Also 7 -chotar, cotar, -kethor. [So in F., Pg. and med.L. (also calcatar), Sp. colcotar, ad. Arab. qolqoṭār (Pedro de Alcalá, 1505), thought by Dozy to be a corruption of Gr. χάλκανθος or χαλκανθές CHALCANTH.]
The brownish red peroxide of iron which remains in the retort after the distillation of sulphuric acid from iron sulphate.
It is used in medicine, in the mechanical arts, and in a finely powdered form by jewellers under the name of rouge; also called Crocus Martis.
1605. Timme, Quersit., I. xiii. 53. The colchotar, or red feces which remayneth in the bottome.
1646. Sir T. Browne, Pseud. Ep., VI. xii. 337. Colcothar or vitriol burnt, though unto a rednesse containing the fixed salt, will make good Inke.
1791. E. Darwin, Bot. Gard., I. Notes 52. The precipitates of gold, and the colcothar of other red preparations of iron, are called tender colours.
1799. G. Smith, Laborat., I. 95. Take red calcined vitriol, or colcothar of vitriol.
1832. G. R. Porter, Porcelain & Gl., 209. The previously polished side is provided with a coating of red colcothar.
b. Formerly applied to analogous compounds of other metals.
1612. Woodall, Surg. Mate, Wks. (1653), 216. This Colkethor is of two … kinds, the one is from the feces of Aqua fortis, and the other from copperas.
1652. French, Yorksh. Spa, vi. 62. The Colcothar … yields upon a refiners tast most pure Copper like to very gold.
1681. trans. Willis’ Rem. Med. Wks., Vocab., Colcothar, Dross of mettals.
