NEW LAW IN THERMOCHEMISTRY 



Compound. 



^K. 



H,0 Liquid. 



Methane 849600 



Ethane 1483600 



Propane 2106800 



Et-hvlene 1359600 



Propylene 199 1600 



Acetylene i 1 259600 



AUylene | 1889600 



H.O Gas. 



766216 



1358524 

 1940032 

 1276216 

 1866524 

 1217908 

 1806216 



Divisor. 



56 



98 



140 



92 



86 

 128 



Quotient. 



13683 

 13863 

 13786 

 13872 

 13929 

 14161 

 14111 



The organic halides, sulphides, and nitrogen compounds are 

 well covered by the general formula, provided that in each case 

 an appropriate factor be added to the divisor to indicate the 

 halogen, sulphur dioxide, or nitrogen produced during combus- 

 tion. Thus, for complete combustion of the halides, when free 

 halogen molecules, not halogen acids, are formed, the modifica- 

 tion of the formula is as follows : Let h represent the number 

 of chlorine molecules produced, h^ the bromine molecules, and 

 h^ the iodine ; then — 



For hydrocarbons, 



For chlorides. 

 For bromides. 

 For iodides. 



iia -\- 6b — c — '^n 



\2a -\- 6b -\- h — c — ^n 



4^ 



\2a -\- 6b -\- 2//j — c — ^n 



12a -{- 6b -\- 4/^2 — c — 8n 



= constant. 



= constant. 



= constant. 



= constant. 



The fundamental identity of the four expressions is obvious. 



Thomsen gives data for twenty-two of these compounds, and 

 only three of them are exceptional. Chlorobenzene is an aro- 

 matic body, and, like the corresponding hydrocarbons, demands 

 a special formula, which will be considered in due time. Car- 

 bonyl chloride is not completely dissociated upon burning, and 

 to it, therefore, the general formula is inappropriate. The re- 

 maining exception is carbon tetrachloride, and to this substance 

 we will recur presently. The nineteen compounds to which the 

 formula does apply are given in the following table. In each 

 case u represents the number of atoms in the single molecule, 

 minus one. 



