evidently not yet set in, whereas this was indeed the case at 567°. 
It was therefore supposed that now at a higher temperature like- 
wise agreement with the vapour tension line of violet phosphorus 
would be observed, but when the temperature was raised to 578°, 
a slow increase of pressure took place. When the experiment was 
finished the pressure amounted already to 39,5 atm., the vapour 
tension of violet phosphorus amounting to 35 atmospheres at the 
same temperature. 
After cooling to room temperature (17°) the pressure appeared to 
amount to 20 em. Hg. This pressure corresponds to 0,77 atm. at 
578°, so that the corrected pressure amounted to 38,7 atm., Le. 
3,7 atm. higher than the vapour tension of violet phosphorus. 
From the vapour tension determinations of the black phosphorus 
mentioned here it follows that at a temperature + 560° a vapour ten- 
sion is observed about equal to that of violet phosphorus. At lower 
temperatures the vapourtension of the black P was found below, 
and at higher temperatures above that of the violet. 
It might be supposed that it is possible that the vapour tensions 
of the black modification actually lie ander the vapour tension line 
of the violet phosphorus at temperatures below + 560°, and above 
it at higher temperatures. Then the two vapour tension lines would 
intersect, and this intersection would mean a transition point between 
the black and the violet phosphorus. A closer examination, however 
shows that this would mean a highly remarkable phenomenon. 
To demonstrate this, we must once more return to the fact that 
Smits and BokHorsr have succeeded in disturbing the violet phos- 
phorus in such a way that a vapour tension line was obtained from 
which followed that the vapour tension of this disturbed state of the 
violet phosphorus was smaller than that of the black. After treatment 
with iodine at 410°, hence still below the supposed transition point, 
the violet phosphorus entirely resumed its former form, the vapour 
tension again becoming perfectly normal: This normal pressure 
amounted to more than 2 atmospheres at 445°, the pressure having 
risen from a value below the vapour tension of the black phosphorus 
to a pressure far above that pressure. 
If the intersection supposed just now actually exists, the black 
phosphorus would be stable below + 560, and then the phenomenon 
would present itself that a state beginning with a vapour tension 
smaller than that of the stable state was converted by a catalyst at 
temperatures below that of the transition point to another state with 
a higher pressure than the stable state. 
We will point out here, that this is possible according to the 
