IC-NRLF EMISTRY THE FATTY COMPOUNDS WHITE LEY iementary ^^^^H anuals. ORGANIC CHEMISTRY THE FATTY COMPOUNDS R. LLOYD WHITELEY, F.I.C., F.C.S. PRINCIPAL OF THE MUNICIPAL SCIENCE SCHOOL, WEST BKOMWICH -ATE LECTURER AND DEMONSTRATOR IN CHEMISTRY IN UNIVERSITY COLLEGE NOTTINGHAM LONDON LONGMANS, GREEN, & GO, AND NEW YORK: 15 EAST i6th STREET 1895 Ail rights reserved PREFACE As it is quite impossible to learn organic chemistry properly by reading only, it has been my endeavour in this work, not only to give students an intelligible and connected account of the theory of the subject, but also to provide them with such information as shall enable therii to gain a practical acquaint- ance with it. In furtherance of these aims, cross-references have been copiously inserted ; processes for the preparation of a large number of compounds have been given, with short (but, it is hoped, sufficient) working detail ; and those most suitable for students' work are distinguished by a dagger (f). The principal tests for the best-known compounds are also supplied ; and, finally, numerous illustrations have been introduced. Amongst the many works referred to during the preparation of this Volume, the following have been freely employed : Watts' " Dictionary of Chemistry," Thorpe's " Dictionary of Applied Chemistry," Roscoe and Schorlemmer's "Treatise on Chemistry," and Richter's " Organic Chemistry." I am indebted to Messrs. Matthews and Lott for permis- sion to copy Figures 33, 40, and 44 from their work on " The Microscope in the Brewery;" and to Mr. G. S. Newth for Figures 24, 26, 27, and 28, which are taken from his " Chemical Lecture Experiments." The starches (Fig. 45) were kindly drawn for me by Mr. E. A. Smith, demonstrator of biology in University College, Nottingham iv Preface Many of the remaining figures are from the above-men- tioned dictionaries, by permission of the publishers, while about half of the total number are from photographs of apparatus, which were prepared for me by Mr. J. B. Pursglove. My hearty thanks are due to my late colleagues, Messrs. J. B. Coleman, A.R.C.Sc., and M. E. Feilmann, B.Sc., for many suggestions, and to them and to Mr. John Allport, M.A., of Richmond, for reading through the proofs. R. L. W. CONTENTS SECTION I. INTRODUCTORY SUBJECTS. PAGE CHAPTER I. INTRODUCTION . . . . ...... i CHAPTER II. SOURCES AND PURIFICATION OF ORGANIC BODIES 3 Sources of organic compounds Purification of compounds Determination of the purity of compounds. CHAPTER III. ELEMENTARY ORGANIC ANALYSIS 12 Carbon and hydrogen Nitrogen Halogens Sulphur Phosphorus. CHAPTER IV. PERCENTAGE COMPOSITION EMPIRICAL FORMULAE 24 CHAPTER V. DETERMINATION OF MOLECULAR FORMULAE . . 25 Vapour densities Raoult's cryoscopic method Molecular weights of acids and bases. CHAPTER VI. CONSTITUTION OF CARBON COMPOUNDS . . 34 SECTION II. FATTY HYDROCARBONS ; HALOID PARAFFINS ; MONOHYDRIC ALCOHOLS AND THEIR DERIVATIVES. CHAPTER VII. INTRODUCTORY REMARKS 38 CHAPTER VIII. SATURATED OR PARAFFIN HYDROCARBONS . 40 Methane Ethane Homology Higher paraffins Crude petroleum Nomenclature of paraffins. CHAPTER IX. UNSATURATED HYDROCARBONS 51 Nomenclature of hydrocarbons Olefine series Ethylene Polymerisation. vi Contents I'AGK CHAPTER X. UNSATURATED HYDROCARBONS (continued} . . 59 Acetylene series Acetylene. CHAPTER XI. HALOGEN SUBSTITUTION DERIVATIVES OF THE PARAFFINS 64 Methyl and ethyl halogen compounds Ethylene and ethyli- dene halogen compounds Chloroform Bromoform lodo- form Carbon tetra-chloride, etc. CHAPTER XII. ALCOHOLS . . ... . ; - . ... . 78 Isomerism of alcohols Nomenclature of alcohols Methyl alcohol Ethyl alcohol Fermentation Alcoholic beverages Alcoholometry. CHAPTER XIII. ALCOHOLS (continued] 94 General remarks on alcohols Diagnosis of alcohols Propyl, butyl, and amyl alcohols. CHAPTER XIV. ETHERS 102 Simple and mixed ethers Methyl ether Ethyl ether Metamerism. CHAPTER XV. COMPOUND ETHERS, OR ESTERS, OF THE MINERAL ACIDS 107 Esters of nitrous acid (nitro-compounds) Esters of nitric acid Esters of hydrogen sulphide Esters of sulphurous acid (sulphonic acids) Esters of sulphuric acid. CHAPTER XVI. ALDEHYDES 120 Formaldehyde Acetaldehyde Aldoximes Hydrazones Chloral. CHAPTER XVII. KETONES . 133 Acetone. CHAPTER XVIII. FATTY ACIDS, OR ACIDS OF THE ACETIC SERIES 136 Formic acid Acetic acid Vinegar Chloracetic acid. CHAPTER XIX. FATTY ACIDS (continued} 148 General remarks on fatty acids Propionic, butyric, valeric, palmitic, and stearic acids Butter Oils and fats Soaps. Contents vii PACK CHAPTER XX. ACID HALOIDS, ANHYDRIDES, ETC 157 Acetyl chloride Acetic anhydride Ethyl acetate. CHAPTER XXI. COMPOUNDS OF THE ALKYL RADICLES WITH NITROGEN 162 The methylamines Ethylamines Ammonium bases Hydia- zines. CHAPTER XXII. COMPOUNDS OF PHOSPHORUS AND ARSENIC WITH ALKYL RADICLES 170 Phosphonium iodide The ethyl phosphines Phosphonium compounds The methylarsines Cacodyl derivatives Arso- nium compounds. CHAPTER XXIII. COMPOUNDS OF SILICON, ZINC, AND MERCURY, WITH ALKYL RADICLES 177 Silicon ethyl Zinc ethyl Mercury ethyl. CHAPTER XXIV. Aero AMIDES AND AMIDO- ACIDS . . . . 181 Acetamide Glycine Leucine. SECTION III. CYANOGEN AND CARBONIC ACID DERIVATIVES. CHAPTER XXV. CYANOGEN AND ITS DERIVATIVES . . . .186 Cyanogen Hydrocyanic acid Ferrocyanides Ferricyanides Nitriles Isonitriles Cyanic acid Cyanic esters Isocyanic esters Thiocyanic acids Thiocyanic esters Mustard oils. CHAPTER XXVI. DERIVATIVES OF CARBONIC ACID .... 200 Carbon monoxide Carbonyl chloride Esters of carbonic acid Urea Carbon disulphide Thio-urea Uric acid. SECTION IV. DERIVATIVES OF UNSATURATED HYDROCARBONS. CHAPTER XXVII. DERIVATIVES OF THE OLEFINES .... 206 Chlorethylene Allyl iodide Allyl alcohol Allyl sulphide Allyl mustard oil Acrolein Acrylic acid Oleic acid. CHAPTER XXVIII. ACETYLENE DERIVATIVES ..... 214 Propargyl alcohol Propiolic acid. viii Contents SECTION V. DIHYDRIC ALCOHOLS AND THEIR DERIVATIVES. PACK CHAPTER XXIX. GLYCOLS 216 Glycol Ethylidene glycol Pmacones. CHAPTER XXX. OXIDATION PRODUCTS OF GLYCOLS . . . 222 Glycollic aldehyde Glyoxylic acid Glycollic acid Lactic acids. CHAPTER XXXI. OXIDATION PRODUCTS OF GLYCOLS (continued} 230 Oxalic acid Malonic acid Succinic acids Fumaric and maleic acids. SECTION VI. POLYHYDRIC ALCOHOLS AND THEIR DERIVATIVES. CHAPTER XXXII. TRI-HYDRIC ALCOHOLS AND THEIR DERIVA- TIVES 242 Glycerol Chlorhydrins Nitre-glycerin Glyceric acid Tar- tronic acid Malic acid. CHAPTER XXXIII. TETRAHYDRIC ALCOHOLS AND THEIR DE-' RIVATIVES 251 Erythritol Erythric acid Mesoxalic acid Tartaric acids Citric acid. CHAPTER XXXI V. PENTA- AND HEXA-HYDRIC ALCOHOLS . 259 Arabitol Arabinose Mannitol Dulcitol Gluconic acid Saccharic acid. CHAPTER XXXV. HEXA-HYDRIC ALCOHOLS AND THEIR DE- RIVATIVES . . . . ... . . . . 263 Carbohydrates Dextrose Levulose Cane-sugar Maltose Lactose. CHAPTER XXXVI. CARBOHYDRATES (continued} 273 Starch Inulin Glycogen Dextrin Cellulose Guncotton Collodion. APPENDICES 281 Aceto-acetic and malonic esters Oxidising and reducing agents. INDEX . ..''... 287 ORGANIC CHEMISTRY SECTION I. INTRODUCTORY SUBJECTS. CHAPTER I. INTR OD UCTION. THE science of organic chemistry is of comparatively recent growth; for although much practically useful knowledge was shown in the manufacture of vinegar and of the acetates, of soap and of various fermented liquors, neither the labours of the alchemists, nor those of the medical chemists who followed them, did much to increase our knowledge of the chemistry of organic substances. It is true that during their times a number of substances were isolated anji chemical processes were improved, but it was only about the end of the seventeenth century that the function of chemistry was more fully understood, and that Lemery first separated the study of the science into the three branches of mineral, vegetable, and animal chemistry. Scheele, however, in the latter part of the eighteenth century, was the great pioneer in organic research. Amongst other things he discovered oxalic acid, and distinguished as distinct substances citric, tartaric, and malic acids. Lavoisier about the same time recognised that both animal and vege- table products contain carbon, hydrogen, and oxygen, and more rarely nitrogen and phosphorus ; but the term " organic chemistry " was not originated by him, although the division of the science into the two branches inorganic and organic 13 2 Introduction chemisffy : wi& conseqiieht- *ipo'ii his labours and those of his contemporaries. It was about 1815 that Berzelius first per- ceived that organic, as well as inorganic substances, had constant compositions, and he explained the difference between the two classes of compounds by saying that the organic compounds were oxides of compound radicles}- He, however, still believed that organic bodies could not, like inorganic compounds, be artificially produced ; that is, that they could only result from the action of vital processes in plants or animals. This belief received its deathblow in 1828, when the German chemist Wohler prepared urea synthetically. It had hitherto been supposed unquestionable that urea could only be obtained from urine ; yet Wohler found that when a solution of ammonium cyanate, which can be readily prepared from inorganic sources, was evaporated to dryness, it yielded that substance. In consequence of this result, it became necessary to believe that organic substances, like inorganic, could be produced by artificial means. Some time elapsed before other discoveries were made which confirmed this opinion, but we are now quite released from the trammels of the old ideas, and fully realise that identical laws govern the formation of both inorganic and organic compounds. Notwithstanding this, it is usual, for purposes of study, to separate what is still termed organic from inorganic chemistry. The main reason for this lies in the specific properties of the carbon atom itself. It stands alone amongst the elements in its extraordinary power of combination, not only with other elements, but also with itself. Its atoms can unite with each other, to an almost infinite extent, to form more or less com- plex open and closed chains, in which some of its affinities remain free to combine with other elements. There is, indeed, no theoretical limit to the number of such compounds which are producible. The great number of its possible combinations, therefore, renders it convenient to consider the compounds of carbon apart from those of other elements. 1 By a compound radicle is meant a group of atoms which occurs in a series of compounds, and which can be replaced as a whole by other radicles or by elements, Sources and Purification of Organic Bodies 3 Organic chemistry is therefore the chemistry of the carbon compounds, or (as carbon dioxide and disulphide, and the carbonates are generally studied in inorganic chemistry) it might be even better denned as the chemistry of the hydro- carbons and their derivatives. Having now realised why it is advisable to divide the study of chemistry into two main branches, the characteristics of that which deals with organic chemistry may now be more fully discussed, certain preliminary and general subjects being first considered in order, as below 1. The general sources of organic compounds. 2. Methods employed for obtaining such substances in a pure state. 3. Methods used for the determination of the purity of compounds. 4. Principles of elementary analysis. 5. Calculation of empirical formulae. 6. Processes employed in the determination of molecular weights. 7. Structure of organic compounds. CHAPTER II. SOURCES AND ^PURIFICATION OF ORGANIC BODIES. SOURCES OF ORGANIC COMPOUNDS. ORGANIC compounds are obtained from four* principal sources. Firstly, many are produced as the direct result of vital action, and may generally be prepared from the animal or vegetable substances containing them ; e.g. urea, the alkaloids, whether of animal or vegetable origin, and the sugars. Secondly, others are found in naturally occurring sub* stances, which are decomposition products of animal, vegetable, or other materials,^, ozokerit, hatchettine, fossil- wax, and crude petroleum yield many of the paraffinoid and benzenoid hydro- carbons. 4 Sources and Purification of Organic Bodies Thirdly, many organic compounds are produced as the result of the destructive distillation of other organic substances. Thus from coal-tar, benzene, naphthalene, carbolic acid, and other materials too numerous to mention, have been isolated. The distillation of wood, too, yields wood spirit (methyl alcohol), acetone, and acetic acid ; while that of bones pro- duces many nitrogenous and other substances. Lastly, a vast number of compounds are prepared in the laboratory by directly synthetical processes; for these, how- ever, it must be remembered that some of the substances in the above-mentioned groups usually form the starting-points. PURIFICATION OF COMPOUNDS. It is seldom possible to prepare a compound at once in a state of purity. As a rule it is more or less contaminated with other substances, and has to undergo some special treatment before it is sufficiently pure to be analysed for the determina- tion of its percentage composition. The methods of purification principally employed are the following : i. Recrystallisation. This process is employed when a crystallisable substance is found associated with some other material, either not so readily crystallisable as it ; or which is more soluble in some particular solvent. In this case, a solution is made of the material in question, from which on cooling or, if necessary, after concentration, the more readily crystallisable and less soluble body separates out, leaving the impurities in solution. The crystals are collected on a filter, washed with a little of the solvent, and dried. If still not pure (see p. 9), they are recrystallised till the requisite purity is obtained. Thus, in the manufacture of ordinary sugar, the purified juice is concentrated, and on cooling the sugar separates as crystals from the coloured mother liquor. If the crystals are redissolved and the concentration repeated, the sugar will be obtained in a still purer form. Of course, with an unknown substance it will be necessary to experimentally determine the most suitable solvent to employ. In organic Separation by Solvents 5 investigations, water, alcohol, ether, chloroform, and acetone, amongst other bodies, find frequent employment. 2. Separation by Solvents. In many cases two sub- stances may be separated from each other by employing solvents in which one of the substances only is soluble. Thus if some dried soap is treated with petroleum ether, that solvent will dissolve out from it any unsaponified oil which remains, and leave the soap itself behind. Similarly, if several substances are in solution together, it is frequently possible to add an immiscible solvent, which on shaking up will abstract a dissolved sub- stance from the first solvent, and as the solutions then form two layers of liquid more or less readily, they can be separated by means of the separating funnel (Fig. i). This apparatus permits the more dense liquid to be drawn away first, and the dis- solved substance is then recovered by distilling off the solvent, or by other means as required. 3. Fractional Distillation, both in its simpler as well as in its more complex form, is of very great service in purifying organic substances. As an example of its simpler use may be instanced the purifica- tion of ethylene glycol (p. 218), in which the crude product is simply distilled from an ordinary distillation flask, which is provided with a thermometer connected with a Liebig's condenser (see Fig. 2). The portion of the glycol which distils over while the thermometer rises from 185 to 205 C. is collected apart. That distillate is redistilled, and the fraction collected between 195 and 200 is nearly pure glycol. There are many cases, however, in which it is impossible, by so simple a process of distillation, to separate liquids from each other by difference of their boiling points ; e.g. water boils at 100, alcohol at 78, yet when a mixture of the two substances is distilled, the distillate is always a mixture. FIG. i. 6 So2trces and Purification of Organic Bodies This difficulty of separation depends upon the different solu- bilities of the compounds in each other, their varying vapour pressures, etc. ; but the laws governing the influence of these conditions are too complex to be discussed in any elementary work. 1 In such cases the apparatus employed may be the same as that just described, but the manner of operation differs. The mixture of substances to be separated is placed in the flask, which is then heated, and the temperature at which the liquid begins to distil is noted. It is allowed to go on distilling while the thermometer rises through an interval of three or FIG. 2. five degrees, when the receiver is changed ; that " fraction " coming over during the next similar interval is also collected apart, and the receiver again changed ; and so on till the whole, or nearly the whole, of the liquid has distilled. (See first fractionation in the example, p. 7.) The distillation flask is then cleaned, and fraction No. i is returned to it and redistilled \ that which comes over between the same intervals as before is collected in No. i receiver, and the distillation is stopped whilst No. 2 fraction is returned to 1 Reference may be made, if required, to " Distillation," vol. ii., Watts' " Diet.," new edit. ; and also Thorpe's " Diet. App. Chem.," vol. i. Fractional Distillation the flask, which is again heated, and all that which comes over between the same degrees as the last is added to No. i receiver. Then that which comes over during the second interval is collected in No. 2 receiver ; when fraction 3 is added and a similar course pursued as with fraction 2, till the whole has been refraction ated. This system of redistillation is repeated as many times as is necessary, and it is usually found that the liquid tends to form large " fractions " at certain intervals of temperature (see the third to sixth fractionations in the example given). If these larger quantities are refractionated using smaller differences of temperature, eventually pure compounds may be obtained. The following example, due to Kreis, will illustrate the method. The mixture used was composed of equal weights of benzene and toluene. Volume of distillate in c.c. Temperature intervals. Frac- tion. First Second Third Fourth Fifth Sixth fraction- fraction- fraction- fraction- fraction- fraction- ation. ation. ation. ation. ation. ation. 81-84. . . I I'O 9-0 I7'0 19*5 21'5 22 '0 84-87.. . 2 IO'O 9'5 7'0 5'5 4'5 3'5 87-90. . . 3 14-5 8-5 4'5 4*o 3-0 2'O 90-93 . . . 4 80 5'o 3'5 2-5 i'5 '5 93-96. . . 5 6-0 3'5 3 -0 2'0 2'0 o 96-99. . . 6 5'5 3 '5 2'0 2'5 i'S o 99-IO2 . 7 i 2-5 2'5 . 2'5 i'S i'5 o 102-105 . 8 3'5 4'o 2'5 2'O i'S '0 105-108 . 9 3'5 3'5 2'5 i'5 I'S 5 I08-III . 10 3'5 7'5 I0'5 13-0 4-5 i6 - o Experiment i. Fractionally distil a mixture of 50 c.c. benzene, h.p. 8o'5, and 50 c.c. toluene, b.p. 1 10, collect the fractions every five degrees, and note the large fractions near 81 and 1 10 respectively. The separation into large fractions occurs more rapidly if a modified still head, such as suggested by Wurtz (Fig. 3), or if the dephlegmating apparatus of Linnemann (Fig. 4), Le Bel and Henniger (Fig. 5), or Glinsky (Fig. 6), is employed. A simple column filled with glass beads (Hempel) will also answer the same purpose. All these pieces of apparatus 8 Sources and Purification of Organic Bodies hasten the separation of the constituents of a mixture because they effect a partial condensation of the vapours of the higher- boiling liquids, which thus flow back to the boiling flask and distil over at a higher temperature later. In some cases it is necessary, so as to prevent the decom- position of the substance, to distil it under low pressure, in which case the receiver is fitted air-tight to the condenser and connected with some form of air-pump which will produce the necessary lowering of pressure, and consequent reduction of boiling point. FIG. 3. FIG. FIG. 5. FIG. 6. Distillation in a Current of Steam serves in some cases to separate a compound from impurities which are not volatile under the same conditions ; and in other cases aids the distillation of compounds which would otherwise decom- pose at ordinary pressures. The apparatus for this purpose may be arranged as in Fig. 7, in which the first vessel is a tin can which serves as a boiler for providing the steam, which is blown in a rapid current through the liquid in the flask. The volatile substance is then found either dissolved in, or mixed with water, in the condenser, and is freed from water by extraction with ether, or by other suitable means. Experiment 2. Fit up the apparatus, Fig. 7, and distil some Fractional Precipitation. Boiling Point 9 aniline and water in it, and notice that aniline is present in the distillate. 4. Fractional Precipitation frequently enables us to separate substances from each other. So, if a solution of magnesium acetate is added in small quantities at a time to an ammoniacal alcoholic solution of fatty acids, a series of precipitates is obtained of different compositions. The first fraction will contain principally the salt of the acid of highest FIG. 7. molecular weight, and the last that of the lowest. By decom- posing the fractions with HC1 and refradionating them, a fairly complete separation of the mixture is eventually obtained. DETERMINATION OF THE PURITY OF COMPOUNDS. If possible, the purity of an organic compound should always be checked before analysis, by a determination of either its boiling point or its melting point. Substances to which these tests cannot be applied, must be purified until they are shown by analysis to possess the theoretical percentage com- position ; or, if they are newly discovered bodies, until after repeated purification they are found to have an unvarying composition. i. Determination of Boiling Point. Every substance io Sources and Purification of Organic Bodies capable of ebullition without decomposition possesses, if pure, a constant boiling point, and the determination of this " constant " is very important for confirming the purity of such a body. The ordinary method of performing the operation is to place some of the compound in a tubulated distillation flask fitted with a thermometer as shown in Fig. 8. Heat is then applied, and as soon as the thermometer is constant the temperature is noted. If possible, the whole of the mercury thread should be exposed to the vapour of the substance being tested ; if, however, that is not possible, another small ther- mometer may be fastened to the stem of the first-named in such a fashion that its bulb is fixed about the middle of the exposed mercury thread. The following correction can then be applied, and gives a fairly correct result : Let N be the number of degrees over which the mercury is not heated, T the temperature as read on the thermometer, and / the mean temperature of the mercury column not heated by the vapour (this is given by the small thermometer). The cor- added to the observed temperature is FIG. rection to be o-oooi43(T - /)N. In accurate determinations, the barometric reading should be taken and corrected to o. The following corrections may be applied : (i.) For water or the lower alcohols, = (p (ii.) for other liquids, = (p 760)-^ - , where is the true boiling point, p the atmospheric pressure, and t the observed boiling point. If the amount of substance to be tested is small, since the Melting Point II vapour will easily become superheated, too high a temperature may be registered. This may be prevented by wrapping round the bulb of the thermometer either a little cotton wool or, for high temperatures, a little asbestos, which keeps the bulb moist. Experiment 3. Determine the boiling points of absolute alcohol and of aniline by the method described, and in the latter case apply the correction for the mercury thread exposed to the air. 2. Determination of Melting Point. Pure substances v/hich fuse without undergoing change possess a constant melting point, which may be deter- mined by the aid of the apparatus shown in Fig. 9. This consists of a small test-tube, or a piece of thin quill tubing, 4-5 mm. in diameter, which is drawn out into a capillary of about i *5 mm. external diameter, and the fine end of the tube fused up. For the estimation, a small portion of the solid whose melting point is required is intro- duced into the tube at the top of the capillary portion. The tube is fastened by means of fine wire or a small indiarubber ring to the bulb of a delicate thermometer, as shown in the figure. The whole is next suspended in a beaker that contains a transparent liquid which boils at a higher temperatufe than that required to liquefy the solid. The liquid is then gently heated while being continuously "stirred by the twisted glass rod. As soon as the substance melts, the temperature is noted. This ex- periment should be repeated two or three times, and the mean of the results taken as the correct melting point. For certain substances, e.g. fats, it is advisable to leave the end of the tube open. Some of the compound is then melted and the fine end of the tube inserted in it. That FIG. 9. 12 Elementary Organic Analysis which enters is allowed to solidify there, and the tube is attached to the thermometer and heated in the bath as before; but the temperature at which the liquid rises in the tube is taken as the melting point of the solid. 1 Experiment 4. Ascertain the melting points of chloral hydrate and of urea, after drying them between filter paper. CHAPTER III. ELEMENTARY ORGANIC ANALYSIS. HAVING established the purity of an organic substance, the next step is to ascertain its elementary composition. This is determined by ultimate analysis, either qualita- tive or quantitative, as may be requisite. The number of elements usually present in naturally occurring substances is small, although most of the known elements may be found in one or other of the artificially prepared compounds. The ordinarily occurring elements are carbon, hydrogen, and oxygen, more rarely nitrogen ; these are sometimes termed the organogens. Less frequently sulphur, phosphorus, the halogens, arsenic, and silicon are found ; other elements are rarely present. All substances under investigation must be subjected to qualitative analysis before they are quantitatively examined, as their qualitative composition frequently determines the method to be employed for their quantitative analysis. In the following pages the qualitative tests for the elements immediately precede and are associated with the like quantita- tive ones. Carbon and Hydrogen. Carbon may frequently be detected by the blackening which occurs when the substance 1 When a solid has had to be melted for insertion in the tube, it is best to allow it to remain a day before taking the melting point ; this precau- tion will obviate inaccurate results in those cases where an abnormal result is obtained after recent fusion. Estimation of Carbon and Hydrogen 13 is heated on platinum foil or in a test-tube. If the dis- coloration is due to separated carbon, this will disappear wholly or in part on continued ignition, and only leave as ash any metallic residue. Blackening due to the separation of carbonaceous matter also often happens when a compound is heated with concentrated sulphuric acid. Many compounds, however, do not give these results, in which case the carbon may be detected either by burning them in a current of oxygen, or by mixing them with cupric oxide in a tube, and heating the mixture to redness. By these means the carbon is oxidised to CO 2 , which is detected by passing the evolved gases through lime-water. A simple apparatus, such as shown in Fig. 10, may be employed for FIG. 10. performing this test, and will at the same time demonstrate the presence of hydrogen by the condensation of moisture which will occur in the bulb-tube. If the amount of sub- stance tested is small, the hydrogen can be detected best by passing the gases over dry P 2 O 5 , which readily deliquesces in the presence of moisture. Of course, for these tests the substance itself must be perfectly dry. Experiment 5. Prove the presence of carbon and hydrogen in sugar, starch, or gelatine by either of the above methods. For the Quantitative Estimation of Carbon and Hydrogen, the method employed to-day is essentially that devised by Lavoisier, which was carried to a high state of perfection by Liebig. It depends upon the reaction just illustrated in describing the qualitative detection of these elements, i.e. oxidising them to carbon dioxide and water Elementary Organic Analysis either by means of oxygen or air, or of some oxidis- ing substance such as CuO or PbCrO 4 . The weights of the carbon dioxide and water pro- duced from a given weight of material are ascer- tained, and from them the corresponding amounts of carbon and hydrogen are easily calculated, be- cause /j- of the weight of the CO 2 is carbon, and g- of the weight of the H 2 O is hydrogen. When only carbon, hydrogen, and oxygen are present, the process is quite simple; but if ni- trogen, sulphur, or the halogens occur, it requires suitable modification. Open-Tube Method. The method which is now usually employed may be called the open- tube method, to distin- guish it from the earlier or closed-tube process, in which one end of the combustion tube is closed by fusion. The combustion is performed in a current of air or of oxygen, and aided by copper oxide, and the products are absorbed by Estimation of Carbon and Hydrogen calcium chloride or concentrated sulphuric acid, and caustic potash or soda-lime respectively. The process is carried out as follows, in the apparatus shown in Fig. n. A tube, DD', about 85 cm. in length, 14-16 mm. in diameter, and made of hard Bohemian glass i -5-2 mm. thick, is thoroughly cleaned and dried. A strip of copper gauze a, 25-30 mm. wide, is made into a roll which fits the tube tightly, and pushed into it to about 3 cm. from one end. The tube is next filled to within 25-30 cm. of the other end with copper oxide, preferably made from wire, which is kept in posi- tion by another roll of gauze b. A space is then left for the introduction of the platinum or porcelain boat c, and another plug of wire gauze arranged to be easily removable is put in at d. The tube so prepared is placed in a combustion furnace, which in the illustration is Erlenmeyer's furnace, and con- sists essentially of a number of Bunsen burners, 2 aceta ' ldehyde . 2C 2 H 4 O + 2H 2 O. Carboxyl Acids are produced when tne j c jj Q oxidation of the alcohol is carried further [ 2 4 ?' ., still, C 2 H 5 OH + 2 =C 2 H 4 2 + H 2 0. J Carbon acids yield a similar series of derivatives to those just mentioned, in which it will be seen that the group CH 3 .CO', acetyl, recurs, just as in the others there is always present the group C 2 H' 5 , ethyl. Thus Acetic Acid ... ... ... CH 3 .CO.OH yields Acetyl or Acetic Chloride ; ... CH 3 .CO.C1 Acetamide ... ... CH 3 .CO.NH 2 and Acetic Anhydride, ... ... CH 3 .CO-^^ or Acetyl Oxide ; ... ... CH 3 .CO-^ 40 Paraffin Hydrocarbon METHOD OF STUDY. The student is strongly advised to first study Sections II. and III., omitting all hydrocarbons containing more than two carbon atoms and their derivatives. Then to go through those sections again, mastering the general reactions and pro- perties of the various series of compounds, as well as studying the higher members of such groups. After that the other sections can be taken in turn. It must also be remembered that the only way in which the student can really learn the subject is by acquainting hirn- self practically, not only with the appearance of the compounds or with the tests for recognising them, but with the reactions and methods employed in their production. For this purpose a number of the preparations, processes for which are given, should be undertaken. Those which are marked by a dagger (f) are suitable for such purpose ; and the purity of the com- pounds prepared should be checked, as far as possible, by a determination of their boiling or melting points. It may also be noted, once for all, that the simple mole- cular formulae assigned to the compounds mentioned in this work are usually supported by determinations of their mole- cular weights ; so that, when reasons for assigning constitutional formulae are discussed, that fact is constantly assumed. Contractions. b. p. = boiling point; m.p. = melting point; sp. gr. at ~ = specific gravity at 15 compared with water at 4. CHAPTER VIII. SATURATED OR PARAFFIN HYDROCARBONS. IN systematically studying the carbon compounds, it is both most natural and most convenient to commence with the simple compounds of carbon and hydrogen, or hydrocarbons, sometimes also termed the hydrocarbides. It is also "most natural to start with the saturated hydro- carbons, of which the simplest member is methane, or marsh gas, CH 4 . A series of hydrocarbons is formed from this by Methane 41 successive increments of CH 2 , because when a hydrogen atom is displaced by the group CH 3 , the total increase in the compound is only CH 2 . Also if four is the free valency of the first carbon atom, Since two valencies are saturated by the carbon atoms themselves for every addition of one carbon atom, the increased valency of a saturated compound will not be four, but two, or the general formula will be C M H 2n+2 , where n is the number of carbon atoms present. METHANE OR PARAFFIN SERIES, C n H 2n+2 Methane, CH 4 , marsh gas, methyl hydride, is the first member of the series, and is very widely distributed. It occurs in the gases which escape from the surface of the coal in coal-mines, and since it forms, when mixed with sufficient air, a highly explosive mixture, it renders coal-mining a dangerous occupation, the danger of which can only be overcome by highly efficient ventilation and the use of safety-lamps. It is produced when organic matter decomposes under water, hence the name " marsh gas." Huge quantities of methane, mixed with hydrogen and other hydrocarbons, are given off from the Pennsylvanian oil-springs, and are collected and conveyed in pipes to a distance for use as fuel. It is also evolved from mud volcanoes in Italy, the Crimea, and other places; and, finally, is produced when carbonaceous matter undergoes dry distillation, and is thus present, for example, in large amounts in ordinary coal gas. (*i) Methane is usually prepared by heating sodium acetate with soda-lime, the reaction being represented by CB 3 .COONa + NaOH = CH 4 + Na 2 CO 3 Note. Reactions marked with a star (j) are types of general reactions. Process. A mixture of three parts soda-lime and one part of the acetate is strongly heated in a copper flask or a piece of iron tubing closed at one end, and the gas collected over water in the ordinary manner. A glass vessel may be employed, but is very likely to be cracked if the materials are not dry. Methane prepared in this manner is always mixed with about 8 per cent, of hydrogen and some ethylene. 42 Paraffin Hydrocarbons (*2) A better way of preparing it is by acting with the zinc-copper couple on a mixture of equal volumes of methyl alcohol and methyl iodide CH 3 I 4 CH 3 .OH 4 Zn = CH 4 4 ZnI(OCH 3 ) Process. Dry zinc filings are heated with one-tenth their weight of copper powder (obtained by reducing granulated CuO) till they just become yellow, and some of the couples so formed are introduced into the wide- necked flask fitted with a drop funnel and scrubber tube shown in Fig. 24. The scrubber contains granulated zinc which has been immersed in a solution of copper sulphate, and is fitted with a delivery tube. When a mixture of equal parts of methyl alcohol and methyl iodide is allowed to fall upon the couple, methane is evolved, is freed from vapour of CH 3 I by the scrubber, and may be collected in the usual manner. Other interesting ways of formation of methane are (*3) its production in a pure condition by decomposing zinc- methyl (p. 1 80) with water Zn(CH 3 ) 2 4 2H 2 = 2CH 4 4 Zn(OH) 2 or (4), when water vapour or H 2 S is mixed with CS 2 and passed over heated copper, the following reactions occur : CS 2 -f 2H 2 S 4 8Cu = CH 4 4 4Cu 2 S CS 2 4- 2H 2 O 4- 6Cu = CH 4 4 2Cu 2 S + 2CuO while, finally, (5) when carbon monoxide and hydrogen are subjected to the action of electricity in an induction tube, methane is formed in small quantity. Reactions No. 4 and No. 5 should be carefully noted, as by means of them the gas can be synthesised from inorganic materials. Properties. Methane is a colourless, odourless gas, slightly soluble in water, more so in alcohol. Its specific gravity is 0-559 (air = i). It is inflammable, but its flame has very slight illuminating power, the whitish flame usually obtained being due to the traces of ethylene produced during FIG. 24. Ethane 43 its preparation, from which it can be freed by washing it with strong H 2 SO 4 . It forms an explosive mixture with air CH 4 + 2 O 2 - CO 2 + 2H 2 O Intense cold and pressure condense it to a liquid of specific gravity 0*415, which boils at -164 (Olszewski). It is decom- posed by the passage of an electric spark (see Formation 5), carbon and hydrogen being freed and some acetylene formed. Methane resists the action of HNO 3 and P 2 O 6 , but a mixture of it and 2 volumes of chlorine exposed to direct daylight explodes with the formation of hydrochloric acid and free carbon; in diffuse daylight, however, substitution occurs with the production of CH 3 C1, CH 2 CL, etc. Experiment n. Prepare methane from sodium acetate, and note (i.) its inflammability ; (ii.) its explosive power when mixed with twice its volume of oxygen or ten times its volume of air. Ethane, C 2 H 6 = CH 3 .CH 3 , Ethyl hydride, dimethyl, the second member of the paraffin series, is found in solution in the crude petroleum of Pennsylvania and in the gases evolved from oil-wells. Ethane can be prepared in a state of purity (*i) by decomposing zinc ethyl with water; but a useful method for ordinary purposes is (*2) the decomposition of ethyl iodide by the Zn-Cu couple in presence of alcohol or 1 TT C 2 H 5 OH + C 2 H 5 I + Zn - C 2 H 6 + Zn^ Process. An apparatus similar to that described for the preparation of CH 4 can be employed, with the addition of scrubbers containing alcoholic soda, bromine water, caustic soda, and lime respectively, in order to free the gas from various impurities, which are absorbed by the reagents named. If, then, a mixture of alcohol and ethyl iodide is added to the Zn-Cu in the flask, and the whole heated to 80, gas is obtained which after scrubbing contains 98 per cent, ethane and no other combustible gases. (*3) Another important method for the synthesis of ethane is that in which methyl iodide is treated in ethereal solution with metallic sodium C^i 1 ! , XT r^tr : T i + Na 2 = -f sNal V'tls : > r^TT 44 Paraffin Hydrocarbons while (*4) when potassium acetate is subjected to electrolysis, it decomposes as follows : CH 3 |COOK ) C H 3 [ + 2H 2 O = -f 2CCX + 2KOH + Ho CH 3 :COOKJ CH 3 the C 2 H 6 and CO.j being evolved together at the positive pole. Both the last two methods of formation are important, as they give an important clue to the constitution of ethane. Properties. Ethane is an odourless, colourless gas, which is condensible to a liquid at 4, under a pressure of 46 atmo- spheres. It is inflammable, and has greater illuminating power than methane. It is almost insoluble in water, but alcohol dissolves i '5 volumes of the gas. With chlorine in diffuse daylight it forms substitution products. HOMO LOGY. We have now studied the properties of two hydrocarbons whose formulae differ from each other by CH 2 . Thus ethane can be looked upon as derived from methane by the substi- tution of the radicle methyl, CH 3 , in place of one of its hydrogen atoms, or as formed from two molecules of methane by the elimination of an atom of hydrogen from each, with subsequent linkage of the radicles remaining H . . H H H I : : I II H C H + H C H = H C C H + H. I : i I II H H H H and this reaction is indirectly realised by the formation of ethane from methyl iodide and sodium (p. 43). If, instead of methyl iodide, ethyl iodide, C 2 H 5 I, is employed, a hydrocarbon butane, C 2 H 5 .C 2 H 5 , is formed; and if a mixture of the two iodides is used, the hydrocarbon propane, CH 3 .C 2 H 6 , results. That is CH 3 .CH 2 I + CH 3 I yield CH 3 .CH 2 .CH 3 , and CH 3 .CH 2 .I + CH 3 .CH 2 I yield CH 3 .CH 2 .CH 2 .CH 3 These hydrocarbons are, with methane and ethane, the Higher Members of the Paraffin Series 45 first members of a series of hydrocarbons which differ from each other by CH 2 ; and such a series of hydrocarbons, or of their derivatives, is termed a Homologous Series, while the individual members are called Homologues. HIGHER MEMBERS OF THE PARAFFIN SERIES. Among the principal members of the paraffin series are Methane, CH 4 Pentane, C 5 H 12 Ethane, C 2 H 6 Hexane, C 6 H 14 Propane, C 3 H 8 Heptane, C 7 H 16 Butane, C 4 H 10 Octane, C 8 H 18 The paraffinoid hydrocarbons occur in large quantities in the petroleum which is found in many parts of the world, but notably in North America and Burmah. The deposits of crude paraffin, known as fossil wax and ozokerit, found in Galicia, Roumania, and other places, and the products of the distillation of brown coal and bituminous shale, also yield considerable quantities. Caucasian petroleum contains only small quantities of the paraffins. Crude petroleum is a mixture of liquid and solid hydro- carbons, and possesses the specific gravity 078-0-88, its colour varying from pale yellow or brown to black. Its chemical composition varies very much, and the hydrocarbons present are by no means confined to the methane series ; while, besides hydrocarbons, it also contains small quantities of bodies which contain nitrogen and sulphur. Purification of Crude Petroleum. To prepare this complex mixture for use it undergoes fractional distillation. In America two fractions are distilled from the crude oil still, the " benzine " distillate, and that of the " burning oil." The residue is then transferred to another still, where it is distilled till coking takes place ; the resulting products yield more burning oils, oils suitable for lubricating purposes, vaseline, and paraffin. From the " benzine " fraction further distillation separates the following different products : (i.) Cymogene, b.p. o C, sp. gr. about o - 6oo, which is principally butane ; (ii.) rhigolene, b.p. 18*3 C., sp. gr. o - 6oo ; (iii.) petroleum ether, b.p. 70-90 C., sp. gr. o'65o-o'666, which consists of pentane and hexane ; (iv.) gasoline, b.p. 70-90 C., sp. gr. o'666-o'69o ; (v.) naphtha, b.p. 80-110 C., 46 Paraffin Hydrocarbons sp. gr. 0^690-0700 ; (vi.) ligroine, b.p. 80-120 C,, which is mainly heptane and octane, sp. gr. 0710-0730; and (vii.) deodorised benzine, b.p. 120-150 C., sp.gr. 0730-0750. Of these bodies the first two are liquefiable by cold or pressure, and find use for producing artificial cold ; numbers iii. to vi. are used as solvents in different processes ; numbers v. and vi. are used in sponge lamps ; while the benzine is used as a substitute for turpentine as a cleansing material. 1 Both the benzine and the burning oil from the first distillation are deodorised by treatment with sulphuric acid, followed by washing first with water and then with dilute caustic soda, when the latter oil forms the ordinary petroleum, " kerosene," or mineral sperm. From the distillate from the tar stills paraffin wax is separated, after washing with acid and soda, by crystallisation from the more liquid hydrocarbons with which it is associated. The more pasty hydrocarbons find employment in the preparation of vaseline, while those between them and the burning oils are used as lubricants. Since many of these oils evolve combustible vapour at very low temperatures, their use in ordinary lamps would be excessively dangerous. To prevent this danger, it has been enacted in this country that oil whose vapour flashes below 37-8 C. when a light is applied in open cups must not be sold for lighting purposes. As many circumstances modify the accuracy of this test, it is now performed in a closed tester specially designed by Prof. Abel, in which the flashing point is allowed to be 227. Besides the oily and solid paraffins obtained in quantity from crude petroleum, large quantities of paraffinoid hydrocarbons are present, along with defines, etc., in the oils obtained by the dry distillation of paraffin shale, which is so largely carried on in the south of Scotland. The crude oil is refractionated and deodorised somewhat similarly to the oils from the crude petroleum, with the production of " naphtha," " burning oil " (paraffin oil), " lubricating oils," and " paraffin wax." From the above-mentioned products, prepared from natural sources, it is possible, by special purification with H 2 SO 4 and HNO 3 and subsequent fractional distillation, to prepare pure paraffins ; but before considering any of the higher members 1 This must not be confounded with the benzene obtained from coal- tar oils. General Remarks on the Paraffins 47 of the series it will be wise to study their general methods of formation and properties. GENERAL REMARKS ON THE PARAFFINS. The following reactions which have been illustrated in studying methane and ethane, are general in their application to the preparation of paraffins. 1. Heating the acids of the acetic series with alkalis or alkaline earths. For higher members sodium methylate re- places the alkalis. 2. The action of the Zn-Cu couple on alkyl 1 iodides. 3. The decomposition of zinc alkyls by water. 4. The action of metals such as sodium, or reduced silver or zinc at 150 upon alkyl iodides. Sodium is the most con- venient, as it acts at a low temperature ; it is often necessary to modify the violence of its action by dilution with ether. 5. The electrolysis of the fatty acids. Besides the above may be mentioned : 6. The reduction of alkyl iodides by such reagents as Zn and H 2 SO 4 , sodium amalgam, or HI. Properties. The members of this group of hydrocarbons are distinguished by their chemical indifference; hence the name " paraffins " which is from the word " paraffin " (parum affinis\ a term first applied to the white crystalline product obtained by Reichenbach from wood-tar. They are not attacked by KOH, by concentrated H 2 SO 4 , and hardly by concentrated HNO 3 at ordinary temperatures. If, on the contrary, they are heated with dilute HNO 3 , H 2 CrO 4 , or MnO 2 and H 2 SO 4 they undergo slow oxidation, CQe and H 2 O princi- pally resulting, although according to circumstances acids are also formed ; strong HNO 3 acts upon the higher members, forming nitro-paraffins. Since they are saturated compounds they do not form additive compounds with the haloid acids, and are not absorbed by H 2 SO 4 or bromine. Chlorine and bromine act on them, replacing hydrogen and forming haloid 1 The term "alkyl" or "alcoholic" radicle is applied to the residual group of atoms derived from a paraffin hydrocarbon by the loss of one atom of hydrogen : thus CH 4 gives CH' 3 , C 2 H 6 gives C 2 H' S . 48 Paraffin Hydrocarbon. substitution derivatives, one molecule of the haloid acid being formed for every atom of hydrogen which is thus replaced C 2 H 6 + C1 2 = C 2 H 5 C1 + HC1 The lowest members of the series methane, ethane, and propane are gases at o, above that to tridecane inclusive they are liquids, and the remainder are solids. The paraffins are almost or entirely insoluble in water; in alcohol the gases are slightly soluble, the liquids readily so, and the solids little soluble, the solubility decreasing with increase of molecular weight. The specific gravities of the liquid and solid paraffins increase with the molecular weight, but never reach unity. The boiling points of similarly con- stituted hydrocarbons increase (with each increment of CH 2 ) by decreasing amounts \ until after nonane every increase is about 19 till the limit of temperature is reached at which the hydrocarbons boil under ordinary atmospheric pressure without decomposition. HIGHER PARAFFINS. Propane, C 3 H 8 , CH 3 .CH 2 .CH 3 , propyl hydride. Propane occurs in crude petroleum. It may be prepared according to Schorlemmer's method by the reduction of normal propyl iodide, or by the action of sodium on a mixture of C 2 H 5 I and CH 3 T. Properties. Propane is a colourless gas which at 25 to 30 C. condenses to a liquid, b.p. 17 C. It is inflam- mable, is slightly soluble in water, more so in alcohol. Chlorine forms both primary and secondary propyl chlorides, CH 3 .CH 2 .CH 2 C1 and CH 3 .CHC1 2 . Its constitutional formula follows from its formation from C 2 H 5 I and CH 3 I, and from the fact that there is only one formula possible if the con- siderations mentioned on p. 34 are kept in mind. Paraffins, C 4 H 10 , or Butanes. Although there is only one possible form of the hydrocarbons, CH 4 , C 2 H 6 , and C 3 H 8 , when we consider those containing four or more carbon atoms, it can be easily shown that those atoms can be linked together in more than one manner ; thus there can be two compounds with the formula C 4 H 10 , as given on p. 49, Butanes, Pentanes 49 This, then, is the first example of a fact which makes the difficulty of elucidating the constitution of organic bodies much greater, viz. that it is frequently possible for bodies that possess identical percentage composition and the same molecular weight to differ very materially in chemical and physical properties, and so evidently to be very differently constituted. This phenomenon is called isomerism, and the substances which differ in this manner are termed isomers, or are said to be isomeric with each other. How the two butanes can be formed will be seen if the () (*) formula for propane, CH 3 .CH 2 .CH 3 , is considered. There it will be noted that hydrogen atoms linked to the carbon atoms a and b evidently bear different relations to the molecule, since a is linked to two other carbon atoms, while b is attached to only one. Let, then, a hydrogen atom attached to b be re- placed by CH 3 , and the formula for the butane produced is () (*) CH 3 .CH 2 .CH 2 .CH 3 . If, on the contrary, an atom attached to g a is replaced, then the butane is CH 3 .CHCprT 3 - The former is called the normal (n), the latter the iso hydrocarbon. n-Butane, CH 3 .CH 2 .CH 2 .CH 3 , butyl hydride, di-ethyl, occurs in petroleum, and is formed from ethyl iodide by the action of sodium 2 CH 3 .CH 2 j I + Na 2 = CH 3 .CH 2 .CH 2 .CH 3 + 2 NaI hence its formula. It is gaseous at ordinary temperatures, but on cooling forms a liquid, b.p. i, sp. gr. 0*6. Iso-butane, (CH 3 ) 3 CH, tri-methyl-methane, formed when zinc and water act on tertiary butyl iodide (CH 3 ) 3 CI, is a gas which condenses to a liquid, b.p. 17. Pentanes, C 5 H 12 . Of the hydrocarbons with this general formula there are three isomers 1. Normal pentane, CH 3 .CH 2 .CH 2 .CH 2 .CH 3 2. Iso-pentane, 3 >CH.CH 2 .CH 3 3. Tetra-methyl-methane, 5O Paraffin Hydrocarbons n-Pentane is found in petroleum, in resin oil, and in cannel-coal tar. It is a colourless, inflammable liquid, b.p. 37, sp. gr 0-633 at if?? nas an ethereal odour, and is attacked by chlorine with the formation of primary and secondary chlorides. Iso-pentane occurs in petroleum and cannel-coal tar. It can be formed from iso-amyl iodide or zinc iso-amyl by general methods. It is a mobile liquid, b.p. 30 G, sp. gr. 0*6248 at -j-fr. It burns with a brilliant white flame. Tetra-methyl-methane, obtained from tertiary butyl iodide and zinc methyl 2 C(CH 3 ) 3 I + Zn(CH 3 ) 2 = 2C(CH 3 ) 4 + ZnI 2 is a colourless liquid, b.p. 9-5 ; it can be frozen to a solid, m.p. 20. The constitutional formulae of these substances follow from their methods of formation. Hexanes, C 6 H 14 . Of these there are five forms, whose formulae are i. Normal hexane, CH 3 .GH 2 .CH 2 .CH 2 .CH 2 CH 3 2. Iso-hexane, C*T-T 3. r~T-T /""pr r^T-T 4. Methyl-di-ethyl-methane, ci/CH 5. Tetra-methyl-ethane, The number of isomers rapidly increases as the series is ascended, until the number is theoretically almost unlimited. Thus for C 12 and C^ there are theoretically 355 and 802 different forms respectively. It is, however, very doubtful if they would be distinguishable if prepared. Nomenclature of Paraffins. If these different groups of hydrocarbons are carefully examined, it will be seen that they can be classified under four heads ; viz. i. Those in which no carbon atom is linked to more than two others, the normal or primary paraffins, e.g. propane. Unsaturated Hydrocarbons 51 2. Those which contain one carbon atom linked to three other carbon atoms, termed secondary or iso-paraffins, e.g. tri-methyl-methane or iso-butane. 3. There are hydrocarbons which contain a carbon atom linked to four others, and it has been proposed to term these tertiary or nee-paraffins, e.g. tetra-methyl-methane, or neo- pentane. 4. When hydrocarbons include two carbon atoms each of which is linked to three others, these ^may be termed meso- paraffins, e.g. tetra-methyl-ethane, or meso-hexane. This nomenclature has not, however, been generally adopted except for normal and iso-paraffins ; but preference has been given to that method which describes a hydrocarbon as being derived from a simpler one by the introduction of some well- known radicle into it. Thus all the normal paraffins can be named as methyl derivatives of the preceding member of the series; and the isomeric paraffins can be similarly treated (see the Pentanes and Hexanes mentioned above). It will be evident that this method has the advantage of indicating clearly the constitution of the hydrocarbon. CHAPTER IX. UNSATURATED HYDROCARBONS. BESIDES the paraffins, which are saturated compounds, there are other series of hydrocarbons which are unsaturated, i.e. the number of hydrogen atoms in each member of the series falls short of that which is possible if the carbon atoms are combined to their fullest extent. Only those unsaturated compounds, which differ from the corresponding paraffins by an even number of hydrogen atoms, can exist in the free state. Thus amongst the fatty compounds there are, besides the paraffins, C n H 2M+2 , the following unsaturated homologous series : The Olefine or Ethylene series, general formula C n H 2rt ; the Acetylene or Ethinene series, general formula C n H 2n _ 2 ; and besides there are others corresponding to C n H 2n _ 4 and C /t H 2n _ 6 , but the above-mentioned are the principal families. 52 Unsatur cited Hydrocarbons Nomenclature of Hydrocarbons. Hofmann proposed to distinguish the different families of the hydrocarbons by their terminology. The first series to have names ending in -ane, the second in -ene, the third in -ine, and so on ; e.g. C 2 H 6 is ethane, C 2 H 4 is ethene, and C 2 H 2 is ethine. Although this nomenclature possesses certain advantages, it has not been generally adopted ; and it is proposed to follow in this work the method adopted in Watts' " Dictionary " (new edit.), and to give names ending in -ene to all unsaturated hydro- carbons, while distinguishing each series by the use of a significant letter before such ending. Thus the names of the hydrocarbons C n H 2rt end in -ylene ; C H H 2H _ 2 in -inene, and so forth. Unsaturated combinations of hydrogen and carbon, the valency of which is an odd number, cannot exist free, and are given names derived from those of the hydrocarbons and end- ing in the syllable -yl ; e.g. methane yields methyl, ethane ethyl, etc. OLEFINES OR ALKYLENES, C H Ho w . Ethylene, C 2 H 4 Hexylene, C 6 H 12 Propylene, C 3 H 6 Heptylene, C 7 H 14 Butylene, C 4 H 8 Octylene, C 8 H 16 , etc. Amylene, C 5 H 10 It might have been expected that this series of hydro- carbons, isologous x with those of the methane series, would have included methylene, CH 2 , corresponding to methane in the same way that ethylene does to ethane; but hitherto all attempts to prepare it have utterly failed. Thus when di- iodo-methane is treated with sodium, or methyl chloride with potash, ethylene, and not methylene, is produced. CHo;i 2 > ( XT . T T P.TT . : T > + 2Na 2 =|| + 4Nal v^rlo : 1 9 j /~y H, ; e.g. C 2 H 6 and C 2 H 4 are isologous, Ethylene 53 and ' KOH = 2KC1 + 2 HS Ethylene or Ethene, CH 2 =CH 2 , defiant gas. Since methylene, CH 2 , cannot exist, this is the first of the defines to be considered. It occurs in coal gas, of which it is an important illuminating constituent, and is a product of the dry distillation of many organic bodies. (*i) It is produced when ordinary alcohol, C 2 H 5 OH, is heated with concentrated H 2 SO 4 to about 165; water is elimi- nated and ethylene is evolved. The reaction probably occurs in two stages (i.) C 2 H 5 OH + H 2 S0 4 = C 2 H 5 SO 4 H + H 2 O Ethyl hydrogen sulphate (ii.) C 2 H 5 S0 4 H = C 2 H 4 + H 2 S0 4 t Process. Mix 25 grams of absolute alcohol with 1 50 grams cone. H 2 SO 4 , place in 2-3 litre flask (Fig. 25), and heat upon a FIG. 25. sand-bath till the gas is rapidly evolved, which takes place at about 165. Then run in slowly a mixture of 2 parts H 2 SO 4 and I part alcohol. Wash the gas first with cone. H 2 SO 4 and then with NaOH, and collect over water. The addition of sand to the mixture, or of a thin layer of paraffin oil, tends to prevent frothing. (*2) Another important method of producing ethylene is by 54 Unsaturated Hydrocarbons FIG. 26. heating ethyl iodide, C 2 H 5 I, with alcoholic potash, when KI is withdrawn and ethylene evolved C 2 H 5 I + KOH = C 2 H 4 + KI + HoO Process. The apparatus shown in Fig. 26 may be employed. It consists of a small flask provided with a drop funnel and reflux condenser, which latter is in turn connected with another flask fitted with a reflux condenser and an exit tube. Alcoholic pot- ash is placed in both flasks and boiled, while C 2 H 5 I is dropped in from the funnel. The con- densers prevent loss of alcohol, and the second flask ensures the complete decomposition of the iodide. (*3) It may be also conveniently prepared from ethylene bromide, C 2 H 4 Br 2 , by reduction with zinc ; (*4) by the electrolysis of sodium .suc- cinate C 2 H 4 (COONa) 2 + H 2 = C 2 H 4 + CO 2 + Na 2 CO 3 + H 2 and (5) notably by the direct combination of acetylene, C 2 H 2 , with hydrogen. Properties. Ethylene is a colourless gas with a faint, peculiar odour, condensible to a liquid, b.p. 103, and can be frozen to a solid, m.p. 169. It is very slightly soluble in water, more so in alcohol and ether; readily inflammable, and burns with a luminous flame. It forms an explosive mixture with air or oxygen, and when brought into contact with ozonised oxygen spontaneously explodes. A mixture of ethylene and chlorine burns, when ignited, with a smoky flame, forming HC1 and free carbon. Ethylene in alcoholic solution readily combines with C1 2 , Br 2 or L C 2 H 4 -f C1 2 = C 2 H 4 C1 2 Ethylene dichloride Ethylene 5 5 It also unites with HI and HBr, but not with HCl C 2 H 4 + HI = C 2 H 5 I ; and an aqueous solution of HOC1 forms ethylene chlorhydrin CH 2 =: CH 2 -f HOC1 = CH 2 C1.CH 2 OH It dissolves in strong H 2 SO 4 to form ethyl hydrogen sulphate, C 2 H SO 4 H, and in presence of platinum black unites with hydrogen to form ethane. Ethylene is oxidised by HNO 3 to glycol, and by other oxidising agents to glycol, and oxalic and formic acids. Experiment 12. Prepare ethylene by the first method, note its inflammability, its explosive power when mixed with 3 volumes of oxygen, and the oily compound produced on mixing it with its own volume of chlorine. Constitution of Ethylene. Ethylene can only have one of three formulae, viz. I I CH 3 .CH=, CH 2 .CH 2 , and CH 2 =CH 2 (i.) (ii.) (iii.) The first two of these three are rendered very improbable by the failure of all experiments hitherto to produce hydro- carbon radicles of any sort possessing free valencies ; e.g. neither CH 3 , C 2 H 5 , nor CH 2 have ever been obtained in the free condition, but reactions expected to yield them always give C 2 H 8 , C 4 H 10 , and C 2 H 4 respectively. It is more in accordance, too, with the tetravalent behaviour of carbon that the tl bonds " should be saturated, if not by other elements, by carbon itself. There is, however, more positive evidence which can be adduced in favour of a symmetrical formula for ethylene, as opposed to that first given. Its formation from methylene iodide or methyl chloride is most readily explicable on the assumption that =CH 2 is freed and unites to form ethylene, H 2 C = CH 2 ; and its production from succinic acid by electrolysis also supports the same conclusion. Besides this, ethylene combines with chlorine to form a compound C 2 H 4 C1 2 ; now, the formula of ethane, CH 3 CH 3 , 56 Unsaturated Hydrocarbons would lead us to expect two possible compounds of that general formula, viz. CH 3 .CHC1 2 and CH 2 C1.CH 2 C1. It will be shown later (p. 73) that that which is formed by the addition of chlorine to ethylene has probably the second of these formulae ; and its formation is most easily understood on the assumption that a reaction such as the following occurs : - Cl CHo C1CH 2 I + II I Cl CH 2 C1CH 2 or that the ethylene molecule is symmetrical. GENERAL REMARKS ON THE OLEFINES. Ethylene has furnished us with several methods which are of general value in the formation of defines. Thus they are obtained 1. By the abstraction of the elements of water from alcohols. The use of cone. H 2 SO 4 for this purpose has been illustrated and explained. Frequently ZnCl 2 or P 2 O 5 may be advantageously employed, and in some cases the higher alcohols yield olefines by mere application of heat. 2. By elimination of HC1, HBr, or HI from haloid paraffins by heating with alcoholic KOH. In some cases the vapour must be passed over heated CaO or PbO, and in others simple distillation of the chlor-parafnn suffices to yield them. 3. By electrolysis of the alkaline salts of acids of the succinic series. 4. By the action of metals upon di-haloid paraffins, e.g. upon C 2 H 4 C1 2 . 5. Besides the above-named methods, olefines are produced in the destructive distillation of many organic substances. Properties. In physical properties the olefines closely resemble the paraffins. At the ordinary temperature the lower members of the series are gaseous, up to hexadecylene they are liquid, and above that they are solid. They burn with luminous flames, which become more smoky as the molecular weight of the hydrocarbons increases. Their specific gravities lie between about 0-63 and 0-80; their boiling points General Remarks on the Olefines 57 are very near to those of the corresponding paraffins, but their melting points are much lower than theirs. In chemical properties the olefines differ from the paraffins in a striking manner, on account of being unsaturated com- pounds. Many of their reactions have already been illustrated in studying ethylene. They unite directly with the halogens, the halogen acids, and with hypochlorous acid to form re- spectively di-haloid and mono-haloid hydrocarbons and the so-called " chlorhydrins," although all do not combine with equal readiness. Olefines are more or less readily absorbed by strong H 2 SO 4 , with the formation of acid sulphates. These salts, when boiled with water, become hydrolysed, 1 and yield the acid and an alcohol CH 3 .CH(SO 4 H).CH 3 +H 2 O = CH 3 .CH(OH).CH 3 + H 2 SO 4 Iso-propyl hydrogen sulphate Iso-propyl alcohol It may be noted that in most cases when these acids combine with the olefines, the acid radicle attaches itself to the least hydrogenised carbon atom, of which general law the combination of propylene with sulphuric acid is an example. The oxidation products of olefines differ with the oxidising agents employed, rupture of the double bond usually occurring. The olefines readily polymerise in presence of strong H 2 SO 4 , ZnCl 2 , BF 3 , etc., i.e. form polymers, which are substances of the same percentage composition, but different molecular weight. Ethylene is an exception to this rule. Propylene, CH 3 .CH:CH 2 , propene, methyl-ethylene.T\\\$ gas occurs in coal-gas, and is a frequent product of the decomposition of organic bodies by heat ; thus it is produced when the vapour of amyl alcohol is passed through a red-hot tube. Propylene may be produced in a pure state either (i) from iso-propyl alcohol, CH 3 .CH(OH).CH 3 , or (2) from the propyl iodides. Also it is formed (3) when allyl iodide, C 3 H 5 I, is reduced by pure zinc in alcoholic solution. Properties. Propylene is a gas with a garlic-like odour ; it is liquefiable by pressure to a liquid. It is moderately soluble 1 " Hydrolysis " is a term used to express the taking up of the elements of water by ethers or esters with resolution into two molecules of an alcohol, or into a molecule of an alcohol and an acid. The latter case is very frequently distinguished as " saponification. " 58 Unsaturated Hydrocarbons in alcohol, and readily in H 2 SO 4 , forming iso-propyl hydrogen sulphate. It combines readily with the halogens and the halogen hydrides, and easily undergoes polymerisation. Butylenes, C 4 H 8 . There are three isomeric hydrocarbons of this formula. All are known, and all occur in the oils from compressed coal-gas. They are : (i) Normal or a-butylene, CH 3 .CH 2 .CH:CH 2 , obtained from n-butyl iodide, CH 8 .CH 2 .- CH 2 .CH 2 I, by KOH, is a gas condensible to a liquid, b.p. -4; (2) $ or /3-butylene, CH^CHiCRCHg, obtained by the action of KOH on secondary butyl iodide, CH 3 .CH 2 .CHI.CH 3 , is a gas which forms a liquid, b.p. i, sp. gr. 0*635 ; and (3) Iso-butylene, (CH 3 ) 2 :C:CH 2 , which can be obtained from tertiary butyl iodide, (CH 3 ) 3 CI, is an unpleasant-smelling gas, which yields a liquid, b.p. 6, sp.gr. 0-637 at ^. From its solution in H 2 SO 4 ! tertiary butyl alcohol is formed on boiling with water. Of the amylenes or pentylenes, C 5 H 10 , five isomeric forms might be expected, and five are known. Two of these are found in quantity along with a trace of a third in " Iso-amylene," or commercial amylene, which is obtained when ZnCl 2 is distilled with iso-amyl alcohol (p. 101 ). The distillate boils at 25-40, and contains 90 per cent, tri- methyl-ethylene, 10 per cent, methyl- ethyl-ethylene, and a trace of iso-propyl-ethylene. The amylenes are the following: (i) a-amylene or n-pentylene, CH 3 .CFT 2 .CH 2 .CH:CH 2 , has not been obtained pure; it is a liquid, b.p. about 40; (2) iso-amylene or iso-pentylene, (CH 3 ) 2 :CH.CH:CH 2 , found in commercial amylene in small quantity, is a fragrant liquid, b.p. 21-1; (3) yS-amylene, CH 3 .CH:CH.CH 2 .CH 3 , found in commercial amylene, and also formed from a-amyl iodide, is a liquid, b -P- 36; (4) y-amylene, CH 3 .CH 2 ,C.(CH 3 ):CH 2 , found in Alsatian petroleum, and obtained from active amyl iodide, is a liquid, b.p. 32 ; while (5) tri-methyl-ethylene, (CH 3 ) 2 :C:CH.CH 3 , forms 90 per cent, of commercial amylene. It is a liquid, b.p. 36, and polymerised by ZnCl 2 or H 2 SO 4 to di-amylene. Unsatur cited Hydrocarbons 59 CHAPTER X. UNSA TURA TED HYDROCARBONS Continued. HYDROCARBONS OF THE ACETYLENE SERIES, C n H 2n _ 2 . Acetylene, ethine, or ethinene, C 2 H 2 Allylene or propinene, C 3 H 4 Crotonylene or butinene, C 4 H 6 Valerylene or pentinene, C 5 H 8 , etc. The first member of this series does not permit, according to our present ideas on the linkage of atoms, of more than one constitutional formula, but two modifications are possible in the case of allylene, and the isomers increase in number as the series ascends. The hydrocarbons of this group may be classed under three heads : 1. Those which contain two carbon atoms linked together by three bonds. Of these acetylene, HC=CH, is the simplest instance ; and there are producible from this two varieties of derivatives : (i.) those which are unsymmetrical and corre- spond to the type R'CE=CH, e.g. allylene, CH 3 .CiCH, and which are "true acetylenes," because they contain the group O=CH ; and (ii.) the symmetrical derivatives, of which R'Cr^CR' is the general formula, e.g. crotonylene, CH 3 .C!C.CH 3 . 2. There are hydrocarbons which contain a tetravalent triad of carbon atoms, one of which is united to each of the other two atoms by two bonds, =C=C=C= ; of this class allene, H 2 C=C=CHo, is the first example. 3. There are, finally, hydrocarbons that may be termed di-ethylenic, and contain two groups, =C=C=, of which di- allyl, H 2 C=CH.CH 2 .CH 2 .HC=CH 2 , is an illustration. Acetylene, CH-CH, ethine or ethinene, is found in coal gas. It is formed (i) By the direct union of hydrogen and carbon when a powerful electric current is passed from carbon poles through an atmosphere of hydrogen, as in Fig. 27. The hydrogen passes in at H, and the stream of gases is 60 Unsaturated Hydrocarbons passed over an ammoniacal solution of cuprous chloride l contained in the flask, where red copper acetylide is formed Cu 2 Cl 2 .2NH 3 + H 2 O + C 2 H 2 = 2 NH 4 C1 + C 2 Cu 2 H 2 O A little sand at the bottom of the globe prevents it being cracked by pieces of red-hot charcoal from the poles. (*2) Acetylene is also readily prepared by the action of alcoholic potash upon di-brom-ethane or brom-ethylene. In the latter case CH 2 :CHBr + KOH = CHiCH + KBr +H 2 O This is quite similar in principle to the preparation of an olefine from a bromo- or iodo-paraffin (see Ethylene, p. 54). Process. Employ the apparatus shown in Fig. 26, p. 54 (for small FIG. 27. FIG. 28. quantities the simpler arrangement shown in Fig. 28), and collect the gas over water ; or form from it the red copper compound. (*3) It is yielded by the electrolysis of sodium fumarate or maleate CH : COOH CH || = HI + 2 C0 2 + H 2 CHiCOOH CH This, again, is analogous to the formation of ethylene from succinic acid (g.v.)-, while (4) it can be produced from chloro- form, bromoform, or iodoform by decomposing them with such metals as copper, silver, or zinc 1 Cuprous chloride is best prepared by dissolving CuO in cold HC1, pouring the solution on copper turnings, and, when it is decolourised, almost neutralising it by well-cooled strong ammonia, and finally making alkaline with it. Acetylene 61 CHC1 3 CH -f 3 Cu= HI + 3 CuCl 2 CHC1 3 CH Chloroform a reaction analogous to the production of ethylene from CH 2 I 2 (p. 52), or of ethane from CH 3 I (p. 43). 5. Acetylene is formed in considerable quantities during the incomplete combustion of coal-gas, as, for example, when a Bunsen burner burns only at the bottom. Process. Allow a Bunsen burner to burn back, and draw the products of incom- plete combustion by means of an aspirator through am- moniacal cuprous chloride (Fig. 29). The red copper compound is formed, and, after washing, the acetylene may be liberated from it by means of HC1. Finally (6), the gas is readily prepared, and in a remarkably pure condition, by the action of barium or of calcium carbide x upon water. BaC 2 + 2H 2 O = C 2 H 2 + Ba(OH) 2 Properties. Acetylene is a colourless gas with a very dis- agreeable and characteristic odour ; it is poisonous, burns with a smoky flame, and is condensible to a mobile refractive liquid whose sp. gr. is 0*451 at - Q0 . In presence of platinum black, it unites with hydrogen to form successively ethylene and ethane (see Ethylene, p. 55). It forms a very explosive mixture with 2% volumes of oxygen. When an induction spark is passed through it, it is decomposed with separation of carbon ; this is remarkable, seeing that it is formed by the union of its elements under the influence of the electric arc. If, however, 1 Prepared by igniting barium carbonate, magnesium, and carbon together BaCO C . = BaC 2 62 UnsaturaUd Hydrocarbons the sparks are passed through a mixture of nitrogen and acetylene, hydrocyanic acid, HCN, is formed. Acetylene can also be resolved into its elements by exploding a percussion cap in it ; and it readily polymerises on passing through heated tubes, with the formation of benzene, C 6 H 6 , styrene, C 8 H 8 , and other hydrocarbons. Being unsaturated, acetylene unites with the halogens and with the haloid hydrides, to form substituted olefmes or paraffins according to the stage to which the reaction proceeds; ethylidene derivatives being ultimately produced by union with the haloid acids (see pp. 71, 72). C 2 H 2 -}- Br 2 C 2 FI 2 Br 2 C 2 H 2 + Br 4 = C 2 H 2 Br 4 C 2 H 2 + HBr = CH 2 :CHBr C 2 H 2 + 2 HBr = CH s .CHBr 2 It is absorbed by concentrated sulphuric acid, forming an acid sulphate, which, when decomposed by water, yields aldehyde. Chromic acid oxidises it to acetic acid. One or both atoms of hydrogen in acetylene can be replaced by such metals as Na, K, Ag, and Cu, with the formation of highly unstable and explosive metallic derivatives ; of these the silver salt is white, and the copper salt red. GENERAL REMARKS ON THE ACETYLENES. The following methods, which are general in their appli- cation to the hydrocarbons of the Acetylene series, have been illustrated in the case of acetylene : 1. Acetylenes are formed when di-haloid paraffins or mono- haloid defines are treated with alcoholic potash. 2. They are formed when unsaturated dibasic acids of the fumaric series (p. 241) undergo electrolysis. Besides these syn- thetical processes, they often result along with other hydro- carbons as the product of the dry distillation of organic substances. The student should again specially note the analogy of the two methods given to those which are employed in preparing defines. Properties. Since the hydrocarbons possess four unsatu- rated affinities, they can combine with either one or two General Remarks on the Acetylenes 63 molecules of a halogen, or of a haloid acid. In the first case, ethylenic substitution products are formed in the second, true fatty compounds. They can also combine with hydrogen to form defines or paraffins. Those which have been termed " true acetylenes " possess one very characteristic property. The triple linkage of the carbon atoms renders the hydrogen atoms very negative or acid in their character, so that in the case of acetylene two hydrogen atoms, and in substituted acetylenes of the type R'C^CH one hydrogen atom, are replaceable by metals. Thus the true acetylenes form precipitates in ammoniacal silver nitrate or cuprous chloride solutions, the precipitate which is formed being decomposed by acids, with liberation of the hydrocarbons. They also give precipitates with HgCl 2 , which, when treated with acids, yield derivatives of aldehydes or ketones. They are slowly absorbed by concentrated sulphuric acid, and the compounds formed on distillation with water yield aldehydes or ketones (difference from olefines). Several of the acetylenes also undergo polymerisation by heat or other agent with great facility, forming aromatic hydrocarbons. Very many of these properties have already received ample illustration in the case of acetylene itself. Of the higher hydrocarbons mention may be made of allylene, allene, and crotonylene. Allylene, CH 3 .C:CH, propinene, methyl-acetylene, is formed from (i) propylene bromide, CH 3 .CHBr J CH 2 Br, and chloro- or bromo-propylene, CH 3 .CH:CHBr; and (2) citra- conic or mesaconic acids, C 3 H 4 (COOH) 2 ,. by the methods indicated above. It is a colourless gas with a disagreeable odour, burns with a smoky flame, and is similar to acetylene in its properties, forming metallic derivatives, in which, how- ever, only one hydrogen atom is replaceable by a metal. Its solution in sulphuric acid when distilled with water yields tri- methyl benzene, C 9 H 12 . Allene, H 2 C:C:CH 2 , iso-allylene, isomeric with the last body, is formed in the electrolysis of potassium itaconate and from the di-chlor-propylene, CHCl:CH.CH a Cl. It is a gas 64 Halogen Derivatives of the Paraffins which smells like allylene, and does not give a precipitate with ammoniacal silver or copper solutions. Crotonylene, CH 3 .C:C.CH 3 , butitiene, di -methyl -di- acetylene, from butylene bromide, is a liquid with a pungent odour, b.p. 1 8. Shaken with H 2 SO 4 diluted with % part of water, it polymerises to solid hexamethyl-benzene, Ci 2 H 18 . The syntheses of benzene derivatives from acetylenes are specially noteworthy. CHAPTER XL HALOGEN SUBSTITUTION DERIVATIVES OF THE PARAFFINS. BY substitution derivatives are meant compounds formed by replacing an element, or group of elements, in a compound, by some other element or radicle. The halogen derivatives of the paraffins may be prepared as a rule by one or other of the following reactions : i. By the direct action of halogens upon hydrocarbons. Many compounds containing chlorine can be so prepared, a molecule of hydrochloric acid being formed for every atom of chlorine introduced. Thus CH 4 4- C1 2 - CH 3 C1 4- HC1 C 2 H 6 4- C1 2 - C 2 H 5 C1 4- HC1 This action is not so simple as it appears, since in the prepara- tion of the lower substitution products a mixture of mono- and poly-haloid compounds always results. Thus if equal volumes of chlorine and methane act on each other, as in the equation given, other chlorinated bodies are formed besides mono-chlor- methane, and a certain amount of unchanged methane remains. In the case of higher hydrocarbons, this further action may be partially avoided by allowing the vapour only to react with the halogen ; then, since the chloro-derivative boils at a higher temperature than the hydrocarbon, it condenses as it forms, and is thus removed from the sphere of action. The action Formation of Haloid Paraffins 65 of chlorine upon hydrocarbons is very much accelerated by the action of light, and also by the presence (in liquid hydro- carbons) of a little iodine dissolved in them. This latter action depends upon the preliminary formation of IC1 3 . Amongst other substances which act as chlorine-carriers may be mentioned SbCl 5 and FeCl 3 . As light aids the action of chlorine, so heat assists that of bromine, but iodine substitutes with more difficulty than either chlorine or bromine ; for when it acts alone, the hydriodic acid which is produced at the same time reacts upon the iodo-derivative, and once more produces the hydrocarbon. If, however, HgO or HIO 3 is used along with the iodine, it will react upon the HI formed, and thus prevent its reducing action. Their action may be re- presented HgO + 2 HI = HgI 2 + H 2 2. Another very important method for producing these com- pounds depends upon the action of the haloid acids, or haloid phosphorus compounds, upon the corresponding alcohols; e.g. C 2 H 5 OH + HC1 = C 2 H 5 C1 -f HOH Ethyl alcohol Ethyl chloride CH 3 OH + PC1 5 = CH 3 C1 + POC1 3 + HC1 Methyl alcohol Methyl chloride 3 CH 3 OH + POC1 3 = 3CH 3 C1 + PO(OH) 3 3 CH 3 OH + PC1 3 - 3CH 3 C1 + P(OH) 3 In the first case the reaction is never complete; it de- pends in part upon the relative masses of the two reacting substances, in part upon the temperature at "which they react. It is analogous to the formation of metallic salts from hydroxides (compare " Constitution of Alcohols," pp. 83, 96), and is an example of " esterification," which is more fully discussed in dealing with the formation of ethereal salts, or "esters" (p. 119). Of the three haloid acids, HI acts with the most readiness, The phosphorus haloid compounds are the most generally useful, but the phosphoric and phosphorous acids formed in F 66 Halogen Derivatives of the Paraffins the last two reactions react with the alcohols to form salts, so that there is always considerable loss of alcohol. To prepare the bromides and iodides it is customary to use phosphorus and bromine, and phosphorus and iodine respectively, instead of the ready-prepared phosphorus com- pounds, e.g. 3 CH 3 OH + P + Br 3 = 3 CH 3 Br + P(OH) 3 5 CH 3 OH + P + I 5 = 5CH 3 I + PO(OH) 3 + H 2 O In studying these compounds the chlorine derivatives will be taken first, then the bromine, and finally the iodine compounds, grouped as shown below : Chlorine derivatives. Bromine derivatives. Iodine derivatives. (Methyl chloride, CH 3 Cl (Ethyl C 2 H 5 C1 Methyl bromide, CH 3 Br Ethyl C 2 H 5 Br Methyl iodide, CH 3 I Ethyl C 2 H 5 I (Methylene chloride, CH 2 C1 2 < Ethylene \ r ~, Uthylidene || JC 2 H 4 C1 2 Methylene bromide, CH 2 Br 2 Ethylene n ' Ir- tr TJ - Ethylidene )C 2 H 4 Br 2 Methylene iodide,CH 2 I 2 Ethylene . \r w T Ethylidene } C ^^ Chloroform, CHC1 3 Bromoform, CHBr 3 Iodoform,CHI 3 Carbon tetra-chloride, CC1 4 Carbon tetra-bromide, CBr 4 Carbon tetra-iodide, CI 4 This grouping enables compounds of like type to be taken together, and the student should carefully compare not only those connected together in the vertical column, but also those which occur in the same horizontal line. GROUP I. MONO-HALOGEN DERIVATIVES. Methyl Chloride, CH 3 C1, chlor-methane. r Tte forma- tion of methyl chloride (i) from CH 4 and C1 2 , and (2) from methyl alcohol and HC1, have been mentioned already (pp. 64, 65). Process. The latter reaction may be carried out either (i.) by heating methyl alcohol (i part) with salt (2 parts) and sulphuric acid (3 parts); or (ii.) by passing gaseous HC1 into a boiling mixture of i part fused ZnCl 2 and 2 parts CH 3 OH contained in a flask provided with a reversed condenser, which method yields it in a pure state. Methyl Chloride, Ethyl Chloride 67 (3) It is produced on a large scale by neutralising the tri- methylamine, obtained in the distillation of beet-root " vinasse," with hydrochloric acid, and distilling the salt at 260. 3N(CH 3 ) 3 HC1 = 2 CH,C1 -f 2N(CH 8 ), -f CH 3 NH 2 + HC1 Tri-methylamine Methyl Tri-methylamine Methylamine hydrochloride chloride Properties. It is a colourless gas with ethereal odour, burns with a green-edged flame, is condensible by pressure to a liquid, b.p. -237, sp. gr. 0-991 at 22^ f is little soluble in water, more so in alcohol, forms a crystalline hydrate with water at 7*3, and its neutral solution gives no precipitate with AgNO 3 , thus differing in a marked manner from its analogue KC1. It yields methyl alcohol when heated under pressure with water or dilute KOH CH 3 C1 4- H 2 = CH 3 OH + HC1 It is used in a compressed condition for producing intense cold, and also in the manufacture of artificial colouring matters. Ethyl Chloride, CH 3 .CH 2 C1, chlor-ethane.IKvs. sub- stance can be formed quite similarly to methyl chloride, (i) by direct chlorination of ethane, (2) by the action of PC1 5 upon ethyl alcohol, and (3) by the action of HC1 .upon the alcohol alone or, most conveniently, in presence of ZnCL (see reactions above, p. 65). \Process. Dissolve 150 grams ZnCl 2 in 300 grams 95 per cent, alcohol ; boil the mixture in a flask provided with an inverted condenser and delivery tube (arranged for example as in Fig. 39), and pass gaseous HC1 through it. The gaseous product is then washed through KOH solution and either dissolved in alcohol, or else condensed by cold to a liquid and sealed up in tubes. It can also be prepared by distilling together 5 parts alcohol, 2 parts H 2 SO 4 , and 12 parts NaCl. Properties. Below 12*5 ethyl chloride is a colourless, mobile liquid, with an ethereal odour and a burning taste, sp. gr. 0-923 at fo. It burns with a green-edged flame, is little soluble in water, but readily in alcohol. It gives no precipitate with AgNO 3 in the cold ; on heating however, in aqueous or alcoholic solution, a precipitate of AgCl is obtained. It yields 68 Halogen Derivatives of the Paraffins alcohol when heated with water, or dilute KOH, underpressure ; and when heated with soda-lime, marsh gas and hydrogen are obtained. Methyl Bromide, CH 3 Br, bromo-methane. It has been already pointed out that the bromine derivatives are readily prepared by acting upon the corresponding alcohol with phosphorus and bromine ; and methyl bromide is formed thus from methyl alcohol. Process. Heat a well-cooled mixture of 6 parts methyl alcohol, I part phosphorus, with 6 parts of bromine ; wash the evolved gas through KOH, and condense it in a vessel surrounded by a freezing mixture. Properties. Methyl bromide is thus obtained as a colour- FlG. less mobile liquid, somewhat resembling chloroform, b.p. 4-5, sp. gr. 173 at , which burns difficultly with a greenish-brown flame. Ethyl Bromide, CH 3 .CH 2 Br, brom-ethane, is formed by the action of phosphorus and bromine upon ethyl alcohol 3 C 2 H 5 OH + P + Br 3 = 3 C 2 H 5 Br + H 3 PO 3 ^Process. Mix together in a |-litre distilling flask connected with condenser and receiver (Fig. 30), 13-3 grams of red phosphorus, and 80 grams of absolute alcohol. Add to this slowly from the Methyl Iodide, Ethyl Iodide 69 dropping-funnel 80 grams of bromine, cooling if necessary. Allow to stand two or three hours, and then distil from the water-bath. Wash the distillate in a separating funnel, first with weak NaOH, then three times with water. Dehydrate over CaCl 2 or K 2 CO 3 and distil, collecting that apart which boils between 36 and 40. This can be further rectified if required, by redistillation. Properties. Ethyl bromide is a colourless liquid similar to the chloride in taste and smell. Its b.p. is 38-4, and sp. gr. at ^a is i '41 89. It burns with a green smokeless flame with evolution of bromine, and is employed as an anaesthetic. Methyl Iodide, CH 3 I, iodo-methane, is most readily formed by the action of phosphorus and iodine upon methyl alcohol. The following quantities may be used : 35 parts CH 3 OH, 100 parts I, and 10 parts red P. (for working details see Ethyl iodide). Properties. Methyl iodide is a colourless, mobile, re- fractive liquid, which turns brown on exposure to light from the liberation of iodine, b.p. 42-3, sp. gr. 2^2529 at ffl. It has an ethereal odour, is difficultly combustible, and unites with water in the cold to form a hydrate, 2CH 3 I.H.>O. Ethyl Iodide, CH 3 .CH 2 I, iodo-ethane, is formed by the action of hydriodic acid, or of phosphorus and iodine upon the alcohol, most readily by the latter method 5 G 2 H 5 OH + P + 5l = 5C 2 H 5 I + H 3 ?0 4 + H 2 O ^Process. Mix 10 grams of red phosphorus and 50 grams of absolute alcohol in a tubulated retort of 500 c.c. capacity, which is connected with a condenser and receiver. Next introduce little by little 100 grams of iodine, and allow the mixture to stand twenty- four hours. Then distil, and free the distillate, from I by shaking with dilute NaOH ; wash with water, dry over CaCl 2 , and rectify by distillation. Both the P and the C 2 H 5 OH are in excess of the quantities calculated from the equation ; the former hastens the reaction, while part of the alcohol forms ethyl phosphate. Properties. Ethyl iodide is a colourless refractive liquid, b.p. 72-4, sp. gr. 1*9433 at {, which rapidly turns brown on exposure to light, owing to liberation of iodine, butane being also formed. It has a pleasant smell, is little soluble in water, readily in alcohol and ether, difficultly inflammable. 70 Halogen Derivatives of the Paraffins The bromides and iodides are chemically similar to methyl and ethyl chlorides, e.g. in their reactions with water. Propyl Compounds. These derivatives can exist in two forms according as the hydrogen atom displaced was attached to the end or central carbon atom of propane ; i.e. they possess the general formula, CH 3 .CH 2 .CH 2 X or CH 3 .CHX.CH 3 . The first is the normal propyl derivative, the second the iso- propyl compound. They can all be prepared by general methods, and are liquids insoluble in, and heavier than, water. Isopropyl Iodide should be noted, as it is usually pre- pared from glycerin (which is a trihydric alcohol, p. 243) by distilling it with phosphorus and iodine, or with amorphous phosphorus and hydriodic acid in excess. The reaction is noteworthy as illustrating the manner in which hydriodic acid acts on the polyhydric alcohols, by replacing all the hydroxyl groups by hydrogen and iodine C 3 H 5 (OH) 3 + SHI = CHs,CHI.CH 3 + 3 H 2 O + 2!, Iso-propyl iodide It takes place in two stages (i.) C 3 H 5 (OH) 3 + 3 HI = C 3 H 6 I + 3 H 2 + I 2 Allyl iodide (ii.) CH 2 :CH.CHJ + 2 HI = CH 3 .CHI.CH 3 + I s GROUP II. Dl-HALOGEN DERIVATIVES OF THE PARAFFINS. Methylene Chloride, CH 2 C1 2 , di-chlor-methane, methene chloride, can be prepared (i) by the action of chlorine on methyl chloride in sunlight; and (2) by the reduction of chloroform CHC1 3 + H 2 = CH 2 C1 2 + HC1 It is a colourless, oily liquid, with an odour like chloroform, b.p. 41*6, sp. gr. 1-37 at o. Di-chlor-ethanes, C 2 H 4 C1 2 , Di-brom-ethanes, C 2 H 4 Br 2 , and Di-iodo-ethanes, C 2 H 4 L>. Of these there are two possible isomers, according as both the halogen atoms are attached to the same carbon atom, or one is attached to each of them. Ethylene Chloride, CH 2 C1.CH 2 C1, ethene chloride, is the symmetrical form. This substance, originally known as Dutch Ethylidene Chloride, Ethylene Chloride 71 liquid, is readily formed (i) by the direct union of ethylene and moist chlorine, by passing ethylene into a slightly heated mixture of 2 parts MnO 2 , 3 parts NaCl, 5 parts H 2 SO 4 , and 4 parts H 2 O; and (2) by the action of HC1 or PC1 5 upon the di-hydric alcohol, glycol, CH 2 OH.CH 2 OH. Properties. Ethylene chloride is a colourless, thin oily liquid, b.p. 837 (cor.), sp. gr. 1*2808 at . It has a sweetish odour and taste, is insoluble in water, soluble in alcohol and ether, and dissolves phosphorus. It burns with a green flame. It is said to be a useful anaesthetic in operations on the eye. Ethylidene Chloride, CH 3 .CHC1 2 , ethidene chloride, the unsymmetrical derivative, is formed (i) by the direct action of chlorine upon ethyl chloride either in daylight or in presence of red-hot charcoal; (2) by heating aldehyde with PC1 5 CH 3 .CHO + PC1 5 = CH3.CHCL, + POC1 3 but is best obtained (3) by fractional distillation of the by- products of chloral manufacture, in which it occurs along with ethylene chloride. Properties. Ethylidene chloride is a colourless liquid, b.p. 60*1, sp. gr. 1*2039 at . It resembles chloroform in taste and smell, and finds some employment as an anaesthetic. It is a very stable compound, being attacked only difficultly by KOH, and may be distilled unchanged over potassium. Ethylene Bromide, CH 2 Br.CH 2 Br, ethene bromide, tne symmetrical compound, can be obtained (i) by the action of bromine on ethyl bromide, but (2) is most readily and usually prepared by passing ethylene into bromine C 2 H 4 + Br 2 = C 2 H 4 Br 2 \Process. Pass ethylene (preparation, p. 53) through the wash- bottles (Fig. 31), which contain strong H 2 SO 4 and NaOH respec- tively, by which it is freed from ether, CO 2 and SO 2 . The second pair of Woulffe's bottles each contain 50 c.c. of bromine covered with water, and the gas is passed through till it is decolourised. The flask contains soda, which absorbs any bromine that escapes. When the reaction is finished, shake the product with NaOH, wash with water, dry over CaCl 2 , and rectify by distillation. The corks used in the bromine bottles must be well soaked in paraffin wax before use. 72 Halogen Derivatives of the Paraffins Properties. Ethylene bromide is a colourless oily liquid with a pleasant smell, b.p. 131*5 (cor.), sp. gr. 2-189 at if; it freezes to a crystalline mass, m.p. 9-2. It is insoluble in water, but dissolves in alcohol and ether. On boiling with alcoholic potash, it forms vinyl bromide, C 2 H 3 Br, and acetylene ; with aqueous potash, vinyl bromide ; and with Na 2 CO 3 , glycol, Ethylidene Bromide, CH 3 .CHBr 2 , ethidene bromide, the unsymmetrical di-brom ethane, is formed by brominating ethyl bromide in sunlight, and by the action of PCl 3 Br 2 upon FIG. 31. aldehyde in the cold. It is a liquid, b.p. 113, sp. gr. 2^1029 at ?. Ethylene Iodide, CHJ.CH 2 I, is formed by direct com- bination of iodine and ethylene by passing ethylene into a paste of iodine and alcohol. It forms colourless needles, m.p. 8 2, which when heated in air are decomposed into C 2 H 4 and I 2 , but may be sublimed unchanged in an atmosphere of hydrogen or ethylene. It has an aromatic smell, and is insoluble in water, but soluble in ether and alcohol. Ethylidene Iodide, CH 3 .CHI 2 , is formed by the action of A1I 3 or CaI 2 upon ethylidene chloride. This may be specially noted as an instance of iodine replacing chlorine. It is a liquid, b.p. about 178, sp. gr. 2*84 at "'. Tri- halogen Derivatives 73 CONSTITUTION OF THE ETHYLENE AND ETHYLIDENE COMPOUNDS. The constitution of these bodies has been so far assumed, but the reasons which lead to the formulae assigned may now be discussed. With regard to ethylene chloride, it is natural to assume, from its mode of formation, that it is a symmetrical body, i.e. if it is granted that ethylene possesses the formula assigned to it, H 2 C=CH 2 (see p. 55), we should expect it to form, when C1 2 is added to it, the compound C1H 2 C CH 2 C1. and riot H 3 C CHC1 2 , since the former formula necessitates less internal alteration of the molecule. But, apart from this reasoning, the fact that a chloride with other properties is actually produced by replacing the oxygen in acetaldehyde, CH 3 .CHO, in which there is every evidence that the oxygen atom is only bound to one carbon atom, leads to the second formula, CH 3 .CHC1 2 , for ethylidene chloride; and as, according to our present knowledge, there are only two possible dichlor-ethanes, ethylene chloride must, by elimination of the last named, possess the formula CH 2 C1.CH 2 C1. A precisely similar argument, of course, applies to the bromo- and iodo- derivatives. GROUP III. TRI-HALOGEN DERIVATIVES. Chloroform, CHC1 3 , trichlor-methane. This important substitution derivative of methane was discovered in 1831 by Liebig and by Soubeiran, by the first and second methods of formation, (i) By the action of alkalis upon tri-chlor-aldehyde (chloral, p. 131), sodium formate being also formed CC1 3 .CHO + NaOH = CHC1 3 + H.CO 2 Na a process which is still employed when exceptionally pure chloroform is required. (2) It is formed when calcium hypo- chlorite acts upon dilute alcohol. The explanation of this reaction, which is employed on a large scale, is somewhat involved, but probably chloral is first formed, which is decom- posed in turn by the alkali liberated from the bleaching powder, yielding chloroform (see Chloral, p. 131) 74 Halogen Derivatives of the Paraffins 8CaOG 2 A- 2C 2 H 5 OH = 2CHC1 3 + (HCO,)Ca + Calcium formate + 2Ca(OH) 2 + 2 H 2 Manufacture. The following is a sketch of its production by this method. A mixture of 3 parts 85 per cent, alcohol, diluted with 60 parts of water, is placed in an iron generating still provided with a stirrer and connected with a suitable condenser ; 12 parts of bleaching powder, containing 35 per cent, available chlorine, are next added, and steam-heat is applied to raise the temperature to 40 (it must not rise above 60). The distillate thus obtained consists of chloroform, water, and alcohol ; it is collected and washed from alcohol, and afterwards rectified by a further distillation. Chloroform can also be obtained (3) from methane or methyl chloride, by the action of chlorine in sunlight ; and finally, (4) considerable quantities are now prepared by running acetone into a thin cream of bleaching powder and water 2 (CH 3 ) 2 CO + 6CaOCl 2 = 2 CHC1 3 + 2Ca(OH) 2 + 3 CaCl 2 + (CH 3 .COO) 2 Ca Calcium acetate The proportions for this process, which gives an excellent yield, are 58 parts of acetone, and 166 parts of bleaching powder containing 35 per cent, available chlorine. ^Process. Add 60 c.c. of acetone, little by little, with constant cooling, to a cream of 300 grams bleaching powder and 300 c.c. of water. Then distil off the chloroform by heating on a water-bath. The distillate consists of two layers, the lower of which is impure chloroform. Wash it once or twice with water, then dry over calcium chloride, and distil. Purification. For surgical purposes the chloroform obtained both from alcohol and acetone requires purification. It is first washed with water to remove traces of alcohol, then allowed to stand over strong H 2 SO 4 (free from nitrous compounds) to char organic impurities, next freed from acid by Na 2 CO 3 or lime-water, then dried over CaCl 2 , and finally distilled at a temperature not exceeding 64. Properties. Chloroform is a colourless liquid, b.p. 61*4, sp. gr. i -5 at ^fo, and can be frozen to a solid, m.p. - 70 It has a faint but characteristic smell and a sweet taste ; is only slightly soluble in water, but mixes in all proportions with Chloroform, Bromoform 75 alcohol and ether. It burns, when mixed with alcohol and boiled, with a very smoky green-edged flame. Chloroform is a powerful solvent, readily dissolving resins, fats, caoutchouc, alkaloids, sulphur, phosphorus, iodine, etc. It is antiseptic, and possesses a powerful anaesthetic action, which was discovered by Sir J. Simpson, of Edinburgh, in 1848, since which time it has been very largely used. In excess it is poisonous, hence care is needed in its administration. Warmed with alcoholic KOH, it yields potassium formate and chloride CHC1 3 + 4KOH - 3KC1 + HCOOK + 2H 2 O Detection of Impurities. Perfectly pure chloroform should not react either with litmus paper or AgNO 3 (absence of HC1 and free Cl) ; neither strong H 2 S0 4 nor KOH should turn it brown (absence of hydrocarbons and aldehyde). Alcohol is frequently present in small quantity, i per cent., to prevent the decomposition of the chloroform; its presence may be detected by the iodoform test (see p. 86). Identification. Chloroform undergoes many important re- actions, which serve for its detection. Thus when a solution containing it is heated with alcoholic potash and one drop of aniline, the very disgusting odour of phenyl isocyanide is pro- duced (the isonitrile test). This is a very delicate test ; i part in 5000 can be detected by it. If chloroform is added to a solution of o- or -napthol in KOH and warmed, an intense blue colour is obtained; addition of alcohol aids, water destroys it. An alcoholic solution of resorcinol, to which KOH and then chloro- form is added, gives a beautiful red liquid on warming ; dilution turns it violet. When chloroform is heated with Fehling's solution, it reduces it with precipitation of Cu 2 O". Bromoform, CHBr 3 , tri-brom-methane, is found in crude bromine, and is formed (i) by decomposing bromal with alkalis, or (2) by acting with bromine and potash on alcohol or acetone. It is a liquid similar in appearance and smell to chloroform, b.p. 151, sp. gr. 2-9045 at fj& and freezes to a solid, m.p. 8, but does not yield a formate on decomposition with KOH (distinction from CHC1 3 ). Iodoform, CHI 3 , tri-iodo-methane } is usually prepared by 76 Halogen Derivatives of the Paraffins the action of iodine upon alcohol, although acetone and other substances may be used CH 3 .CH 2 OH + 4 I 2 + 6KOH = CHI 3 + H.COOK + 5KI Ethyl alcohol Potassium formate + 5H 2 \Process. Mix 20 grams of alcohol with 40 grams of Na 2 CO 3> - ioH 2 O, and 200 grams of water, and heat in a flask to 60-80, add gradually 20 grams of iodine, and filter off the iodoform which separates. Heat the filtrate to 80, add 40 grams more soda, and pass in chlorine until no further separation of iodoform occurs. Collect the iodoform, wash thoroughly with water, and dry between filter paper. A new method now employed on a large scale depends upon the careful addition of a slight excess of dilute sodium hypochlorite to 50 parts KI, 6 parts acetone, and 2 parts NaOH, dissolved in 1-2 litres of water. The iodoform which separates is purified in the ordinary manner: Properties. Iodoform crystallises in characteristic six-sided, yellow tables, sp. gr. 2, which smell like saffron. It melts at 1 1 9, and sublimes on heating, with partial decomposition, iodine and HI being formed ; it is, however, volatile in a current of steam. It is insoluble in water, but soluble in ether, alcohol, and carbon disulphide. Its solution in alcohol or CS 2 (espe- cially CS 2 ) is very sensitive to light ; iodine is liberated, and methylene iodide produced. Boiling aqueous KOH decom- poses iodoform with formation of potassium formate, alcoholic KOH forms methylene iodide. If mixed with finely divided moist silver acetylene is evolved. It is an anaesthetic, with special action on the muscles. Identification. A solution of phenol and solid KOH, gently warmed with an alcoholic solution of iodoform, gives a red substance soluble in alcohol with a carmine red colour. Its reactions with napthol and resorcinol are similar to those of chloroform (p. 75). GROUP IV. TETRA-HALOGEN DERIVATIVES. Carbon tetra-ehloride, CC1 4 , tetra-chlor-methane, is formed (i) by the action of chlorine on methane in sunlight; but most readily (2) by passing chlorine into boiling chloroform contain- ing a little iodine in solution ; or (3) by passing chlorine and carbon bisulphide vapours through a red-hot tube, decomposing Remarks on the Halogen Derivatives 77 the sulphur chloride formed simultaneously by potash, and rectifying. It is a thin colourless liquid, with aromatic smell, b.p. 767, sp. gr. i '63 at -Jl It is insoluble in water, soluble in alcohol and ether; it is decomposed by alcoholic KOH, thus : CC1 4 + 4KOH - CO 2 + 2H 2 O + 4KC1 (compare chloroform). Carbon tetra bromide, CBr 4 , tetra - bromo - methane, occurs in crude bromine, and can be prepared by acting on CHBr 3 , CHI 3 , or CS 2 , with bromine in presence of iodine. It is a white crystalline solid, m.p. 91, b.p. 189-5, S P- r - 3'4 2 > has a camphor-like smell, and very readily sublimes. Carbon tetra-iodide, CI 4 , tetra-iodo-methane, is obtained by heating CC1 4 with A1I 3 or CaI 2 . It is a red solid, crystallises in octahedra, sp. gr. 4*32 at 15L, and slowly decomposes in air. GENERAL REMARKS ON THE HALOGEN DERIVATIVES. Two general methods of production have been already mentioned on pp. 64, 65. It may be noted that they are also notably formed (i) by addition of halogen hydrides to olefines ; (2) by addition of a molecule of a halogen to an olefine ; and (3) sometimes by the action of PC1 5 on bodies containing a CO group, e.g. CH 3 .CHO. Properties. The haloid derivatives of the paraffins are very little soluble in water, but dissolve readily in all pro- portions in alcohol and ether, and also in acetic acid. The liquids are generally colourless and possess an ethereal smell, and are stable with the exception of the iodine compounds, which redden when exposed to light, owing to the liberation of iodine. The chlorine derivatives boil at a lower temperature than the bromine compounds, and those than the iodine derivatives, and the primary derivatives possess a higher boiling point than the secondary. They burn with a green-edged flame, and their inflammability decreases with increase of the amount of halogen. It is important to remember that AgNO 3 cannot be employed as a reagent for the detection of the halogens, although under certain circumstances the halogen derivatives do react with it. The halogens can be displaced by moist ;8 Alcohols silver oxide with introduction of hydroxyl (see Alcohols). Many of the haloid paraffins also yield alcohols when treated under pressure with water or a dilute solution of KOH ; but, on the other hand, alcoholic potash splits off a molecule of the halogen hydride and forms olefines (see p. 56). Nascent hydrogen from sodium amalgam and dilute alcohol, and from Zn and HC1, reduces the halogen compound to the corresponding hydrocarbon, e.g. CHC1 3 + 3 H 2 = CH 4 + 3HC1 Ammonia acts on the monohaloid derivatives, forming amines (p. 163). CHAPTER XII. ALCOHOLS. THE general term " alcohol " is given to a class of bodies composed of carbon, hydrogen, and oxygen, which are derived from hydrocarbons by the replacement of one or more atoms of hydrogen by an equal number of hydroxyl (OH') groups ; thus from ethane are derived ethyl alcohol, C 2 H 5 OH, and glycol, C 2 H 4 (OH) 2 . They are termed mono-, di-, or polyhydric alcohols, according to the number of OH groups which they contain. The name was originally applied solely to spirits of wine, and is supposed to be a corruption of the term vinum alcalisa- tum to vinum alcoholisatum, whence alcohol vini. The alcohols are substances which bear a certain re- semblance to the metallic hydroxides. Thus the OH is re- placeable by acid radicles; for example, just as KOH yields KC1, KHSO 4 , KC 2 H 3 O 2 , so methyl alcohol, CH 3 OH, yields CH 3 C1, CH 3 HSO 4 , and CH 3 C 2 H 3 O2. The number of hydrogen atoms replaceable by hydroxyl in a hydrocarbon is, however, practically limited by the number of carbon atoms in the molecule, since, except under special circumstances, compounds containing more than one hydroxyl group to each atom of carbon cannot be obtained ; e.g. glycerin, Isomerism of Alcohols 79 C 3 H 5 (OH) 3 , the first stable alcohol which contains three hydroxyl groups, also contains three carbon atoms. Isomerism of Alcohols. The two first paraffins, methane and ethane, each yield only one mono-hydric alcohol ; propane, butane, and the higher paraffins can yield isomeric forms, the isomerism of which is due to two different causes : (i.) that produced by the position in the hydrocarbon of the replaced hydrogen atom ; and (ii.) that owing to the isomerism of the hydrocarbon itself. Thus in methane and ethane the hydrogen atoms are pre- sumably of the same relative value, and only one alcohol is obtainable in each case, viz. H.CH 2 OH, and CH 3 .CH 2 OH; but (a) () propane, CH3.CH 2 .CH 3 , can yield two alcohols, viz. (i.) CH 3 .CH 2 .CH 2 OH and (ii.) CH 3 .CH(OH).CH 3 , according as the OH group is attached to the carbon atom (b) or (a), because the carbon atoms (a) and (b) occupy relatively different positions in the molecule. Similarly, the two butanes, CH 3 .CH 2 .CH 2 .CH 3 and (CH 3 ) 2 CH.CH 3 can each yield two isomers according to the carbon atom to which the OH is linked. Thus the first yields (i.) CH 3 .CH 2 .CH 2 .CH 2 OH and (ii.) CH 3 .CH 2 .CH(OH).CH 3 ; and the second (iii.) (CH 3 ) 2 CH.CH 2 OH and (iv.) (CH 3 ) 3 COH. It will be seen that the alcohols derived from methane and ethane, one of those from propane (i.), and two of those from butane (i. and iii.) contain the group CH 2 OH, which is characteristic of primary alcohols. The second one derived from propane and the second from butane contain the divalent group =CHOH, that is distinctive of secondary alcohols ; while the fourth alcohol derived from butane contains the trivalent group =COH, and is a tertiary alcohol. All alcohols (from whatever hydrocarbon they are derived) comprise one or other of the above-named groups ; so that there may be normal-primary, and iso-primary alcohols derived from isomeric hydrocarbons. Thus the alcohols yielded by the butanes may be named (i.) normal primary butyl alcohol ; (ii.) secondary butyl alcohol; (iii.) iso-primary butyl alcohol; and (iv.) tertiary butyl alcohol, respectively. So Alcohols Nomenclature of Alcohols. Kolbe proposed that, for the sake of simplicity, the simplest alcohol, CH 3 OH or H.CH 2 OH, should be called carbinol, and that all others should be looked upon as derived from it, and designated accordingly ; thus ethyl alcohol would become methyl carbinol, the propyl alcohols would be termed ethyl and di-methyl carbinol respectively, and so forth. This proposal has not, however, received universal acceptance, and the alcohols are more generally named according to the hydrocarbon radicles which they contain, the word " alcohol " being employed as the generic termination. MONOHYDRIC ALCOHOLS OF THE C M H 2n+] OH SERIES. Methyl alcohol, CH 3 OH Butyl alcohols, C 4 H 9 OH Ethyl alcohol, C 2 H 3 OH Pentyl alcohols, C 5 H n OH Propyl alcohols, C 3 H 7 OH Hexyl alcohols, C 6 H 13 OH, etc. The alcohols derived from the hydrocarbons of the methane series by replacing one hydrogen atom by hydroxyl, i.e. the saturated monohydric alcohols, must naturally receive earliest consideration, and of these that derived from methane is the simplest. Methyl Alcohol, CH 3 OH or H.CH 2 OH, methyl hydrate, carbinol, wood spirit, wood naphtha. (1) The chief source of methyl alcohol is the watery distillate obtained in the destructive distillation of wood ; indeed, it was in that substance that Boyle first discovered it. Manufacture. The above-mentioned liquid, which contains besides the alcohol, acetone, acetic acid, and other substances, is separated by settling and filtration from suspended tarry matters, and then distilled in copper stills heated by steam. The first tenth of the distillate is then distilled off caustic lime, again distilled after the addition of a little sulphuric acid, and finally rectified over quicklime. Each ton of wood distilled yields from i to 3 gallons of wood spirit. (2) Considerable quantities of the alcohol are also obtained from the spent wash or "vinasse" left when alcohol is pre- pared from beet-root molasses. Methyl Alcohol 81 Mamtfacture. The "vinasse" is evaporated to dryness, the residue calcined, and the vapours condensed. The liquid so obtained contains tri-methylamine, ammoniacal salts, methyl cyanide, and methyl alcohol. It is neutralised with H 2 SO 4 , and again distilled. The distillate contains the cyanide and the alcohol, and is freed from the former by distillation over lime. The weak alcohol which is so obtained is concentrated by means of quicklime. Ordinary wood spirit varies very much in strength, the amount of alcohol in it varying from 45 to 95 per cent. Preparation of the Pure Alcohol. In order to prepare the pure alcohol, the acetone present in crude wood spirit may be partially removed by fractional distillation ; or the crude spirit is saturated with calcium chloride, the acetone dis- tilled off, and the alcohol separated from the calcium chloride by adding water and then distilling. The still impure methyl alcohol thus obtained is dehydrated by lime, heated to the boiling point, anhydrous oxalic acid dissolved in it, and then allowed to cool. Crystals of di-methyl oxalate separate out, and are washed with water till the washings no longer give the iodoform reaction (see p. 86) showing the absence of acetone ; they are then boiled with water or dilute soda, and the alcohol distilled off. It may then be dehydrated by means of lime or baryta. (3) Almost pure alcohol may be obtained by saponifying oil of winter-green with potash and distilling off the alcohol. And (4) it is also formed synthetically by heating methyl chloride with KOH for some days to ioo- CH 3 C1 + KOH = CH 3 OH 4-KC1 or (5) by heating it to 200 with potassium acetate and acetic acid, and saponifying the product with KOH. (i.) CH 3 C1 + HC 2 H 3 O 2 - CH 3 C 2 H 3 O 2 + HC1 (ii.) CH 3 C 2 H 3 O 2 + KOH = CH 3 OH + KC 2 H 3 O 2 Properties. -Pure methyl alcohol is a colourless, limpid liquid, b.p. 65-8-66 (cor.), sp. gr. |f:, 07972. It has a pure spirituous odour, and burns with a pale blue flame. It mixes G 82 Alcohols with water in all proportions, heat being evolved and contrac- tion taking place, this latter being greatest when the propor- tions present are i mol. CH 4 O : 3 mols. H 2 O. It mixes with water, alcohol, and ether, and possesses great solvent powers, dissolving oils, fats, resins, etc., with ease, and hence is much used as a solvent. Anhydrous copper sulphate is slightly soluble in it, although the hydrated salt is not. It combines with many salts to form combinations in which it acts as " alcohol of crystallisation," e.g. CaCL.4CH 3 OH, LiC1.3CH 3 OH, and CuSO 4 .2CH 3 OH ; the first of these is employed in purifying it. On oxidation it yields formic aldehyde and formic acid, the latter being also formed when it is heated with soda-lime. When taken internally it acts as an intoxicant. Methyl alcohol finds considerable employment in the manufacture of aniline colours, for which purpose it should be free from ethyl alcohol and acetone ; it is also employed for making varnishes and as a source of heat. Identification. The following tests assist in the detection of methyl alcohol: It gives, when heated with H 2 SO 4 and sodium salicylate, the odour of oil of winter-green. "When it is oxidised by K 2 Cr 2 O 7 and H 2 SO 4 it yields formic acid, which can be distilled off, and gives a black precipitate or silver mirror with AgNO 3 solution. It gives no iodoform when warmed with KOH and iodine (difference from ethyl alcohol]. Constitution. Some of the reactions of methyl alcohol are specially interesting, because they help to elucidate its constitution, and are also typical of those undergone by the higher members of the series. It has been already pointed out (p. 78) that the monohydric alcohols bear some resem- blance to metallic hydroxides, i.e. they may be looked upon as hydroxides of organic radicles. Thus methyl alcohol is a neutral substance, and yet it possesses slight basic properties, for its hydroxyl can be replaced by halogens similarly to that, for example, of KOH. Thus- KOH -f- HC1 = KC1 + H 2 O CH 3 OH + HC1 = CH 3 C1 + H a O Methyl Alcohol, Ethyl Alcohol 83 The latter reaction is realisable, though not readily, with the acid itself; but if PC1 5 , PC1 3 , or POC1 3 are employed, it is quite easy to prepare methyl chloride (compare p. 65) ; e.g. CH 3 OH 4 PC1 5 = CH 3 C1 + POC1 3 + HC1 and similar reactions occur with the other halogen acids and compounds of phosphorus, although in the last cases it is preferable to employ the elements P and Br, or P and I to produce CH 3 Br and CH 3 I respectively (see p. 66). Methyl alcohol reacts also with other acids to form " ethereal salts," or " esters," in a quite analogous fashion to those produced by KOH. Thus KOH 4- HNO 3 = KNO 3 4 H 2 O CH 3 OH 4 HNO 3 = CH 3 NO 3 + H 2 O KOH + H 2 SO 4 = KHSO 4 + H 2 O CH 3 OH 4- H 2 SO 4 = CH 3 HSO 4 + H 2 O Methyl alcohol also dissolves potassium and sodium with the formation of the corresponding methoxides or methylates CH 3 OK and CH 3 ONa, which can be obtained from their solution in the alcohol as white solids, which are deliquescent, alkaline, and absorb CO 2 . These substances are thus analogous to the corresponding hydroxides. It will be recognised that these reactions with acids and metals lead inevitably to the conclusion that methyl alcohol contains the group OH, or that its formula is correctly H I represented as H C OH, which is methane having a H hydrogen atom replaced by hydroxyl. The second member of the Alcohol series is Ethyl Alcohol, CH 3 .CH 2 OH, spirits of wine, methyl carbinol. Amongst the very oldest manufactures of the world must be placed that of producing the various fermented liquors which serve as more or less intoxicating beverages for various nations, and the existence in these of a substance to 8 4 Alcohols which ultimately the term " alcohol " was given, was proved by the result of investigations in the art of distillation. It is by this same means, i.e. by fermentation of various saccharine solutions and distillation of the resultant product, that alcohol is prepared to-day. The manufacture of strong alcohol is described on p. 88 ; and a typical reaction is that which occurs when grape sugar undergoes fermentation C 6 H 12 6 = 2C 2 H 5 OH + 2 CO 2 This equation represents the principal reaction, which accounts for 95 per cent, of the sugar ; the remaining 5 per cent, goes to form other substances, among which are glycerin and succinic acid. Experiment 13. The validity of the above equation may be qualitatively shown thus : Fit a large flask with a perforated cork and tube, as in a, Fig. 32 ; introduce into it a solution of 40 grams of glucose in 1^-2 litres water, add a little yeast, cork the flask, and insert the tube into a bottle (b] containing clear lime- water. Keep the solution in the flask just warm (20) ; it will ferment readily, and the forma- tion of CO 2 will be shown by the production of CaCO 3 in the lime- water. When the fermentation is over, connect the flask by means of a bent tube with a con- denser, distil off about 100 c.c., and test for alcohol in it by the reactions given on p. 86. Preparation of Absolute Alcohol. Anhydrous alcohol is obtained from the above-mentioned strong spirit. This always contains some water, from which it. is freed by the use of absorbents, such as freshly ignited K 2 CO 3 , CaCl 2 , CaO, or BaO. Of these lime is generally used. ^Process. Place quicklime in a flask or other vessel and add sufficient alcohol to cover it, allow to stand for some hours at 40 and afterwards distil, rejecting the first and last portions. Repeat this process if the alcohol contained more than 5 per cent, of water. FIG. 32. Ethyl Alcohol 85 The last traces of moisture are removed either by carefully adding a small quantity of sodium to the alcohol and again distilling ; or, better, by adding to the lime during the last treatment a small quantity of fresh baryta, which, when the alcohol is anhydrous, dissolves in it with the formation of a yellow liquid, which on distillation yields absolute alcohol. Commercial absolute alcohol usually contains about 0-5 per cent, of water, from which it may be freed as described. Alcohol may be synthetically produced (*i) by dissolving ethylene in H 2 SO 4 , diluting the ethyl hydrogen sulphate formed (p. 55) with water, and then distilling it C 2 H 4 + H 2 S0 4 = C 2 H 5 HS0 4 C 2 H 5 HSO 4 + H 2 O = C 2 H 5 OH + H 2 SO 4 This is an important method, because by its means the synthesis of alcohol from inorganic materials can be accom- plished; for carbon and hydrogen unite under the influence of the electric discharge to form C 2 H 2 , this in its turn unites with nascent hydrogen to form C 2 H 4 , and the reactions given complete the synthesis. It may also be formed (2) from ethyl bromide or iodide by the action of moist Ag 2 O (which acts as AgOH), or from ethyl chloride by heating under pressure with dilute alkalis. C 2 H 5 C1 + KOH = C 2 H 5 OH + KCl Properties. Pure ethyl alcohol is a transparent, colourless, mobile liquid, b.p. 78-2-78-5; it solidifies at 130-5, and its sp. gr. is 0-795 at rP- H nas a pleasant ethereal odour and a burning taste; is inflammable, burning with a pale blue flame ; and its vapour mixed with the proper quantity of air forms an explosive mixture. It is very hygroscopic, and mixes with water in all proportions with contraction of volume and evolution of heat ; the contraction is greatest when the proportions employed are C 2 H 6 O : 3H 2 O. If, however, 2 parts of alcohol are mixed with i part of snow, a freezing mixture is produced. In a concentrated condition it acts as an inflammatory poison, and when dilute produces intoxication. It is a most useful solvent for many organic bodies, such 86 Alcohols as fats, resins, and alkaloids, and it dissolves many gases and inorganic salts. In the latter case some curious instances occur ; thus it dissolves Lid, but neither KC1 nor NaCl ; CaCl 2 , SrCl 2 , and Ca(NO 3 ) 2 are soluble, but neither BaCl 2 , Sr(NO 3 ) 2 , nor Ba(NO 3 )2. It also combines with many salts, forming compounds in which it plays the same part as water of crystallisation. Alcohol coagulates albumen, so preventing putrefaction. Oxidising agents, according to their strength, form aldehyde and acetic acid. Chlorine attacks it violently, and forms chloral alcoholate. Heated with strong sulphuric acid, it yields, according to circumstances, ether or ethylene. Like methyl alcohol it reacts with metals, forming ethoxides or ethylates, and it also forms salts in a similar fashion. Absolute alcohol gives no blue colour to anhydrous copper sulphate, produces no turbidity with benzene, and does not give a precipitate of Ba(HO) 2 if BaO dissolved in absolute alcohol is added to it It also gives a green colouration with sodium amalgam and anthraquinone, but if water is present a red colour is formed. Identification. Alcohol may be detected in an aqueous solution by adding to it a little NaOH or KOH and a slight excess of iodine ; on gently warming, six-sided star-shaped crystals of iodo- form will be produced. This reaction (Lieberfs] is so delicate that Wtfo P art f alcohol may be recognised. It must be remembered, however, that many other substances form the same compound, althotigh methyl alcohol does not yield it. When alcohol is acted upon by acetyl chloride (p. 158), or heated with a little sodium acetate and cone. H 2 SO 4 , the fragrant odour of ethyl acetate is developed. Or the liquid containing alcohol may be distilled, the distillate rectified till anhydrous, and a determination of its boiling point made. If the alcoholic liquid is boiled with a little K 2 Cr 2 O 7 solution and dilute H 2 SO 4 , the smell of aldehyde is obtained ; and if the mixture is then distilled, and the distillate warmed with KOH, a yellowish brown colour indicates the presence of alcohol. Constitution. The formula of alcohol follows from similar considerations to those adduced for that of methyl alcohol, to which substance it bears a strong chemical resemblance. It is Fermentation 87 also supported by its formation from ethyl chloride, which can be prepared direct from ethane. FERMENTATION. MANUFACTURE OF ALCOHOL. The formation of alcohol by a fermentative process is im- portant as affording the first instance of the production of organic compounds (if marsh gas is excepted) by means of living organisms. It is necessary, therefore, to say a few words on the subject of fermentation. Fermentation. Many organic substances, when exposed to the air, undergo a rapid decomposition, very frequently without any apparent cause. These decompositions have been proved to result from the action either of living organ- isms (bacteria or fungi} or of chemical ferments known as enzymes, which are the product of vital action, although them- selves unorganised. The organisms need in most cases the presence of air and also of nitrogenous matter, in order to grow and produce the changes noted. All ferments are destroyed or rendered inactive by high temperatures, at least under ordinary conditions. How the organisms act is not accurately known. It is thought by some that they themselves actually produce the transformations by their life-processes ; others think that they secrete an enzyme, which in its turn effects the change. As an example in support of the latter theory may be cited yeast, which secretes the ferment invertase that possesses the pro- perty of transforming cane sugar into dextrose and levulose. Fermentation products may be neutral, acid, or basic, and it may be noted that the bacteria and moulds form more simple products than do the known enzymes. Alcoholic fermentation is brought about by many different organisms, the principal of which is the ordinary yeast-plant, Torvula or Saccharomyces cerevisice, the ferment that is made use of by brewers and distillers for fermenting the various worts with which they are severally concerned. When viewed microscopically, it is a round or oval, some- what globular object (Fig. 33), and grows, when in a suitable 88 Alcohols medium, by budding or gemmation. These buds often adhere to the parent and themselves undergo subdivision, with the result that sometimes a string of them is formed which might be mistaken for other organisms. Manufacture of Alcohol. The first stage in the manufacture of alcohol is the preparation of the wort, a saccharine solution of not more than i '04 sp. gr. Many kinds of grain, potatoes, etc., may be used in its production, but mixtures of malt, rye, barley, oats, maize, and rice are cn i en y employed in the United Kingdom. By the term malt is usually meant barley, which has been first steeped in water till soft, then piled in heaps and allowed to germinate, and finally kiln- dried to destroy the vitality of the seed. In any case a certain proportion of malt is necessary, because, as a result of FJG the processes just described, it contains a soluble ferment called diastase, which possesses the power of transforming the starch present in the grain into a fermentable sugar. A mixture of two or more kinds of grain has been shown to give a larger yield of alcohol than one kind only. In preparing the wort, about one part of malted barley and two or three parts of ordinary grain (the grist) are taken and crushed up into a tolerably fine condition. This mixture is then extracted (" mashed ") once or twice with warm water at 6o-65, and the infusion allowed to stand for some hours, during which time the diastase converts the starch into dextrin and malt sugar (maltose). After that the cool wort is mixed at a temperature of about 23 with yeast, and the fermentation of the wort proceeds during four or five days, at the end of which time its specific gravity will be reduced to about ro, and it will be ready for distillation. By suitable distillation a spirit containing 90 per cent, by weight of alcohol can be readily obtained, from which absolute alcohol can be prepared as already described. If the ordinary form of still is employed, it requires repeated fractionation to separate the alcohol from the accompanying water; consequently many attempts have been made to separate the two liquids by a continuous operation, and many stills embodying the same principles as Wurtz's fractionating bulbs (see p. 7) have been devised. The Manufacture of Alcohol 89 one commonly used in England is known as Coffey's still, and is figured in diagrammatic form in Fig. 34. It consists of two columns, E and G, known respectively as the "analyser" and "rectifier;" and, after heating them by steam, omitting minor details, it is employed as follows : The fermented wort, or wash as it is technically termed, is pumped up from the reservoir by the pipe B, and passes down the rectifier by the pipe CC, which forms a series of zigzags between FIG. 34. each of the divisions into which the column is divided. The liquid is then discharged into the analyser E, where it meets ascending vapours, the pressure of which prevents it falling down through the perforations of the plates, and it therefore descends by the tubes F F, which discharge the overflow of liquid from one diaphragm on to that next below it. As it descends through these plates it is met by a current of steam coming in through the pipe H, which causes it to boil and volatilises the alcohol. It is thus, by the time it reaches the bottom of the column, deprived of its alcohol, and passes away as spent wash. It will be readily seen that as the go Alcohols steam and alcoholic vapour ascend through the perforated plates they are washed by the short columns of liquid on them, which condense large portions of the aqueous vapour, while the alcohol passes out by the pipe K into the rectifier. In the rectifier it again passes up through a series of perforated plates, where by condensa- tion there are quickly formed layers of liquid as in the analyser, but the cooling and washing effect is intensified by the presence of the pipes C C, which contain the cool wash. More water-vapour is con- densed there along with the feints, which consist of higher-boiling alcohols along with some alcohol forming " fusel oil," which falls to the bottom of G, and can be pumped back again into the analyser. At the upper part of the rectifier the perforated plates cease, and are replaced by shelves, by means of which the vapour is compelled to take a zigzag course. This portion is called the finished-spirit condenser, and most of the spirit condenses here and flows, by an exit-pipe not shown in the diagram, to the finished-spirit reservoir, and the vapour which passes away at L, which contains aldehyde and any uncondensed alcohol, is led into a refrigerator, in which it is condensed. The strong alcohol obtained as described may be freed from traces of fusel oil by filtration through wood charcoal and subse- quent redistillation ; the " first " and " last runnings," which contain the impurities, being collected apart. This spirit, on dilution till it contains 84 per cent, by weight of alcohol, forms the rectified spirits of wine of the British Pharmacopeia, and has a sp. gr. of 0-8382 at i-f^fo. If 100 volumes of this spirit are diluted with 60 volumes of water, they produce 156 volumes of what is known as proof spirit, the sp. gr. of which is 0*9198 at 15-6; it contains 49*24 per cent, by weight of absolute alcohol, sp. gr. 07938 at 15-6, or 57-06 per cent, by volume. The term " proof" is a survival from the time when the strength of spirit was roughly tested by moistening gunpowder with it and then igniting it. The weakest spirit which would ignite the gunpowder when the alcohol was burnt off was " proof spirit ; " while above and below that strength it was termed "over" and "under" proof respectively. Methylated Spirit. In consequence of the high duty upon rectified spirit, it is much too costly to use as a solvent for manufacturing purposes, e.g. in making varnishes, polishes, Alcoholic Beverages 91 etc. For this purpose, therefore, the Board of Inland Revenue permit the use of a mixture of i part wood spirit and 9 parts rectified spirit to be sold under the above name. Latterly, to make it still less drinkable and more difficult to purify, f per cent, of mineral naphtha, 0*8 sp. gr., has been added. This latter addition, however, renders it useless for many laboratory purposes. ALCOHOLIC BEVERAGES. Under this heading may be considered various intoxicating liquors which owe their properties to the presence of alcohol. Beer is a liquor of ancient origin, and is a product of the fermentation by yeast of malted grain, usually barley. In the manufacture of beer, the malt, after preliminary crushing, is run along with water at 70-75 C. into the mash-tun, where, when thoroughly mixed, the whole mixture should possess a tempe- rature of 60-65 C., at which heat it is allowed to stand for i|-2 hours to allow of the diastatic transformation of the starch into maltose and dextrin (see p. 276). The mash liquor, or sweet wort, is boiled in the wort boiler for i-i^ hour, after being mixed with the necessary quantity of hops. The hops serve the double purpose of imparting a bitter aromatic taste to the finished product, and also, owing to the tannin matter which they contain, of helping to clear the beer by the precipitation of albuminous matter : while boiling the wort coagulates these albuminous matters, and also destroys disease germs which may be present. From the boiler the wort is run into the hop-back, a large vessel in which it is strained from the hops as it is run to the coolers, and from them over the refrigerators to the fermenting tuns, where it should possess a temperature of 15 C. In the fermenting tuns the wort is mixed with the necessary amount of yeast, the fermentation begins at once, and the tempera- ture will perhaps become 21 C. in about 60 hours; it is not allowed to rise above this. It is allowed to proceed till the desired amount of attenuation (loss of specific gravity) is attained when the yeast is separated from the beer in various ways. The beer is then racked into casks for immediate use or for storage. A slight fermentation continues in the cask, which makes the beer stronger and less sweet, and charges it with carbonic acid gas. 92 Alcohols The strength of the beer produced varies according to the purpose for which it is required. Porter or Stout is manufactured similarly, the dark colour being due to the introduction of half-burnt or caramelised malt. Wines are liquors prepared by allowing the expressed juice of the grape, known as must, to undergo spontaneous fermentation owing to the germs present on the fruit itself. The grapes are crushed by various methods, and, if white wines are required, are separated from the residual skins, stalks, etc. (the marc], as soon as possible. The wines produced from such "must" owe their colour to the oxidation of the extractive matter of the juice. In the case of coloured wines, the marc is not separated from the must until after fermentation, when, owing to the joint action upon the alcohol and acid then produced, a certain amount of the colour- ing matter (asnolin) is extracted. The grape juice is fermented in large barrels at 10-12 C. for 12-14 days. At the end of this time the clear "young" wine is drawn off the lees, first into vessels, where it is allowed to rest, and then racked into casks, where it matures. During this last stage a second slow fermentation occurs, and as the amount of alcohol slowly increases there is deposited a crust of potassium hydrogen tartrate and calcium tartrate along with albuminous and colouring matters, which is known as argol. This acid salt of potassium is present along with several other acids in the original juice, and differs from them in being much less soluble in dilute alcohol than in water, hence its precipitation. During the maturing of the wine, either in casks or bottle, the special flavour or " bouquet " is developed ; this is due to the forma- tion of various ethereal salts, which are formed from the alcohol or alcohols present. This bouquet differs with different wines, and has been shown to be owing, at least in part, to the yeasts characteristic of the various districts. Spirits. Brandy, properly so called, is made from the spirit distilled from certain white French wines. After dilution this is stored in vats, and allowed to mature. If stored in oak vats it becomes yellow and yields pale brandy ; if coloured with caramel it forms brown brandy. As imported into this country it contains about 50 per cent, by weight of alcohol, or is 1-2 over proof. Rum is spirit obtained from molasses, and owes its flavour to ethyl butyrate. It is generally imported at 20 over proof. Whiskey is largely made from malt only, sometimes from malt and rye. Scotch whiskey is generally bonded at u over proof, and Irish whiskey at 25 over proof. Alcoholometry 93 Brandy, rum, and whiskey cannot be sold of less strength than 25 under proof. Gin, or Geneva (from the French genievre, "the juniper"), is a grain spirit mainly made from malt and rye, and specially flavoured with various aromatic substances, such as angelica root, carda- mons, juniper, liquorice powder, etc. Hollands, the Dutch spirit, is flavoured by juniper. Absinth is a form largely used in France, and flavoured with wormwood. It is generally sold by the rectifiers about 17-22 under proof. Its lowest limit of sale is 35 under proof. The following are approximately the percentage amounts by weight of alcohol in some alcoholic liquors : Lager beer 4 per cent. Madeira ... 1 6 per cent. Burton ale ... 6 Port ... 18 London porter 6 ,, Brandy ... 50 Claret ... 8 Whiskey ... 60 Sherry ... 15 ALCOHOLOMETRY. By the term " alcoholometry" is meant the art of estimating the amount of alcohol in a spirituous liquid, whatever be the method employed. The chief processes which are now used to determine the strength of an alcoholic liquid, depend upon ascertaining either the specific gravity of the liquid itself, or, since alco- holic liquors frequently hold other substances in solution, that of the liquid obtained by distilling off half to three- quarters of a given volume of the liquor, and making the distillate up to the original volume with distilled water. If alcohol and water underwent no contraction when mixed, it would then be easy (knowing the specific gravity of alcohol itself) to calculate, by means of the well-known formula, the percentage of alcohol present in the mixture. Alcohol and water do, however, undergo contraction of volume when mixed, and it has therefore been necessary to ascertain directly the specific gravity of the two liquids when mixed together in all proportions and at different temperatures. This has been done with great accuracy by Gilpin, Tralles, Gay Lussac, Fownes, and others; so that, if the specific gravity of dilute 94 Alcohols alcohol is carefully ascertained, on reference to their tables the percentage amount present can be at once ascer- tained. For excise purposes the specific gravity is deter- mined by Sikes' hydrometer, shown in Fig. 35, which is made of hard metal and gilded. The stem is graduated from o at the upper to 10 at the lower end, with intermediate graduations for every ^ of a division. It is also provided with nine other weights (numbered respectively 10 to 90), which, by means of a slit in them, can be fixed on the stem ; these increase the range of the instrument. Since in England the standard of strength is not absolute but proof spirit, this hydrometer is graduated accordingly, and can only be used in conjunction with tables. FIG. 35. CHAPTER XIII. AL CO HOLS Continued. GENERAL REMARKS ON THE MONOHYDRIC ALCOHOLS. OF the following general methods of formation, the first three have already received some illustration during the study of methyl and ethyl alcohols. 1. Alcohols can be prepared from mono-haloid hydro- carbons by the action upon them of KOH, freshly precipitated moist Ag 2 O, PbO, and even occasionally of water alone, KOH is of little service, but moist Ag 2 O, which acts as if it were AgOH, is very useful QH 5 I + AgOH = C 2 H 5 OH 4- Agl 2. A method which is frequently of great use consists in first transforming the haloid derivative into an ethereal salt (see p. 107) of acetic acid, either by heating with silver acetate, or with a mixture of potassium acetate and glacial acetic acid, and then saponifying the resulting salt with KOH Formation of Alcohols 95 CH 3 .CH 2 .CH 2 C1+ AgC 2 H 3 O 2 - CH 3 .CH 2 .CH 2 (C 2 H 3 O 2 ) + KC1 Propyl chloride . Propyl acetate CH 3 .CH 2 .CH 2 (C 2 H 3 2 )+KOH - CH t .CHCH t OH+KC t H l Q, Propyl alcohol It must of course be remembered that the purity of the alcohol obtained depends upon that of the haloid paraffin employed. It should also be noted that the iodides react more readily than the bromides, and those than the chlorides. 3. Another method of producing alcohols, which has been already illustrated, is that in which an olefine is dissolved in H 2 SO 4 , and the resulting salt boiled with water. In the case of propylene and the higher olefines, the secondary alcohols are frequently formed. 4. Since primary alcohols yield aldehydes and acids by oxidation (see p. 96), it might be expected that reduction of these substances would produce the reverse action. Actually, if aldehydes, and either the chlorides or anhydrides of the acids, are reduced, e.g. by sodium amalgam in acid solution, they give alcohols CHa.CHs.CHO + H 2 = CH 3 .CH 2 .CH 2 OH Propionic aldehyde Propyl alcohol (CH 3 .CO) 2 O + 2H 2 = CH 3 .CH 2 OH + CH 3 .COOH Acetic anhydride Ethyl alcohol Acetic acid CH 3 .COC1 + 2H 2 = CH 3 .CH 2 OH + HC1 Acetyl chloride Ketones, the first oxidation products of secondary alcohols (see p. 96), also yield alcohols when similarly treated (CH 3 ) 2 CO + H 2 = CH 3 .CH(OH).CH 3 Acetone Iso-propyl alcohol 5. When primary amines (see p. 163) are acted upon by nitrous acid alcohols are formed. This reaction is, however, only simple in the case of methylamine and ethylamine. Higher amines yield a mixture of primary and secondary alcohols CH 3 .CH 2 NH 2 + HN0 2 = CH 3 .CH 2 OH + N 2 + H 2 O 6. A special reaction for producing tertiary alcohols is given under the butyl alcohols (p. 100). Properties. The lower members of the alcohol series are 96 Alcohols colourless, limpid liquids miscible with water; the inter- mediate members are oily liquids; while the highest, such as cetylic, cerylic, and melissic alcohols, are solids. As their molecular weight increases they become less soluble in water. The boiling points of alcohols of similar structure increase about 19 C. for every addition of CH 2 to the molecule; primary alcohols boil at a higher temperature than the isomeric secondary alcohols, and these boil higher than the correspond- ing tertiary. It has been already shown that methyl and ethyl alcohols act in many cases as if they were hydroxides of organic radicles, and their behaviour in this respect with acids and metals is typical of their higher homologues. Primary, secondary, and tertiary alcohols show very characteristic differences when oxidised, and these differences serve for their diagnosis. Diagnosis of Alcohols. The three classes of alcohols may be differentiated in two different fashions : (i) by a study of their oxidation products, and (2) by the action of nitrous acid on the mtro-paraffins producible from them. The first method is tedious, because it requires as a rule the quantitative examination of the substances produced ; but it has the advantage of throwing very considerable light on the constitution of the alcohols. Shortly stated, primary alco- hols yield, on oxidation, first an aldehyde, and then an acid, both of which contain the same number of carbon atoms as the alcohol C 2 H 5 OH + O = C 2 H 4 + H 2 O Acetaldehyde C 2 H 4 + O = C 2 H 4 2 Acetic acid If the alcohol is secondary, the first result of oxidation is the formation of a ketone, which, on further action, yields an acid or acids containing less carbon atoms than the original compound. Thus : (CH 3 ) a CHQH + O = (CH 3 ) 2 CO + H 3 O Iso-propyl alcohol Acetone (CH 3 ) 2 CO + 20 2 = CH 3 .COOH + CO 2 + H 2 O Acetone Acetic acid Diagnosis of Alcohols 97 In the second reaction formic acid is first formed, but breaks up into CO 2 and H 2 O. The simplest radicle usually remains attached to the C of the CHOH group. Finally, a tertiary alcohol gives neither aldehydes nor ketones with the same number of carbon atoms, but acids or ketones containing a less number. Thus tri-methyl carbinol yields, first, formic acid and acetone, (CH 3 ) 2 CO, which latter yields acetic acid CH 3 .COOH, H 2 O, and CO 2 . The second method, due to Meyer and Locher, is more readily applied, but is not applicable to alcohols which contain more than 8 carbon atoms. Process. First transform the alcohols into the corresponding iodides by means of concentrated hydriodic acid. Then introduce equal quantities of dry silver nitrite and fine sand into a small dis- tillation flask, provided with a side tube 10 cm. long, and add a little of the alcoholic iodide. When the reaction is over, heat over a small flame and collect the distillate in a test-tube. Mix this distillate with three times its volume of a solution of KNO 2 in strong KOH solution, and shake well. Next add cautiously dilute H 2 SO 4 , and according as the resultant fluid is dark red, dark blue, or colourless, there was originally present a primary, secondary, or tertiary alcohol. This reaction depends upon the formation of nitre-paraffins by the action of AgNO 2 upon the alcoholic iodides. If the nitro-paraffin formed is a primary compound, it yields with nitrous acid a nitrolic acid (p. in), e.g. CH 3 .CH 2 (NO 2 ) gives CH 3 .CCl 2 TT, the alkaline salts of which possess a dark red colour; a secondary nitro-paraffin gives a pseudo-nitrol, e.g. (CH 3 ) 2 CH(N0 2 ) gives (CH 3 ) 2 C^^ 2 , which gives a dark blue colouration when in solution ; while a tertiary nitro-compound does not react at all. Experiment 14. Try the second method, identifying the kind of alcohol radicle present in ethyl iodide, iso-butyl iodide, and tertiary butyl iodide respectively. Propyl Alcohols, C 3 H 7 ,OH. Two isomers. n-Propyl Alcohol, CH 3 .CH,,CH 2 OH, ethyl carbinol. H 98 Alcohols After repeated failures, the presence of this alcohol has been conclusively demonstrated in fusel oil, so that it is one product of the fermentation of different sugars. It may be prepared artificially by the reduction of propionic aldehyde or propionic acid. It is now obtained in quantity by fractionally distilling the "feints" from the rectification of crude alcohol. The " feints " is a mixture of different propyl, butyl, and amyl alcohols. As it is impossible to separate perfectly the two propyl alcohols by such fractionation, they are next converted into the corresponding bromides, which are separated by dis- tillation, and re transformed into the alcohols in the ordinary manner (see p. 94). Properties. Propyl alcohol is a colourless, refractive liquid, of b.p.. 97*4, sp. gr. o'8o88 at yf C. Its odour re- sembles that of ordinary alcohol. It is miscible in all pro- portions with water, but separates out on addition of CaCl 2 or other salts, which fact distinguishes it from ethyl alcohol. When oxidised it gives the corresponding aldehyde and acid. Secondary Propyl Alcohol, (CH 3 ) 2 CHOH, iso-propyl alcohol, di-methyl carbinol, is found in the " feints " obtained in rectifying spirit. It may be prepared by the reduction of acetone, and from iso-propyl iodide, or from propylamine by general methods (pp. 94, 95). Process. It is usually prepared by heating iso-propyl iodide with lead hydroxide and water, in a flask provided with a reflux condenser. The product is distilled, and the distillate dehydrated by potash. Properties. Secondary propyl alcohol is a colourless mobile liquid, b.p. 83 (cor.), sp. gr. 0791 at yf. It has a slight alcoholic odour, is miscible with water, alcohol, and ether, and is separated from its aqueous solution by KOH. It forms several hydrates with water. On oxidation it yields acetone, and then formic and acetic acids. Constitution of the Propyl Alcohols. The constitu- tion of normal propyl alcohol follows from its formation from propionic acid and propionic aldehyde. It will be shown Butyl Alcohols 99 later (p. 194) that carboxyl acids, i.e. acids which are charac- terised by the group CO. OH may be formed by the succes- sive introduction of halogen and CN radicles in place of the OH group of an alcohol, and final saponification of the cyanogen derivative. If, then, the position in the molecule of such a COOH group is known, when it is reduced the position of the CH 2 OH is also known. Now, the COOH group in pro- pionic acid can only take one possible position in the hydro- carbon from which it is derived, viz. ethane, CH 3 .CH 3 , can only yield CH 3 .CH 2 .COOH ; hence on reduction normal propyl alcohol, CH 3 .CH 2 .CH 2 OH, is formed. The constitution of secondary propyl alcohol, CH 3 .CH- (OH).CH 3 , follows from the fact that on oxidation it yields acetone, for which the formula CH 3 .CO.CH 3 is well proved. Butyl Alcohols, C 4 H 9 OH. Of these alcohols there are four isomers, all known : two are primary alcohols, one is secondary, and one tertiary. 1. Normal Butyl Alcohol, CH 3 .CH 2 .CH 2 .CH 2 OH, propyl carbinol, is found in the heavy oils from brandy, and in the " feints " before mentioned. It is a product of the fermentation of glycerin by certain bacteria and also by a schizomycetes, and can be synthetically prepared by reduction of butyric aldehyde or butyric acid. Properties. Butyl alcohol is an oily, colourless, highly refractive liquid, b.p. 117 C. (cor.), sp. gr. 0*8233 at $. It has a peculiar odour, and its vapour excites coughing. It is moderately soluble in water, and separated from solution by CaCl. 2 . It yields butyric acid on oxidation. 2. Iso-butyl Alcohol, (CH 3 ) 2 CH.CH 2 OH, iso-propyl car* binol) fermentation butyl alcohol, is usually obtained from the feints. It is also found in combination in Roman chamomile oil, and is produced by the fermentation of sugar by the Bacillus bitty ticus. Properties. Iso-butyl alcohol is a colourless liquid which smells like fusel oil, b.p. 108, sp. gr. 0*807 at yf. 3. Secondary Butyl Alcohol, CH 3 .CH 2 .CH.OH.CH 3 , methyl-ethyl carbinol, is usually prepared from secondary butyl iodide. It was first obtained from erythrite by reduction ioo Alcohols with HI to secondary butyl iodide, from which the alcohol can be prepared by the ordinary method. Properties. It is a colourless liquid, b.p. 99 C., sp. gr. 0*827 at -; has a strong but pleasant odour and burning taste. 4. Tertiary Butyl Alcohol, (CH 3 ) 3 COH, tri-methyl carbinol, is produced by the reaction which led to the dis- covery of tertiary alcohols, namely, that of zinc methide upon acetyl chloride. The reaction is complicated, but may be represented thus (i.) CH 3 .COC1 + 2Zn(CH 3 ) 2 = (CH 3 ) 3 .COZnCH 3 + CH 3 ZnCl (ii.) (CH 3 ) 3 .COZnCH 3 -f 2 H 2 O = (CH 3 ) 3 COH+Zn(OH) 2 +CH 4 Properties. Tertiary butyl alcohol forms, when anhydrous, colourless prismatic needles, m.p. 25 C, b.p. 83 C., sp. gr. 0*7836 at \y,. When fused it is an oily liquid with a camphor- like odour. It forms a hydrate, C 4 H 10 (X.H 2 O, which boils at 80. Constitution of the Butyl Alcohols. The constitu- tions of n-butyl alcohol and iso-butyl alcohol may be deduced from their respective formation from butyric and iso-butyric acids, which are themselves formed from propyl and iso- propyl alcohols respectively, by transforming them into the corresponding cyanides (nitriles) and saponifying those. We may infer that the constitution of secondary butyl alcohol is represented by the formula CH 3 .CH 2 .CH(OH).CH 3 , from the fact that on oxidation it yields methyl-ethyl ketone ; and, finally, the formula for tertiary butyl alcohol can only be, by elimina- tion of the others, (CH 3 ) 3 COH. Amyl or Pentyl Alcohols, C 5 H n OH. According to ordinary chemical formulae, there are theoretically eight possible isomers. Two, however, of these possess an asym- metric carbon atom, i.e. a carbon atom which is attached to four different radicles. Such an atom is indicated in the formulae by thick type. Now, when a compound contains such a carbon atom, it has been found that it usually occurs in two forms, which possess different optical properties. One of the forms rotates Amy I fitiphoh 101 a ray of polarised light to the right, and the other to the left, or they are said to be dextro- and laevo-rotatory respectively. When such compounds are produced in a reaction in equal quantities, the resultant substance will be optically -inactive, and it is usually difficult to separate it into the two varieties. If more than one asymmetric carbon atom is present, the number of isomers is still further increased. Amongst examples of this phenomenon which will be met with, may be mentioned lactic, malic, and tartaric acids and the sugars. Three of the amyl alcohols are derived from pentane, four from iso-pentane, and one from tetra-methyl-me thane ; the last is unknown. (i)n-Amyl Alcohol, CH 3 .(CH 2 137 ; (2) Methyl-propyl Carbinol, b. p. 119; and (3) Di-ethyl Carbinol, (CH 3 .CH 2 ) 2 CHOH, b. p. 117; are derivatives of pentane. All three are liquids, and the first occurs in fusel oil. The second is noteworthy because it contains an asymmetric carbon atom, and although optically inactive as ordinarily prepared, if ordinary mould (Penicillium glaucum) is grown in it, an alcohol which is optically active (Isevo-r oratory) remains. The following alcohols are derived from iso-pentane : Commercial or Fermentation Amyl Alcohol, li iso- amyl alcohol? or fusel oil, is a mixture of inactive and active alcohols, and is the product of the fermentation of various saccharine materials. The alcohols may be separated by fractional crystallisation of the barium salts of the correspond- ing amyl sulphates. The crude alcohol is a colourless liquid, b.p. about 131, sp. gr. 0-810 at 3. It has a powerful and penetrating smell and a burning taste, and its vapour, when inhaled, produces coughing, giddiness, and headache. Its toxic effect is much greater than that of ordinary alcohol ; hence the evil effects which follow from drinking impure spirits. It is optically active, though in a varying degree. Inactive Amyl Alcohol, (CH 3 ) 2 CH.CH 2 .CH. 2 OH, iso-butyl carbinol) is present in Roman chamomile oil and in 102 Ethers iso-amyl alcohol. It is a liquid, b.p. 131*5 C. (cor.), sp. gr. 0-8135 at ft- It i s optically inactive. Active Amyl Alcohol, CH 3 .CH 2 .CH^^ 3 secondary C.H 2 Oti butyl-carbinol, from iso-amyl alcohol, has probably not been obtained pure ; it boils at 127-128 C., and its sp. gr. at -j-f" is 0*815. As prepared it is laevo-rotatory, but if treated in dilute solution with Penicillium glaucum, it becomes dextro-rotatory. Methyl-iso-propyl Carbinol, (CH 3 ) 2 CH.CH(OH).CH,, from the corresponding ketone, is a fragrant-smelling liquid, b.p. 113, sp. gr. 0-833 at 2. Tertiary Amyl Alcohol, JC.OH, di-methyl-ethyl C 2 H 5 carbinol) from the corresponding iodide, is a colourless liquid with camphor-like odour, sp. gr. o'8i4 at -j4, b.p. 102, which solidifies to a solid, m.p. 12. CHAPTER XIV. ETHERS. THE constitution of the ethers may be shortly expressed by saying that they bear the same relation to alcohols that oxides of monad metals do to their hydroxides. Thus K 2 O + H 2 O = 2KOH and by suitable means the reaction below can also be accom- plished (C 2 H 5 ) 2 + H 2 O = aC a H B OH Ethyl oxide Ethers are therefore the oxides of the alkyl (alcoholic) radicles, or can be considered also as anhydrides of the alcohols. Ethers can be either simple or mixed ; i.e. both the radicles attached to the oxygen atom may be identical, form- ing simple ethers, or they may be different, and then mixed ethers are formed. So, e.g., the following are simple ethers Di-methyl Ether 103 and / 3 C 2 H 5 Di-methyl ether, Di-ethyl ether, methyl ether ethyl ether while as examples of mixed ethers may be cited HpO and CHp U 2 rl 5 ^3 "7 Methyl-ethyl ether Methyl-propyl ether Besides the terms " simple " and " mixed ethers," the expres- sion compound ether is frequently used. Now, a compound ether is in reality a salt in which an organic radicle takes the place of a metal, and is so termed because, while an ether may be looked upon as derived from water in which both hydrogen atoms are replaced by alkyl radicles, in a compound ether one hydrogen atom is replaced by an alkyl group and the other by an acid radicle. Thus ethyl nitrate, C 2 H 5 NO 3 , may be written C 2 H 5 O(NO 2 ). It is now becoming customary to term compound ethers esters. The esters of inorganic acids will be considered after the ethers, and those of the organic acids after the acids concerned. ETHERS. The preparation and properties of the series will find most complete exemplification when we discuss ordinary ether, di- ethyl ether, although the di-methyl derivative will be first mentioned. Di-methyl ether, (CH 3 ). 2 O, methyl oxide, methyl ether, is formed when 20 parts of H 2 SO 4 and 13 parts of methyl alcohol are heated together to 140. The gas evolved is washed through caustic soda, and may then be passed into strong sulphuric acid, which absorbs 600 times its own volume of it to form the compound (CH 3 ) 2 O.H 2 SO 4 . This can be kept without change, and if dropped into an equal volume of water the ether is evolved, and may be dried over CaCl 2 and collected. Properties. Methyl ether is a gas that is condensible by pressure to a liquid, b.p. 24, which may be used for pro- ducing artificial cold. The gas is not very soluble in water, 104 Ethers but readily in alcohol and ether. It forms with dry HC1 the compound (CH 3 ) 2 O.HC1, which boils at 2; and it forms substitution products when acted on by chlorine. Ether or Di-Ethyl Ether, (C 2 H 3 ) 2 O, ethyl oxide, ethyl ether, "sulphuric ether" (^Ether, B.P.). (*i) Ether is usually prepared by what is termed the " continuous " process, by heating alcohol with sulphuric acid to 140. The reaction may be represented by the equation 2 C 2 H 5 OH + H 2 S0 4 = (C a H 8 ) 2 O + H 2 O + H 2 SO 4 but it really takes place in two stages. There is first formed FIG. 36. an acid sulphate of ethyl, which when boiled with alcohol yields ether and the acid (i.) C 2 H 5 OH + H 2 SO 4 = C 2 H 5 SO 4 H + H 2 O (ii.) C 2 H 5 S0 4 H + C 2 H 5 OH = (C 2 H 5 ) 2 + H 2 SO 4 f Process. Carefully mix 9 parts of strong H 2 SO 4 with 5 parts of 90 per cent, rectified spirits of wine, and bring the mixture into a flask provided with a well-fitting cork bored with 3 holes (Fig. 36). Ether 105 Through one of the holes is passed a stoppered funnel, in another is fitted a bent tube which is joined to a condenser, and through the third is passed a straight glass tube that dips into the liquid and in which a thermometer is suspended. The mixture of alcohol and acid given boils at about 140, and at that temperature ether distils over along with water and a little alcohol. As the reaction pro- ceeds alcohol is dropped in from the funnel to take the place of that which has been decomposed, and the reaction would go on continuously if the alcohol were anhydrous, and no by-reactions occurred. Actually, however, water accumulates in the flask and weakens the acid, so that less alcohol is acted on as time passes ; also a certain amount of the acid itself becomes reduced, SO 2 being evolved, so that after about 35 parts of alcohol have been used, it is best to start the operation afresh. Purify the ether by shaking with milk of lime or NaOH to free it from SO 2 , and distil from the water-bath. Pour the distillate on to fused CaCl 2 , allow it to stand for some time, and again rectify by distillation. This treatment frees it from most of the water and alcohol which is mixed with it, leaving it sufficiently pure for most purposes. Purification. If required pure, wash it repeatedly with water till free from alcohol, as shown by the iodoform test, dry first over CaCl 2 , and then over slices of sodium till no more hydrogen is evolved, and finally distil from the water-bath. Ether is also produced (*2) when ethyl iodide acts upon sodium or potassium ethylate C 2 H 5 I + C 2 H 5 ONa = (C 2 H 5 ) 2 O + Nal and also (*3) by heating dry silver oxide with ethyl iodide 2 C 2 H 5 I + Ag 2 = (C 2 H 5 ) 2 + 2 AgI The two last processes are not of great importance for its preparation, except in so far as they throw light upon the constitution of ether, and show that both its alkyl groups are directly united to the oxygen atom. Properties. Pure ether is a colourless, mobile, neutral liquid, with somewhat pleasant odour and burning taste. Its sp. gr. is 0*7201 at yf; it is exceedingly volatile; its b.p. is 34*6, and it freezes to a solid, m.p. 117. It is very inflammable, burn- ing with a luminous flame, and its vapour forms a strongly explosive mixture with air. It is slightly soluble in water, io6 Ethers readily in alcohol, and TOO parts of ether dissolve about 3 parts of water. Ether is a very useful solvent for many inorganic and organic substances, such as I, Br, S, P, fats, resins, and oils, and is largely used as an anaesthetic. It is oxidised in presence of air by platinum black, heated Pt sponge, or red-hot Pt wire, with the formation of acetic and formic acids, CO 2 , and aldehyde; HNO 3 and chromic acid also oxidise it ; and ozone acts on it very violently the explosive compound ether peroxide is said to be formed in the reaction. P 2 O 5 has no action upon ether, but P 2 S 5 forms the corresponding sulphide, (C 2 H 5 ) 2 S. Chlorine acts on it violently ; thus, if a little ether is poured into a jar of chlorine an explosion occurs ; if, however, suitable precautions are taken, substitution compounds are formed ; bromine acts much more gently, and iodine only slightly. Sodium, ammonia, and the alkalis do not affect ether. Dilute H 2 SO 4 , HC1, or PC1 3 do not act on it when cold, but if it is heated in closed tubes with very dilute H 2 SO 4 it re-forms alcohol. Concentrated HI, HC1, or PC1 5 , and H 2 SO 4 form ethyl esters when warmed with it (C 2 H S ) 2 + 2HC1 = 2C 2 H 5 C1 + H 2 O (C 2 H 5 ) 2 + PC1 5 = 2C 2 H 5 C1 + POC1 3 (C 2 H 5 ) 2 O + 2H 2 SO 4 = 2 C 2 H 5 SO J H + H 2 O If the HI is cold, a molecule each of the alcohol and the alkyl iodide is formed. Ether combines with many salts to form molecular compounds ; e.g. (C 2 H 5 )O.SnCl 4 , (C 2 H 5 )oO.SbBr 3 , and 3 (C 2 H 5 ) 2 O.HgBr 2 . GENERAL REMARKS ON ETHERS. The methods given for the production of ether are of general application. i. By abstraction of the elements of water from two molecules of an alcohol by the action of H 2 SO 4 . This method is applicable also for the production of mixed ethers ; thus if methyl alcohol is dropped into heated ethyl hydrogen sulphate, methyl-ethyl ether is formed C 2 H 5 S0 4 H + CH 3 OH = Q.H.OCH, + H 2 SO 4 Remarks on Ethers. Esters 107 2. By the action of haloid paraffins upon ethylates C 2 H 5 ONa + CH 3 I = C 2 H 5 OCH 3 + Nal 3. From dry silver oxide and alkyl iodides, The last methods serve for the formation of both simple and mixed ethers. Properties. Most of the ethers are colourless liquids, although the highest members are solids. They resemble ordinary ether in their properties, being neutral in reaction and almost insoluble in water, although readily soluble in alcohol, and boil at lower temperatures than the isomeric alcohols. The chemical reactions they undergo have been thoroughly illustrated by ethyl ether, and support the con- clusion that they are oxides of organic radicles. The mixed ethers afford us the first example of a form of isomerism termed metamerism. Thus the following ethers are metameric, i.e. are metamers : , CH 3 .CH 2 .CH,^ ' (CH 3 ) 2 CH^ ' * 3 C 2 H 5 ^ Methyl propyl ether Methyl iso-propyl ether Compounds are termed metameric when their isomerism is caused by the linkage together of different groups (which, though individually unequal, give the same sum-total of atoms) by means of a polyvalent element, in this case oxygen. CHAPTER XV. COMPOUND ETHERS, ETHEREAL SALTS, OR ESTERS, OF THE MINERAL ACIDS. WE have already had reason to define the meaning of the term "ether," and to explain that ethers proper differ from com- pound ethers in that they contain only hydrocarbon radicles attached to oxygen, while in the latter, one of the radicles is an acid residue. Perhaps the term "compound ether," or, better, an " ester," may be best defined as a salt in which alcoholic io8 Compound Ethers radicles have been substituted for the typical hydrogen of an acid. Consequently, if an acid be polybasic, we may have acid or neutral salts or esters, or, also, we can have salts which are partly metallic and partly alcoholic ; thus HNO 3 will yield C 2 H 5 NO 3 H 2 S0 4 C2 ^ 5 ^S0 4 , (C 2 H 5 ) 2 S0 4 , and CsI SO 4 and organic acids give similar results. Summing up, it may be said, in short, that if an alcohol is the hydroxide and an ether the oxide of a hydrocarbon radicle, an ester is formed by the combination of such a radicle with an acid. It is convenient to study here those formed with inorganic acids ; those derived from organic acids will be studied as occasion serves. ESTERS OF NITROUS ACID. The usual formula assigned to nitrous acid is HONO, in which the hydrogen atom is united to nitrogen by means of oxygen; there is no reason, however, why there should not be an acid isomeric with it which might be represented by the formula H.NO 2 , in which the hydrogen is directly united to the nitrogen atom, and actually there is a well-known class of organic compounds which appear to be derived from such an acid. The derivatives of the first acid are termed esters of nitrous acid, while those of the second are generally called nitre-compounds ; and the two classes are sharply differen- tiated from each other by their different stability and action towards reducing agents and dilute alkalis. Methyl Nitrite, CH 3 ONO, formed by the action of HNO 3 and copper upon methyl alcohol, is an agreeable- smelling gas condensible to a liquid, b.p. 12. Ethyl Nitrite, C 2 H 5 ONO,is formed (*i) by the action of HNO 3 on alcohol ; the reaction is violent, part of the acid is reduced by part of the alcohol, and the N 2 O 3 thus formed esterifies the remainder 2C 2 H 5 OH + N 2 3 = 2C 2 H 5 N0 2 + H 2 O Ethyl Nitrite 109 Obtained in this manner it always contains aldehyde ; this can be avoided (2) by passing N 2 O 3 into alcohol, or (3) by acting with dilute H 2 SO 4 and NaNO 2 upon alcohol. ^Process. Dissolve 34^5 grams NaNO 2 in 120 c.c. H 2 O, and cool below o. Add 13*5 grams H 2 SO 4 to a mixture of 32 c.c. rectified spirit and 32 c.c. H 2 O, then cool and dilute to 120 c.c. Slowly add this acid mixture, by means of a drop-funnel, to the solution of NaNO 2 . Separate the ethyl nitrite formed, wash with ice-cold water, and dry over ignited K 2 CO 3 . Properties. Ethyl nitrite is a colourless, limpid liquid with a refreshing ethereal odour, b.p. 18, sp. gr. 0*9 at . It is slightly soluble in water, readily in alcohol. If pure it is stable, but impure or wet it readily decomposes with libera- tion of NO ; glycerin added to its alcoholic solution prevents this decomposition. Reducing agents liberate NO, and alkalis saponify it CoH 6 NO 2 + NaOH = QH 5 OH + NaNO 2 This decomposition of ethyl nitrite is a characteristic example of the manner in which all compound ethers or esters break up on heating with water or dilute alkalis or acids, and is termed " saponification," though perhaps the better term would be " hydrolysis ; J> it is the reverse of the process of forming esters from an acid and an alcohol. The term " saponification " was originally applied to the decomposition of fats by alkalis (see Soaps, p. 153). Spiritus JEtheris Nitrosi is an impure form of ethyl nitrite used in medicine. Formerly it was prepared by acting upon HNO 3 with an excess of alcohol, and contained little nitrous ether, and was called " sweet spirit of nitre." It is made now for pharmaceutical purposes as follows : gradually add 2 fluid ozs. of H 2 S0 4 to a pint of rectified spirit ; then carefully add i\ ozs. of HNO 3 , and pour the acid mixture into a retort which contains 2 ozs. of No. 25 copper wire. Fit the retort with a thermometer, attach to it a condenser, and distil the contents at from 76 to 79 (the temperature must not exceed 82), until 12 ozs. have passed over. Cool the contents of the retort, add \ oz. more HNO 3 , and distil off 2 ozs. more. Dilute this distillate with about 2 pints of spirit, so that it will yield not more than seven, or less than five, no Compound Ethers times its own volume of NO, measured at 15-5 and 760 mm., when decomposed by FeSO 4 and H 2 SO 4 according to the following reaction : 2C 2 H 5 NO 2 + 2FeSO 4 + H 2 SO 4 = 2C 2 H 5 OH + Fe 2 (SO 4 ) 3 + 2NO This volume of gas corresponds to 2-3 per cent, of the nitrite. This official solution should have a specific gravity of about 0^840 to 0*845, an d should not effervesce, or only slightly so, when shaken with NaHCO 3 . Amyl Nitrite, C 5 H U NO 2 , is obtained as a yellowish liquid, b.p. 99, sp. gr. 0-9, by acting upon iso-amyl alcohol with KNO 2 and dilute H 2 SO 4 . In a somewhat impure form it finds considerable use in medicine as amyl nitris, B.P., which is prepared from amyl alcohol, boiling at 132, by distilling it carefully with an equal volume of HNO 3 in a large retort. The distillate is collected up to 100, washed with aqueous potash, separated, and then slowly distilled ; that portion which comes over between 96 and 100 is collected as amyl nitrite. It possesses a disagreeable, stupefying odour, and its vapour when inhaled causes dilation of the blood-vessels, and consequent rush of blood to the head and flushing. It has found use in angina pectoris, asthma, etc. If of good quality, about 70 per cent should distil over between 90 and 1 00. Nitre-methane, CtLjNO* produced by acting upon silver nitrite with methyl iodide, is a mobile liquid, b.p. 101. Nitro-ethane, CH 3 .CH 2 NOo, is produced (*i) along with some ethyl nitrite by heating ethyl iodide with AgNO 2 C 2 H 5 I + AgN0 2 = C 2 H 5 N0 2 + Agl (*2) It is also formed by distilling ethyl hydrogen sulphate with NaNO 2 , the yield being, however, small C 2 H 5 SO 4 H + NaNO a = C 2 H 5 NO 2 + NaHSO 4 These methods are the first examples of two processes generally useful in preparing esters. Properties. Nitro-ethane is a colourless, refractive oil with a pleasant ethereal smell, b.p. 114, sp. gr. 1*0561 at YJ. It is reduced by nascent hydrogen to ethylamine, Nitro-ethane. Esters of Nitric Acid ill C 2 H 5 NH 2 ; heated with HC1, sp. gr. 1-14, it forms hydroxyl- amine and acetic acid. Nitro-ethane is slightly acid in its properties, so that alcoholic soda forms the Na salt, CH 3 .CHNaNO., If it is mixed with KOH and KNO 2 , and H 2 SO 4 then slowly added, ethyl nitrolic acid, is produced, of which the alkaline salts are red (see p. 97). Constitution. There appears little doubt that nitro- paraffins possess the constitution already assigned to them (p. 1 08). The fact that nitro-ethane yields on reduction the compound C 2 H 5 NH 2 , for which there is abundant evidence that the nitrogen atom is linked to carbon, supports the idea that in other nitro-compounds nitrogen is also so combined. It also resists saponification another argument in favour of such a fact, since all esters, in which the alkyl radicles are apparently linked to the carbon atom by means of oxygen, are readily decomposed. The following more complex "nitro-compounds" should be noted. Nitroform, CH(NO 2 ) 3 , tri-nitro-methane, is a colourless thick oil, forming white crystals below 15. It explodes when heated, and acts as a strong acid, the H of the CH group having an acid character due to the influence of the nitro groups. Nitre-chloroform or Chloropicrin, C(NO 2 )C1 3 , tri- chlor-nitro-metham, is obtained by distilling alcohol with a mixture of NaCl, KNO 33 and H 2 SO4, or most readily by acting upon picric acid with bleaching powder. p It is a colourless liquid, b.p. 112, sp. gr. 1*69 at f. It has a pungent odour, and explodes when rapidly heated. ESTERS OF NITRIC ACID. Methyl Nitrate, CH 3 ONO 2 , may be prepared by dis- tilling methyl alcohol with nitric acid, best in the presence of urea nitrate (see Ethyl Nitrate). It is a colourless liquid with an ethereal odour, slightly soluble in water, b.p. 65, sp. gr. 1*2167 at |fo. When ignited it burns with a yellow H2 Compound Ethers flame; it explodes on being struck, and its vapour, when heated to 150, explodes with tremendous violence. Ethyl Nitrate, C 2 H 5 ONO 2 , is formed by the action of HNO 3 on ethyl alcohol in the presence of some substance which prevents the reduction of the acid and consequent formation of ethyl nitrite. Urea answers this purpose well, any nitrous acid which may be formed being decomposed at once, according to the reaction CO(NH 2 ) 2 + 2 HN0 2 = 3 H 2 + CO, + 2 N 2 The reaction between the alcohol and acid is QH 5 OH -f HN0 3 = C 2 H 5 ONO 2 + H 2 O This is a typical example of a general reaction for the forma- tion of esters. The reaction is, however, never complete unless the water is removed from the sphere of action by some means, because it weakens the acid and also decomposes the ester, till a stage is arrived at when the decomposition and combination are equal. Process. It may be prepared as follows: Warm 80 grams HNO 3 , sp. gr. i '4, with urea nitrate ; cool, and add to this 60 grams alcohol, sp. gr. o 8i, and 15 grams nitrate of urea, and distil to one- eighth of its volume. Wash well with water, and dry over CaCl 2 or K 2 CO 3 . Properties. Ethyl nitrate is a colourless, mobile liquid, with a pleasant smell and sweet taste, b.p. 86, sp. gr. 1*112 at . It burns with a white flame, and its vapour, when strongly heated, explodes violently. When reduced by tin and HC1, hydroxylamine is produced. Water and alkalis, the latter readily, decompose it into the alcohol, and acid or salt of the acid respectively C 2 H 5 ON0 2 -f NaOH = C 2 H 5 OH + NaNO 3 ESTERS OF HYDROGEN SULPHIDE, OR THIO-ALCOHOLS AND THIO-ESTERS. Just as the alcohols and ethers may be considered as derived from water, by the replacement of hydrogen by alky] Mercaptans 113 groups, .so the thio-alcohols and thio-ethers may be looked upon as bearing a similar relation to hydrogen sulphide. HOH gives C 2 H 5 OH and (C 2 H 5 ) 2 O andHSH C 2 H g SH (C 2 H 5 ) 2 S Since hydrogen sulphide, however, possesses acid pro- perties, the thio-alcohols and ethers may also be looked upon as its ethereal salts. THIO-ALCOHOLS OR MERCAPTANS; i.e. ACID ESTERS OF HYDROGEN SULPHIDE. Of these bodies the simplest is Methyl Mercaptan, CH 3 SH, or methyl sulphydrate, which occurs in human excrement, and can be prepared by distilling potassium methyl sulphate with potassium hydrosulphide S0 4 + KSH = CH 3 SH + K 2 S0 4 It is a light, colourless liquid with an unpleasant odour (P), 1 b.p. 21. Mercaptan, or Ethyl Mercaptan, C 2 H 5 SH, thio- alcohol, may be formed (*i) by distilling potassium ethyl sul- phate with KSH C 2 H 5 SO 4 K + KSH = C 2 H 5 SH + K 2 SO 4 The student may note that this reaction is quite analogous in character to saponification by KOH. (*2) The mercaptan is also produced when chlor- or iodo-methane is acted upon by KSH (compare Formation i of Alcohols^ p. 94) C 2 H 5 I + KSH = C 2 H 5 SH + KI Properties. Ethyl mercaptan is a very mobile, colourless liquid, b.p. 36*5, and sp. gr. 0*8391 at -&. It possesses a very strong garlic-like odour (?) and an unpleasant taste. It is almost insoluble in water, but soluble in alcohol and ether. It burns with a pale blue flame, and has a neutral reaction. 1 It has recently been stated that neither the mercaptans nor the alkyl sulphides possess (if perfectly pure) the unpleasant smell usually attributed to them. 1 14 Compound Ethers When a drop of it is exposed on a glass rod and agitated in the air it becomes solid. It forms metallic compounds more readily than does alcohol ; these are analogous to the alco- holates, and are called mercaptides. Thus mercaptan acts with violence upon the oxide and salts of mercury, forming the compound (C 2 H 5 S) 2 Hg, mercury mercaptide; hence its name (mercurio captans). If mercaptan is treated with potassium, hydrogen is evolved and potassium mercaptide formed. When mercaptan is oxidised by HNO 3 , sp. gr. 1-4, it forms ethane sulphonic acid, C 2 H 5 SO 3 H (usually termed ethyl sul- phonic acid), and if sodium mercaptide is exposed to air it forms the sodium sulphonate of ethane, C 2 H 5 SO 3 Na. These reactions are of considerable interest in determining the con- stitution of the sulphonic acids (see p. 116). General Remarks. Besides the methods given, mer- captans are notably produced by reduction of the acid chlorides of sulphonic acids (q.v.) ; and also by the action of P 2 S 5 on alcohols 5 C 2 H 3 OH + P 2 S 5 = sC 2 H 5 SH + P 2 O g Properties. The fatty mercaptans are mostly colourless or yellow liquids, which are almost or quite insoluble in water, possess a very disagreeable odour (?), and resemble mercaptan in their principal properties. A characteristic colour reaction (green) is obtained when a i per cent, solution of isatin in strong H 2 SO 4 is shaken up with a mercaptan. THIO-ETHERS, i.e. NEUTRAL ESTERS OF HYDROGEN SULPHIDE. Ethyl Sulphide, (C 2 H 5 ) 2 S, will serve as an example of these, and is produced (*i) by the distillation of an alcoholic solution of K 2 S and potassium ethyl sulphate 2 C 2 H 5 KS0 4 + K 2 S = (C 2 H 5 ) 2 S + 2 K 2 SO 4 or (*2) when ethyl chloride is passed through a hot alcoholic solution of K 2 S 2C 2 H 5 C1 + K 2 S = (C 2 H 5 ) 2 S + 2KCI Thio-ethers 1 1 5 Other ethyl esters than C 2 H 5 C1 may be employed. Also (*3) when P 2 S 3 acts upon ethers, replacing the oxygen 5(C 2 H 5 ) 2 + P 2 S 5 = (C 2 H 5 ) 2 S + P 2 5 and (*4) by the action of ethyl iodide upon potassium mer- captide (compare the formation of ether from ethyl iodide and an ethylate, p. 105) C 2 H 5 T + C 2 H 5 SK = (C 2 H 5 ) 2 S + KI Properties. Ethyl sulphide is a colourless, oily liquid with a disagreeable smell (?), b.p. 93 (cor.), sp. gr. 0-8368 at 2 ? . burns with a blue flame, and takes fire when poured into chlorine. It differs from mercaptan in having no action upon HgO. On oxidation with nitric acid, it yields either di-ethyl sulphoxide, (C 2 H 5 ) 2 SO, or di-ethyl sulphone, (C 2 H 5 ) 2 SO 2 , accord- ing to the strength of acid employed. Like ordinary ether, it forms compounds with various metallic salts. It reacts readily with C 2 H 5 I to form tri-ethyl sulphine iodide (C 2 H 5 ) 2 S + C 2 H 5 I = (C 2 H 5 ) 3 SI a substance which crystallises in colourless plates, and is decomposed by moist silver oxide with the formation of tri-ethyl sulphonium hydroxide, (C 2 H 5 ) 3 SOH, which is strongly alkaline and caustic, liberates ammonia from its salts, precipitates many metallic hydroxides, redissolving A1(OH) 3 , and forms neutral salts with acids. ESTERS OF SULPHUROUS ACID. Esters of sulphurous acid can be formeo^, which show that its compounds may exist in two isomeric forms (compare Nitrous Acid, p. 108), which correspond to symmetric and unsymmetric varieties respectively. Thus sulphurous acid may be represented by two formulae TT and SO L < OH Derivatives of the acid of the first formula are called esters of sulphurous acid, while those of the second are sulphonic acids or their derivatives. ii6 Compound Ethers It is quite sufficient to describe the ethyl derivatives in order to illustrate the characters of the two series. Ethyl Hydrogen Sulphite, Ca ^pSO 8 , is not known free, and its potassium salt, C 2 H 5 KSO 3 , is also comparatively unstable. Ethyl Sulphite, (C 2 H 5 ) 2 SO 3 is formed by adding an excess of absolute alcohol either to thionyl chloride or to sulphur chloride. The former reaction may be expressed thus SOCL + 2C 2 H 5 OH = (C 2 H 5 O) 2 SO + 2HC1 Thionyl chloride Properties. It is a colourless, mobile liquid, which smells something like peppermint, b.p. 161, and sp. gr. 1*085 at &'. It is soluble both in alcohol and ether, but not in water. Water or aqueous alkalis saponify it, more rapidly at a high temperature (C 2 H 6 O) 2 SO + 2KOH = 2 C 2 H 5 OH + K 2 SO 3 Ethane Sulphonic Acid, or Ethyl Sulphonic Acid, C 2 H 5 SO 2 OH, is formed (*i) by the oxidation of mercaptan with HNO 3 , or of sodium mercaptide in air C 2 H 5 SH + O 3 = C 2 H 5 SO 2 OH (*2) The salts of this acid are formed when ethyl iodide acts upon a neutral sulphite, preferably an ammonium salt, at 120-150 in aqueous solution K.SCXOK + C 2 H 5 I = C 2 H 5 S0 2 OK + KI Properties. Ethyl sulphonic acid is a thick acid liquid, which crystallises in the cold, and decomposes on heating. It is not saponified by boiling with K.OH solution, but on fusing with solid KOH it reacts in the ordinary manner C 2 H 5 SO 2 OK + KOH = C 2 H 5 OH + KSO 2 OK PC1 5 forms the sulphonic chloride C 2 H 5 S0 2 OH + PC1 5 - C 2 H 5 S0 2 C1 + POC1 3 + HC1 which on reduction by nascent hydrogen yields mercaptan. Constitution. The formation of ethane sulphonic acid by Snlphonic Acids 117 oxidation of mercaptan is of great theoretical importance ; it points clearly to the conclusion that the sulphur atom is linked to a carbon atom. Of course, it may be argued that there may have been a rearrangement of atoms ; this idea is, however, excluded by the fact that the sulphonic chloride on reduction again yields mercaptan. The fact, too, that, unlike esters in which the alkyl group is attached to oxygen, the sulphonic acids are only saponified with difficulty (see Nitro- ethane, p. in), also supports the unsymmetrical formula. The neutral esters of the sulphonic acids are produced by methods which can be exemplified by Di-ethyl Sulphonic Acid, C 2 H 5 SO 2 .OC 2 H 5 , which can be made (* i ) by acting with silver sulphite upon ethyl iodide in ethereal solution 2C 2 H 5 I + AgSO 2 .OAg - C 2 H 5 SO 2 .OC 2 H S + 2AgI In this case, apparently, one of the silver atoms is directly united to the sulphur atom (compare formation of nitro-ethane from AgNO 2 , p. no). (*2) It is formed when ethyl sulphonic chloride acts upon sodium ethylate C 2 H 5 SO 2 C1 + C.,H 5 ONa - C 2 H 5 SO 2 .OC 2 H 5 + NaCl It is a liquid, b.p. 213, sp. gr. 1*17. These neutral esters boil at higher temperatures than the isomeric sulphites. Like them, on boiling with water or dilute alkalis they undergo saponification, but only one of the ethyl groups is split off, leaving a sulphonic acid C 2 H 5 SO 2 .OC 2 H 5 + H 2 O = C 2 H 5 OH + .C 2 H 5 SO 2 .OH This shows that in these compounds one ethyl group is very differently linked to the other, and supports the conclusions already arrived at as to the constitution of the sulphonic acids. ESTERS OF SULPHURIC ACID. Since sulphuric acid is di-basic it can form two series of esters, the acid and neutral salts respectively. Methyl Hydrogen Sulphate, C ^ 3 j SO 4 , or methyl 1 1 8 Compound Ethers sulphuric acid, is the first example of the acid esters, and is an oily liquid, which does not solidify at 30 C. C H Ethyl Hydrogen Sulphate, ' T/^SO 4 ,- ethyl sulphuric acidy sulpho-vinic acid^ can be formed (*i) by mixing ethyl alcohol with concentrated H-jSO 4 C 2 H 5 OH + H 2 SO 4 = C 2 H 5 S0 4 H + H 2 O The reaction only takes place on heating, and is never complete, but the amount produced increases as the excess of one constituent over another is increased. Process. Mix 90 grams of C 2 H 5 OH and 60 grams of strong H L ,SO 4 together ; heat to 100 for about an hour, and then allow to stand in a warm place for twenty-four hours. Dilute the mixture with water, and neutralise with either BaCO 3 or PbCO 3 , so as to precipitate the excess of sulphuric acid as BaSO 4 or PbSO 4 . Evaporate the clear liquid to the crystallising point, and decompose the salts of Ba or Pb by H 2 SO 4 or H 2 S as required. Filter from the precipitate formed, and concentrate in vacua over cone. H 2 SO 4 . (2) Ethyl sulphuric acid may also be formed by the combination of ethylene with sulphuric acid. Properties. Ethyl sulphuric acid is a colourless, oily liquid, sp. gr. 1*316 at ~. It has a strongly acid reaction, and does not wet glass. It is soluble in water and alcohol, but not in ether. Its aqueous solution saponifies slowly in the cold, and rapidly when heated, forming alcohol and sulphuric acid C 2 H 5 S0 4 H + H 2 - C 2 H 5 OH + H 2 SO 4 If heated with alcohol to 140, it yields ether and H 2 SO 4 C 2 H 5 SO 4 H + C 2 H 5 OH - (C 2 H 5 ) 2 O + H 2 SO 4 Heated alone, it gives first ether, and at a higher temperature ethylene. The remaining basic hydrogen atom may be replaced by metals, with the formation of soluble salts, which decompose on boiling with water or with sulphuric acid. Methyl Sulphate, (CH 3 ) 2 SO 4 , is an oil which smells like peppermint, b.p. 188, and sp. gr. 1*324 at -.-. Ethyl Sulphate, (C 2 H 5 ) 2 SO 4 , occurs occasionally in the preparation of ether, and may be produced either (i) by General Remarks on Ester 1 19 the action of SO 3 on alcohol or ether, or (*2) of H 2 SO 4 on alcohol ; also (3) from ethyl iodide and silver sulphate Ag 2 S0 4 + 2C 2 H 5 T = (C 2 H 5 ) 2 S0 4 + 2 AgI It is an oily liquid, b.p. 118 at 40 mm., sp. gr. 1*1837 at ~-\ and solidifies about 25. It smells like peppermint. GENERAL REMARKS ON THE ESTERS. The following methods, which are general in their applica- tion to the formation of esters, have received illustration : 1. Action of acids on alcohols. It should be noted here that these reactions are seldom complete. They are hastened by heat and by the withdrawal from the sphere of action of the water and the ester formed ; but, ordinarily, a time arrives at which the saponifying effect of the water formed upon the ester is equal in effect to the esterifying influence of the acid ; and a state of equilibrium then ensues. 2. Action of alkyl iodides on silver salts. 3. Action of an alcohol on an acid chloride. 4. Distillation of a salt of the acid of which the* ester is required, with an alkyl salt, say of sulphuric acid. Properties. All esters (with the exception of nitro com- pounds and sulphonic acids) can be decomposed by boiling with alkalis, frequently also with water or dilute acids, the alcohol being re-formed ; this operation is termed " saponifica^ tion." The reader must remember that the haloid esters (p. 78) are usually exceptions to this rule, as they yield, except under special circumstances, olefines. The neutral esters are mostly liquids with an agreeable smell, volatile and neutral in reaction ; the acid esters are not volatile without decomposition, and are acid in reaction. The former are almost or quite insoluble in water, the latter readily soluble. Their constitution is most readily explained by look- ing upon them as alkyl salts of the acids from which they are derived ; which view is supported by their reactions. I2O Aldehydes and their Derivatives CHAPTER XVI. ALDEHYDES AND THEIR DERIVATIVES. Formaldehyde, CH 2 O Propaldehyde, C 3 H 6 O Acetaldehyde, C 2 H 4 O Butaldehyde, C 4 H 8 O, etc. ALDEHYDES are oxidation products of primary alcohols in which the CH 2 OH group of the alcohols becomes changed to CHO. Probably the first result of such oxidation is to form the group CH(OH) 2 . This group, however, is very unstable, and immediately loses water, forming the anhydride or aldehyde, which contains two atoms of hydrogen less than the original alcohol. This is an illustration of the theory, thoroughly supported by experiment, which holds that, except under exceptional circumstances, no carbon atom can be linked to more than one hydroxyl group. So, e.g., ethyl alcohol, CH 3 .CH 2 (OH), might be expected to yield, on further oxidation, ethylidene glycol, CH 3 .CH(OH) 2 , while actually it gives acetaldehyde, which is represented by the formula CH 3 .CHO. While, how- ever, ethylidene glycol is unstable, several of its derivatives are stable, e.g. acetal and chloral hydrate, which will be dis- cussed later. Aldehydes may also be viewed from another standpoint, as reduction products of carboxyl acids, or as hydrides of acid radicles. As aldehydes are the first oxidation products of alcohols, so acids are the second. It will be remembered that the primary alcohols contain the monad group CH 2 (OH); the aldehydes are characterised as just described by the group CHO or C\u ; while the carboxyl acids include the group CO.OH. E.g. ethyl alcohol is CH 3 .CH 2 OH, acet- aldehyde CH 3 .CHO, and acetic acid CH 3 .COOH. The group CH 3 .CO, acetyl, is common to both the aldehyde and the acid, which may therefore be looked upon as the hydride and the Formaldehyde 121 hydroxide respectively of that radicle. The fact that aldehydes may be obtained by reducing acids, and also themselves yield the acids by oxidation, supports such view. It will suffice for our purpose to study the first two members of the series, viz. formaldehyde and acetaldehyde. Formic Aldehyde or Formaldehyde, H.CHO, methyl aldehyde. This substance probably occurs in plant-cells which contain chlorophyll, and is produced most readily (*i) by the moderated oxidation of the vapour of methyl alcohol CH 3 OH + O = H.CHO + H 2 For this purpose a mixture of the alcohol vapour and air is passed over a heated platinum spiral, or over platinised asbestos, or platinum or copper wire contained in a tube, and the vapour drawn through a condenser. A solution of the aldehyde in methyl alcohol is thus obtained. Loew obtained, by the use of glowing copper, a 15-20 per cent, solution; with a platinum spiral over a spirit-lamp, only i per cent, solutions can be obtained. Process i. Fig. 37 shows an apparatus by which small quan- tities of the aldehyde may be obtained. It consists essentially of a spirit-lamp, in which methyl alcohol is placed. A platinum spiral surrounds the wick. The lamp is ignited, and when the spiral is red hot the flame is extinguished, and the funnel, con- nected with a condenser and aspirator, is brought down close to the card which is placed on the lamp. With careful adjustment of the amount of air, the wire will continue glowing, and small quan- tities of the aldehyde can be obtained in a receiver connected with the other end of the condenser. ^ Process 2. For larger quantities, the apparatus shown in Fig. FIG. 37. 122 Aldehydes and their Derivatives 38 may be conveniently employed. It consists essentially of the flask A, which contains methyl alcohol, and is connected with a hard glass tube 12 inches long, in which are two rolls of copper gauze 2 inches in length at a and b. The other end of the tube is attached to a spiral condenser, which is connected with a flask that can be cooled by ice water. This is followed by a Woulffe's bottle containing dilute NH 4 OH, and the whole is fitted to a filter pump. That part of the hard glass tube containing the gauze b is then gently heated, the alcohol warmed to 45-50, and a current of air, dried by passing through concentrated H 2 SO 4 , is rapidly drawn through the whole apparatus. If the supply of alcohol is kept up, FIG. 38. and the receiver occasionally emptied, the process goes on con- tinuously. The first plug of copper gauze a prevents any slight explosion (which may occur on starting the apparatus) from being communicated to the flask. This apparatus will also produce aldehydes from ethers and hydrocarbons. Formaldehyde (*2) is also formed when calcium formate is distilled (H.COO) 2 Ca = H.CHQ + CaCOs And (3) by the action of the silent electric discharge on a mixture of CH and CCX. Formaldehyde 1 2 3 Properties. Formaldehyde is a gas with a very strong pun- gent odour which excites tears ; it is also known in solution ; but it is not possible to obtain it pure, because it so very readily polymerises. By freezing the solution usually obtained, and removing the ice formed, it can be concentrated ; but if it is evaporated over sulphuric acid or in a vacuum, a white solid, paraformaldehyde, is rapidly formed. Warmed for some time with dilute NaOH, formaldehyde yields methyl alcohol and sodium formate. It reacts with ammonia to form hexamethyleneamine, (CH 2 ) 6 N 4 , and if a known amount of ammonia is used, the residual quantity may be determined by titration with sulphuric acid in presence of litmus, and the amount of aldehyde present thus determined. Formaldehyde is a powerful reduc- ing agent ; thus with ammoniacal silver solutions, it yields a silver mirror, formic acid being simultaneously formed H.CHO + Ag 2 O = H.COOH + Ag 2 It also readily " condenses " in the presence of many bases, pro- ducing bodies which apparently belong to the sugars, (CH 2 O) 6 . When formic aldehyde is first treated with H 2 S, and then boiled with strong HC1, it yields tri-thio-methylene, (CH 2 S) 3 . Formaldehyde is an antiseptic, and finds employment now as a preservative of milk under the name of " formalin." Constitution. It is only possible, consistently with the tetravalency of carbon, to write the formula of formaldehyde thus The spontaneous formation of Par a form aldehyde, (CH 2 O) 3 , has already been noted; and it, and not di-oxy- methane, is also formed when di-iodo-methane (methylene iodide) is treated with silver oxide or heated with silver oxalate. It is a white crystalline body, which sublimes at about 1 00, but melts at 153-172, and is resolved by heat into the aldehyde. It is insoluble in cold water, alcohol, and ether, but is soluble in alkalis. When heated to 100 with water, it is resolved into ordinary formic aldehyde ; but if a trace of H 2 SO 4 is present, I2 4 Aldehydes and their Derivatives and it is heated to about 120, 'it is changed Into the isomeric a-tri-oxy-methylene, which melts at 6 1. This body is soluble in water, alcohol, and ether. Very probably there also exists another polymeride of formic aldehyde that corresponds to the formula (CH 2 O) 2 . Acetic Aldehyde, or Aeetaldehyde, CH 3 .CHO, ethyl aldehyde. This body was given the name aldehyde by Liebig, as a contraction for " alcohol dehydrogenatum," which signified that it was obtained from alcohol by loss of hydrogen. It occurs in spirit that has been filtered through charcoal, FIG. 39. and also in the first runnings of that which is distilled from a Coffey's still (see p. 89), from which it can be obtained by rectification ; and is a product of the dry distillation of wood, sugar, and other bodies. Aldehyde is formed (*i) by the oxidation of ethyl alcohol by various oxidising agents, as, for example, air in presence of platinum black ; nitric acid, hence its presence in " nitrous ether ; " chlorine ; chromic acid ; and manganic oxide and sulphuric acid CH 3 .CH 2 OH + O = CH 3 .CHO + H 2 O ^Process. Use the apparatus given in Fig. 39. Place in the i|-2 litre flask 100 grams of granulated K 2 Cr 2 O 7 . Add to this a A cetaldehyde \ 2 5 well-cooled mixture of 400 grains water, 100 grams alcohol, and 140 grams concentrated H 2 SO 4 . Add the mixture very gradually , because heat is evolved and the reaction is often violent. Alde- hyde is formed, and distils over through the condenser (the water of which should be kept at about 25) while most of the alcohol and acetai volatilised at the same time flow back into the flask. The more volatile aldehyde is received in the two cylinders, which are half full of dry ether, and are kept cool by being surrounded with ice and salt. The reaction is completed by applying heat to the flask from the water-bath, and, when over, the tube is disconnected from the condenser and attached to an apparatus which furnishes dry ammonia, which is passed into the ether till no further precipitation occurs. Aldehyde ammonia separates as crystals, which can be filtered off, washed with ether, and dried on filter-paper. These crystals, if distilled with H 2 SO 4 , yield aldehyde, which can then be separated from the aqueous dis- tillate by distillation over fused CaCl 2 at a temperature not ex- ceeding 30. Aldehyde is also formed (*2) by the dry distillation of a mixture of calcium formate and calcium acetate (H.COO) 2 Ca + (CH 3 .COO) 2 Ca = 2 CH 3 .CHO + 2 CaCO ;5 and (*3) it can be obtained by reduction of acetyl chloride or acetic anhydride CH 3 .COC1 + H 2 = CH 3 .CHO + HC1 (CH 3 .CO) 2 O + 2H 2 = 2 CH 3 .CHO + H 2 O Properties. Aldehyde is a mobile colourless liquid, b.p. 21, sp. gr. 07876 at {-. It has a somewhat peculiar ethereal smell, is inflammable, and burns with a blue flame. Its vapour, if inhaled in large quantity, produces cramp of the breast. It is miscible in all proportions with water, alcohol, and ether, and dissolves sulphur, phosphorus, and iodine. If perfectly pure, aldehyde is stable, but very small quantities of other substances render it liable to change. In presence of air it is slowly oxidised to acetic acid ; platinum black and other substances increase the speed of change. Acetaldehyde is a strong reducing agent ; thus if a little is added to an ammoniacal solution of AgNO 3 and gently warmed, a silver mirror is produced 126 Aldehydes and their Derivatives the presence of NaOH makes this reaction more sensitive. It also reduces salts of other noble metals, and Fehling's solution. On the other hand, aldehyde is readily reduced by sodium amalgam to alcohol. Aqueous alkalis produce a brown resinous substance when warmed with it. Chlorine acts on it, forming acetyl chloride CH 3 .COC1; in aqueous solution it forms chloral, CC1 3 .CHO. When acetal- dehyde is treated with PC1 5 , ethylidene chloride, CH 3 .CHC1 2 , is produced ; similarly PCl 3 Br 2 produces the corresponding bromine derivative. Aldehyde enters into remarkable and characteristic molecular combinations with several reagents ; e.g. with NH 3 , NaHSO 3 or KHSO 3 , and with HCN. With NH 3 it forms aldehyde ammonia (compare formaldehyde) CH 3 .CHO + NH 3 = S . NH 2 soluble in water and alcohol, insoluble in ether; with a saturated solution of NaHSO 3 , a crystalline compound CH 3 .CHO + NaHS0 3 = . T SO 3 Na Both this and the aldehyde ammonia are readily decomposed by dilute alkalis or acids yielding the free aldehyde, and can thus be employed for its purification. With HCN it combines, forming ethylidene cyan-hydrin, an oxy-nitrile CH 3 .CHO + HCN = this on treatment with dilute HC1 yields the corresponding lactic acid (see p. 228). Aldehyde also undergoes character- istic reactions with hydroxylamine and phenyl-hydrazine to form aldoximes and hydrazones respectively (see these, p. 129). Constitution of Aldehyde. It has been said that aldehyde, when treated with PC1 5 , yields ethylidene, chloride ; i.e. CH 3 .CHO + PC1 5 - CH 3 .CHC1 2 + POC1 3 in which one atom of oxygen is replaced by two atoms of A cetaldehyde 1 27 chlorine. Now, it has been already shown (pp. 65, 83) that if oxygen is present as hydroxyl, OH is displaced by CI, e.g. C 2 H 5 OH + PC1 5 = C 2 H 5 C1 + POC1 3 + HC1 i.e. one atom of chlorine for one atom of oxygen. Evidently, therefore, the oxygen is not present as hydroxyl in aldehyde, an inference which is also supported by the non- formation of metallic compounds from it. The oxygen atom is also in all probability linked to one carbon atom only, for, firstly, aldehyde is produced from ethyl alcohol by an analogous reaction to that in which formaldehyde is produced from methyl alcohol, and in that case the oxygen must be linked to one carbon atom ; and secondly, that assumption best explains the formation from it by PC1 5 , of a di-chlor-ethane which differs from ethylene chloride (see p. 73). Identification. The reactions (i) with KOH, and (2) with ammoniacal silver solutions, may be of assistance ; (3) if a solu- tion of magenta is decolourised by means of SO 2 , and aldehyde added, a deep violet-red shade is obtained. This reaction is given by other aldehydes also. (4) If an alkaline solution of alde- hyde is added to a freshly prepared alkaline solution of diazo- benzene sulphate, and then a little sodium amalgam is added, a red-violet coloration is produced in about 15 minutes. This is characteristic, and not given by chloral. (5) If a freshly prepared strong aqueous solution of metaphenylene diamine is added to an aqueous or alcoholic solution of aldehyde, a blood-red solution with green fluorescence is formed, which, even if the aldehyde is very dilute (i : 200,000), shows a yellow rim. POLYMERISATION AND CONDENSATION OF ALDEHYDE. Aldehyde readily forms three polymeric modifications, known as paraldehyde, metaldehyde, and aldol respec- tively. Paraldehyde, C 6 H 12 O 3 , is readily formed by the addition of a few drops of sulphuric acid to aldehyde, when a rise of temperature and contraction of volume occurs. If the liquid is cooled to o, the paraldehyde separates. The H 2 SO 4 may be replaced by ZnCl 2 , HC1, or COC1 2 . Paraldehyde is a colourless liquid, which solidifies to a solid, m.p. 10-12, b.p. 128 Aldehydes and their Derivatives 124, and sp. gr. 0*999 at y|l It is changed back into aldehyde by distilling with H 2 SO 4 . PC1 5 gives ethylidene chloride. Met aldehyde, C 6 H J2 O 3 . The same reagents which pro- duce paraldehyde will, in a freezing mixture, give metaldehyde ; and the best way to prepare it is to pass a few bubbles of HC1 or SO 2 into aldehyde surrounded by a freezing mixture, when metaldehyde crystallises out. It forms colourless prisms, which sublime at 115, and pass into ordinary aldehyde. PC1 5 forms ethylidene chloride. Neither of these modifications unites with ammonia^ alkaline, bisulphites, or hydroxylamine, and they are not affected by hot KOH. Aldol. When aldehyde is heated with ZnCl 2 , or aqueous solutions of sodium acetate or Rochelle salt, it loses water and undergoes "condensation," forming crotonaldehyde, CH 3 .- CH:CH.CHO. This may really be considered as the result of the second of two reactions, for if aldehyde is allowed to stand for some time with dilute sulphuric acid, a condensation without loss of water occurs, with the formation of aldol, an alcoholic aldehyde; thus 2CH 3 .CHO gives CH 3 .CH(OH).- CH 2 .CHO, which, when heated with ZnCl 2 , loses water, and forms the croton-aldehyde just mentioned. This is an example of the aldol condensation of aldehydes. GENERAL REMARKS ON ALDEHYDES. The formation of aldehydes from (i) alcohols by oxidation ; (2) by distillation of equal molecules of a formate and the salt of the acid corresponding to the aldehyde required ; and (3) by the reduction of acid chlorides and anhydrides ; have been fully illustrated under formaldehyde and acetaldehyde. Properties. The aldehydes are nearly all colourless, volatile liquids ; a few are white solids. They possess a characteristic and not unpleasant odour. They are not so readily soluble in water as alcohols, and the solubility decreases with increase of molecular weight. They are all notable for the ease with which they undergo chemical change ; their reactions with A Idoximes. Hydrazones 1 29 NH 3 , HCN, NaHSO 3 , PC1 C , hydroxylamine, and phenyl- hydrazine, are all characteristic. Aldoximes. When aldehydes are suitably treated with hydroxylamine, they produce aldoximes. Thus CH 3 .CHO + NH 2 OH = CH 3 .CH:N.OH + H 2 O Acetaldoxime It is best to use a solution of hydroxylamine hydro chloride, just neutralised with NaCO 3 , and then to extract the acidified solution with ether. The aldoximes are usually liquids which boil without de- composition, and are split up by boiling with HC1 into their original components CH,.CH:N.OH + H 2 O = CH 3 .CHO + NH 2 OH They are reduced by sodium amalgam to the corresponding amines, and form nitriles (p. 193) when acted on by acetyl chloride (see Ketones). Hydrazones. A very characteristic reaction is that which the aldehydes enter into with phenyl-hydrazine (an aromatic compound) to form the hydrazones or phenyl-hydra- zones; e.g. CH 3 CHO + C 6 H 5 .HN.NH 2 = CH 3 .CH:N.NFT.C 6 H 5 -f H 2 O Acetaldehyde hydrazone The best way to perform this reaction is to make a solution consisting of i part phenyl-hydrazine, i parts sodium acetate, and 8 parts water, and add this to the aldehyde in aqueous solution ; an oily compound in drops, or a crystalline precipitate is then formed. The hydrazones are not volatile in steam, but are resolved by boiling with dilute HC1 into their original constituents. HALOGEN SUBSTITUTION PRODUCTS OF ALDEHYDE. Of the chlorine derivatives which may be obtained by the action of chlorine upon aldehyde or alcohol, only one tri-chlor- aldehyde, or chloral merits attention. Chloral, CC1 3 .CHO, tri-chlor-aldehyde.(\) This sub- stance, which was discovered by Liebig, is obtained when aldehyde is chlorinated in presence of water and CaCO 3 , the K 130 Aldehydes and their Derivatives latter neutralises the HC1 liberated ; if this precaution is not observed, other products are formed CH 3 .CHO + 3C1 2 = CClg.CHO + sHCl (2) The ordinary and most convenient method of producing it is by the chlorination of ethyl alcohol. ^Process. Place 100 c.c. of absolute alcohol in a flask, and surround it with cold water, so as to keep the temperature not higher than 10, then pass in a current of chlorine till the absorp- tion slackens. Next connect the flask with a reflux condenser, warm gently, while still passing in chlorine, till the temperature is 60, and when no further absorption occurs (shown by there being no further increase of weight), stop the reaction. Finally heat the liquid to the boiling point, then cool down, mix it care- fully with an equal volume of strong sulphuric acid, allow to stand, and then distil. Rectify the distillate after standing over CaCO 3 , and collect the portion which boils between 95 and 100 as chloral. Manufactiire. The method is identical with the process described. In making large quantities, the first distillation may be omitted, as the chloral separates and may be drawn off. The reaction involved in the process described is more complex than appears at first sight, and has been shown to occur in the following stages : (i.) The alcohol is first oxidised by the chlorine to aldehyde CH 3 .CH 2 OH + C1 2 = CH 3 .CHO + 2HC1 (ii.) The aldehyde formed combines, at the moment of its formation, with alcohol to form acetal, the di-ethyl ether of ethylidene glycol (see p. 221). CH 3 .CHO + 2C 2 H 5 OH = CH 3 .CH(OC 2 H 5 ) 2 + H 2 O (iii.) The acetal in its turn is chlorinated with the pro- duction of tri-chlor- acetal CH 3 .CH(OC 2 H 5 ) 2 + 3C1 2 = CC1 3 .CH(OC 2 H 5 ) 2 + 3 HC1 (iv.) The tri-chlor-acetal is acted upon by the HC1 pro- duced, leaving "chloral alcoholate," ethyl chloride being simultaneously liberated OH CC1 3 .CH(OC 2 H 5 ) 2 + HC1 = CC1 3 .CH:C + C 2 H 5 C1 Chloral Chloral Hydrate 131 (v.) And finally, on standing with strong sulphuric acid, the alcoholate is decomposed, chloral being liberated 4 H + H 2 O Note. In carrying out the preparation stage (i.) the re- action can be verified by withdrawing a little of the liquid and testing for aldehyde ; while the formation of acetal (stage ii.) may be shown later by mixing a little of the liquid with water, when the acetal separates and renders the liquid turbid. Properties. Choral is a colourless liquid, with a pungent odour, b.p. 98 (cor.), sp. gr. 1-5292 at f; it has a biting taste, and attacks the skin. It solidifies at 75, is soluble in water, alcohol, and ether. It is reduced by nascent hydro- gen to aldehyde, which body it resembles in combining with NH 3 , HCN, and NaHSO 3 . Chloral reduces ammoniacal silver nitrate solution with formation of a mirror (see Aldehyde) ; it is oxidised by nitric acid to tri-chlor-acetic acid ; and when warmed with NaOH or KOH, it is immediately resolved into chloroform and a formate, which can be detected by suitable tests (see Chloroform and Formates). CC1 3 .CHO + NaOH = CC1 3 H + H.COONa In this decomposition, combined with the reactions given for the formation of chloral from alcohol, we have an explana- tion of the chemistry of chloroform manufacture from alcohol (see p. 74), bearing in mind that in that case calcium hydrate replaces the alkalis. If pure, chloral is quite stable, but small quantities of impurities, especially sulphuric acid, induce polymerisation, with the formation of meta-chloral. When mixed with water, it forms a solid body, termed chloral hydrate, which is of considerable technical importance. Chloral Hydrate, CC1 3 .CH(OH) 2 , tri-chlor-ethylidene glycol, is prepared on the large scale from chloral, by mixing it with a suitable quantity of water, and then recrystallising the solid product either from chloroform, or from a mixture of ethylene and ethylidene chlorides which is obtained as a by-product of the chloral manufacture. 132 Aldehydes and their Derivatives Properties. When pure, chloral hydrate forms colourless transparent monoclinic plates, m.p. 57, b.p. 97, and sp. gr. 1-848. Its crystals do not decompose on exposure to the atmosphere, and do not leave an oily stain on filter-paper. It possesses an aromatic odour and a bitter astringent taste. It dissolves readily in water, alcohol, ether, and chloroform. It is decomposed by strong sulphuric acid into chloral and water. It reacts with alkalis in the same manner as chloral, but differs from that substance in not restoring the colour to a solution of magenta which has been decolourised by SO 2 . A very important property of chloral hydrate, discovered by Liebreich in 1869, is that of acting as a powerful hypnotic, and at present large quantities are used in medicine for pro- ducing sleep. Whether its action is due to its own specific properties or to the formation of chloroform in the blood, is still a disputed point. The dose given varies from 5-30 grains. Chloral hydrate for medicinal purposes should answer to the description already given, and should neither give a brown colour if treated with strong H 2 SO 4 , nor be acid to litmus paper, nor give a precipitate with AgNO 3 when in solution in dilute HNO 3 . The following reactions are common to chloral and chloral hydrate : (i) If warmed with alcoholic potash and aniline, the disgusting odour of an iso-nitrile is produced. (2) If boiled with KOH, acidified with acetic acid, and AgNO 8 added, silver is precipitated, due to the formic acid formed. (3) The reactions with naphthol and resorcinol, given for chloroform, also serve for these substances, because they yield CHC1 3 when decomposed by alkalis. Ke tones 133 CHAPTER XVII. KE TONES. KETONES are readily produced by oxidation of secondary alcohols, and may be considered, like aldehydes, as anhydrides of dihydric alcohols, which are formed by oxidation of the corresponding monohydric compounds. Thus (i.) d Propiomc aldehyde CH,CHOH.CH 3 gives- Iso-prpyl alcohol j. Acetone It is convenient to study them at this point, because they resemble aldehydes in many of their reactions, and the first of the series will be taken as an example. Acetone^ CH 3 .CO.CH 3 , di-methyl-ketone, is found in the brain, blood, and urine of diabetic patients. It is produced (i) by the distillation of many organic substances, e.g. citric acid and starch, and is obtained in quantity along with wood spirit in the manufacture of pyroligneous acid. Process. Acetone may be prepared from crude wood spirit by distilling it from over fused CaCl 2 , which retains the alcohol. NaHSO 3 or KHSO 3 is then added in excess to the distillate, and the resulting compound crystallises out. This is pressed, and then decomposed by distilling with dilute Na 2 CO 3 . The dilute acetone is dehydrated with CaCl 2 and rectified. Acetone may also be formed (*2) by the careful oxidation of iso-propyl alcohol CH 3 .CH(OH).CH 3 + O = CH 3 .CO.CH 3 + H 2 O (*3) By the dry distillation of acetates of lead, barium, calcium, or other metal (compare Aldehyde) (CH 3 .COO) 2 Ba = CH 3 .CO.CH 3 + BaCO 3 ^Process. Distil the barium salt in an iron tube at a moderate 1 34 Ketones heat. If the salt is pure, then pure dry acetone is obtained. It can be purified, if necessary, by formation of the compound with NaHSOg as above. (*4) Its production from zinc methyl and acetyl chloride must be carefully noted 2 CH 3 .COC1 4- Zn(CH 3 ) 2 = 2 CH 3 .CO.CH 3 + ZnCl 2 Properties. Acetone is a colourless mobile liquid, b.p. 5 5 -6 (cor.), sp. gr. 07965 at yf. It has a fragrant spirituous odour and a burning taste ; it is very inflammable, and burns with a white smokeless flame. It mixes in all proportions with water, and may be separated from its solution by such salts as CaCl 2 , and K 2 CO 3 ; it is also miscible with both alcohol and ether. Acetone is a useful solvent for many carbon com- pounds such as fats and resins. It is reduced by hydrogen (sodium amalgam and water) to iso-propyl alcohol, pinacone, (CH 3 ) 2 C(OH) I also being formed : and. when oxidised with (CH 3 ) 2 C(OH) chromic acid mixture, it gives acetic and formic acids (CH 3 ) 2 CO 4- 30 = CH 3 .COOH 4- H.COOH The latter acid is broken up in presence of excess of the oxidising mixture into CO 2 and H 2 O. Acetone differs from alde- hydes by not reducing ammoniacal silver nitrate solution. Chlorine and bromine will form substitution products, but in presence of alkalis both those bodies and iodine react to form chloroform, bromoform, and iodoform (see pp. 74-76). C 3 H 6 O 4- 6C1 2 4- H 2 O = 2CHC1 3 4- CO 2 4- 6HC1 PC1 5 forms di-chlor-propane, CH 3 .CC1 2 .CH 3 . Similarly to aldehyde, acetone combines with NaHSO 3 to form the com- pound, (CH 3 ) 2 CC^cr) M , which is decomposed by dilute alkalis; r\TT and with HCN to form a cyanhydrin, (CH 3 ) 2 C^^. With hydroxylamine it forms an oxime, acetoxime, (CH 3 ) 2 C:N.OH, and with phenyl-hydrazine it yields acetone- hydrazone, (CH 3 ) 2 C:N.NHC 6 H 5 . Its reaction with NH 3 is also complicated, a body Acetone. Remarks on Ketones 135 called acetonamine being formed with elimination of water 2(CH 3 ) a CO + NH 3 = CH 3 .CO.CH 2 .C(CH 3 ) 2 NH 2 + H 2 O Constitution. The constitution hitherto assigned to acetone is supported by the following considerations : (i) It can be shown by the action of PC1 5 to contain the carbonyl group CO, this conclusion being supported by its formation by oxidation of a secondary alcohol, and general likeness to aldehyde; and (2) its synthesis from zinc methyl and acetyl chloride leads to the same formula. Identification. (i) The following is a delicate reaction for the detection of acetone : Add excess of NH 4 HO to the solution 4 then iodine in a solution of NH 4 I, till the black precipitate of NI 3 first formed only disappears slowly, and in presence of acetone the solution becomes milky, and iodoform separates ; by this method acetone can be detected in presence of ethyl alcohol. (2) If a solution of HgCl 2 , made strongly alkaline with alcoholic KOH, is added to a solution containing acetone, and the whole shaken, a part of the mercuric oxide is dissolved, and, after filtra- tion, may be detected in the filtrate, either by adding Am 2 S or by acidifying with HC1 and adding SnCl 2 . (3) Add to an aqueous solution of acetone a little sodium nitro-prusside, then some very strong NaOH solution ; a bright red colour is produced, which goes yellow on standing ; acetic acid turns it to a bluer red. GENERAL REMARKS ON KETONES. The formation of acetone illustrates the general formation of ketones (i) by oxidation of secondary alcohols; (2) by distillation of salts of fatty acids ; and (3) from acid chlorides and zinc alkyls. The last two methods can, of course, be modified so as to form mixed as well as simple ketones (CH 3 COO) 2 Ca + (C 2 H 5 COO) 2 Ca = Calcium acetate Calcium propionate Methyl-ethyl ketone Besides the above synthetical methods, they frequently result from the destructive distillation of organic substances. Properties. The ketones are either colourless, aromatic- smelling liquids, which boil without decomposition, or, begin- ning with C 13 H 26 O, crystalline solids. Aldehydes, which contain 136 Fatty Acids the same number of carbon atoms, are isomeric with them. Some of the ketones are easily soluble in water, others only a little or not at all, but they mix in all proportions with alcohol and ether. Many of their reactions and combinations are similar to those of the aldehydes ; thus ketones which contain the group CH 3 .CO unite with the acid sulphites of the alkalis to form compounds which are decomposed by dilute alkalis ; the others, however, do not, with the exception of propione, (C 2 H 5 ) 2 CO, which does so with difficulty. The reactions of acetone with NH 3 , HCN, hydroxylamine and phenyl-hydrazine, with reducing and oxidising agents, and with Cl, Br, or PC1 5 , are quite typical of the series. They may be distinguished from isomeric aldehydes by not reducing ammoniacal silver solutions. Note. The student will do well to tabulate for himself the similarities and differences of the aldehydes and ketones in regard to their preparation ; and of their reactions, more especially with reducing and oxidising agents, hydroxylamine, phenyl-hydrazine, alkaline sulphites, PCl^, etc. CHAPTER XVIII. SATURATED MONOBASIC ACIDS OF THE ACETIC SERIES, OR FATTY ACIDS, CH 2M O 2 . IT has been already stated (p. 120) that the carboxyl acids are the second oxidation products of alcohols, and contain the atomic group, CO. OH, or C _ which is therefore characteristic of them. The principal acids of the series are the following : Formic acid, H.COOH Valeric acids, C 4 H 9 COOH Acetic CH 3 .COOH Caproic C 5 H n COOH Propionic,, C 2 H 5 .COOH Palmitic C 15 H 31 COOH Butyric acids, C 3 H 7 .COOH Stearic acid, C 17 H 35 COOH Only a few of these acids will be considered in detail. Formic Acid 137 Formic Acid, H.COOH, hydrogen-carboxyl acid. Formic acid was first obtained by distilling red ants (Formica rufd) ; hence its name. It is present in various animal fluids, as, e.g., in human blood, sweat, urine, and in the muscles, and in certain caterpillars. It is also found in plant-juices, as in the common stinging-nettle, in tamarinds, and in various pines ; and certain mineral springs contain its salts. (i) Formic acid was early prepared by distilling starch with H. 2 SO 4 and MnO 2 ; many other substances, such as sugar, gums, and grain, yield it when similarly treated. (*2) It is also produced when methyl alcohol is oxidised, e.g. by means of air in presence of platinum black. Experiment 1 5. Place a small portion of platinum black on a watch-glass, moisten with the alcohol, press a piece of blue litmus paper into the mixture, and then cover with a beaker. Reddening of the litmus paper shows the presence of the acid. (3) Formic acid is produced most conveniently in quantity by heating oxalic acid, either alone or better with glycerin, when it loses CO 3 and leaves formic acid COOH | CO 3 = H.COOH COOH Formic acid Oxalic acid Really, however, in presence of glycerin the reaction occurs in three stages : (i.) The crystallised oxalic acid, when heated, loses its water of crystallisation, and is (ii.) decomposed by glycerin, thus COOH , om C 3 H 5 (OH) 3 + I = C,H which freezes to a solid, m.p. 8'6, Formic Acid. Acetic Acid 139 It has a pungent smell, a sour taste, and acts very violently on the skin, producing blisters, and ultimately painful wounds. Addition of water first lowers the boiling point and then raises it, a mixture of 77 parts of acid and 23 parts of water boiling at 107, being always obtained on repeated distillation of the acid. It is a stronger acid than acetic acid, and is a more powerful antiseptic than phenol. Formic acid is readily de- composed by concentrated H 2 SO 4 , with formation of carbon monoxide H.COOH = H 2 + CO It is a powerful reducing agent, its salts reducing alkaline solutions of gold and platinum salts, with separation of the metal ; reducing Fehling's solution with precipitation of Cu 2 O ; and the free acid reduces silver nitrate solution when warmed, with separation of silver and formation of CO 2 H.COOH +Ag 2 = Ag 2 + C0 2 + H 2 O Formates do not reduce ammoniacal silver nitrate. The acid reduces permanganate of potash and chromic acid. Neutral solutions of formates give a red colour with FeCl 3 . It is probable that the powerful reducing properties of formic acid are due to the fact that, although an acid, it also contains the aldehydic group H.CO, thus differing from the higher members of the series. Constitution (see p. 145). Identification. The reactions with AgNO 3 , Fehling's solution, FeCl 3 , and chromic acid serve to identify and to distinguish formic acid from acetic acid. Formates are readily soluble in water, except the lead and silver salts, which are only sparingly soluble. The salts of the alkali metals yield the corresponding oxalates when carefully heated to 250. Acetic Acid, CH 3 .COOH, pyroligneous add, has been known, in the dilute and crude form as vinegar, from very ancient times. It is found both in the free and in the com- bined states in some animal, and many plant juices. It exists, for example, in some plants as the calcium, in others as the 140 Fatty Acids potassium salt ; and esters of it, with glycerin and other alcohols, occur in many oils and fats. Apart from methods which are of purely scientific interest, there are two processes by which acetic acid is produced in a more or less pure state, which from their industrial impor- tance specially claim attention. (i) Acetic acid is a product of the oxidation of ethyl alcohol by means of air in presence of platinum sponge, chromic acid, certain ferments, and other substances, the reaction occurring in two stages, i.e. of alcohol to aldehyde and from that to acid (i.) CH 3 .CH 2 OH + O = CH 3 .CHO + H 2 O (ii.) CH 3 .CHO + O ' = CH 3 .COOH Process. Its formation by this method may be demonstrated as follows : Place a small quantity of alcohol in a dish, over that put a tray containing platinum sponge, and cover the whole with a bell jar which is open at the top and raised from the table at the bottom. Now gently warm the alcohol ; acetic acid will be rapidly formed and condense on the sides of the jar. Its presence may be detected by its odour and its action on blue litmus paper. This method has actually been used for producing the acid in quantity, but its cost has prevented its general adoption. Crude acetic acid is, however, made from alcohol by the oxidising action of a microscopical organism, the Bacterium or My co derma aceti (Fig. 40), which grows upon the surface of the liquid. Pure alcohol remains entirely unaffected if exposed to the action of the ferment ; if, however, weak alcohol is mixed with alkaline earthy and ammonium phos- phates, these supply the nutriment necessary for the growth of the organ- ism, and acetic acid is then produced. FIG. 4 o. j n the manu f act ure of vinegar, the salts which the plant requires are found in the extract from the various fruits and grain, and the albuminous matter which is present furnishes the nitrogen. Vinegar 141 In order to produce vinegar from fermented liquors by the acetous fermentation, the amount of alcohol present must not be too great, or the oxidation will not take place; e.g. in France, in the manufacture of wine vinegar, it is customary to work as far as possible with a wine which contains about 10 per cent, of alcohol. On the other hand, if only 3 per cent, is present, it acetifies too slowly. Manufacture. Wine vinegar is made in 50-100 gallon casks, provided with holes for charging and allowing circulation of air, and arranged in buildings termed " vinageries." They are first filled one-third full of boiling vinegar , after a week a small charge of wine is added, and this is repeated every week till the cask is two-thirds full, when part of the vinegar is drawn off, and the charging commences afresh. The temperature is kept about 25-27 during the process. Quick Vinegar Process. To increase the speed of production, Schutzenberger devised an apparatus, the "Graduator" (Fig. 41), which consists of a large oak tun, A. At a convenient distance from its bottom a number of holes, a, about i inch in diameter are bored, and a perforated false bottom, , is placed just above these. Deal shav- ings are piled on this nearly to the level of the top, c, which has its perforations loosely packed with cotton wick, and contains, besides the small holes thus partially closed, several larger ones, in which glass tubes are fixed. The whole is then covered with a well-fitting lid with a hole in the top. To start the apparatus, vinegar heated to about 25 is poured in, and it drips down by means of the cotton and spreads over the whole surface of the shavings. In a day or two, weak spirituous liquor is poured in and descends similarly. The shavings become covered with the Mycoderma aceti, and expose a large surface to the liquor, while a current of air also passes up through the cask. The vinegar formed can be periodically withdrawn by means of the bent tube and tap. FIG. 41. 142 Fatty Acids It is possible, by the use of this apparatus, to prepare very strong vinegar if the liquor is passed through more than one graduator, as only about 4 per cent, of alcohol is transformed at one passage. It is necessary to carefully regulate the speed of working and the temperature, or else loss of alcohol occurs. Malt vinegar is made from fermented wort by processes which are identical in principle, though differing in detail, from those just mentioned. The vinegars obtained differ in their properties. They may be colourless from white wines or spirits, or brown from malt ; in some cases they are coloured artificially. The amount of acid varies from 4 to 15 per cent, in different vinegars. The B.P. malt vinegar should contain 6 per cent acid, and have a sp. gr. of 1-019. (2) Acetic acid is also made in quantity from the acid tarry liquid obtained when wood is distilled in closed vessels. Manufacture. This liquid contains principally wood spirit, acetone, and acetic acid, and, after separation from the tar, is redistilled. Wood spirit comes over first, and then a crude acid. The impure liquid is neutralised with lime, then allowed to settle, and the clear liquid is drawn off and evaporated down to half its bulk. HC1 is added to this till it is just acid; this causes tar and phenols to separate out. After separation the clear liquid obtained is evaporated to dryness, and heated to char any impurities. The solid residue is then distilled with the necessary quantity of hydrochloric acid, when acetic acid of about 50 per cent, strength is obtained. If this is not pure, it is distilled with potassium dichromate, which frees it from traces of HC1 and empyreumatic impurities. Glacial Acetic Acid. By repeated fractional distilla- tion of the acid described, and separation of the higher- boiling portion, an acid is obtained which solidifies on cooling ; this is termed glacial acetic acid. It is, however, usually produced by forming the sodium salt, carefully and completely drying this, and then distilling it with strong H 2 SO 4 . The acid so obtained must be distilled at least once more, as it contains a little water from the sulphuric acid. A dilute acid distils over first, and then Acetic Acid 143 the anhydrous acid ; this crystallises on cooling, and the crystals, separated, drained, and redistilled, yield a pure acid. The methods of production of acetic acid hitherto considered have been of technical importance ; there are others which must be mentioned, because of their scientific interest. Thus (*3) aceto-nitrile (methyl cyanide), when boiled with acids or alkalis, yields either the acid or its salt CH 3 .CN + NaOH + H 2 O = CH 3 .COONa + NH 3 While (*4) when carbon dioxide acts upon sodium methyl, sodium acetate is produced CH 3 Na + CO 2 = CH 3 .COONa Also (*5) if sodium methylate is heated to 160 with carbon monoxide, the sodium salt is formed CH 3 ONa + CO = CH 3 .COONa Compare the last three reactions with reactions 4, 5, and 6, employed for preparing formic acid (p. 138). The student should specially notice the means by which the synthesis of acetic acid from its elements is possible. The synthesis of alcohol by successive formation of acetylene, ethylene, and ethyl hydrogen sulphate has been given on p. 85, and since alcohol on oxidation yields the acid, the synthesis of the latter body is also possible. But acetylene can also be oxidised directly in presence of dilute potash, with the formation of potassium acetate C 2 H 2 + KOH + O - CH 3 .COOK which furnishes another means of synthetically forming acetic acid. Properties. Pure anhydrous acetic acid is a transparent mobile liquid, b. p. 118-3, S P- g r I '543 at -/ At about 17 it freezes to a crystalline solid, m.p. i6'5. The acid has a pungent odour and a sour taste. It attacks the skin, pro- ducing blisters, and its vapour burns with a pale blue flame. If quite anhydrous it has no action upon litmus paper, although it reddens it in aqueous solution. It dissolves in water in 144 Fatty Acids all proportions, but the specific gravity of the acid does not vary in proportion to its strength ; in fact, a solution containing only 33 per cent, of acid has the same specific gravity at 15 as anhydrous acid. Acetic acid is not readily acted upon by sulphuric or nitric acids. Chlorine attacks it, forming chlor-substitution products ; PC1 5 and PC1 3 form acetyl chloride (q.v.) ; and it can be reduced successively to acetaldehyde and alcohol. It is a useful solvent for many organic bodies, and finds considerable employment in the arts in the pre- paration of the various acetates, etc. Identification. (i.) FeCl 3 solution gives, with a solution of the acid made neutral with NaOH or KOH, a red coloration, and the liquid yields a flocculent brown precipitate when boiled, (ii.) Dry potassium acetate gives, when heated with a small quantity of As 2 O 3 , the disgusting odour of cacodyl (poisonous), (iii.) Add a small quantity of ethyl alcohol to a solution of the acid or a salt, and then an equal volume of strong sulphuric acid, and warm gently ; the odour of ethyl acetate is produced, (iv.) If in the last test the ethyl alcohol is replaced by amyl alcohol, the fragrant smell of jargonelle pears (due to amyl acetate) is obtained. SALTS OF ACETIC ACID. Most of the acetates are readily soluble in water, the silver and mercury salts dissolving with least readiness. As a rule they are also soluble in alcohol (distinction from formates). Some, such as the iron and aluminium salts, decompose, on boiling their solutions, into basic acetates, which are precipi- tated, and free acetic acid. All acetates are decomposed by heat, acetone being usually formed in greater or less quantity. Among the principal salts are the following : Aluminium Acetate, A1(C 2 H 3 O2)3 or A1A 3 , is not known in the solid form, since it decomposes on evaporation ; but in solution in an impure form, which is usually prepared by decomposing lead acetate with aluminium sulphate, it finds very considerable use, under the name of " red liquor," as a mordant in calico-printing. It decomposes on heating, losing acetic acid and leaving a basic salt. Copper Acetates. Of these, the normal cupric acetate, Acetates 145 CuA 2 .H 2 O, forms dark green efflorescent crystals; but more important is verdigris, which is a mixture of basic acetates of copper, and is prepared by exposing copper to the fumes of acetic acid, as, for example, those arising from fermenting wine lees. It is a green solid, which finds some use as a mordant in dyeing silk black. It is also used in the manu- facture of paints. Iron Acetates. Of these the crude ferrous acetate, known as pyrolignite of iron, black liquor, or iron liquor, is technically of great importance. It is a deep black liquor, with a strong and characteristic smell, prepared by dissolving scrap-iron in pyroligneous acid, hence its odour ; and its dark colour is due to a compound of triferric tetroxide formed on exposure to air. It is used in mordanting and preparing both cotton and silk for black dyeing, and for other colours. Lead Acetates. Normal lead acetate, PbA 2 .3H 2 O, sugar of lead, is produced when the oxide or carbonate is dissolved in acetic acid. If crude acid is employed, brown acetate is formed. When pure it forms white crystals, which readily effloresce, and are easily soluble in water and ordinary alcohol, but insoluble in absolute alcohol. It is sometimes employed in dyeing. There are several basic acetates; one of these, which may be prepared by dissolving litharge in a solution of the acetate, is employed in pharmacy in dilute solution as Goulard water. CONSTITUTION OF ACETIC AND FORMIC ACIDS. So far it has been assumed that the constitution of acetic acid is represented by the formula CH 3 .COOH; but it is necessary now to inquire upon what data that formula rests. The elementary analysis of acetic acid gives numbers which lead to the empirical formula, CH 2 O ; if, however, the silver salt is analysed, numbers are obtained which yield the formula C 2 H 3 O 2 Ag, which corresponds to that of C 2 H 4 O 2 for the acid itself, or twice the former number. This latter formula is proved, by a determination of the vapour density, to be also the molecular formula. 146 Fatty Acids These results, however, tell us little about the constitu- tion; the only light they throw on that is this, that in the formula C 2 H 4 O 2 there is one hydrogen atom, which is replace- able by metals, so that the formula might be written C 2 H 3 O 2 H in order to indicate this. It will be remembered that in studying alcohols we found that the (OH) group was replaceable by halogens, if suitable reagents were employed (see p. 65). If now acetic acid is treated with PC1 5 , a substance which is called acetyl chloride is obtained (the group C 2 H 3 O' being termed acetyl), and corresponds to the formula C 2 H 3 OC1. This substance reacts with water, the acid being re-formed and the chlorine elimi- nated as hydrochloric acid ; this reaction, therefore, proves the presence of an OH group in the molecule, so that the formula can now be written C 2 H 3 O.OH. But further, when acetyl chloride is treated with nascent hydrogen, the chlorine atom is displaced by hydrogen, and aldehyde is formed, C 2 H 3 .O.H. This, however, has been shown (p. 127) to contain oxygen bound directly to carbon by both bonds, since when PC1 5 acts on it the compound C 2 H 4 C1 2 is obtained. We can therefore now write the formula for acetic acid C 2 H 3 .O.OH. The next thing to determine is whether the OH and the O are united to the same or different carbon atoms, and numerous reactions lead to the conclusion that they are bound to the same carbon atom. Thus (i.) the saponification of methyl cyanide (prepared by acting on methyl iodide with KCN, i.e. CH 3 I, yields CH 3 .CN), which, on boiling with dilute acids (p. 143), yields the corresponding acid, with elimination of the nitrogen as ammonia CH 3 .CN -f 2H 2 + HC1 = CH..COOH + NH 4 C1 and (ii.) the synthesis of an acetate from sodium methylate and carbon monoxide, and from sodium methide and carbon dioxide (p. 143), as well as the fact that acetic acid on electro- lysis yields ethane (see p. 44), all go to show that the methyl group exists as such in acetic acid, so that the formula can Constitution of Formic Acid 147 be written in the extended form, CH 3 .CO.OH, which has been shown, therefore, to rest on a sound experimental basis. With regard to the constitution of formic acid, CH 2 O 2 , that follows from similar considerations to those just men- tioned ; so, for example, it is formed by the oxidation of methyl alcohol; by the saponification of HCN analogously to that of CH 3 .CN ; and its syntheses from CO and KHO, and CO 2 and H 2 , are not readily explicable by any other formula than H.CO.OH. Acetic acid may therefore be looked upon as derived from formic acid by the replacement of a hydrogen atom by CH 3 , and all other mono-basic acids may be similarly derived. Thus all alcohols are derivable from H.CH 2 OH aldehydes H.COH and acids H.COOH From another standpoint carboxylic acids can be looked OH upon as related to the hypothetical carbonic acid, CO by the replacement of one OH group by an alkyl radicle, while sulphonic acids are similarly derivable from sulphuric acid, HALOID SUBSTITUTION PRODUCTS OF ACETIC ACID. Acetic acid yields haloid derivatives when treated with chlorine or bromine, in which the hydrogen of the methyl group is replaced by the halogen element; from these the iodo-derivatives can be prepared, as well a's numerous other compounds. Mono-chlor-acetic Acid, CH 2 C1.COOH, is prepared by the chlorination of acetic acid. \Process. Pass chlorine into gently boiling glacial acetic acid in a flask provided with a reflux condenser ; if performed in sun- light, the operation is complete in about fifteen hours, without sunlight it takes at least thirty hours. Distil the product with the thermometer in the liquid, and collect apart that which distils between 130 and 190. By repeated rectification of this distillate 148 Fatty Acids a liquid boiling between 185 and 187 is obtained ; allow this to crystallise, press the crystals, and dry in vacuo over H 2 SO 4 and solid KOH. The crystals will then distil at about 186. Properties. Chloracetic acid crystallises in needles or prisms, m.p. 63, b.p. 186; is strongly acid, and soluble in water. The chlorine in it is replaceable by a number of radicles, e.g. OH, NH 2 , CN, and SO 3 H, by similar processes to those employed in preparing similar derivatives of the hydro- carbons, with the formation of hydroxy-acetic, amido-acetic, cyan-acetic, and sulpho-acetic acid respectively. Trichlor-acetic Acid, CC1 3 .COOH, is prepared by the oxidation of chloral with concentrated HNO 3 , as CC1 3 .CHO + HN0 3 = CC1 3 .COOH + HNO 2 ^Process. Heat 100 grams of chloral hydrate till it is just melted, in a 300-400 c.c. flask with a round bottom, and add care- fully 40 grams of fuming H NO 3 . Heat till the reaction commences, then withdraw the flame. When no more nitrous fumes are evolved, and the reaction is over, distil the product ; that which comes over between 193 and 196 is nearly pure tri-chlor-acetic acid. Tri-chlor-acetic acid forms deliquescent scales, m.p. 55, b.p. 195. It is very soluble in water, and strongly acid. CHAPTER XIX. FATTY ACIDS Continued. GENERAL METHODS HIGHER MEMBERS. GENERAL REMARKS ON FATTY ACIDS. HAVING now discussed the preparation and properties of formic and acetic acids, we are in a position to speak of the acids more generally. The following methods of formation, which are of general use, "have already been illustrated by the before-mentioned acids ; thus acids are formed i. By the .oxidation of alcohols and aldehydes. Remarks on Fatty Adds 149 2. By the saponification of alkyl cyanides (nitriles) by heating with alkalis, dilute acids, or water. 3. By the action of CO upon sodium alcoholates at high temperatures. 4. By the action of CO 2 upon sodium alkyls. Besides these methods, they may be formed 5. By the action of strong KOH on aceto-acetic esters (see p. 283) ; (6) by the dry distillation of di-basic acids of the Malonic series (see p. 240) ; and (7) frequently by the decom- position of their naturally occurring esters, the fats and oils. Properties. With the exception of the first three acids, the lower members of the series are oily liquids ; from capric acid upwards they are solids. The liquids have a strongly acid, sometimes disagreeable, odour; the solids are without smell. The lower members are soluble in water; as the molecular weight increases their solubility decreases, till from C 10 they are insoluble. All are easily soluble in alcohol and ether. The lower acids are readily volatilised, but those of high molecular weight are not volatile without decomposition, except at greatly diminished pressures. They can, however, all be easily distilled in a current of steam. The boiling point of acids of like structure increases about 19 for every increment of CH 2 ; but though the melting point of the acids also increases with increase of molecular weight, acids containing an even number of carbon atoms always possess a higher melting points than those with an uneven number of carbon atoms next following them in the series. The fatty acids do not redden litmus paper per se, but do so in solution. They form salts with bases, -and chlorine and bromine act upon them, forming substitution derivatives. Amongst their characteristic reactions must be remembered (1) that they can be reduced to aldehydes and then to alcohols ; (2) that their lime salts, on dry distillation, yield ketones (if a mixture of the salts of two acids is employed mixed ketones result, unless one salt is a formate, when alde- hydes are produced) ; (3) if the dry sodium salts are distilled with soda lime or sodium methylate, they lose CO 2 , and hydro- carbons are produced ; (4) on electrolysis they lose CO 2 with 150 Fatty Acids the formation of hydrocarbons ; and (5) that PC1 5 acts upon them, displacing OH and forming acid chlorides. Isomerism in the Acids. Isomerism in these acids depends upon the same causes as those mentioned in speak- ing of the halogen derivatives of propane, and of the alcohols (p. 79). For since they are mono-derivatives of hydro- carbons, the number of isomers that can be formed depends upon the number of different positions which the carboxyl group, CO OH, can take in the hydrocarbon molecule. Thus there can only be one propionic acid, CH 3 .CH 2 .COOH, since it may be looked upon as ethane in which hydro- gen is replaced by carboxyl; on the other hand, propane can yield two derivatives according to the carbon atom to which the carboxyl group is attached, and consequently there can be two butyric acids, viz. butyric acid, CH 3 .CH 2 .- CH 2 .COOH, and iso-butyric acid, UUUrl Propionic Acid, CH3.CHo.COOH, may be prepared by several of the general methods, e.g. from propyl alcohol, from propionitrile, from sodium ethylate, as well as by the fermenta- tion of calcium malate and lactate. Properties. It is a colourless, somewhat oily liquid, with a smell that resembles both acetic and butyric acids; b.p. 140, sp. gr. 1*016 at o. It is soluble in water, but CaCL throws it out of solution. Its salts are all soluble in water, and generally crystallise readily. Butyric Acids. Two isomers. n-Butyric Acid, CH 3 .CH 2 .CH 2 .COOH, occurs either free or combined in many natural products. It is present, combined with glycerin, in butter, and occurs free in rancid butter. It is also found in cod-liver oil, in muscular juice, and in perspiration, and its esters are found in several fruits. It may be formed from butyl alcohol, and from propyl cyanide, is a product of the fermentation of calcium lactate, and also of many vegetable and animal substances by a species of schizo- mycetes. It has been shown, for example, that Bacillus subtilis acts upon starch, producing butyric acid. Process, Butyric acid is prepared by the fermentation of sugar, Butyric Acids 151 thus : dissolve 6 kilos, of sugar and 30 grams of tartaric acid in 26 litres of hot water, and allow to stand some days ; then add 250 grams of putrid cheese, 8 kilos, of sour skimmed milk, and 3 kilos, of chalk. Keep the mixture at 30-35, stirring every day. At the end of a week a thick magma of calcium lactate is formed, which on longer standing liquefies once more, CO 2 and H being evolved. The reaction is over at the end of six weeks, and calcium butyrate remains in solution. Then precipitate the calcium by adding 8 kilos. Na 2 CO 3 , 10 H 2 O, and decompose the sodium salt formed by adding 11 kilos, dilute H 2 SO 4 . The crude acid which separates may be purified by forming its ethyl ester, rectifying that (b.p. 121), and then saponifying it. The formation of butyric acid occurs in several stages. Sugar, CuHajOn, first forms glucose, C 6 H 12 O 6 , by absorp- tion of water, that yields lactic acid, C 3 H 6 O 3 , which then forms butyric acid according to the equation following 2C 3 H 6 O 3 = C 4 H 8 O 2 + 2CO 2 + 2H 2 Properties. It is a strongly acid liquid, with a disagreeable rancid odour, b.p. 162 (cor.), sp. gr. 0*967 at Y|, and on cooling solidifies to a white mass, which melts at about 3. It is a strong acid, which attacks the skin, is miscible with water in all proportions, and thrown out of solution by salts, e.g. CaCl 2 . Its salts are soluble in water; the calcium salt is less soluble in hot than in cold water, and on heating for some time to 100 it forms calcium iso-butyrate. Iso-butyric Acid, (CH 3 ) 2 CH.COOH, is found in carobs (St. John's bread), in Arnica montana, in Roman oil of chamomile, and in croton oil. It is formed, by general methods, from iso-propyl cyanide ; and from iso-butyl alcohol. Properties. Iso-butyric acid is a liquid, very similar in smell to the normal acid, but not so unpleasant; b.p. 153 (cor.), sp. gr. 0*9539 at yf. It differs from the normal acid by being little soluble in water. The constitutions of the two butyric acids follow from their formation from the two isomeric propyl ,cyanides. Valeric or Pentoic Acids, C 5 H 10 O 2 . Of these there are four possible isomers, 152 Fatty Acids Iso-valeric Acid, (CH 3 ) 2 CH.CH 2 .COOH, or inactive valeric acid, occurs in various natural substances, e.g. dolphin and other fish oils, in valerian root, and in the bark of the wild guelder rose. It can be prepared from the iso-butyl cyanide, and from inactive amyl alcohol, by general processes. It is a mobile oily liquid, b.p. 175, sp. gr. 0-9536 at -; it smells like old cheese, is strongly acid to the taste, attacks the skin, and is little soluble in water. Methyl-ethyl-acetic Acid, CH.COOH, the ^2 H 5 optically active valeric acid, from active amyl alcohol (see p. 102) ; boils at 175, and its sp. gr. is 0-941 at 21. Ordinary valeric acid is a mixture of this and the above-mentioned acid. The other isomers are normal valeric acid, CH :i (CH 2 )3.- COOH, and tri-methyl-acetic acid, (CH 3 ) 3 .C.COOH. Higher Fatty Acids. Many of these acids occur in nature as glyceryl esters in various fats and oils (see p. 153) ; but only those appear to so exist which contain an even number of carbon atoms. They are difficult to separate from each other, this being performed by fractional precipitation. The number of possible isomers for each member is great, but those naturally occurring have been shown to be normal in their structure. The two acids of greatest importance are palmitic and stearic acids. Palmitic Acid, C 15 H 31 .COOH, is found combined with glycerin as palmitin (p. 154) in many fats and oils, such as palm and olive oils, also combined with other alcohols in bees'-wax, spermaceti, and Japan wax. It is found free in palm oil and in lycopodium spores; and can be formed by fusing cetyl alcohol with caustic potash C 15 H 31 CH 2 OH + KOH = C 15 H 31 COOK + 2H a It is best prepared either by saponifying Japan wax, then liberating the acid by HC1 and rectifying it ; or else by sepa- rating it by fractional precipitation with magnesium acetate from the fatty acids obtained from olive oil by saponification, and decomposition of the salts by a mineral acid. Bittter. Oils and Fats. Soaps 153 Properties. Palmitic acid crystallises in white needles, m.p. 6075; its sp. gr. (in the liquid state) is 0-853 at ; it: decomposes on heating to its boiling point, but at 100 mm. pressure its b.p. is 271-5. Stearic Acid, C 17 H 35 .COOH, occurs in association with palmitic and oleic acids as stearin (p. 154) in many fats, such as beef and mutton suet, and hence in tallow. These fats yield a mixture of acids; the solid acids in the mixture are separated by pressure from the oleic acid, and then repeatedly recrystallised from alcohol till the stearic acid is obtained pure. Properties. Stearic acid crystallises from hot alcohol in white pearly plates, b.p. 232 at 15 mm., m.p. 69*2, and sp. gr. i 'oo at . BUTTER. OILS AND FATS. SOAPS. This is, perhaps, the most convenient place to discuss the constitution of the various naturally occurring oils and fats, although the reader must refer to later portions of the book for information on the properties of several of their components. The general term "fat" is applied to a number of more or less greasy substances which are found in animal tissues or are expressed from the seeds of plants. The more liquid fats are generally spoken of as " oils." The oils are divided into non-drying and drying oils, according as they remain unchanged on exposure to air or become oxidised to a resinous compound. Linseed oil is the best illustration of the second class. The animal fatty tissues, such as beef of mutton suet, and the flare of the pig, yield the fat itself on heating, in a fluid form which can be separated from the membrane, and then solidifies. The vegetable fats and oils are obtained from the seeds or fruits which contain them by pressure or by extraction with solvents. These oils and fats are non-volatile, and, when heated with acids, alkalis, or superheated steam, undergo hydrolysis or saponification, with the liberation, usually, of glycerin and fatty acids, which latter vary according to the fat or oil 154 Fatty Acids employed. The fundamental reaction may be illustrated by the following typical equation : C 15 H 31 CO O C 3 H 5 + 3 H 2 = 3 C 15 H 31 COOH + C 3 H 5 (OH) 3 C 15 H 31 CO O/ Palmitic acid Glycerin Glyceryl palmitate, or palmitin If in this reaction alkalis are employed, the resultant pro- duct is not the acid, but the corresponding salt or soap. The fats and oils, therefore, apparently contain fatty or other acids combined with glycerin (see p. 243), or, in other words, they are esters of the acids and glycerin. The principal acids found are palmitic acid, present as " palmitin," stearic acid as " stearin," and oleic acid (p. 2 1 2) as " olein," which substances are the neutral esters of glycerin and the respective acids. Butter is the fatty constituent of milk, obtained from it by churning. It is a mixture of glycerides of butyric, caproic, palmitic, stearic, oleic, and other acids, along with a small percentage of curd and varying quantities of water. The fat can be separated from the curd by melting it in hot water, when the fat rises to the surface. Butter differs from other fats by containing several acids which are readily soluble in hot water. This differentiates it from oleo-margarine, a butter substitute, which is a mixture of fats made from carefully prepared beef fat or lard, along with certain vegetable oils, and, in the higher qualities, some butter. The lower qualities are given the flavour of butter by mixing them with a certain amount of milk, and are coloured with annatto. Soap. Very many different oils and fats are employed in soap-making, e.g. palm, olive, cotton seed, sesame, poppy, and other oils ; tallow, lard, and kitchen grease among animal fats ; and fish oils. These yield hard or soft soaps, according to the alkali employed. Soft soaps are made by boiling such oils as linseed, hemp- seed, olive, and fish oils with potash lye, until the whole is a homogeneous mass. A certain amount of palm oil or tallow Soaps 155 is frequently added, so that the finished product may show white nodules of potassium palmitate or stearate, which pro- duce the appearance technically known as "figging." Soft soap contains from 30 to 50 per cent, of water, as well as the glycerin produced in the saponifi cation. There is always, too, an excess of alkali present. Hard soaps may be made in several ways ; thus some soaps are made by neutralising the "oleine" or "red oil" obtained in stearin manufacture (p. 156) with sodium carbonate or caustic soda, and then running the soap into the cooling frames to solidify. By far the largest quantity, however, is prepared by the saponification of some form of fat, or mixture of fat and resin. The oil is heated in a large pan, and a small quantity of weak soda lye is added, which effects a partial saponification and emulsification ; stronger lye is then added till nearly the whole of the fat is saponified. If the boiling has been properly carried out, there remains then a homogeneous semi-fluid mass of partly formed soap mixed with water and glycerin in what is termed the " close " state. This is " grained " or salted out by the addition of salt, which causes the soap to rise as a curd to the top. The spent lyes, containing salt, glycerin, and impurities, are then drawn off, and the soap is boiled with more alkaline lyes till it is quite alkaline to the taste and saponified completely. The soap paste is allowed to stand, the lyes are drawn off, and the soap heated by blowing steam through it till a certain texture, the " fit," is obtained. It is then allowed to rest, and the soap separates into three layers at the "top a frothy "fob," next " neat " or good soap, and the " niger " (aqueous liquors and impurities) at the bottom. The soap is then drawn off into the cooling frames. This method enables the maker to get an almost neutral soap, and is usually employed for soaps which contain a certain proportion of resin. Curd soap is prepared by boiling a saponified tallow soap with water or weak lye, allowing it to stand so that impurities can settle, and then boiling it down till the flakes show the appearance desired. 156 Fatty Acids Mottled soap is produced by using a mixture of fats, and, after complete saponification and settling, introducing a small amount of ultramarine or copperas before running it into the frames. The colour becomes separated in the more trans- lucent part of the soap. For the purpose of cheapening soap, silicate of soda is often incorporated with it, and does not lessen its detergent properties to a great extent. The composition of soap varies, but may be taken as about 8 per cent, of alkali, 63 per cent, of fatty acids, and 30 per cent, of water. Soap is largely employed as a cleansing agent, for removing grease and other impurities from textile fabrics and from the body. Its action depends upon its hydrolysis by water, free alkali being formed, and an acid soap ; the latter lathers and envelops the particles of dirt, removing them mechanically, while the alkali enables the solution to thoroughly wet the fabric. Soap is also employed as a medicine, both internally and externally ; it acts as a mild alkali. Lead soap, obtained by saponifying olive oil with litharge, is employed as diachylon plaster. " Stearin " and " Oleine." For the purpose of candle manufacture, oils and fats are either heated with lime, the lime soap decomposed by H 2 SO 4 and the fatty acids washed with water, or else they are decomposed by sulphuric acid only, and then washed. The solid stearic and palmitic acids are separated from the oleic acid by crystallisation and pressure. The solid acids form the " stearin" used in making candles, the oleic acid is the " oleine " or " red oil " referred to on P- 155- Acid Haloids. Anhydrides 157 CHAPTER XX. ACID HALOIDS, ANHYDRIDES, ETC. ACIDS can yield two classes of substitution compounds, viz. those in which the hydrogen of the alkyl group^ is replaced by other atoms or radicles (e.g. chlor-acetic acid, p. 147), and those in which the OH group is displaced by such sub- stituents. We shall now consider examples of the latter class. ACID CHLORIDES, BROMIDES, ETC. Acetyl Chloride, CH 3 .COC1, acetic chloride, can be obtained in a variety of ways, use being made of similar reactions to those employed in the preparation of haloid derivatives of the hydrocarbons from the alcohols ; i.e. by the action of the chlorides of phosphorus, phosphorus oxychloride, or hydrochloric acid upon the acid or its salts. So it is produced (*i) when PC1 5 and glacial acetic acid are distilled together CH 3 .COOH 4 PC1 5 = CH 3 .COC1 + POC1 3 4 HC1 (compare the reaction with Alcohol, p. 65). (*2) Acetyl chloride is also formed when POC1 3 acts upon dry potassium or sodium acetate 2 CH 3 .COOK + POC1 3 = 2 CH 3 .COC1 + KPO 3 + KC1 There must not be an excess of the salt, or acetic anhydride is also produced. And (*3) useful reactions for its formation are those in which PC1 3 acts either upon an acetate or the glacial acid 3 CH 3 .COOK 4 PC1 3 = 3 CH 3 .COC1 4 K 3 PO 3 3 CH 3 .COOH 4. 2 PC1 3 = 3 CH 3 .COC1 4- P 2 O 3 4 3HC1 In this, as in the previous case, an excess of the salt or acid causes the production of anhydride. ] Process. Fit a dry distilling flask with a stoppered funnel ; connect the flask tightly to a perfectly dry condenser and a tubu- lated receiver (the latter being fitted with a calcium chloride tube, 158 Acid Haloids > Anhydrides, etc. so as to prevent access of moisture). Place 60 grams of phosphorus tri-chloride in the flask, and carefully add 40 grams of glacial acetic acid by means of the stoppered funnel. Then heat to about 40, and when the evolution of hydrochloric acid has nearly ceased, raise the temperature and collect the distillate, which may be purified by fractional distillation over dry sodium acetate. The whole operation should be conducted in a good fume-cupboard, or out of doors. Keep the acetyl chloride in well-stoppered bottles or sealed tubes. (4) Acetyl chloride is formed when hydrochloric acid and P 2 O 5 act upon acetic acid ; the latter acts as a dehydrating agent. Properties. Acetyl chloride is a mobile, colourless, strongly refractive liquid, b.p. 50 '9 (cor.), sp. gr. i '1305 at - 4 -o. It fumes strongly on exposure to moist air ; its vapour is very pungent and irritating, and attacks the eyes and mucous membranes very violently. It is decomposed violently by water, and alcohols vigorously act upon it, hydrochloric acid being liberated acetic acid is regenerated in the former case, and an ethereal salt formed in the latter CH 3 .COC1 + HOH = CH 3 .COOH + HC1 CH 3 .COC1 + C 2 H 5 OH = CH 3 .COOC 2 H 5 -f- HC1 It can be reduced by sodium amalgam to ethyl alcohol. It reacts with sodium acetate to form acetic anhydride, and with NH 3 to form acetamide (see p. 182). Acetyl Bromide, CH 3 .COBr, can be obtained by the action of phosphorus and bromine upon glacial acetic acid. It is a colourless liquid, b.p. 81, and resembles the chloride in its properties. Acetyl Iodide, CH 3 .COI, cannot be obtained by the action of phosphorus iodide on acetic acid ; it is necessary to use either the anhydride or a salt. It is a brown trans- parent liquid, b.p. 105, sp. gr. 1-98 at ^. It is readily decomposed by water. The methods of preparation and general reactions of acetyl chloride with alcohols, water, ammonia, salts, etc., may be taken as quite typical of the acid haloids generally. Acetic Anhydride 159 ACID ANHYDRIDES. Acetic Anhydride, (C 2 H 3 O) 2 O, acetic oxide, is formed (i), though only in small quantity, by abstracting the elements of water from glacial acetic acid with P 2 O 5 ; (*2) by the action of acetyl chloride upon dry potassium or sodium acetate C 2 H 3 OC1 + CH 3 .C0 2 Na = (C 2 H 3 O) 2 O + Nad ^Process. Allow 30-50 grams of acetyl chloride to run slowly from a stoppered funnel upon an equal weight of dry sodium acetate contained in a 250 c.c. retort or flask connected with a dry condenser and receiver, as for acetyl chloride. Cool the retort till the reaction is over, distil off the anhydride from a sand-bath and rectify by distillation, collecting apart the portion which boils between 135 and 140. By further rectification of this fraction a product boiling at 180 can be obtained. (*3) It is also produced by acting on an acetate with PC1 3 , POC1 3 , or COC1 2 , acetyl chloride being formed first (^.#.), and the previous reaction then taking place. Process. Add 3 parts of POC1 3 to 10 parts of dry sodium acetate, and distil. Rectify the distillate over sodium acetate. Properties. Acetic anhydride is a colourless, strongly re- fractive liquid, and smells somewhat like acetic acid; b.p. 137*8, sp. gr. 1*0799 at l*i2". It has no acid reaction if pure ; is insoluble in water, but, if allowed to stand with that body, eventually combines to form acetic acid ; with alcohols it yields esters. It is readily acted upon by alkalis and alkaline earths, with the formation of acetates. Gaseous HC1 reacts with it to form acetic acid and acetyl chloride (CH 8 CO) 3 + HC1 = CH 3 .COC1 + CH 3 .COOH Chlorine forms a mixture of acetyl chloride and chlor-acetic acid, bromine acts similarly, while iodine has no action. It differs from acetic acid by decolourising potassium permanga- nate, and giving a mirror with an ammoniacal solution of AgNO 3 . It yields aldehyde and then alcohol when reduced by sodium amalgam. Detection of Hydroxyl. It has been pointed out already that acetyl chloride and acetic anhydride both act 160 Acid Haloids, Anhydrides, etc. on alcohols, forming ethereal acetates, and, generally speak- ing, the former reacts with all organic compounds which contain OH, NH 2 , or NH groups, and if there is no evolution of HC1 on its addition, those radicles may be assumed to be absent. In the absence of the two latter groups, the property that the chloride and anhydride have of reacting with hydroxyl is used to show its presence, and to determine how many times that radicle occurs in the molecule. An alcohol may be treated directly with acetyl chloride, or warmed with acetic anhydride and dried sodium acetate. In both cases fragrant esters are formed, which can readily be separated. In the case of an alcoholic acid (i.e. an acid which contains an alcoholic group, e.g. CH 2 OH.COOH) the COOH group must itself be esterified before the alcoholic groups are treated with the above compounds. The number of acetyl groups introduced cannot be ascer- tained by elementary analysis. For this purpose the ester is purified, a known weight of it saponified, and the amount of acetic acid thus freed is estimated; from this amount the number of radicles can be calculated, since one molecule of acetic acid corresponds to one hydroxyl group. ESTERS OF THE FATTY ACIDS WITH MONOHYDRIC ALCOHOLS. Just as when the alcohols act upon inorganic acids ethereal salts are produced, so similarly they form esters with organic acids, some of which are of interest. Methyl Acetate, CH 3 .COOCH 3 , occurs in crude wood vinegar, and is a fragrant colourless liquid, which boils at 57'5. Ethyl Acetate, CH 3 .COOC 2 H 5 , acetic ether, is formed (*i) by the direct action of ethyl alcohol on acetic acid CH 3 .COOH + C 2 H 5 OH = CH 3 CO.OC 2 H 5 + H 2 O but, as we have already seen (p. 119), the reaction is not com- plete. (*2) The method usually employed in its preparation depends upon the action of H 2 SO 4 on a mixture of an acetate and the alcohol, which is, after all, a modification of the first reaction, and probably depends upon the following reactions : Ethyl Acetate 161 (i.) C 2 H 5 OH + H 2 S0 4 - C 2 H 5 SO 4 H + H 2 O (ii.) C 2 H 5 HSO 4 + CH 3 .COONa = CH 3 .COOC 2 H 5 + NaHSO 4 ^Process. Mix together 1 90 grams of concentrated H 2 SO 4 and 36 grams of 95 per cent, alcohol. Allow the mixture to stand for 24 hours, and then pour it on to 60 grams of previously fused and dried sodium acetate, which is broken into small pieces and placed in a flask, which must be kept cool by surrounding it with water. Allow the mixture to stand for 12 hours, and then distil from a sand-bath', and collect the distillate till only water comes over. Shake the distillate with a strong solution of Na 2 CO 3 , separate, then dry over fused CaCl 2 and rectify by distillation, collecting that which distils between 74 and 78. The distillate is nearly pure ethyl acetate, and may be purified by redistillation. Properties. Ethyl acetate is a colourless liquid with a fragrant and refreshing odour, sp. gr. 0-9072 at yf, b.p. 77-5. It mixes readily with alcohol and ether, and is moderately soluble in water. When dry it is stable, but if moist it gradually undergoes saponification, which of course takes place more readily in presence of alkalis CH 3 .COOC 2 H 5 +NaOH = CH 3 .COONa -f C 2 H 5 OH When heated with sodium a rather complicated reaction takes place, which results in the production of a compound called aceto-acetic ester, which has been of great service in the synthetical formation of various acids and ke tones (see Appendix, p. 281). Commercial "acetic ether" is usually a very impure substance, and contains considerable quantities of alcohol, acetic acid, water, etc. GENERAL REMARKS. Esters of organic acids may be produced as just illustrated, viz. (i) from the acid and the alcohol ; (2) from a salt of the acid, H 2 SO 4 and the alcohol. They are also formed (3) when acid chlorides or acid anhydrides act upon the alcohol C 2 H 3 OC1 + C 2 H 5 OH = C 2 H 3 O.OC 2 H 5 + HC1 1 The best way to mix these is to pour the alcohol down a thistle funnel into the acid while stirring constantly with the stem of the funnel. M 1 62 Alky I Nitrogen Compounds and (4) difficultly volatile or non-volatile ethers may be pro- duced by passing gaseous HC1 into a mixture of the alcohol and the acid. Properties. The esters of organic acids are liquid or solid bodies, which are usually insoluble in water. They may be saponified by heating with water, alkalis, or dilute acids. When acted upon by ammonia, acid amides and the alcohols are produced. Many of these esters possess characteristic fruity odours, and are employed as artificial fruit essences ; thus Ethyl Formate, H.CO.OC 2 H 5 , finds employment in flavouring rum and arrack ; Amyl Acetate, prepared from iso-amyl alcohol (p. 101), possesses a pear-like odour, and is used in alcoholic solution as jargonelle pear essence ; Ethyl Butyrate in alcoholic solution is pine-apple oil ; and Amyl Valerate is used as " apple oil." CHAPTER XXI. COMPOUNDS OF THE ALCOHOLIC (ALKYL} RADICLES WITH NITROGEN. THE three elements nitrogen, phosphorus, and arsenic belong, as the student will remember, to the same group, and many of the compounds formed by one element in the group very considerably resemble similar compounds formed by the others. Thus each of the three elements named combines with three atoms of hydrogen to form respectively ammonia, NH 3 , phos- phine, PH 3 , and arsine, AsHg. The hydrogen in these can be more or less readily replaced by alcoholic radicles, and in this manner very important series of compounds are produced, which show similar differences in character to the parent hydrides. Thus ammonia is strongly alkaline, phosphine is less so, and arsine only faintly alkaline ; and the ethyl deriva- tives of these substances show a like gradation of properties. Amines 163 AMINES, AND AMMONIUM BASES. Amines. The term " amine " is applied to compounds which are derived from ammonia by the replacement of its hydrogen by alkyl radicles. If they are derived from one molecule of ammonia, they are called mon-amines ; if from two molecules, di- amines; and if from three molecules, tri-amines. It is possible to replace either one, two, or three atoms of hydrogen in ammonia by alkyl groups. If one atom only is replaced, there is produced a primary amine or amido base, characterised by the amido group NH' 2 , e.g. NH 2 .CH 3 ; if two atoms undergo substitution, a secondary amine or imido base containing the imido group NH" is formed, e.g. NH(CH 3 ) 2 ; while if three groups are introduced, and nitrogen only remains, a tertiary amine or nitrile base is produced, e.g. N(CH 3 ) 3 . The hydrogen atoms are not of necessity all replaced by the same radicles, for it is possible to introduce three different monad groups into the molecule at once. Dyad or triad radicles may also be employed, so that complex amines can be produced with ease, and the number of possible isomers may thus be very considerable. For example, the formula C 3 H 9 N may represent either C 3 H 7 NH 2 , H^ or Propylamine Methyl-ethylamine Trimethylamine The likeness of the amines to ammonia is supported by the formation from them of compounds which are analogous to the ammonium compounds, e.g. the quaternary com- pounds N(CH 3 ) 4 I and N(CH 3 ) 4 OH (the tetra-methyl ammo- nium iodide and hydroxide) are analogous to the ammonium compounds NH 4 I and NH 4 OH respectively. In studying the amines it will be convenient to discuss first one of the general reactions, because certain methods of production apply to all four kinds of amido derivatives. Thus, consider the action of alcoholic ammonia upon alkyl haloids when they are heated together in closed tubes. It may be illustrated by the equations that represent the 1 64 A Iky I Nitrogen Compounds interaction of ammonia and ethyl iodide, in which the hydrogen atoms of the ammonia are successively replaced by ethyl (i.) NH 3 + C,H B I = NH 2 (C 2 H 5 ).HI (ii.) NH 2 (C 2 H 5 ) + C 2 H 5 I = NHCC.H^HI (lii.) NH(CoH 5 ) 2 + C 2 H 5 I = N(C 2 H 5 ) 3 .HI (iv.) N(C 2 H 5 ) 3 + C 2 H 5 I = N(C 2 H 5 ) 4 I or, from another standpoint, the latter phases may be repre- sented (ii.) NH 2 (CoH 5 ).HI + NH 3 + C 2 H 5 I - NH(C 2 H 5 ) 2 .HI + NH 4 I (iii.) NH(C 2 H 5 ) 2 .HI +NH 3 + C 2 H 5 I = N(C 2 H 5 ) 3 .HI + NH 4 I (iv.) N(C 2 H 5 ) 3 .HI + NH 3 + C 2 H 5 T = N(C 2 H 5 ) 4 I + NH 4 I It is only possible by this method to prepare a mixture of bases. In the case cited ethylamine hydriodide is chiefly formed ; when methyl iodide is employed, the tetramethyl ammonium iodide is mainly produced. The bases are separated from each other as follows. The alcoholic solution is filtered ; the residue is NHJ. The filtrate is distilled with KOH, when the amines distil over; the tetra- ethyl ammonium iodide remains behind unaffected. The distillate is dried over solid KOH, and dry ethyl oxalate then carefully added; it is then heated to 100 for some time. Ethylamine and diethylamine respectively form diethyl- oxamide and diethyloxamic ester, while the triethylamine undergoes no change, and can be distilled off. The solid oxamide is separated by pressure from the oxamic ester, or else washed out from it with water. The two substances are then separately distilled with potash, and yield free ethylamine and diethylamine respectively. The above reactions are employed when large quantities of the ethylamines are required, the impure ethyl chloride produced in chloral manufacture being used instead of C 2 H 5 I Process. i part of the crude chloride is mixed with 3 parts of 95 per cent, alcohol, saturated with NH 3 at o, and digested in a closed wrought-iron vessel surrounded by boiling water for i hour. On cooling, NH 4 C1 separates, and the residual liquid is distilled, the alcohol, NH 3 , etc., collected. KOH is added to the residue, and Met /iy lam ine. E thy lam ine 1 6 5 the layer of bases is dried by solid NaOH, and treated as described above. PRIMARY MONAMINES. The general properties of the monamines will be illustrated mainly (though not entirely) by. the ethyl derivatives. Methylamine, CH 3 NH 2 , found in herring-brine, is a product of the distillation of woody and animal matter, and so is found in crude wood spirit. It can be synthetically prepared in several ways besides that indicated on p. 163. A typical method is that in which acetamide (p. 182) is treated with bromine, and then with caustic potash or soda; the methylamine is formed thus CH 3 .CONH a +Br a +KOH = CH 3 .CONHBr + KBr + H 2 O Acetbromamide CH 3 .CONHBr + 3 KOH = CH 3 NH 2 + K 2 C0 3 +KBr-f H 2 O f Process. Mix 20 grams acetamide with 54 grains bromine; keep it cool, and add a 10 per cent, solution of 20 grams KOH till it is nearly decolourised. Then run this from a stoppered funnel into a 500 c.c. distilling flask which contains a 30 per cent, solution of 60 grams KOH, heated to 60-70. Digest for 15 minutes, then boil, and receive the methylamine vapour in hydrochloric acid. Evaporate the solution to dryness, extract the methylamine salt from the NH 4 C1 with hot absolute alcohol and allow to crystallise. On warming these crystals with KOH, the methyl- amine is liberated as an inflammable gas. Properties. Methylamine is a colourless gas condensible to a liquid, b.p. 6, and not solid at 75. It is the most soluble of all gases; i volume of water at 12*5 dissolves 1150 volumes of it. Its odour is ammoniacal and fish-like. Its solution is strongly caustic and alkaline, and precipitates many salts similarly to NH 4 HO, but differs from that body by not dissolving the hydroxides of cadmium, nickel, and cobalt. It forms salts similarly to ammonia. The hydro- chloride forms deliquescent leaflets soluble in water, and gives double salts with PtCl 4 and AuCl 3 . Ethylamine, C 2 H 5 NH 2 , is produced (*i) from ethyl iodide and NH 3 as described on p. 163 the di-ethyl oxamide being decomposed as follows : 1 66 A Iky I Nitrogen Compoiinds CO.NH.C 2 H 5 | + 2KOH = KoC 2 O 4 + 2CoH,NH, CO.NH.C 2 H 5 The di-ethyloxamide (p. 164), after recrystallisation from water, yields it pure. It is also obtained (*2) from propion- amide C 2 H 5 CONH 2 (compare Methylamine) ; and (* 3 ) by re- duction of nitro-ethane, which is a very characteristic method of formation of amines C 2 H 5 NO 2 + 3 H 2 = C 2 H 5 NH 2 + 2 H 2 O and (*4) by the decomposition of ethyl iso-cyanate or cyanurate with KOH CONC 2 H 5 -f 2KOH = C 2 H 5 NH 2 + K 2 CO 3 Properties. Ethylamine is a colourless, mobile, inflammable liquid, b.p. 19, which does not solidify at 140, sp. gr. 0*696. It is hygroscopic, has a strong ammoniacal odour, caustic taste, and alkaline reaction, and absorbs moist CO 2 with the formation of a salt, probably a carbamate. It dis- solves in water with evolution of heat, and is separated from its solution by KOH or K 2 CO 3 . It separates NH 3 from its salts; like methylamine, it precipitates many metallic hydrox- ides, but differs from that and NH 3 by dissolving aluminium hydroxide. It is readily decomposed by nitrous acid, with formation of ethyl alcohol (see p. 168) C 2 H 5 NH 2 + HNO 2 = C 2 H 5 OH + H 2 O + N 2 and gives the carbamine reaction with chloroform and alcoholic KOH (see p. 195). It forms salts, which differ from ammonium compounds by their greater solubility in alcohol. The hydrochloride, C 2 H 5 NH 2 .HC1, forms deliquescent plates, and gives an orange crystalline double salt with PtCl 4 , 2(C 2 H 5 NH 2 HCi).PtCl 4 , also a yellow double salt with AuCl 3 , C 2 H 5 NH 2 HCl.AuCl 3 . SECONDARY MONAMINES. Dimethylamine, (CH 3 ) 2 NH, occurs in Peruvian guano; and can be obtained from the mixture of bases formed by the action of ammonia on methyl iodide. Diethylamine. Trimethylamine 167 Properties. It is a very volatile inflammable liquid, b.p. 7*2, is strongly alkaline, and forms a characteristic yellow precipitate with picryl chloride, C 6 H. 2 (NO 2 ) 3 C1. Diethylamine, (C 2 H 5 ) 2 NH, is obtained by the action of NH 3 upon ethyl iodide, bromide, or chloride (p. 163), then forming diethyloxamic ester (p. 164), and distilling it with KOH CO.N(C 2 H 5 ) 2 | + 2 KOH = K 2 C 2 4 + (C 2 H 5 ) 2 NH + C 2 H 5 OH CO.OC 2 H 5 Properties. It is a colourless inflammable liquid, b.p. 56, sp. gr. 0726 at o. Its smell is strongly ammoniacal ; it is alkaline, readily soluble in water, and differs from ethylamine in not redissolving the precipitate it gives with zinc salts. It reacts with HNO 2 , forming diethyl-nitrosamine (see p. 168) (difference from ethylamine). Its hydrochloride forms non- deliquescent plates, and the platinum double salt forms orange crystals, [N(C 2 H 5 ) 2 H.HCl] 2 PtCl 4 . TERTIARY MONAMINES. Trimethylamine, (CH 3 ) 3 .N, is found in herring-brine, in the juices of many plants, such as Arnica montana, in haw- thorn and pear bloom, in guano and many other animal substances. It can be produced from methyl iodide by the reactions and separation illustrated on p. 164. Manufacture. Large quantities can be prepared from vinasse, a residue obtained in beet-root sugar manufacture (see p. 80). This is distilled, and the distillate condensed in sulphuric acid. Trimethylamine and ammonium sulphates are formed, and the latter separated by crystallisation. The mother liquor is distilled with lime and the distillate neutralised by HC1. On crystal- lising, NH 4 C1 separates, and the mother liquor contains the hydrochloride of the base, from which impure trimethylamine can be separated by an alkali. Properties. Trimethylamine is a liquid, b.p. 3-5, sp. gr. 0-662 at 5. It has a penetrating fish-like smell, is soluble in water, and easily combustible. Uses, It finds employment in producing potassium car- 1 68 A Iky I Nitrogen Compounds bonate by a process quite analogous to the ammonia-soda process, and is used because KHCO 3 and NH 4 C1 differ little in solubility, while (CH 3 ) 3 N.HC1 is much more soluble than the latter salt. Triethylamine, (C 2 H 5 ) 3 N, formed from ethyl iodide (p. 1 64) or by the distillation of tetra-ethyl ammonium hydroxide (q.v.), is a colourless, oily liquid, inflammable, and strongly alkaline; b.p. 90, sp. gr. 07277 at -, little soluble in water. It gives precipitates with many metallic salts, which are usually insoluble in excess. Diagnosis of Amines. One method of separating the three classes of amines has been already illustrated in their separation, given on p. 164. Other methods of distinction are the following : All primary amines give the iso-nitrile reaction with alcoholic KOH and CHC1 3 (see p. 195) C 2 H 5 NH 2 + CHCls 4- KOH = C 2 H 5 NC + 3 KCl + sH 2 O and they also are characteristically decomposed by nitrous acid, with liberation of nitrogen, e.g. C 2 H 5 NH 2 + HN0 2 = N 2 + C 2 H 5 OH + H 2 O As a nitrite is presumably first formed, this reaction is analogous to the decomposition of ammonium nitrite by heat NH 4 NO 2 = N 2 4- HOH + H 2 O They also readily yield mustard oils, e.g. C 2 H 5 NCS, by successive treatment with CS 2 in alcohol and then aqueous ferric chloride (see p. 199). Secondary amines react with HNO 2 to form nitros- amines, e.g. (C 2 H 5 ) 2 NH + HN0 2 = (C 2 H 5 ) 2 N.NO + H 2 O Diethyl-nitrosamine which are neutral oils that reproduce the amine on reduction with Sn and HC1. The nitrosamines give a dark green solution when mixed with concentrated H 2 SO 4 and phenol. This becomes red when diluted, and excess of alkali produces an intense blue or green shade. Finally, tertiary amines are unchanged by nitrous acid. Ammonium Compounds. Hydrazines 169 GENERAL REMARKS ON THE AMINES. The methods of formation already illustrated are all of general application for the production of amines. Properties. The lower members of the amine series are gases ; the higher are liquids, most of which are volatile either alone or in a current of steam. They greatly resemble ammonia, but are more strongly basic, and can expel ammonia from its salts. Their basicity increases with the number of alkyl groups, so that a tertiary amine is a stronger base than a secondary, and that than a primary one. They form salts with acids, and their hydrochlofides combine with PtCl 4 or AuCl 3 to form double salts; they can also replace ammonia in alums. Their other reactions have already been sufficiently illustrated. QUATERNARY OR AMMONIUM COMPOUNDS. The amine bases unite with acids to form true ammonium salts, and they also unite with alkyl haloids to form tetra- alkylated ammonium compounds, of which the tetra-methyl and tetra-ethyl ammonium iodides have been mentioned (pp. 163 and 164). These salts, though not affected by boiling alkalis (p. 164), yield, by the action of moist silver oxide, the ammonium hydroxide derivative. Tetra-methyl Ammonium Hydroxide, (CH 3 ) 4 NOH, and Tetra-ethyl Ammonium Hydroxide, (C 2 H 5 ) 4 NOH, are so formed from the corresponding iodides ; e.g. (C 2 H 5 ) 4 NI + AgOH = (C 2 H 5 ) 4 NQH + Agl On evaporation in vacua both the hydroxides are obtained as crystalline substances, which absorb water and CO. 2 from the air. They are both strongly caustic bodies, resembling caustic potash in their properties, and saponify fats. When neutral- ised with acids, they form salts. HYDRAZINES. Just as amines may be looked upon as derivatives of ammonia, NH 3 , so there exist substances, termed hydrazines, i/o Alky I Phosphorus and Arsenic Compounds which appear to be derived from hydrazine or di-amidogen, NH 2 .NH 2 . This latter substance is not known free, but only as a hydrate and in its salts. Its fatty derivatives are strong bases, thus resembling the amines, and can unite with either one or two equivalents of acids to form salts. They differ from the amines by being powerful reducing agents, e.g. they reduce Fehling's solution. CHAPTER XXII. COMPOUNDS OF PHOSPHORUS AND ARSENIC WITH ALKYL RADICLES. COMPOUNDS OF PHOSPHORUS ; PHOSPHINES, ETC. Phosphines. Primary, secondary, and tertiary phosphines corresponding to the amines can be prepared, but the prin- cipal methods employed differ from those used for the analogous nitrogen compounds. One of the chief substances required for the formation of the phosphorus derivatives is Phosphonium Iodide, PHJ, which can be formed, amongst other ways, (i) by direct union of PH 3 with HI ; (2) by decomposing PI 3 with a little water this being the usual method of manufacture. \Process. Place in a 200 c.c. retort 40 grams of ordinary phosphorus and the same weight of CS 2 ; next add 68 grams of iodine to this solution, keeping it carefully cooled. When the reaction is over, distil off all the CS 2 on a water-bath ; then connect the retort with a CO 2 apparatus, and with a wide condensing tube with a globe receiver and condensing bottles, as arranged in Fig. 42. The first condensing bottle contains dilute HI, and the other water. A slow current of CO 2 is now continuously passed through the apparatus, and the retort is gently heated, while 24 grams of water are slowly added by the drop funnel. The heat of the reaction sublimes most of the PHJ into the tube and the globular receiver, while the HI is absorbed in the condensing bottles. The operation is complete in about 8 hours, and towards its close the Phosphonium Iodide. Ethyl Phosphine 171 retort will require more strongly heating. When no more sublima- tion occurs, the tube is disconnected, one end is corked up, and the PH 4 I is raked out with a wire into dry stoppered bottles. The reaction may be expressed by the equation I3 P + 9 I + 2iH 2 = 2HI Properties. Phosphonium iodide crystallises in glittering transparent prisms ; it boils at about 80, and may be sublimed in HI. It is a powerful reducing agent, and frequently finds employment in organic chemistry on that account; but its FIG. 42. chief use is for the preparation of phosphines and phospho- nium compounds (see below). The phosphines will be illustrated by the ethyl derivatives, and their properties and preparations should be carefully compared with those of the corresponding amines ; their behaviour on oxidation should be especially noted. Ethyl Phosphine, C 2 H 5 PH 2 , is formed when ethyl iodide, phosphonium iodide, and zinc oxide are heated in a closed tube for 6-8 hours to 150. The reaction is compli- cated, but salts of ethyl and diethyl phosphine are principally formed thus 2 C 2 H 5 I + 2 PHJ + ZnO = 2 C 2 H 5 PH 2 .HI + ZnI 2 + H 2 O and 2 C 2 H 5 I + PH 4 I + ZnO = (C 2 H 5 ) 2 PH.HI + ZnL + H 2 O \J2 A Iky I Phosphorus and Arsenic Compounds Both substances form compounds with the zinc iodide. The mixture of substances is treated with water in presence of hydrogen. The water decomposes the salt of the primary base into the free base and HI C^PH^HI + *H 2 = C 2 H 5 PH 2 + HI + *H 2 O The ethyl phosphine is condensed by a freezing mixture. Properties. It is a strongly refractive liquid, b.p. 25, has an overpowering odour and a bitter taste. It is readily inflam- mable, ignites with Cl, Br, or HNO 3 , and in the latter case forms ethane phosphonic acid, C 2 H 5 PO(OH) 2 (ethyl phosphinic acid}. It is a weak base, and unites with hydracids to form salts. Di-ethyl Phosphine, (C 2 H 5 ) 2 PH, is left in the residue from the previous operation, and is separated from it by the addition of caustic soda. The base then distils over, and is condensed in an atmosphere of hydrogen. Properties. It is a colourless, refractive liquid, with a pene- trating smell, b.p. 85, and is inflammable in air. It forms salts with acids. Tri-ethyl Phosphine, (C 2 H 5 ) 3 P. When PH 4 I is heated with alcohol, the following reaction occurs : PHJ + C 3 H B OH = PH 8 + C 2 H 5 I + H 2 O but if the reaction takes place under pressure, the interaction of the PH 3 and C 2 H 5 I produces a mixture of (C 2 H 5 ) 3 P.HI and tetra-ethyl phosphonium iodide (C 2 H g ) 4 PI (compare formation of Amines, p. 164). Similarly, if PHJ and C 2 H 5 I are heated together, the mixture is obtained, but the primary and secondary phosphines are absent PHJ + 3 C 2 HJ = (C 2 H 5 ) 3 P.HI + 3 HI (C 2 H 5 ) 3 P.HI + C 2 H 5 I = (C 2 H 5 ) 4 PI + HI Caustic soda frees the tertiary compound (compare the Amines) from the mixture. Tri-ethyl phosphine is also con- veniently produced by the action of zinc methyl on PC1 3 : 2PC1 3 + 3 (C 2 H 5 ) 2 Zn = 2(C 2 H 5 ) 3 P -4- 3 ZnCl 3 Properties. It is a colourless, mobile liquid, b.p. 128, Phosphonium Compounds. Ar sines 173 with a suffocating odour, which, diluted, smells like hyacinths. It is insoluble in water, soluble in alcohol and ether. It absorbs oxygen from the air very rapidly, becoming acid, although it is neutral when pure, and forms tri-ethyl phosphine oxide, (C 2 H 5 ) 3 PO ; with sulphur it forms the beautifully crystal- line sulphide, (C 2 H 5 ) 3 PS ; and with CS 2 it forms characteristic red crystals of (C 2 H 5 ) 3 P.CS 2 . Its salts are crystalline, but deliquescent. The phosphines (with the exception of methyl phosphine, which is a gas) are colourless, refractive, volatile liquids with an unpleasant smell. They are little soluble in water, and are readily oxidised on exposure to air. Just as PH 3 is not so strong a base as NH 3 , so the phosphines are not so basic as the amines ; but as the introduction of alkyl groups increases the basicity of NH 3 , so it does that of PH 3 . Thus phospho- nium iodide and the salts of primary phosphines are decomposed by water, but the salts of the secondary and tertiary phosphines require the use of an alkali (see Phosphines above). PHOSPHONIUM COMPOUNDS. Tri-ethyl phosphine combines with C 2 H 5 I to form tetra- ethyl phosphonium iodide, exactly as tri-ethylamine forms tetra-ethyl ammonium iodide. It is also formed when PH 4 I acts on C 2 H 5 I. When it is digested with water and freshly precipi- tated Ag 2 O, the iodine is replaced by hydroxyl, and tetra- ethyl phosphonium hydroxide is formed ; when this solution is dried over concentrated H 2 SO 4 , a bitter alkaline deliquescent crystalline mass remains, which absorbs CO 2 and behaves towards metallic solutions very much like caustic potash, but does not dissolve the oxides of zinc and aluminium so readily. COMPOUNDS OF ARSENIC] ARSINES. Arsenic unites with alkyl radicles to form compounds which have many analogies to those produced from nitrogen, but apparently bodies analogous to primary and secondary amines cannot exist. The arsenic compounds may be best looked upon as 174 A Iky I Phosphorus and Arsenic Compounds derived from arsenic tri-chloride by the replacement of one, two, or three atoms of chlorine by alkyl radicles. The groups AsCH 3 and As(CH 3 ) 2 thus formed act as basic di- and mono-valent compound radicles respectively. AsCl 3 yields As^ 3 , As 2 , and As(CH 3 ) Arsenic Methylarsine Dimethyl- Trimethyl- tri- chloride di-chloride arsine chloride arsine These compounds can unite with a molecule of chlorine to form bodies in which the arsenic is penta-valent, and that decompose on heating with the loss of CH 3 C1 ; e.g. As(CH 3 ) 8 C) 2 = CH 3 C1 + As(CH 3 ) 2 Cl Bodies analogous to the ammonium derivatives are also known. The methyl arsenic compounds will be taken as types, and it is convenient to reverse our general order of study- ing these substances, and take the tertiary derivatives first TERTIARY ARSINES. Trimethylarsine, As(CH 3 ) 3 , is formed (i) when arsenic tn-chloride is heated with zinc methyl (compare formation of Tri-alkyl phosphines from PC1 3 ) 2 AsCl 3 + 3Zn(CH 3 ) 2 - 2As(CH 3 ) 3 + 3ZnCL or (2) by heating sodium arsenide with methyl iodide to 180 AsNa 3 + 3 CH 3 I = As(CH 3 ) 3 + 3 NaI Also from tetra-methyl arsonium iodide (q.v.) by heating with KOH (difference from amines and phosphines). Properties. It is a disagreeable-smelling, refractive liquid, boiling below 100, insoluble in water. It absorbs oxygen from the air, forming a crystalline oxide (see Tertiary phosphines). It does not unite with acids to form salts, thus differing from amines and phosphines; but, like them, it forms quaternary compounds with alkyl iodides. DlMETHYLARSINE (CACODYL) DERIVATIVES* It has been pointed out above that the group As(CH 3 ) 2 appears to act as a mono-valent compound radicle, which occurs Cacodyl Derivatives 175 As(CH 3 ) 2 as tetra-methyl di-arsine or cacodyl 1 | . The As(CH 3 ) 2 starting-point for the formation of cacodyl itself and its deriva- tives is alcarsin, an impure form of cacodyl oxide, obtained by heating arsenic tri-oxide with an equal weight of dry potas- sium acetate, condensing the vapours, and collecting the oily distillate under water, because it is spontaneously inflammable owing to the presence of free cacodyl. AsoO 3 + 4CH 3 .COOK = [As(CH 3 ) 2 ] 2 O -f 2K 2 CO 3 + 2CO, Other poisonous gases are evolved, and the operation must be conducted in a good draught. When the crude distillate is distilled with several times its weight of mercuric chloride and hydrochloric acid, cacodyl chloride is obtained, from which its other compounds can be obtained in a pure state. Cacodyl Chloride, As(CH 3 ) 2 Cl, dimethylarsine chloride, is obtained as just described, or by heating trimethylarsine di-chloride (CH 3 ) 3 AsCl 2 = (CH 3 ) 2 AsCl + CH 3 C1 Properties. It is a colourless, heavy oil, boiling near 100, which does not fume in air, although its vapour ignites spon- taneously. Its smell is stupefying, and its vapour attacks the mucous membrane most violently. It unites with PtCl 4 to form a compound, 2As(CH 3 ) 2 Cl.PtCl 4 , forms double salts with other metallic chlorides, and combines with a molecule of chlorine to form cacodyl trj-chloride, As(CH 3 ) 2 Cl 3 , which decomposes at 40, and forms As(CH 3 )Cl 2 .and CH 3 C1. Cacodyl Oxide, [As(CH 3 ) 2 ] 2 O, tetra-methyldiarsine oxide, is found in an impure condition in alcarsin, and is obtained pure by distilling the chloride with potash 2As(CH 3 ) 2 Cl + 2KOH = [As(CH 3 ) 2 ] 2 O + 2KC1 + H 2 O Properties. -It is a heavy oil, boiling about 150, and solidi- fying at 25. It has a frightful odour, attacks the mucous membrane, and produces insensibility. It is insoluble in 1 From KaKuSris, stinking, because of the disgusting odour it and its derivatives possess. 176 Alky I Phosphorus and Arsenic Compounds water, but readily soluble in alcohol or ether ; it is a weak base, but unites readily with acids to form salts. Oxidation produces cacodylic acid (q.v.). Besides the above, other salts of cacodyl are cacodyl cyanide, As(CH 3 ) 2 CN, a crystalline solid formed from the chloride by treatment with Hg(CN) 2 ; and cacodyl sulphide, [As(CH 3 ) 2 ] 2 S, an oily inflammable liquid, obtained when the chloride is distilled with Ba(SH) 2 . As(CH 3 ) 2 The free base cacodyl, , tetra-methyl diarsine, As(CH 3 ) 2 is readily formed from the chloride by heating it with zinc filings to 90-100 in a current of CO 2 2 As(CH 3 ) 2 Cl + Zn = [As(CH 3 ) 2 ] 2 + ZnCL The preparation is difficult, owing to the great inflammability of the compound. Properties. Cacodyl is a spontaneously inflammable, colour- less, mobile liquid, b.p. about 170, and solidifying at 6. It has a frightful odour, which induces vomiting. It combines with chlorine to form the chloride, and with sulphur to form the sulphide, and with nitric acid it produces the nitrate; in fact, it acts in many ways like an element. Cacodylic Acid, As(CH 3 ) 2 O.OH, di-methyl arsinic acid, is produced when cacodyl oxide is oxidised in the air or by mercuric oxide and water [As(CH 3 )J 2 O + 2HgO + H 2 = 2As(CH 8 ) a O.OH + 2 Hg It crystallises in prisms, which are deliquescent and easily soluble in water, insoluble in ether. It is not acted upon by nitric acid or by aqua regia ; it forms salts with metallic oxides, which are difficultly crystallisable. METHYLARSINE COMPOUNDS. Methylarsine Di-chloride, AsCH 3 Cl 2 , is formed by the decomposition of cacodyl tri-chloride As(CH 3 ) 2 Cl 3 by heat (p. 174), and by heating cacodylic acid in gaseous hydrochloric acid As(CH 3 ) 2 O.OH + 3 HC1 = AsCH 3 Cl 2 + CH 3 C1 + 2H a O Silicon, Zinc, and Mercury A Iky Is 177 Properties. It is a heavy, mobile liquid, b.p. 133, does not fume in air, and is not decomposed by water. Its vapour attacks the mucous membrane most violently. It unites directly with chlorine to form As(CH 3 )Cl 4 . Treated with aqueous potassium carbonate, methylarsine oxide, AsCH 3 O, is formed, a solid soluble in water, and smelling like asafcetida. When moist silver oxide acts on the dichloride in presence of water, or mercuric oxide acts on the oxide, methyl arsinic acid (methane arsonic acid), CH 3 AsO(OH) 2 , is produced. ARSONIUM COMPOUNDS. Tetra-methyl Arsonium Iodide, (CH 3 ) 4 AsI, results (i) from the direct addition of methyl iodide to tri-methyl arsine ; and (2) is the main product of the action of AsNa 3 upon CH 3 I, and remains behind when the other products are distilled off. It is a white crystalline solid, which, on treat- ment with moist silver oxide, yields Tetra-methyl Arsonium Hydroxide, (CH 3 ) 4 AsOH, which is a strongly alkaline deliquescent substance that forms salts with acids, and liberates ammonia from its salts. CHAPTER XXIII. COMPOUNDS OF SILICON, ZINC, AND MERCURY, WITH ALKYL RADICLES. COMPOUNDS OF SILICON. THE element silicon has already been foun'd, in the study of inorganic chemistry, to yield many compounds which are the analogues of those given by carbon, and although our know- ledge is still very imperfect, much has been done which shows that this analogy is very marked in its organic derivatives. Thus it forms compounds which are similar to hydrocarbons, alcohols, etc. Amongst these may be noted Silicon Methyl, Si(CH 3 ) 4 , silicon tetra-methide, tetra-methyl- silicane, and Silicon Ethyl, Si(C 2 H 5 ) 4 , silicon tetra-ethide, tetra- ethyl-silicane. These bodies, which are analogous to the N 178 Silicon, Zinc, and Mercury A Iky Is hydrocarbons, tetra- methyl-methane, and tetra-ethyl-methane, can be formed by heating silicon tetra-chloride respectively with zinc methyl or zinc ethyl SiCl 4 -f 2Zn(CH 3 ) 2 = Si(CH 3 ) 4 + 2 ZnCl 2 Silicon methyl is a mobile, inflammable oil, which boils at 31 ; and it is not acted upon by water, KOH, or HNO 3 . Silicon ethyl is an oil similar to the last named, sp. gr. 0^834, boiling at 153. Chlorine acts upon it with the forma- tion of a mono-chlor-substitution product, silico-nonyl chloride, (C. 2 H 5 ) 3 Si.C 2 H 4 Cl ; this, in its turn, by alternate treatment with alcoholic potassium acetate and alcoholic potash, yields first (C* TT ^ an acetate, Si' an< ^ t * ien t ^ ie so ~ ca ^ e( ^ silico- //- TT \ nonyl alcohol, Si^, ^ Q 3 ^, an oily liquid, which boils at 190. A number of other compounds are known which resemble alcohols or ethers, of these may be mentioned ethyl C* H silicon tri-ethylate, Si/<4 ^ QH) ' a lic l uid wnicn yields, by successive treatment with acetyl chloride and water, ethyl C* TT silicon tri-chloride, Si B , and ethyl silicic acid (silico propionic acid), C 2 H 5 SiOOH, which is spontaneously in- flammable, and forms salts with bases. METALLO-ORGANIC COMPOUNDS. The alcoholic or alkyl radicles form compounds by direct union with many of the metals, the most important of which are those with sodium, zinc, and mercury. Not only do they form saturated compounds, but many metals yield derivatives in which their atomicity is only in part satisfied by the alkyl groups, such a metallic group, if monad, forming a compound radicle which cannot be isolated, but which can combine with such groups as Cl or OH. The hydroxides thus produced are strongly basic, owing to the positive character of the alkyl groups. We may conveniently study first a zinc alkyl. Zinc Ethyl 179 Zinc Ethyl, Zn(C 2 H g ) 2 , zinc ethide, was first obtained by the action of zinc upon ethyl iodide. The reaction occurs in two stages : when heated to 90 2C 2 H 5 I + Zn 2 = 2 C 2 H 5 ZnI and this compound, heated to 160, gives 2 C 2 H 5 ZnI = (C 2 H 5 ) 2 Zn + ZnI 2 This reaction, modified by working details, is usually employed tor its production, use being made of zinc filings or the zinc- copper couple. ^Process. Heat 36 grams of zinc filings in a dry flask with 4 grams of copper (prepared by reducing CuO in hydrogen at a low temperature) till the zinc becomes round and yellow, then shake strongly. When cool it should be a dark metallic powder. FIG. 43. Connect the flask with a reflux condenser provided with a mercury trap, as Fig. 43. Next pass perfectly dry CO 2 through the apparatus, and add 34-8 grams of ethyl iodide. Heat the whole to 90 till no more iodide distils back unchanged. Then cool the flask, and transfer it to the upper end of the condenser ; distil the zinc ethyl off from an oil-bath at 160, and collect in vessels full of CO a and separated by mercury traps from the air. 180 Silicon, Zinc, and Mercury Alkyls Caution. Great care must be taken not to expose it to the air, because it is spontaneously inflammable. Properties. Zinc ethyl is a colourless, highly refractive, mobile liquid, with a peculiar odour, b.p. 118, sp. gr. 1-182 at 1 8. When exposed to air it ignites at once, and burns with a luminous green-tinged flame, clouds of zinc oxide being formed, and consequently it must be handled carefully in an atmosphere of carbon dioxide. When oxygen is allowed to act* C* H slowly on zinc ethyl, zinc-ethyl ethylate, (Aj'o^^Bf an( * tnen zinc ethylate, (C 2 H 5 O) 2 Zn, are formed in succession. When added to water, zinc ethyl yields ethane and Zn(OH) 2 ; with alcohol, zinc ethylate and Zn(OH) 2 . The halogens react violently on it, forming haloid esters. It reacts with alkyl-iodides to form hydrocarbons (C 2 H 5 ) 2 Zn + 2C 2 H 5 I = 2C 2 H 5 .C 2 H 5 + ZnI 2 In consequence of its great chemical activity, it finds employment in many syntheses. Thus it reacts with substances which contain hydroxyl and halogen radicles, forming, e.g., hydrocarbons (p. 43), ketones (p. 135), phosphines (p. 172), arsines, etc., and it is quite typical of the zinc alkyls. Zinc Methyl is a mobile, disagreeable-smelling liquid, b.p. 46. It is prepared similarly to the ethyl compound, and is frequently employed in synthetical work. Sodium and Potassium Ethyl. When sodium is added to zinc ethyl, zinc separates out, and there remains a liquid which contains a double compound of zinc and sodium ethyl, NaC 2 H 5 -f Zn(C 2 H 5 ) 2 , from which the sodium compound has not yet been freed. Potassium acts similarly. These compounds are even more reactive than the zinc alkyls, and absorb CO 2 , forming propionates C 2 H 5 Na + CO 2 = C 2 H 5 COONa while CO forms a ketone. Mercury Ethyl, Hg(C. 2 H 5 ) 2 , mercury ethide, was first prepared by decomposing mercuric chloride by zinc ethyl, but Acid Amides and Amido-acids 181 is best obtained by the action of sodium amalgam (o'2 per cent. Na) upon ethyl iodide in presence of acetic ether Hg + Na 2 + 2C 2 H 5 I = Hg(C 2 H 5 ) 2 + 2 NaI The excess of the reagents is distilled off, water added, and the separated oil dried over CaCl 2 , and then rectified. Properties. Mercuric ethyl is a very poisonous , colourless, heavy liquid, with a faint ethereal odour, b.p. 159, sp. gr. 2 -46. It is not acted upon by water, in which it is insoluble, and does not ignite in air till heated, but takes fire in chlorine. C 1 1-T Mercury ethyl yields chlor-mercuric ethyl, Hg^ ? ^ when treated with alcoholic mercuric chloride ; and the chlor- ethide gives, with moist silver oxide, hydroxy-mercuric C* H ethyl, Hg^r 2 5 , which is a strongly alkaline substance form- ing salts with acids. Many other salts can be formed, in which the group Hg. C 2 H 5 ' plays the part of a compound radicle. Mercury ethyl finds employment in certain synthetical work. Mercury methyl is a liquid, b.p. 95, sp. gr. 3-069, and still more poisonous than the ethyl compound. REMARKS ON THE METALLIC DERIVATIVES. Three typical methods of formation have been illustrated : (i) The action of a metal upon an alkyl haloid (see Zinc ethyl) ; (2) of a metal upon a metallic alkyl (see Sodium ethyl) ; and (3) of a metallic salt upon a metallic alkyl (see Mercuric ethyl). CHAPTER XXIV. ACID AMIDES AND AMIDO-ACIDS. ACID AMIDES. HITHERTO the compounds of nitrogen which have been under consideration have contained the amidogen group linked to an alkyl radicle ; that is, they have been derived from alcohols by the replacement of the hydroxyl group by NH 2 . 1 82 Acid Amides and Amido- Acids We must now consider a class of compounds derived from acids in a similar manner, and hence known as acid amides. Thus C 2 H 5 OH yields C 2 H 5 NH 2 , and CH 3 .COOH yields CH 3 .CONH 2 . These substances, unlike alkylamines, are neutral to litmus, although they are sufficiently basic in their properties to form compounds with acids. The first of the series is that derived from formic acid, Formamide, H.CONH 2 , which was first obtained by heating ethyl formate with ammonia in sealed tubes to 100 C, and is a colourless liquid, boiling at 192-! 95. A better substance to study in detail is Acet amide, CH 3 .CONH 2 , which was first prepared (*i) by heating ethyl acetate to 120 with strong aqueous ammonia CH 3 .CO.OC 2 H 5 + NH 3 - CH 3 .CONH 2 + C 2 H 5 OH (*2) When ammonium acetate is distilled in a current of dry ammonia, or, more conveniently, heated in closed tubes to 230, and then distilled, acetamide is produced CH 3 .CO.ONH 4 = CH 3 .CONH 2 + H 2 O ^Process. Heat 100 grams of ammonium acetate in well-sealed glass tubes for 6 hours to 230. (The acetate may be prepared by passing dry NH 3 into glacial acetic acid till it is saturated.) At the end of that time carefully open the tube and distil the contents, collecting all above 180 separately. On standing, crystals of aceta- mide separate, which can be drained, and, on distillation, will yield nearly pure acetamide. It is also formed (*3) when ammonia acts on acetyl chloride CH 3 .COC1 + 2NH 3 = CH 3 .CONH 2 + NH 4 C1 This last method clearly indicates its constitution. Properties. Acetamide is a white, crystalline, deliquescent solid, sp. gr. 1*159, m.p. 83, b.p. 222 (cor.), and it may be heated to nearly 360 without decomposition. It ordinarily possesses a strong smell of mice ; if pure is probably odourless. It is soluble in water or alcohol, but insoluble in pure ether. If heated with water, acids, or with aqueous solutions of alkalis, acetamide is resolved into acetic acid and ammonia CH 3 .CONH a + HOH - CH 3 .COOH + NH 3 Acid Amides. Glycine 183 Nitrous acid also forms the free acid by a similar reaction to that which occurs when it acts on an amine (see p. 168) CH 3 .CONH 2 + HONO = CH 3 .COOH -f N 2 -f H 2 O When distilled with P 2 O 5 or ZnCl 2 acetamide yields aceto- nitrile (see p. 193); while PC1 5 reacts with it, replacing the oxygen atom, and halogens replace one of the hydrogen atoms in the NH 2 group. It is a weak base, and combines directly with the stronger acids ; thus gaseous HC1 passed into a solution of it in alcohol-ether forms the compound CH 3 .CONH 2 .HC1. On the other hand, it is also slightly acid in character, and can form metallic compounds, of which C 2 H 3 ONHAg is an example. GENERAL REMARKS ON THE ACID AMIDES. Acid amides can be formed (i) by the action of NH 3 on esters, (2) by dehydration of the ammonium salts of acids, and (3) by acting on acid chlorides with NH 3 . These methods have been illustrated by the formation of acetamide. It can also be produced (4) by the action of ammonia on acid anhydrides. Properties. The acid amides are generally solid crystalline substances soluble in alcohol and in ether; the lower members of the series are soluble in water. They act as feebly basic compounds, although neutral to litmus. The amide hydrogen is replaceable by metals, and also by acid groups, such as acetyl, C 2 H 3 O', and by the halogens. (For the reactions which they undergo with water, acids, alkalis, nitrous acid, P 2 O 5 , and PC1 5 , see Acetamide.) Constitution. The constitution of these amides may be deduced from their formation by method 3, and the reactions they undergo with water, the alkalis, and nitrous acid. AMIDO-ACIDS. Glycocoll or Glycine, CH 2 NH 2 .COOH, amido-acetic acid. This acid is the first representative of, and serves to illustrate, a series of substances which, though neutral in reaction, possess both acid and basic properties. It may 184 Acid Amides and Amido-Acids be viewed as derived from an alcoholic acid, C FLO H. CO OH, by the replacement of the alcoholic OH by NH 2 ; but it is simpler to consider it as an amido-substitution derivative of the acid to which it is related : its formation by method (3) supports the latter view. Glycocoll (yAvKu's, " sweet"; KoXXa, "glue") is obtained (i) as a decomposition product of glue when boiled with dilute H 2 SO 4 or KOH ; and (2) it is conveniently prepared from hippuric acid, which is found in the urine of horses, by boiling it with HC1 or H 2 SO 4 CH 2 NH(C 6 H 5 CO).COOH + H 2 O = CH 2 NH 2 .COOH Hippuric acid Glycocoll + C 6 H 5 COOH Benzoic acid Process. Boil hippuric acid with four parts of strong HC1 for an hour or two. Cool the solution, filter from benzoic acid, and separate the remainder of that substance by extraction with ether. Evaporate the residual liquid to the crystallising point, when glycocoll hydrochloride is obtained. If this is decomposed by either lead or silver oxide, the glycocoll is obtained free. Glycocoll is synthetically produced (*$) by heating chlor- acetic acid with ammonia (compare Formation of amines) CH 2 C1.COOH + NH 3 = CH 2 NH 2 .COOH + HC1 and (4) by passing cyanogen into boiling concentrated solution of hydriodic acid CN.CN + 5HI + 2H 2 = CH 2 NH 2 COOH + NH 4 I + 2 I 2 Properties. Glycocoll crystallises in colourless monoclinic tablets, which melt with decomposition at 2$o-2$6. It is soluble in water, insoluble in absolute alcohol and in ether, and has a sweet taste. It contains the groups NH 2 and COOH, and can form compounds with both acids and bases ; it is neutral to litmus, and is probably itself a salt formed by one molecule neutralising another, thus CH 2 NH 2 HOOC CH 2 (NH 3 ).OOC I + I - I I COOH H 2 NH 2 C COO(NH 3 ).H 2 C This formula is supported by the fact that it forms two Glycine. Leucine 185 compounds with hydrochloric acid. Nitrous acid converts it into gly collie acid (^.z>.)> an d when heated with BaO it yields methylamine and BaCO 3 . KOH acts similarly. Solutions of glycocoll give, with ferric chloride, a deep red colour, which acids discharge and ammonia restores. Glycocoll prevents the precipitation of copper salts by KOH. Its metallic salts are probably formed by metals replacing hydrogen in the amidogen group. Alanine, amido-propionic add, and the amido-butyric acids, do not call for any special remark ; but Leucine, CH 3 .(CH 2 ) 3 .CH(NH 2 ).COOH, or a-amtdo- caproic acid, found in many animal juices, may be mentioned. It occurs in the liver during disease, and in the brain and the pancreas; also in old cheese, and is found during the decay of albumenoids. It crystallises in leaflets, m.p. 170. It is slightly soluble in water, insoluble in ether, and laevo- rotatory in its action on polarised light. SECTION III. CYANOGEN AND CARBONIC ACID DERIVATIVES. CHAPTER XXV. CYANOGEN AND ITS DERIVATIVES. CYANOGEN is the name given to the compound radicle (CN), which, however, does not exist in the free condition, but only as the gas cyanogen, better termed di-cyanogen, CN.CN. This may be looked upon as a derivative of a hydrocarbon, but it is not usual to do so. It is convenient, therefore, to study the compounds apart, and it will be noticed that the CN group combines with metallic and organic radicles in a manner somewhat analogous to that in which the halogens combine. In fact, the student will remember many reactions already mentioned in which it has displaced one of those elements. The group CN is often written Cy. SYNTHESES OF CYANOGEN DERIVATIVES. The following synthetical processes are especially interest- ing in illustrating the combination of carbon with nitrogen. 1. Carbon and nitrogen do not combine together very readily alone, although cyanogen is formed when electric sparks are passed between carbon poles in an atmosphere of nitrogen C 2 + N 2 = C 2 N 2 2. Although the combination between the two elements occurs so difficultly alone, if nitrogen is passed over a heated Cyanogen 1 87 mixture of potassium carbonate, or barium oxide, and carbon, cyanide of potassium or barium is formed 4 C + N 2 + K 2 C0 3 = 2KCN + 3 CO 3 C + N 2 + BaO = Ba(CN) 2 + CO The production on a large scale of potassium ferrocyanide by heating nitrogenous organic matter with alkalis and iron is an analogous case. 3. Also if ammonia is passed over red-hot charcoal, ammonium cyanide is produced C + 2NH 3 = (NH 4 )CN + H 8 4. Again, cyanogen itself is produced when ammonia and coal-gas are burned together in a Bunsen burner 2 CO + 2NH 3 + O = C 2 N 2 + sH 2 O These examples will suffice to illustrate the synthetical formation of cyanogen compounds from inorganic sources, and the following bodies or classes of compounds will now be studied in order : Cyanogen or di-cyanogen, CN.CN. Hydrocyanic acid, HCN. Metallic cyanides ; e.g. potassium cyanide, potassium ferro- cyanide. Esters of hydrocyanic acid; e.g. CH 3 CN. Cyanic acid and cyanates, HOCN. Cyanogen chloride, Cl.CN. Cyanuric acid and cyanurates, H 3 O 3 (CN) 3 . Cyanogen (/cv'ai/os, "blue"), CN.CN, is usually obtained (i) by the decomposition of cyanides. Thus, cm heating mercuric cyanide it is formed along with the polymeric black solid paracyanogen Hg(CN) 2 = C 2 N 2 + Hg It may also be conveniently obtained from copper cyanide as described below. Process. Heat a concentrated aqueous solution of KCN with 2 parts CuSO 4 .5H 2 O, dissolved in 4 parts of water, and collect the gas over mercury. Remember the gas is very poisonous. (2) Cyanogen is a product of the combustion of ammonia 1 88 Cyanogen and its Derivatives with coal-gas (p. 187), and occurs in the gases from coke ovens. (3) Of special synthetic importance is its formation from its elements by the action of electricity (p. 186) ; and (4) also its production when ammonium oxalate or oxamide is heated with dehydrating agents, e.g. P 2 O 5 C 2 4 (NH 4 ) 2 = C 2 N 2 + 4 H 2 O Ammonium oxalate Properties. Cyanogen is a colourless gas with a peculiar odour, and is very poisonous. It burns with a violet flame ; cold and pressure condense it to a liquid, b.p. 207, and a lower temperature produces a solid, m.p. 34 -4. It is slightly soluble in water, more so in alcohol. Aqueous solutions decompose on standing, with the production of brown azulmic acid, ammonium oxalate, and other bodies. Potash forms the cyanide and the cyanate, but if a little aldehyde is present in the aqueous solution, oxamide only is formed CONHo C 2 N, + 2H 2 O = I CONH 2 These reactions, coupled with its formation from ammonium oxalate, show it to be the nitrile of oxalic acid. HYDROCYANIC ACID AND THE CYANIDES. Hydrocyanic Acid, HCN, pnissic add, occurs in to- bacco smoke, and is found in many plants ; e.g. it is present in bitter almonds, cherry-stones, etc. These bodies contain a substance called amygdalin, which is decomposed if they are macerated in water, and on distillation hydrocyanic acid is found in the distillate. It is obtained synthetically (i) by the direct union of cyanogen and hydrogen induced by the silent electric dis- charge H 2 + C 2 N 2 = 2HCN also (2) when electric sparks are passed through a mixture of acetylene and nitrogen C 2 H 2 + No = 2HCN Hydrocyanic Acid 189 and (3) by rapidly heating ammonium formate with P s O g H.COONH 4 - HCN + 2 H 2 O In the last reaction it appears as the nitrile of formic acid. It is usually obtained by decomposing cyanides by acids (for synthetical formation of cyanides, see p. 186), and as it is exceedingly poisonous great care must be exercised in its preparation 2 K 4 FeC 6 N 6 + 3H 2 S0 4 = sK 2 SO 4 + Fe 2 K 2 C 6 N 6 + 6HCN Potassium ferrocyanide KCN + C 4 H 6 O 6 = HCN + KHC 4 H 4 O 6 Tartaric acid Processes. Distil a mixture of 14 parts water, 7 parts cone. H 2 SO 4 , and 10 parts coarsely powdered potassium ferrocyanide in a capacious flask connected with a condenser and receiver, and collect the gas in distilled water. If required anhydrous, the gas is passed through an inverted condenser, dried over calcium chloride (both the condenser and vessels containing CaCl 2 being kept at 30), and collected in a receiver surrounded by ice and salt. To obtain an acid of known strength, shake together 9 parts tartaric acid, 60 parts water, and 4 parts KCN. Allow the acid tartrate of potassium to separate, and pour off the liquid, which then contains 3'6 per cent, of HCN. Properties. Pure hydrocyanic acid is a colourless, mobile liquid, b.p. 26-5, sp. gr. 07058 at 7. It has a peculiar smell resembling that of oil of bitter almonds. It is intensely poisonous ; one drop of the anhydrous acid is an instantly fatal dose, and minute quantities of the vapour are sufficient to kill when inhaled. The acid is readily inflammable ; it is unstable, especially in aqueous solutions, but a trace of a mineral acid renders it more stable. When heated with concentrated mineral acids, or with alkalis it yields formic acid and ammonia (compare Cyanogen) HCN + 2 H 2 O - H.COOH + NH 3 It is reduced by nascent hydrogen to methylamine. It is only a very feeble acid, but yields a series of salts with the metals, acting like a haloid acid, and gives a white precipitate with silver salts. 190 Cyanogen and its Derivatives Identification. Hydrocyanic acid gives a blue colour, due to Prussian blue, when the solution is first made alkaline with NaOH, then a solution of FeSO 4 and FeCl 3 added, and finally HC1. The following is a more delicate test : add a few drops of yellow ammonium sulphide to the liquid containing the acid, evaporate to dryness, add a few drops of water and a drop of solution of FeCl 3 ; a deep red colour, due to ferric thiocyanate, is produced. Constitution. It is possible to write the constitutional formula of hydrocyanic acid in two ways, viz. H.C-N and as HNjC; which of these formulae is correct cannot be determined, though probably the former is nearer the truth. One of the cyanides, however, silver cyanide, appears to be differently constituted from the others, as in certain reactions it behaves as if it were best represented by the formula Ag.NC, in which the silver is united to the nitrogen ; but there are no series of salts corresponding to the two forms of acid. The alkyl derivatives or esters, however, show marked differences : there are two series of them, apparently derived from HCN and HNC respectively. Those derived from HCN are termed cyanides or nitriles, while the others are called iso- cyanides or carbamines. Simple Cyanides. The cyanides of the alkalis and alkaline earths are readily soluble in water. Cyanides of the other metals, mercuric cyanide excepted, are insoluble ; many of them, however, dissolve in solutions of alkaline cyanides, forming soluble double cyanides. The principal cyanides are mentioned below. Potassium Cyanide, KCN, is found in blast furnaces, and its production from K 2 CO 3 , nitrogen, and carbon has been mentioned (p. 187). It is also formed when potassium is heated in cyanogen. When required quite pure, potassium cyanide is prepared by passing anhydrous HCN into strong KOH, when it is precipitated, and can be collected, washed with alcohol, and dried. It is usually formed by heating potassium ferrocyanide with K 2 CO 3 in a crucible 2K 4 Fe(CN) 6 + 2K 2 CO 3 = loKCN + 2 KCNO Cyanides 191 So prepared, as indicated by the equation, it always contains cyanate. It can also be prepared in an almost pure state by igniting potassium ferrocyanide alone, and filtering the melted product through hot porous crucibles, so as to separate the carbide of iron K 4 FeCy 6 = 4 KCN + N 2 + FeC Potassium cyanide is a white deliquescent solid, which crystallises in cubes and fuses at a red heat. It is very soluble in water, and is readily decomposed by acids, even by CO 2 . It is very poisonous, is a powerful reducing agent, being readily oxidised to potassium cyanate, and forms double cyanides with other metals. Silver Cyanide, AgCN, is prepared as a white curdy solid by adding potassium cyanide to solutions of silver salts. It may be dried at 100, and does not blacken on exposure to light, is little soluble in HNO 3 , but readily in KCN, forming AgCN.KCN, also in NH 4 HO (compare AgCl). Mercuric Cyanide, Hg(CN) 2 , is prepared by boiling Prussian blue with HgO and water, or by dissolving HgO in the acid. It is readily soluble in water, but not in absolute alcohol. Is decomposed on heating, yielding cyanogen. It forms many double compounds with cyanides and other salts. Compound Cyanides. Many of the insoluble cyanides form, with those of the alkali and other metals, soluble double cyanides. Those with the alkali metals are decomposed by mineral acids, with precipitation of the insoluble cyanides and liberation of HCN. Some of the cyanides, however, appear to enter into more intimate combination, so that on acidification a new acid is liberated, and not HCN. Of this class the ferrocyanides and ferricyanides are noteworthy examples. Potassium Ferrocyanide, K 4 FeCy 6 .3H 2 O, yellow prus- siate of potash. It is well known that when nitrogenous organic matter is fused with potashes, KCN is formed. It is practically impossible to purify this complex product so as to obtain the cyanide direct ; but if along with this mixture iron is introduced, on lixiviating the fused mass 192 Cyanogen and its Derivatives crystals of potassium ferrocyanide separate and can be re- crystallised. The reaction which occurs is complex, but it may perhaps be represented thus 6KCN + FeS = K 4 Fe(CN) 6 + K 2 S or, as potassium, thiocyanate is always formed, thus i 3 KCN + Fe 2 S 3 = 2K 4 Fe(CN) 6 + 2 K 2 S + KSCN The sulphur comes both from the organic matter, and from the reduction of K 2 SO 4 present in the carbonate. Manufacture. The above reaction is realised by heating, on the iron hearth of a reverbatory furnace, iron and K 2 CO 3 , and when fusion has occurred, introducing animal matter, e.g. horn, blood, wool, or leather, along with more K 2 CO 3 . When the fusion is complete, the melt is ladled out and cooled. The " metal " is then extracted with water, and the solution allowed to crystallise. Properties. Potassium ferrocyanide forms lemon-coloured quadratic pyramids which lose their water at 6o-8o. It has a sweet saline taste, and is not poisonous. Its solution decomposes when exposed to sunlight, liberating HCN and precipitating " Prussian blue." When ignited it yields KCy, carbide of iron, and nitrogen, and when heated with cone. H 2 SO 4 , gives carbon monoxide K 4 Fe(CN) 6 + 6H 2 + 6H 2 SO 4 = 6CO + 2K 2 SO 4 + FeSO 4 ^ + 3(NH 4 ) 2 S0 4 When a solution t>f potassium ferrocyanide is poured into excess of ferric chloride, a blue precipitate is formed called Prussian blue, which is ferric ferrocyanide 4 FeCl 3 + 3K 4 (FeCy 6 ) = Fe 4 (FeCy 6 ) 3 + "KCl When washed and dried this forms a dark blue amorphous powder, insoluble in water, soluble in oxalic acid. Potassium Ferrieyanide, K 3 FeCy 6 red prussiate of potash, is formed when the ferrocyanide is treated with oxidising agents, e.g. chlorine or PbO 2 2 K 4 FeCy 6 + CI 2 = 2K 3 FeCy 6 + 2KC1 The chlorine is well washed and passed in till the solution no Alky I Cyanides. Aceto-nitrile 193 longer yields a blue colour with ferric salts. Excess of the gas must be avoided, or Prussian green is precipitated. Properties. It forms large red crystals, soluble in water and nearly insoluble in alcohol. It is used as an oxidising agent, especially in alkaline solutions, becoming reduced to ferrocyanide, and finds employment in quantitative analysis on that account. When a solution of potassium ferricyanide is added to excess of a ferrous solution, a blue precipitate is obtained of ferrous ferricyanide, or Turnbull's blue, Fe 3 (FeCy) 2 . When dry it is a deep blue powder, insoluble in water and alcohol, and soluble in oxalic acid. ESTERS OF HYDROCYANIC ACID, OR NITRILES. Hydrogen cyanide or formo-nitrile, H.CN Methyl aceto-nitrile, CH 3 .CN Ethyl propio-nitrile, C 2 H g .CN, etc. It has been already pointed out that, by its formation from ammonium formate (p. 189) and decomposition with dilute alkalis (p. 189), hydrocyanic acid appears to be the nitrile of formic acid. It will be sufficient to study in detail the methods of formation and typical reactions of the second member of the series. Methyl Cyanide, or Aceto-nitrile, CH 3 .CN, occurs in crude benzene and in the distillation products of beet-root vinasse, and can be produced in a number of ways. Thus (*i) making use of a method indicated (p. 119) for the formation of esters, if methyl potassium sulphate is .distilled with dry potassium cyanide, aceto-nitrile is formed CH 3 SO 4 K + KCN - CH 3 .CN + K 2 SO 4 A small amount of the iso-cyanide is also formed, which can be got rid of by shaking with dilute HC1, neutralising with soda, and drying over fused CaCl 2 . (*2) Another useful way is to distil acetamide, or dry ammonium acetate, with P 2 O 5 , which acts as a dehydrating agent CH 3 .CONH 2 -H 2 O = CH 3 .CN CH 3 .COONH 4 -2H 2 O = CH 3 .CN o 194 Cyanogen and its Derivatives And finally, (*3) it has recently been shown that thionyl chloride decomposes acetamide, with production of the nitrile, the yield being very good CH 3 .CONH 2 + SOC1 2 = CH 3 .CN + 2HC1 + SO 2 The reactions with P 2 O 5 or SOC1 2 may be used to prepare it. Properties. Aceto-nitrile is a colourless liquid, b.p. 81.6, sp. gr. 0-805 at ~"' It nas a pleasant odour, is miscible with water and alcohol, and thrown out of its solution in the former by salts. The two following reactions which it undergoes are typical of the nitriles : (i) if boiled with alkalis or acids, it yields acetic acid and ammonia CH 3 .CN 4- KOH + H 2 O = CH..COOK + NH 3 CH 3 .CN + HC1 + 2H 2 O = CH 3 .COOH + NH 4 C1 and (2) on reduction with nascent hydrogen (sodium and alcohol), it yields ethylamine CH 3 .CN + 2 H 2 - CH 3 .CH 2 NH 2 In connection with the former reaction, it should be specially noted that not only is it an exceedingly general way of producing acids, but it is also an important link in a series of reactions which enable us to prepare homologous com- pounds from those which contain a carbon atom less. Thus the following series may be mentioned, each member of which can be prepared from that which immediately precedes it by reactions already indicated : C 2 H 5 OH C 2 H 5 I C 2 H 5 CN C 2 H 5 COOH C 2 H 5 CH 2 OH Ethyl alcohol Ethyl iodide Ethyl cyanide Propionic acid Propyl alcohol ISOCYANIDES, ISONITRILES, OR CARBAMINES. The properties of these bodies, which are isoineric with the nitriles, may be illustrated by methyl isocyanide, CH 3 .NC, or methyl carbamine. It is formed (*i) when methyl iodide, diluted with ether, is heated with two molecules of AgNC for several hours in a closed tube to 130. The crystalline compound AgNC -f.CH 3 .NC is first formed, and is then distilled with water and KCN CH 3 I + AgNC = CH 3 .NC -f Agl Methyl Isocyanide. Cyanic Acid 195 (*2) It is also very characteristically formed when methyl- amine is heated with alcoholic KOH and chloroform CH 3 NH 2 + CHC1, + 3KOH = CH 3 .NC + 3 KC1 + 3 H 2 O also from alkyl sulphates and KCN (see Nitriles). Properties. Methyl carbamine is a colourless, stinking liquid, b.p. 59*6, sp. gr. 0756 at 4. Its vapour produces nausea and headache. Unlike aceto-nitrile, it is not acted upon by alkalis : but acids resolve it into formic acid and methylamine CH 3 .NC + 2 H 2 = CH 3 NH 2 + HCOOH Water at 180 produces the same reaction. HgO oxidises it to methyl isocyanate. Constitution of Nitriles and Isonitriles. The different manner in which the two classes of substances react with dilute acids clearly brings out the difference between them. Thus the nitrile loses its nitrogen atom easily in the form of ammonia, the Carbon of the CN group remaining fixed, while on reduction an amine is produced hence the carbon is apparently the linking atom of the CN group ; on the contrary, the isonitriles readily lose carbon with production of formic acid and an amine. These facts lead to the formulae CH 3 C=N and CH 3 N=C in the two cases. OXYGEN COMPOUNDS OF CYANOGEN ; CYANIC AND CYANURIC ACIDS. Cyanic Acid, HOCN, cannot be obtained from its salts by the action of acids, but only by heating its polymer cyanuric acid in a current of CO 2 , and condensing the vapours in a receiver surrounded by a freezing mixture. Some of the polymeric substance cyamelide is always formed. Properties. Cyanic acid is a mobile, volatile liquid, sp. gr. 1*14 at ^-. It is strongly acid, smells like glacial acetic acid, and its aqueous solutions break up at about o, according to the following equation : HOCN + H a O = CO. + NH, 196 Cyanogen and its Derivatives It changes quickly into the white polymeric solid cyamelide at o ; above that temperature the reaction is very violent. Constitution. There are two possible structural formulae for this acid N^C OH = C= NH Normal cyanic acid Isocyanic acid It is not known, however, which is the correct one ; but though there is no known distinction between the two possible acids, and there are not two series of metallic salts cor- responding to them, there are two series of esters. Cyanates. The salts are probably derivatives of the iso- acid. Two of them only will be noted. Potassium Isocyanate, CO:NK, ordinary cyanate of potassium, is readily formed by the oxidation of potassium cyanide by heating in the air or in the presence of an easily reducible oxide KCN + PbO - CO:NK + Pb It is usually formed by heating ferrocyanide of potassium with some oxidising agent, e.g. K 2 Cr 2 O 7 , and extracting it with alcohol (see Urea, p. 202). The salt crystallises in colourless laminae, which resemble KC1O 3 ; it is readily soluble in water, but insoluble in absolute alcohol. Heat does not decompose it, but in presence of water it forms NH 3 and Kj,CO 3 . Ammonium Isoeyanate, CO:N.NH 4 , is formed by mixing dry ammonia vapour with that of cyanic acid. Its solution on evaporation undergoes intramolecular change, with the formation of urea (see p. 202) CO:N.NH 4 = CO:(NH 2 ), Cyanogen Chloride, CNC1, may be looked upon as the acid chloride of cyanic acid, and is formed when mercuric cyanide, Hg(CN) 2 , is decomposed by chlorine. It is a colour- less gas with pungent odour, which is condensible at 15 to a liquid. It polymerises spontaneously, forming solid cyanuric chloride, C 3 N 3 C1 3 . Cyanamide, CN.NH 2 , is formed from the latter body by Cyanuric Acid. Ethyl Isocyanate 197 the action of ammonia ; also by the action of HgO upon thio- urea CS(NHo), + HgO = CN.NH 2 + HgS + H 2 O It is a white crystalline solid, m.p. 40, which polymerises on heating. Cyanuric Acid, C 3 N 3 O 3 H 3 .2H 2 O, is a polymer of cyanic acid, and can be obtained (i) by boiling cyanuric chloride with dilute alkalis C 3 N 3 C1 3 + 3HX> = C 3 N 3 3 H 3 + 3 HC1 or (2) by leading dry chlorine into melted urea at 130, dis- solving out NH 4 Cl by cold water, and recry stall ising the acid 3CON 2 H 4 + 3d = C 3 O 3 N 3 H 3 + 2 NH 4 C1 + HCl + N Cyanuric acid crystallises (from water) with 2 molecules of water in rhombic prisms, which are efflorescent and soluble in water and alcohol. On distillation it yields cyanic acid (p. 195). There are two possible structural formulae for it, and it yields two series of esters. Ordinary cyanuric acid is probably the normal acid, (CN) 3 (OH) 3 . ESTERS OF CYANIC AND ISOCYANIC ACIDS. Ethyl Cyanate, CN.OC 2 H 5 , cyanetholine, is said to be formed when cyanogen chloride is acted upon by sodium ethylate CNCl + C. 2 H 5 ONa = CN.OC 2 H 5 + NaCl It is a colourless liquid, insoluble in water, and decomposes on distillation. Ethyl Isocyanate, CO:NC 2 H 5 , ethyl carbimide, is an example of the ordinary cyanic esters. It may be obtained (*i) by distilling potassium ethyl sulphate with the ordinary cyanate of potassium (isocyanate) at i8o-25o CO:NK + C 2 H 5 SO 4 K = CO:NC 2 H 5 -f K 2 SO and (*2) by the action of ethyl iodide upon silver cyanate (isocyanate) CO:NAg + C 2 H 5 I = CO:NC 2 H 5 + Agl 198 Cyanogen and its Derivatives It is a mobile liquid, b.p. 60, sp. gr. 0-898, with a suffocating, penetrating smell. When heated with alkalis or aqueous acids it forms ethylamine, which shows that the nitrogen atom is directly united to the ethyl group CO:NC 2 H 5 + 2 KOH = C 2 H 5 NH 2 + K 2 CO 3 CO:NC 2 H 5 + H 2 O + HC1 = C 2 H 5 NH 2 .HC1 + CCX THIOCYANIC ACIDS. Just as there are apparently two possible cyanic acids, so there are two possible thiocyanic acids N=C SFI S=C=NH Normal thiocyanic acid Iso-thiocyanic acid or or sulphocyanic acid thiocarbimide The normal acid is known, and the metallic thiocyanates are also normal (difference from cyanates). Esters of both the acids are also known. Thiocyanic Acid, NC.SH, can be prepared by distilling its potassium salt with dilute H 2 SO 4 (compare cyanic acid), or by decomposing the mercury salt with H 2 S or HC1. It is a colourless liquid with a strong smell, which crystallises at 1 2 '5. It is soluble both in water and alcohol, and is a very strong acid, nearly equal in avidity to HC1. The anhydrous acid polymerises on standing; the aqueous acid is stable. Heat breaks it up into HCN and persulpho-cyanogen, H 2 C 2 N 2 S 3 . Ferric salts colour solutions of both the acid and its salts a deep red, hence its employment in inorganic analysis. Potassium Thiocyanate, CN.SK, can be obtained by dissolving sulphur in an aqueous solution of KCN, but is usually prepared from potassium ferro- cyanide by fusion with K 2 CO 3 and sulphur. \Process. Heat 64 grams of sulphur and 34 grams K 2 CO 3 in a pot till they melt ; then add 92 grams dry K 4 FeCy G and heat till that salt is quite decomposed. Then extract with water, neutralise with H 2 SO 4 , evaporate to dryness, next extract with alcohol and recrystallise. The salt is obtained as long white deliquescent crystals, which resemble KNO 3 . Thiocyanates. Mustard Oils 199 Ammonium Thiocyanate is obtained by heating 8 parts carbon bisulphide with 30 parts ammonia in 30 parts alcohol, and concentrating to crystallisation CS 2 + 4 NH 3 = CN,SNH 4 + (NH 4 ) 2 S It forms large white deliquescent plates, very soluble in water and alcohol. It melts at 147, and if heated to about that temperature undergoes intra-molecular change with production of thio-urea (compare Ammonium cyanate). Mercury Thiocyanate is formed when mercuric nitrate is added to a solution of potassium or ammonium thiocyanate. When burned it swells up (Pharaoh's serpents). ESTERS OF THE THIOCYANIC ACIDS. Esters of the Normal Acid may be formed from its potassium or silver salt and a haloid paraffin ; e.g. (C 2 H 5 I) CN.SK + C 2 H 5 I = CN.SC 2 H 5 + KI and in other ways. They are liquids insoluble in water, with an odour like mercaptans. On reduction they yield mercaptans and HCN- CN.SC 2 H 5 + H 2 - C 2 H 6 SH + HCN and oxidation produces sulphonic acids. Both these reactions show that the sulphur atom is united to the ethyl group. Mustard Oils or Isothiocyanic Esters, thiocarbimides, are formed by a complex reaction from primary amines by the successive action of CS 2 , and HgCl 2 or AgNO 3 , and heating the product. This is what is termed Hofmann's^ " mustard oil test " for amines. The mustard oils are all pungent-smelling liquids, which boil at a lower temperature than their isomers. Nascent hydrogen (Zn and HC1) reduces them to amines and thio- formaldehyde (compare Normal esters) CS:NC 2 H 5 + 2 H 2 = C 2 H 5 NH 2 + H.CHS when heated with HC1 to 100 they break up according to the equation CS:NC 3 H B + 2H..O = C 2 H 5 NH 2 + CO 2 + H 2 S 2OO Derivatives of Carbonic Acid The liberation of amines in these and other reactions leads to the conclusion that in the mustard oils the nitrogen atom is the linking atom. Allyl mustard oil will be described, p. 209. CHAPTER XXVI. DERIVATIVES OF CARBONIC ACID. UREA; URIC ACID. THE hypothetical carbonic acid, COr^Qjj might be looked upon as the first of the series of hydroxy- acids (p. 224), but that the fact of its hydroxyl groups being both attached to the same carbonyl group, and being therefore of exactly equal value, gives it properties different from those of the other hydroxy-acids, in which the hydroxyl groups possess distinctly different values. We need not discuss free carbonic acid, and its anhydride carbon dioxide is well known to the student of inorganic chemistry ; but several of the derivatives of the acid will be mentioned. Carbon Monoxide, CO, may be looked upon as the anhydride of formic acid, and is noticeable as being a free oxygenated carbon radicle. Its formation from formates (p. 139) and from K 4 FeC 6 N 6 (p. 192) has been noted, and it is useful in the synthesis of carbon acids (see pp. 143, 149) and in the formation of carbonyl chloride. At a red heat it is a powerful reducing agent. Carbonyl Chloride, COC1 2 , phosgene gas, carbonoxychloride, is produced (i) by the direct union of carbon monoxide and chlorine in sunlight. It is also formed (2) when CO is lead into boiling antimony pentachloride, and (3) when chloroform is oxidised bv potassium dichromate and sulphuric acid. The first method, or a modification of it, is the best. Phosgene gas is a colourless gas which condenses to a Carbamic Acid. Urea 201 liquid, b.p. 8. It acts as an acid chloride ; thus it decomposes water COCL + H 2 - CO, + 2HC1 and also reacts with alcohols and ammonia (see below). Esters of Carbonic Acid. Phosgene gas acts upon alcohols, forming esters of chlor-carbonic acid, better named chlorformic acid ; thus with C 2 H 5 OH it yields ethyl chlor- carbonate COC1 3 + C 2 H 5 OH = CO^ l aH + HC1 which gives ethyl carbonate by treatment with sodium ethylate C is not known in a free state, but its ammonium salt is obtained by the action of ammonia upon carbon dioxide 2 NH 3 + C0 2 = C This body absorbs water, and yields ammonium carbonate. The ethereal salts, known as urethanes, are obtained by acting with ammonia upon chlorformic esters or the esters of carbonic acid. Urea, CO(NH 2 ) 2 , carbamide, the amide of carbonic acid, is an important product of vital action, and is contained in considerable quantity in human urine and in that of all mammals, especially those which are carnivorous, as well as in other animal juices. Its synthesis by Wohler, in 1828, 2O2 Derivatives of Carbonic Acid from ammonium cyanate, marks an epoch in the history of chemical theory. It can be prepared from urine as follows : Process. Evaporate urine to a syrup, and add pure HNO 3 . Nitrate of urea separates ; recrystallise this from dilute HNO 3 , and decompose it by K 2 CO 3 . The urea is separated from the KNO 3 formed by extraction with alcohol, and allowed to crystallise from that solvent. Urea is synthetically obtained (i) by the intra-molecular transformation of ammonium cyanate. In the process given below potassium cyanate is first formed (p. 196) ; this salt is decomposed by ammonium sulphate, and the solution of ammonium cyanate thus produced gives urea when evaporated to dryness (i.) 2 CO:NK + (NH 4 ) 2 S0 4 = 2 CO:N.NH 4 + K 8 S0 4 (ii.) CO:N.NH 4 =CO(NH 2 ) 2 \Process. Intimately mix 120 grams of well-dried anhydrous ferrocyanide of potash with 45 grams of dry potassium carbonate, and heat in a covered iron crucible till it just melts ; lift out, cool a little, and add little by little, with stirring, 225 grams of red lead. Put the crucible in the fire again, and keep the mixture melted for a little time ; then allow the lead to settle ; pour off the melt on to an iron plate, and allow to cool (potassium cyanate could be extracted by alcohol from this if desired). Break up the solid, dissolve in 230-250 c.c. water, and add a concentrated solution of 1 20 grams neutral sulphate of ammonium. Evaporate the liquid to smaller bulk ; potassium sulphate crystallises out. Separate the liquid, and evaporate it to dryness. Extract the residue with alcohol, and recrystallise the urea obtained, if necessary purifying it by shaking the solution with animal charcoal. Urea is also synthetically formed (2), as might be expected, when either carbonyl chloride or ethyl carbonate is treated with ammonia (compare Acetamide, p. 182) COC1 2 + 4NH 3 = CO(NH 2 ) 2 + 2 NH 4 C1 CO(OC 2 H 5 ), + 2 NH 3 = CO(NH 2 ) 2 + 2 C 2 H 5 OH and (3) also when ammonium carbonate (carbamate) is heated fO-^ NH 2 ^ONH 4 - Urea. Carbon Oxy-stilphide 203 Properties. Urea crystallises in long colourless needles or prisms, m.p. 132, sp. gr. 1-323, and has a taste resembling saltpetre. It is soluble in water and alcohol. When heated above its melting point it decomposes into biuret, cyanuric acid, etc. Heated with water above 100 in closed tubes or with solutions of alkalis or acids, it is decomposed thus 'CO(NH 2 ) 2 4- H 2 = CO 2 + 2 NH 3 Hypochlorites and hypobromites decompose urea with liberation of nitrogen and carbon dioxide, and this liberation of nitrogen is used as a test for the quantity present in urine CO(NH 2 ) 2 + 3 NaOCl = CO 2 + N 2 + 3 NaCl + 2 H 2 O Nitrous acid acts similarly CO(NH 2 ) 2 4- 2 HNO 2 = CO 2 + 2N 2 + 3H 2 O Like acetamide, it combines with acids, the nitrate being the most characteristic salt, and it also forms a characteristic precipitate with Hg(NO 3 ) 2 . Constitution. Urea must be looked upon as the amide of carbonic acid, since it is formed from ethyl carbonate and carbonyl chloride by reactions which are quite analogous to those which yield acetamide. Identification. In the presence of ammonium salts urea is often difficult to identify ; the following tests assist in detecting it : It yields NH 3 when heated alone or with alkalis, and gives off nitrogen with hypochlorites. When heated to 1 50 it forms biuret ; if this is dissolved in water, a few drops of CuSO 4 solution added, and then NaOH solution, a red to violet colour is obtained. There are many sulphur compounds which are analogous to the oxides of carbon and the carbonates. Carbon Monosulphide, CS, is obtained as a red powder by the action of light on the disulphide. Carbon Oxy-sulphide, COS, carbonyl sulphide, is pro- duced (i) when sulphur vapour and CO are passed through red-hot tubes ; and (2) potassium thiocyanate is heated with H 2 SO 4 diluted with an equal volume of water KCNS 4- 2H 2 SO 4 + H 2 O = COS 4- KHSO 4 + NH 4 HSO< 2O4 Derivatives of Carbonic Acid It is a heavy colourless gas with a slightly aromatic odour, and is decomposed by alkalis and alkaline earths, forming carbonates and sulphides. Tri-thio-carbonic Acid, CS(SH) 2 . When alcohol and ether are added to a solution of Na 2 S, which contains CS 2 , sodium tri-thio-carbonate separates out ; this salt yields the free acid as a brown oily liquid when it is decomposed by HC1. Ethereal salts of it are known. Carbon Bisulphide, CS 2 , may be looked upon as the sulphanhydride of tri-thio-carbonic acid. It is produced by passing sulphur vapour over ignited carbon. It is a colourless, highly refractive liquid, b.p. 46, sp. gr. 1-292 at %l. If thoroughly purified it has an ethereal odour, but as usually obtained its odour is very disagreeable. Its vapour is very poisonous. It is almost insoluble in water, and is a useful solvent for oils, fats, and resins. Its analogy to CO 2 is shown by its union with metallic sulphides to produce tri-thio- carbonates. Thio-carbonyl Chloride, CSC1 2 , may be obtained by the action of chlorine, or of PC1 5 , upon CS 2 CS 2 + PC1 5 = CSC1 2 + PC1 3 S It is a red liquid, b.p. 70, with a pungent odour resembling that of COC1 2 . Thio-urea, CS(NH 2 ) 2 , or sulpho-carbamide, is obtained when ammonium thiocyanate is heated to I7o-i8o for several hours (compare the formation of urea from ammonium cyanate, p. 202). When perfectly pure it crystallises in rhombic prisms, m.p. 169. It decomposes on heating with alkalis or acids CS(NH,) 2 + 2H 2 = C0 2 + 2 NH 3 + H 2 S (compare Urea), and it forms a crystalline nitrate. Uric Acid, C 5 H 4 N 4 O3, lithic acid, is found in many animal substances, either free or as a salt. Thus it is found free (and as the ammonium salt) in the urine of both carnivo- rous and herbivorous animals, especially of the former; also in human urine. Serpents' excrement consists almost entirely of Uric Acid 205 ammonium urate, and it is largely present in guano. In gout it is found in the blood as the acid sodium salt. The acid can be prepared artificially, amongst other methods, by heating urea and glycocoll together. Preparation. Uric acid is best prepared by dissolving out oxalates, phosphates, and carbonates from guano by treatment with dilute HC1, boiling the residue with caustic soda, and acidifying the clear solution with HC1, when uric acid separates in fine crystals. Properties, Uric acid separates from its solution as a white crystalline powder, which is insoluble in alcohol, difficultly soluble in water, and moderately so in glycerin. On heating alone it decomposes with formation of urea, cyanic, and cyanuric acids, and CO 2 ; while on heating with HI, glycocoll, NH 3 , and CO 2 are produced. It acts as a weak dibasic acid, and forms difficultly soluble salts, its acid properties being due to the imido (NH) groups which it contains. Identification. Uric acid may be detected by the reddish- purple colour of murexide (acid ammonium purpurate) which is produced when it is evaporated to dryness with HNO 3 , and the pink residue so obtained is treated with ammonia. If potash is employed instead of ammonia, a violet-blue colour is obtained. SECTION IV. DERIVATIVES OF UNSATURATED HYDRO- CARBONS. CHAPTER XXVII. DERIVATIVES OF THE OLEFINES. JUST as the paraffins yield haloid substitution products, alco- hols, esters, acids, etc., so do the olefines, although their number is not so great, and, with certain exceptions, they need not be discussed in an elementary work; the allyl compounds being the most noteworthy. MONO-HALOGEN DERIVATIVES OF THE OLEFINES. Chlor-ethylene, CH 2 :CHC1, vinyl chloride, cannot be prepared by the action of chlorine upon ethylene, because the chlorine forms ethylene chloride. If, however, ethylene chloride or ethylidene chloride is gently treated with alcoholic potash, one molecule of HC1 is abstracted, and this gas is formed CH 2 C1.CH 2 C1 + KOH = CH 2 :CHC1 + KC1 + H 2 O The reaction is quite analogous to that for the formation of ethylene from C 2 H 5 I (p. 54). Properties. It is a colourless gas, which smells like garlic, condenses to a liquid, b.p. 16, and readily undergoes poly- merisation in sunlight. Brom-ethylene, CH 2 :CHBr, vinyl bromide, and iodo ethylene, CH 2 :CHI, vinyl iodide, are formed analogously to the chlorine derivative. The former is a liquid, b.p. 16, sp. gr. 1*516 at , the latter an oil smelling like garlic, b.p* 56, sp. gr. 2-08 at>. Ally I Iodide 207 Allyl Iodide, CH 2 I.CH:CH 2 , can be prepared by the action of phosphorus and iodine upon allyl alcohol, but it is usual to act upon glycerin with those reagents (see p. 70) C 3 H 5 (OH) 3 + 3 HI - C 3 H 5 I + 3H 2 + I 2 ^Process. Introduce 150 grams of dry glycerin into a half-litre tubulated retort along with 105 grams of iodine. Connect the tubulus of the retort by wide indiarubber tubing to a flask con- taining 35 grams of white phosphorus, cut into pieces about the size of a pea and well dried, and pass a current of CO 2 through the whole apparatus. Drop the phosphorus into the retort little by little by tilting the small flask, starting the reaction if required by warming gently. The distillation must proceed so that the allyl iodide distils as it is formed, and is continued till the glycerin begins to carbonise. Wash the lower layer of the distillate with soda, dehydrate over CaCl 2 , and rectify, collecting the portion distilling between 98 and 102, which is nearly pure allyl iodide, apart. This still contains propylene iodide and allyl alcohol, and can be purified by forming the mercury compound, recrystallising it, and then decomposing it with iodine (see below). Properties. Allyl iodide is a colourless liquid, b.p. 1027, sp. gr. i '8696, which smells like garlic. Nascent hydrogen reduces it to propylene (Zn and HC1, or the wet Zn-Cu couple). It combines with mercury to form allyl mercuric iodide, C 3 H 5 HgI, which iodine decomposes, liberating the iodide C 3 H 5 HgI + I 2 = C 3 H 5 I + HgI 2 The di-haloid defines result from combination of the halogens with acetylene. Generally speaking, the haloid defines resemble the olefines themselves in readily combining with the halogens, halogen hydrides, and hypochlorous acid, and many undergo polymerisation with ease. MONO-HYDRIC ALCOHOLS OF THE ALLYL SERIES, CnH^jOH. The best-known alcohol of the series is allyl alcohol, C 3 H S OH. The simplest member of it would be vinyl alcohol, which is yet unknown, since all reactions which might be expected to yield it, by a molecular transformation, give acetaldehyde instead, i.e. CH 2 :GH.OH becomes CH 3 .CHO. 2o8 Derivatives of the Olefines This molecular change is general ; the group C:CH.OH always actually becomes =CH.CHO. Allyl Alcohol, C 3 H 5 OH - CH 2 :CH.CH 2 OH, is found in very small quantity in crude wood spirit, (i) The earliest method of formation was the decomposition of allyl oxalate (obtained by the action of silver oxalate upon allyl iodide) by dry gaseous ammonia. This produces oxamide and allyl alcohol, which latter can be distilled off C 2 2 (C 3 H 5 0) 2 + 2 NH 3 = C 2 2 (NH 2 ) 2 + 2C 3 H 5 OH (2) A better method is by heating allyl iodide with 20 parts of water in a closed tube at 100 C. ; but (3) the method usually employed for preparing it is the distillation of oxalic acid and glycerin. This depends upon the formation of mono-formin, which breaks up on heating into allyl alcohol, carbon dioxide, and water, thus Compare this reaction with that used in preparing formic acid (p. 137). ^ Process. Heat 200 grams of glycerin, 50 grams of crystallised oxalic acid, and 0-5 gram of NH 4 C1 in a retort to 190 C. Change the receiver at that temperature, collect the distillate to 260, rectify the distillate, which contains acrolein, allyl formate, and glycerin, besides allyl alcohol, by distillation. Next dry, first over K 2 CO 3 , then over KOH, and distil. The alcohol so procured boils at 90, and can be completely dehydrated by means of CaO or BaO. Properties. Allyl alcohol is a colourless mobile liquid, b.p. 96'6, sp. gr. 0-8706 at , and solidifies at 50. It has a pungent odour and burning taste is miscible with water, alcohol, and ether. It burns with a bright flame. Oxidation with chromic acid yields formic acid and carbon dioxide, while, if oxidised by silver oxide, it yields acrolein and acrylic acid. Nascent hydrogen (Zn and H 2 SO 4 ) forms n-propyl alcohol. Solid KOH at 150 also produces n-propyl alcohol, along with formic acid and other oxidation products. Being unsaturated, allyl alcohol combines with two atoms of a halogen to form a halogen hydrin of glycerin, and with one Ally I Sulphide. Ally I Mustard Oil 209 molecule of cyanogen to form a cyanhydrin. The last two reactions show it to contain two atoms of hydrogen less than propyl alcohol ; and, as it also yields on oxidation an aldehyde, and an acid, which contain the same number of carbon atoms that it does, the only possible constitictional formula is that assigned to it. ESTERS OF ALLYL ALCOHOL. Amongst the esters of this alcohol two only will be mentioned, viz. the sulphide and the iso-thiocyanate. Allyl Sulphide, (C 3 H 5 ) 2 S, is the principal constituent of oil of garlic, obtained by distilling that plant with water, and is also found in other plants. It may be artificially prepared by acting upon allyl iodide with an alcoholic solution of potassium sulphide Properties. Allyl sulphide is a strongly refractive liquid with an odour of garlic, b.p. 140. It forms crystalline precipitates with PtCl 4 , AuCl 3 , AgNO 3 , and other salts. Allyl mustard oil, or Allyl iso-thiocyanate, C 3 H 5 N:CS, allyl thiocarbimide, is found in the oil distilled from black mustard-seed, and is also present in garlic and horseradish. Black mustard-seed contains a glucoside called potassium myronate, which is decomposed in the presence of water by an unorganised ferment called myrosin, which is also contained in the seeds, according to the equation C 10 H 18 NS 2 10 K = C 3 H 5 N:CS + C 6 H 12 O 6 - + KHSO 4 The mustard oil is also formed by a molecular transposition when allyl iodide is acted upon by an alcoholic solution of potassium thiocyanate. Properties. Allyl mustard oil is an oil, b.p. 151, sp. gr. i '02 8, with a pungent odour and a burning taste, and blisters the skin. UNSATURATED ALDEHYDES, C n H 2n _ 2 O. These aldehydes are related to the alcohols of the allyl 2io Derivatives of the Ole fines series in the same way that acetaldehyde is to ethyl alcohol. The lowest member of this series Acrylic Aldehyde or Acrolein, CH 2 :CH.CHO, is the very pungent liquid obtained when fats are heated, its for- mation being due to the glycerol which they contain. It can be formed (i) by oxidation of allyl alcohol, since that contains a primary alcoholic group ; and (2) by dehydrating glycerin with potassium bisulphate or phosphorus pentoxide C 3 H 5 (OH) 3 - 2 H 2 - C 3 H 4 ^Process. Distil together 50 grams glycerin (anhydrous) and 100 grams KHSO 4 , and redistil the product over lead oxide. Properties. Acrolei'n is a colourless, mobile, refractive liquid with a burning taste, b.p. 52-4, sp. gr. o'8/j.i at - 4 -o. Its vapour is very pungent, and intensely irritating to the nose and eyes. It is slightly soluble in water. Like other aldehydes, it is a strong reducing agent ; thus it reduces ammoniacal AgNO 3 solution, with formation of a mirror, and production of acrylic acid. Acrolei'n is reduced by Zn and HC1 to allyl alcohol. It reacts with NH 3 to form a red amorphous substance, water being eliminated; and com- bines with two molecules of NaHSO 3 (difference from fatty aldehydes). PC1 5 forms allylene chloride, and Br 2 forms di-brom-propionic aldehyde. When impure, acrolein readily passes into disacryl, a white amorphous mass which is isomeric or polymeric. Crotonic Aldehyde, CH 3 .CH:CH.CHO, croton aldehyde, is of interest as being a condensation product of acetaldehyde when it is heated with zinc chloride and water to 100. Hydrochloric acid or sodium acetate will also effect the change. Its formation by the first method depends upon the preliminary production of aldol, which then loses water, forming the aldehyde 2CH 3 .CHO = CH 3 .CH(OH).CH 2 .CHO = CH 3 .CH:CH.CHO + H 2 O Properties. Crotonic aldehyde is a pungent mobile liquid, b.p. 105, sp. gr. at - 1*033. I* is soluble in water, and is oxidised by air or silver oxide to crotonic acid. Acrylic Acid 21 1 UNSATURATED MONO-BASIC ACIDS. ACIDS OF THE ACRYLIC OR OLEIC SERIES. Acrylic acid, C 2 H 3 COOH Crotonic acid, C 3 H 5 COOH Oleic acid, C 17 C 33 COOH, etc. These acids are related to the allylic series of alcohols, just in the same way that acetic acid is related to ethyl alcohol. CH 3 .CH 2 OH CH 3 .CHO CH 3 .COOH Ethyl alcohol Acetaldehyde Acetic acid C 2 H 3 .CH 2 OH C 2 H 3 .CHO C 2 H 3 .COpH Allyl alcohol Acrolei'n Acrylic acid Acrylic Acid, CH 2 :CH.COOH, may be readily produced (*i) by the oxidation of acrolein CH 2 :CH.CHO + O = CH 2 :CH.COOH Process. Pour a mixture of i part acrolem and 3 parts of water upon freshly precipitated Ag 2 O suspended in water and contained in a vessel screened from the light. When the reaction is over, heat gently to the boiling point, and add Na 2 CO 3 till the whole is slightly alkaline. Evaporate the nitrate to dryness, and distil the residue with dilute H 2 SO 4 . Form the silver or lead salt, dry it, and decompose in a current of H 2 S at 170. Acrylic acid is also produced (*2) by the action of alco- holic KOH upon /2-iodo-propionic acid 1 CHal.CHa.COOH + 2KOH = CH 2 :CH.COOK + KI + 2 H 2 O (compare the action of KOH on C 2 H 5 I, p. 54). (*3) It can be formed by distillation of /3-hydroxy-propienic (hydracrylic) acid CH 2 OH.CH 2 .COOH = CH 2 :CH.COOH -f H 2 O (compare formation i of defines, p. 56). Properties. Acrylic acid is a colourless liquid with a pungent 1 Halogen, hydroxyl, or other derivatives of alcohols, aldehydes, or acids, are named according to the position of the substituent to the CH 2 OH, CHO, or COOH groups, e.g. if a halogen atom is attached to the adjacent carbon atom of an acid, it will form an a halogen acid ; if to the second, a compound ; to the third, a 7 derivative, and so forth. Thus CH 3 .CHI.COOH and CH 2 I.CH 2 .COOH are and iodo-propionic acids respectively. 212 Derivatives of the Olefines acid odour (not unlike that of acetic acid), b.p. 140. It is miscible with water. It is converted into propionic acid by nascent hydrogen (boiling with Zn and H 2 SO 4 ) or by the action of sodium amalgam CH 2 :CH.COOH + H 2 = CH 3 .CH 2 .COOH It unites with one molecule of bromine to give a-/?-brom- propionic acid, and with HI and HOC1 yields /2-derivatives of propionic acid CH 2 :CH.COOH + Br 2 = CH 2 Br.CHBr.COOH CH 2 :CH.COOH + HI = CH 2 I.CH 2 .COOH /3-iodopropionic acid CH 2 :CH.COOH + HOC1 = CH 2 C1.CH(OH).COOH /3-chlorlactic acid On heating with an aqueous solution of NaOH to 100, it is changed into hydracrylic acid (see formation 3 above). On fusion with KOH it is characteristically oxidised, rupture of the molecule taking place at the double linkage, salts of formic and acetic acids being produced CH.:CH.COOK + KOH + H 2 O = H.COOK + CH 3 .COOK + H 2 With the exception of the silver salt, its salts are readily soluble in water, and give off part of their acid at 100, leaving basic compounds. Ordinary Crotonic Acid, CH 3 .CH:CH.COOH, is obtained by oxidising croton aldehyde, or from allyl iodide by the successive action of KCN and alcoholic KOH C 3 H 5 I + KCN - C 3 H 5 CN + KI C 3 H 5 CN + KOH + H 2 - C 3 H 5 COOK + NH 3 It crystallises in needles, m.p. 72, b.p. 182. It is reduced by Zn and H 2 SO 4 to n-butyric acid, and breaks up on fusion with KOH into two molecules of acetic acid. Amongst the higher homologues of this series, special note should be taken of Oleic Acid, Ci 8 H 34 O 2 . This acid is found as tri-olein in many natural fats and oils, especially in olive oil, almond oil, and cod-liver oil. Large quantities of it are obtained as a Oleic Acid 213 by-product of stearin-candle manufacture. It may be prepared most readily by saponifying either olive or almond oil by caustic potash C 3 H 5 (C 18 H 33 2 ) 3 + 3KOH = sC^KO, + C 3 H 5 (OH) 3 ^Process. Saponify olive oil by boiling with excess of KOH. Acidify the mixture, and heat the separated acids with lead oxide for some hours at 100. Dissolve out the lead oleate from the lead soaps formed, by ether. Acidify the ethereal solution with HC1, and filter from the precipitated PbCl 2 . Evaporate the filtrate till free from ether, neutralise with ammonia, and add BaCl 2 solu- tion to precipitate barium oleate. Recrystallise the barium salt from alcohol, and separate the oleic acid by the addition of tartaric acid. The impure oleic acid from candle manufacture (see p. 156) may also be used in the preparation of the pure substance, and, if freshly made, contains very few oxidation products. Properties. Pure oleic acid forms, below 14, a white crystalline mass, but over 14 it is a colourless, odourless oil, which does not redden litmus. If, however, it is exposed to the air, it absorbs oxygen, becomes yellow, acquires a rancid smell and an acid reaction. It boils at 286 at 100 mm. pressure, and distils in a current of steam at 250. Bromine forms dibrom-stearic acid, and HI and P reduce it to stearic acid. Nitrous acid transforms it into the isomeric solid elaidic acid. Ricinoleic Acid, C 17 H 32 (OH).COOH, hydroxyoleic acid, occurs in castor oil as a glyceride. It crystallises to a white mass, forms a solid di-bromide, and nitrous acid forms ricin- elaidic acid. GENERAL REMARKS. Many of these acids occur in fats and oils, and the synthe- tical reactions illustrated in considering acrylic acid are of general application. Properties. These acids resemble those of the acetic series in their physical properties, e.g. solubility, acidity, etc. ; chemically, however, they differ considerably, because they contain the group =C:C=, and therefore two atoms of 214 Acetylene Derivatives hydrogen less than that series. They are consequently capable of combining with halogens, halogen acids, and hydrogen in the manner already exemplified. Their decom- position on fusion with KOH is also quite characteristic, acetic acid being usually one of the acids produced. CHAPTER XXVIII. ACETYLENE DERIVATIVES. ALCOHOLS, C n H 2K _ 3 OH. THE halogen derivatives of the acetylenes are comparatively unimportant, and only a few alcohols of the series are known. Of these, propargyl alcohol is the only one which must be considered a true acetylene derivative. Propargyl Alcohol, CH:C.CH 2 OH, propinyl alcohol, is produced when /3-brom-allyl alcohol is heated with caustic potash and water; the liquid is then saturated with carbon dioxide, water added, and the alcohol distilled off. It can be separated from the distillate by carbonate of potash, and dried over lime CHBr:CH.CH 2 (OH) + KOH = CH:C.CH 2 (OH) + KB Properties. Propargyl alcohol is a colourless, pleasant- smelling, mobile liquid, b.p. 114-! 15, and sp. gr. 0-9628 at 21. Since it contains the group HC:C , as well as a hydroxyl group, it has two hydrogen atoms replaceable by metals, and ammoniacal copper and silver solutions respectively yield the explosive compounds Cu 2 (C 3 H 2 OH) 2 and C 3 H 2 (OH)Ag. It unites directly with bromine and HBr to form di- andmono- brom-allyl alcohols ; PC1 3 and PBr 3 respectively displace the OH group by Cl or Br. It is decomposed by fusion with KOH, with formation of acetylene, potassium formate, and hydrogen. Propiolic Acid. Linoleic Acid 215 UNSATURATED ACIDS FROM ACETYLENE. PROPIOLIC ACID, C 2 H.COOH LINOLEIC ACID, C 17 H 31 COOH Of these acids, which contain four atoms of hydrogen less than the corresponding ones of the acetic series, the best known is Propiolic Acid, CH-C.COOH, the potassium salt of which is obtained by gently heating an aqueous solution of the mono-potassium salt of acetylene di-carboxylic acid (obtained by the action of alcoholic potash on dibrom- or iso-dibrom- succinic acid) CHBr.COOH C COOH | + 3KOH = HI -f 2KBr + 3 H 2 O CHBr.COOH C COOK C COOH CH III =111 + co, C COOK C COOK Properties. Propiolic acid, liberated from the above salt, crystallises in silky needles, which melt at 6 C., and it boils with decomposition at 144. It has a smell very like acetic acid. Being unsaturated, it can unite directly with the halogens, etc., forming first olefine, and then paraffin derivatives. It is reduced by sodium amalgam to propionic acid. Its potassium salt yields explosive compounds with ammoniacal silver and cuprous solutions. Linoleic Acid, C 17 H 31 O 2 , is found as an ester of glycerin in drying oils, such as linseed oil, hemp oil, and poppy oil, as well as in smaller quantities in many others. It is obtained by saponification of linseed oil, and purified by means of its barium salt, which is soluble in ether. It is a yellow oil, sp. gr. 0-92, insoluble in water. It is reduced by HI and P to stearic acid, and bromine forms tetra-brom stearic acid (compare Oleic acid). SECTION V. DIHYDRIC ALCOHOLS AND THEIR DERIVATIVES. CHAPTER XXIX. GLYCOLS. So far we have only considered derivatives of hydrocarbons in which one hydrogen atom is replaced by one of the mon- atomic groups CH 2 .OH, CO.H, or CO.OH. We have now to study those in which two hydrogen atoms are replaced, so yielding dihydric alcohols, di-aldehydes, di-basic acids, or intermediate substances possessed of the characters of any two of those classes. These bodies will be found possessed of many of the characteristics of similar monovalent compounds, as well as of special properties due to the fact that they are divalent derivatives. Many of the methods of preparation will be entirely analogous to those already given for the production of the analogous monovalent compounds. The simplest of these substances known in a free state is the dihydric alcohol glycol. This may be considered as derived from ethane by the replacement by hydroxyl of one of the hydrogen atoms attached to each of the two carbon atoms CH 3 CH 2 OH | yields | CH 3 CH 2 OH It will be noticed that glycol contains the group CH 2 OH twice, and is therefore a fa-primary alcohol. By the careful Glycols 217 oxidation of this body the di-aldehyde glyoxal can be pro- cured CH 2 OH CHO | yields | CH 2 OH CHO And this, in its turn, can be oxidised to oxalic acid CHO COOH | yields | CHO COOH There are, however, a number of intermediate compounds producible by suitable methods; thus, besides the above- CH 3 OH named, there may be produced glycollic aldehyde, | CHO, CHO CH 2 OH glyoxylic acid, | , and glycollic acid, | . Other COOH COOH dihydric alcohols form similar series. The hydroxyl groups of the alcohols may be partly or entirely replaced, according to circumstances, by other radicles, such as acetyl, amidogen, cyanogen, chlorine, and bromine, in exactly the same way as those of the monohydric alcohols. The dihydric alcohols, similarly to the monohydric, may be classed as primary, secondary, and tertiary, according to the manner in which the hydroxyl groups are substituted in the parent hydrocarbon; but it must be remembered that glycols in which the hydroxyl groups are both attached to the same carbon atom are not known in the free state, but that reactions which we should expect to yield them actually produce aldehydes. DIHYDRIC ALCOHOLS, OR GLYCOLS. The first member of this series is Methylene Glycol, CH 2 (OH) 2 , formic ortho-aldehyde^ which is not known to exist free, although it is supposed by some that it is present in the solution produced by heating para-formaldehyde (p. 123) with water to 130; the reactions, however, by which we should expect to obtain it always yield 2i 8 Glycols its anhydride, i.e. formaldehyde. But though its existence free is not certain, we are acquainted with several of its derivatives, e.g. the di-methyl ether, methylal, CH 2 (OCH 3 ) 2 , is obtained by the oxidation of wood spirit, and is an aromatic-smelling liquid, b.p. 42. Ethylal, the di-ethyl ether, is also known, and methylene acetate, CH 2 (C 2 H 3 Oo) 2 , an oily liquid obtained by heating methylene iodide with silver acetate, may also be mentioned. The acetate is soluble in water, has a strongly pungent taste and smell, and when heated in a sealed tube for some hours to 100 does not yield the glycol, but para-formaldehyde. Glycol, CH 2 OH.CH 2 OH, ethene glycol, ethylem alcohol, can be obtained by methods which are quite the same in principle as those employed to prepare monohydric alcohols (p. 94) . ( The student should carefully refer to these, and compare them with the following methods.) Thus (*i) glycol can be prepared from ethylene iodide by treating it with silver acetate and saponifying the resultant product with potash (i.) C 2 H 4 I 2 + 2AgA = C 2 H 4 A 2 + 2AgI (ii.) C 2 H 4 A 2 + 2KOH = C 2 H 4 (OH) 2 + 2KA It can also be prepared from ethylene bromide by the successive action of potassium acetate and potash, or by heating it with PbO and water to 150, or by heating with water only to 100 in sealed tubes C 2 H 4 Br 2 + 2 H 2 = C 2 H 4 (OH) 2 + 2 HBr ^Process. Amodification of the last process is usually employed. Boil 1 88 grams of ethylene bromide with 138 grams of K 2 CO 3 and i litre of water in a flask provided with an inverted condenser. When the whole of the bromide is dissolved, concentrate the liquid on the water-bath, filter from the crystals of KBr which are formed, and wash them with alcohol. Distil the alcoholic filtrate, and collect apart the portion that distils between 185 and 205. Redistil that fraction, and collect that which comes over between 195 and 200 as glycol. The yield is small. A considerable proportion of vinyl bromide, C 2 H 3 Br Glycol 219 escapes during the process as the result of a secondary reaction, and may be condensed in bromine. The fundamental reaction is represented thus C 2 H 4 Br 2 + HoO 4 K 2 CO 3 = C 2 H 4 (OH) 2 + 2KBr + CO 2 the reaction which results in the formation of the vinyl bromide being C 2 H 4 Br 2 + K 2 CO 3 = C 2 H 3 Br-f KBr + KHCO 3 Properties. Glycol is an inodorous, colourless, syrupy liquid with a sweet taste, b.p. 198, and sp. gr. 1*1168 at }-!. It is miscible with water and with alcohol, and but slightly soluble in ether. Nitric acid ultimately oxidises it to oxalic acid, but there is intermediate formation of glycollic acid, glyoxal, etc. Strong hydrochloric and hydrobromic acids react with glycol, displacing successively one or two hydroxyl groups by Cl or Br, and forming halogen hydrins and di-haloid derivatives respectively OTT c 2 H 4 (OH) 2 4 HCI - cya > ' + KC 2 H 3 O 2 = C 2 H 4 v^ 4- KC1 Mono-acetin and if treated with potassium hydrate they yield the oxide of CH 2 the di-valent radicle | , ethylene oxide, which is a liquid CH 2 22O Glycols isomeric with acetaldehyde, and slowly absorbs water, re-forming glycol CH 2 OH CHo | + KOH = | ^O + KCl + H 2 CH 2 C1 CH 2 Ethylene oxide It is readily soluble in water, neutral in reaction, strongly basic in character, precipitates metallic hydroxides from solutions of their salts, unites with acetic acid to form the mono- acetate, with acetic anhydride to form the di-acetate of glycol, with hydrochloric acid to form chlorhydrins, with ammonia to form the hydramine C 2 H 4 ^: and with NaHSO 3 it yields N-H-2 CH 2 OH.CH 2 SO 3 Na. Hydriodic acid acts upon glycol differently to hydrochloric or hydrobromic acid. If suitable proportions are used, ethyl iodide is formed ; but if excess of the acid is employed, reduction takes place to the hydrocarbon itself, as has been explained previously (p. 47) ; thus OTT (i.) C 2 H 4 C + 3HI = C 3 H 8 I + 2H 2 + I 2 (ii.) C 2 H 5 I + HI = C 2 H 6 + I 2 The oxygen acids act upon glycol, forming basic or neutral esters. So, for example, from glycol and acetic acid, aided by heat, glycollic mono- and di-acetin may be produced ; thus C 2 H 3 O.OH = C 2 H 4 \TT -I- H 2 O 2C 2 H 3 O.OH = Glycol readily forms metallic derivatives (the glycollates) with alkali metals. Thus sodium dissolves in it, displacing hydroxylic hydrogen and forming the mono-sodium derivative ; and if that is heated with the metal, the second hydroxyl hydrogen atom is displaced. These compounds are decom- posed by water with the re-formation of glycol ; and they react Ethylidene Glycol. Acetal 221 with alkyl iodides to produce ethers in the same manner that ordinary ethers are formed from alcoholates (see p. 105) C 2 H 5 I = C 2 H 4 C;oH 5 + Nal C * H 44 ' Fig. 44, and grows in presence of sufficient nitrogenous food. Process. The usual method employed is the following : Dis- solve a mixture of 3 kilos, of cane sugar and 1 5 grams of tartaric acid in 17 kilos of boiling water. After two days add to this 1200 grams of zinc white (ZnO), along with 60 grams of putrid cheese which is suspended in 4 kilos, of sour milk. Keep this mixture at 4o-45 for 8-10 days, when a crystalline magma of zinc lactate is formed, as well as some mannitol (p. 259). Recrystallise the salt from boiling water ; then dissolve in boiling water, precipitate the zinc by H 2 S, and filter off the ZnS. Concentrate the filtrate by evaporation, and then extract with ether, which leaves the mannitol, and any undecomposed zinc salt, behind. The lactic acid is obtained from the ethereal solution by evaporation. Lactic acid is also produced by the- following general methods : (*2) from propylene glycol by oxidation; ("3) from 228 Oxidation Products of Glycols a-chlor- or a-brom-propionic acids by boiling with silver oxide ; (*4) from alanine, CH 3 .CHNH 2 .COOH, by HNO 2 ; these have been illustrated by glycollic acid. Also (*5) from ethylidene cyanhydrin (a-hydroxynitrile) by saponification with HC1 ; ^, Hydroxy-propionitrile The nitrile is obtained by the addition of HCN to aldehyde. Properties. Lactic acid, obtained as just described, is an uncrystallisable colourless syrup, sp. gr. 1-21-1-24. It has a sour taste, no smell, is hygroscopic, readily soluble in water and alcohol, not so readily in ether. It is not, however, the pure acid ; it always contains some anhydride, tjie amount of which increases rapidly till, after the lapse of some months, it may consist entirely of that substance and lactide (com- pare Glycollic anhydride and Glycollide). When heated to 130 the syrupy acid is changed into lactide, and at higher temperatures CO, CO 2 , and aldehyde are found as well. Heated with quicklime, alcohol and carbon monoxide are produced. Dilute H 2 S0 4 at 130 transforms it into aldehyde and formic acid, chromic acid mixture oxidises it to acetic acid and carbon dioxide. Hydrobromic acid forms a-brom-propionic acid, but hydriodic acid reduces it to propionic acid. A strong solution of potassium lactate, when subjected to electrolysis, yields aldehyde and carbon dioxide. In its formation of anhydrides, ethers, and esters, lactic acid is quite analogous to glycollic acid (see p. 226); e.g. it forms the anhydrides lactic anhydride, lactide, and di-lactic acid. Ordinary lactic acid and its salts are optically inactive, i.e t do not rotate the plane of polarised light. If, however, Penicillium glaucum is allowed to grow in a solution of ammo- nium lactate, the salt of the laevo-rotatory acid is destroyed, and dextro-rotatory para-lactic acid, CH,.CH(OH).COOH, is obtained from the residue. Sar co- lactic Acid. Hydr aery lie Acid 229 2. Sarco-lactic Acid, which is found in many animal juices, and in the blood after death, appears to be identical with the dextro-gyrate acid just mentioned. It can readily be obtained from Liebig's extract of beef. Properties. Sarco-lactic acid is obtained as a dextro- rotatory syrup, which behaves chemically like lactic acid ; e.g. it yields lactide on heating to 140, which gives the active acid on rehydration. Its salts are laevo-gyrate ; the calcium salt is less soluble, and the zinc salt more soluble, than the corresponding lactates. 3. Hydracrylic Acid, CH 2 (OH).CH 2 .COOH, $-hydroxy^ propionic arid, ethylene lactic acid. This acid may be formed (*i) by the action of moist silver oxide on /2-iodo-propionic acid CH 2 LCL.COOH + AgOH = CH a (OH).CH,COOH + Agl (2) from ethylene chlorhydrin by the action of KCN and saponi- fication of the cyanhydrin formed ; i.e. CH 2 (OH).CH 2 C1 yields CH 2 (OH).CH 2 .CN, and that gives CH 2 (OH).CH 2 .COOH (*3) by oxidation of /?-propylene glycol ; and (4) note specially its formation from acrylic acid by addition of water, hence its name (see p. 212). Properties. It is a strongly acid, non-crystallisable syrup, and readily yields acrylic acid when heated alone (see p. 211) or with dilute H 2 SO 4 . Chromic acid or HNO 3 oxidises it to oxalic acid and CO 2 , and it is reduced by HI to /?-iodo-propionic acid. It does not yield the iodoform reaction (difference from lactic acid}, and its zinc salt is soluble in alcohol (difference from the zinc salts of lactic and para-lactic acids). Constitution of the Lactic Acids. Since the ordinary and paralactic acids are simply physical isomers, it is only necessary to distinguish chemically between lactic and hydra- crylic acid. The first of these contains a secondary alcoholic group, as shown by the formation of a ketonic acid, pyruvic acid, CH 3 .CO.COOH, when it is oxidised by potassium 230 Oxidation Products of Glycols permanganate. This is also shown by its formation from alde- hyde and HCN. These give the ethylidene cyanhydrin. which in turn yields lactic acid (see Formation 5, p. 228). This proves its constitution. On the other hand, since oxidation of hydracrylic acid yields malonic acid, CH 2 (COOH) 2 , it contains a primary alcohol group ; and its constitution is fully explained by its formation from ethylene chlorhydrin (see Formation 2, p. 229), which is itself obtainable from glycol (see p. 219). CHAPTER XXXI. OXIDATION PRODUCTS OF GLYCOLS Continued. DlCARBOXYLIC ACIDS. ON further oxidation the primary glycols yield dibasic acids, which are roughly divisible into two series, according as the carboxyl groups are attached to the same or different carbon atoms. The principal acids in each group are the following : Oxalic acid, C 2 H 2 O 4 Succinic acid, C 4 H 6 O 4 Malonic acid, C 3 H 4 O 4 Pyrotartaric acid Q^Q Iso-succinic acid, C 4 H 6 O 4 Glutaric acid Ethyl malonic acid ( C H O Adipic acid, C C H 10 O 4 Di-methyl malonic acid \ COOH Oxalic Acid, | , the first acid in the series, occurs COOH in the free state in some fungi and the juice of the chickpea, while its salts are found in many animal and plant juices. The acid potassium salt is present in wood sorrel and in common rhubarb. Calcium oxalate is found in certain urinary calculi, in many lichens, and in different parts of many plants, often occurring as crystals, CaC 2 O 4 .3H 2 O, termed "raphides." (T) Oxalic acid is formed as the product of the oxidation of many organic materials, such as starch, sugar, and cellulose, by means of nitric acid. Oxalic Acid 231 \Process. Gradually add 400 grams of nitric acid, sp. gr. 1-38, ito 50 grams of cane sugar ; heat the mixture to the boiling point, .and when the reaction is over evaporate to one-sixth of its bulk. 'Oxalic acid crystallises out, and may be purified by recrystallisation ,from water. (2) Oxalic acid is also produced by a complex reaction when starch, bran, or other vegetable substance is fused with potash, and this is the method now employed for its manufacture. Manufacture. Oxalic acid is made from sawdust, preferably that from soft woods, such as the pine or poplar. This is mixed with caustic lye, sp. gr. 135, which is made either from potash or from a mixture of 3 parts potash and 2 parts soda. Soda alone cannot be used, as it does not give a good yield. The mixture is spread out on iron plates and heated to a temperature which at first is about 200, and is never allowed to exceed 250. The mass swells up, becomes dry, and then evolves hydrogen and hydro- carbons, finally becoming dark brown in colour and entirely soluble. At the expiration of about 6 hours it forms a greyish mass, which contains about 20 per cent, of oxalic acid combined with alkalis. This product is treated with warm water, which dissolves out the .excess of alkali and the salts of potash and soda, except the difficultly soluble sodium oxalate. The sodium oxalate is de- 'Composed by milk of lime, and the calcium oxalate produced is in its turn decomposed by sulphuric acid. From the liquid obtained, after separation of the gypsum, the oxalic acid is obtained toy crystallisation. If perfectly pure oxalic acid is wanted, the impure product may be recrystallised from a 10 per cent, solution of hydrochloric acid, and then from water, or may be carefully sublimed. Oxalic acid is also formed by the following reactions, which are of theoretical importance. Thus (*3) By tne oxidation of glycol or of glycollic acid CH 2 (OH).CH 2 OH + 2 O 2 = COOH.COOH + 2 H 2 O CH 2 (OH).COOH -f O 2 = COOH.COOH + H 2 O (4) When an alkaline formate is heated to a temperature not above 400, an alkaline oxalate is produced COOK 2H.COOK = H 2 + | COOK 232 Oxidation Prodiicts of Glycols (5) When an aqueous solution of cyanogen is allowed to stand for some time, ammonium oxalate is formed CN COONH, I + 4H 2 = | CN COONH 4 While finally, (6) the production of oxalic acid when carbon dioxide is passed over a mixture of sodium and sand, heated to 360, is specially interesting COONa 2CO 2 + Na 2 = | COONa The reader should compare the last two reactions with those for the production of formic acid from HCN, and from CO 2 and potassium (see p. 138). Properties. Oxalic acid crystallises with two molecules of water in monoclinic prisms, sp. gr. 1*653 at ^r^ . These lose water of crystallisation when dried over concentrated H 2 SO 4 ; but the anhydrous acid is best obtained by carefully drying the ordinary acid at 100, and volatilising it at a temperature not exceeding 157. Oxalic acid is readily soluble in water and fairly so in alcohol, but its aqueous solutions readily decompose. It has a strongly acid taste, and is a powerful acid, e.g. it de- composes both sodium chloride and nitrate on heating, as well as many other salts. When heated quickly to a high temperature it yields formic acid and CO 2 COOH I = H.COOH + CO 2 COOH also when heated with glycerin (see p. 137). When heated with strong H 2 SO 2 it breaks up without blackening, thus COOH | = CO., + CO 4- HoO (compare Formic acid) COOH P<,O 5 , PC1 5 , and PC1 3 act similarly, and the two latter reagents Oxalic Acid. Oxalates 233 do not produce acid chlorides. Oxalic acid is a strong reducing agent ; e.g. it precipitates the metals from solutions of platinum, gold, or silver salts, for which reason it is employed as a developer in photography. It also readily reduces acid solutions of KMnO 4 and K 2 Cr 2 O 7 , and hence finds employment in volu- metric analysis. It can be itself reduced (by the zinc-copper couple) to glycollic acid. Oxalic acid finds employment in calico-printing, in various bleaching processes, in the manu- facture of certain artificial colours, as a cleansing agent, etc. The constitution of oxalic acid follows from its formation from glycol, cyanogen, and sodium and CO 2 (see Formations 3, 5, and 6). Identification. Oxalic acid may be identified by giving off CO 2 and CO when heated with cone. H 2 S0 4 , and by giving a precipitate with CaCl 2 insoluble in acetic acid. The following are the principal oxalates : Potassium Oxalate, C 2 O 4 K2.H 2 O, is a readily soluble salt finding some employment in photography. The acid potassium oxalate, C 2 O 4 HK, which is less soluble, is found in many plants, and forms with oxalic acid the quadr oxalate, C 2 O 4 HK.C 2 O 4 H 2 .2H 2 O. The two latter salts are both sold as "salts of sorrel," or "salts of lemon," and are used in the removal of iron-stains. All these salts can be prepared by suitable neutralisation of the acid with potassium carbonate. Sodium and Ammonium Oxalates are similarly pre- pared. Calcium Oxalate, C 2 O 4 Ca.H 2 O, also obtainable anhydrous, is present in many plants, and, on account of its insolubility, serves for the estimation of calcium. Ferrous Oxalate, C 2 O 4 Fe 2 .H 2 O, is used as a developer in photography. Antimony Oxalate and the double oxalate of potash and antimony find some employment in dyeing. The silver salt, Ag 2 C 2 O 4 , if quickly heated when dry, explodes. Esters of Oxalic Acid. Being di-basic, oxalic acid can produce two series of ethereal salts, acid and neutral respectively. Methyl Hydrogen Oxalate and Methyl Oxalate are both solids, and are formed when oxalic acid acts upon 234 Oxidation Products of Glycols methyl alcohol. Water saponifies them. The ethyl oxalates are liquids formed correspondingly from ethyl alcohol. Ethyl Oxalate, or Oxalic Ether, C 2 O 2 (OC 2 H 3 ) 2 , is formed by the action of dry oxalic acid on alcohol. \Process Heat together 120 grams of anhydrous oxalic acid and 80 grams absolute alcohol to 100 for 3 or 4 hours in a flask provided with a reflux condenser. Then pass in the vapour of 80 grams more alcohol while raising the temperature to 125-! 30. Properties. It is a colourless liquid, b.p. 186, sp. gr. 1-0793 at 2 e , and is readily hydrolysed by water. CONH 2 Oxamide, | , is produced when the last-named CONH 2 compound is treated with aqueous ammonia COOC 2 H 5 CONHo | + 2NH 3 = | + 2 C 2 H 5 OH COOC 2 H 5 CONH 2 and also (2) when ammonium oxalate is heated C 2 2 (ONH 4 ) 2 = CoO(NH 2 ) 2 + 2 H 2 (compare formation of acetamide from ethyl acetate and ammonium acetate, p. 182). Also notably (3) from cyanogen in aqueous solution, if a trace of aldehyde is present. Properties. It is a white crystalline solid, little soluble in water or alcohol. On heating with water to 200, or with dilute acids, it re-forms ammonium oxalate. Malonic Acid, C 3 H 4 O 4 = CH 2 (COOH) 2 , is found in beet-root juice, and is produced (i) by the slow oxidation of malic acid with potassium dichromate CH 2 .COOH COOH I + o 2 CH(OH).COOH (2) It is best prepared synthetically from cyanacetic acid by saponification with either alkalis or acids ; (cyanacetic acid is readily produced by acting upon chloracetic acid with KCN) Malonic Acid. Snccinic Acids 235 \Process. 100 grams of chloracetic acid, CH 2 C1.COOH, dis- solved in 200 grams of water are neutralised with 75 grams of K 2 CO 3 , and the solution heated with 70 grams KCN. When the reaction is over, 100 grams KOH are added ; the liquid is boiled till free from NH 3 , then acidified with HC1, evaporated to dryness, and the acid extracted by ether, from which it can be obtained by evaporating off the solvent. (3) It is also formed by the oxidation of several of the defines. Properties. Malonic acid crystallises in triclinic tables, m.p. i32-i34, and a little over this temperature decomposes into acetic acid and CO* It is readily soluble in water, alcohol, and ether. Its alkaline salts undergo electrolysis in strong solutions, with liberation of CO 2 , CO, and O, but no hydrocarbon. If heated with acetic anhydride, it gives a reddish-yellow liquid with greenish fluorescence. The constitution of malonic acid is shown (i) by its formation from cyanacetic acid, and (2) by its production when hydracrylic acid is gently oxidised. It forms acid and neutral esters, of which ethyl malonate or malonic ether, CH 2 (COOC 2 H 3 )o, is the most remarkable, and will be referred to later (see Appendix, p. 283). Succinic Acids, C 4 H 6 O 4 . There are two isomeric acids with this general formula, viz. succinic acid and isosuccinic acid. CH.,COOH 1. Succinic Acid, | , ethylene dicarboxylic acid, CHo.COOH is very widely distributed in nature, being found in the lettuce, in various varieties of wormwood, in the poppy, celandine, and unripe grapes. It frequently occurs in urine, is present in the spleen of the ox, and is found in other animal substances. It is also found in amber and fossil wood ; and the oldest method of preparing succinic acid is by the distillation of amber, hence its name (Lat. succinum, " amber "). Process. Distil amber from a retort, heat the filtrate, filter through a moist filter-paper, and evaporate to the crystallising point. The yellow crystalline product is boiled with HNO 3 , sp. gr. 236 Oxidation Products of Glycols 1*32, to free it from traces of empyreumatic oils, and recrystallised from water. Succinic acid is readily prepared (*2) by the reduction of malic acid, and of tartaric acid (monohydroxy- and dihydroxy- succinic acids), either by fermentation or hydriodic acid ; e.g. C 2 H 3 (OH)(COOH) 2 + Ho = C 2 H 4 (COOH) 2 + H 2 O C 2 H 2 (OH) 2 (COOH) 2 + 4HI = C 2 H 4 (COOH) 2 + 2H 2 O -f- 2L (3) A noteworthy synthetical formation of succinic acid occurs when ethylene dibromide is treated with KCN, and the resulting ethylene cyanide boiled with acids or alkalis (i.) C 2 H 4 Br 2 + 2 KCN - C 2 H 4 (CN) 2 + 2 KBr (ii.) C 2 H 4 (CN) 2 + 4H 2 - C 2 H 4 (COOH) 2 + 2 NH, Ethylene chloride can also be employed. ^Process. Boil an alcoholic solution of 100 grams of ethylene dibromide with 75 grams KCN till no further formation of KBr takes place, using a flask combined with a reflux condenser. Filter from the KBr, add 65-70 grams of KOH, and once more boil till the strong evolution of NH 3 ceases. Then cool the liquid, acidify with HCt, evaporate to dryness, and boil out the residue several times with alcohol. Distil off the alcohol, dissolve the crystalline residue in water, add animal charcoal, boil, and filter. Colourless crystals can then be obtained from the filtrate. (4) Succinic acid is also produced when finely divided silver acts upon bromacetic acid CH 2 Br CHo COOH 2 | + Ag 2 = | + 2 AgBr COOH CH 2 -COOH (compare the formation of C 2 H 6 from CH 3 I, p. 43); and (5) is a product of the action of HNO 3 on many organic substances, such as fats, fatty acids, wax, etc. Properties. Succinic acid forms white or colourless crystals, which belong to the monoclinic system, sp. gr. 1-55, m.p. 185. It boils at 235, decomposing into its anhydride and water, It has a weakly acid taste, is readily soluble in water, less in alcohol, and still less in ether. It is a very stable substance, not being acted upon by HNO 3 or chlorine, although KMnO 4 Succinic Acid. Brom-succinic Acid 237 in acid solution forms CO 2 . On electrolysis, hydrogen is evolved at the negative, and CO 2 and C 2 H 4 at the positive pole (see p. 54). Constitution. Since succinic acid can be prepared from ethylene cyanide, which is formed in its turn from ethylene bromide, it is evident that the acid contains the group CH 2 .CH 2 , and is best represented by the formula already assigned to it. This conclusion is confirmed by its formation from bromacetic acid by the method given. Since, too, ethylene can be built up from its elements, it is therefore evident that succinic acid can also be. Identification. Succinic acid is characterised by its irritating vapour when heated ; by yielding a reddish precipitate with FeCl 3 in neutral solutions, which decomposes on addition of NH 4 HO, giving a basic succinate ; and by giving a precipitate with BaCl 2 when alcohol and NH 4 HO are added (difference from benzoic acid}. Succinates. The salts of succinic acid differ considerably in their solubility in water. The alkaline salts are readily soluble ; the others are either almost or entirely insoluble. Haloid Substitution Products of Succinic Acid. Amongst the derivatives of succinic acid may be mentioned the mono- and di-brom-succinic acids, which are interesting as serving in the synthesis of malic acid and of tartaric acid respectively. Mono-brom- succinic Acid, C 2 H 3 Br(COOH) 2 , may be obtained by addition of hydrobromic acid to fumaric acid {p. 241) or by the action of i parts bromine and 8 parts water upon i part succinic acid at 120. It crystallises in colourless prisms, which melt at 160 and lose HBr. It forms malic acid when treated with moist silver oxide (see p. 249). CHBr.COOH Di-brom-succinic Acid, | , may be formed CHBr.COOH from fumaric acid and bromine, or when bromine acts upon succinic acid C 2 H 4 (COOH) 2 + 2 Br 2 = C 2 H 2 Br 2 (COOH) 2 + 2 HBr 238 Oxidation Products of Glycols \Process. Heat 12 grams succinic acid, 33 grams bromine, and 12 grams of water in a closed tube to i6o-i8o for six hours. The tube is allowed to cool, and the grey crystalline mass contained in it is recrystallised from hot water, being decolourised by the addition of purified animal charcoal to the solution and filtration. It forms opaque crystals little soluble in cold water, and loses HBr at 200, leaving brom-maleic acid. On boiling the silver salt with water, it yields tartaric acid (see p. 253). CC1 Succinyl Chloride, C 2 H 4 (COC1) 2 or C 2 H 4 C CQ 2 ^O, is produced when succinic acid is treated with two molecular equivalents of PC1 5 (compare Acetyl chloride, p. 157) 2PCl = H + 2POCl3 + 2HC1 This substance is an oil, which solidifies at o, b.p. 190- 200, sp. gr. 1-39. It behaves with water, alcohol, etc., as an acid chloride (compare Acetyl chloride) ; but in many of its reactions it acts as if possessing the second formula assigned to it. f*f\ Succinic Anhydride, C 2 H 4 ^^^O, is formed if the chloride is distilled with the acid, or if the acid is heated alone or with P 2 O 5 , or treated with one molecular equivalent of PC1 5 PCls = C2H + POCl3 + HC1 It crystallises in needles, m.p. 119, b.p. 261, and behaves in an analogous manner to acetic anhydride. The student should note here the formation of an acid anhydride from one molecule of an acid. Succinic Esters can be produced by the general methods illustrated (p. 161). Thus succinic anhydride reacts with ethyl alcohol to form the only known acid ester and the normal esters are produced by the action of gaseous HC1 on solutions of the acid in the alcohols. Sueeinamide, C 2 H 4 (CONH 2 ) 2 , is a white powder formed Amido-succinic Acid. Asparagine 239 from the ethyl ester by the action of aqueous ammonia (see Acetamide, p. 182); and when it is heated, a substance known as Succinimide is produced /-I TT ^CONH 2 f* TT .x^CO's^TTT , XT TT ^j^^CQNHj ~~ ^ 2tl ^^cO^ *~ 3 Succinimide is also formed when succinic anhydride is ignited in a current of NH 3 , or when ammonium succinate is distilled (compare this reaction with that which occurs when ammonium acetate is distilled with NH 3 , p. 182). It forms large efflorescent crystals, m. p. 126, b.p. 288, soluble in water and alcohol. It forms compounds with metals in which the imido (NH) hydrogen is replaced by them. This add character is characteristic of imides. Amido-succinic Acid, or Aspartic Acid CH(NH 2 ).COOH CH 2 .COOH is found in beet-root juice after treatment with lime, in vinasse, and is a decomposition product of asparagine (see below) when boiled with alkalis or acids. It contains an asymmetric carbon atom, and the naturally occurring and best-known form is optically laevo-rotatory. It crystallises in plates, little soluble in water, insoluble in alcohol. When treated with HNO 2 , aspartic acid yields malic acid C 2 H 3 (NH 2 )(COOH) 2 + HN0 2 = C 2 H 3 (OH)(COOH) 2 +N 2 + H 2 Being an amido acid, it forms salts both with acids and alkalis (compare Glycocoll, p. 184). The synthetically formed acid is optically inactive. CH(NH 2 ).COOH Asparagine, | , amido-succinamic acid^ CH 2 .CONH 2 can also occur in three forms, the ordinary form being laevo-rotatory. It occurs in germinating seeds, in the juice of asparagus, of lettuce, in the young shoots of peas and beans, and other plants, from the juice of which it can be 240 Oxidation Products of Glycols separated by crystallisation. It crystallises in prisms, is tasteless, readily soluble in water, not soluble in alcohol or ether. When boiled with alkalis or dilute acids it forms aspartic acid, and HNO 2 changes it into malic acid. 2. Iso-succinic Acid, CH 3 .CH:(COOH) 2 , methyl malonic acid, can be produced from a-chlor-propionic acid by formation of the cyanide and decomposition of that with alkalis. It cannot, however, be prepared from ethylidene bromide in that way, as ordinary succinic acid is produced. Properties. Isosuccinic acid forms colourless prisms or needles, which sublime at 100 in plates, melt at 130, and, if heated more strongly, break up into propionic acid and CO 2 (compare with Oxalic, Malonic, and Succinic acids). CH 3 .CH.(COOH) 2 = CH 3 .CH 2 .COOH + CO 2 It gives no precipitate with FeCl 3 in neutral solutions, and does not yield ethylene on electrolysis (differences from succinic acid). Adipic Acid, C 6 H 10 O 4 , is noteworthy because it is a product of the oxidation of fats. It is formed from /2-iodo- propionic acid by finely divided silver (see Succinic acid, Formation 5), and crystallises in prisms, m.p. 148. GENERAL REMARKS ON THE DICARBOXYLIC ACIDS. The formation of these acids from the glycols, from hydroxy-fatty acids, and from haloid derivatives of paraffins or of fatty acids through the cyanides, have all been illustrated, and are general methods of production, while their formation from malonic ether (see Appendix, p. 283) is of special interest. Properties. They are crystallisable solids, generally volatile, soluble in water. The two classes *of acids are differentiated on heating. Those which contain the carboxyl groups attached to one carbon atom do not yield anhydrides, but lose CO 2 , and form a fatty acid ; while those of which succinic acid is the type form anhydrides by loss of water from one molecule (difference from fatty acids). Fumaric and Maleic Acids 241 UNSATURATED DICARBOXYLIC ACIDS. Fumaric and Maleic Acids, C 2 H 2 (COOH) 2 , contain two atoms less hydrogen than succinic acid, and are physically isomeric. When malic acid is distilled it loses H 2 O, and fumaric acid remains behind, while maleic acid and its anhydride distil over C 2 H 3 (OH).(COOH) 2 = C 2 H 2 (COOH) 2 + H 2 O Fumaric acid is also formed by the action of KOH on brom- succinic acid. Fumaric acid has a very acid taste, crystallises in small prisms, is almost insoluble in water, and melts at 200, forming maleic anhydride. Maleic acid has a peculiar taste, crystallises in large prisms, is easily soluble in cold water, melts at 130, and distils at 1 60, forming the anhydride. If it is heated for some time to 130, maleic acid changes into fumaric acid. Both acids yield acetylene on electrolysis (see p. 60). SECTION V. POLYHYDRIC ALCOHOLS AND THEIR DERIVATIVES. CHAPTER XXXII. TRIHYDRIC ALCOHOLS AND THEIR DERIVATIVES. FEW of the trihydroxyl derivatives of the hydrocarbons are known, and by the rule which has already been given (p. 120) the first stable trihydric alcohol must contain at least three carbon atoms. The symmetrical trihydroxy-propane, CH 2 OH.- CHOH.CH 2 OH, known as glycerol, is actually the first of the series, and this will be taken as typical. It must not be forgotten, however, that, just as derivatives of the dihydric methylene and ethylidene alcohols exist, although they themselves are not known in the free state, so there are certain compounds which appear from their formation to be ethers of trihydric alcohols, in which the hydroxyl groups are all combined with one carbon atom. These substances are generally known as the esters of ortho- acids. Thus formic acid appears to form the compound called "ortho-formic acid," corresponding to CH(OH) 3 ; but it has not been isolated. On the other hand, its so-called esters, or, more properly speaking, its ethers, looking upon them as derived from a trihydric alcohol, are formed in the usual manner by the action of a trihaloid paraffin upon an alcoholate (compare Formation 2 of ether, p. 105). For ex- ample, ethyl " orthoformate " is formed thus CHCV+ 3 CoH 5 ONa = CH(OC 2 H 5 ) 3 + 3 NaCl Glycerol 243 and the corresponding ethane derivative, "ethyl ortho- acetate," CH 3 .C(OC 2 H 5 ) 3> is similarly produced from the tri- chlor-ethane, CH 3 .CC1 3 . Glycerol, or Glycerin, C 3 H 5 (OH) 3 , propenyl alcohol. Glycerin was discovered in the preparation of " lead plaster," formed by saponifying olive oil with lead oxide ; and occurs combined with very many different acids in various natural fats and oils. Thus it is combined with butyric acid in butter fat, with palmitic acid in palm oil and lard, and with oleic acid in olive, lard, and almond oils, it is therefore a constant product of their saponification by whatever means that is effected. It exists in combination with phosphoric acid in the brain substance, and is a constant product of the alcoholic fermentation of sugar, and so is found in beer and wine. Glycerol may be synthesised by methods identical in principle with those used and described for the mono- and di-hydric alcohols. Thus certain halogen derivatives of propane yield it by treatment with moist silver oxide, by formation of esters and saponification, or even by boiling with water; e.g. it can be obtained from tribrom-propane by the steps indicated, barium hydrate being employed to saponify the triacetate (triacetin) CHoBr CH 2 .CoH 3 0, CH 2 OH I I I CHBr gives CH.C,H 3 O,, and that yields CHOH I I I CH 2 Br CH 2 .C 2 H 3 O 2 CH 2 OH Similarly, the trichlor-propane obtained from acetone yields it on heating with water to 180 CH 2 C1.CHC1.CH 2 C1 + 3H 3 O = CH 2 OH.CHOH.CH 2 OH 4-3HC1 Mamifacture. Glycerin was originally manufactured by sa- ponifying olive oil with lead oxide ; the watery liquid remaining was freed from lead by means of H 2 S and concentrated. It is now prepared by saponifying fats under pressure with small quantities of lime (2 to 3 per cent.), the liquid being then separated from the fatty matters, and concentrated. In another process fats are heated with concentrated H 2 SO 4 244 Trihydric Alcohols and their Derivatives next boiled with water, and the acid liquid separated. The excess of acid is removed by neutralising with lime, and after the CaSO 4 has subsided the liquid is concentrated by evaporation. Crude glycerin is purified .by filtration through animal char- coal, and then concentrated in vacuum pans. To further purify this product, it may be distilled in a current of steam, or it may be crystallised. Within the last few years many patents have been taken out fcr the recovery of glycerin from ordinary soap lyes, but these are too complex for description here. Properties. Glycerol is a colourless syrup, with a sweet taste, sp. gr. 1*2624 at yfo. It boils at 290 with partial decomposi- tion, but can be distilled unchanged at diminished pressure, and also in a current of steam (see above). On cooling to o it solidifies to crystals, which melt at 20. It is very hygroscopic, and can absorb more than half its own weight of water, is miscible with water or alcohol, but is not soluble in ether or chloroform. Glycerol possesses antiseptic properties, and is note- worthy for its great solvent powers. For example, it dissolves NaOH, KOH, lead oxides, many sulphates and chlorides, and such salts as Na 2 CO 3 , alum, and lead acetate in considerable quantities, besides dissolving iodine, phosphorus, and sulphur in smaller amounts. It prevents the precipitation of ferric and copper salts by alkalis. Glycerol burns with a pale blue flame. It is readily oxidised, and when KMnO 4 is used, the formation of oxalic acid, CO 2 , and water is quantitative C 3 H 5 (OH) 3 + 3 O 2 = C 2 H 2 O 4 + CO 2 + sH 2 O Other oxidising agents yield, according to their strength, different products, including glycerose, glyceric acid, tartronic acid, racemic acid, CO 2 , and other substances. If oxidised by PbO 2 , and then bromine vapour, " glycerose " is produced, which apparently contains glyceric aldehyde. When heated alone or with dehydrating agents, e.g. P 2 O 5 , or H 2 SO 4 , it yields acrolein (p. 210). Hydriodic acid or phos- phorus and iodine form allyl iodide (p. 207), iso-propyl- iodide, etc. Tests of Purity. Glycerol finds considerable use in Glycerol. Chlorhydrins 245 medicine and the arts, and the following tests are useful : If pure, it should give no precipitate with lead acetate. It should not give a precipitate with AgNO 3 , nor a sensible precipitate with Fehling's solution, if heated with it for a few minutes to 100. It should give no colour when heated with strong H 2 SO 4 , and very little with alkalis. For the manufacture of " nitroglycerin," it is usual to test its purity by nitrating a sample under carefully fixed con- ditions. The purer the sample is, the sharper is the line of demarcation between the residual layer of acids and the " nitro- compound." Identification. On heating glycerol with concentrated H 2 S0 4 or KHSO 4 , the vapour of acrolein is evolved, known by its pungent odour. If the glycerol is in aqueous solution, saturate with KHSO 4 , and then heat. If a borax bead is moistened with glycerol or its solution (if very weak, concentrate) and heated in a Bunsen flame, the green coloration due to boric acid will be observed (ammonium salts must be absent). If equal volumes of phenol, glycerol, and H 2 SO 4 are mixed together and heated to 120, then diluted with water and NH 4 HO added, a crimson colour is obtained. Glycerol, being an alcohol, can form both ethers and compound ethers or esters. The former are of little importance, and can be obtained by ordinary methods ; on the contrary, the esters, both of inorganic and organic acids, are important. HALOID ESTERS OF GLYCEROL, OR CHLORHYDRINS. When glycerol is treated with HC1, four different substances are formed in varying quantities, viz. two isomeric monochlor- hydrins, and two dichlorhydrins, which are respectively 1. CH 2 C1.CH(OH).CH 2 OH 3. CH 2 C1,CHC1.CH 2 OH a or unsym. chlorhydrin and a or uns y m - dichlorhydrin 2. CH 2 (OH).CHC1.CH 2 OH 4. CH 2 C1.CH(OH).CH 2 C1 /3 or sym. chlorhydrin /3 or sym. dichlorhydrin The /3-chlorhydrin is also formed by the addition of HOC1 to allyl alcohol ; the a-dichlorhydrin by the action of sulphur chloride, S 2 CL, upon glycerol, and the ft compound by the 246 Trihydric Alcohols and tlieir Derivatives addition of HOC1 to allyl chloride. They are all liquid substances. Trichlorhydrin, CH 2 C1.CHC1.CH 2 C1, trichlor- propane, or glyceryl trichloride is obtained by the action of PC1 5 upon both the dichlorhydrins CH 2 C1.CHC1.CH 2 OH + PCI 5 = CH 2 C1.CHC1.CH,CJ + POC1 3 + HC1 It is a liquid, b.p. 158, and reverts to glycerol when boiled with twenty times its own volume of water. GLYCIDE COMPOUNDS. When the dichlorhydrins are treated with caustic potash or soda, they lose HC1 and form epi-chlorhydrin, or glycide chloride \/ O which is a mobile liquid with a chloroform-like taste and smell, b.p. n6'6 (cor.), sp. gr. 1-203 at . It is nearly insoluble in water, which at 100 converts it into a-chlorhydrin. Like ethylene oxide (see p. 219), it unites with NaHSO 3 , and the chlorine atom is replaceable by OH, or by acid radicles, with the respective formation of glycide alcohol, or glycide esters. GLYCEROL ESTERS OF NITRIC ACID. " Nitre-glycerin/' or Glyceryl Trinitrate, C 3 H 5 (NO,) 3 , trinitrin is the principal ester of glycerol and nitric acid, and is not, as its name would indicate, a " nitro-compound," but a real salt of nitric acid, prepared by the action of strong HNO 3 upon glycerol, concentrated H^SC^ being used as a dehydrating agent C 3 H 5 (OH) 3 + 3HN0 3 = C 3 H 5 (ON0 2 ) 3 + sH 2 O Manufacture.~A.bout 2 parts (by weight) of HNO 3 sp. gr. 1-5, and 4 parts of H 2 SO 4 sp. gr. 1-84, are thoroughly mixed and cooled. About 0-5 part of glycerol is then injected into the mixture in the form of a fine spray, and becomes immediately nitrated, while con- siderable rise of temperature occurs. The mixture is kept in constant agitation, and the temperature carefully kept below 27 Nitro-glycerin 247 while the reaction proceeds. When it is over, the mixture is allowed to stand and separate, and the nitro-glyerin is drawn off from the top and well washed, first with water and then with alkali, till the wash- water is alkaline to test paper. It is then stored, ready for conversion into dynamite. Dynamite is a mixture of nitro-glycerin and kieselguhr, the latter being a highly silicious infusorial earth which, after calcining, will absorb three or four times its weight of the nitro-compound, and retain it under pressure. Dynamite finds much more employment than nitro- glycerin, because it can be stored and handled with so much greater safety. Properties. Nitro-glycerin is a heavy, oily, and, if pure, colourless liquid, sp. gr. i'6o at 15, which, when quite pure, will keep unchanged for a very long time. Traces of im- purities, and sunlight, will start its decomposition, glyceric, oxalic, and nitrous acids being formed. It is slightly soluble in water, very soluble in alcohol, ether, and chloroform. It solidifies on cooling, forming needles which melt at about n. It has no smell, has a sweet taste, and is poisonous, small quantities producing vertigo and headache even handling it will produce these symptoms. Reducing agents, e.g. (NH 4 ) 2 S and HI, reduce it to glycerol. Potash decomposes, but does not saponify it in the ordinary manner, as HNO 2 is formed C 3 H 5 (ON0 2 ) 3 + 5KOH = KN0 3 + 2KNO., + H.COOK Potassium formate + CH 3 .COOK + 3H 2 O Potassium acetate Nitro-glycerin is a highly explosive compound, exploding with great violence when exposed to shock,- as in detonation, or when heated. It contains more than enough oxygen in itself for its own combustion ; the following equation expresses the reaction : 2 C 3 H 5 (N0 3 ) 3 = 6C0 2 + 5 H 2 + 3 N 2 + O The liability to explode on handling is much less when it is used in the form of dynamite, or when it is transformed into blasting gelatin or cordite, which are combinations of it with guncotton, camphor, etc. 248 Trihydric Alcohols and their Derivatives OXIDATION PRODUCTS OF GLYCEROL. Since the three-carbon alcohol, glycerol, contains two primary alcoholic groups, it might be expected to give by oxida- tion two aldehydes and two acids, containing one or two aldehydic or carboxylic groups. The same might be predicted of other similar trihydric alcohols. Little is known of the aldehydes (see Glycerose, p. 244); but the mono- and di-basic acids derived from glycerol are well known. The monobasic acids, which contain two alcoholic groups, may be looked upon as hydroxy-acids derived from those of the lactic series (see formation of Glyceric acid, below) ; and the dibasic acids, which contain one alcoholic group, as hydroxy- substitution derivatives of the acids of the malonic series (compare formation of Tartronic and Malic acids, p. 249). The three acids named will be the only ones considered. DlHYDROXY-CARBOXYLIC ACIDS. The first stalk dihydroxy-carboxylic acid is gly eerie acid, for though in some reactions glyoxylic acid (p. 223) appears to be dihydroxy-acetic acid, in others it acts as an aldehyde. Glyceric Acid, CH 2 (OH).CH(OH).COOH, dihydroxy- propionic acid, is formed (i) when glycerol, mixed with an equal quantity of water, is carefully oxidised by HNO 3 , sp. gr. 1-5 CH 2 (OH).CH(OH).CH 2 OH + O 2 = CH 2 (OH).CH(OH).COOH + H 2 O also (2) by acting with silver oxide upon /?-chlor-lactic acid. CH 2 C1.CH(OH).COOH + AgOH = CH 2 (OH).CH(OH).COOH + AgCl It forms an uncrystallisable syrup, readily soluble in water, is optically inactive, but is evidently a mixture of acids of opti- cally different properties. On heating to 105 for some time, it forms an anhydride. Its salts crystallise well. Tar ironic Acid. Malic Acid 249 HYDROXY-DICARBOXYLIC ACIDS. Tartronic Acid, CH(OH).(COOH) 2 , hydroxy-malonic arid, is, amongst other methods, produced (i) by oxidising glycerol with potassium permanganate CH(OH).(CH 2 OH) 2 + 2 2 = CH(OH>(COOH) a + 2H 2 also (2) from brom-malonic acid, CHBr(COOH) 2 , by the action of silver hydroxide. It is a transparent solid, which crystal- lises in large prisms, is readily soluble in water, and melts at 184, forming glycolide and CO 2 . CH 2 .COOH Malic Acid, | , hydroxy-succinic acid> is CH(OH).COOH very widely distributed in the vegetable kingdom, e.g. it is found free, mixed with other acids, in such fruits as red and white currants, raspberries, blackberries, morella cherries, unripe apples, and the berries of the mountain ash, and is present as the acid potassium salt in sweet cherries and ordinary rhubarb. It is also a constituent of the "yolk" which is found in such large quantities on wool. Malic acid is ordinarily and most easily prepared from the juice of unripe mountain-ash berries. Process. Filter the juice, almost neutralise it with lime, and boil for some time. Remove the white calcium malate which separates, with a spoon, and when no more falls out, cool the liquid, when a further amount separates. Wash with cold water, add it to boiling dilute HNO 3 (i acid : 10 water) till no more dissolves. Allow to cool, and recrystallise the acid calcium malate which separates, from water. To obtain the free acid, dissolve the acid malate in water, precipitate it by lead acetate, wash, and decompose the lead compound by H 2 S. From the syrupy solution the acid will crystallise out. Malic acid can be synthetically prepared (i) by the action of moist silver oxide on monobrom-succinic acid (compare formation of lactic acid from a-chlor-propionic acid) C 2 H 3 Br(COOH) 2 + AgOH = C 2 H 3 (OH).(COOH) 2 + AgBr This reaction yields it in an inactive form. 250 Trihydric Alcohols and their Derivatives A dextro-rotatory variety is produced (2) by partial reduc- tion of tartaric acid with hydriodic acid C 2 H 2 (OH) 2 (COOH) 2 + 2 HI = C 2 H 3 OH(COOH) 2 + H 2 O + L This form possesses opposite optical properties to that found in plants, which is laevo-gyrate ; but (3) if malic acid is formed by the action of HNO 2 on asparagine (see p. 239), its properties are identical with those of the natural acid. Properties. Malic acid exists in three optically distinct varieties, viz. the dextro- and laevo-rotatory, and the in- active forms. Of these the best known is the ordinary or laevo-rotatory variety. It forms colourless needles, sp. gr. 1*559, which have an acid taste, deliquesce in moist air, and melt at 100. It is very soluble in water, forming solutions which when dilute are laevo-rotatory, and when concentrated dextro-rotatory ; the addition of H 2 SO 4 renders the latter solu- tions laevo-rotatory. It yields, on heating to temperatures from 140 to 200, varying amounts of fumaric anhydride and maleic acid (p. 241). Malic acid is reduced by concentrated HI to succinic acid. Certain schizomycetes also reduce it to succinic and less complex acids. It prevents the precipitation of salts of copper and iron by alkalis. Constitution. The constitution of malic acid follows from its production from monobrom-succinic acid, which shows it to be hydroxy-succinic acid. Identification. There are no very characteristic qualitative tests ; however, in neutral solutions it does not give a precipitate with CaCl 2 , unless the solution is very strong, or alcohol is present (distinction from tartaric and oxalic acids). The calcium salt is soluble in NH 4 HO (difference from citric acid). Lead acetate gives a white precipitate in solutions of malic acid, best if the solution is neutralised by NH 4 HO. On heating the precipitate it partly dissolves, the rest fuses together ; it is soluble in dilute acetic acid at 60 (difference from citrate and tartrate}. Salts. The acid salts of the alkalis crystallise well, the normal salts with difficulty, and the salts of many other metals are non-crystallisable. The ammonium, calcium, and lead salts are amongst the most characteristic. Erythritol. Erythric Acid 251 CHAPTER XXXIII. TETRA-HYDRIC ALCOHOLS AND THEIR DERIVATIVES. ALCOHOLS. THE first stable alcohol which contains four hydroxyl groups also contains four carbon atoms, and is a tetra-hydroxy-butane. Erythritol, C 4 H 10 O 4 = CH 2 (OH).CH(OH).CH(QH).- CH 2 OH, or Erythrite. It is found free in the alga Protococcus vulgaris, and in erythrin a substance which occurs in orchella weed, a lichen of the species Rocella, largely used in preparing the dye orchill. This substance readily yields it on decomposi- tion with milk of lime C 4 H , + 2H2 o = C 4 H 6 (QH) 4 -f (ULx 8 ri 7 (J 3 )2 Erythritol Orsellic acid Erythrin Properties. Erythritol crystallises in large quadratic crys- tals, m.p. 112, b.p. 330, and sp. gr. 1-45. It has a sweet taste, and is optically inactive, although it contains two asym- metric carbon atoms, is very soluble in water, little in alcohol, and insoluble in ether. It does not reduce copper salts, and is not fermented by yeast. It yields, on oxidation by HNO 3 , an aldehyde-like substance, and oxalic and tartaric acids. TETRA-HYDRIC ACIDS. Since erythritol contains two primary alcoholic groups, it can yield, on suitable oxidation, two different acids one monobasic, erythric acid ; the other dibasic, tartaric acid. The trihydroxy-carboxylic acid, erythric acid, CH 2 OH.- [CH(OH)]2.COOH, is a deliquescent substance, formed by oxidising erythritol by means of platinum black. DlHYDROXY-DICARBOXYLIC ACIDS. Mesoxalic Acid, C 3 H 4 O 6 Tartaric Acid 1 r TT n RacemicAcid I 4 6 6 252 Tetra-hydric Alcohols and their Derivatives Mesoxalic Acid, C 3 H. 2 O 5 .H 2 O = C(OH). 2 .(COOH) 2 , ) Ketone alcohols or) ketoses j C 6 Hi 2 Oa CeHioOo Mannoses Fructoses (levulose) Galactoses Glucoses (dextrose) Sorbinose (2) Disaccharides (anhydrides of the saccharides) (3) Poly saccharides ... ( Cane-sugar from glucose and levulose -(Milk-sugar ,, dextrose and galactose (Maltose dextrose (Starch {Dextrin (Cellulose 262 Penta- and Hexa-hydric Alcohols 2. ACIDS. The two following acids correspond to sorbitol and glucose. Gluconic Acid, CH 2 (OH).(CHOH) 4 COOH, can be pre- pared from cane-sugar, maltose, starch, glucose, and other carbo- hydrates by oxidising them with bromine water and silver oxide. The acid, liberated from the silver salt by H 2 S, forms an uncrystallisable syrup, which is soluble in water, insoluble in alcohol. Its solutions are dextro-rotatory. When carefully oxidised with HN0 3 , it yields the corresponding dibasic saccharic acid. Saccharic Acid, COOH.(CHOH) 4 COOH, is produced by the oxidation of gluconic acid by HNO 3 or by chlorine water. It is also formed by the oxidation of dextrose, cane- sugar, starch, and other carbohydrates by HNO 3 , sp. gr. 1-15. It is a brittle, amorphous substance, deliquescent in air, soluble in water and alcohol, only slightly so in ether. It is dextro-rotatory, and reduces ammoniacal AgNO 3 with formation of a mirror. The monobasic acid related to dulcitol is lactonic acid, which may be passed over here. Mucic Acid, COOH.(CHOH) 4 COOH, is the dibasic acid formed by the oxidation of dulcitol, milk-sugar, galactose, gums, etc. It is readily prepared by oxidising i part milk- sugar with a mixture of 2 parts HNO 3 sp. gr. 1-4 and 2 parts water. On evaporation mucic acid separates in crystals, which may be washed with water and dried. It forms white tables, m.p. 2o6-2i6, almost insoluble in cold water and alcohol. It does not reduce Fehling's solution. Saccharides, Glucose 263 CHAPTER XXXV. HEXA-P1YDRIC ALCOHOLS AND THEIR DERI V A- TIVES Continued. CARBOHYDRATES. THE carbohydrates form a group of closely related substances which were originally given their name because in them the hydrogen and oxygen are present in the proportions necessary to form water. They are divisible into the following groups : 1. Saccharides, hexoses, or glucoses. 2. Disaccharides, or saccharoses, 3. Polysaccharides, which include the amyloses, i. SACCHARIDES, HEXOSES, OR GLUCOSES. The saccharides include such substances as dextrose and levulose, which are typical examples of the two classes into which these bodies are divisible, viz. the Aldoses and Ketoses. Aldoses are derived from a hexa-hydric alcohol by the oxidation of z. primary alcoholic group, e.g. CH 2 (OH).(CHOH) 4 .CH 2 OH yields CH. 2 (OH).(CHOH) 4 CHO. In ketoses, on the contrary, a secondary alcoholic group has been oxidised ; e.g. CH 2 (OH).- (CHOH) 4 CH 2 OH gives CH 2 (OH).(CHOH) 3 .CO.CH 2 OH. i ALDOSES. Glucose, C 6 H 12 O a or CH 2 (OH).(CHOH) 4 .CHO, is con- sidered to be the aldehyde of the alcohol sorbitol, and will be considered in some detail as illustrative of the aldehydes of the hexa-hydric alcohols. It occurs in three optically distinct forms. Of these ^-Glucose, or Dextrose, gr ape-sugar > is the best known isomer. It is found in very many plant and animal substances, being widely distributed in the vegetable kingdom, where it occurs along with levulose and frequently with cane-sugar. Thus it is found in grapes and in most fruits, in honey, and in a 264 Hexa-hydric Alcohols and their Derivatives combined state in many glucosides. 1 It is also present in the liver, in eggs, and in large quantities in the urine of those suffering from diabetes mellitus. It has been recently synthetically produced from com- paratively simple substances, but the processes are too complicated to detail here ; suffice it to say that the starting- point is acrolein (p. 210). It is, however, readily formed by the hydrolysis of cane- sugar by invertase ; and of sugar, starch, and cellulose by treatment with dilute acids. This latter process is com- mercially employed, and is known technically as " inversion." The equation in the case of sugar is C 12 H 22 O n + H 2 - C 6 H 15 6 + C 6 H 12 6 Glucose Levulose the mixed product being termed " invert sugar." The manu- factured article goes under various names glucose, saccharum, saccharine, and starch or corn sugar. Manufacture. Starches, rice, or maize are heated with solutions of H 2 SO 4 , HC1, or HNO 3 , containing from 0-5 to 5 per cent, of pure acid. Either open or closed vessels are used ; the latter, employed under pressure, are preferable because the time of *' conversion " is then greatly decreased. The liquid obtained is neutralised, preferably by chalk, filtered from the calcium sulphate and other insoluble impurities, decolorised, usually by filtration through animal charcoal, and concentrated in vacuum pans, from which, when it contains 82 per cent, solid matter, it is run into moulds. The impure glucose so obtained varies from white to brown in colour, according to the materials employed and the methods of manufacture. As impurities it may contain maltose, dextrin, and unfermentable substances, and may be further purified if requisite by adding crystals of anhydrous glucose to the concen- trated syrup, and so inducing crystallisation, the product being separated from the syrup by means of a centrifugal machine ; or it may be recrystallised from methyl alcohol. Preparation of Pure Dextrose. Pure dextrose may be 1 Glucosides are compound ethers which, when boiled with dilute acids, yield glucose (or some other sugar) and another body which is not a carbohydrate. Many occur in natural products. Dextrose 265 prepared from a white commercial specimen by crystallising it first from alcohol, sp. gr. 0-82, then dissolving in 8-10 per cent, of water, and adding methyl alcohol to the solution till fine crystals of anhy- drous glucose separate. Soxhlet recommends the following method for the preparation of a kilogram of glucose : mix 12 litres of alcohol, sp. gr. o'8i, with 480 c.c. strong HC1 ; heat to 45-5o, and stir in 4 kilos, powdered cane-sugar ; keep at this temperature for two hours ; then cool, and add a few crystals of anhydrous glucose and stir frequently. In about two days a large quantity of the sugar will separate. Wash it free from the mother liquor with alcohol till it is quite free from HC1, or recrystallise the precipitate from methyl alcohol. Properties. From aqueous solutions dextrose ordinarily separates in crystals with i molecule of water of crystallisation, C 6 H 12 O 6 ,H 2 O, m.p. 86; it can be obtained, however, from strong warm solutions, and also from methyl or ethyl alcohol in the anhydrous form, C 6 H 12 O,j, m.p. 146. The hydrated form loses its water at 110. Glucose is not so sweet as sugar, is readily soluble in water, but almost insoluble in absolute alcohol. When heated to 170, it passes into a body called glucosan or dextrosan, C 6 H 10 O 5 , which, on boiling with dilute acids, re-forms glucose. Sodium amalgam reduces dextrose in alkaline solutions to mannitol. Strong HNO 3 oxidises it to saccharic acid, and eventually to oxalic and carbonic acids. It is easily attacked by alkalis, espe- cially when hot, and reduces many oxides in alkaline solution either to a lower state of oxidation or to the metal. It is decom- posed by the yeast ferment, yielding alcohol and CO 2 principally, but also smaller quantities of succinic aci<4 and glycerol. Its solutions are dextro-rotatory (see p. 101). Its specific rotatory power 1 = [a] D = +527 for 10 per cent, solutions; freshly made solutions have almost double the rotatory power of old ones; on standing the normal rotation is slowly attained. Alkalis replace a hydrogen atom in dextrose, forming dextrosates, while such oxides as CaO and BaO, and salts like 1 For full explanation of the effect of sugar solutions on polarised light, a work on physics must be consulted. The determination of the specific rotation of a sugar solution in a "saccharimeter " enables us to determine its strength. 266 Hexa-hydric Alcohols and their Derivatives NaCl and NaBr combine molecularly with it to form well- defined compounds. Identification. The following tests aid in detecting the presence of dextrose: (i) It is not blackened by cone. H 2 SO 4 (difference from cane-sugar}. (2) It turns brown with alkalis. (3) If heated with NaOH, and then with basic bismuth nitrate, it readily yields a black precipitate. (4) It quickly reduces Fehling's solution 1 when heated, precipitating red Cu 2 O. (5) It gives a mirror when gently warmed with an ammoniacal solution of AgNO 3 (the silver solution is best prepared by precipitating AgNO 3 by KOH, and just redissolving the precipitate in NH 4 HO). (6) On heating glucose with a weak acetic acid solution of copper acetate, Cu 2 O is pre- cipitated (dextrin, milk^ cane or malt sugar do not give this except after long boiling}, (j) An aqueous solution of glucose boiled with NaOH gives a red colour (due to picramic acid) if a drop of picric acid solution is added. Fructose, CH 2 (OH).(CHOH) 3 .CO.CH 2 OH, is theketonic alcohol derived from mannitol. It occurs in three forms; of these ^-Fructose or levulose, fruit-sugar, occurs associated with grape-sugar in many fruits and in honey ; and is readily produced (i) along with glucose in the hydrolysis of cane- sugar. \Process. Dissolve 100 grams of sugar in 1000 c.c. of water, add 20 c.c. of HC1, and carefully invert at 60. Cool the solution to -5, and add 60 grams of slaked lime (the temperature must be down to 2) ; collect the lime compound, press, and wash two or three times with water. Suspend the precipitate in water, and decom- pose with oxalic acid or CO 2 , filter, and concentrate ; the levulose remains as a syrup. If the syrup is repeatedly treated with cold absolute alcohol, this removes the water and other impurities. Keep the residue in a closed flask, when it will eventually crystallise ; or, dissolve in hot alcohol, cool, separate from the syrupy levulose, which settles out, and allow the alcoholic nitrate to stand in a closed vessel, when it will deposit levulose in crystals. 1 Fehling's solution is prepared by dissolving 34 '632 grams of CuSO 4 , 5H 3 O, in 200 c.c. water, adding to that 173 grams of Rochelle salt in 480*0. c. of NaOH, sp. gr. 1-14, and diluting to I litre. I c.c. is reduced by 0*005 grams dextrose. Levulose 267 (2) Besides the method just given, since inulin (p. 276) is completely resolved into levulose on boiling with dilute acids, or on digestion for 20 hours with water at 100 C., it >may be conveniently employed for preparing it ; while (3) it is produced by the gentle oxidation of mannitol CH 2 (OH).(CHOH) 4 .CH 2 OH + O = CH 2 (OH).(CHOH) 3 .CO.CH 2 OH + H 2 O Properties. Levulose is generally found as a syrup, but yields silky needles (when prepared as described above), sp. gr, i '669 1, m.p. 95. When heated to 170 it loses a molecule of water, forming the anhydride levulosan. It is readily soluble in water, also in dilute alcohol ; has a sweeter taste than dextrose, being as sweet as cane-sugar. Levulose is readily attacked by alkalis and by acids, and is easily reduced to mannitol by sodium amalgam in alkaline solution. Its oxidation products vary with the agent employed ; it reduces Fehling's solution to the same extent as dextrose, but more slowly. Levulose is laevo-rotatory ; its specific rotatory power at 1 5 is [a] D =s 98-8: hence "invert sugar" is also laevo-rotatory, because the laevo-rotation of levulose is greater than the dextro- rotation due to dextrose. The following reactions show the difference in behaviour between dextrose and levulose. They both undergo fermentation with yeast, but the re- action is much slower in the case of levulose. Both com- pounds unite with HCN, and both with phenyl-hydrazine, the former with either one or two molecules of the reagent, the latter with two molecules, the osazones thus formed being identical. They both show alcoholic characters ; e.g. both give a penta- acetyl derivative when treated with acetic anhydride and ZnCl 2 , and therefore both show the properties of penta-hydric alcohols j but dextrose readily yields on oxidation acids con- taining the same number of carbon atoms, while levulose is less easily oxidised, but gives acids containing less carbon than it. These results are in accordance with the assumption 268 Hexa-hydric Alcohols and their Derivatives that dextrose is an aldehydic and levulose a ketonic alcohol, as shown by the formulae given. 2. THE DISACCHARIDES OR SACCHAROSES. These substances are ether-like anhydrides, derived from the saccharides by the elimination of water from two molecules of them. Sufficient is not known to enable us to decide definitely which groups interact in forming the new molecule, but the fermentable sugars are supposed to retain an aldehyde or ketone group intact. They undergo hydrolysis when warmed with dilute acids. Cane-Sugar, C 12 H 22 O n , Saccharon, or Sucrose, is very widely distributed in the vegetable kingdom. Considerable quantities are present in the juice of the sugar-cane (16 per cent.), in the sorghum, in the sap of palms, limes, and maples, especially the sugar maple, and in beet-root (7-14 per cent.) Besides these substances, it is found in moderate quantities in many fruits, generally accompanied by invert sugar. It is doubtful if it has been synthetically prepared. Manufactitre. The manufacture of cane-sugar varies with the source of the sugar. 1. It is made from the sugar-cane by the following or some similar process : The juice, extracted from the ripe canes by crushing them, con-' tains about 20 per cent, of sugar mixed with impurities. It is very liable to ferment, and is strained at once into the clarifier, where it is treated with sulphurous acid, then neutralised with lime and defecated by heating to 75-8o, when a scum separates and is skimmed off. This treatment is repeated on the clarified liquid until it has a sufficient degree of consistency to be run into moulds, where it crystallises. 2. In making sugar from beet-roots, they are sliced, and then systematically lixiviated by warm water of gradually increasing temperature in a series of vessels termed diffuse, a strong solution finally being obtained. From 0-5 to 3-0 per cent, of lime is added to this liquid, which is boiled ; the clear juice is decanted into another vessel, where it is freed from excess of lime by passing in CO 2 . The CaCO 3 formed is allowed to settle, and carries down with it other impurities. The above operations are repeated, and Cane-sugar 269 the liquid, after filtering, is passed through animal charcoal or treated with SO 2 and filtered through sand to decolourise it. It is then evaporated down to sp. gr. 1*15 in vacuum pans, once more filtered through charcoal, and evaporated to the crystallising point. The brown liquid remaining when the sugar crystallises out is termed molasses, or treacle, and contains a large quantity of sugar, which formerly was not recoverable. It is now recovered, amongst other ways, by forming strontium saccharosate, separating it, decomposing it by CO 2 , and crystallising the sugar remaining. Refining Sugar. The raw sugar obtained by the two methods described, when required quite white as " lump " or " granulated " sugar, is dissolved in water, filtered, decolourised by filtration through charcoal, or by treatment with SO 2 , and boiled down in a vacuum pan till crystallisable, the subsequent treatment depend- ing on the form in which it is required. Properties. Pure cane-sugar is a transparent solid, which crystallises in monoclinic prisms. Its sp. gr. is i'S93 at 2^.-. It is insoluble in ether, almost so in absolute alcohol, readily soluble in water, and also soluble in dilute alcohol in quantities which are not proportionate to the amount of water present, weak solutions dissolving more and strong ones less, than might be expected. Its solutions are dextro-rotatory [a] D at 20 being +64*1. It melts at i6o-i6i, and does not crystallise again on cooling. If kept just above its meltin.g point for some time it breaks up, forming dextrosan and levulo- san; at i90-20o it turns brown and then black, and forms caramel used for colouring purposes. If heated with water in closed tubes to 160 it is decomposed, CO 2 , formic acid, and charcoal being formed. Boiling with water does not decom- pose it, but if a small quantity of some acid (especially mineral acids) is present, it is decomposed or "inverted" into an equi-molecular mixture of dextrose and levulose. This inversion takes place slowly in the cold, and CO 2 is sufficient to produce it. Strong acids differ in their action; HNO 3 of 1*3 sp. gr. oxidises it with the production of saccharic, tartaric, and oxalic acids, while a mixture of strong HNO 3 and H 2 SO 4 forms the explosive tetra-nitrate. Strong H 2 S0 4 has only slow action 2/o Hexa-hydric Alcohols and their Derivatives on dry cane-sugar, but if added to a thick syrup rapid heat- ing takes place, SO 2 is evolved, and a semi-solid carbon- aceous mass results. Cane-sugar combines with bases, e.g. CaO, SrO, BaO, to form saccharo sates. Cane-sugar is not directly fermentable by yeast, but is hydrolysed by the enzyme invertase produced by it, and the invert sugar formed then ferments. It forms an octo-acetate when heated with sodium acetate and acetic anhydride, which proves the presence of eight hydroxyl groups in it, but its constitution is not yet established, though it is evidently an anhydride of dextrose and levulose. Identification. The following reactions are useful. A solution of cane-sugar does not turn brown when boiled with alkalis, nor give the smell of burnt sugar when afterwards acidified. Fehling's solution has no action in the cold, and on boiling for a minute or two the reduction is only slight (difference from dextrose']. If, however, a solution of sugar is heated for a minute with a few drops of cone. HC1, and then neutralised with KOH, on addition of Fehling's solution dextrose may be detected. Ammoniacal silver nitrate solution is not reduced by heating with sugar solutions, but on addition of NaOH, a silver mirror is formed. The reaction with H 2 SO 4 may also be noted. , . Maltose, or Malt- Sugar, C^H^On.HoO, maltobiose, is found in some glucoses and beers; it often occurs in the intestinal canal and in urine. Certain ferments which act on glycogen produce it, and it is yielded by the action of sul- phuric acid upon starch. It is also formed, along with dextrin, from the starch present in grain, by the action of the ferment diastase 3C 6 H 10 5 + H 2 = QaHaOu + C 6 H 10 O 5 Process. Make 100 grams of starch into a paste with 2300 c.c. of water ; cool down to 60 C, and mix with it 20 grams of air- dried malt, or the extract from that. Keep the mixture at 6o-65, for four hours, cool, allow to stand for a fe\^days, evaporate down in vacuo, and boil the residue with 2 litres of alcohol, sp. gr. 0*820. Decant the clear liquid, and put on one side for a week in a corked flask, when a crust of crystallised maltose will form on the side of the flask. The crystals may be purified by recrystallisation from either methyl or ethyl alcohol. Maltose. Lactose 271 Properties. Maltose crystallises in fine needles, sp. gr. o'Sio, which become anhydrous at 100. The anhydrous substance is little soluble in either methyl or in ethyl alcohol ; the hydrated form is readily soluble both in them and in water. Its solution is dextro-rotatory, [a] D = + 140 at 15*5. Maltose undergoes no further change by the action of diastase, but is hydrolysed with formation of dextrose (compare Cane-sugar) by the pancreatic secretion, and by other ferments C 12 H 22 O n + H 2 O = 2C 6 H 12 O 6 It is also hydrolysed by dilute inorganic or organic acids, although not so readily as cane-sugar. It is capable of direct fermentation by yeast. When boiled with HNO 3 , it yields saccharic and oxalic acids ; chlorine and bromine oxidise it to malto-bionic acid; heated with sodium acetate and acetic anhydride, it yields an octo-acetate. Malt sugar reduces Fehling's solution, but only to about two-thirds the extent of dextrose, and it differs from that body by being less soluble in alcohol, and not reducing a solution of CuA 2 made acid with acetic acid. Maltose is evidently an anhydride of dextrose, and probably contains an unchanged aldehyde group. Lactose, or Milk-Sugar, C^H^On-HaO, lactobiose, is present to the extent of 5-8 per cent, in human milk, and in varying amounts in that of other mammals. It is also found in some other animal fluids, and is said to occur along with cane-sugar in the sap of a West Indian tree, Achras, sapota. According to Demole, its octo-acetate can be synthesised by boiling a mixture of dextrose and galactose with acetic anhydride ; this is, however, denied by other observers. Manufacture. Milk-sugar is prepared for commercial purposes by evaporating whey to dryness. The residue is dissolved in water along with a small quantity of alum, filtered through animal charcoal, evaporated to a syrup and crystallised. It may be purified by dissolving it in water, and reprecipitating it by the addition of alcohol. Properties. Lactose forms white, semi-transparent, rhombic crystals, sp. gr. 1*534 at 3'9- It * s I GSS sweet and less soluble 272 Hexa-hydric Alcohols and tticir Derivatives in water than cane sugar. It is insoluble in alcohol and in ether. It crystallises (from water) with one molecule of water of crystallisation, which it loses if heated to 130; at 180 it forms lacto-caramel, C^H^O, and above that it melts to a brown mass. Its solutions differ in rotatory properties according to their source; it is, however, dextro-rotatory, and normally [a] D = +52-53 at 20. Pure yeast has no action upon it, although other organisms ferment it, producing alcohol and lactic acid. When heated ' with water to 170, milk-sugar decomposes with separation of carbon, formic acid, and CCX (vide Cane-sugar, p. 269). It turns brown when heated with alkalis, similarly to dextrose j organic acids have little effect, except when boiled with it, though oxalic acid does not act on it even at 100 (difference from cane-sugar) ; dilute mineral acids hydrolyse it, with formation of galactose and dextrose. Concentrated H 2 SO 4 has no action upon milk-sugar till heated with it. Dilute HNO 3 oxidises it to mucic and saccharic acids ; con- centrated HNO 3 forms nitrates. Lactose prevents the pre- cipitation of metallic oxides by means of caustic alkalis, readily reduces Fehling's solution, yields a silver mirror with ammo- niacal silver solutions, but does not reduce Barfoed's solution (CuA 2 + HA). If it is boiled with a solution of lead acetate, and AmHO is then added, a precipitate is obtained which is first yellow and then copper red. Lactose forms, like the other sugars, an octo-acetate, and by several of its reactions may be shown to be an anhydride of galactose and dextrose, in which the aldehyde group of the dextrose remains intact. Polysaccharides. Starch 273 CHAPTER XXXVI. CARB OH YD R A TES Continued, 3. THE POLYSACCHARIDES. MUCH less is known about the constitution of these substances than of the other saccharides. As far as we know, their constitution is very complex, and their molecular weight great. Starch, (C 6 H 10 O 5 ) n , where n is probably 100 at least, amylum^ occurs in varying quantities in many different parts of plants, such as the leaves, stems, flowers, fruit, and roots. It is formed in the chlorophyll cells sugars probably being first formed and it serves as a reserve food for the plant. Starches, such as sago, tapioca, and those in grain, are im- portant as food for men and animals. The following numbers show the approximate amounts present in different substances : wheat, 55 ; barley, 45 ; rice, 75 ; peas and lentils, 39 ; potatoes, 16-23 ; yams, 25 parts starch per cent. Mamifacture. The principal substances used in the manu- facture of starch are wheat, maize, rice, and potatoes ; and the following is a short description of the processes employed : In the simplest and oldest method, the grain is softened by soaking, next crushed, and the starch then washed out by frequent treatment with water. The milky liquid, which contains the starch along with a quantity of gluten, is allowed to stand until the latter is destroyed by fermentation. The supernatant liquid is then drawn off, and the starch washed by frequent stirring up with water, allowing the mixture to settle, and drawing off the wash- water. In another method flour is employed ; this is made into dough, is then washed on sieves and in centrifugal machines till free from starch, which is purified by washing with weak caustic soda, and then with water till free from alkali. To prepare starch from potatoes, these are ground to pulp and then washed in centrifugal machines or on sieves, with water made acid with H 2 SO 4 . The starch so obtained is purified similarly to that just described. Experiment 16. Make 100 grams of flour into a stiff paste, T 274 Carbohydrates wrap it in a piece of calico and knead it in water. Notice that the water becomes milky in appearance, and, if allowed to stand, deposits a white sediment, while the gluten remains behind in the calico. Boil part of the sediment with a little water, and apply the tests for starch given below. Also examine some of it with a microscope, using a -inch objective. The granules obtained by cutting a slice off a potato and smearing a microscope slide with it may also be examined. Properties. Starch is a white lustrous powder, sp. gr. dry varying from i'56 to 1*65, and, with the exception of that from potatoes, is without taste or smell. This powder consists of minute granules (Fig. 45). The granules from different sources differ characteristically in appearance and size. They each consist of a nucleus or hilum, surrounded by concentric layers, which are made visible by treatment with dilute alkali. They have the power of polarising light, and so yield characteristic effects when ex- amined by polarised light. The largest granules are those from tous les mois or potatoes, 0-175 mm. and 0-140 mm. in diameter respectively ; the smallest are from beet-root starch, 0*0004 mm - m diameter. If the granules are entire, starch is insoluble in cold water, but when treated with boiling water the granules swell and burst ; the cell-walls (starch cellulose or farinose) remain in- soluble, while the cell-contents (gramtlose) go into solution. Air-dried starch contains 18-20 per cent, of moisture, and, if carefully dried, may be heated to 160 without change ; at a higher temperature it undergoes change, with partial formation of dextrin. If starch paste is boiled with dilute alkalis, or if starch is heated to 190 with glycerol, " soluble " starch is produced. Boiling dilute acids convert starch into dextrin and maltose, and finally dextrose. Strong HNO 3 forms first saccharic acid, and then oxalic acid ; while fuming HNO 3 mixed with cone. H 2 SO 4 nitrates it. Many unorganised ferments (enzymes) possess the power of liquefying starch ; the action of diastase is note-worthy (see Dextrin, p. 276). Identification. Iodine gives, with moist starch or cold starch Starches 275 Q <0 o < 0* f n ^ FIG. 45. i. Maize. 2. Wheat : (b) side view ; (c) cracked from desiccation. 3. Oat: compound grains and (a) single granules. 4. Potato: (a) hilum ; (b) compound granule. 5. Rice. 6. Bean. 7. West Indian arrowroot. 8. Tous les mois. 276 Carbohydrates paste, a blue colour, which disappears when heated and reappears when cooled. This is a very delicate test for its presence. Bromine colours starch an orange-yellow. Inulin, (C 6 H 10 O 5 ) M , a polysaccharide found in dahlia roots, in chicory, and other plants, is a white powder, which is remarkable for its ready transformation into levulose (see p. 267). Glycogen, or animal starch, (C 6 H 10 O 5 ) W , is found in many animal tissues, but especially in the liver. It is a white meally powder, soluble in water, is dextro-rotary, and is coloured red by iodine. Diastase forms maltose, and dilute acids dextrose. Dextrin, (C 6 H 10 O 5 ) n , Sullivan's fi-dextrin Hi. This term has been used to denote a mixture of substances obtained by the action of heat and various reagents upon starch; that obtained by the action of diastase upon starch will now be described. Dextrin is said to be present in plant-sap, in seeds, probably in the juice of horseflesh, in beer, and is prepared artificially (i) by the action of heat alone, (2) by heat assisted by small quantities of acid, or (3) by the action of diastase (malt extract) on starch 3 C 6 H 10 5 + H 2 = C^H^Ou + C 6 H 10 5 Maltose Dextrin Process. The residue left in the preparation of maltose (p. 270) is repeatedly exhausted with alcohol, then dissolved in water, and alcohol added till one-eighth of the dissolved substance is precipi- tated ; this is filtered off, and pure alcohol added to the nitrate, when pure dextrin is precipitated. It may be purified by re-solu- tion and reprecipitation. Manufacture. Commercially, the various forms of dextrin, such as dextrin, British gum, starch gum, etc., are prepared (i) by heating well-dried starch to 2i2-275 in suitable apparatus. Different starches yield distinct products at the same temperature, and the lower the temperature the slower the transformation, but the whiter the product. (2) If the starch is moistened before drying with very dilute nitric acid, and then heated to no-i2O, dextrin is readily obtained. (3) The dextrin syrups are manu- factured by the action of diastase or sulphuric acid on starch. When prepared by the former, maltose is always present, and dextrose in the latter case. These dextrins are employed as gum substitutes and in the manufacture of beer. Dextrins 277 Properties. Dextrin is an uncrystallisable, glassy, colour- less substance, which can be rubbed down to a white powder. It dissolves in water to a neutral syrup, from which alcohol reprecipitates it. Its solutions are dextro-rotatory [a] D = + 200-4 for a 10 per cent, solution. It is not fermentable by yeast, except in the presence of diastase, which converts it into maltose. Dilute mineral acids act upon dextrin as upon starch. Identification. The reactions of dextrin are not very character- istic. It does not reduce Fehling's solution, or only slightly so, and is precipitated from its aqueous solutions by the addition of alcohol (difference from dextrose]. It is not coloured by iodine (difference from starch}. The isomeric or polymeric dextrins are similar to that just described. They are white substances readily soluble in water, and all possess the same specific rotatory power [A] D = + 200-4. They differ from dextrin by being fermentable. Cellulose, (C 6 H 10 O 5 ) n , or some modification of it, forms the principal portion of most plant structures. In its purest natural form we know it as raw cotton, which consists of the vegetable hairs surrounding the seeds of the cotton plant. This yields on purification practically pure cellulose, the only impurity present being a trace- of mineral matter, which leaves o'i to 0*2 per cent, of ash. Process of Purification. Treat cotton wool frequently in alternation with cold bromine water (bromine has no action on cellulose) and boiling dilute ammonia till nothing more is removed by the alkali. Then wash it successively with dilute acid, water, alcohol, and ether, and dry. Properties. Pure cellulose is a white semi-transparent colloidal substance, of sp. gr. i -45. It usually contains about 7 per cent, of moisture, which is, however, probably water of hydration. It is insoluble in all ordinary solvents, but it dis- solves in cuprammonia (Schweitzer's reagent), 1 from which it may be reprecipitated by dilute acid. The soluble compound 1 This may be prepared by dissolving well-washed copper hydrate in the least possible quantity of strong ammonia. 278 Carbohydrate, produced is said to be (C 6 H 10 O 5 ) 2 .Cu(NH 4 ) 2 O. It is also soluble in a hydrochloric acid solution of zinc chloride, of sp. gr. 1*44. Dilute potash or soda have little or no action upon it, but if concentrated they profoundly modify the structure of the fibre, forming C 1 aH a9 Q w .Na,O. Dilute acids have little action at ordinary temperatures, but destroy it on heating. Strong H 2 SO 4 dissolves cellulose with the formation of acid sulphates. Strong HNO 3 , either alone or with cone. H 2 SO 4 , forms nitrates (see Nitro-cellulose, below). Cellulose is slowly disintegrated by H 2 SO 4 of 1*35 sp. gr., or HNO 3 of 1*3, but a toughening first occurs. This reaction is employed to form parchment paper, and may be shown as follows Experiment 17. Pass strips of filter-paper rapidly through a mixture of 3 parts strong H 2 SO 4 , and I part water ; wash at once in dilute ammonia, and then in water, and note the increased strength of the paper. Moist chlorine oxidises cellulose, bromine has no effect upon it, and iodine gives no colour ; but hypochlorites attack it, producing oxycellulose, which is remarkable for its affinity for vanadium compounds. Identification. Though cellulose gives no reaction with iodine alone, after treatment with a dehydrating agent a blue colour is obtained. A useful reagent is a mixture of 90 parts of ZnCl 2 solu- tion, sp. gr. 2, 6 parts of KI, and 10 parts of water, with a little iodine dissolved in it ; this gives a blue colour when applied to cotton or other form of cellulose. Or cotton may be rubbed with a mixture of 3 parts strong H 2 SO 4 , 2 parts glycerol, and I part water. If a drop of dilute iodine solution is then applied, the blue colour is obtained. Cellulose Nitrates, nitro-celluloses or pyroxy lines. Cellulose contains hydroxyl groups, and when treated with strong nitric acid, under suitable conditions, nitrates are easily formed. These contain a varying number of (NO 3 ) groups according to the conditions of the experiment. Of these, the hexa-nitrate forms gun-cotton, and the tri- and tetra- nitrates are used for making collodion. These nitrates have certain common properties : many reducing agents reconvert Gun-cotton. Collodion 279 them into cellulose ; alkaline solutions remove the nitric acid radicle, i.e. they are saponified ; on boiling with HC1 and FeSO 4 their nitrogen is given up as nitric acid ; and all are more or less explosive. Gun-cotton, Ci 2 H 14 (NO 3 ) 6 O4, is prepared by treating cotton with a mixture of 3 parts HNO 3 , sp. gr. 1-5, and i part H 2 SO 4 , sp. gr. 1*84, for twenty-four hours. The temperature must not exceed 10, and the product is afterwards thoroughly washed free from acid. This body is insoluble in alcohol or in ether, or in a mixture of them, and slowly soluble in acetone. It is hardly distinguishable from cotton in appearance, gives no blue colour with iodine, and is insoluble in cuprammonia. It burns quietly when ignited, but explodes violently by percussion, especially if compressed. It is not affected by water, and therefore can be stored in a wet condition, and is quite safe if thoroughly free from acid. Collodion is composed of a mixture of tri- and tetra- nitrates, prepared by nitrating cellulose at a higher tempera- ture and with weaker acids, and differs from gun-cotton by being soluble in ether-alcohol. APPENDICES 1. Calculation of Percentage Composition. Extra Example. 0*3636 gram of caffeine yielded 0*6601 gram of CO 2 and 0*171 gram of water ; also 0*1283 gram yielded, when analysed by Will and Varrentrap's process (p. 19), 0*2613 gram of platinum. The percentage amount of carbon present (see p. 24), is 3 ico 0*660 1 x x ^^ *= 4Q'5o i r 0-3636 The percentage amount of hydrogen present (p. 24), is I 100 0*171 x - x 7 7 = 5*22 9 0*3636 Since in the formula of (NH 4 ) 2 PtCl 6 one atom of carbon corresponds to two atoms of nitrogen 195 grams Pt correspond to 28 grams N .*. i gram Pt corresponds to gram N and 0*2613 Pt , to ** x 0*2613 gram N J 95 But that amount of nitrogen was present in 0*1283 gram caffeine ; the percentage amount present will therefore be 28 100 x 0*2613x^^ = 29-44 The percentage amount of oxygen will be, "by difference, 16*04. 2. Aceto-acetic Ester, or Ethyl Aceto-acetate, and. its Derivatives. These compounds have proved very important in the synthesis of fatty acids and ketones. The methods of their preparation, and their decompositions, will accordingly be described. To prepare ethyl aceto-acetate the following process may be used : 1000 grams of carefully dried ethyl acetate are treated with 100 grams of sodium in small pieces, and after the first reaction is over the mixture is heated, in a flask with a reflux condenser 282 Appendices attached, till the sodium is dissolved. 550 grams of 50 per cent. acetic acid are added, and, when the mixture is cool, 500 c.c. of water. The oily layer that separates is washed with water and fractionated, and about 175 grams of a liquid boiling at about 180 may eventually be obtained. The reactions may be thus repre- sented 2CH 3 .COO(C 2 H 6 ) 4- Na 2 = CH s .CO.CHNa.COO(C 2 H 6 ) Sodio-aceto-acetic ester + C 2 H 5 ONa + H 2 CH 3 .CO.CHNa.COO(C 2 H 6 ) + CH 3 .COOH = CH 3 .CO.CH 2 .COO(C 2 H 5 ) + CH 3 .COONa Aceto-acetic ester The ester is a neutral liquid with a fragrant odour, b.p. 181, slightly soluble in water, readily in alcohol. It yields a violet-red colour if FeCl 3 is added to its aqueous solution. If it is decom- posed by cold KOH it is saponified, and free aceto-acetic acid can be obtained by acidification with dilute acids and extraction with ether. If the ester is dissolved in absolute alcohol, and an equivalent amount of sodium added, hydrogen is liberated, and the sodio-derivative is formed ; if to this solution an alkyl iodide is added and heat applied, the sodium is replaced by the alkyl group. If the treatment with sodium alcoholate and the iodide is repeated, a second hydrogen atom can be displaced. Thus, according as one or two hydrogen atoms are replaced, compounds of the following types are formed : CH 3 .CO.CH(CH 3 ).COO(C 2 H C ) and CH 3 .CO.C(CH 3 ) 2 .COO(C 2 H ) in which the methyl group may be replaced by other similar radicles. Free aceto-acetic acid breaks up readily, when heated, into acetone and CO 2 CH 3 .CO.CH 2 .COOH = CH 3 .CO.CH 3 + CO 2 The esters and their alkyl derivatives may be broken up in two ways, yielding ketones and acids as the respective results. If they are heated with dilute KOH, or if they are boiled with H 2 SO 4 , or with HC1 (i part acid to 2 parts water), CO 2 is split off and ketones are formed ; e.g. CH 3 .CO.CHJCOO(C 2 H 5 ) + 2KOH = CH 3 .CO.CH 3 . + K 2 CO a + C 2 H 5 OH CH 3 .CO.CH(C 2 H 5 ) :COOC 2 H 5 + 2KOH = CH 3 .CO.CH 2 .C 2 H 5 4- K 2 CO 3 4- C 2 H 5 OH Appendices 283 If concentrated alcoholic KOH is employed, the reaction differs, acids being produced ; e.g. CH 3 .CO.;CH 2 .COO(C 2 H 5 ) + -KOH = CH 3 .COOK + CH 3 COOK + C 2 H 5 OH CH 3 .COC(CH 3 ) 2 .COOC 2 H 5 + 2KOH = CH 3 .COOK + CH(CH 3 ) 2 .COOK +C 2 H 5 OH The cleavage of the molecule occurs as indicated by the dotted lines. It will thus be recognised that these reactions furnish us with valuable means of readily synthesising from ethyl aceto-acetate either fatty ketones or fatty acids, whose compositions will vary according to the alkyl groups introduced. If the sodium compounds are treated with halogen derivatives of esters, then acid derivatives are obtained which decompose similarly to the alkyl compounds, but yield acids of the succinic series. Thus monochlor-acetic ester CH,,C1.COO(C 2 H 5 ) produces CH 8 .CO.CH(CH 2 .COOC 2 H fi ).COOC 2 H 6 which breaks up and gives succinic acid CH 3 .CO.'iCH(CH 2 .COOC 2 H 5 ).COOC 2 H 5 + 3 H 2 = CH 3 .COOH + C 2 H 4 (COOH) 2 + 2C 2 H 5 OH 3. Ethyl Malonate, or Malonic Ester, CH 2 (COOC 2 H 6 ) 2 , can be prepared by passing HC1 gas into a solution of cyanacetic acid in absolute alcohol, or by the following process : Dissolve 125 grams of chloracetic acid in 250 c.c. of water and 93'5 grams of K 2 CO 3 ; add 87^5 grams of KCN, and heat to start the reaction. As soon as the action is over, evaporate the liquid down over a sand-bath till its temperature is 135. Then cool, add the mass to two-thirds its weight of absolute alcohol, and pass in HC1. Pour the product into ice-water, extract with ether, dry over CaCl 2 , and distil. It is a liquid with a faintly aromatic odour, b.p. 195. It resembles ethyl aceto-acetate in containing a CH 2 group, the hydrogen of which can be replaced successively by sodium and by alkyl radicles, thus yielding substituted malonic esters. From these the free acids can be obtained, and as they (like malonic acid itself) lose, when heated, a molecule of CO 2 and yield fatty acids, we have another method of synthesising higher fatty acids. Thus C(C 2 H 6 ) 2 (COOC 2 H 5 ) 2 yields C(C 2 H 5 ) 2 (COOH) 2 , which in turn gives on heating CH.(C 2 H 5 ) 2 COOH + CO 2 . 284 Appendices 4. Oxidising Agents. The following are some of the princi- pal substances employed in oxidising organic compounds. 1. There are cases in which free oxygen acts upon readily oxidisable substances, especially in presence of spongy platinum ; thus alcohol can be oxidised to aldehyde, and then to acetic acid. 2. Chromic Acid itself, or a mixture of K 2 Cr 2 O 7 along with either H 2 SO 4 or acetic acid, is often employed. For the oxidation of alcohols a solution of 3 parts K 2 Cr 2 O 7 , i part H 2 SO 4 , and 10 parts water is useful ; for hydrocarbons stronger solutions may be employed. One molecule of the salt yields three atoms of oxygen, and the equation may be represented as K,Cr,0 7 + 4H 2 S0 4 = K 2 SO 4 + Cr 2 (SO 4 ) 3 + 4H 2 O + 3 O 3. Nitric Acid, sp. gr. 1*4, diluted with 2 volumes of water may frequently be employed, the amount of oxygen yielded being dependent upon the conditions of the experiment. It is also employed in the concentrated form. 4. Potassium Permanganate is used both in alkaline and in acid solution. In the first case two molecules of the salt yield three atoms of oxygen ; in the second they give five atoms 2KMnO 4 -i- 3H 2 O = 2Mn(OH) 2 + 2KOH + 30 2KMnO 4 + 3H 2 SO 4 = K 2 SO 4 + 2MnSO4 + 3H 2 O + 50 The action of the H 2 SO 4 upon the oxide of manganese explains the increased amount of oxygen in the second case. Manganese Dioxide (or, at a higher temperature, lead dioxide) can be employed along with H 2 SO 4 MnO 2 + H 2 SO 4 = MnSO 4 + H 2 O + O 5. Chlorine and bromine both act as oxidising agents in presence of water C1 2 + H 2 O = 2HC1 + O 6. Silver Oxide is also employed for oxidising aldehydes (see Formation of acrylic acid), while 7. Potassium Ferricyanide in alkaline solution is a mild oxidising agent 2K 3 FeCy 6 + 2KOH = 2K 4 FeCy 6 + H 2 O + O . 5. Reducing Agents. i. At a high temperature hydriodic acid acts as a powerful reducing agent, and is frequently employed to reduce polyhydric alcohols ; when a large excess is used, it is possible to reduce acids to hydrocarbons. 2. Sodium, either alone or as sodium amalgam, when acting Appendices 285 in alcoholic or in moist ethereal solution, is a very powerful reagent Na 2 + 2H 2 O = 2NaOH -1- H 2 3. Zinc may be used either in acid or in alkaline solution Zn + 2HC1 = ZnClg + H 2 Zn + 2KOH = Zn(OK) 2 + H 2 Zinc dust (a mixture of Zn and Zn(OH) 2 ) is frequently employed. Difficultly reducible substances are often heated to a high tem- perature with zinc dust alone. 4. Iron and tin are also employed along with acids, and it should be noted that the FeCl 2 and the SnCl 2 formed from these metals and HC1 are themselves reducing agents. In presence of readily reducible substances, SnCl 2 reacts as follows : SnCl 2 + 2HC1 = SnCl 4 + H 2 Besides the above-mentioned reagents, 5. Sulphuretted hydrogen finds some employment in ammoniacal solution ; and 6. Sulphur dioxide in aqueous solution. INDEX The figures in black type indicate the principal reference ', where more than one is given. ACE ARS CAR ACETAT., 130, 221 Alcohols, nomenclature of, 80 Arsonium compounds, 177 Acetaldehyde, 124 , oxidation products of, Asparagine, 239 hydrazone, 129 96 Aspartic acid, 239 Acetaldoxime, 129 , isomerism of, 79 Az'jlmic acid, 188 Acetals, 221 Aldehydes, 39, 12O Acetamide, 182 Acetates, 144 Acetic acid, 39, 139 , constitution of, 145 , haloid substitution de- and their derivatives, 120 , general remarks on, 128 , unsaturated, 209 Aldol, 127, 128 Aldoses, 263 BACTERIUM lactis, 227 Barfoed's solution, 272 Beer, manufacture of, 91 Benzene, 46 rivatives, 147 aldehyde, 124 Aldoximes, 126, 129 Alkyl radicle, definition of, 47 Boiling-point, determination of 10 anhydride, 39 ether, 160 Aceto-acetic ester, 281 Acetonamine, 135 Acetone, 133 hydrazone, 134 Aceto-nitrile, 193 Acetoxime, 134 Alkylenes, 52 Allene, 63 Allyl alcohol, 207 , esters of, 209 iodide, 207 ' iso-thiocyanate, 209 mercuric iodide, 207 mustard oil, 209 Bonds, 35 Brom-ethylene, 206 Bromoform, 75 Brom-succinic acid, 237 Butaldehyde, 120 n-Butane, 49 Butanes, 48 Buffer 1-1 I*i4 Acetyl bromide, 158 chloride, 39, 157 iodide, 158 sulphide, 209 Allylene, 63 Amido-acids, 181 uner, 153* AOT* n-Butyl alcohol, 99 Butyl alcohols, constitution Acetylene, 59 derivatives, 214 series, 59 , general remarks Amido-base, defined, 163 succintc acid, 239 Amine, defined, 163 Amines, 39, 163 of, 100 Butylenes, 58 n-Butyric acid, 150 Butyric acids, 150 on, 62 , diagnosis of, 168 Acetylenes, true, 59 , general remarks on, 169 CACODYL, 175, 176 Acid amides, 181 Ammonium bases, 163 chloride, 175 , remarks on, 183 Acid anhydrides, 157, 159 compounds, 169 Amyl acetate, 162 , cyanide, 176 derivatives. 174 Acid haloids, 157 Acids, 39 n-Amyl alcohol, 101 Amyl , commercial, 101 oxide. 175 sulphide, 176 , acetic series, 136 alcohols, 100 Cacodylic acid, 176 , acrylic series, 211 nitrite, no Cane sugar, 268 AcroleTn, 210 valerate, 162 Caproic acids, 136 Acrylic acid, 211 Amylenes, 58 Caramel, 269 aldehyde, 210 Active amyl alcohol, 102 Analysis, qualitative organic, 12 Carbamic acid, 201 Carbamide, 201 Adipic acid, 240 , quantitative, 12 Carbamines, 194 Air-bath for heating tubes, 22 , ultimate, 12 Carbinol, 80 Alanine, 185 Arabinose, 259 Carbohydrates, 263 Alcarsin, 175 Arabite, 259 Carbon, detection cf, 12 Alcoholic beverages, 91 Arabitol, 259 dioxide, 200 radicles defined, 47 Arabonic acid, 259 disulphide, 204 Alcoholometry, 93 Alcohols, 39, 78 Arsenic, alkyl compounds of, , estimation of, 13 , , in presence of nitro- , diagnosis of, 96 Arsines, 173 gen, halogens, etc., 16, 17 288 Index CAR ETH FOR Carbon monoxide, 200 Di-ethyl carbinol, 101 Ethine, 59 mono-sulphide, 203 ether, 104 Ethinene, 59 oxy-sulphide,' 203 phosphine, 172 Ethyl acetate, 160 tetra-bromide, 77 sulphonic acid, 117 aceto-acetate, 281 ^ -chloride, 76 iodide, 77 Carbonic acid, 224 , derivatives of, 200 Carbonyl chloride, 200 Di-ethylamine, 167 Di-glycollic acid, 226 Di-haloid olefines, 207 Di-hydroxy dicarboxylic acids, 251 alcohol, 83 , identification of, 86 , manufacture of, 88 bromide, 68 butyrate, 162 Carboxyl acids, 39 Di-iodo-ethanes, 70 chloride, 67 Cellulose, 277 Di-lactic acid, 228 cyanate, 197 nitrates, 278 Di-methyl ether, 103 formate, 162 Chloral, 129 hydrate, 131 ketone, 133 malonic acid, 230 hydrogen sulphate, 118 sulphite, 116 Chlor-acetic acid, 147 Di-methylatnine, 166 iodide, 69 -carbonic acid, 201 Di-methylarsine, derivatives, isocyanate, 197 -ethylene, 206 T 74 malonate, 2^3 formic acid, 201 Di-saccharides, 263, 268 malouic acid, 230 hydrins, 245 mercuric ethyl, 181 Distillation, 5 in a current of steam, 8 mercaptan, 113 nitrate, 112 Chloroform, 73 Dulcite, 260 nitrite, 108 Chloropicrin, in Dulcitol, 260 nitrolic acid, in Citric acid, 257 Dynamite, 247 ortho-acetate, 243 Collodion, 278, 279 ortho-formate, 242 Combustion furnace, 14 oxalate, 234 Combustions, closed-tube me- ELA'foic acid, 213 phosphine, 171 thod, 17 Elementary analysis, 12 phosphinic acid, 172 , open-tube method, 14 Empirical formulae, 24 silicic acid, 178 Compound ethers, 107 radicles, defined, 2 Enzymes, 87 Epichlorhydrin, 246 silicon tri-chloride, 178 tri-ethylate, 178 Constitution of organic sub- Erythric acid, 251 sulphate, 1 18 stances, 34 Constitutional formula, 34 Erythrite, 251 Erythritol, 251 sulphide, 114 sulphite, 116 Contractions, 40 Esters, 39, 103, 1O7 sulphonic acid, 116 Cordite, 247 , defined, 107. thiocyanate, 199 Grotonic acid, 212 of carbonic acid, 201 Ethylal, 218 aldehyde, 128, 210 of cyanic acid, 197 Ethylamine, 165 Crotonylene, 64 of fatty acids, 160 Ethylene, 53 Cuprous chloride, preparation of, 60 Cyamelide, 195 , general remarks on, 161 of hydrocyanic acid, 193 of hydrogen sulphide, bromide, 71 chloride, 70 chlorhydrin, 219 Cyanamide, 196 Cyanates, 196. Cyanetholine, 197 Cyanic acid, 195 112, 113, 114 of isocyanic acid, 197 of isothiocyanic acid, 199 , mineral acids, 107 , constitution of, 55 , halogen derivatives, con- stitution of, 73 iodide, 72 Cyanides, 190 of mineral acids, general lactic acid, 229 , compound, 191 remarks on, 119 oxide, 219 Cyanogen, 187 chloride, 196 of nitric acid, in of nitrous acid, 108 Ethylidene bromide, 72 chloride. 71 derivatives, 186 of ortho acids, 242 glycol, 221 Cyanuric acid, 197 of sulphuric acid, 117 iodide, 72 of sulphurous acid, 115 lactic acid, 227 of thiocyanic acids, 199 DEPHLEGMATING apparatus, Ethane, 43 7.8 . phosphonic acid, 172 FARINOSE, 274 Detection of hydroxyl, 159 Dextrin, 276 sulphonic acid, 116 Ethene, 53 Fats, 153 Fatty acids, 136 Dextrosan, 265 bromide, 71 , general remarks on, Dextrose, 263 chloride, 70 148 Dextro-tartaric acid, 252 iodide, 72 Fehling's solution, 266 Diamidogen, 170 Diamines, defined, 163 Ether, 104 , compound, defined, 103 Fermentation, 87 , amyl alcohol, 101 Di-brom-succinic acid, 237 peroxide, 106 Flashing point, 46 ethanes, 70 Ethereal salts, 39, 1O7 Formaldehyde, 121 Dicarboxylic acids, remarks Ethers, 102 Formamide, 182 on, 240 Di-chlor-ethanes, 70 , defined, 39, 1O2 , general remarks on, 106 Formic acid, 137 , constitution of, 145, hydrin, 245 , mixed, 102 147 Di-cyanogen, 186 , simple, 102 aldehyde, 121 Index 289 FRA MAL NIT Fractional distillation, 5 Hydrocarbons, 40 Malt sugar, 270 precipitation, 9 , nomenclature of, 52 Mannite, 259 Fructose, 266 Hydrocyanic acid, 188 Mannitol, 259 Fumaric acid, 241 Hydrogen, detection of, 12 Marsh gas, 41 , estimation, 13 Melting point, determination Hydrolysis defined, 57, 109 of, TI GLUCONIC acid, 262 Hydroxy-dicarboxylic acids, Mercaptan, 113 Glucose, 263 249 Mercaptans, 113 Glucoses, 263 Hydroxy-mercuric ethyl, 181 , general remarks on, 114. Glucosides, defined, 264 Glutaric acid, 230 Hydroxy-propionic acid, 227 Hydroxy-tricarboxylic acids, Mercury ethyl, 180 Meso-paraffins, 51 Glyceric acid, 248 257 Mesoxalic acid, 252 Glycerin, 243 Hydroxyl, detection of, 159 Metachloral, 131 Glycerol, 243 Metaldehyde, 127, 128 , oxidation products of, IMIDO-BASE, defined, 163 Metallo-organic compounds, 248 Glycerose, 244 Glyceryl tri-nitrate, 247 Inactive amyl alcohol, 101 tartaric acid, 237 178 Metamerism, 107 Metamers, 107 Glycide chloride, 246 compounds, 246 Glycine, 183 Inulin, 270 Invert sugar, 264 Invertase, 87, 270 Methane, 41 series, 41 Methyl acetate, 160 Glycocoll, 183 Glycogen, 276 Iso-amylene, 58 alcohol, 80 , constitution of, 82 Glycol, 216, 218 Glycolide, 226 Glycollates, 220 Glycollic acid, 217, 224 aldehyde, 217, 222 anhydride, 226 dt-acetin, 220 mono-acetin, 219, 22O Glycols, 216, 217 -, general remarks, 221 , oxidation products of, 222 butyl alcohol, 99 butyric acid, 151 cyanates, 196 cyanides, 194 nitriles, 194 , constitution of, 195 paraffins, 51 pentane, 50 pentoic acids, 151 pentylenes, 58 propyl alcohol, 98 bromide, 68 chloride, 66 cyanide, 193 ethyl acetic acid, 152 hydrogen oxalate, 233 sulphate, 117 iodide, 69 isocyanide, 194 isopropyl carbinol, 102 mercaptan, 113 nitrate, m nitrite, 108 Glyoxal, 217, 222 iodide, 70 oxalate, 233 Glyoxylic acid, 217, 223 Granulose, 274 Graphic formulae, 34 Guncotton, 278, 279 HALOGEN hydrins, 219, 245 succinic acid, 240 valeric acid, 152 Isologous series, 52 Isomerism, definition of, 49 -of acids, 150 of alcohols, 79 Isomers defined, 49 propyl carbinol, 101 sulphate, 118 Methylal, 218 Methylamine, 165 Methylarsine dichloride, 176 Methylated spirit, 90 Methylene acetate, 218 , substitution compounds, chloride, 70 38 KETONES, 133 Methylene glycol, 217 Halogens, detection of, 21 , general remarks on, 135 Milk sugar, 271 ~, estimation of, 21 Ketoses, 263 Molecular formula, determi- Haloid esters, 38 Ketoximes, 134 nation of, 25 paraffins, 64 Molecular weights of acids, ^ , general remarks on, 77 LACTIC acid, 227 * of bases, 33 Monamine, defined, 163 Heptane, 45 Heptylene, 52 Hexa-hydric alcohols, 259 and derivatives, 259 , oxidation products, 261 Hexahydric alcohols, 261 Hexamethyleneamine, 123 Hexanes, 50 acids, 227 , constitution of, 229 anhydride, 228 Lactide, 228 Lactonic acid, 262 Lactose, 271 Laevotartaric acid, 256 Leucine, 185 Levulosan, 267 Monohydric alcohols, 80 , general remarks on, 94 Mucic acid, 262 Murexide, 205 Mustard oils, 199 Mycoderma aceti, 140 Myrosin, 209 Hexyl alcohols, 80 Hexylene, 52 Levulose, 266 Linoleic acid, 215 NEO-PARAFFINS, 51 Higher paraffins, 45 Nitrile base, defined, 161 Homologous series, 45 MALEIC acid, 241 Nitriles, 138, 193 Homologues, 45 Malic acid, 249 , constitution of, 195 Hydracrylic acid, 229 Malonic acid, 234 Nitro-chloroform, in Hydrazines, 169 ester, 283 compounds, 108 Hydrazones, 126, 129 ether, 235 ethane, no Hydrocarbides, 40 Maltose, 270 form, in U 290 Index NIT Nitro-glycerin, 246 methane, no Nitrogen, alkyl compounds with, 162 , detection of, 18 , estimation of, 19 Nitrolic acids, 97 Normal paraffins, 50 OCTANE, 45 Octylene, 52 Oils, 153 Olefines, 52 , derivatives of, 206 , general remarks on, 56 Oleic acid, 212 Olein, 154 Oleine, 155, 156 Oleomargarine, 154 Organic chemistry denned, 3 Organogens, 12 Ortho-formic acid, 242 Oxalates, 233 Oxalic acid, 230 , esters of, 233 ether, 234 Oxamide, 234 Oxidising agents, 284 Oxygen, estimation of, 23 PALMITIC acid, 152 Palmitin, 154 Para-aldehyde, 127 Para-cyanogen, 187 Paraffin series, 41 Paraffins, 41 , general remarks on, 47 , nomenclature of, 50 Paraformaldehyde, 123 Paralactic acid, 228 Penta-hydric alcohols, 259 n-Pentane, 50 Pentanes, 49 Pentoic acids, 151 Pentyl alcohols, 100 Pentylenes, 58 Percentage composition, 24 Petroleum, 45 , purification of, 45 Phosphines, 170 general remarks on, 173 Phosphonium compounds, 173 iodide, 170 Phosphorus, alkyl compounds with, 170 , detection of, 23 , estimation of, 23 Pinacones, 221 Polysaccharides, 263, 273 Potassium ethyl, 180 ' carbonate, 201 '- ferricyanide, 192 ferrocyanide, 191 myronate, 209 Primary amines, defined, 163 monamines, 165 paraffins, 50 STE Proof spirit, qo Propaldehyde, 120 Propane, 48 Propargyl alcohol, 214 Propiolic acid, 215 Propionic acid, 150 n- Propyl alcohol, 97 Propyl alcohols, constitution of, 98 halogen compounds, 70 Propylene, 57 Prussian blue, 192 Pseudo-nitrols, 97 Purification of compound, 4 Purity of compound, determi- nation of, 9 Pyrotartaric acid, 230 QUAKTERNARY baSCS, 163 RACF.MIC acid, 256 Raoult's method for mol. wt., 25,30 Rational formula;, 34 Recrystallisation, 4 Rectified spirit, 90 Reducing agents, 284 Ricinelaidic acid, 213 Ricinoleic acid, 213 SACCHARIC acid, 262 Saccharides, 263 Saccharomyces cerevisiae, 87 Saccharon, 268 Saccharoses, 263, 268 Saponification defined, 109 Sarcolactic acid, 229 Saturated compounds defined, hydrocarbons, 40 Schweitzer's reagent, 277 Secondary amines, defined, 163 butyl alcohol, 99 monamines, 166 paraffins, 51 propyl alcohol, 98 Silico-monyl alcohol, 178 Silicon, compounds of, 177 ethyl, 177 methyl, 177 Soap, manufacture of, 154 Soaps. 153 Soda lime, 18 Sodium ethyl, 180 Solvents, separation by, 5 Sorbitol, 260 Sources of organic com- pounds, 3 Specific rotatory power, 265 Spirits, 92 of wine, 83 Spiritus aitheris nitrosi, 109 Starch, 273 Stearic acid, 153 Stearin, 156 TRI Study, method of, 40 Substitution derivatives, de- fined, 64 Succinamide, 238 Succinates, 237 Succtntc acid, 235 , haloid substitution products, 237 acids, 235 anhydride, 238 esters, 238 Succinimide, 239 Succinyl chloride, 238 Sucrose, 268 Sulphur, detection of, 23 , estimation of, 23 Sweet spirit of nitre, 109 TARTARIC acids, 252 Tartrates, 255 Tartronic acid, 249 Tertiary amine defined, 163 amyl alcohol, 102 arsines, 174 butyl alcohol, 100 paraffins, 51 Tetra-ethyl-ammonium hy- droxide, 169 Tetra-ethyl-ammonium io- dide, 169 Tetra-ethyl-phosphonium hy- droxide, 173 Tetra-ethyl-phosphonium io- dide, 173 Tetra-hydric alcohols and their derivatives, 251 Tetra-methyl ammonium hy- droxide, 169 Tetra-methyl ammonium io- dide, 169 Tetra-methyl arsonium hy- droxide, 177 Tetra-methyl arsonium io- dide, 177 Tetra-methyl di-arsine, 175, 176 Tetra-methyl methane, 50 Thio-alcohol, 113 carbonyl chloride, 204 -cyanates, 1 98 cyanic acid, 198 -cyanic acids, 198 ethers, 114 urea, 204 Triamines, defi ed, 163 Tri-chlor-acetic acid, 148 aldehyde, 129 -hydrin, 246 Tri-ethyl phosphine, 172 sulphine iodide, 115 sulphonium hy- droxide, 115 ethylamine, 168 Tri-hydric alcohols and their derivatives, 242 Tri-methyl acetic acid, 152 methane, 167 methylamine, 167 Index 291 TRI Tri-tnethylarsine, 174 -oxymethylene, 124 thio-carbonic acid, 204 -thio-methylene, 123 Turnbull's blue, 193 UNSATURATED compounds defined, 35 hydrocarbons, 51 Urea, 201 VAP Urethanes, 201 Uric acid, 204 N-VALERIC acid, 152 Valeric acids, 151 Valerylene, 59 Vapour density determina- tions, 26 (Dumas), 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