Photoacoustic and photopyroelectric investigations of thermal parameters in water mixed with organic liquids

Abstract
Two photothermal (PT) techniques have been applied for investigation of some water-based binary liquid mixtures. Photopyroelectric (PPE) method in back configuration, using the sample thickness scan of the phase of the PPE signal, has been applied for thermal diffusivity measurements. Thermal effusivity investigation has been performed using photoacoustic (PA) open cell with microphone recording. A linear dependence of thermal effusivity on mass concentration of a liquid admixture was observed in the case of non-interacting liquids. For the case of interacting liquids the dependence of relative excess values of both thermal diffusivity and effusivity on mass fraction revealed distinct minima. The results of the PT experiments have been analysed with a simple theoretical model. Adiabatic compressibility variation versus mole fraction of the liquid admixture was also determined, by means of ultrasonic method, for comparison purposes. The obtained PT results support the conclusions drawn from the investigation of the elastic parameter.