HCL/H2O SOLID-PHASE VAPOR-PRESSURES AND HCL SOLUBILITY IN ICE

A study of the HCl/H2O binary system at low temperatures is presented, and applications to the polar stratosphere are discussed. A phase diagram constructed for low HCl partial pressures includes the tri- and hexahydrates as well as solid solutions of HCl in ice. Results of two experiments strongly suggest that the solubility of HCl in ice is low, less than 0.01 mol % for stratospheric conditions. Previous measurements have shown HCl to be orders of magnitude more soluble in bulk ice. The nitric acid trihydrate crystal, which is formed above ice condensation temperatures in the polar stratosphere, shows a much greater ability to absorb HCl than does pure ice for HCl pressures characteristic of the stratosphere. © 1990 American Chemical Society.