GIFT OF PROF. W.3. RISING WILLARD B. RISING Mo. TEXT-BOOKS OF SCIENCE ADAPTED FOR THE USE OF ARTISANS AND STUDENTS IN PUBLIC AND OTHER SCHOOLS. QUALITATIVE CHEMICAL ANALYSIS AND LABORA TOR Y PRA CTICE. LONDON : PRINTED BY SPOTTISWOODE AND CO., NEW-STREET SQUARE AND PARLIAMENT STREET SPECTRA Of THE METALS Of THE ALKALIES 3c ALKALINE EARTH!: ! Illlliiii i!:li; ! 'llii:ii|||||i!ii!liiii!i! ! . ' Llltllllll >l 11:1 ilil II! 1 . li; < \ 'llil Ulil'l A. B C D E T In QUALITATIVE CHEMICAL ANALYSIS AND LABORATORY PRACTICE. BY T. E. THORPE, PH.D. F.R.S.E. PROFESSOR OF CHEMISTRY ANDEKSONIAN INSTITUTION, GLASGOW : AND M. M. PATTISON MUIR, F.R.S.E. LONDON : LONGMANS, GREEN, AND CO. 1874. All rights reserved* PREFACE. THIS BOOK is divided into two distinct parts. In PART I. the student is instructed to perform a series of experiments, in order to familiarise himself with the leading properties of the chief non-metallic elements, and of the principal sub- stances which they form by their mutual union. This por- tion of the book is, of course, supplementary to the work of the lecture-room, and should be studied in connexion with a manual in which the origin, properties, and relations of the various bodies are fully described. The experiments are generally of a very simple nature, and are strictly illustrative of the chemical and physical properties of the substances to which they refer. To each lesson is appended a short statement or summary of the facts which that lesson is intended to convey. The object of these resumes is to afford the student precise ideas of the nature and extent of the information which he has gleaned from the experiments he has performed. The advantages of this preliminary course are manifest. Not only does the student become practically familiar with the properties of a large number of chemical agents, but he acquires opportunities for the exercise of manipulative skill and dexterity in the construction and arrangement of appa- 237346 vl Preface. ratus, which the few and simple operations of ordinary qualitative analysis are not so well fitted to give. In arranging this course of laboratory practice we have sought to cover the Scheme of Practical Instruction sketched out in the Syllabus of the Science and Art Department. PART II. treats of Qualitative Analysis ; it is divided into five sections. In the first section the general preliminary operations of testing are described, such as the employment of flame reactions, the use of the Bunsen flame, the spectroscope, . and so for'.h. The second section treats of systematic qualitative testing. The wet and dry reactions of each of the more commonly occurring bases and acids, inorganic and organic, are first described, after which a synopsis of analytical methods is given. The third section gives the special tests for the rarer elements, and shows where they may be expected, and how they may be separated, in the ordinary course of analysis. The fourth and fifth sections have been added mainly for the use of medical students. We have endeavoured to make this book as practical as possible. The methods of analysis are, of course, mainly founded on established and reliable processes. Still the book will be found to contain a number of novelties both in Preface. vii the way of shortening the course of systematic testing and in the recognition of bodies by means of special tests. We have hesitated, however, to adopt new methods, unless experience has shown them to be preferable to the older ones. All the experiments described in the First Part have been carefully tried ; and with the exception of certain of the separations of the rarer metals and organic poisons, which, however, will be recognised as well-established pro- cesses, all the operations described in the Second Part have been repeatedly tested by ourselves and by students in this Institution. Our thanks are due to Mr. DUGALD CLERK and to MR. STEPHEN MILLER for the attention they have bestowed on the woodcuts. CONTENTS. PART I. PREPARATION AND PROPERTIES OF GASES. LIQUIDS, AND SOLIDS. LESSON I. PAGE Oxygen Its Preparation Bending Glass Tubes^-Use of the Pneumatic Trough Oxygen supports Combustion Distinc- tive Character of Chemical Action Meaning of the Term 'Chemical Test' I LESSON II. Hydrogen Its Preparation Its Lightness Pouring Hydrogen Upwards Formation of Zinc Sulphate Crystallisation of a Salt 9 LESSON III. Combination of Oxygen with Hydrogen Composition of Water Combustion of Oxygen in Hydrogen Combustion of Air in Coal Gas Meaning of the term ' Combustion ' . . .12 LESSON IV. Nitrogen - Its Preparation It does not support Combustion It is not itself combustible It differs from Carbon Dioxide . .18 LESSON V. Nitric Acid its Preparation Distillation Tests for Nitric Acid. 19 x Contents. LESSON VI. PAGE Nitrogen Monoxide Its Preparation Meaning of the terms ' Neutralisation ' and ' Salt ' Nitrogen Monoxide supports Com- bustion Difference between its Power of supporting Combus- tion and that of Oxygen Difference between Nitrogen Monox- ide and a Mixture of Nitrogen and Oxygen . . . -23 LESSON VII. Nitrogen Dioxide Its Preparation Its Power of supporting Combustion Difference between this and the Power of Nitro- gen Monoxide Action of Oxygen on Nitrogen Dioxide Analysis of Air . 27 LESSON VIII. Ammonia Its Preparation Collection of Gases by Displacement Combustion of Ammonia Slow Combustion of Ammonia Formation of Ammonium Chloride Solubility of Ammonia in Water 30 LESSON IX. Carbon Dioxide Its Preparation Its Density Its Action on Lime Water and on Litmus Solution It does not support Com- bustion Decomposition of Carbon Dioxide Its Solubility in Water It is absorbed by Caustic Potash Solution ... 36 LESSON X. Carbon Monoxide Its Preparation Decomposition of Oxalic Acid by means of Sulphuric Acid Separation of Carbon Monoxide ,and Dioxide Combustion of Carbon Monoxide . . .40 LESSON XL Chlorine Its Preparation Its Affinity for Hydrogen Its Bleach- ing Action Its Oxidising Action 43 Contents. xi LESSON XII. PAGE Hydrochloric Acid Its Preparation It does not support Com- bustion, nor is it Combustible It is soluble in Water Its Action on Litmus Solution Synthesis of Hydrochloric Acid Analysis of Hydrochloric Acid .... 47 LESSON XIII. Bleaching Powder Its Preparation Theory of Bleaching Hypochlorous Acid Its Preparation Potassium Chlorate Its Preparation Its Properties Chlorine Tetroxide Its Prepara- tion . . . -49 LESSON XIV. Bromine Its Preparation Its Detection Preparation of Potas- sium Bromide Solubility of Bromine in Water Combination of Bromine with Phosphorus ....... 5 2 LESSON XV. Iodine Its Preparation Sublimation Tests for Iodine Com- bination of Iodine with Phosphorus With Sodium Separation of Iodine from Bromine Hydriodic Acid Its Preparation Its Properties Difference between this Acid and Hydrochloric Acid . 55 LESSON XVI. Hydrofluoric Acid Its Preparation Etching Glass Silicon Flu- oride Its Preparation Its Properties Hydrofluosilicic Acid Its Preparation Filtration Use of the Wash Bottle . . 59 LESSON XVII. Methane Its Preparation Its Combustion in Air Products of its Combustion Explosion of Mixture of Methane and Oxygen Action of Chlorine upon Methane . 65 xii Contents. LESSON XVIII. PAGE Ethene Its Preparation Its Combustion in Air Its complete Combustion with Oxygen Its Action on Bromine and Chlo- rine ......... 68 LESSON XIX. Ethine Its Preparation Preparation of Cuprous Chloride Detection of Ethine Presence of Ethine in Coal Gas . LESSON XX. Luminosity of Flame Density of Products of Combustion Zones of Flame Extinction of Flame by Conduction of Heat by Metallic Surfaces . LESSON XXI. Sulphur Its Crystalline Forms Test for Sulphur Allotropy . 77 LESSON XXII. Sulphur Dioxide Its Preparation Its Bleaching Action Its Liquefaction Its Oxidation Its Action on Iodine Sulphur Trioxide Its Preparation Its Properties . . . -79 LESSON XXIII. Sulphuric Acid Its Properties Its Action on Sugar . . .85 LESSON XXIV. Sulphuretted Hydrogen Its Preparation Its Action on Metallic Solutions .... 86 LESSON XXV. Phosphoretted Hydrogen Its Preparation Its Inflammability . 88 Contents* xiii PART II. QUALITATIVE ANALYSIS. SECTION I. GENERAL PRELIMINARY OPERATIONS. PAGE Flame Reactions Bunsen Lamp Charcoal Splinter Reduction and Oxidation of Substances Films on Porcelain Flame Colours Coloured Glasses Spectroscopic Analysis Prelimi- nary Dry Reactions ........ 9 SECTION II. SYSTEMATIC QUALITATIVE ANALYSIS. Grouping of the Metallic Bases Group Reagents Special Tests for Members of Group I. Separation of Group I. . . .107 Special Tests for Members of Group II. and Separation of the Group in Special Tests for Members of Group III. and Separation of the Group . H9 Special Tests for Members of Group IV. and Separation of the Group 122 Special Tests for Members of Group V. and Separation of the Group 126 Special Tests for Members of Group VI. and Separation of the Group 128 Illustration of Separation of all the Groups in the Analysis of Fahl Ore .130 Tests for Sulphuric Acid and Sulphates 1 34 ,, ,, Hydrofluosilicic Acid and Silicofluorides . . -135 ,, ,, Phosphoric Acid and Phosphates . . . . . 135 ,, ,, Boric Acid and Borates 137 ,, Oxalic Acid and Oxalates 137 ,, ,, Hydrofluoric Acid and Fluorides . . . . .138 Sulphurous Acid and Sulphites 139 ,, ,, Silicic Acid and Silicates , . , . . .139 , Carbonic Acid and Carbonates 141 xiv Contents. PAGE Tests for lodic Acid and lodates 141 ,, ,, Thiosulphuric Acid and Thiosulphates . . . .141 ,, ,, Hydrochloric Acid and Chlorides ..... 142 ,, ,, Hydrobromic Acid and Bromides . . . .142 ,, ,, Hydriodic Acid and Iodides . . . . ... 143 ,, ,, Chlorides, Iodides, and Bromides, when occurring to- gether 145 ,, ,, Hydrocyanic Acid and Cyanides ..... 145 ,, ,, Nitrous Acid and Nitrites ...... 147 Hypochlorous Acid and Hypoohlorites . . . . 14 7 ,, ,. Hydrosulptiuric Acid and Sulphides- .... 148 ,, ., , Nitric Acid and Nitrates . .... 149 , ,, Nitrates and Chlorates, when occurring together . .150 ,, ,, Nitrogen in Organic Bodies . . . . . . 151 ,, ,, Chloric Acid and Chlorates . . . . . . 151 ,, ,, Perchloric Acid and Perchlorates . . . . . 151 ,, ,, Tartaric and Citric Acids . . . . . .152 ,, ,, Benzoic and Succinic Acids . . . . . . 153 ,, ,, Acetic and Formic Acids . . . . . . 153 Synopsis of Analytical Methods : Table for Preliminary Dry Tests 155 ,, ,, Flame Reactions by the Bunsen Flame . . .156 ,, ,, Solution of Substances . . . . . -157 ,, ,, Treatment of the Solution . .. . . .158 , , , , Separation of Group I. . . . . . 1 59 J, H 1 60 ,, HI 161 ,, IV 162 MM ,, V 163 VI 164 ,, ,, Preliminary Examination for Acids .... 165 ,, ,, Grouping of the Inorganic Acids .... 166 ,, ,, Separation of the Inorganic Acids .... 167 ,, ,, Examination of Insoluble Substances . . .168 ,, ,, Separation of Organic Acids . . . . .169 Contents. xv SECTION ill. DETECTION OF THE RARE ELEMENTS. PAGE Tests for Thallium 1 70 ,, ,, Palladium, Rhodium, Osmium, Ruthenium, Platinum, and Iridium . . . . . . . . .171 ,, ,, Molybdenum and Selenium . . . " . . . 173 ,, . Tellurium . . . . . . . . .173 ,, ,, Zirconium, Cerium, Lanthanum, Didymium, and Titanium . . . . . . . .174 ,, ,, Uranium and Indium ... ... 176 ,, ,, Vanadium, Lithium, Caesium, and Rubidium. . .177 Detection of the Rare Elements in the Systematic Course . . 1 78 SECTION IV. DETECTION OF POISONS. Detection of Phosphorus 182 ,, ,, Arsenic by Dialysis . . . . . . .183 ,, ,, ,, by Marsh's Process ..... 187 ,, by Fresenius and Von Babo's Process . .192 ,, ,, Mercury, Lead, and Copper ..... 195 ,, ,, Antimony and Zinc . . . . . . 195 ,, ,, Hydrocyanic Acid . . . . . . .196 ,, ,, Oxalic Acid . . . . . . . . 199 ,, Alkaloids by Method of Stas 200 ,, ,, ,, ,, ,, Uslar and Erdmann . . 202 Special Tests for Veratrine, Aconitine, Brucine, and Colchicine . 204 ,, ,, ,, Morphine and Strychnine ..... 206 ,, ,, ,, Quinine ........ 207 Detection of Opium . . . . . . . . . 208 Identification of Blood Stains ....... 209 SECTION V. EXAMINATION OF URINE AND URINARY CALCULI. Examination of Healthy Urine 2lo ,, ,, Abnormal Urine ...... 210 ,, ,, Urinary Calculi . . . . . . . 214 APPENDICES .219 QUALITATIVE CHEMICAL ANALYSIS AND LABORATORY PRACTICE. PART I. PREPARATION AND PROPERTIES OF GASES, LIQUIDS, AND SOLIDS. LESSON I. PREPARATION AND PROPERTIES OF OXYGEN. TAKE a few crystals of potassium chlorate, place them in a clean dry test-tube, and heat them gently over a small Bunsen flame (see list of apparatus in Appendix). The salt begins to spirt, then fuses. Now light a small splint of wood, blow out the flame so as to leave the wood just glowing at the point, plunge this into the tube in which you are heating the potas- sium chlorate ; but do not allow the wood to touch the fused salt in the tube. Note what takes place : the splint, which only glowed when introduced into the tube, now bursts into bright flame, with a slight explosion. Withdraw the splint, blow out the flame, introduce it again into the tube; the same brilliant light will be noticed. What does this teach us? -L-* B 2 Qualitative Chemical Analysis. That, by heating potassium chlorate, we have produced a substance having the property of causing an almost expiring flame to burn again more briskly than ever, which property, as we can easily determine, the potassium chlorate does not itself possess. This substance is oxygen gas. If this oxygen has been produced from potassium chlorate, then that salt must have undergone some change. Let us put this to the test. Take a few crystals of the chlorate, dissolve them in water in a test-tube (by shaking the tube, the mouth being closed by the thumb), and to this solution add a drop of a solution of silver -nitrate. Nothing seem- ingly takes place, the liquid remains clear. Take now the small quantity of potassium chlorate which you have heated in the test-tube, dissolve this also in water, and add a drop of silver nitrate solution ; at once a white solid forms in the liquid, and this on shaking settles down to the bottom of the tube, (such a solid substance, produced by the addition of one solution to another, or, in some cases, by passing a gas into a liquid, is called a precipitate). These different actions of silver nitrate show us that the potassium chlorate has been changed by heat. What we have after heating is potassium chlorate minus oxygen, which, as we saw, goes off as a gas (KC10 3 =KC1+0 3 ). In heating the potassium chlorate you will notice that it spirts, and gives up moisture, which, condensing on the colder part of the tube, is liable to flow back on to the hot portion, and so to crack the glass. Before preparing a quan- tity of oxygen it is therefore necessary to dry the salt. To do this, grind about 30 grams of potassium chlorate in a mortar, place it in a porcelain dish which is supported on a tripod over a very small flame, stirring it from time to time with a glass rod until it is dry. The temperature to which it is necessary to heat potassium chlorate before it parts with its oxygen is so high that the glass vessel containing the salt is very apt to crack, or at least to soften ; but by mixing with the chlorate a small quantity of an infusible substance, as Preparation of Oxygen. 3 sand, oxygen will be given off at a comparatively low tem- perature. To facilitate the decomposition of the chlorate, we generally use not sand, but manganese dioxide, which acts more readily. Take about 5 grams of manganese dioxide and set it drying, as you have done with the potas- sium chlorate. Meanwhile get ready an apparatus in which to prepare and collect the oxygen. Take a flask such as is described in the list of apparatus, No. i, clean and dry it ; to do this, pour a little water into the flask, add a few small pieces of filtering paper, rinse well, shake out the paper, rinse again with water, and let the flask drain ; then heat it gently over a flame, turning it round, and either suck or blow out the heated air by means of a piece of glass tubing ; select a good cork a very little larger than the neck of the flask, soften it (by wrapping it in a piece of paper, and rolling it several times under the foot upon the floor), and bore a hole in it about 6 mm. diameter, with a round file. (See Note i.) Choose now a piece of glass tubing about 85 cm. long and very slightly wider than the hole in the cork. Light an ordinary gas-burner, bring the tube at about 15 cm. from one end into the flame, holding it parallel with the broadest part (fig. i), and keep turning it round ; soon you will feel the tube soften. Now slowly bend it, as if you were making a crook like a shepherd's staff, turning it in the flame as much as possible, and not hurrying the opera- tion in the least. Some practice is required to make a neat bend ; but if the flame be good, if you turn the tube inces- santly, and if you bend it slowly, you will soon be able to conquer any little difficulty which at first may present itself. When bent, the tube should have the shape shown in fig. 2, No. i. At about 15 cm. or so from the other end make B 2 4 Qualitative Chemical Analysis. another bend in the opposite direction, but do not make this bend so sharp as the first (fig. 2, No. 2). In making this bend, hold the tube so that you may look along it, and then you will be able to make both bends in one plane. Now, by means of a three-cornered file, make a scratch on the tube about 10 cm. from the end (fig. 2, No. 2, c), and, by a sharp pull, break the tube at this point. Holding the tube in both hands, bring one end of it into a Bunsen's flame, the tube being inclined at an acute angle with the flame (see fig. 2, No. i) ; keep turning it round until just the edge of the tube begins to glow, then after a few moments (turning the tube all the while) withdraw it, when you will find that the FIG. 2. rough edge is now perfectly smooth ; do the same with the other end of the tube, and allow it to cool. The end a (see fig. 2) is now to be gently fitted into the cork. By this time the potassium chlorate and manganese dioxide will be dry; these are mixed together in a mortar, the mixture placed upon a piece of paper, and poured, by means of this, into the 'flask. Fit the cork with the bent tube into the flask and support it by a clamp (see fig. 3). To collect the gas, use the pneumatic trough and four gas bottles. The trough is nearly filled with water, in which a gas bottle is inverted so that the water may rush into it, the air escaping as the water enters. Some little Preparation of Oxygen. 5 management is required to fill the bottle completely, but by raising the mouth the bottle lying on its side beneath the water just above the surface, and then slowly de- pressing it, the last bubble of air may be forced out. When this is done, place the bottle mouth downwards to one side of the trough, while you fill the other bottles in the same way. Now place the flask on the retort-stand in such a position that the lower end of the delivery tube passes under the water just beneath the hole in the beehive FIG. 3. shelf of the trough. Everything being now ready (see fig. 3), gently heat the flask, using at first a small flame ; the air in the flask will be first of all expanded and driven out, bub- bling up through the water in the trough. When the bubbles begin t follow one another in rapid succession they may be tested by bringing a glowing splint of wood over the place where they stream up through the water. If the splint bursts into flame, then we may begin to collect the gas. To do this, move one of the bottles on to the beehive shelf, so that its mouth is over the opening in this shelf; the gas will 6 Qualitative Chemical Analysis. then rise into the bottle, displacing the water, which finds its way into the trough. When full, depress the mouth of the bottle somewhat further beneath the water, slip a small tray under it, then lift the bottle, standing mouth downwards, on the tray (which must contain a little water) out of the trough, and set it aside. Fill the other three bottles in a similar manner. In heating the flask while preparing the gas, so regulate the heat as to avoid any sudden rush of gas ; and whenever a sufficient amount of oxygen has been collected, remove the lamp and lift the end of the delivery tube out of the water, othenvise, in cooling, the water will rush back into the flask and crack it. The mass remaining in the flask may, when cold, be easily washed out with water. We will now proceed to examine the properties of the oxygen we have obtained. By the preliminary experiment with potassium chlorate heated in the test-tube we have learned that a burning body when plunged into oxygen burns with greatly increased activity. Oxygen is evidently a supporter of combustion. Experiment /. Take a small piece of phosphorus about tne size of a pea, dry it carefully between folds of filtering paper (see Note 2), and place it in the cup of a deflagrat- ing spoon, set fire to the phosphorus by bringing it for a moment into a gas flame, and plunge it into a bottle of oxygen ; a brilliant white light, almost insupportably bright, is produced, together with dense white fumes. (If the gas bottle be made of thick glass, it is advisable to dilute the oxygen in it with about one-third of its volume of air before burning the phosphorus, as the great heat may crack the Bottle. This may be done by depressing the bottle in the trough, allowing one-third of the oxygen to escape, and then lifting the bottle, mouth downwards, out of the trough, so that the water which flowed in when the oxygen escaped, may run out.) When the bottle is c6ol, remove the defla- grating spoon, put a little water into the bottle, and shake Properties of Oxygen. 7 it up ; the white fumes disappear, they are dissolved in the water. Taste a few drops of the solution thus formed you find it exceedingly sour or acid. Pour into the bottle a few drops of blue litmus solution (reagents list, No. 27) ; it turns red, showing the presence of an acid. What, then, has this experiment taught us ? (1) That substances burn in oxygen with great energy. (2) That a substance having totally different pro- perties from either oxygen or phosphorus is produced when these bodies combine together. The colourless gas oxygen, and the yellow wax-like solid phosphorous form, when che- mically combined, a light snow-like mass, which, when dissolved in water, gives rise to a solution possessing an intensely sour taste. Experiment II. Place a small piece of sulphur in the deflagrating spoon, set fire to it, and bring it into a bottle of undiluted oxygen ; it burns with a pale lavender-blue flame, considerably more brilliant than when it burns in air. After the combustion is over, remove the spoon, and note the pungent odour of the substance formed, also the seeming absence of anything in the bottle ; the product of combus- tion is an invisible gas. Add a little water, shake the bottle, and pour in a drop or two of blue litmus solution. By its action on the litmus you see that an acid is present. Experiment III. In the third bottle a small piece of charcoal is burned, in the spoon. Note the comparatively feeble light produced; the presence of the gaseous com- pound formed is shown (i) by its extinguishing a lighted taper when plunged into it ; (2) by its action on lime-water, which, when added and the bottle shaken, becomes turbid, owing to the gas in the bottle, known as carbon dioxide, 8 Qualitative Chemical Analysis. CO 2 , combining with the lime (lime-water being a solution of lime in water), and forming a substance, carbonate of lime, or calcium carbonate, insoluble in water, and therefore appearing as a solid, floating about in small particles in the clear liquid, and thus rendering it turbid. You have thus detected the presence of an invisible gas, by presenting to it something with which it could combine to form a new substance, having such characteristic pro- perties as to be easily recognisable ; you have thus applied a chemical test. You have learned from these experiments : (1) That oxygen supports combustion. (2) That the production of substances differing in properties from the substances which combine to form them is a characteristic result of chemical action. \ (3) The meaning of the term chemical test. The fourth bottle of oxygen is set aside, with its mouth downwards, in one of the small trays we shall have occasion to use it in Lesson IV. Note i. In boring a hole in a cork, do not forcibly drive the end of the file into the cork, but gently turn the file round, at the same time pressing it cautiously into the cork, until the hole is made ; take care that the hole be bored straight through, and not in a slanting direction. If you wish to enlarge the hole, you may easily do so by working the file round and round, filing away thin little bits of cork ; but see that you do this equally on all sides, otherwise the round glass tube will not perfectly fit the hole in the cork. Cork -borers, which are sold in sets, are very useful, making a neater hole than a file. ) Note 2. In working with phosphorus, be careful to keep it under water. To prepare a piece for Experiment L, take a little piece out of the bottle by means of a knife ; place it in a basin under water, and then cut off a piece of the required size ; dry this by pressing it several times quickly between folds of blotting or filtering paper. Preparation of Hydrogen. 9 LESSON II. PREPARATION AND PROPERTIES OF HYDROGEN. TAKE one or two grams of zinc, put them into a test-tube, and add a few drops of dilute sulphuric acid ; you notice an effervescence, bubbles of gas make their way through the liquid ; bring a lighted taper into the test-tube : a slight explosion takes place, and you see a momentary flash, as if something in the tube had taken fire. FIG. 4. You have here another instance of chemical action : the zinc has so acted on the sulphuric acid as to decompose or break it up, hydrogen gas, one of the constituents of the acid, being evolved. You must now proceed to prepare and collect a quantity of hydrogen, making use of the reac- tion you have just learned for this purpose. Take a flat-bottomed flask (similar to that represented in fig. 4), holding about 300 c.c.; select a cork, soften it, and bore in it two holes of such a size as to fit the bent tube you used in last lesson. In boring the holes, take care you do not make them too near the edges of the cork, nor too near one another, otherwise the cork will be sure to io Qualitative Chemical Analysis. crack when you attempt to fit it into the mouth of the flask. Into one of these holes you fit the bent delivery tube, and into the other a straight glass tube, terminating at its upper end in an open mouth-shaped funnel ; this funnel-tube is to be pushed through the cork, so that when fitted into the flask it reaches very nearly to the bottom. Take now about 30 grams of granulated zinc (see reagents list), put it into the flask, inclining the flask to one side, and gently sliding the zinc down the neck, taking care that it does not fall heavily against the bottom, else it will most likely crack the flask ; fit the cork into its place, and arrange the ap- paratus so that the delivery tube may reach under the shelf of the trough (fig. 4). Pour into the flask through the funnel-tube sufficient water to cover the zinc to the depth of about 6 mm. or so ; then add, also through the funnel, a small quantity of diluted sulphuric acid (one part acid to four water, previously mixed and allowed to cool), and shake the flask gently ; in a minute or two you will notice an effervescence ; gas begins to bubble up through the water in the trough ; after a few moments add a little more acid, so that a pretty rapid stream of gas may be obtained. Do not, however, add much acid at a time, otherwise the action will become violent, the liquid will get very hot, and will froth up through the funnel-tube ; should there be indication of this, pour a little water into, and also on to the outside of the flask, in order to cool it Take a test-tube, fill it with water in the trough, and bring it, mouth downwards, over the hole in the shelf whence the gas is issuing ; when it is full of gas, cover the mouth of it with the thumb (while still in the trough), lift it mouth down- wards out of the water, remove the thumb, and bring a lighted taper to the mouth of the tube ; if an explosion ensues, the hydrogen is not pure, it is still mixed with air ; repeat this experiment after the expiration of a minute or so, and do not begin collecting the gas in bottles until a small quantity in a test-tube does not explode when brought near Properties of Hydrogen. 1 1 a light, but takes fire and burns quietly. When you have satisfied yourself that the hydrogen is unmixed with air, proceed to collect four bottles of it, exactly as described in the last lesson. Be careful never to bring a light near a mixture of hydro- gen and air in a glass vessel, as if these gases be present in any quantity, and the vessel is not very strong, a dangerous explosion may occur. Let us now examine some of the properties of this gas hydrogen, and see what lessons it has to teach us. Experiment I. Take a bottle of hydrogen from the little tray, hold it mouth downwards, and apply a light to the mouth of the jar ; the gas takes fire, burning with a very pale non -luminous flame ; pass the taper further up into the jar, it is extinguished. Hydrogen therefore differs from oxygen in being itself combustible, but not (under ordinary circumstances) a supporter of combustion. You may natur- ally inquire, Why keep the bottle of hydrogen inverted ? The next experiment will answer this question. Experiment If. Take the second bottle of hydrogen, lift it from the tray, keeping it inverted, in the right hand, while in the left you hold, also mouth downwards, the bottle in which you performed Experiment I., containing now only air ; by depressing the top of the bottle containing hydrogen, and holding the empty bottle as if you were pouring from the lower one into it (see fig. 5), you can in a very FIG. 5. few moments decant all the hydrogen up- wards into the higher bottle. Set the bottle from which you have poured the hydrogen, mouth downwards, in the tray ; light a taper and bring it to the mouth of the second bottle, still held inverted in the left hand : a slight explosion ensues, and you see the pale lambent flame of burning hydrogen. Apply a light now to the mouth of the other bottle the taper burns quietly, as if in air, showing you that all the hydrogen has been 1 2 Qualitative Chemical A nalysis. poured out of this bottle. You learn then that hydrogen is much lighter than air, quickly rising through it. Had you held the bottle in Experiment I. mouth upwards, the light hydrogen would have escaped before you could notice its characteristic flame. Pour the liquid from the flask which you have used in these experiments into a small porcelain basin, evaporate it over a flame to about one-half or one-third its bulk, and set it aside ; when cool, you will find a mass of white crystals formed in the liquid ; this is zinc sulphate, the second product of the action of zinc on sulphuric acid, the first being the hydrogen you collected. The action is thus represented : Zn + H 2 SO 4 = ZnSO 4 + H 2 . You have learned from these experiments (1) That hydrogen is a combustible gas, burning with a feebly luminous flame. (2) That hydrogen is an exceedingly light sub- stance, so light that it can be poured upwards. (3) That hydrogen and air form an explosive mix- ture. (4) That the action of zinc on sulphuric acid is to produce an invisible gas, hydrogen, and a white crystalline solid, zinc sulphate. LESSON III. COMBINATION OF OXYGEN WITH HYDROGEN. MEANING ' OF THE TERMS ' COMBUSTIBLE ' AND ' SUPPORTER OF COMBUSTION/ Experiment I. Procure an ordinary soda-water bottle and a cork to fit it tightly ; fill it with water, pour out this water into a measuring glass you thus find the capacity of Combination of Oxygen with Hydrogen. 1 3 the bottle ; divide this by three, and now pour into the bottle one-third of the water which you know is required to fill it. With a file make a mark on the outside of the bottle on a level with the surface of the water inside. You have thus divided the bottle into two parts : one equal to one- third, the other equal to two-thirds of the whole. Again fill the bottle with water at the trough, invert it, and let it stand on the beehive shelf, with its mouth under water. You now bring to the side of the trough the bottle of oxygen which you prepared but did not use in Lesson I., also a bottle of hydrogen from last lesson. Lift the bottle of oxygen, with the tray on which it stands, into the trough ; when the FIG. 6. mouth of the bottle is beneath the surface of the water, with- draw the tray, gently depress the upper end of the bottle (held in the right hand), while with the other hand you hold the soda-water bottle so that the bubbles of oxygen as they escape may pass up through the water into it (see fig. 6). A little dexterity is necessary in thus decanting the gas up through the narrow neck of the soda-water bottle ; do not be too hasty, but allow the gas to pass up slowly and steadily. Fill the* soda-water bottle with oxygen up to the mark you made with the file, that is, one-third ; then set it on the beehive shelf while you again bring the tray under the mouth of the oxygen bottle and lift it from the trough. Decant (as you have just done with oxygen) hydrogen sufficient to entirely fill the soda-water bottle, and set aside 14 Qualitative Chemical Analysis. any hydrogen which remains. Quickly cork the soda- water bottle, shake it once or twice briskly, withdraw the cork, and apply a light to the mouth of the bottle a sharp, loud explosion instantly ensues. With the oxygen and hydrogen remaining, again fill the bottle, but this time vary the proportion of the gases put less oxygen and more hydrogen, or vice versa ; you will find that the explosion is less violent than in the first experiment. FIG. 7. The application of the light has caused chemical combi- nation to take place between the two gases, oxygen and hydrogen ; this combination is of a very violent nature, as testified by the loudness of the explosion. The product of the combination is water, which is composed cf oxygen and hydrogen in the proportion of one volume of the former gas to two volumes of the latter. From the small volume of the gases employed, the quantity of water produced is so minute that it seemingly adds nothing to the drops already adhering to the inside of the soda-water bottle. If, however, we were to fill a very large and perfectly dry bottle with the two gases mixed in the above proportion and explode the mixture, we Combustion cf Oxygen in Hydrogen. 1 5 should notice that a perceptible quantity of water formed as dew on the sides of the bottle. With the fourth bottle of hydrogen prepared in last lesson you have another experiment to perform. Experiment II. Set up again the flask with bent delivery tube for the preparation of oxygen, putting into it a mixture of about 15 grams of potassium chlorate, and 3 grams of manganese dioxide, as directed in Lesson I. Soften the end, fig. 7, of the delivery tube in the flame, and keep turning it round until the edges run together, and so make the orifice much narrower than it originally was. Support the flask on a stand, so that the end of the delivery tube points straight upwards, and is about 20 cm. from the table. (No trough is needed in this experiment.) Heat the flask gently, so as to produce a slow current of oxygen gas ; from time to time bring a smouldering splint of wood near the end of the tube, and when the nearly ex- piring flame just bursts again into brilliancy, you may con- sider the stream of oxygen to be issuing with sufficient rapidity. Now lift the bottle of hydrogen, mouth downwards, from the tray; apply a light to it, and while the hydrogen is- - burning, place the mouth of the jar over the end of the tube from whjch oxygen is issuing. As you do this, you notice that at the point where the oxygen meets the burning hydrogen a long flame of ignited oxygen shoots up within the bottle (fig. 7). If the oxygen is issuing in a rapid stream, there is danger of the flame produced by it being so large as to strike against the upper part of the bottle and crack it. You must, there- fore, carefully regulate the supply of oxygen. In this experiment you see that a gas which you had pre- viously regarded as a supporter of combustion can itself be made to undergo combustion. As combustion is a chemical com- bination attended with evolution of light and heat, this action takes place where the two substances which combine meet each other; but the oxygen rushes into an atmosphere of hydrogen, surrounding it on all sides ; the particles of oxygen, 1 6 Qualitative Chemical Analysis. as they are combining with those of hydrogen, are carried quickly forwards, and thus it is that the oxygen appears itself actually to burn within the hydrogen with the long narrow flame which you noticed. The relativity of the terms ' combustion ' and ' supporter of combustion ' may be shown with other gases than pure oxygen and hydrogen. Thus air may be made to burn in an atmosphere of coal gas. For this experiment you require a flask with three necks. To make this, take a round-bottomed flask, of about 300 c.c. capacity (a Florence flask suits admirably), and at the points a and b (fig. 8, No. i) heat it in the blowpipe flame, at first very gently, then gradually increasing the heat ; use a small flame, and direct it so as to heat to redness a small circle of glass at the point a ; when this is soft, suddenly blow in at the mouth of the flask, the glass at a is blown out (see fig. 8, 2) and breaks. Now, still using the blowpipe flame, fuse the rough edges of the opening thus made ; these melt and run together, and you obtain a round hole with smooth edges (fig. 8, 3) ; repeat this operation at the point b, a cork being fitted into the hole a while you blow out the glass. > You have now a flask with three necks. Choose a cork to fit, not very tightly, into the lower neck of the flask, and through this cork pass a piece of glass tubing about 10 cm. long, drawn to a tolerably fine point at its upper end. Combustion. 1 7 Fit a cork also into the side neck of the flask, with a glass tube passing through it, and arrange the two tubes so that the end of the one inside the flask may be just over that of the other (fig. 9). To the tube entering the flask at the side attach a caoutchouc tube coming from the gas supply, turn on the gas, and after the expiration of a minute F or two light it as it issues from the upper neck of the flask ; now cautiously draw out the lower cork with its tube, and when it is just out of the flask, apply a light to the neck ; the gas will take fire there ; as soon as it does so fit the cork into its place, and you will per- ceive a small pale flame playing round the point of the tube. The formation of this flame is accounted for by a similar reasoning to that used in explaining the burning of oxygen in hydrogen ; in this case air takes the place of oxygen, and the atmo- sphere of hydrogen is replaced by one of coal-gas. In this lesson you have learned : (1) That oxygen and hydrogen unite together violently when brought near a flame. (2) That the union of two volumes of hydrogen with one volume of oxygen gives a louder explosion than any other proportionate mixture of these two gases. (3) That water is composed of oxygen and hydro- gen in the above proportion, viz., two volumes of hydrogen and one volume of oxygen. (4) That the terms ' supporter of combustion/ and ' combustile,' are merely relative, and denote no absolute property of bodies. 1 8 Qualitative CJiemical Analysis. LESSON IV. PREPARATION AND PROPERTIES OF NITROGEN. THE gas nitrogen exists already made in the air ; in order to obtain it, you have only to take away another gas oxygen with which it is mixed. Fill the trough to the depth of about 3 cm. with water, and place in it an ordinary white plate. Into this plate pour a little water coloured blue by the addition of litmus solution. (See fig. 10.) Float a small porcelain dish, about 5 cm. diameter, on the water : the lid of a porcelain crucible, fastened to a piece FIG. 10. of wood of sufficient size to float it, does very well. Cut a little piece of phosphorus, attending to the directions given in Lesson I., dry it, place it on the dish, and set fire to it by touching it with a hot wire. Have at hand a large stoppered bottle, holding about 750 c.c. Take out the stopper, and place the bottle cautiously over the dish containing the burning phosphorus. You notice that as the phosphorus burns, the water rises slightly inside the bottle, showing that something is being taken away from the enclosed air. That it is the oxygen which is thus taken up by the phosphorus, is evident from the fact that the blue colour of the water gradually changes to red. This, you remember (Lesson I.), is owing to the formation of an acid, the product of the union of phosphorus and oxygen. When the combustion is over, and the bottle is cool, fill up the trough with water (take care that the bottle does not Preparation of Nitric A cid. 1 9 upset as you do this), and decant the air or gas into two gas bottles (see Lesson III.). Experiment /. Plunge a lighted taper into one of the bottles ; the flame is at once extinguished, and the gas does not take fire. Nitrogen therefore is incombustible, and is a non-supporter of combustion. Experiment II. Into the other bottle pour a few cubic centimetres of clear lime-water, close the bottle with the palm of the hand, and briskly agitate it. The lime-water is not rendered turbid. This test serves to distinguish nitrogen from carbon dioxide, which, as you learned from Lesson I., extinguishes flame, but gives a precipitate with lime-water. You learn then (1) That air contains oxygen and nitrogen. (2) That by burning a combustible substance in a confined space of air, the oxygen is with drawn (the combustible uniting with it), and nitrogen remains. (3) That this nitrogen possesses no very distinc- tive qualities, being neither combustible, nor supporting combustion. LESSON V. PREPARATION AND PROPERTIES OF NITRIC ACID. CHOOSE a stoppered retort, capable of holding about 250 c.c., having a tolerably long beak ; clean and dry it. Weigh out 30 grams of potassium nitrate, place it on a small piece of paper turned up at the edges, so as to form a kind of little trough, and by means of this transfer it to the retort, taking care that none of it gets into the neck of the retort (see fig. u). We act on this nitre with sulphuric acid; the equa- tion expressing this reaction is c 2 2O Qualitative Chemical Analysis. KNO 3 + H 2 SO 4 = HNO 3 + KHSO 4 that is to say, 39 + 14 + 48 = 101 parts by weight of potassium nitrate are decomposed by 2+32 -h 64 = 98 parts by weight of sulphuric acid; the product being i + 14 + 48 = 63 parts by weight of nitric acid. Calculate then the amount of strong sulphuric acid re- quired to decompose the 30 grams of nitre, weigh out this amount in a small beaker, and pour it into the retort through a small funnel passing well into the body of the retort through the opening at the neck. Put in the stopper and support the retort, with wire gauze beneath it, on one ring of a retort-stand, bringing another ring over the neck. Clean and dry a small flask, the neck of which will permit the FIG. xx. beak of the retort to be passed through it ; support it on the beehive shelf, and fill the trough with water, so that the flask may be pretty well covered, but take care that no water gets into it. The apparatus has now the appearance shown in Fig. 12. Gently heat the retort : an action evidently goes forward ; after a little time brown fumes are evolved, and drops of liquid form on the sides of the neck, and trickle slowly down it into the small flask, or receiver, which being kept cool by the water surrounding it, condenses the nitric acid, which in the heated retort is in a gaseous state. In the receiver a brownish-yellow heavy liquid, fuming Properties of Nitric Acid. 2 1 in the air, gradually accumulates ; this is strong nitric acid, which we will now examine. When you have removed the light, pour out the semi- liquid contents of the retort, consisting chiefly of hydrogen potassium sulphate (HKSO 4 ), into a small basin. After cooling and solidifying, break up this salt into little pieces, and preserve it in a stoppered bottle. You already know what is meant by a chemical test. In the laboratory we often have occasion to detect this sub- stance nitric acid, and to do this we use certain chemical tests. Experiment I. Pour a little of the acid into a test-tube FIG. 12. add a few drops of water, and then put into the tube a littie slip of copper foil ; you notice that a violent action ensues, a dark reddish-brown gas is given off, and the liquid becomes more or less gre*en in colour. The production of these red fumes when a piece of copper foil is brought into contact with a liquid suspected to be nitric acid, is one proof that the liquid is nitric acid. The red-coloured gas consists chiefly of nitrogen te- troxide, NO 2 8HNO + Cu = 2NO + 3 The NO thus formed, in contact with air takes up 22 Qualitative Chemical Analysis. another atom of oxygen, forming the ruddy-coloured gas NO 2 . But we have by the production of these same ruddy fumes, and the application to them of another chemical test, a much more delicate means of detecting the presence of small quantities of nitric acid. Experiment II. Take a few crystals of ferrous sulphate and dissolve them in a little cold water, in a test-tube. Into FIG. 13. the test-tube used in Experiment I. pour a few drops of nitric acid, so as to cause a fresh evolution of gas. Now hold the two tubes so that the ruddy fumes may fall into that containing the ferrous sul- phate solution (see fig. 13) ; the clear solution becomes rapidly darkened in colour, until it is nearly black; this darkening effect of the oxides of nitrogen, when brought into contact with ferrous sulphate solution in the cold, is the second and most delicate test for the presence of nitric acid. (Boil the dark brown solution in ferrous sulphate ; you see that the colour is almost entirely discharged. You now perceive why directions have been given to apply this test in cold solutions.) To carry out the test Experiment III. Make a solution of nitre in a little water in a test-tube ; add to this a few crystals of ferrous sulphate. Shake the tube, incline it to one side, and cau- tiously pour a few drops of strong sulphuric acid down the side of the tube, so that the heavy acid may sink to the bottom, and there form a separate layer. At the point of contact of the two layers you will notice a dark brown- coloured ring : this is proof of the presence of nitric acid ; it is nothing else than the dark liquid you produced in the last experiment by decanting nitrous fumes into a ferrous sul- phate solution. The reaction which goes on in the tube is as follows : The sulphuric acid acts on the nitre, nitric acid and potassium sulphate are formed ; part of the ferrous sulphate acts on the nitric acid, robbing it of some of its Preparation of Nitrogen Monoxide. 23 oxygen, ferrzV sulphate and lower oxides of nitrogen are produced ; the latter dissolve in the excess of ferrous sul- phate, and this solution, as you know, has a dark brownish- black colour. In applying the test, be careful to have all the solutions perfectly cold ; by pouring the acid gently down the side of the tube, you do not allow it to mix with the liquid, because if it did so, heat would be produced, and the dark colour destroyed, as you learned in Experiment II. In this lesson you have learned (1) How to conduct a process of distillation. (2) That by the action of sulphuric acid on potassium nitrate, nitric acid is produced. (3) That this acid is a heavy, slightly coloured liquid, fuming in the air. (4) What are the tests for nitric acid, and what is the mode of their application. LESSON VI. PREPARATION AND PROPERTIES OF NITROGEN MONOXIDE (NITROUS OXIDE). TAKE the nitric acid remaining from last lesson, put it into a porcelain basin, dilute it with a little water, and add ammonia to it (stirring with a glass rod after each addition of ammonia), until a drop taken on the end of a rod just ceases to redden blue litmus paper. Set the basin on a piece of wire gauze resting on a tripod- stand over a flame, and evaporate down until the liquid becomes slightly viscid, and no longer exhibits signs of ebullition. During this evaporation add from time to time a few drops of ammonia, otherwise the solution becomes acid, and when you heat the ammonium nitrate formed you find red nitrous fumes produced. Set the basin aside as the liquid cools it 24 Qualitative Chemical Analysis. becomes solid. When quite cold, break up the solid sub- stance in the basin into small pieces. In this process you have neutralised the nitric acid by means of ammonia, the acid and alkali have combined to- gether, the resulting new substance being ammonium nitrate the white salt in the basin. The substance produced by such a union of an acid with a base is called a salt. As this salt has a definite chemical composition, there must be a point reached, in adding ammonia to the acid, at which all the acid present is taken up by the ammonia ; this is the point of neutralisation. Put into a flask, which can be fitted with a delivery tube (that used in the preparation of oxygen may be employed), 10 grams of the ammonium nitrate which you have just made. Set the flask, fitted with its cork and tube, on the retort-stand, and arrange the trough in the usual manner, but use warm water instead of cold. Heat the flask gently until the salt fuses, then gradually increase the heat until the fused ammonium nitrate begins to decompose with effervescence, and bubbles of gas succeed each other rapidly through the water in the trough. Allow a few minutes to elapse, then begin to collect the gas ; fill three bottles, and set them aside on the small trays. In heat- ing the flask, do not let the temperature get too high ; if you see many white fumes appearing in the flask especially towards the close of the operation -the heat must be mode- rated ; but do not withdraw the lamp entirely, or, as the flask cools, the water may rush back from the trough into it, and crack it. By the action of heat ammonium nitrate is decomposed, nitrogen monoxide is given off, and water remains ; you may see this water condensing in the neck of the flask, and trickling down the sides NH 4 NO 3 = N 2 O + 2H 2 O. This nitrogen monoxide is slightly soluble in cold water, but much less so in hot water, hence the reason for using warm water in the trough. Properties of Nitrogen Monoxide. 25 Experiment /.Lift one of the bottles from the tray, set it, mouth upwards, on the table, and plunge into it a lighted taper ; the flame burns more brilliantly, but the gas itself does not take fire. Do this experiment quickly, and immediately replace the bottle, inverted, on the tray. Experiment //.For this experiment you must pass the deflagrating spoon through a cork of a size to fit the mouth of the bottle - } below the cork on the spoon is fitted a small copper or tin plate, which prevents the burning phosphorus from setting fire to the cork. (See fig. 14.) Cut and dry a small piece of phosphorus, place it on the deflagrating spoon, set fire to it, and plunge it into the jar of gas used in the last experiment, fitting FlG 14> the cork on the spoon into the bottle. The phosphorus burns very brilliantly, with almost as bright a light as when it burned in oxygen. This confirms the teaching of the last experiment. When the fumes pro- duced in this experimenthave somewhat subsided, plunge a lighted taper into the jar ; it is extinguished, the gas behaves therefore as nitrogen does : now pour a little blue litmus solution into the bottle, close the mouth with the pain, of the hand, and shake well; the litmus is reddened, therefore an acid has been qroduced in this ex- periment. This result agrees with that obtained by burning the phosphorus in pure oxygen (Lesson I.) or in air (Lesson IV.). But there is a difference between the powers of sup- porting combustion possessed by this gas and oxygen. Experiment III. Place a small piece of sulphur on the spoon, set fire to it, but let it be only just lighted anb no more ; now bring it into the second bottle of nitrous oxibe : the flame is extinguished. Had you employed oxygen in this experiment, you know that the sulphur would have burned with increased brilliancy. 26 Qualitative Chemical A nalysis. These combustions in nitrous oxide are due to the fact that the body burning decomposes the gas, taking to itself the oxygen ; but as there is a large quantity of nitrogen pre- sent, this dilutes the oxygen, and so the combustion is less violent than if it took place in oxygen alone. The oxygen and nitrogen being held together chemically, the low tempe- rature of the burning sulphur was not sufficient to dissolve their union, the sulphur could get no oxygen, hence its flame was extinguished ; but if you heat the sulphur con- siderably above its melting-point before plunging it into the gas, it will burn brilliantly. A mixture of oxygen and nitrogen would diminish the intensity of combustion like the oxide of nitrogen ; but to show the difference between such a mixture and nitrous oxide we will perform another experiment. Experiment IV. Pour a little cold water quickly into the third bottle of the gas, close the mouth with the hand, and agitate briskly ; invert the bottle, still keeping the hand over the mouth, and bring it thus beneath cold water in a basin. Now withdraw the hand : you notice that the water rises in the bottle, thus showing that you have dissolved some of the gas in the water you added. Again slip the hand beneath the mouth of the bottle, lift it, containing water, out of the basin, agitate briskly and replace it in the basin as before ; the water rises further in the bottle. Repeat this agitation until the water nearly fills the bottle. You now perceive how uneconomical it would have been to have collected the gas over cold water. This solubility in water also serves to dis- tinguish the chemical compound of oxygen with nitrogen from a mechanical mixture of these gases which would not dissolve in water to the same extent. You learn in this lesson (1) By what reaction nitrous oxide is produced. (2) That this gas has the power of supporting- com- bustion, and in what way it does this. Properties of Nitrogen Dioxide. 27 (3) That there is a difference between this gas and oxygen in their respective powers of supporting combustion. (4) That there is a difference between a mechani- cal mixture and a chemical compound. (5) That this gas is soluble in cold water. (6) What is the meaning of the terms ' neutralisa- tion ' and ' salt.' LESSON VII. PREPARATION AND PROPERTIES OF NITROGEN DIOXIDE (NITRIC OXIDE). INTRODUCE about 15 grams of copper in small pieces into a flask which is fitted with a delivery and funnel tube in the manner represented in fig. 4. Mix 30 c.c. of water with the same amount of strong nitric acid, and pour about three- fourths of this mixture on to the copper clippings through the funnel tube. Action evidently goes forward in the flask, for it is almost immediately filled with red vapours, and bub- bles of gas make their way through the water in the trough ; the red vapours in the flask soon however almost entirely disappear. Now begin to collect the gas which is coming over, and fill four bo.ttles with it. This gas is produced by the above action without heating the flask. Should the action become too violent, pour a little cold water on the outside of the flask ; if the stream of gas slackens, add a little more of the dilute nitric acid. Experiment I. Plunge a lighted taper into one of the bottles; the taper goes out, and the gas does not take fire : you notice, however, that ruddy fumes appear in the bottle. The ibrmation of these will be explained by the fourth experiment. Experiment II. Get ready a small piece of phosphorus on the spoon, light it, and plunge it, immediately it begins to 28 Qualitative Chemical Analysis. burn, into the second bottle of the gas ; the phosphorus is extinguished. Nitric oxide does not support combustion as nitrous oxide does. If you repeat this experiment, allowing the phosphorus to burn briskly for a little time before you bring it into the gas, holding it for a few moments in the Bunsen flame, it will burn with increased brilliancy in the nitric oxide. You thus see that the temperature at which nitric oxide is decomposed and made to part with its oxygen is considerably higher than that at which nitrous oxide is similarly split up ; the latter therefore much more readily supports combustion than the former gas. Experiment III. Into the second bottle of nitric oxide plunge a piece of brightly-burning sulphur, held in the defla- grating spoon : it is extinguished. In nitrous oxide under the same circumstances the sulphur continues to burn. Experiment IV. For this experiment you will require a small bottle of oxygen (make this as directed in Lesson I., using a smaller flask, and about 10 grams of potassium chlorate with 2 grams of manganese dioxide). Decant about one-fourth of the nitric oxide contained in the third bottle into another gas bottle, by means of the trough, and very slowly pass up into this a little oxygen. As each bubble of oxygen comes into contact with the nitric oxide, brown ruddy fumes are produced. After the addition of a small quantity of oxygen, shake the bottle containing the mixed gases (taking care not to let its mouth get above the water, else air will rush in) ; the water rises in the bottle, showing that gas is being dissolved. Continue the addition of oxygen, and at intervals shake the bottle ; you find that at last it is entirely filled by the water. You would naturally expect that by the addition of one gas to another, the volume of gas would be increased ; in this case, however, it is diminished until it is actually nil. The reason is that the oxygen combines with the nitric oxide, forming nitrogen tetroxide, NO 2 , a gas of a brown colour hence the brown fumes in the flask when you prepared nitric oxide, and in Properties of Nitrogen Dioxide. 29 the bottle of this gas when you exposed it to the air in bringing the taper into it. This gas is very soluble in water, so that as fast as it was produced in the last experiment, it was dissolved. If then you add this gas nitric oxide to a measured quantity of a mixture of oxygen and nitrogen, these ruddy fumes will be produced ; if you now shake up with water, the fumes will be dissolved, and a contraction in the bulk of the gases will ensue ; by measuring this contrac- tion you may determine how much oxygen was present in the original mixture. On this principle analyses of air were formerly made. To illustrate the method of carrying out such analyses we will try Experiment V. Take a glass tube about 30 cm. long and 2 cm. in diameter, divide it into five equal parts, each part corresponding to the contents of a smaller tube i cm. diameter and 14 cm. long ; mark the divisions on the out- side of the large tube by slipping over it small india-rubber rings. Pour water into the large tube, so that when inverted over the trough the water shall reach to the first ring FlG - IS - (see fig. 15); set the tube on the beehive shelf, and fill the smaller tube, over the trough, with nitric oxide; pass this into the larger tube, again fill the smaller tube with nitric oxide, and again pass this into the larger, in which you now have five volumes of air and twovolumes of nitric oxide ; shake this tube briskly; the oxygen of the air forms with the nitric oxide, nitrogen tetroxide, which is dissolved in the water. Add a few more bubbles of nitric oxide ; if no red fumes 3O Qualitative Chemical Analysis. are formed, the, reaction is ended ; again shake the tube and depress it so that the water inside and outside the tube may be at the same level ; you find that the air or gas in the tube now occupies only four volumes one volume of oxygen has therefore been taken away. Hence you conclude that five volumes of air contain one volume of oxygen. Pour the liquid remaining in the flask used in preparing the nitric oxide into a porcelain basin, evaporate it nearly to dryness in a draught chamber, and set it aside. After some time you notice a blue solid substance formed in the basin this is copper nitrate, produced by the action of the nitric acid on the copper: it was kept in solution by the excess of dilute nitric acid which you have evaporated off. From these experiments you learn (1) What is the method of preparing nitric oxide. (2) What is the behaviour of this gas towards combustible bodies. (3) That a high temperature is required to de- compose this gas. (4) That with oxygen, nitric oxide forms a brown- coloured gas nitrogen tetroxide very soluble in water. (5) That the formation of this nitrogen tetroxide by adding nitrogen dioxide to oxygen in a systematic manner may be made available for the analysis of air. LESSON VIII. PREPARATION AND PROPERTIES OF AMMONIA. IN this lesson you have to deal with a gas which is so soluble in water that it cannot be collected over the trough. It differs much in weight from air ; we can therefore use, so Preparation of Ammonia. 31 to speak, an air trough in collecting the gas. This trough is the atmosphere around us ; a gas bottle is already filled and standing in this trough; but as the gas to be collected is lighter than air, the bottle must be inverted, so that when the gas passes upwards into it the heavier air may be driven out at the mouth which opens downwards. Mix a few grams of ammonium chloride with about an equal amount of lime, heat this mixture gently in a dry test- tube ; you recognise the well-known smell of ammonia. Repeat this experiment, using a little caustic soda instead of lime ; the same effect is produced. Moisten a small piece of red litmus paper (reddened by holding it for a moment in the fumes coming from a bottle of nitric acid), and hold it over the test-tube, it is changed to blue again ; warm it gently, the blue colour disappears. Weigh out 10 grams of ammonium chloride (sal ammoniac), and powder it in a mortar ; also weigh out 20 grams of powdered quicklime. Choose a flask of the same shape as that used in Lesson I. and a cork to fit it, and bore in the latter a neat round hole ; take a piece of glass tubing about 30 cm. long, bend it at right angles, the length of the smaller limb being 5 cm. ; at a distance of 10 cm. from this bend make another in the same direction, and let the third limb of the tube be 15 cm. long. The smaller limb of this tube is fitted into the cork of the flask. Into a small wide-mouthed bottle fit a good cork having two holes bored in it, through one of which passes a piece of tolerably wide tubing (4 or 5 cm. long), within which the longer limb of the first tube passes nearly to the bottom of the small bottle. The shorter limb of a third tube, similar to the first, except that the bends are in opposite directions, is fitted into the second hole in the cork of the small bottle, into which you now pour about 20 c.c. of ordinary ammonia solution. Mix the sal ammoniac with two-thirds of the total quantity of the lime in a mortar, transfer the mixture to the 32 Qualitative Chemical Analysis. flask, and then add the remainder of the lime; fit the cork into the flask, and put the pieces of apparatus together, the flask standing over wire gauze on a tripod or retort-stand, while the small bottle is supported on a block of wood. A perfectly dry gas bottle is supported, mouth downwards, on another retort-stand, so that the tube leading from the small bottle may pass nearly to the top of it. The apparatus is shown in fig. 16. By the application of a gentle heat to the flask, the sal FIG. 1 6. ammoniac and quick lime are caused to react on one another, with the production (i) of ammonia the first portions of which are dissolved by the water in the small bottle (this at first not being quite saturated), and which is afterwards collected in the gas bottle ; (2) of water which is absorbed by the upper layer of quick lime ; and (3) of calcium chloride a white solid which remains in the flask mixed with a little undecomposed quick lime and sal am- moniac, CaO + 2NH 4 C1 = CaCl 2 + 2NH 3 + H 2 O. Properties of Ammonia. 33 The liquid in the small bottle serves to wash the gas. The ammonia passes upwards into the gas bottle, and gathering near the top, gradually drives out the air, until at last the bottle is filled with ammonia ; when this is done, the gas will of course flow over the edges of the mouth of the bottle. You may ascertain that this is taking place by holding a piece of moistened turmeric paper close to the outside of the bottle, a little above the mouth ; it will be turned brown, showing the presence of ammonia. Now remove the bottle from the re tort -stand, and set it mouth downwards on a glass plate. Fill in this way three bottles with the gas. Experiment I. Pass a lighted taper into one of the bottles of ammonia, supported, mouth downwards, on a retort-stand ; you notice a momentary flash of greenish, coloured flame round the taper, which is then immediately extinguished. Ammonia tends to burn when a flame is brought near it. By passing ammonia mixed with oxygen through a glass tube, and applying a light to the issuing gas, it will burn briskly. Experiment II. Choose a piece of tubing about 100 cm, long and ij cm. in diameter ; support this by means of a clamp, so that the end of the delivery tube from a flask con- taining a little strong ammonia solution may pass a little way into it, and let it be slightly inclined at an angle with the surface of the table. Fit up the oxygen apparatus used in Lesson I. (using smaller quantities of potassium chlorate and manganese), and let the end of this delivery tube also pass into the wide tube see fig. 17. Heat the two flasks so as to produce a gentle stream of oxygen, and also of ammonia ; you will soon have a mixture of these two gases issuing from the upper end of the wide tube. On applying a light to the opening, the ammonia burns with a long greenish flame. Experiment IIL Pour 30 or 40 c.c. of strong ammonia solution into a flat-bottomed flask capable of holding half a D 34 Qualitative Chemical A na lysis. litre ; wind a piece of thick platinum wire, about 30 c.m. long, round a glass tube so as to form a spiral, and arrange this on a glass rod so that it shall hang into the flask to within a centimetre or so of the ammonia solution. Make the end of this spiral red-hot in the flame of a Bunsen lamp, and then plunge it into the flask. You see that it continues to glow, while the flask gradually becomes filled with white fumes. In the last experiment you caused ammonia to combine rapidly with oxygen ; in this a similar combination takes FIG. 17. place, but much more slowly. Under the influence of the heated platinum, the oxygen of the air .combines with the ammonia, forming nitrous acid, which in turn reacts on the excess of ammonia and combines with it to form the salt ammonium nitrite, which you see appearing as white fumes in the flask. The next experiment will show you the formation, in a somewhat similar manner, of another ammonium salt. Experiment IV. Take 3 or 4 c.c. of strong hydrochloric acid, pour it into a small flask, set this on wire gauze on a tripod, and heat the solution. While the fumes of hydro- Preparation of Carbon Dioxide. 3 5 chloric acid are coming off, bring the second bottle of am- monia, mouth downwards, over the flask ; it is immediately filled with dense white fumes. The hydrochloric acid com- bines with the ammonia, forming a new substance, ammo- nium chloride ; such a union of an acid with a base is, as you already know, called a salt. Experiment V. Lift the remaining bottle of ammonia, mouth downwards, standing on a glass plate, into the trough filled with water, withdraw the plate and shake the bottle ; the water will quickly rise until it nearly fills the jar, show- ing the great solubility of ammonia in water. In this lesson you have learned (1) That gases soluble in water may be collected by displacement, and how to collect such gases. (2) By what reaction ammonia is produced. (3) What is the action of this gas on vegetable colouring matters. (4) That ammonia is a combustible gas, especially when supplied with a large amount of oxygen ; that it also may be made to un- dergo slow combustion. (5 ) That ammonia is very soluble in water. (6) That ammonia gas is much lighter than air. (7) That ammonia readily combines with certain acids, producing thereby salts of these acids. D 2 Qualitative Chemical Analysis. LESSON IX. PREPARATION AND PROPERTIES OF CARBON DIOXIDE. FIT a flat-bottomed flask with a cork, through which pass a funnel tube and a delivery tube, this latter being bent twice at right angles, so that the shorter limb may be about 8 cm., and the longer 20 cm. in length. Weigh out 30 grams of marble ; break it up into pieces the size of a pea, and FIG. 18. place these in the flask (remembering the precautions given in Lesson II.), fit the cork with the tubes in its place, and set the flask so that the longer limb of the delivery tube may dip nearly to the bottom of a gas bottle standing on a block of wood, and having its mouth covered with a piece of paste- tyoard through a hole in which the tube passes (fig. 18). Pour a little water into the flask, and then some strong hydro- chloric acid; a brisk effervescence ensues, a gas being evolved. If after the expiry of a few moments you plunge a lighted taper into the gas bottle, you will find that as it approaches the bottom of the bottle it goes out; there is evidently some Properties of Carbon Dioxide. 37 gas collecting here, and as it gathers at the bottom of the bottle, it must be a heavy gas. The atomic weight of carbon dioxide, CO 2 , is 44 ; it is therefore % 4 = 22 times heavier than hydrogen. But hydrogen is 14*47 times lighter than air, carbon dioxide is therefore about ij times heavier than air. Continue the evolution of gas for some time, and again bring the lighted taper into the jar; as soon as the flame comes within the jar it is extinguished ; you have thus filled the bottle with a gas heavier than air by downward, displace- ment. Fill three bottles and a small flask capable of holding about 100 c.c. with the carbon dioxide, cover them with well- greased glass plates, and set them aside. Experiment I. Pour a little clear lime-water into a small beaker, dip the end of the delivery tube into this liquid, and allow the carbon dioxide to bubble through it; you very soon perceive that the clear solution becomes turbid the reason for this has been explained in Lesson I. Continue the pas- sage of the gas, the turbidity after a time disappears. When this occurs, withdraw the delivery tube, and boil the liquid in the beaker; the turbidity soon again makes its appearance. The disappearance of the turbidity on the continued passage of the gas is owing to the solution of the calcium carbonate in the carbonic acid ; on boiling, the solution is decomposed, carbon dioxide is evolved, and the insoluble calcium car- bonate is reprecipitated. Experiment II. Pour a little blue litmus solution into a small flask, and pass the carbon dioxide through this liquid. You notice that it becomes a wine-red colour, differing entirely from the pure red produced by the action of nitric or hydrochloric acid upon litmus solution. Boil the reddened liquid, it becomes blue again. Now set aside, for further use, the flask employed in the preparation of the gas. Experiment III. Place on the table a little piece of lighted taper stuck into a cork, withdraw the glass plate from the mouth of one of the bottles of carbon dioxide, and 38 Qualitative Chemical Analysis. gradually invert the bottle as if you were pouring from it on to the taper (fig. 19). The lighted taper soon goes out. This experiment confirms what you have already learned while preparing this gas, viz. that it extinguishes flame, and that it is heavier than air. Experiment IV. Put a small newly- \cut piece of sodium, about the size of a pea, into the flask containing carbon dioxide, and gently heat the flask the sodium melts, and then takes fire ; cover the mouth of the flask with the thumb, and agitate it, so as to move the burning sodium about from place to place. When the sodium has ceased to burn, allow the flask to cool, and then pour a little water into it ; you notice black soot-like flakes floating about in the water. The carbon dioxide has been broken up into its elements by the burning sodium, which seized upon the oxygen so greedily as to cause evolution of light and heat, while the carbon appeared in the free state. Carbon dioxide, in re- spect of its power of supporting combustion, may be classed with nitric oxide. Experiment V. Pour a little water into the second bottle of carbon dioxide, close the mouth of it with the hand, and shake briskly ; bring the bottle, inverted, under the water of the trough, and withdraw the hand : the water rises in the jar. Now place the hand as before, and lift the bottle out of the water ; pour into it a few drops of clear lime-water, and shake several times ; you notice that the liquid becomes turbid, which, as you know, is proof of the presence 01 cafbon dioxide. You have therefore dissolved this gas in water. Experiment VI. Into the third bottle of carbon dioxide pour a little caustic potash or caustic soda solution, close the mouth of the bottle with the hand, and shake briskly ; Preparation of Carbon Monoxide. 39 bring now the bottle, inverted, under the water in the trough, and withdraw the hand. By the fact that the water rushes into the jar, you learn that the gas has been absorbed by the caustic potash. Pour the liquid in the generating flask into a porcelain basin, and evaporate it over a flame to complete dryness, stirring the mass from time to time with a glass rod, so as to have all parts equally heated ; do not allow it to gather into a hard cake, else you will have difficulty in getting it out of the basin. Put this solid substance, when quite dry, into a wide-mouthed stoppered bottle, labelling it 'calcium chlo- ride.' This calcium chloride is the second product of the action of hydrochloric acid on marble (calcium carbonate) : CaCO 3 + 2HC1 = CaCl 2 + H 2 O + CO 2 . You have learned then (1) How to collect a heavy gas by downward dis- placement. (2) That marble, when acted upon by an acid, gives off the gas carbon dioxide, CO 2 . (3) That this carbon dioxide is a heavy gas. (4) That it extinguishes flame. (5) But that certain substances can, at high tem- peratures, decompose this gas, taking its oxygen to themselves. (6) What is the action of carbon dioxide on lime- water and on litmus solution. (7) That carbon dioxide is soluble in water, and how to recognise it in this solution. (8) That this gas is absorbed by caustic potash or soda solution. 40 Qualitative Chemical A nalysis. LESSON X. PREPARATION AND PROPERTIES OF CARBON MONOXIDE. PUT a few crystals of oxalic acid into a dry test-tube, drench them with strong sulphuric acid, and heat gently over a flame : you notice an effervescence in the tube ; continue heating for a few moments, then bring a lighted taper to the mouth of the tube : a pale lavender-blue flame appears for an instant, passes down the tube, and goes out. Pour a little clear lime-water into another test-tube, and decant the gas (see Lesson V.) from the first tube (heating this all the while) into the lime-water ; this soon becomes turbid : carbon dioxide is therefore present. But carbon dioxide is not an inflammable gas ; we have therefore two gases produced in this reaction : one of them is carbon dioxide, the other carbon monoxide. Arrange the apparatus in which you prepared hydrogen (Lesson II.), setting the flask on a retort- stand. Place 10 grams of crystallised oxalic acid in the flask, and add, through the funnel tube, about 15 grams of strong sulphuric acid ; heat the flask gently, and after the gas has been coming off for a few minutes, begin to collect it over the trough. Fill a bottle with the mixed gases, and set it aside, mouth downwards, on a small tray. (Set the generating flask at once in the draught chamber, carbon mon- oxide being a very poisonous gas.) Experiment I. Pour about 20 c.c. of a strong solution of caustic potash rapidly into the bottle, close its mouth with the hand, and shake briskly several times. You feel by the pressure of the outside atmosphere on the hand that some gks has been absorbed by the potash within the bottle. You have already seen that carbon dioxide is produced by the action of strong sulphuric acid upon oxalic acid ; the caustic potash absorbs all this carbon dioxide, leaving the monoxide untouched. Now invert the bottle beneath the water in the Properties of Carbon Monoxide. 41 trough, and withdraw the hand ; the water rushes in until it fills one half of the bottle. Sulphuric acid heated with oxalic acid gives rise there- fore to equal volumes of carbon monoxide and dioxide. The sulphuric acid acts by taking away the elements of water j C 2 H 2 O 4 - H 2 O = CO 2 + CO. Experiment II. Decant the gas remaining in the bottle used in the last experiment into another smaller bottle, and bring a light to its mouth ; the gas burns with the peculiar pale blue flame noticed in the preliminary experiments. When the flame has gone out, add a little lime-water to the bottle, and shake it briskly. A turbidity tells you that carbon dioxide is present. By burning carbon monoxide, therefore, carbon dioxide is produced. This is in keeping with what you have already learned about combustion. The monoxide, CO, has been burned or oxidised, a compound relatively richer in oxygen being produced. There is another method of producing this carbon mon- oxide which is one of much interest. Take about 10 grams of formic acid, and add to this, in the apparatus you have just used, 15 grams of strong sulphuric acid. Gently heat the flask, and collect over the trough a bottle full of the gas which is evolved. Test this gas, first by shaking it with caustic potash nothing is absorbed ; then apply a light, when you at once see, by the colour of the flame of the burning gas, that it is carbon monoxide. By the action of sulphuric acid upon formic acid, pure carbon monoxide is produced. Formic acid, H 2 CO 2 , gives up to sulphuric acid the elements of water, H 2 O, while carbon monoxide, CO, remains. C(OH) 2 = CO + H 2 O. Formic acid may be prepared by heating together for several hours glycerine, oxalic acid, and a little water, then adding more water, and raising the temperature : liquid formic acid distils over. The same amount of glycerine may be again used to effect the transformation of a fresh quantity 42 Qualitative Chemical Analysis. of oxalic acid. This formic acid was formerly obtained from ants, or from certain plants, e.g. nettles in which it exists : sometimes also by the reaction mentioned above ; but in this case the oxalic acid was itself obtained from plants, so that formic acid was entirely of animal or vege- table origin. But the experiment you have just performed, viz., splitting this acid into carbon monoxide and water, suggested the idea that by combining these two substances together, formic acid might be re-formed. This has actually been done, and the chemist has thus built up from inorganic or mineral constituents a substance formerly obtainable only from organised forms. Such a building up is termed synthesis, and is exactly opposed to analysis, or pulling to pieces. You may have noticed on a winter's evening a pale blue flame playing on the surface of a coal fire, when the coals are red-hot, and little or no smoke is emitted from them. This flame is produced by burning carbon monoxide. You have already learned (in Lesson I.) that by burning carbon, carbon dioxide is produced ; by burning coals, therefore, this gas is formed ; but this carbon dioxide in passing through the layer of red-hot coals in the upper part of the fire is robbed of part of its oxygen, carbon monoxide being pro- duced, while the oxygen unites with another atom of carbon to form also this gas carbon monoxide ; thus the ultimate form assumed by the gas produced in the combustion of coal in such a fire as that described is that of carbon monoxide : C + CO 2 = 2CO. From the experiments in this lesson you learn (1) What is the action of sulphuric acid upon oxalic acid. (2) That carbon monoxide is a combustible gas, producing, when burned, carbon dioxide. (3) That carbon dioxide can be separated from the monoxide by shaking the mixed gases with caustic potash solution. Preparation of Chlorine. 43 (4) That carbon monoxide is produced in a coal fire. (5) What is the action of sulphuric acid on formic acid. (6) What is the meaning of the term synthesis. LESSON XL PREPARATION AND PROPERTIES OF CHLORINE. HEAT a few grams of manganese dioxide with a little hydro- chloric acid in a test-tube ; a yellowish green gas * with an extremely pungent odour is evolved : Mn0 2 4- 4HC1 = MnCl 2 + 2 H 2 O + C1 2 . A more uniform stream of chlorine gas is obtained by acting on a mixture of manganese dioxide and sodium chlo- ride with dilute sulphuric acid : 2 NaCl + MnO 2 + 2H 2 SO 4 = Na 2 SO 4 + MnSO 4 + 2H 2 O + C1 2 . Weigh out about 30 grams of manganese dioxide and the same amount of sodium chloride, mix them in a mortar, and transfer the mixture to a large flat-bottomed flask. Mix cautiously 38 grams of water with 60 grams of strong sul- phuric acid in a large beaker, and allow this mixture to cool. The apparatus is similar to that in which you prepared carbon dioxide (Lesson IX.), but the generating flask must be considerably larger. You know that chlorine has the atomic weight 35*5 ; it is therefore 35^ times heavier than hydrogen, but hydrogen is 14^ times lighter than air. How therefore must chlorine be collected : by upward or down- ward displacement ? When you have settled the arrange- ment of the receiving bottles, pour the cold mixture of * Hence the name, from x\wpbs = yellowish green. 44 Qualitative Chemical Analysis. sulphuric acid and water through the funnel tube into the flask ; an action at once ensues, the flask gradually becomes filled with yellowish-green vapours, which pass over into the receiving bottle. Conduct all operations with chlorine in a draught chamber, as the fumes of this gas are very hurtful. Make sure that all the connections in the apparatus are tight. (Should you get a whiff of the gas into the lungs, pour a little alcohol on to a piece of filtering paper, and hold this over the mouth and nose so as to inhale the vapours.) When, judging by the colour, you think that the bottle is full of chlorine, remove it, cover it with a well greased glass plate, and set another in its place. Fill thus seven bottles, and proceed to test the properties of the gas. Should the flow of gas slacken, apply a gentle heat to the generating flask by means of a small Bunsen lamp ; the action will soon go on briskly again. Experiment I. Invert the first bottle of chlorine in the trough, withdraw the plate, and shake the bottle ; the water gradually rises in the jar, showing you that this gas is very soluble in water. It is this property of chlorine that obliges us to have recourse to collection by displacement. Experiment II. Moisten a piece of madder-dyed red cloth with water, and put it into one of the bottles of chlorine ; cover the mouth of the bottle with a glass plate, well greased where it touches the bottle, and notice how the red colour of the cloth gradually disappears ; allow the bleaching action to go on, and proceed with Experiment III. Quickly pour a little strong sulphuric acid into the third bottle of chlorine, replace the glass plate, and shake the bottle several times ; after a little time intro- , duce into the bottle a piece of dyed cloth, similar to that used in last experiment. It is not bleached. The sulphuric acid, by taking away all moisture present in the jar, dries the chlorine, and this gas, when perfectly dry, does not bleach. Experiment IV. Moisten a strip of filtering paper with Properties of Chlorine. 45 turpentine, and plunge it into the third bottle of chlorine ; a cloud of black smoke is at once produced, accompanied by a momentary flame, and you find the paper charred and blackened in the jar. The affinity which chlorine possesses for hydrogen is very great, and as turpentine consists of carbon and hydrogen chemically combined, the hydrogen is seized upon by the chlorine, and separated from the carbon or charcoal, which, as you know, is a black soot-like sub- stance. With another bottle of chlorine you may perform an experiment showing the great affinity of chlorine for metals. Experiment V. Place a little powdered metallic anti- mony on a small piece of paper, and from this shake it slowly into the bottle containing chlorine. The antimony, as it falls, burns, each little grain sparkling brilliantly. Chlo- rine and antimony have therefore very great affinity for each other, so great that light is produced by the intensity of their combination. Experiment VI. Into another bottle of chlorine plunge a piece of phosphorus supported on the deflagrating spoon ; the phosphorus takes fire and burns with a brilliant flame, showing you that chlorine has a great affinity for this sub- stance as well as for so many others. Experiment VII. Put two pieces of paper into the last bottle of chlorine with some letters printed or written on each, those on one paper being printed with common ink, those on the other with printers' ink. You notice that the common ink is soon bleached and almost entirely disappears, while the letters formed with printers' ink remain unacted upon. This is a further illus- tration of the affinity of chlorine for hydrogen. Common ink is a vegetable substance, and contains a considerable quantity of hydrogen united with other elements; while printers' ink is essentially a mixture of carbon, in the form of lampblack, with some thickening material. Experiment VIII. Place a few grains of powdered iron 46 Qualitative Chemical Analysis. pyrites in a test-tube with a little water, and, while you shake the tube so as to keep the solid particles suspended in the water, pass a gentle stream of chlorine through the liquid. (The materials used in preparing chlorine for the foregoing experiments will probably, if heated, yield enough of the gas for this experiment.) The pyrites rapidly disappears, and you have soon only a few fine white particles floating about ; allow these to settle, pour the clear liquid into another test- tube, divide it into two portions, and apply a chemical test to each. To portion (i) add a little barium chloride ; a dense white precipitate immediately forms. This, as you will here- after more fully learn, is proof of the presence of sulphuric acid. To portion (2) add a little ammonia ; a foxy-red preci- pitate tells you that iron, in a high state of oxidation, is present. Iron pyrites is essentially sulphide of iron. The action of the chlorine has been to combine with the hydrogen of the water, while the oxygen thus liberated has attacked the iron and sulphur and oxidised them. You thus see how chlorine may be made an exceedingly valuable oxidising agent From these experiments then you learn (1) How to prepare chlorine. (2) That this gas is very soluble in water. (3) That chlorine has a great affinity for many sub- stances, especially for hydrogen. (4) That this property may be applied to bleaching purposes. (5) That chlorine may be made to act as an oxidis- ing agent. Properties of Hydrochloric Acid. 47 LESSON XII. PREPARATION AND PROPERTIES OF HYDROCHLORIC ACID. PLACE a few grains of common salt in a test-tube, and add a drop or two of strong sulphuric acid ; a brisk effervescence ensues, and a gas having a strongly acid pungent odour is given off. The semi-fluid mass in the test-tube solidifies on cooling, forming hydrogen-sodium-sulphate. This reaction is exactly analogous to that by which you prepared nitric acid, NO 3 being in this instance replaced by Cl, and K by Na : NaCl + H 2 SO 4 = NaHSO 4 + HC1. Into the flask used- in preparing carbon dioxide (see Lesson IX.) put about 20 grams of common salt in lumps. To get the salt into this state, fuse it in an iron ladle in the furnace, and when cool break it up into pieces. Pour, through the funnel tube, strong sulphuric acid sufficient to cover the salt in the flask, which is set on a retort-stand, and place a bottle to collect the gas, as in the case of carbon dioxide, testing when the bottle is full by bringing a lighted taper near the mouth of the bottle ; if the light is extinguished, remove the bottle, and cover it with a greased glass plate. Fill thus two bottles with the gas. If the action slackens, apply a gentle heat. You have already noticed, while testing if the bottles were full of gas, that hydrochloric acid is incombustible, and that it does not support combustion. Experiment I. Bring a piece of blue litmus paper into the first bottle of the gas, the paper is at once reddened ; this property of reddening litmus you already know to be characteristic of acids. Experiment II. Bring the other bottle, inverted, beneath the water in the trough, withdraw the plate and shake the bottle briskly ; it is rapidly filled by the water rising within 48 Qualitative Chemical A nalysis. it. This experiment shows you the great solubility of hydrochloric acid in water. Ordinary hydrochloric acid consists of a solution of the gas in water. That the gas is to a certain extent expelled from such a solution, on boiling, you have already had proof. Experiment III. To prepare such a solution, fit up an apparatus similar to that used in making the ammonia solu- tion, but in the small bottle put a little ordinary dilute hydrochloric acid, and let the delivery tube from this bottle dip downwards into a receiving bottle, which is partially filled with water. The fumes formed when hydrochloric acid gas issues into the air are caused by the condensation of the gas by the moisture in the atmosphere. The neutralisation of this acid by ammonia and con- sequent production of the salt ammonium chloride, you have also already noticed. Experiment IV. Fill a bottle with hydrogen, and another over the trough, using warm water, with chlorine; pass equal volumes of each of these into a soda-water bottle, cork it, surround it with a cloth, and shake it well ; withdraw the cork and bring a light to the mouth of the bottle ; a loud explosion ensues, and the formation of hydrochloric acid is rendered evident by the white fumes which appear on bringing a little ammonia to the mouth of the soda-water bottle. Hydrochloric acid gas is made up therefore of equal volumes of hydrogen and chlorine. Experiment V. Heat, in a test-tube, a little strong hy- drochloric acid with a few crystals of potassium dichromate ; by the colour and smell of the issuing gas you at once recog- nise it to be chlorine. As in Experiment IV. you built up hydrochloric acid from hydrogen and chlorine, so in this experiment you have broken up the acid, liberating its con- stituent elements : K 2 Cr 2 O 7 + I2HC1 = Cr 2 Cl 6 + 2KHO + sH 2 O + 6C1. Oxygen Derivatives of Chlorine, 49 In this lesson you learn (1) By what methods hydrochloric acid can be pre- pared. (2) That this gas is soluble in water, and the prac- tical application of this fact. (3) What is the action of hydrochlorie acid upon litmus. (4) That fumes are caused when hydrochloric acid gas issues into the air, and the reason of this. (5) What is the synthetical method of preparing this gas, and what we thus learn of its formation. (6) What is the analytical method of breaking up hydrochloric acid. LESSON XIII. PREPARATION AND PROPERTIES OF OXYGEN DERIVATIVES OF CHLORINE. FIT up an apparatus for generating chlorine, using half as much salt, manganese, &c., as directed in Lesson XL Make about 200 cc., of a tolerably strong solution of caustic potash, place this in a beaker which is kept cool by being sur- rounded with water, and lead the chlorine gas which is generated into the liquid. After a few minutes remove the beaker, pour about half of its contents into another dish, place the beaker, resting on wire gauze, on a stand with a lamp beneath, and continue to pass in the chlorine gas, keeping the solution boiling. Meanwhile make a few experi- ments with that part of the solution which you have set aside. First notice its smell : it is sensibly different from that of chlorine, although chlorous. Experiment I. Dip a piece of madder-dyed cloth into the solution : it is not bleached. 50 Qualitative Chemical Analysis. Experiment II. To a small quantity of the solution in a test-tube add a drop or two of hydrochloric acid. Action ensues, and a gas is given off which, by its smell and colour, you at once recognise to be chlorine. Experiment III. Again dip the piece of cloth used in Experiment I. into the solution, then pass it quickly through dilute hydrochloric acid, and afterwards wash it in water ; it is now bleached. You see that, by the action of the acid on the solution contained in the pores of the cloth, chlorine is liberated ; as the cloth is moist, it is bleached by this chlorine. The solution you have just been experimenting with is a mixture of potassium hypochlorite and chloride : 2KHO + C1 2 = KC1O + KC1 + H 2 O. Bleaching powder is the corresponding calcium compound. To illustrate its forma- tion, perform Experiment IV. Fill a dry flask with chlorine by down- ward displacement, put into it a little powdered quicklime, and shake the flask ; the yellow gas gradually disappears, being absorbed by the lime (as it was by the caustic potash). Pour a little water into the flask, and shake it up with the bleaching powder which you have made ; then test the bleaching effect of the solution, as in Experiment III. You now understand the object of dipping the goods into acid (souring, as it is termed) after passing them through the bleaching powder solution. To the remainder of the solution of potassium hypochlo- rite add a little very dilute nitric acid, place the mixture in a retort to which a small receiver is adapted, and apply a gentle heat. After a little time a colourless peculiarly smell- ing liquid condenses in the receiver. This is hypochlorous acid, HC1O. Experiment V. Dip a piece of dyed cloth into the dis- tillate you have just obtained ; the colour of the cloth is at once discharged. , Experiment VI. Add a few drops of dilute hydrochloric Oxygen Derivatives of Chlorine. 5 1 acid to another portion of the liquid ; chlorine is generated. You can now more fully understand the action of bleach- ing powder. When the goods are soured, the first effect of the acid probably is to produce hypochlorous acid just as you have done ; but this (as you have shown in Experi- ment V.) is at once decomposed, chlorine being liberated. You may now put together all you have learned about chlorine, and attempt to answer the question, How does chlorine bleach? If you consider that dry chlorine gas alone does not discharge vegetable colouring matters (Lesson XL, Experiment III.) ; that chlorine has an intense affinity for hydrogen (Lesson XL, Experiment IV.); that chlorine in presence of moisture does bleach (Lesson XL, Experiment II.) ; and that moisture or water consists of hydrogen and oxygen (Lesson III., Experiment I.) you will be led to the conclusion that the bleaching action of chlorine must depend upon its power of combining with the hydrogen of the water present, and thus liberating oxygen. At the moment of its liberation oxygen is possessed of pecu- liarly active properties (it is in this state called nascent oxygen), so that it combines readily with the colouring matter of the cloth, oxidising this to form compounds which are removed in the subsequent washing. Return to the heated potash solution through wnich you have been passing chlorine ; it will now be saturated with the gas. Remove the chlorine-generating apparatus, pour the solution into a basin, evaporate it to about half its bulk, and set it aside. A salt crystallises out on cooling ; drain off the liquid, and dry the crystals between folds of filtering paper. These are crystals of potassium chlorate, 6C1 + 6KHO = KC10 3 + sKCl + sH 2 O. The potassium chloride formed, being more soluble than the chlorate, remains in solution. You have thus separated two salts by taking advantage of their different degrees of solu- bility in water. E2 52 Qualitative Chemical Analysis. Experime?it VII. Take one or two of the crystals you have prepared, place them in a test glass, cover them with water, put into the glass a very small piece of phosphorus, and set a funnel tube in the glass so that its lower extremity just touches the crystals (see fig. 20), pour a few drops of strong sulphuric acid down the funnel tube ; a greenish gas is evolved which, coming in con- tact with the phosphorus, attacks it so violently as to cause it to take fire even under water. This gas is another oxide of chlorine, viz. the tetroxide, C1 2 O 4 . You have here an instance of very intense chemical action. In this lesson you learn : (1) The modes of producing some of the oxygen derivatives of chlorine, and their leading pro- perties. (2) One of the methods for separating two salts occurring together in solution. (3) The modus operandi of bleaching, and the way in which chlorine bleaches. LESSON XIV. PREPARATION AND PROPERTIES OF BROMINE. INTO a small stoppered retort pour a mixture of 3 grams of manganese dioxide with i-^ grams of potassium bromide, set the retort on wire gauze on the ring of a stand, allowing its beak to pass into a small receiving flask, which is kept cool by being surrounded with cold water. Take out the stopper of the retort and pour in about 20 c.c. of strong sulphuric acid, replace the stopper and gently heat the retort. Dark- Properties of Bromine. 53 FIG. 21. red fumes speedily fill the apparatus, and a heavy dark-red liquid condenses in the receiver ; when you have collected a few cubic centimetres of this liquid, remove the lamp. (Con- duct the operation in a draught chamber.) Bromine is produced in this reaction in a manner exactly analogous to that employed in preparing chlorine. 2 KBr + 2 H 2 SO 4 + MnO 2 = 2Br + K 2 SO 4 + MnSO 4 + 2H 2 0. Bromine occurs, combined with sodium, magnesium, or potassium, in sea water. To illustrate the preparation of the pure potassium salt, from which the bromine itself can, by the above re- action, be prepared, you may per- form the following experiments : Experiment I. Dissolve a few crystals of potassium bromide in water in a test-tube, add a little chlorine water to the solution, and shake the tube ; the bromine is dis- placed from its combination with potassium by the chlorine, and is dissolved in the water ; hence the yellowish-red colour now observed. Add now a few cubic centimetres of ether and shake the tube ; all the bromine is concentrated in the ethereal solution which floats on the surface ; draw this off by means of a little pipette, and add to it caustic potash until the red colour nearly disappears; evaporate the solution on a small water-bath, formed by placing a basin on the top of a beaker containing a little water a piece of filter- ing paper between the basin and the beaker separates these 54 Qualitative Chemical Analysis. so that the steam may escape (fig. 21), and when dry, ignite the residue over a Bunsen flame. You have now pure potassium bromide, from which, as you know, bromine is easily prepared. You have already detected the very irritating odour of bromine (whence its name, Ppwpog = a bad smell). Experiment II. Add to a few drops of bromine about thirty times their volume of water and shake the mixture ; you thus obtain a clear yellowish-red solution. Dip a piece of madder-dyed cloth into this solution ; it is slowly bleached, the action being less intense than in the case of chlorine. Experiment III. Pour a few drops of bromine into a small flask, and heat it gently until the flask is full of bro- mine vapours ; cut and dry a small piece of phosphorus, place this on the deflagrating spoon and plunge it into the flask ; the phosphorus combines with the bromine so energe- tically that light is evolved. This, you remember, was also the case in a similar experiment with chlorine. This action on phosphorus is typical of that which occurs between bromine and many other substances. From these experiments you learn (1) By what method bromine is prepared. (2) That bromine is slightly soluble in water. (3) That this solution possesses a certain bleaching action. (4) That the vapour of bromine is intensely irritat- ing. (5) That bromine has a very energetic action upon many substances. Properties of Iodine. 55 FIG. 22. LESSON XV. PREPARATION AND PROPERTIES OF IODINE AND HYDRIODIC ACID. PLACE a mixture of two grams of manganese dioxide with one gram of potassium iodide in a round-bottomed flask, resting on a retort-stand; pour about three or four cubic centimetres of strong sulphuric acid, through a funnel tube, on to the mixture, and gently heat the flask ; you soon notice violet- coloured fumes appearing which gradually fill the flask, condensing in the neck, and forming brilliant metallic-looking plates. When a sufficient quantity of iodine has been thus produced, collect a little of it, by scraping it off the flask with a glass rod or horn spatula and place it in a clean dry test-tube. This reaction is exactly ana- logous to that used in last Lesson for the preparation of bromine ; you can easily formulate it for your- self. Experiment /. Put a few crys- tals of iodine in a small porcelain basin (about 4 cm. diameter), place an inverted funnel over this, resting on the basin (fig. 22), and set the whole apparatus on a piece of wire gauze on a tripod stand ; now very gently heat the basin, the iodine rises in beautiful violet vapours filling the funnel, on the sides of which it again condenses, forming small glancing crystals. If you call to mind Lesson V., in which you prepared nitric acid by a process of distillation, you will see that this process agrees with that then performed only you now 56 Qualitative Chemical Analysis. distil a solid, by causing it to become a gas, which is again condensed to a solid : such a process is termed sublimation. Experiment II. Take a single crystal of iodine and shake it up with water in a test-tube ; very little is dissolved, the water however is slightly tinged yellow. To a few drops of this solution add a drop or two of a solution of starch in water ; a deep blue colour is instantly produced. Heat this solution; the blue colour disappears, but reappears again when the solution cools. In the formation of this blue compound with starch you have then a means of easily detecting the presence of iodine. Experiment III. Make a solution of potassium iodide in a test-tube, and add to this a few drops of starch paste ; no blue colouration ensues. Now add one drop of chlorine water, the blue colour instantly makes its appearance ; on adding some more chlorine water the solution again becomes colourless, owing to the formation of a chloride of iodine which has no action on starch. Idione compounds there- fore alone do not give a blue colour with starch, it is only free iodine that does this. By the addition of the chlorine water the potassium iodide was decomposed, potassium chloride being formed and iodine set free, which immediately reacted on the starch. By paying attention to what you saw in performing this last experiment, you will be able to say what special precautions must be taken in applying this test to iodine compounds. Experiment IV. Place a small piece of dry phosphorus in a basin and throw into it a few crystals of iodine ; after a very few moments combination of the two substances takes place accompanied by the evolution of light and heat. Experiment V. Put a few crystals of iodine into a small flask and heat this until it is rilled with iodine vapours ; now throw into the flask a little piece of sodium, and continue heating the flask gently ; the sodium combines with the iodine, so energetically that light is evolved. Experiment VI. Dissolve one crystal of potassium iodide in water, add a very few drops of a solution of potassium Properties of Hydriodic Acid. 57 FIG 23. bromide, and then cautiously a little chlorine water; the liquid becomes yellowish-red in colour. Now add a little ether and shake the tube ; the iodine, liberated from the potassium iodide by the action of chlorine, is dissolved in the ether, to which it imparts a violet colour ; this ethereal solution may be drawn off by means of a pipette. A little more chlorine water is now to be added, and again a few cubic centimetres of ether ; this dissolves out the bromine, which is now liberated, and which shows its presence by the distinct orange (not violet) colour imparted by it to the ether. You learn thus how iodine and bromine may be separately obtained from a liquid in which they exist together, such as the liquid produced by lixiviating kelp or the ashes of sea-plants, which again obtain their iodine and bromine from the sea itself. For the preparation of hy- driodic acid we make use of the reaction of Experiment IV. some- what modified. Fit up an apparatus like that represented in fig. 23, consisting of a flask fitted with a cork carry- ing a small separating funnel, and a tube leading into a retort the beak of which, passing through a cork into a two-necked bottle, dips about 3 cm. below the surface of the water in this bottle (this water is coloured blue with litmus). In the flask place 2 grams of amorphous phos- phorus, and 15 grams of iodine ; now very gently heat the flask until these combine to form a blackish-looking mass ; when this is cool, fill the bulb of the separating funnel with cold water, and, by turning the stopcock, allow this to flow, drop by drop, on to the phosphorus teriodide in 58 Qualitative Chemical Analysis. the flask (this is the compound produced by the mutual action of phosphorus and iodine upon one another), which is decomposed : PI 3 + sH 2 O = H 3 PO 3 + 3 HI. Hydri- odic acid, HI, is evolved, and passes into the retort, and thence into the water in the bottle, by which it is readily dissolved. This gas, being very soluble in water, is some- times so quickly absorbed as to cause a partial vacuum in the retort, into which the water rushes ; but, before the bulb of the retort is filled with water, the level in the bottle sinks below the beak of the retort ; thus no water is allowed to flow back into the flask. The blue colour of the water you notice gradually turns to red. Experiment VII. Disconnect the apparatus and arrange it so that the gas shall pass into an empty dry two-necked bottle, into which, through the second neck, you lead chlorine. Violet vapours filling the bottle show the presence of free iodine ; the hydriodic acid therefore has been decomposed by the chlorine, hydrochloric acid being formed, and iodine set free. In this respect hydriodic acid differs from its chlorine-analogue hydrochloric acid. The bromine-analogue hydrobromic acid, HBr, also exists and i formed by a reaction similar to that employed above. From your experiments in this lesson you learn (1) The method of preparing iodine. (2) The meaning of the term sublimation ; and that iodine may be sublimed. (3) The reaction of free iodine with starch. (4) The intense action of phosphorus upon iodine. (5) The application of the reaction noted in (4) to . the preparation of hydriodic acid. (6) The solubility in water of the gas hydriodic acid, which agrees in this respect with hydro- chloric acid, but differs in > (7) The fact that it is decomposed by chlorine, hydrochloric acid and iodine being formed. Properties of Silicon Fluoride. 59 LESSON XVI. PREPARATION AND PROPERTIES OF HYDROFLUORIC ACID, SILICON FLUORIDE, AND HYDROFLUOSILICIC ACID. Experiment /. Take a small circular piece of sheet lead, about 6 or 7 cm. diameter, place this in a mortar, and, with the pestle, press the centre of the lead inwards ; you thus form a little leaden cup a platinum crucible or basin, if you have one, will do instead of this cup. Gently warm a plate of glass large enough to cover the mouth of the little dish, and rub over it a piece of beeswax, so that the plate is equally covered with a thin coating of this substance. Into the leaden dish put about 5 or 6 grams of powdered fluor- spar, and drench this with strong sulphuric acid. Trace some device on the glass plate with a sharp-pointed piece of wood, or wire, making sure that the lines are drawn quite through the wax. Place the plate over the leaden dish with the side on which the lines are drawn downwards. Apply a gentle heat to the dish for a few moments ; you notice that white fumes are evolved and fill the space between the glass plate and the dish. After a few minutes remove the glass plate, wash out the leaden cup, and remove the wax from the glass by rubbing it with a warm cloth ; the design which you traced is seen to be etched into the glass. You infer there- fore that, by the action of sulphuric acid upon fluor-spar, a gas has been produced which has the property of etching glass. You at once see the reason for not using a glass vessel in the preparation of the gas. The reaction which goes on between the sulphuric acid and fluor-spar is thus formulated : H 2 S0 4 + CaF 2 = 2HF + CaSO 4 . You noticed the fumes produced by the hydrofluoric acid in the air, and you have learned something about its remark- able action on glass ; the following experiments will explain this action more fully. 6o Qualitative Chemical Analysis. FIG. 24. Experiment II. Arrange an apparatus similar to that used in the preparation of carbon dioxide, but let the flask rest on a retort-stand; into the flask put a mixture of 10 grams of powdered fluor-spar with about 15 grams of fine white sand. Into one of the gas bottles intended for the collection of the gas pour mercury sufficient to form a layer on the bottom to the depth of 10 or 12 mm., and let the delivery tube from the flask dip beneath this mercury (fig. 24). In the first instance, however, use a dry empty bottle for the collection of the gas. Pour, through the funnel tube, about 20 c.c. of strong sulphuric acid. Shake the flask well, so as to mix the sub- stances in it, and apply a gentle heat A gas, which fumes in the air, soon begins to come off. Do not apply much heat in this process, otherwise the mixture in the flask will froth up and may come over. When a few mi- nutes have elapsed, bring a lighted taper into the gas bottle; if it is extinguished immediately on entering the bottle, sufficient gas has been collected. You learn by this that the gas is heavier than air, that it is incombustible, and that it does not support combustion. Remove the bottle of gas, and in its place set the second bottle containing the mercury ; let this bottle be nearly filled with water, and allow the evolution of gas to proceed, while with that already collected you perform Experiment I II. Attach, by means of caoutchouc tubing, a small piece of glass tubing drawn to a tolerably fine point, to the end of a funnel tube. Pour a little water into the Properties of Hydrofluoric A cid. 6 1 funnel ; the opening of the small tube should be of such a size that the water slowly trickles out at it. Bring this tube within the bottle containing the gas ; as each drop of water falls from the opening of the narrow tube, it seems to turn solid, and after some time you have a long stalactite hanging from the end of the tube. Let us consider how this is brought about. Fluor-spar and sulphuric acid, as you have just learned, produce, by their mutual action, hydrofluoric acid ; this, at the moment of its production, reacts on the sand you placed in the flask (sand is nearly pure silica), and, combining with the silica, forms- the gas silicon tetrafluoride, which you have collected. This gas is decomposed by water, silica being produced. As each drop of water came into contact with the silicon tetrafluoride, the gas was decomposed, and the silica thus formed coated the drop of water, holding it as in a bag : 2CaF 2 + SiO 2 + 2H 2 SO 4 = 2CaSO 4 -f 2H 2 O + SiF 4 . If you now look at the other bottle, you will see an action going forward similar to that which you have just noticed. As each bubble of gas comes up through the water, it is coated with silica, which gradually accumulates on the surface, until the water is full of this silica in a very finely divided state. Were it not for the layer of mercury the silica would soon choke up the mouth of the delivery tube. When the action has proceeded for some time, you may remove and wash out the generating flask. Cover the bottle with a glass plate, while you perform Experiment IV. You remember the action of hydrofluoric acid upon glass ; you also know how this gas is produced ; and in the last experiment you have seen that the mutual action of silica, fluor-spar, and sulphuric acid, when heated together, is to produce the gas silicon fluoride : therefore you may infer that the way in which hydrofluoric acid etches glass (which is a compound of silicon), is by seizing upon the silica in the glass, and forming therewith this silicon 62 Qualitative Chemical A nalysis. fluoride. To verify this supposition is the purpose of the present experiment. Put a little fluor-spar into the leaden dish, adding to it sulphuric acid as before ; cover the dish with a glass plate, in the centre of which you have put a drop of water, and heat gently. You soon see that the drop of water is coated with a film of silica ; therefore you conclude that the gas silicon fluoride is actually produced and is decomposed by the water. The water in the gas bottle (Experiment II.) is now to be separated by filtration from the finely divided silica suspended in it. Take a medium-sized glass funnel, and a circular piece of filtering paper (fig. 25, No. i). (It is con- venient to have your filtering paper cut in circular pieces of FIG. 25. various sizes, about 4, 6, 8, 10, and 12 cm. diameter.) Fold the paper so as to form a half-circle (fig. 25, No. 2), and then again at right angles to the first fold (fig. 25, No. 3). Open out the paper thus folded, and you have a filter formed three folds of the paper being on one side, and one on the other. The funnel chosen should be rather larger than the filter. Set the filter inside the funnel, moisten- the paper with a few drops of water, and with the finger press the filter to the sides of the funnel, leaving no bubbles of air between the paper and the glass. Place the funnel in the ring of a retort-stand, or on a filter-stand, a beaker glass being set below it to receive the filtered solution, or filtrate, as it is termed. Making a Wash Bottle. 63 Now slowly pour the liquid down a glass rod held in one hand from the gas bottle on to the filter. The liquid is thus delivered directly on to the filter, and all loss from spirting avoided. The lower end of the funnel should, for the same reason, rest against the side of the beaker ; the filtered liquid thus gently runs down the side of the glass (fig. 26). Care- fully filter off the suspended silica from the liquid, set aside FIG. 26. the silica on the filter for further use, and proceed to examine the solution. Touch a piece of blue litmus paper with a drop of the solution, on the end of a glass rod; the litmus paper is reddened : you have, therefore, an acid in the solution. To a little of this acid liquid, in a test-tube, add a drop or two of barium chloride solution : an immediate white precipi- tate is produced. This application of hydrofluosilicic add (as it is called) for the detection of barium is one which 64 Qualitative Chemical Analysis. you will have occasion to use hereafter. The action of water on silicon fluoride is to form silicic acid, and hydro- fluosilicic acid : 3SiF 4 + 4H 2 O = H 4 SiO 4 + 2H 2 SiF 6 . The new acid should be kept in a gutta-percha bottle, as it gradually acts upon glass. The silica on the filter, which you set aside, is now to be washed, dried, and preserved for subsequent use. To wash a pre- cipitate, you require a wash-bottle (see fig. 27, No. i). Choose a flat-bottomed flask, capable of holding about three- quarters of a litre, also a good cork to fit this flask (preferably a caout- chouc cork) ; in the cork bore two holes. Fuse the edges of a piece of glass tubing about 10 cm. longer than the height of the flask, and bend this tube, at about 10 cm. from the end, so as to form an obtuse angle. Take another little piece of tubing, gently soften it in the Bunsen flame, keep turning it round, and very gradually drawing it out, so that you obtain a tube like that repre- sented in fig. 27, No. 2, the glass in the narrow part being tolerably thick. Allow it to cool, and cut it at the point a. Fuse the edges of this tube, and attach it to the shorter end of that already made by a little piece of caoutchouc tubing. Take another piece of glass tubing, about 10 cm. long, bend it gently about the middle, and round its rough edges. Now fit these two tubes through the cork of the flask, so that the longer may dip to the bottom of, the shorter only a little way into, the flask. By blowing in at the shorter tube a stream of water is forced out at the narrow opening of the longer. By turning the small jet attached by flexible tubing, you can direct the stream of water in any direction you please. Fill the wash-bottle with water, and proceed Properties of Methane. 65 to wash the silica in the filter, sending the stream of water in a circular direction round the filter, so as to bring all solid matter into the centre of the filter ; when you have filled up the filter with wash water, allow it to drain through before adding more. Continue the washings until all acid is re- moved (that is, until the washings no longer redden litmus paper), then cover the funnel with a piece of paper, and set it aside to dry. When dry, put the silica into a stoppered bottle, and preserve it. In this lesson you learn (1) By what method hydrofluoric acid is prepared. (2) That this acid etches glass, and the way in which it does this. (3) By what method silicon fluoride is prepared. (4) That this gas is decomposed by water ; and (5) That hydrofluosilicic acid is thus produced. (6) That a solid may be separated from a liquid by filtration. (7) What is the use of the wash-bottle. LESSON XVII. PREPARATION AND PROPERTIES OF METHANE (MARSH GAS). INTRODUCE into an iron tube about 20 cm. long and 5 cm. diameter (see fig. 28) a mixture of 8 grams of dry sodium ace- tate with 8 grams of caustic soda previously strongly heated on an iron plate and 12 grams of lime. Fit in a good cork with a delivery tube, arrange the trough and a bottle to collect the gas ; now heat the tube, beginning at the F 66 Qualitative Chemical Analysis. upper part, and heating gradually downwards. As the gas does not come off until a pretty high temperature is reached, FIG 28 it: is P referable to use such an apparatus as that described, than to heat the mixture in a glass flask, which is very liable to crack.* NaC 2 H 3 2 + NaHO = Na 2 CO 3 + CH 4 . The lime in the above mixture serves to render it more infusible, and to prevent it stopping up the tube. As the bubbles of gas pass through the water in the trough, test them from time to time by bringing a lighted taper near them. As soon as they inflame, begin to collect the gas ; and when you have filled three bottles, withdraw the delivery tube from the water. Experiment I. Set an inverted bottle of the gas on the ring of a retort-stand, and apply a light to its mouth ; the gas burns with a bluish non-luminous flame. Experiment //. Pour a little lime-water into the bottle used in the last experiment, when the flame has gone out ; on shaking the bottle you learn, from the turbidity in the lime-water, that carbon dioxide is present. One of the pro- ducts of the oxidation or burning of marsh gas is therefore carbon dioxide. Marsh gas is formed in coal mines, where it is known under the name of ' fire-damp.' If mixed with ten volumes of atmospheric air it forms an explosive mixture, producing water and carbon dioxide. This latter gas will not support life ; hence the dreadful effects produced, not only by the actual explosion in mines, but also by the formation of this ' jchoke ' or ' after ' damp, as the carbon dioxide is called by the miners. Experiment III. To illustrate the explosive nature of a mixture of marsh gas and oxygen, decant into a soda-water * This gas may also be easily prepared by heating I part of dry sodium acetate with 2 parts of sodium carbonate and 2 parts of lime. Properties of Methane. 67 bottle one volume of the gas, and add two volumes of oxygen j cork the bottle, shake it, and wrap a cloth . tightly round it, then take out the cork, and bring a lighted taper to its mouth ; a very sharp explosion ensues. Experiment IV. Fill a perfectly dry flask, capable of holding about 250 c.c., with marsh gas, by upward displace- ment, and fill also a similar flask with chlorine ; FlG 2g connect these flasks by a glass tube passing through corks in each, and set them in the sun- light, the flask containing marsh gas being uppermost (see fig. 29). You soon notice that the upper as well as the lower flask, becomes filled with yellow fumes, but that these after a little time entirely disappear. Now separate the flasks, and bring a bottle containing strong ammonia solution near the mouth of each ; dense white fumes are formed : this, you remember, (Lesson IX.), tells you that hydrochloric acid is present. The chlorine has therefore withdrawn part of the hydrogen from the marsh gas. An- other quantity of chlorine combines with the remainder of the marsh gas, forming a new gaseous compound, the pre- sence of which you may detect by its peculiar ethereal odour after agitating the gaseous mixture in the flask with a little water to absorb the hydrochloric acid. You learn then from these experiments (1) By what method marsh gas may be prepared. (2) That this gas is combustible. (3) And that by its combustion carbon dioxide is produced. (4) What is the cause of the evil effects produced by this marsh gas when present in mines. (5) That chlorine acts on marsh gas in sunlight. F 2 68 Qualitative Chemical Analysis. LESSON XVIIL PREPARATION AND PROPERTIES OF ETHENE (OLEFIANT GAS). FIT up an apparatus like that shown in fig. 30, consisting of two flasks, the first of which is fitted with a cork carrying a tube bent twice at right angles ; the last limb of this tube dips, through a wider tube, into the second flask, from which a delivery tube leads to the trough. The second flask FIG. 30. also carries a thermometer, as shown in the figure. Into the first flask pour about 20 c.c. of alcohol (rectified spirits). Mix 40 c.c of strong sulphuric acid with 12 c.c. of water, and pour this mixture into the second flask, and fit the corks into their places. Heat both flasks; the alcoholic vapours pass into the sulphuric acid (the temperature of which must not be raised above 170), the acid gradually darkens in colour, and bubbles of gas come up through the water in the trough. When, on bringing a light close to it, the issuing gas takes fire, you may begin to collect it Fill Properties of E them. 69 three bottles with ethene gas, withdraw the lamps, and at once take the delivery tube of the first flask out of the liquid in the second by drawing it up the wider tube. In this reaction the sulphuric acid acts in a manner similar to that noticed in the case of oxalic acid, viz. it withdraws the elements of water : C 2 H 6 = C 2 H 4 + H 2 0.* Experiment I. Apply a light to the mouth of the first bottle standing on the table ; the gas burns with a bright white smoky flame, while the taper is extinguished. Ethene is therefore a combustible gas. After the combustion is over, add a little lime-water to the bottle, and shake it briskly ; the turbidity of the liquid indicates the presence of carbon dioxide. Experiment II. Graduate a soda-water bottle into four divisions (see Lesson III.), and decant into it one measure of ethene gas, and three measures of oxygen ; cork the bottle, surround it with a cloth, and shake it several times ; on withdrawing the cork and applying a light, a loud ex- plosion occurs You have in this experiment completely oxidised the carbon and hydrogen of the ethene, carbon dioxide and water being the products : C 2 H 4 + O 6 = 2CO 2 + 2H 2 O. Experiment III. Pour a few drops of bromine into a small flask, shake the flask, and pour the excess of bromine back into the bottle ; and bring the flask, mouth downwards, into one of the bottles of ethene. The red vapours quickly disappear, while heavy oily drops form on the sides of the bottle, and run down to the bottom. This oil is a com- pound of ethene with bromine. A similar oily compound is produced by the union of this gas with chlorine ; hence the name defiant or oil-producing gas sometimes given to ethene. * This reaction probably occurs in two stages ; in the first ethyl sulphuric acid is formed, and this is then split up into ethene and sul- phuric acid. /o Qualitative Chemical Analysis. Experiment IV. Graduate a gas bottle into three equal parts, fill it with water at the trough, and quickly decant up into it two measures of chlorine, and one of ethene ; cover the mouth of the bottle with a glass plate, remove it from the trough, agitate it briskly, and apply a light ; the gases burn with a very smoky flame, which gradually passes down the bottle, much carbon being deposited. This experiment further illustrates the great affinity which chlorine has for hydrogen ; the ethene is robbed of its hydrogen and the carbon is deposited on the glass. In this lesson you have learned (1) What is the action of strong sulphuric acid upon alcohol. (2) By what mode ethene is prepared. (3) That ethene is a combustible gas, burning with a smoky flame. (Coal gas owes its lumino- sity in great measure to the presence in it of ethene.) (4) That for its complete oxidation or burning, one volume of ethene requires three volumes of oxygen. (5) That with chlorine and bromine ethene forms oily compounds. (6) But that with different proportions of this gas and chlorine the hydrogen of the former is seized upon by the latter, carbon being libe- rated. Contrast this with the action of chlo- rine upon methane (last Lesson), whereby a substitution product of the methane (that is, a product in which part of the hydrogen is replaced by another element) and hydro- chloric acid are produced. Preparation of E thine. 71 (7) That the explosion which occurs when a light is brought into a mixture of coal gas and air is caused by the combination of the methane and ethene, contained in the gas, with the oxygen of the air. LESSON XIX. PREPARATION AND PROPERTIES OF ETHINE (ACETYLENE). THIS gas is produced in many cases of incomplete combus- tion of organic substances ; thus, when a Bunsen lamp burns down, the gas is only partially consumed, ethine is pro-, duced, and can be recognised by its peculiar smell. This gas combines with certain metals, as copper, &c. The com- pound produced when ethine is passed through an ammo- niacal solution of cuprous chloride is very characteristic, possessing a bright red colour ; we make use of this reaction in order to detect the presence of ethine. Experiment I. Make a solution of cuprous chloride by dissolving 10 grams of black cupric oxide in about 100 c.c. of ordinary hydrochloric acid, boil for 15 minutes with 8 grams of metallic copper in small pieces, pour this solu- tion into about one litre of water, allow the precipitate to subside, pour off the water, and rinse the precipitate into a bottle, of about 150 c.c. capacity, nearly full of water. After the subsidence of the precipitate, the water is again poured off, 40 grams of powdered ammonium chloride are added, the bottle is again filled with water and shaken up. To a small quantity of this solution gradually add am- monia until the precipitate which forms redissolves, and you have an azure-blue solution. Pour a few cubic centimetres of this solution into a wide-necked flask, capable of holding about half a litre, rinse the flask with the liquid and allow it Qualitative Chemical A Italy sis. FIG. 31. to drain for a few moments ; turn down a Bunsen burner so that it may burn below > and now bring the flask, mouth down- wards, a little way over the top of the lamp, and support it in this position on a retort-stand ; after a few minutes you will notice that the inside of the flask becomes coated with a red substance, which is the compound produced by the action of ethine upon cuprous chloride solution. It is termed cuproso-vinyl oxide, and has the formula (C 2 HCu 2 ) 2 O. To show the presence of ethine in coal gas, we will per- form Experiment II. Choose a U-tube each limb of which is about 12 or 15 cm. long and i cm. diameter, and fit into each of the openings a cork carrying a little piece of glass tubing ; let one of these tubes be drawn to a tolerably fine opening, to the other attach a caoutchouc tube connected with the gas tap ; pour into the U-tube sufficient ammo- niacal cuprous chloride solution to fill the bend, support the tube on a clamp or retort- stand and turn on the gas, which, bubbling through the solution in the bend of the tube, issues from the small glass tube, where it may be lighted (fig. 31) ; after a few minutes you notice the formation of a copious red precipitate in the blue solution, which proves the presence of ethine in the coal gas. You have learned (1) That ethine is produced in very many cases of incomplete combustion. (2) That ethine is present in coal gas. (3) How to detect ethine. Structure of Flame. 73 LESSON XX. STRUCTURE OF FLAME. FROM the experiments performed in Lesson III. you have learned the exact relation which exists between the terms ' combustible ' and ' supporter of combustion,' and from various experiments you have learned what is meant by the term < combustion.' In Lesson XVIII., Experiment I., you saw that ethene burns with a smoky, luminous flame. Experiment I. Set up the apparatus used in preparing ethene (fig. 30, p. 68), putting about 10 c.c. of alcohol and a corresponding amount of sulphuric acid into the flasks ; to the end of the delivery tube adapt, by means of caoutchouc tubing, a small glass tube having a tolerably fine orifice. Fill a large wide-mouthed bottle with oxygen ; when ethene gas is coming off in a gentle stream, light it ; it burns with a smoky flame. Now bring the bottle of oxygen gas, mouth downwards, over the burning gas ; the flame becomes much less luminous and more elongated. You thus see that when this gas is completely burned, or oxidised, the luminosity of the flame is diminished. Experiment II. Fit a two-necked Wollff's bottle with corks, through one of which passes a small glass tube drawn to a tolerably fine point, and through the other a chloride of calcium tube, in the bulb of which is a little cotton-wool which has been previously soaked in benzene. In the bottle place materials for generating hydrogen (see fig. 32). When the gas has been coming off for a little time, test it by filling a test-tube by upward displacement and bringing this near a flame ; if the hydrogen burns quietly in the tube, you know that the air has been driven entirely out of the bottle. Now light the gas issuing from both necks of the bottle. The flame of the hydrogen burning at the mouth of the small glass tube is almost colourless, while that at the 74 Qualitative Chemical Analysis. mouth of the other tube is tolerably luminous. The gas giving the latter flame passes, before being burned, through FIG. 32. wo l soa -ked in benzene, which is a hydrocarbon, or compound of carbon and hydrogen, resembling in this re- spect ethene. But the presence of heavy hydrocarbons in a flame gives luminosity to that flame. On the other hand, a flame in which hydrocarbons of low density only are present is wanting in luminosity. The luminous character of the flame of coal gas is now explained, as you already know that that gas contains hydrocarbons of comparatively high density. It is also not improbable that in the burning of such luminous flames a certain amount of carbon is liber- ated, and that this also radiates light. Experiment III. Fill two bottles with chlorine by downward displacement, and bring one of these over a Bunsen lamp which is burning with a small flame ; the lumi- nosity of the flame is much increased. You have learned that chlorine combines with ethene, methane, &c. (components of coal gas), and also that chlo- rine has a great affinity for hydrogen. Both of these actions probably occur in the present case, and hence, on account of the density of the products of combustion, as well as, pos- sibly, on account of the presence of solid carbon, the lumi- nosity of the flame is much increased. Experiment IV. Set up a small hydrogen-generating apparatus having a platinum jet adapted to the end of the delivery tube at which the issuing gas is ignited. On bring- ing the second bottle of chlorine over the burning hydrogen, an increase in the luminosity of the flame is noticed. The product of combustion of hydrogen in chlorine hydrochlo- ric acid possesses a density twice as great as that of the Structilre of Flame. 75 product of combustion of hydrogen in air, viz. water ; there- fore the flame appears brighter when the bottle of chlorine is brought over the burning hydrogen. In this case the pre- sence of solid matter in the flame is impossible. Experiment V. Bend a glass tube, about 60 cm. long, into the shape shown in fig. 33, No. i; bring the end a into the flame of a candle immediately above the wick ; on ap- plying a light to b, you find that combustible gases are being withdrawn from the flame. FIG. 33. No. i. No. 2. Experiment VI. Move the end a of the tube until it is situated at the outside of the candle flame; a light now brought to the end b is extinguished, telling you that a non-combustible gas is present Allow the end b of the tube (fig. 33, No. 2) to dip into a small flask, into which, after a little time, pour a few cubic centimetres of lime-water ; on shaking the bottle a precipitate forms in the solution. The gas which you have drawn off is therefore carbon dioxide. These experiments tell you that in the flame of a combustible carbonaceous sub- stance there is an inner zone in which the gases are but partially burned, then a zone containing carbonaceous matter 76 Qualitative Chemical Analysis. (constituting the luminous part of the flame), while outside of this is the zone of complete combustion in which all the carbon is burned to carbon dioxide. The presence, in this part of the flame, of the product of combustion of the hydrogen, viz. water, may be shown by bringing a test-tube, containing a little cold water, into the outer flame of the candle ; drops of dew are immediately formed on the tube, by the con- densation of the water vapour on the cold glass. There is yet another part of the flame, called the mantle, which is situated at the extreme outer edge of the flame, FIG. 34 . FlG - 35- FIG. 36. and only becomes visible by holding a piece of cardboard (cut so as exactly to cover all that part of the flame ordinarily visible) between the eye and the flame (fig. 34) ; the mantle will then be seen round the outer edge of the cardboard. Experiment VII. Make a small helix of copper wire (see fig. 35), leaving a space between each coil, and bring this over the flame of a candle ; the flame is extinguished. As air sufficient to support combustion could enter between the coils of wire, the flame could not be extinguished by suffocation. Experiment VIII. Pour, from a small basin grasped by a pair of crucible tongs, a quantity of burning methylated spirit on to a piece of wire gauze held over a second basin Properties of Sulphur. 77 (fig. 36). The spirit passes through the gauze, but it is no longer ignited. The gauze presents to the burning spirit a large metallic surface, which conducts away heat from the flame, so that the process of rapid oxidation of the consti- tuents of the spirit ceases, and the flame therefore goes out. The same thing occurred in Experiment VII. The copper wire so quickly conducted away heat from the candle flame, that the temperature required to inflame the mixture Of gases could no longer be maintained. On this principle of extinguishing a flame Sir Humphry Davy based his celebrated ' safety lamp.' In this lesson you have learned (1) What is the difference between a luminous and a non-luminous flame. (2) What is the constitution of a candle flame, as the type of others. (3) That a flame may be extinguished by heat being conducted from it by a metallic surface. LESSON XXI. PROPERTIES OF SULPHUR. Experiment I. Heat a quantity of * flowers of sulphur ' in a Florence flask placed on wire gauze on a retort-stand. You notice that the sulphur melts, forming a clear mobile liquid, it then darkens and gets thicker, and, as the heat is increased, it again becomes fluid. When this point is reached, take hold of the flask with a cloth or pair of crucible tongs, invert it, and pour the molten sulphur into cold water in a beaker. The mass of sulphur in the water retains its plasticity, and can be moulded with the hand, like recently melted caoutchouc. When sulphur is allowed to spontaneously crystallise FIG. 37. 78 Qualitative CJwmical Analysis. from its solution in carbon disulphide, it forms octahedral crystals of forms derived from that shown in fig. 37 ; but, as you will learn from the next experiment, it may also be obtained in another crystalline form. Experiment II. Melt 20 grams of sul- phur in a Hessian crucible placed in a fire, and allow it to cool until a crust forms on the surface of the mass ; now make two holes in this crust with a glass rod, and invert the crucible so that the still molten sulphur flows out at one of the holes into a dish of water, while air enters at the other. On removing a pcrtion of the sulphur with a knife, you will find that the inside of the crucible is full of needle-shaped or prismatic crystals of sulphur. You have already learned that sulphur burns in air or oxygen, producing the gas sulphur dioxide. Experiment III. Fuse a small quantity of sulphur, mixed with an equal quantity of sodium carbonate, in a porcelain crucible over a Bunsen flame, when cool pour a little water into the crucible and dip a silver coin into the solution. The silver is stained black owing to the produc- tion of silver sulphide. This reaction is occasionally used for the detection of sulphur. From these experiments you learn (1) What is the action of heat upon sulphur. (2) By what method the presence of sulphur may be detected. That sulphur is capable of existing in various modifications, viz. as plastic, octahedral, or prismatic. Such modifications of one and the same substance are called allotropic modifica- tions of that substance. (3) Properties of Sulphur Dioxide. 79 LESSON XXII. PREPARATION AND PROPERTIES OF SULPHUR DIOXIDE AND TRIOXIDE. INTO the flask of an apparatus similar to that represented in % 3 8 put about 20 grams of copper clippings (take care to slide the pieces of copper down the side of the flask to pre- vent cracking it), and add, through the funnel tube, 60 c.c. of strong sulphuric acid. Set the flask on a retort-stand, FIG. 38. and let the delivery tube dip into a gas bottle. Place a Bunsen lamp beneath the flask and gradually increase the heat; after a little while you notice a brisk action going on in the flask; when the action has thus begun, you may moderate the heat. You soon perceive that the gas which is given off has a very pungent sulphurous odour. It is identical with that produced by burning sulphur in oxygen, viz. sulphur So Qualitative Chemical Analysis. dioxide : 2H 2 SO 4 + Cu = CuSO 4 + 2H 2 O + SO 2 . Collect two bottles of the gas, and while the evolution of the gas is proceeding, get ready an apparatus in which to condense the sulphur dioxide. Choose a piece of stout glass tubing about 2 cm. diameter ; at a distance of 20 cm. from one end soften the tube in the flame (in the case of thick tubing such as this, it is better to use the blowpipe, very gradually increasing the heat of the flame), and draw it out; by heating the projecting portion in the flame, touching it with a little piece of glass- rod, and sharply drawing it off, you will get rid of most of this part ; finally, heat the end of the tube to redness, keep turning it round, and blow in at the open end once or twice; vou will thus get a tube sealed neatly at one end. Now heat the tube at about 8 cm. or so from FIG. 39. the open end, and gently draw it out until the narrow part is just a little wider than the delivery tube of the gas-generating apparatus (fig. 39). Select a beaker whose height is about equal to the length of the tube you have just prepared; set this, with its open end upwards, in the middle of the beaker, and surround it with a freezing mixture made by intimately mixing together one part of pounded ice with about one and a half parts of salt. By this time the two gas bottles will be full of sulphur dioxide, cover them with greased glass plates, and bring the delivery tube into the wide tube standing in the freezing mixture, so that it may reach nearly to the bottom of this latter tube. Allow the evolution of gas to proceed for some time ; meanwhile examine that which you have collected. Experiment I. Plunge a lighted taper into one of the bottles ; the flame is extinguished, and the gas does not take fire ; quickly replace the glass plate. Experiment II. Plunge a few flowers (preferably red roses or reddish-coloured pansies) into the same bottle of sul- Properties of Sulphur Dioxide. 8 1 phur dioxide. The red colour of the flowers is after a little time discharged. This gas, therefore, possesses the property of bleaching; further experiments will explain this more fully. Experiment III. Invert the second bottle beneath water in the trough, and withdraw the glass plate; the water rises in the jar, showing that the gas is soluble in water. Slip the hand beneath the mouth of the bottle, remove it from the water, and shake it briskly; again bring it under the water and repeat the operation until the water has nearly filled the bottle. This solution contains sulphurous acid H 2 SO 3 = SO 2 + H 2 O. Experiment IV. Transfer a few cubic centimetres of this solution to a test-tube, and add a drop or two of barium chloride solution; no change ensues. Boil a second portion of the sulphurous acid solution with a few drops of nitric acid, and again add barium chloride; the immediate formation of a white precipitate shows that there is a difference between this and the original liquid. This white precipitate with barium chloride, as you will afterwards more fully learn, tells us that sulphuric acid is present. The sulphurous acid has, there- fore, been changed to sulphuric acid, i.e. it has taken up oxygen, H 2 SO 3 + O = H 2 SO 4 . It is in this way, viz. by robbing substances of their oxygen, or acting as a reducing agent, that sulphur dioxide bleaches. Experiment V. To a few cubic centimetres of sulphurous acid solution add a little bromine water and boil the mixture. On applying the test for sulphuric acid viz. barium chlo- ride to a portion of the liquid, the formation of a white precipitate tells you that this acid has been formed. The action which has here taken place is analogous to that noticed in the last experiment. The oxygen of the water has been seized upon by the sulphur dioxide, while the hydrogen which remains has combined with the bromine to form hydrobromic acid. To prove the presence of the latter substance, add a little silver nitrate solution to another 82 Qualitative Chemical Analysis. part of the liquid ; an immediate white precipitate of silver bromide is produced. Experiment VI. Pour a small quantity of a solution of potassium iodide into a beaker, add some water and a few drops of starch paste, then one or two drops of chlorine water ; as you have already learned, an intense blue-coloured solution is thus obtained. To this solution add, drop by drop, with constant stirring, sulphurous acid solution until the blue colour is entirely discharged. This bleaching is effected by the sulphurous acid combining with the oxygen of the water to form sulphuric acid, while the hydrogen of the water combines with the iodine liberated from the potas- sium iodide to form hydriodic acid, which, as you know, is colourless, soluble in water, and without action on starch. You thus learn that sulphur dioxide bleaches in a way directly opposed to that in which chlorine bleaches ; the former acts by reduction, i.e. by taking away oxygen ; the latter by oxidation, i.e. by giving oxygen. You must now turn your attention to what is going forward in the tube in the freezing mixture. If a steady flow of gas has been kept up, you will find, on raising the tube partially out of the beaker, that it contains a liquid ; by the application of cold you have caused the gaseous sulphur dioxide to become liquid. Many gases can be thus condensed, while others refuse, under all circumstances, to appear in any other than a gaseous form. The latter are termed, on this account, per- manent gases. Keeping the tube as much as possible in the freezing mixture, direct a blowpipe flame on to the narrowed portion ; when fused draw this out, but do not quite close it ; allow the tube to get quite cold, again heat the narrow part, and now quickly draw it off. You may remove the tube from the beaker and set it aside ; the sulphur dioxide will remain liquid in the closed tube. Experiment VII. Heat a few drops of the sulphurous acid solution in a test-tube. You distinctly smell that sul- phur dioxide is given off. Let us try to oxidise this sulphur Properties of Sulphur Dioxide. 83 dioxide, and thus produce the higher compound of sulphur with oxygen, viz., sulphur trioxide. Experiment VIII. Pass a stream of sulphur dioxide into a part of the solution of sulphurous acid, until the liquid smells strongly of the gas ; then transfer it to a small flask, fitted with a cork, in which two holes are bored ; through one of these passes a tube, which reaches nearly to the bott9m of the flask, while through the other a shorter tube is fitted which ends just below the cork. Fit up a small oxygen-generating apparatus, but let the FIG. 40. end of the delivery tube be bent at a right angle with the longer part of the tube. Support this on a stand, and con- nect it, by caoutchouc tubing, with the longer tube coming from the flask. Take a few pieces of asbestos, soak them in platinum tetrachloride solution, then dry and ignite them in a small basin over a Bunsen lamp. The platinum tetra- chloride is decomposed, chlorine being given off, while platinum remains behind in a finely divided state covering the asbestos, which therefore appears nearly black. Put this platinised asbestos into the bulb of a chloride of calcium G 2 84 Qualitative Chemical A nalysis. tube, and through a cork in the wider end of this tube pass the short tube leading from the flask. The apparatus is represented in fig. 40. Cause a gentle stream of oxygen to pass through the solution of sulphurous acid in the flask ; the oxygen carries along with it some of the sulphur dioxide, the presence of which is easily distinguished by the smell of the gases issuing from the bulb tube. On gently heating the bulb containing the platinised asbestos, the two gases, oxygen and sulphur dioxide, are caused to unite. Sulphur trioxide, SO 3 , is hereby produced, the presence of this compound being shown by the dense white fumes which now appear near the orifice of the bulb tube. This property of fuming in the air is characteristic of the trioxide. By means of caoutchouc tubing, adapt to the end of the bulb tube a small glass tube, bent at right angles, and allow this to dip into a little water in a beaker. Continue to heat the bulb, and condense the resulting sulphur trioxide in the water. After a little time test some of this water with barium chloride ; you find that it contains sulphuric acid. You have therefore produced this acid by the combination of sulphur trioxide with water : H 2 + S0 3 = H 2 S0 4 . Experiment IX. Pour about 10 c.c. of strong Nord- hausen sulphuric acid (H 2 S2Q 7 ) into a little retort, to which a small receiver is attached. Ori heating the acid in the retort, fumes of sulphur trioxide are formed, which pass over into the receiver, where they condense to a white crystalline solid : H 2 S 2 7 = H 2 S0 4 + S0 3 . If the receiver be carefully closed, these crystals of sulphur trioxide may be kept for a long time. Allow a drop of water to fall on to one of the crystals : the chemical com- bination is so intense, that it hisses as if it had touched red- Properties of Sulphuric Acid. 85 hot iron. You already know that sulphuric acid is the pro- duct of this reaction. From the experiments in this lesson you learn (1) What are the methods for preparing the two oxygen compounds of sulphur, viz., the di- and tri-oxide. (2) What is the way in which sulphur dioxide bleaches. (3) What is the action of this gas on a solution of iodide of starch. This action, as you will hereafter learn, constitutes the basis of a, widely applicable quantitative process. (4) That sulphur dioxide may be liquefied ; and the meaning of the term permanent gas. (5) That sulphur trioxide is the product of the oxidation of sulphur dioxide, and that this compound, in contact with water, yields sul- phuric acid. LESSON XXIII. PROPERTIES OF SULPHURIC ACID. To make sulphuric acid by the process adopted on the manufacturing scale requires a more complicated arrange- ment of apparatus than is readily put together in the labo- ratory. We shall, therefore, neglect the actual preparation of this substance, and proceed to perform a few experiments with the acid,, which is a liquid in constant use in the laboratory. Experiment /.To a drop or two of sulphuric acid diluted with water, in a test-tube, add barium chloride 86 Qualitative Chemical A nalysis. solution ; a copious white non-crystalline precipitate is at once produced. After boiling, allow the precipitate to settle, pour off the clear liquid, add a little water to the precipitate, shake it up, and again allow it to settle. After having thus washed it several times by decantation, pour over the precipitate a little strong hydrochloric acid; it remains undissolved. Pour away the hydrochloric acid, and add a little nitric acid; the precipitate is unacted upon. Therefore the formation of a white precipitate (barium sulphate), insoluble in acids, when barium chloride is added to any given solu- tion, tells us that sulphuric acid or a sulphate is present in that solution. Experiment IL Heat a little of the acid, and pour it on to a small piece of sugar in a porcelain basin. The sugar is instantly charred; steam is given off, while black masses of charcoal remain. Sulphuric acid chars sugar, which has the composition C 12 H 22 Oii by removing the elements of water, viz., hydrogen and oxygen, and eliminating the carbon. You thus learn (1) In what way sulphuric acid may be recognised. (2) That this acid has a great avidity for water. LESSON XXIV. PREPARATION AND PROPERTIES OF SULPHURETTED HYDROGEN. FIT up an apparatus similar to that shown in fig. 41, and in the flask A place a few small pieces of ferrous sulphide. Cover these with water, and pour a little strong sulphuric acid through the funnel tube into the flask. Sulphuretted hydrogen gas is evolved, and is washed by passing through water contained in the small flask B. The reaction is as follows : FeS + H 2 SO 4 . = FeSO 4 + H 2 S. Allow the exit Preparation of Sulphuretted Hydrogen. 87 tube to dip into a dry gas bottle; place the whole appa- ratus in the draught chamber, and continue the evolution of the gas for some time. Now close the bottle with a well- greased glass plate, remove it, and place in its stead a beaker containing water. Experiment I. With- Fig 4I draw the glass plate, and bring a lighted taper to the mouth of the bottle con- taining the gas. The gas burns with a pale bluish flame, and the inside of the bottle becomes coated with sulphur. In this reaction sulphur dioxide and water are produced together with the sulphur. H 2 S + O 3 = H 2 O + SO 2 and H 2 S + O = H 2 + S. If the gas be mixed with air in quantity sufficient to burn it completely, the first reaction alone takes place. The water in the beaker glass will now be saturated with the gas, the peculiar smell of which it will possess. Experiment II. Prepare solutions of copper sulphate, arsenious oxide, ferric chloride, and barium chloride in water, acidulate them slightly with hydrochloric acid, and add to each a little of the solution of sulphuretted hydrogen. In the first liquid, a black precipitate of copper sulphide (CuS) will be produced ; in the second, a yellow precipitate of arsenious sulphide (As 2 S 3 ) ; in the third, a finely divided precipitate of sulphur ; the fourth liquid will remain clear. By taking advantage of the reaction of metallic solutions to- wards sulphuretted hydrogen, we are enabled to arrange the metals in groups for the purposes of qualitative analysis. (Seep. 1 06.) 88 Qualitative CJiemical Analysis. LESSON XXV. PREPARATION AND PROPERTIES OF PHOSPHORETTED HYDROGEN. ;FiT a cork carrying an exit tube into a small round-bot- tomed flask, supported on a clamp, in which you have already placed a strong solution of caustic potash and a few pieces of phosphorus. Connect the end of the exit FJG. 42. tube, by means of a caoutchouc tube, with the gas tap, and pass coal gas into the apparatus, the cork being loosely held in its place, until it is entirely rilled with it. Now shut the gas stopcock, remove the caoutchouc tube, fit the cork tightly into the flask, and quickly plunge the end of the exit tube under water in a pneumatic trough. On now heating the flask a gas is evolved, each bubble of which, as it passes out of the water into the air, spontaneously inflames, and produces a ring of white smoke (see fig. 42). The reaction which takes place may be thus formulated : P 4 + 3H 2 + 3KHO = 3 KPH 2 2 + PH 3 . Qualitative Analysis. 89 The rings are composed of phosphoric anhydride, formed by the oxidation of the phosphoretted hydrogen (2PH 3 + 8 = P 2 5 + 3 H 2 0). In this lesson you learn by what method phos- phoretted hydrogen is prepared, and also that it is spontaneously inflammable. PART II. QUALITATIVE ANALYSIS. QUALITATIVE ANALYSIS is that branch of Practical Chemistry which treats of the methods of determining the nature of substances, and the way in which their constituents may be separated. By far the greater number of substances may be resolved, by various forces, into parts or constituents, which separately are possessed of properties different from those which characterise the original matter. These parts may, generally, be again broken up ; but ultimately we arrive at certain forms of matter which refuse to yield to any force by means of which we may attempt to subdivide them. These ultimate parts we term Elements ; by their union in definite proportions they form Compounds. For example, a piece of chalk (calcium carbonate) when heated is split up into two groups or combinations of elements carbon dioxide, which is evolved ; and lime, which remains behind. By appropriate means we can further resolve the carbon dioxide into carbon and oxygen, and the lime into calcium and oxygen ; but all attempts to break up the calcium, the carbon, or the oxygen into simpler substances have hitherto been unsuccessful : these three substances, calcium, carbon, and oxygen, are therefore called elements. If, then, we de- sire to know of what substances a given piece of matter is composed, our wish will be satisfied when we have ascer- go Qualitative Chemical Analysis. tained what elements, or what combinations of elements, are present in it. The total number of the elements at present known to us is about 63, but comparatively few of these are of common occurrence, and still fewer have received any practical appli- cation. The operations of Qualitative Analysis may be con- veniently subdivided under the two heads of (i) Analysis bv dry reactions; and (2) Analysis by wet reactions. In determining the nature of a substance by the dry method, we subject it to examination when in the solid state ; for example, we notice if it imparts any peculiar colour to flame ; if it yields a metal when heated with reducing substances at a high temperature; or if, when heated, it imparts a colour to various fluxes, &c. In analysing a substance in the wet way, we subject it to the action of appropriate solvents, and determine the nature of the substances dissolved by the addition of re- agents, themselves also in solution. SECTION I. GENERAL PRELIMINARY OPERATIONS. A. FLAME REACTIONS. THE flame of the Bunsen lamp may be used to detect the presence of very many elements. The Bunsen lamp consists essentially of a metal tube, at the bottom of which a gas burner is fixed ; the lower part of this tube is pierced with holes, through which air enters and mixes with the gas in the tube. These holes are of such a size as to admit an amount of air, which, when mixed with the gas issuing from the burner, is sufficient to oxidise or Flame Reactions. 91 burn it entirely. A non-luminous, very hot flame is thus produced. The Bunsen lamp to be used in the following experi- ments is shown in fig. 43, No. i. At a is a circular cap, by moving which you can regulate the supply of air, so as to obtain a more or less luminous flame. A conical chimney, resting on the gallery (b) of the lamp, serves to protect the flame from draughts of air. The flame is shown in fig. 43. No. 2, of its natural size ; the letters refer to the various portions of the flame, with the properties of which it is necessary that you make your- self thoroughly acquainted. There are three principal divisions, viz. (i) The dark zone, a a, a a, in which the cold, unburnt gas is mixed with about 62 per cent, of air. '(2) The flame mantle, a, ca, b, in which is a mixture of burning coal gas and air. (3) The luminous point aba, which is not seen when the full supply of air is allowed to enter the lamp, but which can be produced by turning the cap, so as partially to close the holes at a, No. i. Examining the flame more in detail, we find the follow- ing six points, which are made use of in the reactions : 1. The base of the flame is situated at a, a very small distance from the summit of the lamp itself. On account of the proximity of the metal tube, and also by reason of the ascending current of cold air, the temperature of this part of the flame is, comparatively, very low. Hence many easily volatilised substances may be recognised by the colours which they impart to the flame when held in this portion of it. 2. The zone of fusion, or point of highest temperature, is situated at /3, somewhat above the first third of the entire height of the flame, and at a distance from the edge of the flame equal to about one-fourth of its greatest breadth. 3. and 4. The lower, and upper oxidising flames: the former of which, situated at y in the outer margin of the 92 Qualitative Chemical Analysis. FIG. 43. g.. N2I. Flame Reactions. 93 zone of fusion, possesses a higher temperature than the latter, which is found at e, the highest point of the non- luminous flame when the draught-holes are wide open. 5. and 6. The lower, and upper reduction flames : the former is at 3, close to the dark central zone : owing to the presence of atmospheric oxygen the i educing powers of this flame are not so great as those of the upper reducing flame, which is situated at y, just over the dark zone, and is formed by lessening the supply of air so as to produce a considerable amount of finely divided carbon or of dense hydrocarbons, but not sufficient to form a sooty deposit on a test-tube full of cold water held, for a moment, at this point. In examining substances by means of these flame reac- tions, the appliances must all be on the smallest possible scale, otherwise so much heat will be carried off by them as to reduce the temperature of the flame to a point at which the proper reaction can no longer be obtained. Many substances to be tested are held in the flame by means of a little piece of platinum wire ; this wire must be so thin that one decimeter of it does not weigh more than 34 mgm. If two little loops be made on the wire, as shown in fig. 43, No. 3, A, these may then be so brought together, by turning the wire round at the point a, as to form a little catch in which the substance to be tested rests. (See No. 3, B.) Such a platinum loop is also very useful for holding decrepitating substances, which should first be ground to fine powder with the elastic blade of a small knife (fig. 44, No. i, p. 97) upon a little porcelain plate, then drawn up on to a square centimetre of moistened filtering paper, which, held in the platinum wire loop, can be burned ; the sample is thus obtained adhering to the wire. Certain substances cannot be held in the flame on the platinum wire, as they either act upon the metal, or do not adhere to it when moistened; these are supported on a piece of asbestos about one-fourth the thickness of an ordinary lucifer-match. 94 Qualitative Chemical Analysis. In fig. 43, No. 4, is shown an arrangement by means of which substances to be tested may be held in the flame for a length of time. A small glass tube is held by the arm, a, attached to the carrier, A ; into this tube a little piece of platinum wire is fused. The carrier, A, is moveable, so that the substance held in the loop of the wire may be moved to any part of the flame, and held there while the phenomena which occur are noted. The arm, d, also attached to the carrier, A, serves to support threads of asbestos, which are often used instead of platinum. Another carrier, B, carries an arm which may clasp a small test-tube containing any substance requiring to be held for a length of time in the flame. From the phenomena noticed when substances are heated we may often learn much concerning them. The following points are more especially to be observed : (1) Emission of Light. Heated on the platinum wire in the hottest part of the flame, different substances emit dif- ferent degrees of light. If the sample and the platinum wire appear equally luminous, the substance is said to be of mean emissive power; if the wire appears more luminous than the substance, the emissive power of the latter is said to be low, while this same quality is called strong or high if the light emitted by the heated substance be more intense than that coming from the platinum wire. (2) The melting point of many substances maybe pretty accurately determined by holding them on the platinum wire, in different parts of the flame, and observing the tints assumed by the wire. The following six different tempera- tures may thus be obtained : (a) below a red heat ; (b) commencing red heat ; (c) red heat ; (d} commencing white heat; (e) white heat; (/) strong white heat. (3) The colour imparted to the flame by volatilised sub- stances may be judged of by holding the sample in the upper Flame Reactions. 95 reducing flame, when the colour appears in the upper oxi- dising flame. If we wish to discriminate between substances which im- part various colours to flame, we may often do so by bring- ing the mixture into the lowest and coldest portion of the flame : the most volatile substance is the first to betray its presence, by imparting a momentary colour to the flame ; this is followed by the next volatile, and so on. But perhaps the most important point you have to notice is the behaviour of substances when heated in the oxidising and reducing flames. I. REDUCTION OF SUBSTANCES. Very many compounds when exposed to the influence of the reducing flame give up the oxygen, sulphur, etc., which they contain, the metals being thereby obtained in the pure state ; to these various tests can then very easily be applied. Bring a crystal of common washing soda (Na 2 CO 3 + ioH 2 O) to the side of the flame, and when the edge begins to melt, smear a common wooden lucifer-match, with the head broken off, with the fused salt. By gently heating the smeared match in the flame you obtain a mass of carbonised wood intermixed with sodium carbonate. A small quan- tity of the substance to be tested is now to be placed on the palm of the hand, and well mixed, by means of the small knife, with a little fused soda crystals. A portion of this mixture you must now cautiously bring on to the end of the prepared match. . This is, perhaps, the most difficult part of the process, as in attempting to make the substance adhere to the match, the carbonised mass is very apt to break off. Heat the match with the substance on it in the lower reducing flame, situated at $ ; the soda effer- vesces; after a few moments withdraw the match, break off the head into a small agate mortar, press it gently with the pestle, adding a little water; the lighter particles of carbon float upon the water, the soda is dissolved, and the heavy reduced metal is left, on pouring off the water, 96 Qualitative Chemical A nalysis. at the bottom of the mortar. After a few washings the metal is obtained almost perfectly pure. You must now examine the small bead of metal. To do this, remove it to a little piece of glass (a piece of a broken flask is the best), and gently dry it over the flame. The colour and general appearance of the small metallic bead will give you some clue to its nature. Copper may be at once recognised by its red colour ; lead, by its bluish-grey colour and its malle- ability ; bismuth and antimony, by their brittleness; iron, by the action of a magnetised steel blade upon it ; and so on. If the metal is suspected to be iron, the small knife-blade is drawn once or twice over a magnet, and then brought near to the spicules : if these are attracted by the blade, the metal, you may almost certainly conclude, is iron. Nickel and cobalt are also magnetic, but not to so great a degree as iron. The metal is further to be tested by being brought into solution and having several wet tests applied to it. Let us take an actual example. Treat a very small quantity of copper sulphate as di- rected above. From the red colour of the metal obtained you conclude that it is copper ; you must, however, make quite sure of this. For this purpose the reduced metal placed on the small glass plate is dissolved by gently warming it with one drop of dilute nitric acid ; the excess of acid is driven off by blowing on the surface of the warm glass ; a drop of water is added, and the corner of a small piece of filtering paper being dipped into the solution, a very little of it is sucked up by the paper. On now bringing a drop of po- tassium ferrocyanide (a reagent used as a test for copper) on to the paper, a brown stain of copper ferrocyanide instantly makes its appearance. Sometimes it is preferable to use small capillary tubes in the application of the wet tests. To form these, heat a piece of wide thin glass tubing, and when soft draw it out slowly, turning it all the while. The thin part of the tube Flame Reactions. 97 FIG. 44. (see fig. 44, No. 4) is now separated from the rest, and cut into lengths of about 6 cm. One of these small capillary tubes is dipped into the solution to be tested; a very small quantity of the solution rises a little way in the tube, from which, by gentle blowing into the other end of the tube, it is expelled on to a small piece of glass ; a drop of the test reagent is also brought on to the glass in a precisely similar man- ner, and after slightly stirring the mixture, a drop of it is again brought into a third capillary tube, when any precipitate or change of colour in the liquid is easily detected. Mix a small quantity of ferrous sulphate with the fused sodium carbonate, bring the mixture upon the charred match, and hold it in the upper reducing area (rj) for a minute or so. Break off the charred mass containing the re- duced metal into a small mortar in which are a few drops of water, 4231 crush it gently with the pestle, and insert the magnetised blade of a knife. The spicules of iron will attach themselves to the blade ; they may be washed, without being detached, by allowing a few drops of water to flow along the knife blade, dried, by holding the blade above the flame for an instant, wiped off on to a piece of filter paper, and dissolved in a drop of hydrochloric acid. Dry the paper carefully over the lamp, and moisten the yellow spot with a drop or two of a solution of potassium 98 Qualitative Chemical Analysis. ferrocyanide : it will be seen to acquire a deep-blue tint owing to the formation of Prussian blue. Treat a little more of the ferrous sulphate on the car- bonised splinter with soda in the reducing flame, break off the head of the match on to a silver coin, and moisten it with a drop of water ; in a few moments the coin will be stained brownish-black. This stain tells you that sulphur was present in the substance tested. By the combined action of soda, charcoal, and the reducing flame on the copper sulphate, soluble sodium sulphide has been formed, which, acting upon the silver, has given rise to a film of black silver sulphide. Almost all sulphates may be thus reduced, and the sulphur recognised. You see how very delicate these reactions in the re- ducing flame are, and how they may be made the means of detecting almost infinitesimal amounts of many substances. As you learn the various wet tests for the metals, you will be able yourself to apply them to the beads obtained in your preliminary flame reactions. But let us now glance at another application of this reducing flame : many of the metals may be obtained, through its influence, in the form of films. The following experiments are only applicable to those elements which are volatile at the temperature of the re- ducing flame. The principal of these are antimony, arsenic, bismuth, mercury, and cadmium. Bring a small piece of arsenious oxide on to a thread of asbestos, by slightly wetting the asbestos between the lips and then touching the oxide with k. Select one or two porcelain basins, 10 to 20 cm. in diameter, and into one pour a little cold water, and hold it close above the asbestos in the upper reducing flame. The arsenious oxide is thus deoxidised, a film of metallic arsenic being deposited on the cold surface of the basin. To this film many tests can now be applied, but these will more properly be performed when Flame Reactions. 99 you have gone through the wet tests for arsenic. Meanwhile you must note the appearance of the arsenical film or mirror. Repeat the above experiment, using an antimony com- pound (antimony trichloride will do) instead of arsenious oxide, and compare the film thus obtained with that given by the arsenic. You at once notice the sooty-black velvety appearance of the antimony mirror. From the appearance of the films you may often be able to tell by what metal they are caused. Volatilise a small quantity of corrosive sublimate (HgCl 2 ) in the manner just described. You thus obtain the metallic film of mercury ; you see how it spreads over the entire under- surface of the porcelain dish, and how unlike it is in this respect to either antimony or arsenic. Although we do not as yet proceed to apply any ' wet tests ' to these metallic films, you will nevertheless perceive the service which may be rendered to the chemist in his qualitative researches by these easily-obtained mirrors. Let us now look at the results obtainable by the oxidising flame. Repeat the experiments which you have just performed, but hold the asbestos in the upper oxidising flame ; you will thus obtain films of the oxides of the metals upon the por- celain, instead of the metals themselves. Obtain thus an oxide film of arsenic, using a small quantity of arsenious oxide. Notice the peculiar lavender tint given to the flame by the arsenical fumes, and remark also the white smoke which rises from the flame, caused by the volatilised oxide of arsenic. On the porcelain you obtain an almost imperceptible film. This, on the application of proper tests, is very easily recognised to be arsenious oxide. Similar oxide films are obtainable from many other metals. From these oxide films others are obtained which are very characteristic, and often of great use in helping us to draw conclusions as to what substances we are dealing with. (i) Iodide Films. To obtain these, the dish on which we H 2 I oo Qualitative Chemical A nalysis. have formed the oxide film is, after being breathed on, placed upon the wide-mouthed well-stoppered glass (fig. 44, No. 5) which contains fuming hydriodic acid and phosphorous acid, obtained by the gradual deliquescence of phosphorus tri- iodide. (If this mixture should cease to fume, the addition of a little phosphoric anhydride renders it again fuming.) (2) Sulphide Films, are most easily obtained from the iodide films by blowing a stream of strong ammonium sul- phide over these, and removing excess of the FIG. 4$. ammon i um sulphide by gently warming the porcelain basin. The ammonium sulphide is contained in a small wash bottle, the exit-tube of which is cut short so as not to dip into the liquid, while the blowing tube passes nearly to the bottom of the flask. (See fig. 45.) The reduction films should be deposited on a glass tube instead of on porcelain when a considerable quantity of the film is required for examination. In this case a tube similar to that represented in fig. 43, No. 4 a, is half filled with water, and it is so arranged as to catch and condense the metallic fumes arising from the substance, which, sup- ported on an asbestos thread by the holder d (see fig. 43), is held in the upper reduction flame. This arrangement may be left for some time, until a sufficiently large film has accumulated on the glass. (As the water in the glass soon boils, it is desirable to put a very small piece of marble into it to prevent ' bumping.') A few elements when heated with certain solutions in the Bunsen flame yield coloured beads which are highly cha- rapteristic of the different metals. These beads are gene- rally obtained by bringing a small quantity of the substance to be tested on to one of the platinum wires (see fig. 44, No. 2), heating it for a few moments in the hottest part of the flame, allowing it to cool, and by means of a capillary tube moistening the mass with the solution used as a test, and Flame. 'Retittioris. 101 FIG. 46. again heating in the oxidising Bunsen flame. Heat a very small quantity of zinc sulphate on the loop of the platinum wire, moisten the bead when cold with cobaltous nitrate solution, and heat again in the upper oxidising flame ; a beautiful green-coloured mass is proof of the presence of zinc. The special application of these flame reactions to the various metals will be described when we speak of these in detail. When we have a mixture of substances each of which colours the Bunsen flame, it is often possible to discriminate between them by viewing the flame in which the mixture is held through coloured glasses, or through a glass prism containing indigo solution. The colours imparted to the flame by different bodies are distinguished as : (i) border colours, produced by the most volatile substances when held in the loop of a platinum wire a very little way outside of the flame, about 2 mm. from the lower part ; (2) mantle colours, produced by holding certain substances in the outer part or mantle of the flame ; (3) flame colours these colours are shown when the more difficultly volatile substances are held in the hottest part of the flame. A glass prism (fig. 46), filled with dilute indigo solution, is very useful in observing certain flames. The base of the prism may conveniently mea- sure about 35 mm. and its length 150 mm. The indigo solution is made by dissolving i part of indigo in 8 parts of fuming sulphuric acid, diluting with 1,500 to 2,000 parts of water, and filtering. The flame is first viewed through the thinner layers of the liquid, and gradually through thicker and thicker layers, by moving the prism horizontally. If small quantities of a sodium salt be mixed with a salt of potassium, the violet colour given to the flame by the latter is completely hidden by the intense yellow of the 1 02 'Qualitative- C'hemicul Analysis. sodium flame ; no sodium rays can pass through the indigo solution, which, however, freely transmits the potassium rays ; if therefore the mixed flame be viewed through the indigo prism, it appears at first of a sky-blue colour, chang- ing, as it is viewed through thicker layers of the solution, to violet, and lastly appearing crimson-red. Other applications of these flame tests with coloured glasses will be noticed under the special tests for the various metals. B. Use of the Spectroscope. Of late years the spectroscope has become of general use in qualitative analysis. The indications afforded by this instrument are of such exceeding delicacy that by its means 7j-o~oi^nr P art f a milligram of sodium can be detected with accuracy. The spectroscope is shown in fig. 47. It consists of a flint glass prism, A, having a refracting angle of 60, resting on a brass plate which again is fixed on an iron or brass support, B. The brass plate carries also the tube c. The tubes D and E are supported by arms, so as to be moveable in a hori- zontal plane about the axis of the support B. On the end of the collimator tube, c, nearest the prism, is placed a lens, the other end being closed by a plate in which there is a vertical slit. The end of the tube E nearest the prism is also furnished with a lens; at the other end is a reduced photographic millimetre scale, which can be seen through the telescope, D. It is generally necessary to obtain two spectra in the field of the telescope at the same time, so that we may com- pare the positions of the lines in each. The arrangement of the vertical slit in the collimator tube, c, enables us to do this. An enlarged drawing of this arrangement is shown in fig. 48, No. i. The upper part, ab, of the slit is open ; the under part is covered by the small glass prism, c. Rays of light falling directly on the upper Use of the Spectroscope. 103 part of the slit pass therefore straight into the tube ^ CN rt *^ Q H i i 3 w" i i-A ^j i ^ ^^ . CO ft 3 - OT3 3 5 P2 S-a h4 H - rf "CO ^^ ^>v, -^ ^<; ^. ^ o 1 f i 8^g. J>^ -T3 ,,, $ l ^1/ rgg c n *^ ? ^ ' s-s Gase o O J1IL 4|ii ^^^s| rt 1 e S. i 111 I 3*111 . d ^^ s H (034) ^S 5> i -f % 5 i 1 t t ; G J] ^ |3 ( l I " a> .2 <5 3 - < 156 Qualitative Chemical Analysis. CL, S < J a w D pa w ~ BS gf S I 1 o u?^8 fl Si^ r rt rt T? f-l c3 o I*. ,0 " ^ u ^ g.s 153 Qualitative Chemical A nalysis. W Pn C .s S u ~ ^ o .2 rt^ c *s g ||sfll-lll 'i ^ ^3 ^ fej -B ^ rt E^'S 2 ^ <5 - ^ S ^^^'S5p.'S.S^^6igrt s W ^SlSi . I8|^" "115 X-J3 ^ S'S . 2-g fl ej^a^Si^s: ^ iliifljli 159 s g 03 1 60 Qualitative Chemical A nalysis. t/3 ^ | I Z3 *"* . "3 I 1^ O fcJO D-i S3 a 3 8 "3 S g _ .0 & 2! - 1 - 1 o if I " A -d 1 ed > > rZ ~ ~ 5 : '93 8 ^3 o ^:-5 s fcj tJ V g II s.J ^5 S J ^ II S S S-2 ^ ^ -^ s s s ^ a | II 1| S s a &. a fl ^j 4-1 Ti rt S S S rt g ^'SH f |: ^S"2 o fa it! w.S I .S ^ 2 ^ 1^ rt ^ rt 11 Ss^- OH-^ OS Mi il! >~> S . i ^-a 2 ^ ^ stl aj oj o S3 g o ^1 - g 8 ^ . ^I'S s j i, ll || iftftiKjjfrKAIfn r }1SlliliiiuiJ! , - B S, -OrtC^ fio^^a^rt-SS J3 , ill! JM lt-1 If Jl: Ml 1 ill! 1 Il?l ^ o 3J: h S s Sir," a-S* a 3^ S2 E?^ " rt z S v2-S-rt 'I 'a^^ of. ^ O .. rtV- -^Trrt a Kr i) rt C 4J T! ",2 g.a . -ss - 1 i 1 2 9^ >. s.a ill ^ ^s W -w >> O Illf - S ?l| S-S.aS .= ! ri ^^ ^ d --ss ; rt o'-o 0)0 ll 1 o > o 0) +-" 12 ^ OH i O O ^> r < ^ .y O CL, C H o Q i-C CJQ ^oo ^ 3 rt ^ bo c a C ^J j ac s x ^ *-". o 'o S fii g i *u fcjj"^ rt u "rt -B 'o s g,i o a rt 163 g Id- 13 W S .-y 04 < * OK s u S SS o IS hyd ri O O _cj rt III ci D "^ CJ '-T! o V r . bfl s u 3 H o <* s x -g S o 2 H g o Cei O oi io o O JJ _ri CL! o ? g S PQ _ 11 .* 111! rT O.'O C "O i|! II ,1111 ..^3 0^3 C C C S 0' to" H A -S v 111 167 aj tH (U , *iS 1 ^ i | tn |g=8.rf .."i t [E INORGANIC ACIDS. B. Silver Nitrate has produced a precipitat "he precipitate is wJiite and soluble /;/ nitric acid. \\\ the acids here will have already been detected e Table L, or by Div. A of this Table. "he precipitate is white and insoluble in nitric acid. part of the original solution for hydriodic acid ( although silver iodide is yellowish in colour, it might present along with the others), est for HYDROBROMIC and HYDROCHLORIC ACIDS a< to XIII. and XIV. (<:), p. 142 and 143. est another portion for HYDROCYANIC ACID by XVI. (c third portion is tested for HYPOCHLOROLIS ACID by adc nitrate, a white precipitate changing to red, then d (from formation of kad oxide PbO 2 \ is produced, itric acid will also have evolved the characteristically hypochlorous acid (HCIO) from the precipitate. 'Ae precipitate is coloured and soluble in nitric acid. C or PHOSPHORIC ACID. hromic acid will have been found among the base 'arsenic acid be present, this must be removed be r ore te phosphoric acid (do this by means of sulphuretted hyi then add to the acid solution ammonium molybdate, ; gently. Filter off any precipitate, dissolve in ammo apply test in III. (a), p. 135. he precipitate is coloured and insoluble in nitric acia Yellow. HYDRIODIC ACID ; test a little of original by XIV. (c), p. 144. ^/rtc/C-. HYDROSULPHURIC ACID ; already detected I L. > _ LC ^S t> C~ H ^ ^ c> U ^ vN ^ *- ft | ^ H <; | '^.a| 4 gl ^*^ue^ tt & 1^5 b cj |'1o|S, 1 OH a, "2 ^ iJ a t J5 h a, J3 rt >-' iJ ^ g 3 * *V w ^ '-3 O! 1 ||| lilj .S |f.|||i IS 6 || b U) D > ill 1 | 8w|^ ! 1-?tik 1 & SL'D : jVJ - ta tlH^il c t .c lation ^A "^1 'O w s " c _ d ^3 a O 4) ^ d - 2 2 ii a Q S ft ^3 I 2 TV i i C I=! z W M S 'G -*_j W3 S'S 2 Q 2 *"rt ^ M TO *^-i ^ B. I * [3 ^ a 'o u su < "c " S j2 S c X ^ T3 rt J1 a ^t/i'aS h .^ ^ "C ^ % ^rt^-s ^ L -rC W tJ fe- u ^ ^2 /.^ 77-4 3 dissolved in acid ( AMINATION OF I .2 "5 13 So ^3 D a ? T3 C & z * Ifaw. S B 2 S g.si sfc^S colour returns on cooitn It is coloured (green), an, ing. It is black. S --3 sl g !l!i 55^^rt _jj ^:s ^ rt u a; rt -" ^J g T .. -^ flifg taa?.s > insoluble in water is X S^ s S S ^^ -z I ^ c/2 .2i 'o 3 -3 S |"o 1 s ^ g 1 ^ ^ J-4 J X N cS )^ T^ fe O ^j HI u o c/3 x -o jJ tT Q iu || \ !! 1 H^ c 'S t ~ l S 3 ^ i. ^ . |j,>g 8 2 fe S \ II I 2 - >^c E3C^B ca 169 -rT i ti i oJ 1 oT s .! ti ^ D-.S fe > 0? i .-^ : 5S 1>2 3 1 1 "rt o tfi y 1 'o S T3 -s 2 o|o, QJ ^Q . rj O W (J j PH ^ C ^ ^j " PE 2 rt o S 1 cJ PH 1 5t3 ^-' o 'ri ^^Tior) 1 1 o 1 rt'CS^ g S ^ f 5 *-< <-H r-f 'S . 52!^ 2.^ rt -^ '^ rC D p ^ .s :s -5 (U C 10 ^0 ^ ^ l> C 'o g -Si 'S Q d, .2 ACIDS. 'a o o II 1 ^S a o C ^ "^ -^ & T3 -^ 1 s 1 'rt d s fe U ^ ^ J ^ B 1 ^ ]tf 1 P^ s < o 1 C! ^ -? .p/ 1 ^ C/2 I G c v ^G .*-> t a c W o ts "3 O 5 i 1 PQ V J U ^o J^ IB _s H o o H r^T ^0 2 W _G T" "^ O 1 | * istilled wi a it 1 "5 ^rt 1 - < CiJ a ^ 1 I ^ 1 .52 1 S rt '0 DH .5 'c w ^o ^ -2 e; i >_; D-. S; JS 1 p la 1 01 a C "S s O -J2 f^ 'i d rj *^, ^5 rj ^2 *KA O < :| | B ^ ^ ^ *< ^ e .? 3 Stas Rhodium . Rh 104-21 Berzelius Appendices. V. Names, Symbols, and Atomic Weights of the Elements. Cont. Element Symbol Atomic weight Observer Rubidium Rb 85-40 Bunsen ; Piccard Ruthenium Ru 104-40 Berzelius Selenium . Se 79-46 Dumas Silver Ag 107-93 Stas Silicon Si 28-10 Dumas Sodium . Na 23-04 Stas Strontium Sr 87^4 Marignac Sulphur . S 32-07 Stas Tantalum . Ta 182-30 Marignac Tellurium Te I28-06 v. Hauer Thallium . Tl 203-64 Crookes Thorium . Th II5-72 Delafontaine Tin . Sn 118-10 Dumas Titanium . Ti 50-00 Pieire Tungsten . W 184-00 Schneider ; Dumas ; Roscoe Uranium . U 118-80 Ebelmen Vanadium V S l '3$ Roscoe Yttrium . Y 61-70 Bahr and Bunsen Zinc Zn 65-16 Axel Erdmann Zirconium Zr 89-60 Marignac INDEX. A CETIC acid, tests for, 152 JT\. Air, analysis of, 29 combustion of, in coal gas, 16 Alkaloids, detection of, by process of Otto and Stas, 200 Uslar and Erdmann, 202 Allotropic, meaning of term, 78 Alum in bread, detection of, 120 Alumina, traces of, detection of, 120 Aluminium, tests for, 120 Ammonia, as group reagent, 119 combination of, with hydrochloric acid, 34 with oxygen, 34 combustion of, 33 preparation of, 31 solubility of, in water, 35 tests for, 35 Ammonium carbonate, as group reagent, 123 sulphide, as group reagent, 126 tests for, 130 Analysis, by dry reactions, 90 by wet reactions, 90 Analysis, meaning of term, 42 Antimony, in organic mixtures, detection of, 195 tests for, 115 Apparatus list, 219 Arsenic, in organic mixtures, detection of, 187 in presence of copper, detection of, 114 tests for, 113 BARIUM, strontium, and calcium, detection of by flame reactions, 127 Barium, tests for, 126 Bases, reactions of the, 107 Beads, coloured, in Bunsen flame, 100 Benzoic acid, tests for, 153 Bismuth, tests for, in Bleaching powder, preparation of, 56 Bloodstains, identification of, 209 Borates, tests for, 137 Border colours, 101 Boric acid, tests for, 137 Boron, in minerals, detection of, 137 Bread, alum in, detection of, 120 Bromides, in presence of iodides and chlorides, detection of, 145 tests for, 142 Bromine, action of, on phosphorus, 54 bleaching action of, 54 detection of, 63 in organic compounds, detection of, 144 preparation of, 52 Brucine, in presence of strychnine, de- tection of, 208 tests for, 205 Bunsen lamp, structure and flame of; 91 use of, 93 /CADMIUM, tests for, 113 V^ Caesium, tests for, 177 Calcium, tests for, 127 chloride, tests for, 39 preparation of pure, 227 Capillary tubes, 96 Calculi, urinary, examination of, 214 Carbon, combination of, with oxygen, 7 monoxide, preparation of, 40 from formic acid, 41 dioxide, decomposition of, by sodium, 38 preparation of, 36 properties of, 32 tests for, 141 Carbonates, tests for, 141 Cerium, tests for, 174 Chemical action, meaning of term, 8 test, meaning of term, 8 Chlorates, tests for, 151 in presence of nitrates, detection of, 150 Chloric acid, tests for, 151 Chlorides, in presence of bromides and iodides, detection of, 145 tests for, 142 Index. Chlorine, action of, on methane, 67 affinity of, for hydrogen, 45 as a bleaching agent, 51 in organic bodies, detection of, 144. oxidising action of, 46 oxygen, derivatives of, 49 preparation of, 43 tetroxide, 52 Citric acid, tests for, 152 in presence of tartaric acid, de- tection of, 158 Cobalt, detection of, 123 Chromic acid, detection of, 121 Chromium, detection of, 121 Colchicine, detection of, 205 Combustion, meaning of term, 15 Compounds, meaning of term, 89 Conine, tests for, 203 Copper nitrate, preparation of, 30 Copper, in organic mixtures, detection of, 112 tests for, 112 in presence of arsenic, 114 traces of, detection of, 112 Corks, boring, 9 Cyanides, analysis of, 146 in presence of hydrocyanic acid, detection of, 198 tests for, 145 DIALYSIS, use of, 184 Didymium, test for, 174 Displacement, downward, meaning of term, 37 upward, meaning of term, 83 Distillation, process of, 20 Dry reactions, analysis by, go preliminary use of, 106 T^ LEMENTS, 89 1^> detection of rare, 170 number, 90 rare, systematic search for, 178 Emission of light, 94 Ethene, combination of, with bromine and chlorine, 69 forms explosive mixture with oxygen, 69 preparation of, 68 Ethine, detection of, 72 in coal gas, 72 preparation of, 71 FAHL ore, analysis of, 130 Ferrous sulphate, as test for nitric acid, 22 Films on porcelain, 98 Filters, how to make, 62 Filtrate, meaning of term, 62 Filtration, 62 Flame, colours, 101 luminous and non-luminous, 73 reactions, 90 Flame, structure of, 73 zones in, 75 Flasks, making three-necked, 16 Fluorides, test for, 138 Formic acid, tests for, 154 Fresenius and von Babo's test for arsenic, 192 GAS bottles, 5 Glass tube bending, 3 sealing of, 80 Gold, tests for, 171 Group reagent, meaning of term, 107 Groups, number, and what they include, 108 Group I., separation of, no II., separation of, 117 III., separation of, 122 IV., separation of, 125 V., separation of, 117 VI., separation of, 130 Guaiacum, as test for hydrocyanic acid, HYDRlODIC acid, preparation of, 57 properties of, 58 tests for, 143 Hydrobromic acid, 58 tests for, 142 Hydrochloric acid, as group reagent, 108 preparation of, 47 pure, 224 solubility of, in water, 47 synthesis of, 48 tests for, 142 Hydrocyanic acid, in organic mixtures, detection of, 197 tests for, 145 Hydrofluoric acid, action of on glass, 60 preparation of, 59 tests for, 138 Hydrofluosilicic acid, preparation of, 63 tests for, 135 Hydrogen, a combustible body, n burning of oxygen in, 15 e_xplosion of with oxygen, 14 lightness of, 1 1 preparation of, 9 Hydrogen, test for purity of, 10 Hydrosulphuric acid, tests for, 148 Hypochlorites, 147 Hypochlorous acid, 147 TNDIUM, tests for, 176 1 Inorganic poisons, in organic mix- tures, detection of, 183 lodates, tests for, 141 lodic acid, 141 Iodides, in presence of chlorides and bromides, detection of, 145 tests for, 143 Iodide films, 99 Index. 237 Iodine, action of on phosphorus, 56 Iodine, action of on sodium, 56 on starch, 56 in organic compounds, detection of, 144 _ preparation of, 55 Iron, tests for, 119 T ANTHANUM, tests for, 174 .1 ; Lead, detection of in organic mix- tures, 195 tests for, no Light, emission of, 94 Lithium, tests for, 177 MAGNESIUM, tests for, 128 Manganese dioxide, use of in making oxygen, 3 tests for, 125 Mantle colours, 101 Marsh's process for detection of arsenic, 187 Meconic acid, detection of, 208 Melting points, 94 Mercury (monad), tests for, 109 (dyad), detection of in organic mix- tures, 195 Metaphosphoric acid, tests for, 136 Methane, combination of with chlorine, 67 with oxygen, 66 forms an explosive mixture with oxygen, 66 preparation of, 65 Molybdenum, tests for, 173 Morphine, tests for, 206 NARCOTINE, tests for, 205 Neutralisation, meaning of term, ^42 Nickel, tests for, 122 Nicotine, tests for, 203 Niobium, tests for, 171 Nitrates, 149 and nitrites, discrimination between, *4? in presence of chlorates, detection of, 150 Nitric acid, preparation of, 19 pure, preparation of, 224 tests for, 149 Nitrites, 147 Nitrogen, in organic bodies, detection of, iS 1 preparation of, 18 properties of, 19 dioxide, combination of with oxygen, 28 combustion in, 28 preparation of, 27 monoxide, preparation of, 23 tetroxide, production of in testing for nitric acid, 21 Nitroub acid, tests for, 147 OPIUM, detection of, 208 Organic poisons, detection of, 196 Orthpphosphoric acid, tests for, 135 Osmium, tests for, 172 Oxalates, tests for, 137 Oxalic acid, in presence of organic matter, detection of, 199 tests for, 137 Oxygen derivatives of chlorine, 49 , combination of with hydrogen, 12 , burning of in hydrogen, 15 supports combustion, 6 tests for, 5 PALLADIUM, tests for, 171 L Perchlorates, tests for, 51 Perchloric acid, 151 Permanent gas, meaning of term, 85 Phosphates, tests for, 135 , traces of, detection of, 136 Phosphoretted hydrogen, preparation of, 88 Phosphoric acid, tests for, 135 Phosphorus, action of on bromine, 54 on iodine, 56 on nitrogen monoxide, 25 detection of, 182 withdrawal of oxygen from air by, _i8 _ Picoline, tests for, 203 Platinum, tests for, 171 Platinum ores, analysis of, 171 Pneumatic trough, use of, 4 Poisons, detection of, 181 Potassium hydrate, preparation of pure, 225 tests for, 129 spectrum of, 129 Potassium chlorate, preparation of, 51 cyanide, purification of from cyanate, 123 Precipitate, meaning of term, 2 Pyrophosphoric acid, tests for, 136 /QUALITATIVE analysis, 89 \.2 subdivision of, 90 Quinine, sulphate, examination of, 207 tests for, 207 RARE elements, detection of, 170 systematic search for, 178 Reagent list, 220 Reagents, pure, preparation of, 224 Reduction of substances in Bunsen flame, 95 Rhodium, tests for, 172 Rubidium, tests for, 177 Ruthenium, tests for, 171 SEDIMENTS, urinary, examination of, 213 238 Index. Selenium, tests for, 171 Silicates, analysis of, 140 Silicic acid, tests for, 139 Silico-fluorldes, tests for, 135 Silicon fluoride, action of on water, 60 preparation of, 60 Silver, tests for, 108 Sodri lime, preparation of, 227 Sodium carbonate, preparation of pure, 227 flame, reaction of, 129 hydrate, preparation of pure, 226 spectrum of, 129 tests for, 129 Solubilities, table of, 228 Spectroscope, direct vision, 105 use of the, 102 Strontium, tests for, 126 Strychnine, in beer, detection of, 207 tests for, 206 Sulphates, tests for, 134 Sulphides, in presence of sulphites and thiosulphates, detection of, 148 tests for, 148 Sulphide films, 100 Sulphites, in presence of sulphides and thiosulphates, detection of, 148 tests tor, 139 Sulphur, combination of with oxygen, 7 detection of, 78 properties of, 77 traces of, detection of, 134 Sulphur dioxide, bleaching action of, 81 detection of, 139 liquefaction of, 80 preparation of, 79 Sulphur trioxide, preparation of, 84 Sulphuretted hydrogen, action of on metallic solutions, 87 as group reagent, in preparation of, 86 Sulphuric acid, free, detection of, 134 properties of, 85 pure, preparation of, 225 tests for, 134 Sulphurous acid, free, detection of, 139 preparation of, 84 tests for, 139 Synthesis, meaning of term, 42 TABLE of solubilities, 228 for examination by Bunsen flame, 156 Table for examination by heating in glass tube, 155 of insoluble substances, 166 for preliminary examination for acids, 165 for separation of inorganic acids, 167 organic acids, 169 solution of substances, 157 treatment of Group I., 159 - II., 160 III., 161 IV., 162 V., 163 VI. 164 of solutions, 158 Tables for weights and measures, 232 Tartaric acid, in presence of citr acid, detection of, 153 tests for, 152 Tellurium, tests for, 173 Thallium, tests for, 170 Thiosulphates, in presence of su phides and sulphites, detection of, 148 tests for, 141 Tin, tests for, 1 16 Titanium, tests for, 175 Tungsten, tests for, 170 T TRANIUM, tests for, 176 \*J Urea, tests for, 212 Uric acid, tests for, 212 Urine, examination of, 210 Urinary calculi, examination of, 214 Urinary sediments, examination of, 213 V ANADIUM, tests for, 177 Veratrine, tests for, 204 WASH-BOTTLE, making a, 64 Water, composed of, 14 Wet reaction, analysis by, 90 "7 INC, detection of, in organic mix- /-* tures, 183 action of on sulphuric acid, TO tests for, 124 sulphate, preparation of, 12 Zirconium, tests for, 174 LONDON : PRINTED BY SPOTTISWOODE AND CO., NEW-STREET SQUARE AND PARLIAMENT STREET MESSRS, LONGMAN & 00,'S TEXT-BOOKS OF SCIENCE, MECHANICAL AND PHYSICAL, ADAPTED FOR THE USE OF ARTISANS AND OF STUDENTS IN PUBLIC AND SCIENCE SCHOOLS, Now in course of publication, in small 8vo. each volume containing about Three Hundred pages, A SERIES OF ELEMENTARY WORKS ON MECHANICAL AND PHYSICAL SCIENCE, FORMING A SERIES OF TEXT-BOOKS OF SCIENCE ADAPTED FOB THE USE OF ARTISANS AND OF STUDENTS IN PUBLIC AND OTHER SCHOOLS. 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