Formation of Lead Aerosols in Nitrogen and their Chemical Reactivity

Abstract

By a condensation method, nitrogen-borne lead aerosols were generated with the intention of inquiring into the conditions under which monodisperse aerosols might be formed. The experimental procedures are almost the same as those in the previous report.It was found that (1) the weight concentration and the particle size vary with the flow rate of nitrogen stream and the temperature of lead vapor; both of them reach a peak at a certain rate of flow under any of the temperatures examined (950° to 1150°C) making a contrast to the number concentration passing through a trough. (2) There is a linear relation between the logarithm of mean particle size and the reciprocal of vapor temperature for all the rates of flow tested (1.0 to 4.5l/min). (3) Aerosols of high monodispersity might be obtained by vaporizing metal at a temperature in the range of 1000° to 1150°C and by flowing nitrogen at a rate of 1.5l/min.Using the aerosols so obtained, a preliminary experiment of their reactivity toward iodine vapor was carried out, with the following results:(1) It seems that the coarser particles of lead react with iodine to produce lead iodide more readily than finer ones. (2) The reactivity is affected by the temperature of reaction; it was found to be nearly 2 and 16% per 15minutes at 30° and 50°C respectively, the apparent heat of activation being estimated as 21kcal/mol.