by the metal. A table giving the specific gravities of solutions of the more important acetates of different strengths will be found under the heading Hydrometers and Hydrometry. For the acetate of any metal or radical, see that metal or radical. Thus, for Acetate of Silver see Silver.
Acetic Acid (Ger., Essigsaure; Fr., Acide Acetique; Ital. Acido Aceticd). Formula, HC2H302; molecular weight, 60; synonym, Purified Pyroligneous Acid. The earliest known acid. In dilute form as vinegar by the fermentative oxidation of alcohol, but now largely prepared from wood by destructive distillation and subsequent purification. There are three com-mercial strengths.
Glacial Acetic Acid contains about 99 per cent, of acid and 1 per cent, of water. Its specific gravity varies from 1.065 to 1066. When cooled to 340 F. it solidifies into a mass of crystals, and remains solid till the temperature is raised. From this property is derived the term glacial. Care should be exercised in handling this, as it is a powerful escharotic; if any should by chance be spilt upon the naked skin, it should be washed off immediately. It is a poison, by reason of its caustic properties - the obvious chemical antidote being chalk or carbonated alkalies; but caution should be exercised lest the antidote should be worse than the poison. It is miscible with water and alcohol in all proportions, and is a solvent of pyroxyline.
Commercial "Strong" Acetic Acid,. This is one-third the strength of the glacial acid, and contains about 33 per cent, of real acid. It can be conveniently prepared from the glacial acid by mixing with it twice its own quantity of distilled water. It is sometimes known as " Beaufoy's Acetic Acid." Specific gravity, 1-044.
Dilute Acetic Acid. Made by mixing 1 part of " strong'' acid and 7 parts of distilled water, and sold as "distilled vinegar." Specific gravity, roo6. It contains about 4^ per cent, of acid. The impurities in the acetic acids may be sulphurous acid or tarry matter, hydrochloric acid, or sulphuric acid. Samples sold for photographic use are, however, usually sufficiently pure. Any sample which gives a precipitate when a drop of strong silver-nitrate solution is added to one-fourth of an ounce, or