LIME, ACETATE OF.—This salt, in its pure solid state, forms silky needle-shaped crystals with a bitter taste, which effloresee iu the air, and are soluble in water and alcohol. Decomposed by the action of heat, acetone and carbonate of lime are formed. It is obtained by dissolving chalk in acetie acid until there is a slight excess of lime. The commercial article is of two descriptions, grey or white, sometimes called " distilled," and brown. Acetate of lime liquor is largely used in the manufacture of red liquors, having some such constitution as the following :— Aeetie aeid 9.50 Cloride of calcium 0.50 Chloride of sodium .. 3.22 Tarry matter .. 3.83 Water .. 77.75 100.00 Upon a large seale the manufacture of lime acetates is carried on as a continuous process with that of the production of crude or pyroligneous acid, and the reader must therefore refer to that point in the description of wood-distillation, where the acid liquors, consisting of water, pyroligneous acid, naphtha, and various resinous and tarry matteis, are run off from the tar-settlers and pumped either into the " neutralizer " or into stills. By the former process, when the lime is added to the whole body of acid liquors, brown acetate is produced ; by the latter, grey. Taking the brown acetate proeess first, roughly powdered chalk, sometimes milk of Hine, is added to the liquors in the neutralizer until by the litmus test there is a very slight excess. The mixture is well stirred from time to time, and the light tarry substances which rise as a scum to the surface skimmed off. After being allowed to settle for a short timo the liquors are run or siphoned off into a still or boiler. Heat is applied from a fire placed directly underneath, or from a coil of steam piping within the still, and the naphtha compounds and bulk of the water are driven off. Convenient forms of this apparatus are shown in Figs. 31 and 32. In Fig. 31 A is a copper still in the form of a boiler, B the fireplace, C the exit pipe for the naphtha. When the latter ceases to come over, the acetate
of limo liquor left in the still is run into an evaporating pan, and heat again applied from a tire below the pan or by a coil of steam-pipea in the Ihfu.or. lkre it is kept gently simmering, and once more are the tarry impurities skimmed off as they rise. After a while the acetate crystallizes out from the concentrated liquor and forms a thin coat ing, which is taken off and put into baskets or any convenient form of drainer set on runners over the liquor. When drained it is carried up into the drying house, usually built on the top of the ovens. Two forms of evaporating pan arc shown in Figs. 33 and 31. The first is the best, as the salt raked up upon the shelving and of the pan shown in Fig. 84 is apt to burn, and the drainings arc returned to the pan cold. In some works the acetate liquor, instead of bchig allowed to crystallize out in tho manner described, is boiled down to dryness in a pot of the form shown in Fig. 35. In this way, only an inferior article is obtained, but by evaporating to dryness in a shallow sheet iron pan, similar to that shown in Fig. 33, and by carefully supervising the operation, a very fine acetate may be obtained indeed, given the necessary experience and care, this is the best method of finishing.
The acetate is spread upon the floor of the drying house in a layer from 2 to 3 in. thick, and must be carefully turned from time to time. The chief end of drying being to burn off gently and uniformly the carbonaceous and oleaginous substances con tained in the salt, its manipulation in the drying house requires considerable care, skill, and attention. If spread in too thick a layer, or if not completely and carefully turned, these impurities arc retained and the salt itself is decomposed. A good brown acetate is composed of light honeycombed fragments streaked here and there with charcoal, and with a pleasant, fresh smell. It should contain 70 per cent. of real acetate.