Measurements of the partitioning of hydrogen peroxide in a stratiform cloud*

Simultaneous measurement of hydrogen peroxide in cloud droplets and in the air in which the droplets were suspended are presented. In addition, a description of the new technique used to make the measurements is presented. The ratio of the measured cloud-water concentration to the equilibrium cloud-water concentration predicted using Henry's law and the measured gas-phase hydrogen peroxide was 0.64. Analysis of both random and potential systematic errors indicate that, while this ratio was statistically different from unity, the difference was not considered to be substantial. Henry's law appeared to have been valid for hydrogen peroxide in the ambient cloud studied.