Uptake of nitrosyl chloride (NOCl) by aqueous solutions

The uptake kinetics of nitrosyl chloride (NOCl) by aqueous solutions has been measured as a function of temperature, using two different techniques, i.e., the wetted-wall at atmospheric and reduced pressure and the droplet train flow tubes, both techniques being combined with FTIR and HPLC detection. Uptake coefficients, which were shown to be slightly temperature dependent, range from 0.012 to 0.0058 for temperatures between 273 and 293 K. The production of HONO was observed from the hydrolysis of NOCl, and its yield in the gas phase is in agreement with the Henry's law constant of nitrous acid. The uptake of NOCl was also studied on solutions containing HCl, NaCl, and NaOH. Only the latter affected the uptake kinetics, probably through a nucleophilic reaction with OH-. The observed kinetics are shown to be consistent with a lower limit of 0.03 for the mass accommodation coefficient. These results suggest that heterogeneous removal of NOCl is very efficient, meaning that this compound is not expected to be a significant precursor of atomic Cl in the atmosphere. The Henry's law constant for NOCl was observed to be greater than 0.05 mol L-1 atm(-1).