AC′ETATED (ăs′-). In chemistry and pharmacy, combined or impregnated with acetic acid or vinegar.
ACE′TIC. Syn. Ace′ticus, L.; Acétique, Fr. Of or relating to vinegar; made with acetic acid, as perfumes, &c. (See below.)
ACETIC ACID. HC2H3O2. Syn. Pyrolig′neous acid (pure); Acid of vinegar; Acidum ace′ticum, L.; Acide acetique, Fr.; Acido acetico, It.; Essigsäure, Ger.; Azynzuur, Dut.; Eisel, Sax. When free from water it crystallises on cooling, and is distinguished as—Acetic hydrate, Hy′drated acetic acid, Monohy′drated a. a., Gla′cial a. a., Monohydrated a. a., Ace′tum glacia′le, Acidum ace′ticum G., L., &c. the sour principle of vinegar.
Var. Commercial acetic acid is found under the form of the pure acid of the chemist and pharmaceutist (glacial and dilute), and of vinegar, of which there are several varieties, which are noticed under their respective heads.
Sources. Fermented liquors; the vinegars of commerce; alcoholic liquors; wood, from which it is obtained, as pyroligneous acid, by distillation; the commercial acetates of soda, potassa, lime, lead, copper, &c. The pure acetic acid of the chemist and of commerce is almost wholly obtained from the acetates, either by the action of a strong acid, which seizes on the base, setting the acid free; or, by dry distillation, in which the high degree of heat employed separates the acetic acid from the base in the form of vapour. It is also obtained by the oxidation of alcohol.
Prep. The following are the principal processes at present adopted to obtain pure acetic acid:—
1. From the Acetates in the moist way:—
a. From ACETATE OF SODA:—
1. Commercial acetate of soda (i.e., the ‘pure acetate’ of the pyroligneous acid works), in crystals, is put into the body of a stout copper still, and a deep cavity being made in the centre of the mass, about 35% of sulphuric acid of a sp. gr. of not less than 1·84 is poured in; the walls of the cavity are then thrown in upon the acid, and the whole briskly agitated, for a very short time, with a large wooden spatula; the head of the still is next luted on, and the distillation conducted at a gentle heat, the receiver being changed as soon as the distillate begins to acquire a slight empyreumatic odour. The product, when the process is well managed, is an almost colourless acid of the sp. gr. of fully 1·05, containing about 40% of glacial acid, or between 34% and 35% of anhydrous acid. Any trace of colour or empyreuma is removed by agitation with some well-washed and recently ignited vegetable charcoal, or with a very small quantity of recently ignited purified animal charcoal, and subsequently passing it through a prepared calico bag-filter; or by allowing it to stand, for about a fortnight, in barrels containing some beech-wood chips; after which it is ready for sale, either as the ordinary acetic acid or pure pyroligneous acid of commerce, or (on dilution, &c.) as vinegar.
2. The acid of sp. gr. 1·05 (obtained as above) is distilled with fused chloride of calcium, the distillate being run into a refrigerator; the crystals that form are drained at a temperature below 40° or 45° Fahr., and after removal to a warmer temperature, where they liquefy, and agitation with a little peroxide of lead, are submitted to a second distillation, as before; and this is repeated until the whole of the acid crystallises at 51° Fahr. The product is the glacial acetic acid of commerce.