AZIDE-INDUCED REVERSIBLE VOLTAMMETRIC REDUCTION OF GALLIUM(III) FROM ROOM-TEMPERATURE, LOW IONIC-STRENGTH ACID-MEDIA

A dffferential pulse (DP) voltammetric study of aquogallium-(III) reduction from acidified azide media has revealed the previously unreported existence of a pH "window" extending from about pH 3 to 5 within which the cation undergoes reversible or near-reversible reduction to the amalgam independent of the need for high ionic strength or elevated temperature. DP peak heights (I(p)'s) increased from ca. pH 2.5 to 4.0, beyond which they dropped off fairly smoothly as a result of hydrous oxide formation. At constant pH 4.0, I(p)'s increased in S-shaped fashion with an increase In free azide. The DP peak potential (E(p)) varied linearly with (a) pH at constant free azide concentration and (b) free azide concentration at constant pH 4. At pH 4.0 and 0.58 M N3-, DP peak heights were found to increase linearly (r = 0.999) with an increase in Ga(III) concentration from 0.0 to 0.985 mM. Measurements within the pH band enable precise determination of Ga(III) under mild conditions, in marked contrast to the thiocyanate-based reaction whose success depends On either high ionic strength or elevated temperature.