182 METHYLIC ALCOHOL, OR WOOD SPIRIT. used for stiffening the basis of silk hats. The hydrates of the alkalies are soluble in wood spirit, but they immediately colour it brown. Ure used this reaction as a means of discovering small quantities of pyroxylic spirit when mixed with alcohol, since alcohol is not thus altered in colour until after a considerable lapse of time. Caustic baryta is soluble in wood spirit, forming with it a crystallizable compound, Ba✪,2 ¤H ̧Ð; and many salts form definite compounds with it; that with chloride of calcium (EaCl2,4ЄH ̧Ð) crystallizing in six-sided tables. It has already been mentioned that when alcohol is submitted to a gradual and incomplete oxidation, one of the products of the operation is aldehyd (1249), which passes, by further oxidation, into acetic acid. Now, wood spirit may in like manner be subjected to partial oxidation, under the influence of finely divided platinum; and though the different stages of the process have been less satisfactorily investigated than those which occur with ordinary alcohol, it appears that an intermediate substance is formed, which, like aldehyd, has the power of reducing the salts of silver; and finally, a strong solution of formic acid is produced. This acid stands in the same relation to the methylic series that the acetic does to the ethylic series: This method, however, is not an advantageous one for the preparation of formic acid, since it is difficult to prevent the oxidation from going a stage further, and converting the formic acid into carbonic anhydride and water :-— When wood spirit is heated moderately with soda-lime, formiate of the basyl is produced, and hydrogen is liberated : Wood spirit. ЄH2O + NaHO If caustic potash be employed oxalate is formed, whilst a large Wood spirit. = Sodic formiate. : Na¤HO2+ 2 H2. instead of soda-lime, potassic evolution of hydrogen occurs :-- 2 €Ꮋ Ꮎ + 2 ᏦᎻᎾ = ETHYLIC, OR ORDINARY ALCOHOL. 183 6 (1126) 2. ALCOHOL; Ethylic or Vinic Alcohol; Spirit of Wine (¤ ̧Н ̧→ or СH ̧O2=46). Sp. gr. of liquid at 32°, 0·815; of vapour 1·6133; Rel. wt. 23; Boiling pt. 173° (78.3° C.)—Alcohol is a colourless volatile inflammable liquid, of an agreeable wellknown spirituous odour, and an acrid burning taste. When pure it has a specific gravity of 0.7938 at 60°. It has never been frozen, though at a temperature of -165° (-110° C.) it becomes viscid. When taken in small quantities in a diluted form it furnishes a useful and well-known stimulant, forming the basis of all fermented liquors. In large quantities it produces intoxication, and acts as a powerful narcotic poison, frequently occasioning fatal results when taken in a concentrated state and in excess. Alcohol furnishes a cleanly and valuable fuel to the chemist: it emits a high temperature during its combustion, and deposits no soot upon cold bodies which are introduced into its flame. When burned in air it emits but little light, and is wholly converted into carbonic anhydride and water: two volumes, or one molecule, of alcohol vapour, for complete combustion requires three times its bulk, or six volumes, of oxygen; ¤‚H ̧¤+30,= 2 ЄO2+3 H2O. When the vapour of alcohol is transmitted through red-hot tubes it is decomposed. The products vary according to the temperature employed; at low temperatures, olefiant gas, marsh gas, water, carbonic oxide, and acetylene are formed; and at higher temperatures naphthalin; whilst at a bright red heat carbon is deposited, and free hydrogen produced. By gradual oxidation alcohol yields amongst other bodies, aldehyd and acetic acid (1250). With nitric acid it furnishes nitrous ether, glyoxal, glyoxalic acid (1299 note), with glycolic (1308) and oxalic acids. When alcohol is exposed in its concentrated form to the atmosphere it attracts moisture like sulphuric acid; and like this compound, when mixed with water, it emits heat and contracts in bulk, though to a considerably less extent; the observed density of the mixture of alcohol and water is therefore greater than its calculated mean density. According to Rudberg, the condensation is greatest when 53'739 measures of alcohol and 49.836 of water are mixed at 59° (15° C.): these proportions correspond to Є2H2+3 HO; when cooled again to 59°, this mixture occupies -3 6 only 100 measures instead of 103.575, and has a sp. gr. of o'927. From the importance of alcohol as an exciscable article, great labour has been bestowed upon the means for readily determining its percentage in spirituous liquors. The method in common use 2 184 ETHYLIC, OR ORDINARY ALCOHOL. for distilled spirits consists in determining the specific gravity by means of a sensitive hydrometer, and tables have been constructed for showing the percentage of alcohol in mixtures of various densities. In these cases great attention must be paid to the temperature, since slight differences in this particular make a material variation in the density. The term proof spirit, in constant use among the excise, is defined by an Act of Parliament (58 George III.), to be "such as shall at the temperature of 51° F. (10°5 C.) weigh exactly twelve thirteenth parts of an equal measure of distilled water." It consists of water 50'76, alcohol 49'24 by weight, and indicates alcohol of sp. gr. c'920 at 60° (Drinkwater, o'91984). The term derives its origin from the rude method of proof formerly in use, in which gunpowder was moistened with the spirit of wine to be tried, and the alcohol ignited; if it fired the powder it was said to be over proof, but if the spirit burned off and left the powder damp, it was considered to be under proof; the weakest spirit capable of thus firing powder had a sp. gr. of about o'920.* Every additional o'5 per cent. of absolute alcohol above o‘920 is said to be one degree over proof. Alcohol is a solvent of great value to the chemist. It usually exerts but little chemical action upon the bodies which it dissolves, and owing to its volatility it is easily expelled by a gentle heat, leaving the substances which it previously held in solution, in a pure state. Alcohol dissolves many of the gases freely; some of them, as for instance, nitrous oxide, carbonic anhydride, phosphuretted hydrogen and cyanogen, and the hydrocarbons, are dissolved by it more readily than by water. Iodine and bromine are also readily soluble in it, but their solutions gradually undergo decomposition, in consequence of the reaction of iodine and bromine upon the alcohol. Absolute alcohol dissolves small quantities of phosphorus and of sulphur. The alkaline sulphides, as well as caustic potash and soda, are soluble in it to a very large extent; and ammoniacal gas is absorbed by it nearly as readily as by water; but it does not dissolve the carbonates of these alkalies. Alcoholic solutions of caustic potash and soda act powerfully as reducing agents upon many metallic solutions, such as those of platinum; they gradually absorb oxygen from the air, and become brown, owing to the formation of a resinoid substance, the resin of aldehyd. When dropped upon fused In the Appendix two tables of the strength of alcohol at different specific gravities will be found. PREPARATION OF ALCOHOL. 6 3 185 caustic potash, alcohol is decomposed, hydrogen is evolved, and potassic acetate is produced, H2O+KHO=2H2+K¤¿H ̧Ð1⁄2 Sodium or potassium dissolves readily in alcohol with evolution of hydrogen, and considerable rise of temperature, forming a powerfully alkaline substance, sodic, or potassic ethylate, 2 €,H+ Na2= =2 ¤‚H ̧NaO+H,. When heated with sulphuric acid, alcohol yields sulphovinic acid, ether, or olefiant gas, according to the temperature employed and the proportions used. 2 6 The results of the action of chlorine (1174) and of sulphuric and other acids (1133), as well as of sodium and other metals (1181 et seq.) upon alcohol, will be further alluded to hereafter. Most of the deliquescent salts are soluble in alcohol, but the efflorescent salts, and those which are sparingly soluble in water, are not dissolved by it. Anhydrous alcohol combines with many anhydrous saline bodies in definite proportions, and forms with them crystallizable compounds, in which the alcohol, according to Graham, occupies the place of water of crystallization. The chlorides and the nitrates offer the best examples of the formation of these alcoates. The compound with chloride of calcium (EaCl, 4€2H), crystallizes readily; and analogous compounds may be obtained with the chlorides of zinc and manganese, and with the calcic and magnesic nitrates. Alcohol likewise dissolves freely many organic bodies, such as the resins, the essential oils, the vegetable alkaloids, and many of the vegetable acids. It also dissolves, more sparingly, sugar, and the soaps of potash, soda, and ammonia; but the fats and fixed oils, with the exception of castor oil, are dissolved by it in but small quantities. A characteristic reaction of alcohol is its power of forming fulminate of silver; when c'1 grm. of silver is dissolved in 2 grms. of nitric acid, and about 5 of alcohol are added, crystals of fulminate of silver are gradually deposited. Preparation.-Alcohol may be obtained in a state of purity by subjecting to distillation any saccharine solution that has undergone fermentation; for being more volatile than water it passes over in the first part of the distillation, accompanied with more or less water. By repeated rectifications, or by a single operation in Coffey's still (188), it may be concentrated till it contains about 10 per cent. of water. Beyond this point the water adheres to it so strongly that it requires a different process for the complete separation of the last portions :-it is first rectified from charcoal, with a view of retaining all essential oils to which the peculiar odour and flavour of different spirits 186 WINES, FERMENTED LIQUORS, AND SPIRITS. are mainly owing, and is then mixed with about half its weight of quicklime, and allowed to stand for three or four days: the lime gradually slakes and falls to powder in consequence of its conversion into a hydrate, at the expense of the water in the alcohol; then, on applying heat by means of a bath of chloride of calcium, the pure spirit may be distilled off, the hydrate of lime retaining the water at temperatures far above 300° F. (149° C.) Any traces of water which it may still retain are removed by a second distillation from quicklime, or from caustic baryta. The alcohol thus obtained is anhydrous, or as it is often termed, absolute alcohol.* Berthelot (Ann. de Chimie, III. xliii. 385) has pointed out a means of obtaining alcohol synthetically, by forming a solution of olefiant gas in oil of vitriol, which dissolves about 120 times its bulk of the gas, then diluting the mixture with water, and submitting it to distillation. Small quantities of dilute alcohol are thus obtained with facility. Tritylic alcohol has been obtained by acting on tritylene in a similar manner, but the denser hydrocarbons of this series, such as octylene, become charred when thus treated. (1127) Wines, Fermented Liquors, and Spirits.-The various kinds of spirits in use derive their names from accidental circumstances, often from the flavour which they possess. For instance, gin is spirit flavoured by distilling it with juniper berries; peppermint owes its aroma to the essential oil of the plant after which it is named; whisky is spirit distilled from wort prepared from malt which has been dried over a peat fire, to which its peculiar flavour is due; arrack is a spirit distilled from fermented rice; and rum, a West Indian product from molasses; brandy is really the 'spirit of wine,' being obtained from wines by distillation, and coloured more or less deeply with burnt sugar. In all these cases the characteristic flavour depends upon a small quantity of some volatile oil or compound ether, which passes over with the spirit during the process of distillation. The varieties of spirits are very numerous, and those of fermented liquors which are used without subjecting them to distil The methylated spirit of commerce consists of a mixture of alcohol of sp. gr. 0830 with 10 per cent. of wood spirit. This addition of wood spirit scarcely interferes with the employment of the spirit as a solvent, though it renders it unfit for use afterwards as a stimulant drink; it was added to facilitate the use of spirit in the arts without inflicting injury on the revenue. The offensive odour may, however, be removed by prolonged contact with charcoal, as has been shown by Mr. Eschwege. |