Acetate of soda is used chiefly in the production of the best qualities of acetic acid, by distil lation with sulphuric acid in the manner already described ; to some slight extent in the preparation of naordants, and in the preservation of animal and vegetable substances. One of its chief virtues as a preservative is that substances treated with it can be readily restored before use to their original appearance or couaistency. The plan usually adopted is as follows :—The flesh to be preserved is sandwiched with powdered acetate of soda in a cask, in the proportions of about one part of the salt to four of flesh. Without being changed in constitution, the acetate abstracts the moisture from the flesh, and when the latter is withdrawn, may be used over again. To ensure the success of the process the temperature should not be below about 15° (60° F.), so that in winter the casks "in pickle" must be kept in a warmed room. The operation usually takes a couple of days, at the end of which time the flesh is dried in the air and packed. A little powdered sal-ammoniac is sprinkled over the meat, or fish, before cooking, and it is then thoroughly steeped in tepid water. The sal ammoniac decomposes the acetate of soda, forming common salt (chloride of sodium) and acetate of ammonia, and the flesh resumes its normal appearance. Vegetables may be preserved in acetate of
soda " pickle "—a liquor formed by dissolving the salt in three parts of water—in somewhat similar fashion.
The demand for acetate of soda has diminished of late years owing to the increased use of lime acetate as a source of acetic acid. There are now only about eight manufacturers in this country who are keeping their plant at work, the chief seat of the trade being South Wales.
STANNOTd ACETATE.-- Acetate of the protoxido of tin is an unstable salt, crystallizing out in colourless needles from a strong solution of metallic tin in acetic acid. Upon a larger scale it is prepared by mixing solutions of tin crystals (chloride of tin) and acetate of soda, limo, or lead, a usual recipe being 103 parts of tin salt to 190 of good brown acetate of lead ; the mixture is well agitated, allowed to settle, and the clear supernatant acetate of tin drawn oft Owing to a tendency to undergo oxidation upon exposure to the air the solution should only be prepared for immediate use. The salt is employed in dyeing and calico-printing to a limited extent to obtain nu orange colour. It is, however, an uncertain agent from its unstable character, and gives, moreover, a " loose" colour, a defect that it shares with all other tin mordants on vegetable fibre.