A dark, viscous,usually pungent substance, tar is derived from the destructive distillation of various organic compounds such as wood,coal, or shale,that is used for various industrial purposes.
4-(2-Thiazolylazo)resorcinol is used in treatment of psoriasis.
Dissolve it in aqueous alkali, extract it with diethyl ether, and re-precipitate it with dilute HCl. The purity is checked by TLC on silica gel using pet ether/diethyl ether/EtOH (10:10:1) as the mobile phase. It complexes with Cu2+ (pH 3-4), Co2+ and Ni2+ (pH 7) and Zn2+ , andCd2+ (pH 8.4). [Beilstein 27 III/IV 5988.]
