94 J. Thomsen’s Thermochemical Investigation 
Again, a very remarkable relation appears when we compare 
iapustinens as in table VI, the values of 7, g, v, and v 
TaBLE VI, 
y = 14,573¢ 
a x 
— c —_ oo — 
q = 14,687 i a 
“ % 
0, = 14,805 + > =r + > 
Vq = 15,033° + @ =r + &. 
It seems highly ibe yi that the numerical term is the same 
in all these values; an e fact that the same constant fre- 
quently appears as a peth t in the data of thermo-chemistry 
renders this conclusion still more probable. Thus we find 
that the heat of formation of HCl, NO and H,0 (in the condi- 
tion ey all as aeriform products under constant pressure 1s 
as follow 
H.+Ol,= 44,000: —3 x 14,667 
No + Og = — 43,150° = 8 x 14,383° 
H.+0 =  57,610°= 4 x 14,402° 
The constant we have represented by 7 has evidently then 
an important significance, and its most probable value is that 
deduced by the method of least squares from all the observa- 
tions on the series of hydrocarbons containing two atoms 0 
carbon, as shown by table III. If we take then r=14,573 as 
the true value and g=r+3, we can easily deduce a second 
value of d from the data Even in the table on page 92. Since 
39,100°=—2d+8q, we have by substituting the value of 4, 
d=38,742°+a. From the oxides of carbon we have d=39,200" 
+a, The mean of these Nigh omitting the last two figures as 
insignificant, is d=38,900°+ 
The following are, now, the most probable values of the 
chief constants used in this investigation : 
TABLE a 
d = 38,900°+ = = 14,570¢ 
GS r+ to ¥ = 67,880¢ 
. Fo r+ 4% Vq = T+ 
= + 3a MW = —%& + 2% 
With these values we can calculate the heat of formation, 
under constant volume, of a hydrocarbon cis eee us 
carbon and yeaa gas, by means of the equa 
(C,, H,,) = — nd + 2mq + Se (17) 
in which the 2v is the sum of the calorific effects resulting 
from the union of the carbon atoms with each other. The 
results are inde ol acre of the unknown quantity # which is 
eliminated in reducing the equation. Since, as just stated the, 
unknown quantity # is always eliminated on solving the last 
