The solubility of HONO in various wt % sulfuric acid solutions was measured. HONO becomes increasingly more soluble in high acid wt % Solutions, probably resulting from the protonation of HONO to give H2ONO+, followed by dissociation and association to give NO+HSO4-(nitrosyl sulfuric acid). The reaction of HONO with HCl on 50, 60, 67, and 70 wt % sulfuric acid solutions was also studied. The measured uptake coefficients could not be explained simply by the occurrence of a bulk phase reaction, and a surface effect is found to contribute to the uptake. The reaction of HONO with HCl was measured on sulfuric acid particles, and a small reacto-diffusive length further supports a surface reaction. From extrapolating our measured uptake values to stratospheric conditions, the formation of ClNO from the heterogeneous reaction of HONO and HCl is concluded to be an insignificant process in the volcanically unperturbed stratosphere.