Sulphate of iron, or green vitriol; a salt of a peculiar astringent taste, and of various colors, green, gray, yellowish, or whitish, but more usually green. It is much used in dyeing black and in making ink, and in medicine, as a tonic. The copperas of commerce is usually made by the decomposition of iron pyrites. The term copperas was formerly synonymous with vitriol, and included the green, blue and white vitriols, or the sulphates of iron, copper and zink.
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Copperas
Encyclopedia Britannica
COPPERAS (French, couperose ; Latin, cupri rosa, the flower of copper), melanterite, green-vitriol, or ferrous sulphate, is a salt of iron of the composition FeSO 4 , 7H 2 O. Ithas a bluish-green colour and an astringent, inky, and somewhat sweetish taste. It crystallizes in oblique rhombic prisms of the monoclinic system, but generally occurs renifυrm, botryoidal, incrusting, stalactitic, pulverulent, or massive in nature. It is readily dissolved by water, but is insoluble in alcohol. On exposure to the air it effloresces slightly, and if moist becomes coated with a basic ferric sulphate having, according to Berzelius, the formula 2Fe 2 O 3 , SO 3 , or Fe 2 (SO 4 ) 3 .5Fe 2 O 3 . If precipitated from its aqueous solution by alcohol, copperas does not readily absorb oxygen. 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 2 , in a damp atmosphere. The oxidation of the pyrites of coal to ferrous sulphate tends to promote the disintegration of the coal; occasionally, in the presence of shale, it gives rise to the formation of finely crystallized “feather-alum,” FeAl 2 (SO 4 ) 4 , 24H 2 O. 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 Alum, vol. i. p. 646). It may also be prepared by Spence’s method of heating ground puddling-furnace slag, tap-cinder, or Cleveland or black-band ironstone with sulphuric acid. A factory for making copperas from the pyritous nodules of the clay of the Island of Sheppey, is said to have been established at Queenborough by ...Matthias Falconer, a Brabanter, in 1597.
Copperas is used in dyeing and tanning, in the manufacture of ink, Prussian blue, and Nordhausen sulphuric acid or fuming oil of vitriol, in medicine as an astringent and tonic, and in analytical chemistry. In the 13th century it was in request for sheepdressing. When calcined it yields first a white salt, FeSO 4 ,H 2 O, the ferri sulphas exsiccata of pharmacy, and finally brownish-red ferric oxide or colcothar of vitriol (colcothar vitrioli, caput mortuum, or crocus Martis), employed as a paint and polishing-powder. Colcothar may also be prepared by calcining a mixture of 100 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.
9th ed. Encyclopædia Britannica, vol. 6, p. 352
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Greenness Roget’s Thesaurus §435
N. green, blue and yellow, vert #, emerald, verd antique, verdigris, malachite, beryl, aquamarine, absinthe, creme de menthe, terre verte, verditer, verdine, copperas, greenness, verdure, viridity, viridescence, verditure, glaucoma, [Jap: rokunaisho]
Adj. green, verdant, glaucous, olive, olive green, green as grass, verdurous, emerald green, pea green, grass green, apple green, sea green, olive green, bottle green, coke bottle green, greenish, virent, virescent, green (learner) 541, (unskillful) 699, green
Phr. green with envy, the green grass of ireland, the wearing of the green
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