i()7 



As this conversion is accompanied h^- a pretty 

 great generation of heat (4.4 Cal. at the ordinary 

 ^--*-.— jiJi temp.), and the velocity of this reaction is already 



pretty great above 325°, it would be possible that 

 the temperature of the phosphorus had been higher 

 than that of the surrounding bath, whereas it had 

 been assumed that inside and outside the apparatus 

 there always prevailed the same temperature. 



To avoid this possible error, not the temperature 

 of the hath, but that of the phosphorus had to be 

 measured. 



For this purpose with application of the dynamic 

 method according to Smith') the tube of the thermo- 

 element was fused into the vapour pressure apparatus, 

 so that always the temperature of the phosphorus 

 was determined. 



Afterwards when it had appeared that through 

 "^' *■ the contact with stearine the boiling point of the 



phosphorus was absolutely not influenced, the apparatus was used 

 represented in tig. 1. Into the inner tube n which has a constriction 

 at c a resistance thermometer has been fused, which reaches to the 

 lowest widening. This inner tube is filled up to above the constric- 

 tion with pure white phosphorus, which is then shut off by a layer 

 of stearine. All this takes place in vacuum. In the outer jacket e 

 also stearine is brought, which is heated under different pressures. 

 Just as for the other apparatus also now the temperature is 

 determined at which the phosphorus under a definite pressure begins 

 to boil. This method has this advantage that without any difficulty 

 the experiment can be made with larger quantities, and the tempe- 

 rature can be indicated \ery quickly and very accurately. 



By these two improved methods the following results were now 

 found : 



Temp. 



Pressure 

 in atm. 



331.8° 

 332.9° 

 342.0 

 355.7 



2.47 

 2.61 

 2.95 

 3.88 



1) Americ. Chem. Soc. 32, 897 (1910). 



