135 



ALCOHOLOMETRY. 



ALCOHOLS. 



ISO 



at any temperature within the ordinary range of our climate; but 

 these tables are too voluminous for insertion here. 



In this country it is usual to express the strength of spirits in 

 degrees under or mer proof '; the strength of proof spirit being fixed by 

 Act of Parliament at such a specific gravity that at 51 F. thirteen 

 volumes are equal in weight to twelve volumes of water. Proof spirit 

 has therefore, according to this standard, a density of '9186 at 60, and 

 contains very nearly half its weight of absolute alcohol (49'5 per cent.). 

 Sykes' hydrometer is the instrument in general use by the Excise 

 for estimating the strength of spirits according to this standard, and its 

 scale is so arranged as to show the volume of water which must be 

 added to or abstracted from 100 volumes of the spirit in order to bring 

 it to the proof standard. Thus if the hydrometer indicates 18 over 

 proof, it shows that 18 volumes of water must be added to 100 

 volumes of the spirit to reduce it to proof strength ; whilst 24 under 

 proof signifies that 24 volumes of water must be abstracted from 

 100 volumes of spirit to render it proof ; or in levying the duty upon 

 such spirit, 100 gallons must be reckoned only as 76 gallons, the duty 

 being assessed upon the proof gallon. 



An ingenious method of estimating the alcohol in fermented liquors, 

 without the trouble of previous distillation, has been devised by 

 M. Tabarie' (' Ann. de Chim. et de Phys.' xlv. 222). It consists in 

 boiling a known volume of the liquor, the density of which has been 

 estimated, until the whole of the alcohol has been expelled; then 

 replacing the liquid evaporated by an equal volume of distilled water, 

 and again taking the specific gravity, which will now be found to be 

 higher. A table prepared for the purpose shows the percentage of 

 alcohol from this difference in density. Another and more accurate 

 method of effecting the same object consists in ascertaining the boiling 

 point of the liquor. Water boils at 212 and alcohol at 173, when the 

 barometer stands at 30 inches; consequently a mixture of the two 

 will boil at some temperature between these points, dependent upon 

 the relative quantities of alcohol and water present. Tables of the 

 boiling points of spirits of different but known strengths having been 

 constructed, a reference to these shows at a glance the percentage of 

 alcohol in any sample the boiling point of which has been ascertained. 

 It is found that this method yields results sufficiently accurate with 

 most of the fermented liquors and sweetened spirits in ordinary use, 

 as the sugar and salts present affect the boiling point to a scarcely 

 sensible degree. 



The following table embodies the results of alcoholometrical experi- 

 ments by Br,mde, Cliristison, and others, on the percentage of alcohol 

 in the chief descriptions of wine, beer, and spirits : 



The two first have been long known ; the others have been discovered 

 by the more recent researches of Cahours, Brodie, Balard, Bouis, \Vurtz, 

 and Chancel. 



Most of the alcohols are liquid ; but the three last in the list are solid, 

 at the ordinary temperature. All, except the higher terms of the 

 series, are capable of being distilled without decomposition. By 

 oxidising agencies they pass first into aldehydes, and finally into acids 



CnH(n+ 



H} ( 



and 



Alcohol. 



_CnH(n 1)0, 

 Aldehyde. 



a/ -M>.-<* *fc), 



Aldehyde. Acid. 



In contact with acids under favourable circumstances they yield a 

 series of bodies possessing generally a fragrant odour, and termed ethers 

 or ethereal salt*. [ETHEREAL SALTS.] Heated with the sulphuric or 

 phosphoric acid several of the alcohols lose water and are converted 

 into ethers. The alcohols are produced by various chemical processes ; 

 thus, the methylic, ethylic, and propylic alcohols are derived from the 

 destructive distillation of wood, and of coal ; several, as the ethylic, 

 propylic, butylic, amylic, and caproylic are obtained by the fermenta- 

 tion of saccharine liquids ; the ethylic and propylic may also be pro- 

 duced by acting with water upon a solution of their olifenes (C, H 4 and 

 C, H e ) in concentrated sulphuric acid, whilst the cetylic, cerylic, and 

 melissic are derived from animal secretions. 



Another series of alcohols have the general formula * IT' ^ 2 ; 



it is represented by the allylic alcohol recently discovered by Hofrnanu 

 and Cahours, which contains the radical allyl (C H 5 ), and has the 



f TT T 

 formula "5" \ 2 . Allylic alcohol is obtained by treating the oxalate 



of allyl with ammonia ; oxamide is at the same time produced, according 

 to the following reaction : 



Oxalate of Allyl. 



Allylic Alcohol. Oxamide. 



Allylic alcohol is a very mobile liquid, insoluble with water in all 

 proportions, and possessing a pungent odour irritating the eyes and 

 lungs. It boils at 217, and when ignited burns with a luminous 

 flame. By oxidising agents it is converted into acroleine and acrylic 



