184 BRIDGMAX. 



21.31. The density of the larger of the two pieces measured above 

 was 21.34 at 20°. Evidently the mechanical condition of these two 

 specimens must have been nearly the same. 



Molybdenum. The treatment of molybdenum was like that of 

 tungsten. Through the kindness of the General Electric Company I 

 obtained a number of pieces in different stages of mechanical working; 

 the compressibility of two of these was measured. One specimen, 

 which had been swaged only but not drawn, was used as a compression 

 specimen in the lever apparatus; its diameter was 0.48 cm. and length 

 about 10 cm. This specimen was in two pieces, held butting end to 

 end in a steel sleeve. It is often possible in this way to fit together 

 several shorter pieces and obtain effectively a longer piece, thus in- 

 creasing the accuracy of the measurements. The density of this speci- 

 men at 20° was found by weighing to be 10.185. The second specimen 

 was in the form of drawn wire 0.051 cm. in diameter and 10 cm. long, 

 mounted as a tension specimen in the lever apparatus. Its density 

 could not be obtained with sufficient accuracy by weighing, but the 

 average density found by the General Electric Company for wire of 

 this diameter is 10.20. 



The regular series of runs, at 30° and 75°, were made for each speci- 

 men. The accuracy of the measurements was about the same for the 

 two specimens. Discarding 5 points, the average arithmetical de- 

 parture from a smooth curve of the remaining 50 points was 0.36% of 

 the maximum pressure effect, and the departure from linearity (that 

 is, the departure from linearity of the difference of compressibility of 

 iron and molybdenum) was 1.40% of the maximum pressure effect. 

 The departure from linearity of each specimen was sensibly the same 

 at the two temperatures. The final results are : 



AV 



— = - 10- 7 (3.47 - 1.2 p) p 

 I o 



AT' 



— = - 10- 7 (3.48 - 1.2 p) p 

 » o 



A T7* 



— = - 10- 7 (3.61 - 1.0 p) P 



» 



t^L = -10- 7 (3.62-1.0p)p. 

 > o 



The compressibility of the drawn wire is seen to be higher than that 

 of the swaged rod in spite of its higher density, as was also the case for 

 tungsten, and probably for the same reason. 





