Cocaine, which is a tropane alkaloid, is a weakly alkaline compound and may thus combine with acidic compounds to produce salts. The hydrochloride (HCl) salt of the cocaine is by far one of the most commonly encountered, although the nitrate (NO3−) and the sulfate (SO42-) salts are seen occasionally. Various salts dissolve either to a lesser or greater extent in different solvents – the hydrochloride salt is polar in character and is quite soluble in water.