Colcothar

noun

1. A brownish-red ferric oxide obtained as a residue after heating ferrous sulfate, used in glass polishing and as a pigment.
2. The brownish-red peroxid of iron which remains after the distillation of the acid from iron sulphate.
3. Polishing rouge; a reddish brown oxide of iron, used in polishing glass, and also as a pigment; -- called also crocus Martis.
4. Polishing rouge; a reddish-brown oxide of iron, used in polishing glass, and also as a pigment; crocus Martis.