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Evaporation of ammonium nitrate particles

1987; Elsevier BV; Volume: 21; Issue: 4 Linguagem: Inglês

10.1016/0004-6981(87)90092-8

1878-2442

C. B. Richardson, R. L. Hightower,

Coagulation and Flocculation Studies

Microscopic anhydrous ammonium nitrate particles are levitated in a vacuum in an electric quadrupole trap at 25°C. Size and mass changes of the evaporating particles are monitored continuously in situ using light scattering and gravity balancing. Both supersaturated liquid droplets at the zero-solvent limit and crystalline solids are studied. The measured vapor pressure of the liquid is p = (3.18 ± 0.45) × 10−6 torr. Fresh solid particles evaporate at a rate drdt = − 0.23 As−1 where r is an equivalent radius. Beyond 4 h the rate is a constant −0.06 Å s−1. These rates are consistent with that predicted from thermodynamics if the mass accommodation coefficient is α = 0.02 initially and 0.004 after 4 h. Aerosol sampling by several groups indicates the presence of solid ammonium nitrate particles in the atmosphere. Long lifetime and long-range transport of these particles are predicted regardless of ammonia and nitric acid vapor concentrations.