It was found that the polarographic behavior of cadmium ion in 0.5M H2SO4 solution containing 0.01% gelatin is unsatisfactory because the diffusion current does not attain a perfect constant value but continues to increase gradually up to the potential of hydrogen discharge. The polarographic behavior of cadmium ion in 0.5M H2SO4 solution without gelatin is studied in this work. It is found that the polarographic behavior of cadmium ion in 0.5M H2SO4 is excellent. The current-potential curves of cadmium ion in 0.5M H2SO4 solutions in which the concentration of cadmium varies from 0.050mM to 20.0mM are determined and the well-defined polarographic waves with limiting diffusion current and easily determined half-wave potential are obtained. The limiting diffusion current (wave height) of cadmium ion in 0.5M H2SO4 is proportional to its concentration. The half-wave potential of cadmium ion only varies slightly in the range of -1.011--1.047V (vs. 0.5M mercurous sulfate electrode) as the concentration of cadmium ion varies from 0.05mM to 20.0mM. Therefore, cadmium can be determined quantitatively and qualitatively by polarographic method in H2SO4 solution. The following polarographic data of cadmium ion in 0.5M H2SO4 solution are obtained: the diffusion current constant id/cm2/3t1/6= 3.97\m\A/mM.mg2/3.S-1/2 the half-wave potential E1/2=-1.011V (vs. 0.5M mercurous sulfate electrode) or K1/2=-0.559V (vs. SCE), and the number of electron transferred in the electrode reaction n=2.

Key words: SULFURIC ACID, POLAROGRAPHIC ANALYSIS, CADMIUM ION