ASTM D2780 Test Method for Solubility of Fixed Gases in Liquids
9. Procedure B
9.1 Procedure B covers the determination of the solubility of fixed gases in liquids at elevated pressure.
9.2 Place in the elevated pressure saturator (Fig. 2) 300 to 500 mL of the sample liquid that has been saturated with the test gas (Warning - See 6.2) in the ambient pressure saturator (Fig. 1) in the manner described in 8.3 to free it from dissolved air. The transfer line, described in 5.2.4, is used. If flowing the liquid by gravity is too slow, evacuate the elevated pressure saturator partially prior to starting the transfer, and close valve A. Bring the saturator to temperature equilibrium at the temperature desired for the determination.
NOTE 7 - Should solubility measurements at subambient temperatures be desired, the saturation cell can be modified by the addition of a jacket through which a suitably thermostated cooling fluid may be circulated.
9.3 Charge the saturation cell with the test gas at the desired pressure through valves A' and A'' with valve A closed. Then close valves A' and A'' and shake the cell for 5 min. Recharge the cell with gas to restore pressure after the initial saturation step. Shake again. Repeat the process of charging and shaking until constancy of pressure indicates that the liquid has been completely saturated. Allow the sample to stand at constant pressure and temperature for at least 30 min to permit the release of entrained bubbles. (Warning - At elevated pressures the reactivity of samples with gases is greatly enhanced. Some samples in contact with oxygen or air may form mixtures capable of autoignition at room temperature or below. Do not attempt the use of oxygen at elevated pressures under any circumstances. Studies with air under moderate pressure may be attempted provided that the autoignition temperature (reaction threshold temperature) of the sample in the presence of air at the test pressure is not exceeded. See Test Method D2883.)
9.4 Attach the saturator containing the saturated liquid to the assembled gas extraction system. Evacuate the gas extraction system by the procedure described in 8.4. Then extract the gas from a measured portion of the sample by the procedure described in 8.5.
