POLAROGRAPHY OF GALLIUM IN ACID MEDIA - SEPARATION OF EFFECTS DUE TO ANION INTERACTION AND IONIC STRENGTH

Investigation of the SCN--catalyzed ac and dc polarography of gallium in strong acid media has been extended to ascertain the separate effects on the Ga(lll) reduction process of (a) ionic strength; (b) thiocyanate concentration; (c) added halide; (d) pH; and (e) changing Ga(lII) concentration. Results (a) through (c) intimated that reversible reduction may occur via anionic gallium [probably Ga(SCN)4−] rather than cationic, and results obtained in (d) were not inconsistent with this notion. A subsequent anion exchange study using the CI04− form of Dowex 1-X8 indeed verified that anionic Ga(lll) could be present in the SCN-containing 6.0M NaCIO4 test solutions. Variation of corrected dc diffusion current vs. Ga concentration was linear over the range 0.01 mM to 5.0 mM Ga(lll) which enabled direct polarographic measurement of Ga(lll) down to the 1.0-ppm level. The Ga(lll) diffusion coefficient, DGa was calculated to be 3.06 ✕ 10−6 cm2-sec−1 (30° C) referred to 6.0M NaCIPO4. © 1968, American Chemical Society. All rights reserved.