40 THE COMPRESSIBILITY OF CARBON, SILICON, ETC. 



SUMMARY. 



The method of Richards and Stull of determining the compressibilities 

 has been applied to five more non-metals. 



The compressibility of silicon was found to be not over 0.1G X 10" 8 , 

 silicon being the least compressible of the thirty-five elements thus far 

 investigated. 



Carbon in the state of graphite was found to be filled with minute pores 

 which interfered with the exact determination of its compressibility. 

 Nevertheless, this quantity may safely be said to be not greater than 

 3 X 10- 6 . 



The compressibility of carborundum (SiC) was found to be 0.21 X 10" 6 , 

 but little greater than that of silicon. From these results and from other 

 compressibilities it is concluded that the compressibility of diamond can 

 not greatly exceed 0.5 X 10" 6 . 



Red phosphorus was found to have a compressibility of 9.0 X 10~ 6 , less 

 than half of the value for white phosphorus. Thus for the first time dif- 

 ferences in compressibility caused by change of allotropic form are illus- 

 trated by actual experiment. 



Sulphur and selenium were found to have, respectively, compressibilities 

 amounting to 12.5 X 10~ 6 and 11.8 X 10~ G - All these values are expressed 

 in megabars, and give the average compressibilities between 100 and 500 

 megabars. 



