(2) To 3 or 4 parts of caustic baryta moistened with water are added 2 parts of nitrate of barium and 2 parts of oxide of manganese; the whole mass is most intimately mixed, then put into a crucible in a furnace, and subjected to a dull red heat so long as may be necessary for securing complete decomposition. When the green colour is satisfactorily produced, the mass in a state of fusion is poured out, cooled, pulverised, digested in boiling water, then washed with cold water, and finally dried in an atmosphere which is free from carbonic acid. (3) The oxide of manganese may be replaced by the nitrate, when the quantities are 46 parts nitrate of barium, 30 parts of sulphate of barium, and 24 parts of nitrate of manganese; the fusion, grinding and washing are repeated as before. According to some recipes the powdery pigment, consisting essentially of manganate of barium, is mixed with a little dextrine to make sure of its stability, but it is not clear whether this is really essential. MINERAL GREEN.--This is only another name for the green made from copper carbonate, and described under mountain green, see p. 131. MITIS GREEN.--This pigment is an arseniate of copper, and bears a very close relationship to the emerald green made according to Braconnot’s formula, and described in the fifth paragraph of that section, see p. 123. Mitis green is prepared by dissolving arseniate of potash in five times the quantity of hot water and adding a solution of an equal weight of sulphate of copper, keeping the whole in constant agitation. A pulverulent precipitate is formed, possessing a grass green colour. This is washed and dried. The tint can be varied by altering the proportions of the arseniate and sulphate. The arseniate of potash is made by boiling arsenious acid in concentrated nitric acid, filtering, and saturating with carbonate of potash. The arseniate is allowed to crystallise out of the liquor. MOUNTAIN GREEN.--This pigment is also known by the names of malachite and mineral green. (1) In its native form the mineral malachite or green carbonate of copper is very widely distributed in Europe, Asia, America, and Australia, but on a commercial scale it is chiefly produced in the Ural mountains of Siberia and in the Banat of Hungary. It only needs to be picked clean from adhering rock and to be ground to a very fine powder in order to render it ready for use. It is much superior to any of the artificial substitutes referred to below, but its cost confines its application to artistic work. (2) Sometimes a little orpiment or chrome yellow is ground up with the malachite. (3) A very simple formula for making the artificial pigment is to add solution of carbonate of soda or potash to a hot mixed solution of alum and bluestone (sulphate of copper).