90 J. Thomsen’s Thermochemical Investigation 
other values of column III have been calculated, and we thus 
obtain what may be called the heat of combination under con- 
stant volume. 
TABLE I. 
‘ I TIL. 
1. CHa 213,530¢ 20,150°¢ 19,570°¢ 
2. CaHs 373,330¢ 25,670° 24,510¢ 
3. CsHs 533,500°¢ 30,820°¢ 29,950° 
4. CaHg 334,800° —4,160¢ —4,740°¢ 
5. CsHe 495,200¢ + 760¢ _ 
6. C,H 310,570°¢ —48, 290° —48,290°¢ 
ff 
members of a series of homologues corresponds in all cases to 
equal differences in the calorific power of their molecules. 
Thus from the above table we have 
CsHs — CoH, et 16 708 
CoHs — CH, = 1 9,800¢ 
C,H. nore C,H, = 160,400° 
and it is evident that the difference in question must be very 
closely 160,000°. 
f, next, we compare the heat of formation under constant 
volume of all the hydrocarbon molecules which contain two 
atoms of carbon, we find between these values, also, a manifest 
relationship, and from this the remarkable conclusions of the 
paper we are noticing have been deduced. 
TaBLeE II. 
Differences. 
C2 =-— 4, 
“+b = 4r 
C, + H, = 48,290°¢ 
- 43,550 = 3r 
C, + Hy= — 4,740¢ 
+ 29,250 = 2r 
Co + He = + 24,510°¢ 
9(0-+H,) = Os + He = + 39,140¢ 5 14630 = 7 
Now just as 2CH, is the limit of this series of molecules at one 
end, G, is evidently the limit of the series at the other end, and 
the symbol C, represents the theoretical molecule of carbon 1n 
the aeriform state occupying the unit of molecular volume, 
the two atoms of this molecule united by four bonds. Now 
if we represent the heat of formation of this molecule by —% 
it will be seen that the relationship exhibited by the table 
gives us at once the means of calculating its value. But it Is 
obvious that while the results given in the table are sufficiently 
accordant to exhibit their relationship, we should obtain quite 
different values for —a by combining different results, and the 
only correct method is to bring all the determinations into the 
Sg hs De a a 
