The theory of irreversible polarographic waves was applied to the reduction of a series of aliphatic amino oxides such as trimethyl-, dimethylbenzyl-, dibenzylmethyl- and tribenzyl-amine oxides, and of a series of substituted N, N-dimethylaniline oxides such as dimethyl-p-toluidine-, dimethyl-p-chloraniline-, dimethyl-m-chloraniline-, dimethyl-o-toluidine- and dimethyl-o-chloraniline oxides. In every case, a well-defined straight line was obtained in the relation between logk and E (vs. SHE). In aliphatic amine oxides the plot log ^<k^0_f> vs. E_<1/2> for the first three yielded a straight line, while the one for the last deviated somewhat from the line. On the other hand, the plot for N, N-dimethylaniline oxides substituted in para or meta position fell into a straight line a little different in its slope from that for those substituted in ortho position.
In spite of the above fact, those deviations are rather small, and the relation between log ^<k^0_f> values for the oxides and pK_a values for the parent amines in both groups agrees at least qualitatively with that between E_<1/2> and pK_a shown formerly. Therefore we may say that the above E_<1/2> values used in the comparison between the molecular structure and the electrode process roughly show the characters of the structure of each amine oxide.