(893%) 
As was shown in the preceding eommunication’) on this subject, 
this has reaily already been observed in the melting-point determi- 
nation of the rhombic sulphur. 
The first substance that was closely examined by us in this 
direction was the white phosphorits. 
Theory has already drawn attention to the fact that not only the 
violet, but also the white phosphorus is built up of different kinds 
of molecules, so that the possibility existed, that the complexity of 
this metastable modification could be demonstrated. 
Experiment has corroborated this supposition, and that so convin- 
cingly that as yet no substance is known, by means of which 
the validity of the theory can be demonstrated in so simple and 
clear a way as by means of the white phosphorus. 
Before this result was obtained, however, a great difficulty had 
to be surmounted, which consisted in the preparation of pure phosphorus. 
It appeared, namely, that none of the known methods yielded a 
product that melted in a unary way also when the supply of heat 
took place very slowly, i.e. a substance was always obtained which 
presented a range of melting temperatures. 
The melting-heat of white phosphorus being so small (5 cal.), an 
exceedingly slight quantity of a second substance can already cause 
an appreciable range of melting temperatures, and it was therefore 
to be foreseen that the preparation of a product melting at one and 
the same temperature might present peculiar difficulties. 
As it appeared that the last contaminations must chiefly consist 
in the oxides of phosphorus, which cannot be sufficiently separated 
from the phosphorus by the usual methods of purification (treatment 
with potassium dichromate and sulphuric acid, distillation with steam, 
etc.) an apparatus was constructed (fig. 1), in which the phosphorus 
was distilled in vacuo, and then subjected to a repeated partial 
crystallisation, after which it was transferred, thus purified, to a 
melting point determination vessel. 
The latter is represented in fig. 1 by A. A resistance thermometer 
is sealed to it; this vessel is connected with three bulbs B, C, and 
D, the last of which (capacity 500 cm.) at first filled with water, 
was afterwards filled for three quarters with pieces of commercial 
so-called pure white phosphorus. 
After this phosphorus had been melted under water, and had 
then solidified again, the water was poured off, leaving only a thin 
layer, and then the tube d was sealed. 
I. he 
