By the above elegant and economical process, perfectly pure acetic acid of considerable strength may be produced from even impure alcohol; but it is impossible in this way to obtain a concentrated acid without a subsequent operation, because the action of platinum-black on absolute alcohol, or even on strong alcohol, is so violent that the platinum soon begins to glow, and inflammation ensues. Unfortunately the revenue laws of this country, until lately, stood in the way of the adoption of this beautiful process, unless duty-paid alcohol or methylated spirit be employed; but there is no statute that prevents an individual employing pure spirit, of any strength, on the small scale, for private consumption. In Germany, and in the United States of America, vinegar is manufactured on this plan, and from the low price of crude alcohol there, it will no doubt prove ultimately to be the cheapest source of both pure acetic acid and culinary vinegars. VI. _Miscellaneous Formulæ_:—— 1. An excellent acetic acid, of considerable strength, may be made by soaking fresh-burnt and perfectly dry charcoal in common vinegar, and then subjecting it to distillation. The water comes over first, and on increasing the heat, the acid follows. Vinegar-bottoms and waste vinegar may be used. 2. By exposing vinegar, or dilute acetic acid, to the air in very cold weather, or to freezing mixtures, the water separates in the form of ice, and the strong acetic acid may be obtained by draining it into suitable glass vessels, observing to do so at a temperature sufficiently low to keep the water solid. Said to answer well in cold climates. 3. Acetic acid containing 20% of water may be deprived of a good deal of its superfluous water by standing over dry sulphate of soda. (Liebig.) It may then be used either with or without distillation. 4. Acetic acid, of ordinary strength, may be concentrated to any degree, by rectification once, or oftener, from dry acetate of potash or soda, rejecting the first and last portions. The same acetate may be used repeatedly. The temperature need not exceed 400°, and must not rise above 570° Fahr. ACETIC ACID. (B. P.) _Syn._ ACIDUM ACETICUM. Water mixed with 33% of hydrated acetic acid. Prepared by distilling acetate of soda with sulphuric acid. Colourless sour liquid. Sp. gr. 1·044.