Abstract: For many engineering applications, it is important to obtain reliable data of the solubility of air in dimethyl silicone and hydraulic oils. Overcoming some drawbacks of previous methods for measuring gas-solubility, a new piston apparatus was established, in which the state equation of ideal gas was used to determine the amount of gas-dissolution. An expression of the Bunsen solubility of air in 500cSt silicone at temperatures of 293.2 and 353.2 K and in the gas-pressure range of 0-350 kPa was determined. The Bunsen solubilities of air in 20cSt silicone and Chinese 32# hydraulic oils at 298.2 K under various gas-pressures were also measured. Reliability and accuracy analyses indicated that the error range of the experimental data was about 6%. The Bunsen solubility and gas-pressure exhibited good linearity, while the relationship between the molar fraction and the pressure in the experimental range was nonlinear but could be well fitted by the Krichevsky-Ilinskaya equation. It was discovered that the Bunsen solubilities of air in silicone with quite different molecular mass were close to each other. The results suggested that the molar fraction based on the monomer mass was more appropriate than that based on the molecular mass for engineering extrapolation of the solubility data of small and non-polar solutes in polymer solvents. At last, for solvents containing much different or uncertain molecular mass, the commonplace in engineering applications, the Bunsen solubility was appropriate to give the dissolved gas concentration.

Key words: Gas-liquid phase equilibrium, Air, Bunsen coefficient, Dimethyl Silicone oil, Hydraulic oil