Appearance A white crystalline powder Assay 98.0% to 101.0% Melting point About 185℃ Identification IR Similar with the Reference Spectrum Optical Rotation -15.5°～-17.5° Clearity and color of solution Clear and colourless Metals Not more than 10ppm Arsenic Not more than 2ppm Related Substances Total Not more than 2.0% GSSG Not more than 1.5% Loss on Drying Not more than 0.5% Residue on Ignition Not more than 0.1%