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Project Progress

In the past year, Co-Investigator Robert Hodyss performed measurements of the solubility of rare gases in liquid ethane using the quadrupole mass spectrometer system that was developed in the first year of this work. Briefly, a quadrupole mass spectrometer (SRS 200) in a small vacuum chamber is used to sample liquids through a capillary into the mass spectrometer. Liquid drawn into the capillary will rapidly vaporize and be analyzed with the mass spectrometer. Saturated solutions of rare gas are made by first condensing ethane in a LN2 cooled, temperature controlled dewar, then bubbling the rare gas of interest through the solution until saturation is reached. A mass spectrum of a representative mixture of argon in liquid ethane is shown in Figure 1. By monitoring the selected peaks in the mass spectrum, we can observe the solution as it reaches saturation (Figure 2). Final concentrations are calculated based on the sensitivity of the mass spectrometer to the particular species. The solubility of argon in liquid ethane at 94 K was determined to be 4.6 × 10^-2 mole fraction, consistent with theoretical values.

After the solubilities of the Kr, Xe, and N₂ are determined, he will begin to use this system to determine the solubilities of small organic species. He will begin with the small aromatics and nitriles such as benzene and acetonitrile, which are expected to have relatively large solubilities in liquid methane/ethane. This method of sampling and analysis of liquid hydrocarbon solutions also could be easily adapted for in situ Titan missions with the goal of sampling Titan’s lakes.