Sub-μL measurements of the thermal conductivity and heat capacity of liquids.

We present the analysis of the thermal conductivity, kappa, and heat capacity, C-p, of a wide variety of liquids, covering organic molecular solvents, ionic liquids and water-polymer mixtures. These data were obtained from approximate to 0.6 mu L samples, using an experimental development based on the 3 omega method, capable of the simultaneous measurement of K and C-p. In spite of the different type and strength of interactions, expected in a priori so different systems, the ratio of kappa to the sound velocity is approximately constant for all of them. This is the consequence of a similar atomic density for all these liquids, notwithstanding their different molecular structures. This was corroborated experimentally by the observation of a C-p/V approximate to 1.89 x 10(6) J K-1 m(-3) (approximate to 3R/2 per atom), for all liquids studied in this work. Finally, the very small volume of the sample required in this experimental method is an important advantage for the characterization of systems like nanofluids, in which having a large amount of the dispersed phase is sometimes extremely challenging.