1025 
been inserted in the above table in the fourth column, were caleu- 
lated from the values of this pressure. 
PAS Bs. By, ol 
EIEREN Ei log K log K (corr.) ee aby 
| | 4 
1022 | 1295 | 0.329 1.221 — 1.368 — 1.210 
| | 
1217 1490 0.3755 | — 1.044 | — 1.384 — 1.115 
| | 
The values of the fourth column have been caleulated on the 
assumption that all the iodine is present as /,; this now is certainly 
not the case according to the determinations of the iodine dissocia- 
tion (see § 5). At these temperatures the iodine has already percep- 
tibly been split up into atoms, and specially at the low iodine 
tension of these experiments the splitting up will be great. Through 
the correction which is to be applied for this, log K of column 4 
becomes smaller. 
Let us suppose the iodine to be partially split up into atoms 
(degree of splitting y), then the total iodine pressure is not equal 
to the hydrogen pressure, but 1+ y times greater. Let us call the 
hydrogen pressure Py,, the total pressure /, then we have for the 
partial tensions of hydrogen, iodine atoms, iodine molecules and 
iodine hydrogen : 
Pro on dem vel gh Pa, ande, Bo oe. 
Hence the equilibrium constant for iodine hydrogen becomes : 
ects (uaa 
__ [P—Pa,(2+y) 
and that for the iodine dissociation expressed in partial pressures : 
2 
K mi 
‚ (23) 
Pu, . 5 ‘ è ‘ . ‘ e (24) 
AR —: np 
Now from the equation for the iodine dissociation (equation 18) 
follows for the equilibrium constant (in partial pressures ; pressure 
unity the atmosphere) : 
Pa l295 log K}, = — 0.668 
(25) 
T = 1490 log Kj, = + 0.148 
If we now introduce the values of 25 and the found values of 
Py, into 24, y may be calculated from it. This value of y sub- 
stituted in 28, yields the values log & (corr.) of table XI. When 
68 
Proceedings Royal Acad. Amsterdam. Vol. XVII . 
