COMPRESSIBILITY OF METALS. 181 



Metals Crystallizing in the Cubic System. 



Tungsten. It is well known that, because of its methods of prepa- 

 ration, this metal may show considerable differences of density, 

 depending on the amount of mechanical working to which it has been 

 subjected, the finer wires having the greater density. It therefore 

 seemed to me desirable to measure the compressibility of two samples 

 differing considerably in the amount of working to which they had 

 been subjected. Through the kindness of the General Electric Com- 

 pany I obtained a number of samples of pure tungsten, and selected 

 two from these best adapted to the measurements. The first was 0.48 

 cm. in diameter; it had been swaged to these dimensions from the 

 original sintered bar, but had not been drawn through dies. It was 

 mounted as a compression specimen in the lever apparatus, with a 

 length of 8.68 cm. The density at room temperature was found by 

 weighing in air and water to be 19.137. The second specimen was of 

 drawn wire 0.051 cm. in diameter, and was mounted as a tension 

 specimen in the lever apparatus. The length was about 10 cm. The 

 density of this small sample could not be determined with sufficient 

 accuracy by weighing, but tables compiled by the General Electric 

 Company show that the density to be expected on the average for wire 

 of this diameter is 19.48. The difference between the densities of the 

 two samples is thus considerable; it is questionable how much is due 

 to closing of the pores and how much is due to the breaking up of the 

 crystalline structure by working, replacing the crystalline material 

 by amorphous. 



Regular readings were made on these two samples at 30° and 75°. 

 The readings were very satisfactory, considering the small compressi- 

 bility of this metal. Discarding the 8 most irregular points, the aver- 

 age numerical departure from a smooth curve of the remaining 48 

 points was 0.28% of the effect produced by the maximum pressure. 

 The accuracy of the readings with the two different samples was essen- 

 tially the same. The departure of the points from linearity, as com- 

 pared with iron, was well marked, and at the mean pressure was about 

 2.5 times as great as the average error of a single observation. The 

 deviations from linearity determined for each sample independently 

 from the series of readings at the two temperatures differed by not 

 more than 10% from the mean. The direction of this departure from 

 linearity was such as to make the change of compressibility of tungsten 

 with pressure less than that of iron, as would be expected from its 



