the melastable prolongations of SL,G and SiiL,G. The determinations 

 were difficnlt; the only way to find the eqnilibria was by examining 

 whether rise of pressnre or descent of pressnre takes place at constant 

 temperature after some lapse of time. It is clear that below the 

 three-phase line SSbG (fig. 4a) the two-phase coexistence Sb -f- G is 

 found, and above it S -f- G and S -(- Sb, because S with regard to 

 its concentration lies between G and Sb, and the coexistence of the 

 two solid substances will extend towards higher pressure ^). Hence 

 the transformation Sb -(- G ^ S occurs on the three-phase line. The 

 upper arrow indicates the conversion on diminution of volume, 

 the lower one on expansion. When at a definite temperature a fall 

 of the pressure takes place, we are above SSa G ; when the pressure 

 increases, we are below SSb G. In this way an upper and a lower 

 limit was found, which were no fuither apart than one atmosphere, 

 sometimes some tenths of an atmospheie. The slowness of the 

 transformation rendered this method of working necessary ; the lower 

 limit was found to yield values which were better reproducible than 

 the upper one. The explanation of this is in my opinion to be found 

 in the fact that the transformation S — > Sb + G takes place more 

 easily than the opposite one. This is self-evident, as the action of 

 G on Sb can exclusively take place on the boundary of the two 

 phases, and formation of a phase S can stop the action. Accordingly 

 the values of the lower limit are recorded in table 4; besides, the 

 uppei' limit often differs no more than a fraction of an atmosphere 

 from the lower one, as has been said. The relative situation of the 

 three-phase lines is actually that which was predicted with the aid 

 of the quadruple point rule. 



8. The analysis of the compound did not present any difficulties. 

 The results of the analyses were resp. 1.00, 0.97, and 0.99 mol. CO, 

 to 1 mol. p-toluidine. Hence the compound contains equal molecular 

 quantities of the two components. 



9. Summary of the results. 



The four examined systems yield pretty well coinciding three- 

 phase lines LJjjG. The critical end-points lie close together. The 

 great difference, between the systems consists only in the situation 

 of the quadruple points. In table 5 the four systems are arranged 



^) This can also be immediately derived from the relative situation of the three- 

 phase lines in fig. 4a. 



44* 



