967 
a curve with a perfectly regular course, so that there is no question 
of the occurrence of the discontinuity found before at 450°, which 
rendered the existence of a transition point, stating it mildly, very 
doubtful. 
First of all it had to be examined what was the cause of the 
discrepant result of the earlier, preliminary determinations, and 
whether a preparation prepared in the same way again yielded such 
a line with a break at + 450°. 
To decide this question a new preparation N°. 5 was made, chiefly 
prepared in the same way as N°. 1; white phosphorus with 0,2°/, 1 
was heated at 400° for 6 hours, then cooled very slowly to give the 
white phosphorus depositing from the vapour every possible oppor- 
tunity to be converted to violet phosphorus. 
This cooling lasted 14 hours, and when the tube was opened in 
the dark no emission of light could be observed. The obtained phos- 
phorus was not extracted with CS,, but only treated with water to 
remove oxidation products which might possibly be present, then 
washed with ether, and dried in a vacuum exsiccator over P,O, 
The vapour pressure line determined with this preparation in glass 
spring N°. 78, is represented in Fig. 1. We see from it that first 
four points were found which were much too high. In the determi- 
nation of the fifth point a remarkable phenomenon was observed, 
which threw light on the vapour pressure line determined earlier. 
After the pressure had risen to 2,99 atm. at 442°, and had remained 
constant for five minutes, the pressure began to descend at first 
slowly, then more rapidly, and at last again more slowly. 
When the phosphorus had been kept at the same temperature of 
442° for two hours, the pressure had fallen to 2,21 atm., a value 
which agrees pretty well with that obtained with the preparations 
NE DENS and. 4 
On continned investigation towards higher temperatures this agree- 
ment continued to exist, which follows from the subjoined table. (p. 968). 
The result of this experiment is of great importance, for in the first 
place it follows from this that violet phosphorus prepared in the same 
way as for preparation N°. 5, so by tbe heating of white phosphorus 
with a trace of iodium, consists without after treatment of violet 
phosphorus, which was very nearly in internal equilibrium at the 
temperature of preparation, and that by the side of it a little white 
phosphorus is found, which has deposited on cooling from the vapour 
phase after the preparation of the violet phosphorus. It must now 
be attributed to the presence of this quantity of white phosphorus 
that in our preliminary investigation, just as in this last-mentioned 
