A technique for the measurement of diffusion coefficients in molten salts

A diffusion method is described in which two columns of molten salt to be interdiffused, initially separated by a gas bubble at reduced pressure, are joined by breaking a capillary and allowing external pressure to eliminate the bubble. After a period of diffusion, the salt distribution is preserved by causing the glass diffusion tube to break at the point of initial junction while the tube is still in position in the high temperature zone of the furnace. The method has been tested with a 1: 1 CdCl₂-KCl mixture. The self-diffusion coefficient of cadmium is found to be 1.40 cm. ²sec^-1 at 470° C, with a probable error of 2.5%. The method is applicable up to temperatures of the order of 1000° C.