Abstract
Various mechanisms and associated rate expressions for the reversible evaporation of volatile ammonium salts are presented, and experimental evidence for them discussed. The literature concerned with the existence of stable NH sub(4) super(+) salt monomers in the gas phase is highlighted. Four kinetic mechanisms are presented: monomer formation; adsorption of one precursor species on the particle surface; biomolecular surface reaction; and transport-limited particle growth. No mechanism emerges as the rate-limiting process for all experimental studies. Rate constant ratios for the first two mechanisms are calculated from the literature and shown to differ greatly from the thermodynamic equilibrium constant.