The precipitate is allowed to settle. It is then well washed with water by decantation, filtered rapidly, and brought on to boards, where it is allowed to dry slowly. During the drying process, the colour swells up, and care should be taken that this swelling takes place on the boards, and not on the filters. Shades can be obtained from light yellow to dark orange, and almost red. By mixing together some lead bichromate or chromate with the lead acetate solution, a precipitate is obtained of a dark lemon colour; and by mixing caustic alkali with the precipitate on the filter, a much redder shade can be obtained. (Text. Colourist)

Naples-Yellow

(a) Mix 3 lb. powdered metallic antimony, 1 lb. oxide of zinc, and 2 lb. red-lead; calcine, grind fine, and fuse in a closed crucible; grind the fused mass to fine powder, and wash well. (6) Grind 1 part washed antimony with 2 parts red-lead to a stiff paste with water, and expose to red heat for 4 to 5 hours.

Orpiment

Orpiment (arsenic tri-sulphide) is a lemon or orange-yellow coloured substance, found native in Hungary, the Hartz, and other places; the finest samples used by artists (golden orpiment) come from Persia. The commercial article is artificially prepared for use as a pigment in the following way: - A mixture of arsenious acid and sulphur is placed in an iron subliming-pot, similar to those used in the preparation of crude white arsenic. The mixture is heated until the sublimate, which immediately forms upon the rings fixed above the pot, begins to melt. The proportions of the 2 ingredients used vary largely, the best colours being probably produced when the mixture contains 1/3 to 1/5 of sulphur; for the lighter colours, a smaller proportion of sulphur is employed. Orpiment made in this manner consists of a mechanical mixture of arsenic sulphide and oxide. The native sulphide is preferred to the artificial by artists and dyers, by reason of its richer colour.

Yellow Lakes

(a) Boil 1 lb. Persian berries, quercitron-bark, or turmeric,and 1 oz. cream of tartar, in 1 gal. water till reduced to half; strain the decoction, and precipitate by solution of alum. (6) Boil 1 lb. of the dyestuff with 1/2 lb. alum in 1 gal. water, and precipitate by solution of potash carbonate, (c) Boil 4 oz. annatto and 12 oz. pearl ash in 1 gal. water for 1/2 hour; strain, precipitate by adding 1 lb. alum dissolved in 1 gal. water till it ceases to produce effervescence or a precipitate; strain, and dry.

Paint

Paint consists essentially of two parts - (1) the vehicle or medium, and (2) the pigment. In the case of oil-paints, a third substance becomes necessary, to facilitate the drying or solidification of the vehicle; this is termed a "drier."