SODIUM, ACETATE OF (len. Terre foliee ; GER. Essigsiiure natron.)--This salt, one of the most huportant or the acetates, forms small oblique rhombic prisms, soluble in 31. parts of cold, and lit parts of hot water ; also in alcohol, in various proportions depending upon the strength of the solvent. In its erystalline form it containa 3 atoms of water, which it loses when exposed in dry air. A liquid supersaturated solution may be formed by melting the crystals, and allowing the salt to deliquesce. In this way they take up aeven atoms of water, the solution immediately erystnllizing upon agitation with a small piece of the dry acetate. Gerardin has made some curious experiments touching the solubility of this salt in alcohol ; with a solvent of 0.9904, and at the ordinary temperature of the air, SS parts of the acetate are dissolved, hut the uleohol loses its iieteney very rapidly upon concentration.
Acetate of soda may be obtained in a pure state by crystallization from an evaporated and cooled solution of carbonate of soda in pure acetic acid ; or, of slightly worse quality, from a saturated solution of tho in " second" acid—that obtained from the distillation of acetate of lime with eulphuric or hydrochloric acid. On a large scale a good commercial steetate is produced in the following manner :—Grey acetate of lime is dissolved in water until the solution stands ut 1.15 to 1.2 specific gravity. It is theu filtered and run into a shallow sheet-iron vessel about 6 ft. long, 4 ft. wide, and 2 ft. deep. Hero ground or roughly powdered aulphate of soda is slowly added, the mixture being kept well stirred up, until the whole of the lime separates in the form of sulphate. The proportions usually employed are 4 parts of sulphate of soda to 1 part of acetate of lime. The
mixture should be carefully tested from time to time to ascertain if the whole of the lime has been precipitated. The addition of a little sulphate solution to a sample of the liquor will readily ahow when this point haa been reached. When the precipitation is complete the sulphate of lime is allowed to settle down, and the clear supernatant acetate of soda liquor is siphoned off to the evapo rating pans, which are of similar desoription to the mixing pan, heated by a fire beneath. The reaiduc, which consists of sulphate of lime and vurious insoluble matters, is thoroughly washed with hot water that no acetate of soda may be wasted, the first washinge being added to the liquor in the evaporating pan, and the weaker run off to aid in the dissolution of a fresh batch of grey acetate. Sometimes the liquors are evaporated in cast iron pots, 6 ft. in diameter and 3.4 ft. deep, instead of sheet-iron pans. Here they are boiled down till a density of 1.30 is attained. During concentra tion whatever excess of sulphate of soda has been used crystallizes out and is scraped off and thrown into drainers, usually winker baskets, placed on rods laid across the pan or pot, so that all the acetate of soda liquor may readily find its way back to the main body of solution. All impuri ties that rise to the aurfaee during concentration aro also carefully skimmed off. After being allowed to settle thoroughly, an operation usually requiriug about nine hours, the clear liquor is run or siphoned off to small copper crystallizing pans, when it is allowed three or four days to set. The