In commerce there are many qualities of black, the names of which are generally chosen quite arbitrarily. The so-called ivory black is an example of this. At some period it was observed that ivory produced a very fine black when carbonised; this black was made for a long time from refuse ivory. When it was found that a similar black could be made quite as well from much cheaper materials, it was no longer made from ivory. The name, however, remains in trade to the present day: it has come to be regarded as a description of quality. By the name of ivory black a fine black pigment is understood; it is immaterial to the consumer whether it is made from ivory or not: to him the quality of the pigment, but not its source, is important. According to the method of production, the black pigments can be divided into charcoal blacks and soot blacks. CHARCOAL BLACKS. This term is applied to the pigments obtained by heating organic substances in the absence of air. The charcoal blacks have two valuable properties: they are easily made, and they exhibit a pure black shade which it is far more difficult to obtain with the soot blacks. It is very difficult to convert these pigments into the requisite state of fine division. They cannot be levigated on account of their low specific gravity, which causes them to settle very slowly in water. It only remains to convert the charcoal into a very soft powder by grinding, but even then the pigment has but little covering power, because it is not possible to destroy the organic structure of the substance carbonised. When the finest charcoal powder, made by carbonising any organic substance, is examined under a powerful microscope the structure of the particles is at once recognised, so that it is almost always possible to decide whether the charcoal is of plant or animal origin. A very careful examination may show what particular part of the plant has been carbonised. If a manufacturer succeeded in producing by direct carbonisation a black with the covering power of a soot black, that black would soon be the only one found in commerce. The charcoal blacks come on the market under various names—ivory black, bone black, vine black, Frankfort black, Paris black, etc. The ivory blacks are the best quality, but recently true vine black, _i.e._, made from grape residues, has come into use.