362 



EDNA D. SAYCE. 



The values of K25 obtained for crystalline selenium are 

 given in Table IV. 



Table IV. — Thermal Conductivity of Crystalline Selenium. 



Disc. 



Temp, 

 of 

 prepara- 

 tion. 



1. 



11. 



in. 



Age. 



K 25 



Age. 



K 25 



Age. 

 Year. 



K 25 



A 



160°C. 



Days. 

 11. 



0-00110 



Days. 



164 



0-00081 



0-00070 



B 



170 



16 



0-00157 



134 



0-00130 





000097 



(J 



180 



38 



0-00149 



95 



0-0099 





000097 



D 



192 



28 



0-00161 



148 



0-00111 





0-00120 



K 



200 



9 



000168 



156 



0-00120 





0-00110 



F 



214 



42 



0-00183 









0-00139 



Two general tendencies are apparent, firstly the decrease 

 in conductivity with the age of the disc, and secondly the 

 increase in conductivity which accompanies an increase in 

 the temperature of preparation. Departures from these 

 general principles will be noted in the case of discs B and 

 D (III). In preparation the former was heated for a longer 

 period than any of the other discs, and, by accident, the 

 bath was kept at a temperature of 57° O. for twenty-four 

 hours shortly before the readings for D (III) were taken. 

 This appears to have produced some permanent change in 

 the substance, for when measured six weeks later the 

 value of K25 for disc D was found to be 0*00119. 



Table V has been included in order to illustrate what has 

 previously been said with respect to the accuracy of the 

 work. This disc, though apparently treated in exactly the 

 same manner as the others, fails to give a linear relation 

 between conductivity and temperature. The increase in 

 the conductivity at room temperature is also very much 

 larger than in the normal case shown in Table II. 



The existence of such irregularities renders the numerical 

 values of the conductivity unreliable, but there appears to 

 be definite evidence that the thermal conductivity is 



