641 
TABLE 1. 
mans a es a nt ve mg 
yi | log Ky | 9a Ì 9b | 9 | 9d | Ve | of Og 
pease | 0 | --0.0k Ae | 0.01 | —0.01 | 0 
1395 | —11.84 | —0.07 | —0.08 | -0.07 | —0.07 | —0.07 | —0.07 | —0.08 
1400 | ~—11.77 | —0.05 | —0.06 | —0.06 | —0.05 | —0.05 | —0.05 | —0.06 
1443 | —11.11 --0.08 —0.09 —0.10 -0.09 —0.09  --0.09 | —0.10 
1478 | —10.79 | +0.07 | #0.07 | +0.07 | +0.06 | +0.07 | 40.07 | +0.06 
1498 | —10.28 | —0.18 | —0.18 | —0.18 | —0.18 | —0.17 | —0.17 | 0.18 
1500 | 10.50 | +0.06 | +0.08 | +0.08 | +0.07 40.07 | +0.07 | +0.07 
1565 | — 9.88 | 40.26 | +0.28 | 40.21 | +0.26 | +0.28 | 40.28 | +0.26 
| 
It will be clear from this table that the six expressions 9a—f, 
which in the most accurate way take the specific heats into account, 
and the formula 9g, in which the specific heats do not occur, repre- 
sent the observations equally well. The sum of the deviations in 
absolute value is successively : 
OTT: O87, 0.88, 0.78, OSL, 0.81) sand 0.81. 
This example shows clearly that the said deviations must be 
attributed to errors of observation, and that a change in the specific 
heats has not much influence on the equilibrium expression. 
3. The hydrogeniodidedissociation. 
On a former occasion | discussed this equilibrium at length, taking 
the specific heats of the substances taking part in the reaction, into 
account *). My purpose was then to test an expression derived by 
Prof. van per Waars Jr. for the gas dissociations. | have now also 
examined whether the simplest expression (equation 2) can be applied 
to this equilibrium, If we graphically represent /og K as function 
of 7'-!, and if we draw a straight line through the points as well 
as is possible, we find: 
600 
log K = — — — 0.856. . B kred) LOM 
In table IL the values yielded by this expression, are compared 
with those that follow from the formula derived before: 
529 zit 
log K = — A —log\ 1— e. F.J) — 1.079 ss (LOB) 
1) These Proc. 17, 1022, (1915). 
41 
Proceedings Royal Acad. Amsterdam. Vol. XIX. 
