurs as the acid potassium salt in plants belonging to the species known as Oxalis and in other plants. It can be prepared in a variety of ways, but it is now prepared for commerce by heating pine sawdust with caus- tic potash. Usually a mixture of caustic soda and caustic potash is employed instead of the caustic potash alone. The fused mass is treated with water, when all but the sodium oxalate dissolves. This salt is ignited and then treated with lime-water, whereupon insoluble calcium ox- alate and caustic soda are obtained. From the calcium oxalate, oxalic acid is liberated by means of sulphuric acid, which gives insoluble calcium sulphate and free oxalic acid. From the acid thus obtained in solution, crystals of oxalic acid are secured by concentration and crystalli- THE OLEFINE DERIVATIVES. 203 zation. The caustic alkalies are regained and used to act upon more sawdust. Oxalic acid is readily soluble in water and in alcohol, and upon the system it acts as a poison when taken in large doses. It forms, with the metals, a series of salts, the oxalates, that are used in a variety of ways. Both the acid and its salts possess bleaching properties, and some of the salts serve as useful reagents in the laboratory. 234. Succinic Acid, C 4 H 6 4 . Succinic acid occurs in amber in certain lignites and in fossil wood. It also occurs in such plants as lettuce and wormwood. It is also one -of the products of alcoholic and acetic acid fer- mentation. Commercial succinic acid is prepared by distilling amber and by the fermentation of calcium malate and of tartaric acid. 235. Malic Acid, C 4 H 6 5 . This acid occurs in the juices of fruits, like apples, pears, gooseberries, raspberries, and currants. It can best be prepared from mountain-ash ber- ries or from the stems and leaves of garden rhubarb. The juice is expressed and treated with milk of lime, when in- soluble calcium malate is obtained. This salt is purified, and then decomposed by means of sulphuric acid. This gives insoluble calcium sulphate and malic acid. By comparing the formula of this acid with that of suc- cinic acid, it will appear that malic acid simply has one atom more of oxygen than succinic acid. Hence malic acid is often called oxy-mccinic acid. 236. Tartaric Acid, C 4 H 6 6 . This acid occurs widely distributed in nature. It occurs both in the free state 204 THE OLEFINE DERIVATIVES. and in the form of salts in many fruits along with malic acid. Hydrogen potassium tartrate occurs plentifully in the juice of grapes, from which it is deposited along with the calcium salt during the fermentation of grape juice in the manufacture of wine. The crude 'salts thus obtained are called " Argols " and are employed in assaying. Tartaric acid crystallizes in large transparent prisms, soluble in alcohol and in water. This acid finds many uses in the arts, while the hydrogen potassium salt, KHC 4 H 4 O 6 , often called cream of tartar, is extensively employed in the manufacture of baking-powder. For this purpose this salt is mixed with acid sodium carbonate, and a certain quantity of starch is added as a " filler " to prevent chemical reaction between the other ingredi- ents while in a dry state. This tartrate finds other uses, as in medicine, in silvering, in soldering, and in dye- ing. Tartar emetic has been mentioned under antimony, Art. 137. Tartaric acid has two atoms of oxygen more than suc- cinic acid, whence the name Dioxy-succinic acid which it often bears. The acids of the defines each have two or more isomers which are sometimes distinguished by their action on polarized light. One may rotate the plane of polarization to the right, another to the left, while perhaps a third will be optically inactive. 237. Citric Acid. This acid belongs to a class of compounds called hydroxy acids, since it contains a hydroxyl group, as appears from the rational formula, C 3 H 3 (OH)(CO2H)3. It is a tribasic acid, yielding both acid and normal salts. It occurs widely distributed in nature like malic and tar- taric acids. It is obtained for commerce from lemon juice. THE OLEFINE DERIVATIVES. 205 The juice is allowed to ferment, lime is added, and the calcium citrate thus obtained is then purified, and after- wards treated with sulphuric acid. It is also found in the orange, cranberry, and whortle- berry. With about an equal quantity of malic acid it occurs in the currant, gooseberry, strawberry, cherry, and raspberry, and berries of the mountain-ash. This acid is much used in preparing lemonade and other cooling drinks. It also is used in medicine, in calico- printing, and in dyeing. Of its salts, magnesium citrate, Mg 3 (C 6 H 5 O 7 ) 2 + 14 H 2 O, made by dissolving magnesia, MgO, in citric acid, is used in medicine as a mild pur- gative. Effervescing citrate of magnesia is made by add- ing to this salt citric acid, acid sodium carbonate, and sugar. The whole is then moistened with alcohol and afterwards dried. 238, Glycerine, Glycerol, or Propenyl Alcohol, Glycerine, as will appear from its formula, is a triad alco- hol containing three hydroxyls. This is the best-known compound of its class. In comparing with propylene, C 3 H 6 , it appears that not only are the two combining equivalents of propylene satisfied with hydroxyls, but also one hydrogen is replaced by a hydroxyl. Glycerine, as already mentioned, occurs in most of the fats from which it can be separated by saponification. It can also be isolated by treating the natural fats with super- heated steam ; and it is in this way that a larger part of the glycerine of commerce is prepared. Glycerine is a syrupy, odorless liquid of a sweetish. pleasant taste. It is readily soluble in alcohol and in water, but insoluble in ether and chloroform. It is much used in pharmaceutical preparations, for manufacturing 206 ACETYLENE DERIVATIVES. copying-ink, for "improving" liquors, and, owing to the ease of its digestibility, for a food. But perhaps the largest consumption of glycerine is for the manufacture of the powerful, high-grade, explosive nitro-glycerine, C 3 H 5 (NO 2 ) 3 . This compound is made by treating one part of glycerine with a mixture consisting of four parts of sulphuric acid and one part of nitric acid, at a low temperature. The nitre-glycerine separates out as an oily liquid, and it must be carefully freed from acids to prevent its decomposition, which is frequently accom- panied by terrific explosions. But at its best the liquid is not safe to handle. Consequently it is now mostly used in the form of dynamite or giant powder* These substances are prepared by allowing absorbent substances like Kiesel- guhr, a siliceous kind of earth, to take up the liquid. In this form nitro-glycerine is much used in blasting. It is usually exploded by percussion. 239. Oleic Acid, C^H^. This acid occurs in most of the liquid fats and many solid fats combined with glycer- ine. It is obtained in large quantities as a by-product in manufacturing stearin candles. A crude form of this acid containing other fatty acids may be had by dissolving castile soap in water, and then treating the solution with hydrochloric acid. II. ACETYLENE DERIVATIVES. 240. Linoleic Acid, C^H^O^. Acetylene has been men^ tioned in Art. 82. Of the derivatives belonging to the acetylene series we shall notice but one or two. Linoleic acid occurs combined with glycerine as trilin- olein in linseed oil. It is to this compound that linseed ACETYLENE DERIVATIVES. 207 (flaxseed) oil owes its value as an ingredient of paints. When a thin layer of linseed oil is exposed to the air, oxygen is taken up, and the glycerine is oxidized, leaving a gummy mass behind which is little acted upon by heat or moisture. For the same reasons linseed oil is much used in the manufacture of varnishes. 241. Mannite, or Mannitol, C6H 8 (OH) 6 . Just as glycerine is a triad alcohol, so is niannite a hexad alcohol. This sub- stance occurs in manna, the dried sap of certain species of ash, as Fraxinus ornus and F. rotundifolia. It also occurs in many other forms of vegetation, as in the roots of celery, in the sugar-cane, in olives, and in many fungus-like plants. The manna mentioned in the Bible contained no man- nite, but instead a kind of sugar. It was probably the dried sap of a species of Tamarix. The manna mentioned as falling from heaven may have been a kind of lichen, Spcerothallia esculenta, which is carried about by the winds. There is an isomer of mannite which is called Dulcite. Both these substances possess a sweetish taste, and are more closely related to the carbohydrates of the next chapter than to any other class of compounds. CHAPTER XVIII. THE CARBOHYDRATES. 242, Carbohydrates is a term applied to a class of carbon compounds containing hydrogen and oxygen in the same proportion as found in water. These substances seem to be closely allied to the hexad alcohols, but the exact rela- tions are not very clearly defined. For convenience of consideration the carbohydrates may be divided into three classes : 1. The Sucroses, C^H^On, embracing cane sugar, milk sugar, maltose, etc. 2. The G-lucoses, C 6 H 12 O 6 , embracing grape sugar, levu- lose, etc. 3. The Amyloses, (CeHuAX, 1 including starch, dex- trine, gums, cellulose, etc. These compounds are of the greatest importance. They occur widely distributed throughout the vegetable king- dom, and they play an important part in the nourishment and growth of both plants and animals. The sucroses and glucoses are sweet to the taste and freely soluble in water. The amyloses are generally tasteless and insoluble in water. The first two classes are remarkable for their power of ro- tating the plane of polarized light. Cane sugar, milk sugar, maltose, and grape sugar rotate the plane to the right (+), while levulose rotates it to the left ( ). 1 This formula indicates that the molecular formulas are not exactly determined. 208 THE SUCROSES. 209 Again, many of these compounds possess the property of reducing solutions of cupric salts to cuprous oxide. Upon the two properties last named the methods employed for the quantitative determination of the sugars are based. Thus cane sugar is determined by its dextro-rotary power, specially constructed apparatus being employed, while glucose is estimated by its reducing effect on Fehling's solution, an alkaline solution of copper sulphate, Rochelle salts, and sodium hydroxide. THE SUCROSES. 243, Sucrose, or Cane Sugar, CvfLzfin> This is the best known of all the sugars. It is of wide distribution, and is prepared for commerce in enormous quantities. The prin- cipal sources of cane sugar are the sugar beet, the sugar- cane, the sugar maple, and sorghum. Until recently the sugar-cane furnished the larger part of the sugar of com- merce ; but recent estimates now accredit that honor to the sugar beet. The sugar beet contains from eight to twenty per cent of cane sugar and the sugar-cane from fourteen to twenty. In exceptional cases the percentages for both have been known to exceed twenty per cent. There have been many processes employed in manufac- turing sugar. The simplest of these is the one employed in making maple sugar. An incision is made in the tree, and just beneath is fastened a spile or spout which carries the sap into a trough or bucket placed at the foot of the tree. At intervals the sap is collected and carried to large kettles or pans that are frequently placed in the sugar forest at some convenient location. These kettles are often placed in the open air, and are heated by means of direct fires. Here the sap is evaporated, and any scum that rises 210 THE SUCROSES. is simply skimmed off. When the sap reaches a syrupy consistence, it is removed from the large kettles, and the "sugaring off" is completed in smaller kettles, very fre- quently on the kitchen stove. In this latter process the concentration is carried on till the sugar will grain on cooling, when it is placed in pans or tins and allowed to cool. It is now ready for market. Of late many improvements have been introduced into the manufacture of sugar from sugar beets and sugar-cane. That known as the " diffusion process " is by all means the best. In this process the canes or beets are first cut into thin slices, or sometimes in the case of beets they are torn into shreds. Now by the judicious application of hot water the sugar diffuses through the cell walls of the plants, leaving behind most of the uncrystallizable im- purities. In order to accomplish this end, a series of from twelve to sixteen boiler-iron cylinders or " cells " are arranged in a circle to form what is termed a "bat- tery." These cells are first filled with the chips, and then a charge of hot water and steam is introduced into No. 1. From here the water is next forced into No. 2, and then into No. 3, and so on around. When the last cell is reached the water has taken up sugar from every cell until it is now a somewhat concentrated sugar solution. It will readily be understood that the chips in the first cell where the water was pure have lost more sugar than the chips in any of the succeeding cells ; also that as the water passed along from cell to cell it gradually took less and less sugar, so that the chips in the last cell were ex- hausted least of all. From the last cell the concentrated solution is run into a large liming-tank, and a fresh charge THE SUCROSES. 211 of water is started in again at No. 1 and passed around as before. Other charges of water are then introduced into No. 1 and passed around until the chips in that cell are ex- hausted. Then these chips are removed and fresh ones are introduced. Now the next charge of fresh water is started at No. 2, and finally taken out at No. 1. Then fresh chips are placed in No. 2, and the next charge of water is started at No. 3 and taken out at No. 2 ; and thus the process is continued. When the liming-tank is filled, it is heated, and lime is added to remove impurities. From this tank the juice is passed into another, where the excess of lime is removed by means of carbon dioxide. If necessary, the juice is next filtered through boneblack filters, from which it is passed into vacuum pans, where it is concentrated until the crys- tal] izing-point is reached. The crystals are removed and dried in centrifugal driers. By further concentration a second and even a third crop of crystals may be obtained, when nothing is left excepting uncrystallizable molasses. The molasses from beet sugar is much used for manufac- turing alcohol. Raw sugars from the cane and from beets are usually sent to the refiners, where the remaining impurities are removed, and the sugar worked up in a variety of ways ready for the market. France and Germany now produce most of the beet sugars of the world. This industry now bids fair to become established in the United States. Cane-sugar crystals obtained by slow evaporation are large and transparent, but when the crystals are formed rapidly, they are small, striated, and nearly opaque. Water at 45 dissolves nearly two and a half times its weight of 212 THE SUCROSES. cane sugar. When fused at about 175 for some time, sugar is changed into a mixture of levulosan and dextrose : C^H^On = C 6 H 10 5 -{ C 6 H 12 6 . When heated to higher temperatures a substance called Caramel is produced. When submitted to still higher tem- peratures, or when treated with concentrated sulphuric acid, sugar is decomposed, oxygen and hydrogen in the proportions found in water are removed, and carbon is left behind. EXP. 99. Dissolve 2 g or 3 g of sugar in about the same quantity of water, and while the solution is warm slowly add concentrated sulphuric acid. Note the remaining carbon. When sugar in water solution is strongly heated or ex- posed to the action of dilute acids, or of certain other reagents, it is changed into " invert sugar," which is Isevo- rotary, and which consists of a mixture of equal parts of levulose and dextrose : C 12 H 22 O n -f- H 2 = C 6 H 12 6 -f- C 6 H 12 6 . In alcoholic fermentation the ferment first changes the sugar into invert sugar, after which the conversion into alcohol proceeds by the further action of the ferment on the invert sugar. Cane sugar of itself is not fermentable. 244. Milk Sugar, Lactose, C 12 H 22 O n . Milk sugar is an isomer of cane sugar, which occurs in the milk of the Mammalia, and of which it constitutes about four per cent. This sugar is said to occur in but one plant, a tree, Sapota achras, a native of the West Indies. Commercial milk sugar is prepared from milk whey, which is simply concentrated and allowed to stand in a cool place until the sugar separates out in crystals. Some- THE GLUCOSES. 213 times the crystallization is aided by suspending strings in the whey. As found in commerce, milk sugar usually con- sists of elongated crystalline masses containing one equiv- alent of water. It is hard and gritty, and is not very sweet to the taste. It is employed in medicine. When the sugar in milk ferments, it yields lactic acid and alcohol. The lactic acid coagulates the albumen of the milk, and thus causes the milk to thicken. Maltose is also an isomer of cane sugar, which is pre- pared by the action of malt on starch. There are several other isomers of cane sugar which are of less importance. THE GLUCOSES. 245. Grape Sugar, Dextrose, or Glucose, C 6 H 1:i 6 . Grape sugar occurs widely distributed in plants along with equal parts of levulose, the two forming invert sugar. Some cane sugar is usually present at the same time. Grape sugar also occurs in honey, but it is most plentiful in the sweet juices of ripe fruits such as grapes, cherries, etc. This sugar is called dextrose, owing to its dextro-rotary action on polarized light. Under the name of Glucose grape sugar is now manufac- tured in enormous quantities by heating starch with water containing from one to two per cent of sulphuric acid. EXP. 100. To 100 CC of water in a flask add l cc of sulphuric acid, and boil. Slowly add to the contents of the flask, without checking the boiling, 10 g of starch which have been made into a paste with water. Boil for three hours. Then add powdered chalk or marble until the acid is completely neutralized, and then filter. Finally evaporate the filtrate to a thick syrup, and then set it away in a cool place. Note the taste, and from time to time examine the solution for crystals of glucose. 214 THE AMYLOSES. The preceding experiment illustrates in a general way the process employed in manufacturing glucose. Glucose is now extensively used in the manufacture of candy and syrups and for the adulteration of cane sugar. It is cheaper than cane sugar, and is not so sweet. Unless properly purified it contains some substances which act upon the system like the pernicious fusel oil found in impure alcoholic liquors. EXP. 101. Test samples of sugar, candy, and syrups for glucose, thus : First prepare one-half litre of Fehling's solu- tion as follows : Dissolve 17.32 g pure copper sulphate in a small quantity of water, and then add 100 s of Rochelle salts (sodium potassium tartrate). Then add ahout 300 CC of a solu- tion of sodium hydroxide of a specific gravity 1.12. Then dilute to one-half litre by adding pure water. Now place about 10 CC of the clear blue solution thus pre- pared in a large test-tube, and boil. While still boiling add a few drops of a water solution of the substance to be tested, and continue the boiling for a short time. Then add a few drops more of the same solution, and boil as before. If the Fehling's solution loses color, add more of the substance to be tested, and boil. Continue this process until the color is destroyed. Now allow the solution to stand a short time, and if a reddish precipitate of cuprous oxide collects in the tube, glucose is pres- ent. Cane sugar has no reducing effect on the copper solution. Levulose, which has already been mentioned several times, occurs with dextrose in fruits, etc. It it a Isevo-rotary iso- mer'of dextrose that does not crystallize. It is nearly as sweet as cane sugar. THE AMYLOSES. 246. Starch, or Amylum, (C 6 H 10 5 ), ( , Starch occurs in nearly every part of most growing plants, and especially of THE AMYLOSES. 215 those plants containing chlorophyll. It is formed from the protoplasm which the chlorophyll cells contain. But the largest deposits are to be found in seeds, grains, tubers, bulbs, and piths, where the starch is stored away to fur- nish material for the next season's growth. Some biennial and perennial plants make deposits of starch in their thickened leaves for the same purpose. EXP. 102. Agitate about 100 g of wheat bran with sufficient water to form a thin paste. Filter through a linen cloth, using pressure if necessary. Allow the filtrate to stand for some time. Test the white sediment that is deposited for starch, by moistening a part of it with a dilute solution of iodine in potas- sium iodide solution. If starch be present, it will turn blue. Moisten a second portion of the sediment with a dilute solution of potassium iodide, and then examine it with a microscope magnifying from 200 to 300 diameters. Similarly prepare and test starch from corn and potatoes. Also examine the pith of growing twigs of trees for starch. Starch is prepared for commerce from a variety of sub- stances, such as corn, wheat, arrow-root, and potatoes. In one of the common processes employed, the starch is washed out of the moistened and finely divided substance by means of water, after which it is allowed to ferment in order to destroy some of the impurities present. Finally, it is washed in pure water by decantation. The grains of starch exhibit under the microscope pecul- iar markings and forms which differ according to the source from which the starch was obtained. Thus the microscope is able to reveal the origin of any sample of starch as well as to expose any adulteration. The markings are more clearly brought out by treating the starch with dilute potassium hydroxide solution. 216 THE AMYLOSES. The largest grains of starch occur in the potato, while the smallest are found in rice. When starch is heated to 205, it is converted into an isomer termed Dextrine. This is much used as a substitute for gum arabic. The backs of postage stamps and the flaps of envelopes are gummed with dextrine. When the starch is moistened with a mixture of dilute hydrochloric and nitric acids, the conversion into dextrine takes place at from 100 to 125. In fact, most of the dex- trine of commerce is prepared in this way. 247. The Gums, (C 6 H 10 5 ) n . Of the gums, gum arabic and gum tragacanth are well-known examples. Gum arabic exudes from several species of acacias, which are natives of tropical regions. These gums are used for mak- ing mucilage, confectionery, and inks, and for many phar- maceutical purposes. Nearly every kind of wood and vegetable tissue carries' gummy substances, which are usually soluble in water. 248, Cellulose, (C 6 H 10 5 ) n . Cellulose occurs in all plants, since it forms the basis of all cell-walls. But it seldom occurs pure, as some of the solids which the sap carries in solution are deposited in the cell-walls during the growth of the tissues. Cellulose is of great importance, since it forms the bulk of many fibres which are used in enormous quantities. Among these fibres may be mentioned cotton, hemp, flax, and wood fibres which are extensively used for making cloth, cordage, paper, etc. Gun-Cotton, or cellulose hexnitrate, C 12 H 14 (NO 3 ) 6 O 10 , is a powerful explosive prepared by first treating cotton wool with alkalies to remove gummy matters, after which it is ui IYER SIT y THE AM treated with a mixture of strong nitric and-ffBftpfiOnc acids. Finally, it is washed with much pure water until every trace of free acid is removed in order to prevent sponta- neous decomposition, which is often accompanied by disas- trous explosions. ' Collodion is a solution of some of the lower nitrates of cellulose in a mixture of alcohol and ether. It is used in surgery and in photography. 249. The Glucosides. Under this name are included a number of substances occurring in plants. On decompo- sition they yield a glucose together with other substances. Amygdalin, C^H^NOu-fEIIaO, occurs in bitter almonds, apple seeds, peach pits, etc. Salicin, C ]3 H 18 O 7 , is found in the bark of willows, and in the bark and leaves of poplars. The Tannins occur in the barks of certain trees, but more especially in the gall-nuts found on oak-trees. The tannins have the property of forming inks with ferric salts. They are largely used for that purpose, and for tanning leather. CHAPTER XIX. THE TERPENES, BENZENES, STYRENES, NAPHTHALENES, AND ANTHRACENES, AND THEIR DERIVATIVES. THE TERPENES, C n H 2n _ 4 . 250, The Terpenes, C 10 H 16 . Of this series of hydrocar- bons, the turpentines, the camphors, and certain essential oils are among the best-known compounds. Turpentine, C 10 H 16 , is the product of southern pine-trees, Pinus australis. Turpentine is also obtained in some parts of Europe. A tree is wounded, and the pitch which oozes out is allowed to collect in a box or pocket which is cut into the tree. In France a vessel is used to collect the pitch. From time to time the pitch is gathered up until a sufficient quantity has been collected, when it is sub- jected to distillation. The turpentine distils over, and the solid residue is sold under the name Rosin. Ex. State the uses of turpentine. When turpentine is acted upon by hydrochloric acid, a peculiar substance called Artificial Camphor, C 10 H 16 HC1, is produced. This substance closely resembles camphor. Camphor, or Laurinol, C 10 H 16 O, is obtained by distilling with water chips of Laurus camphora, a tree growing in China and Japan. Borneo Camphor, C 10 H 16 O, occurs in Dryolalanops cam- phora, a tree native to Borneo and the adjacent islands. 218 THE BENZENES. 219 Belonging to the terpene series are a large number of essential oils that occur in various parts of different plants. Among these oils those of lemon, bergamot, neroli, mace, sassafras, bay, anise, fennel, peppermint, spearmint, laven- der, and rosemary may be mentioned as consisting princi- pally of terpenes. Closely allied to the terpenes is Caoutchouc, or Indian Rubier, which consists of the dried milky juice of the Jatropha elastica and other kindred plants. Vulcanized rubber contains from twelve to fifteen per cent of sulphur, and is prepared by heating caoutchouc with sulphur to about 150. At higher temperatures Vul- canite or Ebonite is obtained. G-utta Percha is the dried juice of a tree, Isonandra percha, a native of the East Indies. THE BENZENES, C n H 2n _ 6 . 251. Benzene, CeHe. This series is often called the Aromatic Series, since several fragrant compounds belong to it. The lowest known term is Benzene (not the com- mercial benzine, which is a mixture of paraffin hydrocar- bons), or, as it is sometimes called, Benzol. Coal tar has been mentioned as one of the by-products in the manufacture of illuminating gas ; and it is from this source that benzene is chiefly obtained. The crude tar is subjected to fractional^ distillation. The " first runnings," which include all products boiling under 110, contain small quantities of benzene. The "light oil," however, coming over between 110 and 210 contains benzene in larger quantities. From this light oil benzene is separated and purified by further fractional distillation and by treat- ment with sulphuric acid and caustic soda. 220 THE BENZENES. Benzene is a colorless, strongly refracting liquid, pos- sessing a characteristic odor, and burning with a luminous but smoky flame. It boils at 80.5. It serves as an excel- lent solvent for various fats, resins, alkaloids, etc., and it is extensively used in the manufacture of the aniline dyes. Benzene forms both substitution and addition products ; but in all these compounds all six carbon atoms appear. Various facts noted in the chemical behavior of benzene have led to the adoption of a graphical formula in which the carbon atoms are arranged in the form of a ring or closed chain, the carbons being connected alternately with one and two linkages. This formula may be represented as follows : H I C H-C X ^C-H H-C I H Now the substitution products of benzene are made by replacing one or more of the hydrogens, leaving the carbons undisturbed. In the best known of the addition products, benzene acts like a hexad radical, thus : benzene hexchloride, C 6 H 6 C1 6 ; benzene hexbromide, C 6 H 6 Br 6 . To account for these com- pounds, the supposition has been made that one of each of the double links has been broken, thus giving up six bonds to new uses. Since any one or all of the hydrogens of benzene may be replaced by a radical ; and further, since the hydrogens of these substituted radicals may be replaced by elements THE BENZENES. 221 or radicals ; and again, since each compound may have sev- eral isomers, it is evident that the derivatives to be obtained from benzene are simply innumerable. Of the homologous series of which benzene is the first member, four members are known : Benzene ........ C 6 H 6 . Toluene ........ C 7 H 8 . Xylene ........ C 8 H 10 . Cyinene ...... . . We can here notice only a few of the most important compounds derived from this series. 252. Phenol, Phenyl Alcohol, or Carbolic Acid, Phenol, although a true alcohol corresponding to the hydrocarbon benzene, is quite generally known as carbolic acid. It is prepared from that fractional distillation prod- uct of coal tar which boils between 150 and 200. The "middle oil"' obtained between these temperatures is treated with caustic soda and afterward with sulphuric acid. Now since phenol forms a hydrate with water which splits up into the pure acid and water upon distillation, this reaction is used for the final purification of the better grades of carbolic acid. Phenol possesses a characteristic odor, is soluble in water, and when taken internally it is a violent poison. It is much used as a disinfectant. Phenol forms a well-defined series of derivatives, among which is trinitrophenol, or Picric Acid, C^H^NOg^OH. Picric acid is a very bitter poisonous substance which is used alone for dyeing silk and woollen goods yellow. With other dyes it is used for producing different shades. 222 THE BENZENES. Picric acid is now manufactured by the action of nitric acid on phenolsulphonic acid, C 6 H 4 (OH)SO 3 H, although it is to be had by the use of phenol and nitric acid. 253, Resorcin and Pyrogallol. It will be noticed that phenol is a monad alcohol, but just as one would expect there are other benzene alcohols. Resorcin, C 6 H 4 (OH) 2 , is a diad alcohol obtained by melting various resins with caustic potash. It is largely used in manufacturing dyes. Pyrogallol, or Pyrogallic Acid, C 6 H 3 (OH) 3 , is a triad alcohol obtained by subliming gallic acid at from 210 to 220. It is found in commerce as lustrous, flaky, or acicular crystals. It is used as a reagent in gas analy- sis on account of the ease and rapidity with which it absorbs oxygen. It is also used in photography as a developer. 254. Nitrobenzene, C 6 H 5 N0 2 , Nitrobenzene is a light yellow, strongly refracting liquid which has an odor re- sembling the oil of bitter almonds somewhat modified by another odor suggesting oil of cinnamon. It is manufactured in large quantities under the name of artificial oil of bitter almonds or essence of mirbane. It is prepared by treating benzene with a mixture of strong nitric and sulphuric acids. The 'crude oil is purified by passing through it a current of steam, after which it is treated with caustic soda and distilled with steam under pressure. Although nitrobenzene is somewhat poisonous, and has an irritating effect on the skin, nevertheless it is used in perfuming the cheaper grades of soap. But the largest quantities are employed in the manufacture of aniline, aniline blue, aniline black, and magenta. THE BENZENES. 223 255. Aniline, Amidobenzene, or Phenylamine, Aniline is now manufactured in enormous quantities for use in preparing the aniline dyes. It is obtained by the action of nascent hydrogen on nitrobenzene. The nitro- benzene is placed in a large iron cylinder fitted with a stirring apparatus, and the hydrogen is furnished by add- ing directly to it hydrochloric acid and iron. The crude product is purified by distillation. Aniline is a colorless liquid of a characteristic odor and possessing strong basic properties. It forms definite salts with the ordinary acids, and together with its compounds it is invaluable to the color industry. It acts upon the system as a powerful poison. 256. The Toluenes. Toluene, C 7 H& is obtained by dis- tilling toluic acid with an excess of lime. It occurs natu- rally in petroleum, and can be obtained by various reactions upon benzene. The Cresols, C 7 H 8 O, of which there are three isomers, occur in coal tar, pine tar, and creosote. The toluene alcohol, C 7 H 7 OH, is called Benzyl Alcohol. It occurs in balsam of Peru and in balsam of Tolu. The aldehyde of benzyl alcohol, C 7 H 8 O, or benzoic alde- hyde, is the true Oil of Bitter Almonds. It occurs in a glucoside, amygdalin, one of the constituents of bitter almonds, cherry pits, laurel leaves, etc. Under the influ- ence of emulsin, a ferment found in amygdalin itself, amygdalin breaks up into glucose, prussic acid, and oil of bitter almonds : CaHjyNOu + 2 H 2 = 2 CeHjA + HCN + C 7 H 6 0. Benzoic aldehyde on oxidation passes into Benzoic Acid, C 7 H 6 O 2 , a monobasic acid occurring in gum benzoin and 224 THE BENZENES. the balsams of Peru and Tolu. It also occurs in the urine of herbivorous animals. Benzoic acid may be obtained in a variety of ways, but the best commercial article is ob- tained by subliming gum benzoin. Cheaper forms are prepared from the urine of cows and horses, and by the oxidation of toluene. EXP. 103. Place a small quantity of benzoic acid in a beaker with no lip, and then fit a paper funnel over the mouth of the beaker. Place the apparatus on the sand-bath and heat gently. Note the sublimate of benzoic acid which collects inside the funnel. Salicylic Acid, C 7 H 6 O 3 , occurs as methyl salicylate in oil of wintergreen, from which it is prepared for commercial purposes. It is also prepared by treating benzene with caustic soda and carbon dioxide. Salicylic acid is now largely used as an anti-ferment and in medicine. G-allic Acid, C 7 H 6 O 5 , occurs in many plants, such as sumach, Chinese tea, and in nut-galls. It is prepared from nut-galls by the fermentation of the tannin which they contain. Tannic Acid, C 14 H 10 O, also occurs in nut-galls, from which it is obtained for commerce. Nitrotoluene, C 7 H 7 NO 2 , is prepared by treating toluene with nitric acid. By reduction with hydrogen this sub- stance is reduced to Amidotoluene, C 7 H 7 NH 2 , which is a necessary constituent of the red and violet aniline colors. This substance occurs as an ingredient of commercial aniline. There are three isomeric Xylenes, C 8 H 10 , all to be ob- tained from coal tar. Cymene, C 9 Hi 2 , occurs in oil of cara- way and in oil of thyme. It can be prepared from the terpenes. THE STYRENES, OB CINNAMINES. 225 Closely related to the benzene derivatives is the common substance known as Indigo. The indigo plants are natives of tropical countries. From them indigo is prepared by placing the plants in tanks and covering them with water. Fermentation sets in, and when it is completed the water solution is drawn off, carrying the coloring-matter in solu- tion. Upon standing, the indigo is precipated, when it is collected, pressed, and dried ready for the market. The value of indigo depends upon the amount of Indigo Blue, or Indigotin, C 16 H 10 N 2 O2, which the crude article contains. Indigo is now prepared artificially. THE STYRENES, OR CINN AMINES, C n H 2n _ 8 . 257. Styrene, or Cinnamine, C^S. 8 . - - This hydrocarbon occurs in liquid storax, a fragrant, honey-like substance which yields styrene upon distillation with water and sodium carbonate. Styryl alcohol, C 9 H 10 O, belongs to this series, and its al- dehyde, cinnamic aldehyde, C 9 H 8 O 2 , constitutes the greater part of the essential oil of cinnamon. Cinnamic acid, C 9 H 8 O 2 , closely resembles benzoic acid. It occurs in storax and in balsam of Peru. This acid is now manufactured on the large scale by treating benzyl chloride, C 7 H 6 Cl2, with sodium acetate. THE NAPHTHALENES, C n H 2n _ 1-2- 258. Naphthalene, C 10 H 8 . This hydrocarbon occurs in large quantities in the heavier portions of coal tars, boiling between 180 and 220. It crystallizes in large pearly plates. From careful studies of the chemical behavior of naphthalene it has been discovered that this hydrocarbon consists of two benzene residues which con- 226 THE ANTHRACENES. tain two carbons in common. The following formula will show its constitution : H H I I C 1 0* H-C^ X C X ^C-H I II I H-C ^C-H ^C / ^C^ I I H H Naphthalene, C 10 H 8 . Naphthalene forms many derivatives, and among them are some of the most beautiful dyes. Thus Martius' Yel- low, C 10 H 5 OH(NO 2 ) 2 , Naphthol Yellow S., K 2 C 10 H 4 N 2 SO 8 , and other splendid colors belong to this series. THE ANTHRACENES, C n H 2n _i 8 . 259. Anthracene, C 14 H 10 . Anthracene is prepared from those portions of coal tar boiling between 340 and 360. It crystallizes in white, silky scales or plates, and like naphthalene it furnishes beautiful dyes. Its constitution is exemplified by the following formula : H H I I C H C // \ I / % H-C C-C-C C-H I II I II I H-C C-C-C C-H % / I \ // C H C I I H H Anthracene, C H H, . THE ANTHRACENES. 227 Among the dyes derived from anthracene we may men- tion Alizarin, C 14 H 8 O 4 , and Purpurin, C 14 H 8 O 5 . These substances are found naturally in madder root, which has been used from the earliest times as the source of a red dye. Formerly large tracts of land were devoted to the cultivation of the madder plant, but now Turkey Red, as this dye is called, is nearly all obtained from coal tar. CHAPTER XX. THE ALKALOIDS AND THE ALBUMINOIDS. 260, The term Alkaloids is applied to a class of sub- stances contained in a large variety of plants, and espe- cially those containing medicinal and poisonous principles. Our knowledge of the constitution and relations of these substances is extremely limited, and in most cases entirely wanting. The alkaloids are optically active on polarized light; some being dextro-rotary, and some being Isevo-rotary. In their chemical behavior they resemble the amines and the amides ; and they all contain carbon, hydrogen, and nitro- gen, and nearly all contain oxygen. They are nearly all crystallizable, especially those that are solids ; and they form crystallizable salts with the ordinary acids. Conine, C 8 H 15 N, the active principle of poison hemlock, and Nicotine, C 10 H 14 N 2 , the active poison found in tobacco, are liquids. These are among the most important of the liquid alkaloids. Caffeine, C 8 H 10 N 4 O 2 , is found in tea and coffee, and in other plants that are used to prepare infused beverages. Theobromine, C 7 H 8 N 4 O2, is found in cocoa. Opium, the dried sap of certain species of poppies, fur- nishes about nineteen different alkaloids, which possess more or less active properties. Among the more note- worthy are Morphine, C 17 H 19 NO 3 . H 2 O ; Codeine, C 18 H 21 NO 3 ; 228 THE ALKALOIDS AND THE ALBUMINOIDS. 229 Thebaine, C 19 H 21 NO 3 ; and Narcotine, C^H^NO,. The sul- phates of these alkaloids are most used. Cinchona bark furnishes about twenty-one alkaloids, of which Quinine, C^K^NgO,,, and Cinchonine, C^H^^O, are the most important. The sulphates and chlorides of these alkaloids find extended use. Nux vomica furnishes the powerful poisons, Strychnine, e n HaNA, and Brucine, C^HJSTA 4 H 2 O. The reader is referred to any of the standard works on pharmacy, or to the dispensatories, for lists and descrip- tions of the crude drugs and alkaloids used in medicine. 261. The Albuminoids are compounds of very complex constitution, concerning which our knowledge is quite incomplete. They do not crystallize, but exist in an amorphous, jelly-like form ; and in consequence it is nearly impossible to obtain them in a state of sufficient purity to enable us to determine with exactitude the pro- portions in which their constituents unite, or even to be certain what elements are present in the pure compounds. Nevertheless, these compounds are of great importance to both plants and animals. In plants they occur in nearly every part, but more especially in the seeds. In young and growing plants, particularly those used as food for man and animals, the albuminoids are quite generally dis- tributed throughout the tissues. G-luten is the albuminoid found in grains, and is a sticky, elastic substance which gives tenacity to dough. Albumen is found, in the purest form, in the whites of eggs. This substance may be obtained, as a flocculent precipitate, by adding acetic acid to the white of an egg, and then diluting with water. Albumen also occurs in the serum of blood. 230 THE ALKALOIDS AND THE ALBUMINOIDS. Fibrin may be obtained from fresh blood by whipping it with a bundle of twigs. Fibrin, when thus obtained, and after washing with water, appears in the form of whitish threads, which are tasteless and insoluble in water. Fibrin remains in solution while the blood is circulating through its proper channels ; but on removing the blood from the circulation, the fibrin immediately causes coagulation. Casein is the albuminoid found in milk, and separates out as curd when the milk becomes sour. The albuminoids possess in common the property of coagulating, upon the application of heat, or by con- tact with alcohol. They readily undergo putrefaction, and in other respects their resemblances are close. They all contain sulphur, and many of them contain phosphorus, beside carbon, nitrogen, hydrogen, and oxy- gen. No formula can, with certainty, be assigned to albumen. INDEX. (INORGANIC AND ORGANIC.) [The numbers refer to pages.] Absolute alcohol 192 Acetic acid 196 Acetone 197 Aceto-nitril 186 Acetylene 61, 72 Acids 59 Acid salts 61 Addition products 173 Agate 92 Albumen 229 Albuminoids 30, 229 Alizarin 227 Alkalies, " Fixed " 31 "Volatile" 31 Alkaloids 228 Alloys 101 Aluminum 138 Occurrence and preparation, 138 Properties and compounds, 138 Tests 140 Aluminum bronze 139 Aluminum hydroxide 139 Aluminum sulphate 139 Aluminum trioxide 138 Alums 139 Anfalgams 101 Amido benzene 227 Amines 185 Ammonia, Occurrence 30 Preparation and properties, 31 Tests.. 33 Ammonium 161 Salts of 162 Amorphous phosphorus 95 Amygdalin 217 Amyloses 208 Amylum 214 Analysis of an unknown 163 Aniline 223 Anthracene 226 Anthracite 67 Antimony 118 Occurrence and preparation, 118 Properties and compounds, 118 Tests 119 Antimony acids 119 Antimony oxides 119 Antimonyl salts 118 Antimony trisulphide 119 Arabs 1 Argillaceous iron ore 132 Argols 204 Aromatic series 219 Arsenic 114 Occurrence and preparation, 114 Properties and compounds, 115 Tests 116 Arsenic acid .115, 116 Arsenic pentoxide 116 Arsenic trioxide 116 Arsenious acid 116 Arsenious sulphide 116 231 232 INDEX. Arsines 187 Artificial camphor 218 Asbestos 153 Asphalt 179 Asphaltum 179 Atomic theory 8 Atomic weights 8 Atoms 7 Aqua ammonise 31 Aqua regia 47 Avogadro's hypothesis 38 Baking-powder 75 Barium 149 Occurrence and preparation, 149 Properties and compounds, 149 Tests 150 Barium carbonate 149 Barium chloride 149 Barium hydroxide 149 Barium oxide 149 Barium sulphate 149 Baryta 149 Baryta water 149 Bases 60 Basic salts 61 Beet sugar 209 Benzene 219 Benzoic acid 223 Benzol 219 Benzyl alcohol 223 Beryl 139 Binary compounds 57 Bismuth 122 Occurrence and preparation, 122 Properties and compounds, 122 Tests 123 Bismuth nitrate 123 Bismuth ochre 122 Bismuth trioxide 123 Bismuth trisulphide 123 Bismuthite 122 Bismuthyl nitrate 123 Bismuthyl salts 123 Bituminous coal 67 Black diamonds 68 Blanc de farcl 123 Blanc d'Espagne 123 Bleaching-powder .48, 152 Bog iron ore 132 Bohemian glass 161 Boneblack 66 Borneo camphor 218 Boron, Occurrence. 93 Tests 94 Brass 144 Brimstone 79 Bromic acid 51 Bromine, Occurrence 50 Preparation 50 Test 50 Bromine oxacids 51 Brucine 229 Butyric acid 199 Cacodyl compounds 188 Cadmium 125 Occurrence and preparation, 125 Tests 126 Cadmium iodide 126 Cadmium sulphide 126 Caffeine 228 Calcium 151 Occurrence and preparation, 151 Properties and compounds, 152 Tests 153 Calcium carbonate 151^ 153 Calcium chloride 152 Calcium hydroxide 152 Calcium oxide , 152 Calc spar 152 Calomel . .110 INDEX. 233 Camphor 218 Cane sugar 209 Caoutchouc 80, 219 Caramel 212 Carbamides 186 Carbamines 186 Carbinol 193 Carbohydrates 208 Carbolic acid 221 Carbon, Occurrence 65 Preparation and properties, 65 Tests 69 Carbonado 68 Carbon dioxide, Occurrence. . . 72 Preparation and properties, 73 Tests 75 Carbon disulphide 89 Carbon monoxide 72 Carbonylamines 186 Casein 230 Cassiterite 120 Cast iron 134 Celestine 150 Cellulose 216 Cellulose hexnitrate 216 Chalcedony 92 Charcoal 65, 66 Chemical affinity 10 Chemism 10 Chemistry, Origin of 1 Chert 92 Chili saltpetre 158 China clay 138 Chloric acid 48 Test 49 Chloral 196 Chloral hydrate 196 Chlorine, Occurrence. 43 Preparation and properties, 43 Test 43 Chlorine oxacids. . 48 Chlormethane 180 Chloroform 180 Chlorous acid, 48 Chrome alum 137 Chrome ironstone 137 Chrome yellow 106, 137 Chromic oxide 137 Chromium, Occurrence, etc 137 Tests 138 Cinchona bark 229 Cinchonine 229 Cinnabar 79 Cinnamic acid 225 Cinnamic aldehyde 225 Cinnamine 225 Citric acid 204 Clay 92 Clay ironstone 132 Coal 65, 67 Coal tar 71, 219 Cobalt 141 Occurrence and preparation, 141 Properties and compounds, 142 Tests 142 Cobalt glance 141 Cobalt oxide 142 Cobaltous chloride 142 Cobaltous nitrate 142 Cobaltous sulphide 142 Codeine 228 Coke 71 Collodion 217 Combining number 9 Compounds 7 Condensation of vapors 39 Condy's disinfecting fluid .... 143 Conine 228 Copper 124 Occurrence and preparation, 124 Tests 125 Copper aceto-arsenite 116 234 INDEX. Copper arsenite 116 Copper sulphate 125 Corals 152 Corrosive sublimate 110 Cosmoline 178 Cresols 223 Crocoisite 137 Crystallization 15 Cyanic acid 186 Cyanogen 186 Cyamiric acid 186 Cymene 221, 224 Cymogene 178 Decantation 3 Determination of atomic weights, 63 Determination of molecular weights 37 Determination of valence 64 Dextrine 216 Dextrose 212, 213 Diamond drills 68 Diamond dust 68 Diamonds 65, 67, 68 Dibasic acids 84 Diffusion batteries 210 Diffusion of gases 22 Diffusion process 210 Dimethylamine 185 Dioxy-succinic acid 204 Dog-tooth spar 152 Dolomite 153 Dryobalanops camphora 218 Dulcite 207 Dulong and Petit' s law 101 Dutch liquid 71 Dynamite 206 Ebonite 81, 219 Electrolysis 24 Elements denned . . 4 Elementals and derivatives. . . . 171 Elixir vitse 1 Equations 56 Ethane 69, 189 Ethyl alcohol 189 Ethyl aldehyde 196 Ethylene..... 71,201 Ethyl ether 194 Ethyl nitrate 200 Evaporation 2 Experimentation .... 1 Experiment denned 2 Fehling's solution 214 Feldspar 92, 138 Fermentation 73 Ferric chloride 135 Ferric hydroxide 135 Ferrous sulphate 135 Ferrous sulphide 135 Fibrine 230 Fifth group metals 103, 156 Filtration 3 Fire damp 70 First group metals 101, 104 First runnings 219 Flashing-point 179 Flint 92 Flowers of sulphur 79 Fluorine 53 Fool's gold 79, 132 Formic acid 184 Formic aldehyde 184 Fourth group metals 103, 155 Fractional distillation 191 Franklinite 144 Fulminating powder 187 Fusible metals 122 Galena 79, 104 Gallic acid . . .224 INDEX. 235 Gas carbon * 67 Gasoline 178 Gaultheria procumbens 182 Giant powder 206 Glacial acetic acid 197 Glass 161 Glucose 213 Glucoses 208 Glucosides 217 Glycerine ^ . . . 205 Glycerol 205 Gluten 229 Gold 128 Grape sugar 213 Graphite 65, 67, 134 Guignet's green 137 Gums 216 Gun-cotton 40, 216 Gunpowder 40, 159 Gutta percha 219 Gypsum 79, 152 Hematite 132 Halogen derivatives 172 Heavy spar 79 Higher compounds 59 Homologous series 169 Homology 169 Hone stone 92 Hydracids 59 Hydriodic acid 53 Tests 53 Hydrobromic acid 51 Hydrocarbons 170 Hydrochloric acid 46 Test 47 Hydrocyanic acid 76, 186 Hydrogen 19 Test 22 Hydrogen sulphide 81 Tests, . 82 Hydroxylamine 187 Hypobroinous acid 51 Hypochlorous acid 48 Hyponitrous acid 38 Hypophosphorous acid 97 Hyposulphurous acid 84 Iceland spar 151 Illuminating gas 71 Indian rubber 219 Indigo 225 Indigo blue 225 Indigotin 225 Invert sugar 212 lodic acid 53 Iodine 51 Tests 52 Iodine pentoxide 53 lodoform 181 Iron 132 Properties and compounds, 135 Tests 136 Iron furnace 133 Iron pyrites 79, 132 Iron slag 134 Isocyanides 186 Isomerism 174 Isomers 175 Isonandra percha 219 Isonitroso compounds 187 Jatropha elastica 219 Kaolin 138 Kelp 52 Kerosene 178 Ketones 197 Kupfer nickel 140 Lac sulphuris 80 Lactic acid.. . 202 236 INDEX. Lactic acid series 201 Lactose 212 Lampblack 65 Laurinol 218 Lauras camphora 218 Law of definite proportions ... 8 Law of multiple proportions . . 36 Lead 104 Properties and compounds, 105 Tests 106 Lead acetate 106 Lead chloride 106 Levulosan 212 Levulose 214 Light oil. 219 Lignite 67 Lime-kilns 152 Linoleic acid 1 206 Litharge 105 Lodestone 132 Lubricating oil 178 Lunar caustic 108 Magnesia 154 Magnesite 153 Magnesium .... 153 Tests 154 Magnesium carbonate 154 Magnesium chloride 154 Magnesium sulphate 153, 154 Malic acid 203 Manganese 142 Tests 143 Manganese dioxide 143 Maganese sulphide 143 Manganic acid 143 Manna 207 Mannite 207 Mannitol 207 Maple sugar 209 Marble... . 152 Marsh gas 70 Martius' yellow 226 Massicot 105 Meerschaum 153 Melissic acid 199 Mercaptans 187 Mercuric chloride 110 Mercury 109 Tests Ill Mercurous chloride 110 Mercurous nitrate 110 Metallic derivatives 188 Metals, Introduction . . . , 100 Metals of the alkalies 156 Metals of the alkaline earths . . 148 Metameric isomers 175 Methane. 69, 180 Methyl alcohol 182 Methyl aldehyde 184 Methylamine 185 Methyl ether 183 Methyl chloride 180 Methyl mercaptan 187 Methyl salicylate 182 Mica 92 Middle oil 221 Milk of sulphur 80 Milk sugar 212 Mispickel 114 Molecular formulae 10 Molecules ' 9 Monobasic acids 84 Morphine 228 Naphtha 178 Naphthaline 225 Naphthol Yellow S 226 Narcotine 229 Natural gas 70 Nickel 140 Tests.. . 141 INDEX. 237 Nicotine 228 Nitric acid 39 Tests 41 Nitrils 186 Nitrobenzene 222 Nitro-compounds 187 Nitrogen 29 Nitrogen derivatives 172 Nitrogen monoxide 35 Tests 36 Nitrogen oxacids 38 Nitro-glycerine 40, 206 Nitro- hydrochloric acid 47 Nitro-inethane 186 Nitrous acid 38 Nordhausen or fuming sulphuric acid 89 Normal salts 61 Nux vomica 229 Oil of bitter almonds 223 Oil of wintergreen 182 Olefiant gas 69 Olefine acids and alcohols 202 Oleic acid 206 Opal 92 Opium 228 Organic chemistry 168 Organic substances 168 Oriental amethyst 138 Oriental emerald 138 Oriental topaz 138 Orpiment 114 Orthoclase 156 Orthosilicic acid 92 Oxacids 59 Oxalic acid 202 Oxalic acid series 201 Oxides of chlorine 48 Oxides of nitrogen 34 Oxides of phosphorus 97 Oxygen 12 Tests 17 Oxygen derivatives. 172 Oxysuccinic acid 203 Ozone 16 Palmitic acid 199 Paraffin 178 Paraffin series 176 Paris green 116 Peat 67 Penicillum glaucuui 202 Pentathionic acid 84 Perbromic acid 51 Perchloric acid 48 Periodic acid 53 Permanganic acid 143 Petroleum 177 Phenol 221 Phenylamine 223 Philosopher's stone 1 Phosphine 96 Phosphines 187 Phosphoric acid 97 Phosphorous acid 98 Phosphorus 94 Picric acid 221 Pinus australis 218 Plastic sulphur 80 Platinum 129 Polymeric isoiners 175 Porcelain clay 138 Potash 159 Potassium 156 Properties and compounds, 157 Tests 159 Potassium bichromate 137 Potassium carbonate 159 Potassium chlorate 158 Potassium ferrocyanide 136 Potassium ferricyanide 136 238 INDEX. Potassium hydroxide 158 Potassium iodide 158 Potassium nitrate , . . . 158 Potassium permanganate 143 Potassium sulphate 156 Precipitation 2 Propenyl alcohol 205 Proteids 30 Prussic acid 76 Purpurin 227 Pyrogallic acid 222 Pyrogallol 222 Pyrolusite 142 Qualitative analysis 103 Quantitative analysis 103 Quartz 92 Quartzite 92 Quicklime 152 Quinine 229 Red fire 150 Red oxide of mercury 109 Red phosphorus 95 Reduction 3 Resorcin 222 Rhigoline 178 Rinmann's green 145 Roll sulphur 79 Rosin 218 Ruby 138 Safety lamp 70 Salicin 217 Salicylic acid 224 Salt 159 Saltpetre 156, 158 Salts 60 Sand 92 Sandstone 92 Sapota achras 212 Sapphire 138 Scheele's green 116 Schweinfurth's green 116 Secondary alcohols 192 Second group metals 102, 114 Separation of 126 Separation of first group metals, 111 Separation of third group metals, 145 Shells 152 Silica 92 Siliceous conglomerates 92 Silicon 92 Tests 93 Silver 106 Properties and compounds, 107 Tests 107 Silver chloride 108 Silver nitrate 108 Silver-plating solution 108 Skutterudite 141 Smalt 142 Smithsonite 144 Soap 197 Soda-water 95 Sodium 159 Properties and compounds, 160 Test 161 Sodium aluminate 139 Sodium carbonate 160 Sodium stannate 121 Soft coal 67 Solution 163 Solution of gases 31 Soot 65 Speiss cobalt 141 Spirits of hartshorn 33 Spiritus setheris nitrosi 200 Stannic acid 121 Stannic sulphide 121 Stannous sulphide 121 INDEX. 239 Starch 214 Stearic acid 199 Steel 134 Stibines 187 Stibnite 118 Stone coal 67 Stream tin 120 Strontianite 150 Strontium 150 Tests 151 Strontium nitrate 150 Strychnine 227 Styrene 225 Styryl alcohol 225 Subnitrate of bismuth 123 Substituted ammonias 185 Substituting power and valence, 63 Substitution 172, 173 Succinic acid 203 Sucrose 209 Sucroses 208 Sugar manufacture 210, 211 Sulphonic acids 188 Sulphur 79 Tests 81 Sulphur derivatives 172 Sulphur dioxide 83 Tests 84 Sulphur trioxide 83, 84 Sulphuric acid 84, 85 Preparation and properties, 86 Tests 89 Sulphurous acid 84, 85 Sylvite 156 Synthesis 24 Symbols 7 Table of elements 5, 6 Table of primary hydrocarbons, 170 Table of primary paraffin alco- hols and acids 198 Tannic acid 224 Tannins 217 Tartar emetic 119 Tartaric acid 203 Tellurium 90 Terpenes 218 Tertiary alcohols 194 Tetrabasic acids 84 Tetrathionic acid 84 Thebaine 229 Theobromine 228 Thiosulphuric acid 84 Test 89 Third group metals. ...... 102, 131 Tin 120 Tin, Properties and compounds, 121 Test 121 Tin stone 120 Toluene ; 221 Toluenes 223 Topaz 139 Tribasic acids 84 Trichlor-rnethane 180 Tri-iodo- methane 181 Trimethylamine 185 Trithionic acid 84 Turf 67 Turkey red 227 Turpentine 218 Turquoise 138 Uniformity of derivatives 175 Unsaturated radicals 174 Urea 186 Valence 62 Vaselene 178 Ventilation 77 Vinasses 176, 182, 185 Vinegar 196 Vulcanite 81, 219 240 INDEX. 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The Old English epic poem, with introduction, translation, glossary and fac-simile page. $1.60. Students' edition without translation. 35 cts. COOk's The Bible and English Prose Style. Approaches the study of the Bible from the literary side. 60 cts. Simonds' Sir Thomas Wyatt and his Poems. 168 pages. With biography, and critical analysis of his poems. 75 cts. Hall's BeOWUlf. A metrical translation. $1.00. Students' edition. 35 cts. Norton's Heart Of Oak Books. A series of five volumes giving selections from the choicest English literature. Phillips's History and Literature in Grammar Grades. An essay showing the intimate relation of the two subjects. 15 cts. See also our list of books for the study of the English Language. D. C. HEATH & CO., PUBLISHERS. BOSTON. NEW YORK. CHICAGO. READING. Badlara's Suggestive Lessons in Language and Reading. A manual for pri- mary teachers. Plain and practical ; being a transcript of work actually done in the school- room. $1.50. Badlam's Stepping-Stones to Reading. A Primer. Supplements the 28 3 -page book above. Boards. 30 cts. Badlam'S First Reader. New and valuable word-building exercises, designed to follow the above. Boards. 35 cts. Bass's Nature Stories for Young Readers : Plant Life, intended to supple- ment the first and second reading-books. Boards. 30 cts. Bass's Nature Stories for Young Readers : Animal Life. Gives lessons on animals and their habits. To follow second reader. Boards. 40 cts. Fuller's Illustrated Primer. Presents the word-method in a very attractive form to the youngest readers. Boards. 30 cts. Fuller's Charts. Three charts for exercises in the elementary sounds, and for combin- ing them to form syllables and words. The set for $1.25. Mounted, $2.25. Hall's HOW tO Teach Reading. Treats the important question: what children should and should not read. Paper. 25 cts. Miller's My Saturday Bird Class. Designed for use as a supplementary reader in lower grades or as a text-book of elementary ornithology. Boards. 30 cts. Norton's Heart Of Oak Books. This series is of material from the standard imagin- ative literature of the English language. It draws freely upon the treasury of favorite stories, poems, and songs with which every child should become familiar, and which have done most to stimulate the fancy and direct the sentiment of the best men and women of the English-speaking race. Book I, 96 pages, 25 cts.; Book II, 268 pages, 45 cts.; Book III, 308 pages, 55 cts.; Book IV, 370 pages, 60 cts.; Book V, 378 pages, 65 cts. Smith's Reading and Speaking. Familiar Talks to those who would speak well in public. 70 cts. Spear's Leaves and FlOWers. Designed for supplementary reading in lower grades or as a text-book of elementary botany. Boards. 30 cts. Ventura's Mantegazza's Testa. A book to help boys toward a complete self -develop- ment. $1.00. Wright's Nature Reader, NO. I. Describes crabs, wasps, spiders, bees, and som univalve mollusks. Boards. 30 cts. Wright's Nature Reader, NO. II. Describes ants, flies, earth-worms, beetles, bar- nacles and star-fish. Boards. 40 cts. Wright's Nature Reader, NO. III. Has lessons in plant-life, grasshoppers, buttei- flies, and birds. Boards. 60 cts. Wright's Nature Reader, NO. IV. Has lessons in geology, astronomy, world-life, etc. Boards. 70 cts. For advanced supplementary reading see our list of books in. English Literature. D. C. HEATH & CO., PUBLISHERS, BOSTON. NEW YORK. CHICAGO. HISTORY. Sheldon's United States History. For grammar schools. Follows the " seminary " or laboratory plan. " By it the child is not robbed of the right to do his own think- ing." Half leather. $1.25. Teacher's Manual to Sheldon's United States History. A key to the above system. 60 cts. Sheldon's General History. For high school and college. The only general history following the "seminary" or 'laboratory plan now advocated by leading teachers. Half leather. $1.75. Sheldon's Greek and Roman History. Contains the first 250 pages of the above book. $1.00. Teacher's Manual tO Sheldon's History. Puts into the instructor's hand the key to the above system. 85 cts. Sheldon's Aids to the Teaching of General History. Gives also list of most essential books for a reference library. 10 cts. Thomas's History Of the United States. For schools, academies, and the general reader. A narrative history with copious re illustrated. 532 pages. Half leather. #1.25. reader. A narrative history with copious references to sources and authorities. Fully alf l Shumway's A Day in Ancient Rome. With 59 illustrations. Should find a place as a supplementary reader in every high-school class studying Cicero, Horace, Taci- tus, etc. 75 cts. Old South Leaflets. Reproductions of important political and historical papers, ac- companied by useful notes. Each, 5 cts. and 6 cts. For titles see separate lists. Per hundred, $3.00. Allen's History Topics. Covers Ancient, Modern, and American history, and gives an excellent list of books of reference. 121 pages. Paper. 30 cts. Fisher's Select Bibliography of Ecclesiastical History. An annotated list of the most essential books for a theological student's library. 15 cts. Hall's Method Of Teaching History. "Its excellence and helpfulness ought to v secure it many readers." The Nation. $1.50. Phillips' History and Literature in Grammar Grades. A paper read before the Department of Superintendence, at Brooklyn, N.Y. Paper. 15 cts. See also our list of Old South Leaflets. D. C. HEATH & CO., PUBLISHERS, BOSTON. NEW YORK. CHICAGO. CIVICS, ECONOMICS, AND SOCIOLOGY. Boutwell's The Constitution of the United States at the End of the First Century. Contains the Organic Laws of the United States, with references to the decisions of the Supreme Court which elucidate the text, and an historical chapter re- viewing the steps which, led to the adoption of these Organic Laws. In press. Dole's The American Citizen. Designed as a text-book in Civics and morals for the higher grades of the grammar school as well as for the high school and academy. Con- tains Constitution of United States, with analysis. 336 pages. $1.00. Special editions are made for Illinois, Indiana, Ohio, Missouri, Nebraska, No. Dakota, So. Dakota, Wisconsin, Minnesota, Kansas, Texas. Goodale's Questions to Accompany Dole's The American Citizen. Con- tains, beside questions on the text, suggestive questions and questions for class debate. 87 pages. Paper. 25 cts. Gide's Principles Of Political Economy. Translated from the French by Dr. Jacobsen of London, with introduction by Prof. James Bonar of Oxford. 598 pages. $2.00. Henderson's Introduction to the Study of Dependent, Defective, and Delinquent Classes. Adapted for use as a text-book, for personal study, for teachers' and ministers' institutes, and for clubs of public-spirited men and women engaged in considering some of the gravest problems of society. 287 pages. $1.50. Hodgin'S Indiana and the Nation. Contains the Civil Government of the State, as well as that of the United States, with questions. 198 pages. 70 cts. Lawrence's Guide to International Law. A brief outline of the principles and practices of International Law. In press. Wenzel's Comparative View Of Governments. Gives in parallel columns com- parisons of the governments of the United States, England, France, and Germany. 26 pages. Paper. 22 cts. Wilson's The State. Elements of Historical and Practical Politics. A text-book on the organization and functions of government for high schools and colleges. 720 pages. $2.00. Wilson's United States Government. For grammar and high schools. 140 pages. 60 cts. Woodburn and Hodgin's The American Commonwealth. Contains several orations from Webster and Burke, with analyses, historical and explanatory notes, and studies of the men and periods. 586 pages. $1.50. Sent by mail, post paid on receipt of prices. See also our list of books in History. D. C. HEATH & CO., PUBLISHERS, BOSTON. NEW YORK. CHICAGO. SCIENCE. Shaler'S First Book in Geology. For high school, or highest class in grammar school. #1.10. Bound in boards for supplementary reader. 70 cts. Bollard's World Of Matter. A Guide to Mineralogy and Chemistry. $1.00. Shepard's Inorganic Chemistry. Descriptive and Qualitative; experimental and inductive; leads the student to observe and think. For high schools and colleges. $1.25. Shepard's Briefer Course in Chemistry ; with Chapter on Organic Chemistry. Designed for schools giving a half year or less to the subject, and schools limited in laboratory facilities. 90 cts. Shepard's Organic Chemistry. The portion on organic chemistry in Shepard's Briefer Course is bound in paper separately. Paper. 30 cts. Shepard'S Laboratory Note-Book. Blanks for experiments: tables for the re- actions of metallic salts. Can be used with any chemistry. Boards. 40 cts. Benton's Guide to General Chemistry. A manual for the laboratory. 4 octs. Remsen's Organic Chemistry. An Introduction to the Study of the Compounds of Carbon. For students of the pure science, or its application to arts. $1.30. S Laboratory Manual. Containing directions for a course of experiments in Organic Chemistry, arranged to accompany Remsen's Chemistry. Boards. 40 cts. ' Coit's Chemical Arithmetic. With a short system of Elementary Qualitative Analysis For high schools and colleges. 60 cts. Grabfield and Burns' Chemical Problems. For preparatory schools. 60 cts. Chute's Practical PhysiCS. A laboratory book for high schools and colleges study- ing physics experimentally. Gives free details for laboratory work. $1.25. Colton's Practical Zoology. Gives a clear idea of the subject as a whole, by the careful study of a few typical animals. 90 cts. Boyer's Laboratory Manual in Elementary Biology. A guide to the study of animals and plants, and is so constructed as to be of no help to the pupil unless he actually studies the specimens. Clark's Methods in MicrOSCOpy. This book gives in detail descriptions of methods that will lead any careful worker to successful results in microscopic manipulation. $1.60. Spalding's Introduction tO Botany. Practical Exercises in the Study of Plants by the laboratory method, go cts. Whiting's Physical Measurement. Intended for students in Civil, Mechani- cal and Electrical Engineering, Surveying, Astronomical Work, Chemical Analysis, Phys- ical Investigation, and other branches in which accurate measurements are required. I. Fifty measurements in Density, Heat, Light, and Sound. $1.30. II. Fifty measurements in Sound, Dynamics, Magnetism, Electricity. $1.30. III. Principles and Methods of Physical Measurement, Physical Laws and Princi- ples, and Mathematical and Physical Tables. $1.30. IV. Appendix for the use of Teachers, including examples of observation and re- duction. Part IV is needed by students only when working without a teacher,. $1.30. Parts I-III, in one vol., $3.25. Parts I-IV, in one vol., $4.00. Wllliams's Modern Petrography. An account of the application of the micro- scope to the study of geology. Paper. 25 cts. For elementary -works see our list of booksinElementary Science. D. C. HEATH & CO, PUBLISHERS. BOSTON. NEW YORK. CHICAGO. 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