Appearance Colourless crystals or white powder; odourless Loss on drying Not more than 1.0% Assay Between 99-100.5% Solubility Very soluble in water; freely soluble in glycerin; soluble in ethanol (95%) Arsenic Not More Than 2 ppm Heavy metals Not More Than 10 ppm Iron Not More Than 20 ppm Barium No turbidity develops within one minute Cyanide No blue color is produced Iodate No blue color is produced within 2 minutes Sulphates Not More Than 150 ppm Thiosulphate A blue color is produced