This article reports a calibration procedure for the commercial Anton Paar DMA 512 densimeter usable at pressures up to 40 MPa. The method is based on water as a reference substance and requires knowledge of the characteristics of the cell as functions of temperature when subjected to a vacuum lower than 100 Pa. Comparis on with data from the literature indicates a relative accuracy of 0.1% where the classical calibration method (i.e. assuming no dependence of the densimeter performance upon pressure) led to a relative accuracy of 0.8% for the same substances.

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The volumetric behavior of carbon dioxide (1) + decane (2) mixtures has been investigated under the high pressures 20, 30, and 40 MPa in the temperature range [308.15 K to 368.15 K]. Densities have been measured for pure decane and for x 1 ) 0.15, 0.30, 0.51, 0.66, 0.78, and 0.84. Density variations show a peculiar behavior: a crossover phenomenon with the composition at a given pressure and temperature is observed. The measured fluid densities have been compared with values predicted by equations of state with various mixing rules. This comparative study has revealed models well adapted to these density estimations.

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