Black pigments with a basis of carbon

The principal of these are Soot black, which includes resin black, tar black, lamp black and acetylene black slate black, obtained from bituminous shales lignite black and peat black vegetable blacks, including charcoal black, vine black, pine Hack, etc. animal blacks, the chief of these being bone black and others ivory black, horn black, etc. 

Mixtures of these blacks either with one another or with inert materials are also sold, sometimes under special names. 

The examination of black pigments comprises certain technical and physical tests, indicated in paragraphs 1-3, and also chemical tests and determinations (paragraphs 4-7) for the purpose either of distinguishing the different products from one another (especially the determination and examination of the ash) or of ascertaining their purity and value. 

Quality and Intensity of the Colour.—These are determined by the general methods, particular care being taken to note if the colour is a pure black or if it shows more or less traces of brown, reddish, greenish, etc. as regards the intensity, it is well to examine black pigments—always in comparison with a typical black—with reference to their behaviour when mixed not only with a white but also with other pale pigments. 

Specific Gravity.—This is determined more especially with soot black by means of a picnometer at 150 C., alcohol of at least 95 % concentration being employed as liquid. 

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