from lower temperatures, because passing from higher to lower 
temperature, the establishment of the equilibrium required far too 
much time. Owing to this we are unfortunately uncertain about the 
degree of the accuracy, but the error cannot be very great, as the 
preparations of different temperatures of preparation yield vapour 
pressure lines which, below 500°, differ comparatively little from 
each other in situation, with the exception of the very lowest points. 
2. Corroborations of the theory of allotropy. 
bese PY 
The theory of allotropy says that every phase of an allotropous 
substance exhibits the phenomenon of molecular allotropy, hence the 
violet phosphorus had also to be a state of internal equilibrium, 
which equilibrium is in general dependent on temperature and pressure. 
To test this view the following experiment was made. By sub- 
lination in vacuo it was tried to expel the more volatile pseudo 
component at a temperature at which the internal equilibrium sets 
in only very slowly, and the formation of the more volatile from 
the less volatile pseudo component takes, therefore, place with very 
slight velocity. If this succeeded, a substance would be obtained 
with a considerably smaller vapour tension than the preparation 
from which we had started. 
Keeping this purpose in view part of the preparation N°. 4, with 
which the vapour pressure line with manometer N°. 74 had been 
determined was heated in a glass tube for two hours in the bigh 
vacuum of the Gaede-pump at somewhat more than 360°, during 
which small drops of liquid white phoshorus condensed against the 
colder part of the tube. After the tube had been cut in the middle, 
so that the violet phosphorus was separated from the white, a new 
glass spring N°. 75 was filled with the thus obtained violet P N°. 4a 
without any further treatment, and then we proceeded to the deter- 
mination of the vapour tension. 
It now really appeared that the vapour tension of this preparation 
was much too low, which is clearly indicated by the vapour pressure 
line N°. 75 in our PT-figure. 
As this figure shows, this vapour tension line is not continued 
beyond 473°, because at this temperature a reading of the pressure 
was no longer possible on account of the continual slow rise of the 
vapour tension. Also this result was in perfect agreement with our 
expectations, because the internal equilibrium sets in already notice- 
ably at 473°. 
Now we might have continued the determination of the vapour 
