EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 117 



their experience was that although the chemical analysis might show 

 very little impurity, there was nevertheless present in all antimony 

 from American sources some slight impurity which was sufficient to 

 displace the melting point by several degrees. Presumably my anti- 

 mony suffered from the same impurity. 



Two of my samples were made from cast antimony and two from 

 extruded metal. The metal was cast by pouring it into a groove in a 

 massive iron block to a thickness of a trifle over | inch. The chilling 

 was hence very rapid, and the crystalline structure very fine. From 



1500 







10 



12 3 4 5 6 7 8 



Pressure, Kg. / Cm.' X 10 



Bismuth 



Figure 10. Bismuth. Thermal conductivity in arbitrary units against 

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

 specimen. 



this casting two pieces were machined for the longitudinal flow 

 method. The metal is so brittle that it was not possible to cut it with 

 the tool in the ordinary way, but the machining had to be by grinding. 

 Even then extreme caution was necessary, and there were many fail- 

 ures before success was attained. The wire for the other two speci- 

 mens was extruded at a red heat through a high speed steel die of the 

 required dimensions. Some little practice was needed before the 

 proper manipulation was found. It is possible to extrude antimony 

 at a considerably lower than a red heat, but with a wire as large as | 



