Page:Encyclopædia Britannica, Ninth Edition, v. 1.djvu/508

Rh 470- ALCOHOL Alcohol has the f ollowing chemical composition : Carbon 52 67 per cent. Hydrogen 12-90 Oxygen 34 43 ,, 100-00 ,, Its formula in chemical symbols is C,H 6 0. During the fermentation of sugar the change that takes place is repre sented as follows : C f ,H 12 6 = Grape sugar. 2 CJI 6 Alcohol. + 2 CO, Carbonic acid. The complex body, grape-sugar, breaks up by the action of the ferment or yeast into alcohol or carbonic acid, without anything being added. This kind of chemical change is sometimes called an action of presence, or catalytic action, because the substance inducing it does not enter into the composition of the products of the reaction. The alcohol ferment or yeast is a minute cellular plant that grows rapidly in sugar solution, especially if albumenoid matter is also present, and during the continuance of its vital functions causes a rearrangement of the atoms of the sugar. In order that fermentation may proceed regularly, a tempera ture of about 60 Fahr. is required, and an amount of sugar in solution not exceeding 10 per cent. The sugar is principally obtained from malt, which is barley that has been allowed to germinate for a certain time, and is then arrested in its growth by heating to a high temperature. During this process of germination there is a peculiar ferment produced called diastase ; this has the remarkable property of changing starch into grape-sugar. When the malt is treated with water, the ferment causes all the starch originally present in the grain to appear in solution as grape-sugar. All kinds of starch may be changed into grape-sugar by boiling with dilute sulphuric acid, which in this case acts somewhat like a ferment, because it is not decomposed during the action. The sulphuric acid is afterwards separated by treating with lime, which produces insoluble sulphate of lime (gypsum), and leaves the sugar in solution. In this way sugar for the alcohol manufacture is now largely made from the potato and other starch- yielding plants. Cane-sugar is too expensive to be employed in the distillery. Molasses, or the uncrystallis- able portion of the cane-sugar, is, however, largely used. Alcohol, when acted on by other chemical substances, produces a great variety of new compounds. With acids a remarkable class of bodies are produced called ethers, of which ordinary ether is the type. The majority of them are very volatile fluids, that in many cases have a very agree able odour, and are not readily soluble in water. Many ethers are obtained by simply heating a mixture of the acid and alcohol in a closed vessel to a temperature of 21 2 Fahr., and subsequently treating with water. The water dissolves the alcohol not acted upon, and leaves the ether floating on the surface. When alcohol is treated with chlorine, absorption occurs, and hydrochloric acid is continuously evolved for many hours, the temperature rising considerably during the action. Many substances are formed in succession, but the principal product, after long-continued action, is the substance chloral, now largely used as an anaesthetic. Bromine produces a similar body called bromal. Iodine does not act on alcohol at ordinary temperatures, further than to pass into solution. When treated with a solution of chloride of lime, alcohol is violently attacked, and the result of the action is the well-known substance chloroform. Acted on by oxidising agents, alcohol gives two new sub stances aldehyde and acetic acid. The ease with which acetic acid is produced by heating with a mixture of bichromate of potash and sulphuric acid gives a delicate method of detecting and estimating very small quantities of alcohol. When the vapour of alcohol is passed through a red-hot tube filled with fragments of pumice-stone, com plete decomposition takes place. Among the products are found naphthalin, benzol, hydrogen, marsh gas, ethylene, and other bodies. The synthesis of alcohol has been effected by means of the hydro-carbon called olefiant gas, which may be made directly from carbon and hydrogen. When this gas is shaken with strong sulphuric acid it gradually combines with it ; and if it is afterwards diluted with water and distilled, alcohol passes over. As olefiant gas is one of the constituents of common coal-gas, this substance may be used to make alcohol by the above method. The action that takes place is represented thus : C 2 H 4 + H,0 - C.H.O Olefiant Gas. Water. Alcohol. As the value of spirituous liquors depends mainly on the quantity of alcohol they contain, it is essential to find some simple and rapid means of ascertaining the percentage amount of the substance present. For this purpose three methods may be employed, viz., specific gravity determina tion, temperature of ebullition, or rate of expansion. The easiest plan, and the most generally used, is the density method. Very accurate tables are published of the specific gravity of mixtures of alcohol and water in all proportions, so that it is only necessary to refer to these tables to get the percentage composition. In the case of liquors, like wines or beers, that contain many other substances in solu tion in addition to alcohol, it is necessary to separate the alcohol from the extractive matters sugar, salts, &c. by distillation, and to take the density of the volatile portion. As wines contain many volatile ethers that would pass over with the alcohol in the above process, and interfere with accurate results being obtained, they are generally decomposed by heating with an alkali before the distillation commences. The physiological action of alcohol is a subject to which considerable attention has been directed of late years, and many investigators have attacked the problem. The most important contribution to our knowledge of the subject is due to Dr Parkes, who has made a long series of observa tions on soldiers living on a constant diet with and without the use of alcohol. In these experiments the weight of the body, the amount of nitrogen in the urine and faeces, the amount of urea, the pulse, and the temperature of the body were all determined daily. The following are the principal conclusions deduced from the investigation : The elimination of nitrogen during exercise was unaffected by brandy ; and since a similar result occurred in a series of experi ments made during rest, it seems certain that in healthy men on uniform good diet alcohol does not interfere with the disintegration of nitrogenous tissues. The heat of the body, as judged of by the axilla and rectum temperature, was unaffected by the amount given. The apparent heat after alcohol must therefore be owing to subjective feelings connected with the quickened circulation, rather than to an actual rise of temperature. The pulse was increased in frequency by 4 ounces of brandy, and palpitation and breathlessness were brought on by larger doses to such an extent as greatly to lessen the amount of work the man could do, and to render quick movements impossible. As the effect of labour alone is to augment the strength and frequency of thw heart s action, it would appear obviously improper to act on the heart still more by alcohol. Whether on a heart exhausted by- exertion alcohol would produce good or bad effects is not shown by these experiments. Neither exercise nor alcohol produced any effect on the phosphoric acid of the urine, or the free acidity, or the chlorine. As the action of alcohol in dietetic doses on the elimination of nitrogen and on the bodily temperature is so entirely negative, it seems reasonable to doubt if alcohol can have the depressing effect on the excretion of pulmonary carbon which is commonly attributed to it. It can hardly depress, one would think, the metamorphosis of tissues or substances furnishing carbon, without affecting eithe* the changes of the nitrogenous structures or bodily heat.