i6 



CLARKE 



Cyanogen itself gives 2 + (5 x 2) = 12, and acetonitrile has 

 (4 X 2) -f 5 = 13. Nitrogen, then, in its combinations with car- 

 bon, must be assigned at least two thermal values, but these are 

 still multiples of the henotherm, the fundamental quantity. 

 Possibly the differences may discriminate between quinquiva- 

 lent and trivalent nitrogen, although the data are too few to 

 settle this point definitely. 



In the combustion of organic sulphur compounds, at least in 

 the examples given by Thomsen, SOj is produced, and this im- 

 plies a distinct factor in the divisor of the general formula. If 

 s represents the number of molecules of SOg formed, the factor 

 to be added is 95, and the formula becomes 



p^ — ' s— = constant. 



12a + 00 + gs — c — on 



From this expression the absolute heat of formation of SOg from 

 isolated atoms of sulphur and oxygen is nine henotherms, or 

 123 300 calories ; while the ordinary value, as derived from the 

 normal molecular elements, is 71000. Add to the latter the 

 13 700 calories due to the dissociation of oxygen, and the sum 

 is approximately six henotherms, leaving three henotherms as- 

 cribable to the gasification and isolation of one sulphur atom. 



Three of the compounds studied by Thomsen contained the 

 cyanogen group, and for these the divisor of the general 

 formula must be modified exactly as was done with the other 

 cyanides. So much assumed, the formula can be applied as 

 follows : 



Mean, 13773 



There are three other sulphur compounds in Thomsen's list, 

 to which the formula does not apply. Thiophene is a ring com- 



