Density measurement by oscillating tube. Effects of viscosity, temperature, calibration and signal processing

Abstract

A frequency counter and precision thermostat, designed to operate in conjunction with an Anton Paar DMA 602 oscillating tube densitometer, have been built. The apparatus is capable of rapid density determinations. It can detect density changes of less than 5 × 10^–7 g cm^–3 and allows densities of low viscosity materials to be determined to an accuracy of ±5 × 10^–6 g cm^–3 if a suitable calibration standard is available. The effect of the viscosity of the samples on the density readings has been found to be significant when the viscosity is greater than ca. 1 mPa s. A correction procedure has been devised for such liquids. Excess volumes of the cyclohexane–toluene system have been measued at 298.15 K and agree with literature data, thus confirming the suitability of the apparatus for the determination of density differences.