175 
we substitute the values pj; = 100 and 7, = 158.2 + 273 = 4381.2, 
our observations yield values of / varying with the temperature, as 
will be clear from the subjoined table II. 
TA BLE it 
t 7 P f | t t P | f 
7.0 280.0 Is 4.25 100.5 373.5 20 | As 
21.2 204. 2 1 4.3 123.8 306.8 40 4.6 
BGG 319.6 3 4.35 138.8 411.8 60 [4.7] 
79.4 352.4 10 4.5 150.0 423.0 80 [5.0] 
The value of f appears really to reveal the dissociation; it lies, 
namely, much higher than that of normal substances (+ 3), even 
higher than that of substances as water and alcohol. It appears at 
the same time that f rises with the temperature, whereas the reverse 
takes place for water and alcohol. 
So the inclination of the —7-line increases more rapidly with 
rising temperature than for a normal substance. 
In the graphical representation, which occurs in the Theoretische 
Chemie of Prof. Nernst’), in which — log = is taken as ordinate, 
Pk 
Tr 
7 
in opposition to that of water and aleohol is concave seem from 
below, and yields a branch of the fanlike sheaf of lines, which lies 
still higher than all those indicated in the graphical representation. 
We have put the last two values for f in table II between paren- 
theses, as these change resp. 0.1 and 0.2 by a change of one 
atmosphere in the value of /;, and are therefore distinctly inferior 
to the preceding ones in accuracy. 
6. As appears from the change of colour of liquid and vapour 
with rising temperature the increase of the degree of dissociation 
is accompanied by an increase of darkening of the colour according 
to table IV of our former communication. Hence the supposition 
naturally suggests itself, that the brown colour is owing to the split 
molecules, whereas the unsplit molecules are colourless. This suppo- 
sition has been confirmed by the investigation of SALET *), who has 
— 1 as abscissa, nitrogen tetroxide yields therefore a line, which 
1) p. 237 (1909). 
2) (i. r. 67. 488 (1868). 
