ALCOHOLOMETRY 



61 



And now, by reference either to Drinkwater's, Tralla's, or Gay-Lussac's Tables, 

 ihe operator will be enabled to find, by the knowledge of the density or specific 

 gravity, at the temperature at which the operation was performed, the per-centage of 

 real alcohol, either by weight or by volume. 



In France, Gay-Lussac's alcoolometre is usually employed. It is a common glass 

 hydrometer, with the scale on the stem divided into 100 parts or degrees. The 

 lowest division, marked 0, denotes the specific gravity of pure water ; and 100, that 

 of absolute alcohol, both at 15 C. (59 F.) The intermediate degrees, of course, 

 show the per-centage of absolute alcohol by volume at 15 C. ; and the instrument is 

 accompanied by the Tables already given for ascertaining the per-centage at any 

 other temperature. 



Alcoholometry of Liquids containing besides Alcohol, Saccharine Matters, Colouring 

 Principles, $c., such as Wines, Beer, Liqueurs, $c. 



In order to determine the proportion of absolute alcohol contained in wines, or 

 other mixtures of alcohol and water with saccharine and other non-volatile sub- 

 stances, the most accurate method consists in submitting a known volume of the 

 liquid to distillation (in a glass retort, for instance) ; then, by determining the specific 

 gravity of the distilled product, to ascertain the per-centage of alcohol in this distil- 

 late, which may be regarded as essentially a mixture of pure alcohol and water. 

 The distillation is carried on until the last portions have the gravity of distilled 

 water ; by then ascertaining the total volume of the distillate, and with the knowledge 

 of its per-centage of alcohol and the volume of the original liquor used, the method of 

 calculating the quantity of alcohol present in the wine, or other liquor, is sufficiently 

 obvious. 



In carrying out these distillations care must be taken to prevent the evaporation of 

 the spirit from the distillate, by keeping the condenser cool. And Professor Mulder 

 recommends the use of a refrigerator, consisting of a glass tube fixed in the centre of 

 a jar, so that it may be kept filled with cold water. The tube must be bent at a 

 right angle, and terminate in a cylindrical graduated measure-glass, shaped like a 

 bottle. 1 



It is well to continue the distillation until about two-thirds of the liquid has passed 

 over. 



This process, though the most accurate for the estimation of the strength of alco- 

 holic liquors, is still liable to error. The volatile acids and ethers pass over with the 

 alcohol into the distillate, and, to a slight extent, affect the specific gravity. This 

 error may be, to a great extent, overcome by mixing a little chalk with the wine, or 

 other liquor, previous to distillation. 



By this method Professor Brando made, some years ago, determinations of the 

 strength of the following wines, and other liquors : 2 



Proportion of Spirit per Cent, by Measure. 



1 The Chemistry of Wine, by G. J. Mulder, edited by H. Bonce Jones, M.D. 

 Brando's Manual of Chemistry ; also Philosophical Trans. 1811. 



