CLARKE 



Mean, 13815 



For carbon tetrachloride the heat of combustion, as giv^n by 

 Thomsen, is 75 930 calories. Hence ^K = 303 720. Applying 

 the proper divisor to this quantity, we have a quotient of 15 186, 

 a value far too high. The actual measurements, however, 

 were made by a complex process, and may well be somewhat 

 uncertain. Farther investigation is necessary in the case of car- 

 bon tetrachloride, since this one possible failure of the formula 

 cannot counterbalance its nineteen successful applications. 



What, now, is the meaning of the formula, and of the con- 

 stant which is evidently derived from it? A consideration of 

 this question may conveniently precede the discussion of other 

 thermochemical quantities. First, however, I may call atten- 

 tion to the fact that the formula itself can be condensed and 

 simplified. Taking the hydrocarbons as the least complex of 

 the compounds we have studied, the expression for them may 

 be given in three forms, thus : 



4^ 



\K 



4^ 



12a ■\- 6b — c 



II 



[a^^^-^n 



C — QU 



= constant. 



The difference between these expressions arise§ from the fact 

 that the oxygen consumed is always proportional to the carbon 



