The Art of Perfumery, and Methods of Obtaining the Odors of Plants

PRACTICAL REMARKS ON SPIRIT OF WINE. BY THOMAS ARNALL. The strength of spirit of wine is, by law, regulated by proof spirit (sp. gr. .920) as a standard; and accordingly as it is either stronger or weaker than the above, it is called so much per cent. above or below proof. The term per cent. is used in this instance in a rather peculiar sense. Thus, spirit of wine at 56 per cent. overproof, signifies that 100 gallons of it are equal to 156 gallons of proof spirit; while a spirit at 20 per cent. underproof, signifies that 100 gallons are equal to 80 gallons at proof. The rectified spirit of the Pharmacopoeia is 56 per cent. overproof, and may be reduced to proof by strictly adhering to the directions there given, viz., to mix five measures with three of water. The result, however, will not be eight measures of proof spirit; in consequence of the contraction which ensues, there will be a deficiency of about [Symbol: oz.]iv in each gallon. This must be borne in mind in preparing tinctures. During a long series of experiments on the preparation of ethers, it appeared a desideratum to find a ready method of ascertaining how much spirit of any density would be equal to one chemical equivalent of absolute alcohol. By a modification of a rule employed by the Excise, this question may be easily solved. The Excise rule is as follows:-- To reduce from any given strength to any required strength, add the overproof per centage to 100, or subtract the underproof per centage from 100. Multiply the result by the quantity of spirit, and divide the product by the number obtained by adding the required per centage overproof, or subtracting the required per centage underproof, to or from 100, as the case may be. The result will give the measure of the spirit at the strength required.