TABLE XXXIV., SHOWING THE ALCOHOLIC CONTENT BY VOLUME OF BOILING SPIRITS AND OF THEIR VAPOUR, FROM THE TEMPERATURE OF THE LATTER, AS OBSERVED BY A THERMOMETER. BY GRÖNING.

TABLE XXXV., EXHIBITING THE BOILING POINTS OF ALCOHOL AND WATER OF THE GIVEN STRENGTHS. BY GRÖNING.

§ 231. Tests for Alcohol. The principal tests for alcohol are the following:-

(1.) Production of Acetic Ether.-To a distillate or aqueous solution supposed to contain alcohol, some acetate of soda is

added and sulphuric acid in amount more than sufficient to decompose the acetate. The flask containing the mixture is connected with a Liebig's condenser, placed vertically, and boiled for a few minutes; any volatile vapour is condensed, and falls back again into the flask. On removing the cork, if acetic ether has been produced, it can readily be detected by its odour.

(2.) Reduction of Chromic Acid or Bichromate of Potash to Oxide of Chromium.-A crystal of chromic acid, placed in a test-tube, with a fluid containing alcohol warmed to a boiling temperature, is decomposed into the green oxide of chromium. Instead of chromic acid, a test-solution of one part of dichromate of potash dissolved in 300 parts of sulphuric acid may be used. A portion of the liquid to be tried is mixed with twice its volume of concentrated sulphuric acid. On pouring a small quantity of this mixture into a quantity of the test-solution, a deep green is produced where one fluid touches the other. This is a very good test in the absence of other reducing agents, such as formic acid, ether, &c.

(3.) Dr. Edmund Davy's Test.-Dr. Davy has proposed a test for alcohol founded on a colour reaction, and produced also by methyl, propyl, butyl, and amyl alcohols, ether and aldehyde. A solution of one part of molybdic acid in ten of strong sulphuric acid, is warmed in a porcelain capsule, and the liquid to be tested allowed to fall gently on it. If alcohol is present, a blue coloration appears either immediately, or in a few moments; the liquid gradually absorbs moisture from the air, and the colour disappears, but it may be reproduced by evaporation.*

(4.) The production of Iodoform.-According to Lieben, one part of alcohol in 2000 of water can be detected by adding to some of the warmed liquid a few drops of a 10 per cent. solution of soda, and dropping in a solution of potassium iodide, fully saturated with free iodine, until the liquid is yellowishbrown; then the alkali solution must be added until the whole is colourless, and the mixture allowed to stand for many hours, when a yellowish crystalline deposit of iodoform is obtained. Under the microscope the latter presents the appearance of hexagonal plates, six-rayed, or other varieties of, stellar crystals: C2H2O+412 + 6NaHO = CHI, + NaCHO2+5NaI + 5H20. objection to this test is, however, that other alcohols, aldehyde, gum, turpentine, sugar, &c., give a similar reaction.+

The

* Proceedings of the Royal Irish Academy [2] ii. 579–582; Journ. Chem. Soc., 7, 1877, p. 108.

+Rajewsky has found that the brain of a rabbit, which had been starved for two days before death, gave a marked reaction for alcohol with the iodoform test, and the same result was obtained from the muscles and

(5.) The production first of Acetic Acid, then of Kakodyl.-A very delicate test for alcohol, and one specially suited for its detection in the blood, &c., is recommended by Bucheim.

The finely-divided substances are put in a tubulated retort, and, if acid, carefully neutralised. In the neck of the retort is placed a little porcelain or platinum boat, containing platinum black, and at each end there is a moistened piece of stronglyblued litmus-paper. On warming the retort, if alcohol be present, it is oxidised by the platinum black to aldehyde and acetic acid; hence, the hinder piece of litmus-paper will be reddened, the front one unchanged. If only a drop of acetic acid be present, it is possible to detect it in the following way:The platinum black is washed, the washing water neutralised with potash, and dried after the addition of a few grains ef arsenious acid. On warming the dry residue in a small glass tube, if even a very small admixture of acetic acid be present, the smell of kakodyl will be perceptible.

The Action of Alcohol on Benzoyl Chloride.—This test, proposed by Berthelot, is based on the fact that very small quantities of alcohol decompose benzoyl chloride with the formation of ethyl benzoate. The sample is shaken up in the cold with a few drops of benzoyl chloride; any ethyl benzoate formed sinks to the bottom with the excess of benzoyl chloride. This heavy layer is removed by a pipette, and heated with a little caustic soda or potash, which dissolves at once the benzoyl chloride, but not the ethyl benzoate, and the latter may be recognised by this insolubility, by its general properties, and by its boiling point. It is nearly insoluble in water, burns with a smoky flame, has a characteristic pleasant odour, and boils at 213°.

Mr. J. Hardy has proposed a very simple test for the detec tion of alcohol, which may be performed as follows:-Two common "Nesslerising" glass cylinders are taken, and a little guaiacum resin, which has been removed from the interior of a freshly broken lump, is shaken up with the sample to be tested. The liquid is filtered, and a few drops of hydrocyanic acid and a drop of very weak solution of sulphate of copper added. Exactly the same process is adopted with an equal bulk of distilled water. On now placing the two liquids in the glass cylinders side by side, over a porcelain plate, the liquid to be tested, if it contains alcohol, will be found of a blue colour decidedly darker than that of the distilled water.

§ 232. Separation of Alcohol from Animal Matters. In order to tissues of rabbits. He therefore considers that alcohol always exists in the animal organism, or that it is produced during distillation.-Pflüger's Archiv. für Physiologie, xi. 122, 127.

obtain alcohol from organic matters (e.g., the contents of the stomach, or the tissues), the following process will be found convenient :-Solid matters, such as the tissues, are cut up as finely as possible, and placed with water in a retort attached to a suitable condenser. Most liquids require no previous preparation, and are merely poured into the retort or flask, as before de scribed; but it is desirable in the treatment of urine to add a little tannic acid. About one-third to one-half of the liquid is distilled over into a flask closed by a mercury valve. The product is now made alkaline with caustic potash (which will fix any volatile acid, and expel any volatile alkali), and again distilled, about one-third being drawn over. The liquid is next neutralised with sulphuric acid, to fix volatile alkalies, and redistilled. This final distillate contains all the alcohol, but neither volatile acids nor alkalies. The liquid thus obtained may even now be too dilute to respond conveniently to tests, and it may therefore be digested for some hours with a little caustic lime, and then very slowly distilled. The distillate should finally be carefully measured or weighed, and divided into two parts, one of which serves for the application of the usual tests, the other (if alcohol be found) can be oxidised in the manner described at p. 380, and estimated as acetic acid volumetrically.

J. Bechamp (Compt. Rend., 89, 573, 574) has recently succeeded in obtaining a sufficient quantity of alcohol from the fresh brain of an ox to estimate by specific gravity, and has also separated it from putrefying animal matter. In fact, it is capable of proof, that all putrefaction is accompanied by the production of minute quantities of alcohol, and that the living cells of the body also produce it. Hence, in questions of poisoning, it is not enough to obtain qualitative reactions for alcohol, but the quantity also must be accurately estimated.

ESTIMATION OF ALCOHOL IN SPIRITS AND ALCOHOLIC

LIQUIDS.

§ 233. In the examination of alcoholic liquors, one of the analyst's first steps is to determine the percentage of alcohol, and the methods by which this is done are equally applicable (with slight modifications) to all liquids containing alcohol. The percentage is ascertained

(1.) By distillation, and taking the specific gravity of the distillate.

(2.) By Tabarie's method, applied especially to wines and beers.

(3.) By Geissler's vaporimeter.

(4.) By oxidation into acetic acid, and by several other methods, which are, however, not much in use by the analyst. (1.) Distillation.-A convenient quantity (e.g., 100 cc. of beer or wine, 50 cc. of spirits, measured at 15°5) is placed in a flask (a, fig. 41), having a side tube connected by means of a cork to a

Liebig's condenser. The distillate is received in a flask (b) provided with a doubly perforated cork, into which the bent tube of the condenser, as well as a tube provided with a mercury valve, to prevent loss, is adjusted; the latter may be readily made by putting a very small quantity of mercury into the bend of an ordinary thistle-head funnel (c). This precaution is only necessary when very small quantities are operated upon. Experiments with 50 cc. of spirit distilled into a flask unprovided with a valve, have shown that there is no appreciable loss; but distillation