The effect of apparatus dimensions on the accuracy of vapor pressure measurements by Knudsen's effusion method is discussed for the usual type of experimental arrangement. It is shown that the total surface area of a condensed solid phase is not fundamentally related to the pressure of the effusing vapor. Equations are derived which may be used to check the pressure of the effusing vapor for saturation. Two cases in the literature are discussed.

No abstract

A process for the preparation of high‐purity thorium powder by calcium reduction of thorium oxide has been developed, Calcined thorium oxide is reduced in an inert atmosphere at 950°C with high‐purity calcium metal in the presence of calcium chloride. The reduction vessel is fabricated of type 446 stainless steel to avoid pick up of iron and nickel impurities and permit break out of the reduction cake. The thorium powder so produced has essentially the same purity as the thorium oxide starting material. Important factors controlling yield and quality of the thorium powder are discussed.

No abstract

The vapor pressure of zinc has been measured using Knudsen's effusion method. The temperature-vapor pressure relation was found to be log10pmm=(−6688/T)+8.888 in the range 300°—360°C. These results are about 20 percent higher than those previously reported. It is suggested that this difference may be attributed principally to the omission of a probability factor by earlier workers.