48 BRIDGMAN. 



The tension coefficient of resistance given by the two runs on the 

 better specimen was —8.2 and^— 8.4 X 10~® respectively for a tension 

 of 1 kg/cm^. The other specimen, which was very much more un- 

 certain in its indications, gave a coefficient of —10.5 X 10~^. Take as 

 the best mean —8.3 X lO"". 



Young's modulus was determined from the bending of two samples. 

 Measurements were also made on the sample of the imperfect resist- 

 ance measurements, but these were discarded because of the uncer- 

 tainty introduced by failure of geometrical regularity. The dimen- 

 sions were approximately the same as for lithium. The maximum 

 load was 0.0(36 gm. and within the limits of error the relation between 

 bending and load was linear. The first specimen gave for Young's 

 modulus 1.24 X lO^^, and the second 1.36 X lO^^ Abs. C.G.S. units. 

 Take as the best value 1.30 X 10^\ or 1.33 X 10^ when tension is 

 expressed in kg/cm-. The compressibility of strontium has never 

 been determined experimentally so far as I am aware. A probable 

 value for it may be found by interpolating in Richard's chart ^ giving 

 the compressibility as a periodic function of the atomic weight. The 

 value which I have assumed for the compressibility is 6.5 X 10~^^ 

 Abs. C.G.S. The value of Poisson's ratio computed with these values 

 for Young's modulus and compressibility is 0.359. An error of 1% in 

 the compressibility changes Poisson's ratio by 0.5%. 



The behavior of the resistance beyond the elastic limit was not 

 investigated, except to establish that there is a permanent increase 

 in resistance on exceeding the limit. The permanent change is there- 

 fore of the opposite sign from the elastic change. 



Antimony. So-called chemically pure antimony from the J. T. 

 Baker chemical company was used. It was extruded into wire in the 

 way previously described. ^° This wire is not from the same source as 

 that whose pressure coefficient of resistance was previously measured, 

 which was from Eimer and Amend. The present material has also 

 been used in a determination of the effect of pressure on thermal 

 conductivity, and the data will be given elsewhere. 



Great difficulty was experienced with antimony because of its 

 extreme brittleness, and a special procedure was adopted. At the 

 suggestion of Mr. Slater, who made the measurements, the vertical 

 position of the other metals was replaced by a horizontal position for 

 antimony. The wire was placed in an oil bath, without a stirrer, 

 resting on a massive bar of copper. Tension was applied by a spring 



9 Reference 6, p. 1649. 

 10 P. W. Bridgman, Phys. Rev. 9, 138-141, 1917. 



