VOL. LXXXIV.] PHILOSOPHICAL TRANSACTIONS. 42/ 



spirituous liquors would be, to consider rectified spirit as the true and only ex- 

 cisable matter." 



It may be proper to add a short account of the method pursued in computing 

 some of the columns of these tables. Columns 1, 2, 3, require no other ex- 

 planation than has been already given. Col. 4 is obtained thus : divide the 

 specific gravity of the pure spirit, at the temperature in the table, by the 

 specific gravity of water at the same temperature : then, for the first of the two 

 tables for each degree of heat, the proportion is, as 100 is to the quantity of 

 water by weight in the first column, so is the quotient of the above-mentioned 

 division to the quantity of water by measure sought ; for the 2d of the 2 tables 

 the proportion is, as the quantity of spirit by weight in the first column is to 

 100, so is that same quotient to the quantity of water by measure sought. 



Col. 5 requires more calculation. The first step is to compute what the 

 specific gravity of the mixture in question would be if no concentration took 

 place; to obtain which, the constant number 100 (indicating the quantity by 

 measure) of pure spirit, is to be multiplied by the specific gravity of pure spirit 

 at the temperature in the table, and the corresponding measure of water in the 

 4th column is also to be multiplied by its specific gravity at the given tempera- 

 ture ; these 2 products being added together, their sum is to be divided by the 

 sum of the absolute quantities of spirit and water by measure in the same hori- 

 zontal line of the 3d and 4th columns : then the proportion is, as this quotient 

 (or what the specific gravity would be without concentration) is to the real spe- 

 cific gravity as found in the same horizontal line of the 2d column of the table, 

 so is the sum of the quantities of spirit and water in the 3d and 4th columns 

 inversely to the bulk of the mixture. 



Col. 6 is obtained by subtracting the real bulk of the mixture in col. 5 from 

 the sum of the quantities of spirit and water in col. 3 and 4, the difference 

 between them being the diminution occasioned by the concentration on that 

 whole quantity. Col. ^ is obviously to be computed by the following propor- 

 tion : as the bulk of the whole quantity of the mixture in col. 5, is to 100 (the 

 constant quantity), so is 100 to the quantity of pure spirit per cent, at the tem- 

 perature of the table. Col. 8 is formed by reducing the volume of the spirit 

 per cent, at the temperature of the table, to its volume at 6o°, by the following 

 proportion: as .825 (the specific gravity of pure spirit at 6o°) is to its specific 

 gravity at the given temperature, so is the number in the 7th column to the 

 volume of pure spirit, at 6o° of heat, contained in 100 parts by measure of the 

 mixture at the temperature of the table : this divided by 100 is the decimal mul- 

 tiplier sought ; the product of which into any measure of a spirituous liquor of 

 the corresponding specific gravity and temperature, will be the true quantity of 

 standard pure spirit, at dO° of heat, contained in that liquor. 



3 I 2 



