ÜB 



phosphorus will differ from the wliite fliiefly in this that it contains 

 a niiicii larger proportion of associated molecules. 



In lliis case tlie psendo system, as was already explained several 

 times, will possess no euteclic point, and llien tliis pseudo system 

 with the unaiy system lying in it, can bo given schematically by 

 fig. 5. If the pseudo-component /i was isomer of (t, also a figure 

 like fig. 6 would be possible. 



Note. When according to form. 14 we calculate the pressure corresponding 

 with the temperatine of 695°, which is the critical temperature of the licjuid phos- 

 phorus according to \V. A. Wahl's measurements, we find 82,2 atni. This is 

 tjjerefore the critical pressure, for wliich we found 83.56 in our preceding com- 

 municalion by means of the assumed linear relation. 



When we calculate the ^-value from the critical pressure 82,2 atm. and the 

 absolute critical temperature of 69(3" + 273^ = 968°, and from this the size of the 

 phosphorus molecule, we find 4.33; we found 4.26 before, which makes no 

 difference of any importance. 



According to the formula: 



/ = 0,4343^ ^r^^;^ '« /u- J 



the following values are found for the value of f at dillerent temperatures: 



from 200° to 300° /^S,!! 



, 300^ , 400° f = 2,84 



, 400=^ , 500° f = 2,60 



, 500° , G00° f = 2,40 



Amsterdnin, April 19, 1915. Anory. Chemie. Laboratory 



of the University. 



Chemistry. — "In-, mono- and dirariani eqniUJiriit" I. By Prof. 



F. A. H. SCHKKINKM AKERS. 



1. Introduction. 



When n -\- 2 phases occur in an etpiilibrium, which is conijiosed 

 of n substances, then it is invaiiant; the composition of the phases, 

 the pressure and the temperature are perfectly defined then. In a 

 7^7'-diagram this equilibrium is represented by a point; we shall 

 call this pressure and this temperature ƒ*„ and 1\. 



As this equilibrium is completely determined in every respect 

 neither the composition of the phases, nor the pressure or the 

 temperature can change on addition or withdrawal of heat or on 



') In the preceding communication the term ^np^. had been erroneously omitted. 



