COMPRESSIBILITY OF METALS. 213 



1(H (corrected for the new value of iron) as the average to 10000. 

 The initial values of these two observers fall within the extremes above, 

 but the decrease of compressibility with pressure found by A. W. J. is 

 somewhat greater than the larger of the two above values. 



Antimony. Two different specimens from two different sources 

 were used. One was so-called chemically pure antimony from the 

 J. T. Baker Chemical Co. It was cast in a graphite mold, the mold 

 being preheated to above the melting point of antimony, and chilled 

 by slowly lowering into water. The second specimen was antimony 

 from Kahlbaum, his "K" grade. I have no analysis, but antimony 

 from this source is known to be of high purity. This also was cast, 

 but by pouring into a groove machined in a massive iron bar, the bar 

 being cold. The manner of chilling the two castings was therefore 

 entirely different, and the crystalline orientation in the two castings 

 should be different. The casting of Baker's antimony, which was 

 14.6 cm. long, was mounted as a compression specimen in the appara- 

 tus for direct measurement without magnification. Its density at 

 20° was 6.678. The other casting, which was given its final shape by 

 grinding, was 2.3 cm. long, and was mounted as a compression speci- 

 men in the lever apparatus for short specimens. 



The regular series of runs at 30° and 75° was made on each specimen. 

 The average arithmetical departure from a smooth curve of the read- 

 ings on Baker's antimony (one discard) was 0.48%, and the maximum 

 departure from linearity was 1.67% of the maximum pressure effect. 

 For the casting of Kahlbaum's antimony the average arithmetical 

 deviation from a smooth curve (four discards) was 0.68%, and the 

 maximum deviation from linearity was 2.7%. The results, computed 

 on the assumption of equal compressibility in all directions, are: 



Baker's antimony, slowly cooled in graphite, 



VA 



At 30° — = - 10- 7 (14.69 - 6.2 X 10- 5 p) p 



I 



i) 



AV 

 At 75° — = - 10- 7 (14.80 - 6.3 X 10~ 5 p) p . 



V 



Kahlbaum's antimony, rapidly chilled in iron, 



AV 

 At 30° — = - 10- 7 (20.41 - 12.9 X 10~ 5 y) p 



V 



o 



AV 

 At 75° -77- = - 10- 7 (20.50 - 12.9 X 10- 5 p) p . 



V 



o 



