The density, electrical conductivity, freezing point, and viscosity of mixtures of trifluoromethanesulfonic acid and water

Density, viscosity, specific conductivity, and freezing point measurements over the whole composition range of water–trifluoromethanesulfonic acid mixtures are reported. A maximum in viscosity and minimum in specific conductivity are observed at the composition corresponding to the monohydrate, H3O+SO3CF3−, and a maximum deviation from the ideal density is found at the composition corresponding to H5O2+SO3CF3−. The freezing point curve gives evidence for four hydrates with 1:1, 2:1, 4:1, and 6:1 water/trifluoromethanesulfonic acid mole ratios. An incongruent melting hydrate, probably 2:1 acid to water mole ratio is also indicated.