NEW LAW IN THERMOCHEMISTRY 5 



Let K represent the heat of combustion of any one of these 

 h3^drocarbons ; then in the quadrupled equations /\K must be 

 taken. Now let a be the number of COg molecules produced ; 

 h the number of molecules of gaseous H^O ; c the number of 

 oxygen molecules dissociated during combustion, and n the 

 number of atomic unions or linkings in the single molecule of 

 the compound burned. Then taking these data directly from 

 the quadrupled equation, we have the subjoined expression : 



\K 



12a -\- 6d — c — 8n 



= constant. 



The two plus quantities in the divisor represent combinations ; 

 the two minus quantities stand for decompositions, and all the 

 terms of the fundamental equations are thus utilized. 

 Let us apply this formula to the methane equation : 



4A- + 8/ — 8-z — ^r= ']6^ 336 = ^K. 



Here a = 4, /; = 8, ^ = 8 and ;/ -= 4, the last factor indicating the 

 four unions of hydrogen atoms with carbon in the symbol CH^. 

 In ethane ;/ = 7, in propane 10, etc. ; all linkings, whether of 

 hydrogen with carbon, or carbon with carbon, being treated as 

 thermally equal. Now 12a -^ 6b — c — Sji = 56, which is the 

 divisor applicable to methane. The quotient obtained is 13649, 

 and this quantity I have indicated as a constant. In the follow- 

 ing table for fourteen aliphatic hydrocarbons its constant char- 



Compound. 



Methane 



Ethane 



Propane 



Trimethyl methane .. 

 Tetramethjl methane 



Diisopropyl 



Ethylene 



Propylene 



Isobutylene 



Isoamylene 



Acetylene 



Allylene 



Diallyl 



Dipropargyl •. 



^. 



H2O Liquid. 



847720 

 I 48 I 760 

 21 16848 

 2748760 

 3388440 

 3996800 

 1333400 

 1970960 

 2602480 

 3230520 

 I 240200 

 1870200 

 3731280 

 3531520 



H„0 Gas. 



764336 

 1356684 

 1950080 

 2540300 

 3138288 

 3704956 

 1250016 

 1845884 

 2435712 

 3022060 

 I 198508 



I 7868 I 6 

 3522820 

 3406444 



56 

 98 

 140 

 182 

 224 

 266 

 92 



134 

 176 

 218 

 86 

 128 



254 

 242 



Quotient. 



13649 



13844 

 13929 



13957 

 14010 

 13928 

 13587 

 13776 



13839 

 13862 



13936 



13959 

 13869 

 14076 



Mean, 13873 



