1504 
NH,Cl in the vapour, we get two lines A’B’ and C/D’, which 
would hold resp. for the evaporation without dissociation of B- and 
a-NH,Cl. These lines intersect again at the transition temperature 
If with WhrescHemEer we, therefore, assume that the «-form stable 
at the ordinary temperature could continue to exist above the 
transition point, we should find the line OD, if the homogeneous 
dissociation continued to exist; if, however, the dissociation in the 
vapour phase does not set in, the realizable states lie on O’D’. 
Accordingly the vapour tension values of JoHNson’s experiments lie 
on O/D’, the vapour pressure determinations of ordinary (somewhat 
humid) NH,Cl on OB. It is clear that the equality of the pressures 
in humid and in dry state over an appreciable range of tempera- 
ture becomes a coincidence, and that strictly speaking equality of 
pressure could only occur in a point of intersection of OB and 0’ D’, 
280 
260 
240 
220 
2.00 
180 
1.95 1.90 1,65 1.80 1.75 1.70 1.65 1.60 
Fig. 4, 
If we should wish to accept this explanation, we shall have to conclude 
from the results that the differences in vapour pressure over the 
examined temperature range are only small and lie within the 
errors of observation. It is, therefore, now the question whether 
the investigations mentioned allow of such an explanation. 
