Study On The Electrochemical Behavior Of The Polarographyic Waves Of Cobalt, Molybdenum And Rare Earth Elements Lanthanum, Cerium, Praseodymium And Its Application

Adsorptive complex wave has developed rapidly for twenty years. We attach importance to it highly, because it enhances the sensitivity and enlarges the determining range of the convenient oscillopolarograph. We study the characteristic of adsorptive complex wave with direct current polarography , voltammetry , and so on. These not only show the mechanism of adsorptive complex wave more, but also direct the work in practice .On the basis of some certain literatures , I studied three systems of complex polarographic wave respectly:1. The system of C0( II)- alpha -furfualdioxime-NH3·H2O -NH4ClIn a supporting electrolyte containing NH3 · H2O-NH4C1(PH=10.8), a sensitive adsorptive complex wave of C0( II)- alpha -furfualdioxime was observed at about -1.18V by oscillopolarography(vs. SCE), and the peak height is proportional to the concentration of Co(II) over the range from 2 × 10-10g/rnL to 4 × 10-8g/mL. The method has been applied to the determination of the trace Co( II) in the aque and troche of vitamin B12 with satisfactory results. The properties of the polarographic wave was discussed with direct current polarography and voltammetry in this paper. It is a adsorptive complex wave with catalysis. The complex ratio is 2:1. The electrode reaction is reversible. The number of electrons transfer (n) is 2 and the transfer coefficient( a ) is 0.60. The rate constant of surface electrode reaction(ks) is 1.83/s. The adsorption of the complex obeys Frumkin adsorption isotherm. The adsorption cofficient (P )is 3. 79 X107 and the attractive factor(gamma)is 1.58.2. The system of Ce(III)[Pr(III),La(III)]- alizarin complexone- hexamethylene-tetramineIn 0.1mol/L hexamethylene-tetramine buffer containing(PH=4.5), cerium(III)-alizarin complexone complex shows a sensitive polarographic absorptive wave with its peak potential at -0.48V (vs.SCE), and there is a linear relationship between peak height and concentions of cerium(III) in the range of 1.0 × 10 -1.5×10 5mol/L. The complex ratio is 1:1. Lanthanum(III) and praseodymium(III) are similar to cerium(III). It can be used for the determination of Ce(III) in solution and the total concent of lanthanum(III), cerium(III) and praseodymium(III) in solution. And the results obtaind are satisfactory. 3. The system of Mo(VI)-cupferron-HAc-NaAcThere is a sensitive polarographic wave of Mo(VI) and cupferron in the HAc-NaAc buffer containing. Its peak potential is about -0.38V(vs.SCE). The optium conditions are 0.1mol/L HAc-NaAc at PH 3.2. The peak height is linear with the concentration of Mo(VI) in the range of 5 × 10-10g/mL to 3 × 10-8g/mL. This method is applied to determination of trace amounts of molybdenum of man hair. This wave is reversible and adsorptive. The molar ratio of Mo(VI) to cupferron in the complex is found to be 1:1.