Diltiazem HCl is (2S,3S)-3-acetoxy-2,3-dihydro-2-(4-methoxyphenyl)-5-(2-dimethyl)-1-5-benzothiazepine-4(5H)-one monohydrochloride. It occurs as white crystals or crystalline powder and is odorless. It is very soluble in formic acid, freely soluble in water, in methanol and in chloroform, sparingly soluble in acetonitrile, slightly soluble in dehydrated ethanol and in acetic anhydride, and practically insoluble in ether. Melting Point: 210-215°C (decomposition).