Onsager heat of transport of carbon dioxide at the surface of aqueous ammonia: The remarkable effect of carbamate formation

The Onsager heat of transport Q∗ has been measured for CO ₂ at the surface of aqueous ammonia. The heat of transport incorporates the enthalpy of reaction of gaseous CO ₂ with ammonia, adsorbed on the liquid surface, to form adsorbed ammonium carbamate, with the result that -Q∗ has the unusually large value of 180 kJ mol ^-1. Measurement of Q∗ for transfer of a reactive species through a surfactant monolayer is proposed as a new method of studying reactions at liquid and quasi-liquid surfaces.