182 BRIDGMAN. 



smaller absolute compressibility. The final results are expressed 

 in the following formulas, p being in kg/ cm 2 : 



AV 

 Swaged rod, At 30° — = - 1(H (2.93 - 1.5 X KHp) p 



I 



o 



AV 

 At 75° — = - 10- 7 (2.95 - 1.5 X I0~ 5 p) p 



1 



o 



AV 

 Drawn wire, At 30° — = - 10~ 7 (3.15 - 1.6 X lO^p) p 



I 



o 



AV 

 At 75° — = - 10- 7 (3.16 - 1.5 X l(Hp) p. 



I 







It is perhaps not to be expected that the drawn wire with the greater 

 density should also have the greater compressibility. This is possibly 

 due in part to the greater amount of the amorphous metal that the 

 drawn wire doubtless contains, since it is usually true that an amor- 

 phous phase is more compressible than the corresponding crystalline 

 one. 



The only previous determination of the compressibility of tungsten 

 seems to be by Richards. 1 His material was in the form of fused 

 buttons, also obtained from the General Electric Company, and had a 

 density at room temperature of 19.231. He finds for the initial com- 

 pressibility 2.7 X 10" 7 . The value is given to only two significant 

 figures, and I gather from personal conversation with Professor 

 Richards that he regards as possible an error of several units in the 

 last place. 



Platinum. Runs were made on two specimens, of quite different 

 dimensions, in two different pieces of apparatus. I am indebted to 

 the kindness of Baker and Company for the loan of the two specimens. 

 The material was stated by them to be chemically pure platinum. 

 The first specimen was 2.5 cm. long and 0.S cm. in diameter. It was 

 used as a compression specimen in the lever apparatus for short speci- 

 mens. It was cut from a drawn rod of platinum, and before the meas- 

 urements was annealed for several hours in an electric furnace at a 

 temperature of 800°. The second specimen was of drawn wire, an- 

 nealed, 0.065 cm. in diameter and about 10 cm. long, and was mounted 

 as a tension specimen in the lever apparatus for long specimens. 



The regular set of readings at two temperatures was made on 

 each specimen. The readings with the shorter specimen we're not 



