GROWTH OF SALT AND ACID AEROSOL-PARTICLES IN HUMID AIR

Aerosols of industrial significance like ammonium chloride, hydrochlor ic acid and sulphuric acid aerosols have been generated with particle number concentrations between 10(6) and 10(8) cm(-3) and particle size s between 0.1 and 0.5 mu m (NH4Cl), 0.8-1.5 mu m (HCl) and 0.2-0.5 mu m (H2SO4). The influence of the generating conditions on the size and the concentration of the aerosol particles have been investigated. Aft er the generation, the particles were exposed to atmospheres of differ ent relative humidity. If a certain level of relative humidity is exce eded, the solid salt particles dissolute and become droplets. The part icle diameter of the salt and acid droplets increases if the relative humidity is raised. The particle diameters and concentrations were mea sured to show the dependence on the generating conditions and the rela tive humidity by a laseroptical extinction technique. The results of t he measurements were compared with growth models. There was a very goo d agreement between the experimental data and the growth models for sa lt and acid aerosols. It is therefore possible to evaluate the limit o f the growth by pure water vapour saturation, which is especially usef ul for the design of particle separators.