13<) 



iiiul compared with the rate observed after melting took phur. The ratio wor- 

 ked out to be 10,0()(). 



The measurement of the rate of self-diffusion of lead ions in a solid lead salt 

 permitted the determination of the transference number of the ions of solid lead 

 lialogenides (paper 14). In his very beautiful investigation Tubandt found that 

 while both ions have a large part in the conduction of electricity through the 

 solid lead iodide, alone the movement of chloride ions is responsible for the 

 jnissage of an electric current through solid lead chloride. The ionic mobility of 

 Ph-' in PbCl, calculated from its self-diffusion rate determined by making use 



ol the very S(!nsiti\e lecoil method indicates that for about - pait of the 



(>iectrical curient passing through solid lead chloride the movement of lead ions 

 is responsible. 



References 



I. Groh and G. Hevesv (1920) Ann. Phys. 63, 85. 

 G. Hevesy and W. Seith (1929) Z. Phys. 57, 869. 

 G. Tubandt, H. Reinhold and \V. Jost (1928) Z. Anorg. Chem. 177, 254. 



