Abstract In this work the measurements of electrical conductivity, viscosity and density of NaI salt in formamide solutions in the composition range 0–21 mole % and in the temperature range 35–80°C are reported. The experimental data have been analyzed with equations utilized for transport in glass forming liquids. The glass-transition temperatures deduced from conductivity and viscosity data, reported in graph against the salt concentration, lie on the same straight line. Alternatively, the experimental conductivity and viscosity data have been analyzed with a three-parameter equation which describes the isothermal composition dependence of transport processes. At the four temperatures used the plots of 1gΛ and 1g against 1/( x 0− x), where x 0 is the glass transition concentration, were linearized by almost the same x 0 value. The values of the apparent and partial molar volumes of salt, deduced from density measurements,were found to be close to the value of the molecular volume of pure salt. This fact is interpreted in terms of equivalent energies of the ion-dipole and of the dipole-dipole interactions.