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<br />8 <br /> <br />+ - + <br />iodide to form a new compound (Na As2I,) which reduoes the Ag and I <br />ooncentrations. The new compound effectively removes the ions because <br /> <br />the stable AsI.NaI complex readily dissolves in water or acetone and <br /> <br />does not dissociate into its component ions. Thus the equilibrium is <br /> <br />shifted toward more dissolution of As1 (St.-Amand, et al., 1971), <br /> <br />The earliest study of the chemical composition complexes of AgI- <br /> <br />alkali iodides was made by Mason and Hallett (1956). They analysed <br />electron diffraction patterns of vaporized AgI-II and AgI-NaI mixtures <br /> <br />and concluded that AgI alone was not beins produced when these aerosols <br /> <br />were generated and that mixed crystals of both substances, Ag1 and the <br /> <br />solubilizing salt, were formed. Several workers then concentrated their <br /> <br />eftorts on studying the AgI-II system. Because of the similarity of <br /> <br />Ag1-NaI and AgI-II in nucleating behavior (Rilling, et al., 1984) a <br /> <br />brief discussion of the chemistry of the AgI-II system tollows. <br />Electron diffraction studies by dePena and Caimi (1967) and <br />Burkardt, et al., (1968) demonstrated that simple mixtures ot AgI and II <br /> <br />were not tormed by combustion of acetone solutions containing these <br /> <br />materials. DePena and Ca1m1 (1967) concluded that a solid solution of <br /> <br />AgI and II in a 2:1 mole ratio was formed. Burkardt, et ale (1968) <br /> <br />lists the known AsI-alkali iodide-vater complexes and presents X-ray <br /> <br />diffraction results which support the existence of these complexes. <br /> <br />The complex formed by AsI and II is hygroscopic due to the presence <br /> <br />of II, in contrast to AgI alone, which is hydrophobic. AgI-II samples <br /> <br />collected from a field burner, similar to that used in this research, <br /> <br />begin to adsorb water vapor at 531 relative humidity (Tompkins, et a1., <br /> <br />1963). Similar aerosol particles were shown to form droplets at 9S~ <br /> <br />relative humidity (dePena and Caimi, 19(7). <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />