673 



line SSbL, that the slope will be steep. Of three of the three-phase 

 lines that pass through the quadruple point SSb^^G the situation 



Fig. 3. 



could, therefore, easily be given. The fourth three-phase line SSrG 

 was, however, difficult to find. The quadruple point rule mentioned, 

 however, gave me an indication where it was to be found. There 

 ex^ist two possibilities for the situation of this fourth three-phase 

 line, wdiich are represented by fig. 4^ and b. The three-phase line 



Fig. 4a. Fig. ib. 



SSbGt must namely lie between the metastable prolongations of SL,G 

 and SbL,G (fig. 4aj or between those of SL,G and SSbL, (fig. 4:b). 

 Other situations are impossible, because else two-phase coexistences 



44 



Proceedings Royal Acad. Amsterdam. Vol. XXI. 



