The ionization constants of eighteen secondary amines and eight alpha-substituted N-methylpyrrolidines have been measured in absolute methanol using the hydrogen electrode and a reference calomel half-cell containing 0.1 f sodium-chloride in methanol;The results found confirm the order of electro-negativity of organic radicals obtained from Goldschmidt and Bader's data on the dissociation of a series of alpha-aryl substituted beta-benzoyltetrazenes;The effect of substitution of organic radicals into the series RNHCH 2, RNHC5H5, and RC4H7NCH 3 on the ionization constants of the compounds gives an order of electronegativity of radicals similar to that obtained by Hixon and Johns and co-workers;The order of polarity of a series of (R)2-radicals obtained from the ionization constants of (R)2NH compounds was found to be similar to that for the R-series;Bronsted's opinion that the solvent influence is a constant and additive factor in the ionization of bases and acids in alcoholic solutions has been verified further for the case of bases in methanol;The pKb value of alpha-naphthyl-N-methylamine in water obtained by Hall and Spinkle has been corrected from ionization data in methanol.