The surface tensions of aqueous solutions of formic acid, acetic acid, and propionic acid were measured over the entire concentration range at temperatures (20 to 50) °C. The experimental values were correlated with temperature and mole fraction. Maximum deviations were in both cases always less than 1%.

The surface tension of aqueous solutions of N-methyldiethanolamine and diethanolamine + N-methyldiethanolamine, monoethanolamine + N-methyldiethanolamine and 2-amino-2-methyl-1-propanol + N-methyldiethanolamine was measured at temperatures from 25 °C to 50 °C. For binary mixtures the concentration range was 0−50 mass % N-methyldiethanolamine, and for the tertiary mixtures the concentration range for each amine was 0−50 mass %. The experimental values were correlated with temperature and mole fraction. The maximum deviation in both cases was always less than 0.5%.