VAPOR-PRESSURES OF H2SO4 HNO3/HCL/HBR/H2O SOLUTIONS TO LOW STRATOSPHERIC TEMPERATURES/

Vapour pressures of H2O, HNO3, HCl and HBr over supercooled aqueous mi xtures with sulphuric acid have been calculated using an activity coef ficient model, for 185 K < T < 235 K, 0 < wt%(H2SO4)+wt%(HNO3) < 70, a nd assuming HCl and HBr to be minor constituents. Predicted vapour pre ssures agree well with most laboratory data, and give confidence in th e validity of the model. The results are parameterized as simple formu lae, which reproduce the model results to within 40% and cover the ent ire stratospherically relevant range of composition and temperature.