A differential freezing point apparatus was utilized to determine the freezing point depressions of aqueous solutions of mono-, di- and trimethylamine hydrochlorides over a concentration range 0.0025 to 1.0 molal. The data are presented in terms of j-values at rounded concentration values. From these j-values, provisional values for the activity coefficients were calculated. Conductivity data for the methylamine hydrochlorides are presented. Two new alkaloids, saururine (C₁₀H₁₉N) and sauroxine (C₁₁H₂₆ON₂), have been isolated from Lycopodium saururus.