COPPERAS (French, couperose ; Latin, csipri rosa, the flower of copper), melanterite, green-vitriol, or ferrous suloxygen. When heated to 114° C. it loses six molecules of water, but the last molecule is not given up at a temperature of 280' C. Copperas is frequently found in metalliferous mines, being produced by the oxidation of marcasite and iron-pyrites, FeS,, in a damp atmosphere. The oxidation of the pyrites of coal to ferrous sulphate tends to promote the disintegration of the coal ; occasion. ally, in the presence of shale, it gives rise to the formation of finely crystallized "feather-alum," FeAl,(SO4)4, 24E120. Copperas is manufactured, with alum, by the oxidation of the iron-pyrites contained in aluminous schists, such as those of the Coal measures of Renfrew and Lanark (see the clay of the Island of Sheppey, is said to have been established at Queenborough by Matthias Falconer, a Bra,banter, in 1597.

parts by weight of copperas with 42 of common salt, and washing out the resulting sodium sulphate. Jeweller's rouge or plate-powder is the washed and calcined precipitate of ferric oxide obtained by adding solution of sodium carbonate to solution of copperas.