356 EDNA D. SAYCE. 



SOME DETERMINATIONS OF THE HEAT CONDUC- 

 TIVITY OP SELENIUM. 



Edna D. Sayce, b.Sc, 



Demonstrator in Physics at the University of Sydney. 



(Communicated by Professor 0. U. Vonwiller.) 



[Bead before the Royal Society of N.S. Wales, October 3, 1917. 



It is well known that the electrical conductivity of 

 selenium can be varied over a wide range by suitable alter- 

 ations in the method of preparation, or in the temperature 

 and degree of illumination at the time of testing. If these 

 changes are due to variations in the number of free elec- 

 trons present in the substance, we should expect to find 

 corresponding changes in the thermal conductivity under 

 similar conditions. 



Some investigations on this point have been made by 

 Bellati and Lussana, 1 and by L. P. Sieg. 2 In both cases 

 attention was concentrated mainly on the effect of illumin- 

 ation, and only relative measurements were made. In the 

 work which is to be described here, the influence of the 

 method of preparation, the age of the specimen, and the 

 temperature of testing have been investigated, all measure- 

 ments being made with the selenium in darkness. 



The results obtained are such as might be expected from 

 a consideration of the values of the electrical conductivity 

 obtained by observers working with selenium cells. It is 

 found that the thermal conductivity varies over a wide 

 range, being affected by those conditions which influence 

 the electrical conductivity. In all the cases which have 

 been examined, both thermal and electrical conductivities 



1 Gazz. Chim. Ital., 17, 391. * Phys. Rev., 6, p. 213, 1915. 



