Interaction of formic and acetic acid with ice surfaces between 187 and 227 K. Investigation of single species- and competitive adsorption.

摘要: The physical adsorption of formic (HC(O)OH) and acetic (CH3C(O)OH) acid on ice was measured as a function concentration temperature. At low concentrations, the gas–ice interaction could be analysed by applying Langmuir isotherms to determine temperature dependent partition constants, KLang. Using independent saturation coverages (Nmax) (2.2 ± 0.5) × 1014 molecule cm−2 (2.4 0.6) for HC(O)OH CH3C(O)OH, respectively, we derive KLang(HC(O)OH) = 1.54 10−24 exp (6150/T) KLang(CH3C(O)OH) 6.55 10−25 (6610/T) cm3 molecule−1. Via van’t Hoff analysis, enthalpies were obtained CH3C(O)OH. Experiments in which both acids or methanol interacted with surface simultaneously adequately described competitive kinetics. results are compared previous measurements used calculate equilibrium partitioning these trace gases surfaces under conditions relevant atmosphere.