The determination of sodium mercaptobenzothiazole and benzotriazole in inhibited glycol products

Abstract

A polarographic method is described for the determination of sodium mercaptobenzothiazole and benzotriazole in unused inhibited glycol mixtures.

Sodium mercaptobenzothiazole can be determined directly on the sample by using 0·2 M hydrochloric acid as supporting electrolyte and measuring its polarographic wave at –1·26 V. This is an extremely sensitive method and concentrations as low as 1 p.p.m. can be determined in addition to the normal concentration level of 0·2 per cent.

Benzotriazole is also determined polarographically at–1·14 V, with the same electrolyte, after initial separation of the sodium mercaptobenzothiazole on an anion-exchange resin in the chloride form.

Determinations have been successfully carried out in the presence of anti-freeze mixtures containing sodium benzoate, borate, nitrite and phosphate inhibitor systems.