... anhydridedark red orthorhombic crystals or purple flakes. Melting point196, freezing point of 170 ~ 172 Date SheetSpecificationGrade AGrade BGrade CTotal mass fraction ... , % max0,020,05not normalizedTotal mass fraction of Sulphates (SO4), % max0,060,18not normalizedTotal Mass fraction of Sodium (Na), % max0,05not normalizednot normalized ...