Minerals and Metals in Ancient India v2.c45.s5.4

v2.c45.s5.4

Viḍa/viṭ or black-salt probably used to be prepared by fusing common salt with sodium sulphate or *sājimāṭi* and organic materials like the fruit of *T. Chebula*. The reddish brown colour of *viḍa* is due to reduction of the sodium sulphate to sulphide which converts the iron impurity (this as well as sulphate come from the common salt) to the coloured sulphide. The material was used medicinally to aid digestion. (Ray, 1956: 205)