C–H Infrared Absorption and Solubility of Ethylene, Propyne, 2-methyl-2-butene, and 2-methyl-1, 3-butadiene (Isoprene) in Liquid Argon Solutions

The solubility of ethylene (H2C=CH2), propyne (CH3–C≡C–H), 2-methyl-2-butene (CH3–CH=C(CH3)2), and isoprene or 2-methyl-1, 3-butadiene (H2C=C(CH3)–CH=CH2) in liquid argon has been measured using mid-infrared and near-infrared (NIR) absorption. Spectra were recorded in the C–H infrared (IR) region. Spectra were obtained at increasing solution composition until the magnitude of the integrated absorption band reached a maximum value, indicating a saturated solution. The approximate experimental solubilities are: (600 ± 100) ppm at 92 K for ethylene, (22 ± 9) ppm at 100 K for propyne, (9 ± 5) ppm at 100 K for 2-methyl-2-butene, and (12 ± 2) ppm at 86 K for isoprene. The experimental solubility values at the corresponding temperature were used with solubility parameters of two separate models: the perturbed-chain statistical associating fluid theory (PC-SAFT) and the regular solution theory. Solvent–solute interaction parameters k12 (PC-SAFT) and ι12 (RST) were obtained for each solute in the presence of argon...