EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 



Ill 



two different sources. I am indebted to the International Nickel Co. 

 for a piece of | inch round rod of high commercial purity (99%). 

 From this two samples were made for the radial flow method, large 

 cylinders without the sheath. The thermo-couples and heating ele- 

 ment were placed in fine copper tubes sweated into place. The re- 

 sults obtained with these samples were very irregular, and it was 

 evident that the thermal contact between the copper and the nickel 

 was not sufficiently good. These measurements did little more than 

 establish a strong probability that the effect was negative. After 

 the radial flow measurements had been made, two small pieces were 



p 2700 

 o 



Z) 

 Q 



Z 



o 

 o 



< 



cc 



UJ 



I 



2600 



2500 



4 3 6 7 8 9 



Pressure. Kg./Cm.'X 10' 

 Silver 



FiGiiRE 8. Silver. Thermal conductivity on an arbitrary scale against 

 pressure in thousands of kg/cm^. Results obtained with a longitudinal flow 

 specimen. The points lie on several lines of the same slope; the reason for 

 this is explained in the text. 



cut from one of the cylinders for longitudinal flow specimens, and a 

 few readings were made with them. This was before the explanation 

 of the scattering of the points by this method had been found. The 

 results were very scattering, and repetition would have been necessary 

 to make sure of even the sign of the effect. 



After completing the measurements on commercial nickel I was 

 fortunate enough to obtain through the kindness of Mr. I. B. Smith 

 of the Research Laboratory of the Leeds and Northrup Co. several 

 samples of exceedingly pure nickel. I have no analysis of the nickel, 

 but its high purity is vouched for by the unusually high value of the 

 temperature coefficient of electrical resistance, which between 0° and 



