_Gen. commentary._ The duties on spirits in England are charged on the number of proof gallons they contain, which is ascertained by gauging or weighing the spirit, and then trying its strength by Sykes’ hydrometer. The per-centage of proof spirit multiplied by the number of gallons gives the net amount of proof spirit to be charged. ‘PROOF STRENGTH’ is an arbitrary standard, adopted for the purpose of facilitating calculations, for which it is well suited; although pure alcohol would, for this purpose, be more simple. As defined by Act of Parliament, 58 Geo. III, c. 28, “proof spirit” is such “as shall, at the temperature of 51° of Fahrenheit’s thermometer, weigh exactly twelve thirteenth parts of an equal measure of distilled water.” Taking, therefore, water at 51° Fahr. as unity, the sp. gr. of “proof spirit” at 51° Fahr. is 12/13 of 1·000 or ·92308. When such spirit is raised to the temperature of 60° Fahr., its density is ·91984. Spirit at “proof” contains very nearly equal weights of absolute alcohol and water; the exact proportions according to recent experiments are:—— --------------------------------------------------------------------- | By VOLUME. | | By WEIGHT. |---------------------------------------| Sp. gr. at | | Bulk before | Bulk after admixture| 60° Fahr. | | admixture. | and condensation. | | ----------------+-----------------+----------------------------------| Alcohol. Water.| Alcohol. Water.| | 100·00 + 103·08 | 100·00 + 81·80 | 175·23 } ·91984 | 49·24 + 50·76 | 57·06 + 46·68 | 100·00 } | --------------------------------------------------------------------- The standard alcohol of the Revenue authorities, and that on which Gilpin’s Tables are founded, is a spirit of the sp. gr. ·825 at 60° Fahr., which is said to contain, by weight, 89% of pure alcohol of ·796; and 92·6% of alcohol, by volume, which corresponds to about 62·5 o. p. It is of great importance to the spirit dealer to be able to estimate correctly the number of ‘proof gallons’ in any quantity of his commodities, or in the whole or any portion of his stock, as disagreeable errors frequently result from ignorance on this point. Calculations of this kind are extremely simple. Thus, when we find, by the hydrometer, that a given sample of spirit is 10 per cent. over-proof, it means, that 100 gallons of such spirit contain as much alcohol as 110 gallons of proof spirit.