In this paper we discuss the use of an alternative photothermal technique for measurements of thermal properties of liquids. The proposed technique is based upon the concept of thermal wave interferometry. The liquid sample is confined between two thin pyroelectric detectors. One of these detectors acts as a modulated absorber of light while the other is used for sensing the temperature fluctuations transmitted through the liquid layer. The good agreement between the values of the thermal properties we got with the present technique and those reported in the literature demonstrates the capability of the technique for full characterization of the thermal properties of liquids.

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In this paper, we describe a new, simple and fast photothermal method for characterizing the quality of natural gas used as automobile fuel. The method consists essentially in measuring the thermal properties of a sequence of natural gas diluted in nitrogen with a photothermal gas analyser time especially designed for this purpose. It is shown that the proposed method is capable of measuring the thermal properties with an accuracy of 3%. It is also shown that the proposed method is capable of detecting traces of H2S greater than 7.8 mg m−3 in the natural gas. This good accuracy, together with its fast response and portability, suggests it as a simple routine, local, checking device for natural gas quality assurance at retailers' stations.

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