SIB B. C. BEODIE ON THE CALCULUS OF CHEMICAL OPERATIONS. 



817 



Combinations of the Prime Factors a, |, and 6. 



(4) Symbol of Selenium. — The vapour-density of selenium exhibits similar anomalies to 

 the vapour-density of sulphur. But from the experiments of Deville there can be 

 little doubt that at a sufficiently high temperature it would accord with theory. Deville 

 found for the vapour-density of selenium at 860°, 8-2, and at 1040°, 6-37. On the hypo- 

 thesis that 2 volumes of selenide of hydrogen are decomposed into 2 volumes of hydrogen 

 and 1 volume of selenium, the vapour-density of selenium would be expressed by the 

 number 5 '44. I shall assume this as the correct number. 



We have, then, putting a^X""' as the symbol of selenide of hydrogen, and a"X"' as the 



symljol of selenium, 



2a'">i'"' = 2a+ «">."', 



whence, as in the two last examples, 



2m=2-\-n, 2mi=/ij, 



and 



a mmimura. 



n=0, «i=2, 

 m=l, Wi=l, 



Assuming the density of selenide of hydrogen as 41, 



w(X)=40. 



Combinations of the Prime Factors a, |, 6, and X. 



