994 
As BripamMan says, we should be inclined to infer that black 
phosphorus is the stable modification, but he did not succeed in 
confirming this conclusion in another way. Thus he heated among 
others a vacuum in which a dish with black and a dish with violet 
phosphorus was placed, at 445° for six hours. If black P was really 
the stable, violet P the metastable modification, the weight of the 
black P would have to increase at the expense of the violet P. 
Instead of an increase in weight of the black P an exceedingly 
small decrease of weight was found. 
He further heated violet and black P together in an exhausted 
glass tube at 620° fer 20 minutes. The violet P melted, the blaek 
did not. If now the black P was the stable modification, the black 
P would have to increase in quantity at the expense of the molten 
violet modification; this, however, was not the case. 
2. Under the vapour pressure the black phosphorus is probably a 
metastable state. 
When this paper by BribgmMan appeared, the vapour pressure line 
of the violet P had already been determined, and now it was very 
remarkable that as was explicitly stated, after evaporation of the 
violet P in vacuo at 360° Smits and Boksorst ') obtained a substance 
which possessed a vapour tension of 0,64 atmospheres at 445°, as 
appears from the curve N°. 75, whereas Bripeman found that the 
black P at the same temperature showed a vapour tension of 58.5 
em. Hg. or 0,77 atm. 
Hence it appeared that this substance obtained by Smits and 
Bokuorst, possessed a smaller vapour tension than BRIDGMAN’s black P. 
Now it was further found by Smits and Boknorsr that the sub- 
stance with this abnormally low vapour tension was a state of the 
violet phosphorus which bad been greatly disturbed by the said 
evaporation, and that after heating of this substance at 410° in 
contact with 1,5°/, iodine the internal equilibrium had set in again, 
and the substance had resumed the normal vapour pressure. 
It followed from these experiments that Briweman’s black phos- 
phorus, at least under the vapour pressure, is probably not the stable 
modification. 
3. Vapour pressure determinations. 
It seemed, however, very desirable more closely to examine this 
new form of the phosphorus, for which reason a request was sent 
1) These Proc. XVII, p- 962. 
