Cw-laser thermal lens spectrometry in binary mixtures of water and organic solvents: composition dependence of the steady-state and time-resolved signals.

The thermal lens effect obtained in binary liquid systems composed of water and ethanol, propanol and acetonitrile has been investigated. The dependence of dn/dT upon the solvent volume fraction follows polynomials up to sixth order and cannot be precisely predicted using the additive rule. The sensitivity of the thermal lens method upon the addition of organic solvent in water varies as the temperature-dependent refractive index gradient to thermal conductivity ratio of the mixture provided that the signal is sampled correctly.