Abstract
By condensation method, aerosols of lead iodide were prepared, using carbon monoxide, nitrogen, or argon as carrier gas, the vapor of lead iodide being decomposed to yield iodine in oxygen-containing atmosphere; their weight concentrations were determined by a procedure like that in preceeding reports making use of chemical analysis, while their particle sizes were found through ultramicroscopy, in which the settling velocities of particles were measured.
The main findings are the following: (1) That both the weight concentration and the particle size go through a maximum with the rate of flow of the carrier gas. (2) That in carbon dioxide form aerosols of higher concentration, and in nitrogen and argon those of lower one; in carbon dioxide form aerosols of smaller size, and in nitrogen and argon those of larger one. (3) That the heat of vaporization of the melt of lead iodide is nearly 23kcal/mole, without distinction of carrier gas, in the range of temperature 360°-487°C. (4) That the circumstances under which highly monodisperse aerosols form are around 420°C-2l/min for carbon dioxide and 400°C-3l/min for nitrogen, the number concentrations being both of the order of magnitude of 107 particles/cc.
