BONEBLACK, ANIMAL CHARCOAL, or CHAR. A substance prepared from carefully selected, clean, hard hones, made by heating them in retorts, out of contact with air, until they are carbonized. In this process combustible gases and water, together with oil and the va pors of various salts of ammonia, are given off, and boneblack is left in the retort. It is gen erally reduced to coarse grains from about the size of small peas, down to large pinheads. and is extensively used in the arts for deeolorizing liquids, such as the syrup of sugar, and solu tions of argol (impure cream of tartar). It is capable of removing various mineral substances from their solutions, and is therefore used in filters for separating chemical impurities from water. The general mode of using the bone black for the purpose of &colorizing liquids is to allow the liquid to percolate through a layer of the charcoal, when all color is arrested. and the syrup of sugar runs through clear aml colorless. This power of absorbing coloring mat ters is possessed also by vegetable (peat or wood) charcoal, but not. to such an extent as by boneblack. The application of heat to the liquids before filtration greatly facilitates the decoloriza tion, and where the volume of liquid to be oper ated upon is not great, the most expeditious method is to boil the liquid and boneblack to gether, and then strain through filtering-paper or cloth. The power of absorbing colors appears
to be due to the porosity of the substance; it is extremely improbable that the absorption of color is due to a chemical process. When syrup of sugar and other liquids have been run through boneblack for some time, the pores of the latter appear to get clogged with the color, and the clarifying influence ceases; then the bone black requires to undergo a process of revivifica tion, which usually consists in reheating it care fully in ovens, or iron pipes inclosed in a fur nace, when the absorbed color is charred, and the boneblack can be of service once again as an arrester of color. After several the boneblack becomes of very inferior absorptive quality, and is disposed of for the manufacture of fertilizers. Boneblack has also the power of absorbing odors, especially those of a disa greeable nature, and can be employed to deodor ize apartments, clothing, outhouses, etc. See BONE FERTILIZERS.