Bone Black

Bone Black, a mixture of charcoal (10 per cent.) with various inorganic salts, chiefly calcic phosphate, known also as "animal charcoal," and obtained by heating bones. The bones, preferably sheep or ox bones, are first boiled for some time to remove fatty matters, then dried and heated strongly in iron retorts. Gases pass off, some of which condense forming bone oil (q.v.); the uncondensed portion, after purification, may be employed for illuminating or heating purposes. The bone black is left in the retorts, is taken out, crushed and ground between stone or steel cylinders. It is largely used in the manufacture of blacking, in sugar refining, and as a pigment.