647 
Fe‚,0O, +4CO 23 Fe+4CO, will then be stable. It would be 
desirable, in my opinion to test this conclusion experimentally. 
If, therefore, the situation of the equilibria of the iron oxides with 
carbonic acid and carbon oxide is still insufficiently known, these 
equilibria are even quite in conflict with the determinations of 
DevitLE and Preuner’') concerning the reaction 3 Fe+4H,O=Z 
Fe,O, ++4H,, which was studied between 200° and 1600°. It is 
clear that when the above interpretation is correct, this equilibrium 
must be metastable with respect to FeO at the higher temperatures; 
FeO may have been present in these determinations, and the obser- 
vations may have been wrongly interpreted. 
In conclusion it may still be said that v. Jéprner’s calculations lead 
to the entirely divergent conclusion that FeO should be always meta- 
stable in the range from 600° abs. to 2400° abs. In these calcula- 
tions use has, however, been made of uncertain data and uncertain 
hypotheses. *) 
In his paper (These Proc. XIX, p. 175) Prof. ReINpers pointed 
out that the separation of iron carbide will give rise to new equili- 
bria: this formation, can however in my opinion not affect the above 
conclusion. This will be clear on a consideration of fig. 10 of 
Prof. Retnpers’s paper. 
6. The dissociation of ammonium bromide. 
In his researches on the homogeneous dissociation of the ammonium- 
halides Prof. Smrrn found a maximum at about 320° for the equili- 
brium constant of the ammonium bromide *): above this temperature 
the dissociation constant diminishes at rising temperature. This decrease 
is very peculiar, as evidently no heat is required here for the split- 
ting up of NH,Br into NH, and HBr but heat is liberated. At the 
splitting up of a molecule into two it might be expected that energy 
was required to neutralise the chemical attraction. 
At 320° the heat of transformation is zero as appears from equation 
1. When the value of # is calculated from Smitn’s line at the 
highest temperatures, 43000 cal. are found at the mean temperature 
of 384° C. Accordingly the heat of transformation varies over the 
range of 64° ©. by 48000 cal., hence the algebraic sum of the 
specific heats is about 670 cal. A value is expected for this sum 
which will not be higher than about 10 calories and with the 
opposite sign, as it is the difference between the specific heat of a 
1) PREUNER. Zeitschr. f. physik. Chem. 47. 416 (1904). 
2) v. Jiiprner. Theorie der Eisenhüttenprozesse (1907). 
5) Smtrn Journ, Amer, Chem. Soc, 37, 38 (1915). 
