Orange lead, which is a brighter variety of red lead, is prepared from lead salts; white lead or lead nitrite is used for this purpose. The latter salt is made by the process of Pischon, by heating 1 equivalent of lead nitrate with 4 equivalents of granulated lead and water at a temperature between 50° and 60° C. After about 2 hours, the lead nitrite separates in the form of a granular yellow mass. According to Burton’s process, lead carbonate is oxidised by heating with 20 per cent. of sodium nitrate and extracting the mass with water. There are also other methods by which red lead is obtained from litharge by the use of potassium chlorate or saltpetre; but these methods, without producing a finer product than those previously given, are more expensive, and consequently have found no application on the large scale. CHAPTER XIV. OTHER YELLOW PIGMENTS. =Cassel Yellow=, also known as mineral or Veronese yellow, has now a very restricted use; it has been replaced by the deeper and cheaper chrome yellow. Much of the Cassel yellow of commerce is nothing but chrome yellow shaded with barytes. As regards chemical composition, Cassel yellow has the following formula: PbCl₂.7PbO. It is obtained by heating litharge, red lead or white lead with ammonium chloride. To 10 parts of the lead compound 1 part of ammonium chloride is used; on melting, ammonia is set free, by which part of the lead oxide is decomposed, metallic lead separating. The melted mass is poured off from the lead into iron moulds, in which it solidifies to a very crystalline substance of a fine yellow colour. By grinding and levigating, the Cassel yellow is prepared for use. Pale yellow shades, obtained by admixtures of barytes, are occasionally encountered. =Montpellier Yellow= consists, like the preceding pigment, of basic lead chloride. It is obtained by gradually mixing 400 parts of powdered litharge with a solution of 100 parts of common salt in 400 parts of water. After each addition of salt solution the pasty mass must be thoroughly stirred, or it will harden. When all the salt solution has been mixed with the litharge to a homogeneous white mass, the latter is treated with water to remove excess of salt, and the washed material dried and melted in earthenware crucibles. The melt, which has a bright yellow colour, is ground and levigated, when it forms a handsome pigment. There are several other yellow pigments of similar composition, of which one only need be mentioned, obtained by treating a solution of zinc chloride with lead hydroxide. =Turner’s Yellow or English Yellow= is prepared by two methods: either by melting 7 parts of finely ground litharge with 1 part of common salt; or by treating litharge with a solution of common salt and converting the white oxychloride into a yellow pigment by melting.