Polarographic Behaviour of Chromium(VI) at the Dropping Mercury Electrode

Department of Chemistry, Saugar University, Sagar Received 25 September 1970; ReviBed MSS reuived 18 November 1971; accepted for publication 9 February 1972 Kolthoff and Lingane1 have observed the polarographic reduction of chromate ions in sodium hydroxide. A single well defined wave was obtained with ·a half-wave potential of -0·85 volts. Urone et al.2 have described a polarographic method for the determination of chromium in dusts and mists. Issa et al. 3 have studied the polarographic behaviours of chromate and dichromate ions within the limits 0·2-2·0 mM. Polarographic behaviours of chromium( VI) have been studied by several workers using different electrolytes4-8. The present work deals with the study of the polarographic reductions of chromate, molybdate, and tungstate ions using potassium chloride-phosphoric acid supporting electrolyte. Whereas the Mo(VI) and W(VI) ions are reduced successively to the penta- and tri-valent states, Cr(VI) is not reduced reversibly. Use of gelatin as maxima suppressor in the case of Cr04 -2 results in the suppression of its polarographic wave in O·IM sodium hydroxide