The heterogeneous chemistry, on aqueous surfaces, of a series of acid halides, COF2, CF3COF, and CF3-COCl, was studied. The technique used consists of a low-pressure flow tube reactor in which a stream of monodisperse droplets interacts with the gaseous acid halide. The experiments, which were performed as a function of the initial pH of the droplets, temperature, and gas/liquid interaction time, yield low uptake coefficients in the range 5 x 10(-4) to 5 x 10(-3) and allow estimation of the product H root k, where H is the Henry’s law constant and k is the hydrolysis rate constant. The values reported here are 60, 60, and 350 M.atm(-1) s(-1/2) for CF3COCl, CF3COF, and COF2, respectively, at 273 K. Separate values of H and k are also reported. The results show slightly different behavior between the chloride and the fluorides as a function of temperature. This study shows Henry’s law and hydrolysis rate constants large enough that heterogeneous reactions on aqueous surfaces will limit the residence time of these species in the atmosphere.