( 549 ) 



vapour pressure curve. Beforehand lilde is lo be said about this 

 course; an increase of temperature at constant pressure will promote 

 the splitting up, because the dissociation takes place endotliei-micallj, 

 increase of pressure on the other hand will oppose it. Now increased 

 temperature always accompanies increased pressure along the P-T 

 line, and it remains the question which influence is the greater one. 

 This consideration had already led us, in connection with the 

 reasoning of § 1, to the jiossibilitj of a point of inflection in the 

 P-T line. The absence of a point of inflection in the P-T line 

 (according to § B) in the temperature region examined bj^ us here 

 corresponds to a gradual change of the degree of dissociation as 

 function of T along the P-T line ; it appears from the subjoined 

 table that the degree of dissociation increases with the temperature, 

 that in other words the ascending temperature exerts a greater 

 influence on the splitting than the increasing pressure on the formation 

 of N^O^-molecules. 



TABLE V. 



It will perhaps be superfluous to emphasise particularly that these 

 values of the degree of dissociation expressed in percentages in the 

 above table, are only intended as a rough calculation, because 

 Schreber's formula is only an approximate formula, and these values 

 have, moreover, been found by extrapolation to the region where 

 the gas phase in equilibrium reaches its point of condensation ; for 

 a survey of the course of the degree of dissociation and the last 

 mentioned conclusion, however, the above table is perfectly sufficient 

 in our opinion. 



Anory. Cliem. Laboratory oj the 

 University of Amsterdam > 



37 



Proceedings Royal Acad. Amsterdam. Vol. XIV. 



