ANIMAL CITARCOM„ or IvonY-BLAcK, is prepared from bones by heat ing them in close retorts till they undergo' the process of destruefive distillation, when combustible gases and water, together with the vapors of various salts of ammonia, and oil, are given off, and boneblack is left in the retort. It is generally reduced to coarse grains from about the size of small peas, down to large pinheads, anti is exten sively used in the arts for decolorizing liquids, such as the syrup of sugar, and solutions of argol (impure cream of tartar), and of the alkaloids, as also in filters '(q.v.). for separat ing chemical impurities from water. The general mode of using, -the bone-black is to allow the colored liquid to percolate through a layer of the charcoal; when all color is arrested, and the syrup or water runs clear and colorless from under the stratum of char coal. This power of absorbing coloring matters is also observable in vegetable (peat or wood) charcoal, but not to such an extent as in bone-black. The application of heat to the liquids before filtration greatly facilitates the decolorization, and where the volume of liquid to be operated upon is not great, the most expeditious method is to boil the liquid and bone-black together, and then Strain through filtering-paper or cloth. The composi tion of bone-black in 100 parts is 10 of pure charcoal, associated with 90 of earthy salts —that is, in the proportion of 1 of pure charcoal in 10 of the commercial bone-black. The power of absorbing colors appears to be due to the porosity of the substance, and is not resident simply in the pure charcoal; indeed, the earthy matters (principally phosphate of lime carbonate of lime) can be dissolved out of the bone-black by dilute hydrochloric acid, and the pure charcoal thus obtained only possesses about one third the decolorizing power of the total amount of bone-black it was obtained from.
Thus, if 100 parts of ordinary hone-black have the power of arresting the color from ten volumes of a given colored liquid, then the 10 parts of -pure charcoal which can be obtained from the 100 parts of bone-black will be found to decolorize only three volumes of the same colored liquid; so that it is apparent the earthy matters in the bone-black influence and increase the absorption of the coloring matter, and thus render a given weight of the charcoal of greater commercial value. When syrup of sugar and other liquids have been run through bone-black for some time, the pores of the latter appear to get clogged with the color, and the clarifying influence ceases, and then the bone-black requires to undergo the process of retie:potion. which consists in reheating it carefully in ovens, or iron pipes inclosed in a furnace, when the absorbed color is charred, and the bone-black can be of service once as an arrester of color. After several re the bone-black becomes of very inferior absorptive quality, and is then dis posed of for the manufacture of bone-ash and dissolved bones (q.v.). Bone-black has likewise a great power of odors, especially those of a disagreeable nature, and can thus be employed to deodorize apartments. clothing. outhouses, etc., or wherever animal matter may be passing into a state of active putrefaction.