802 



Dr. ScHEi'FER liad already derived in his cited investigation, but 

 wliicii had been left unpublished, as the essential part appeared to 

 have been published already by Schreinemakers, and the derivation 

 of' which only diifers somewhat in form. In his investigation on the 

 quadruple point rule Sen effer demonstrated that no two-phase coexist- 

 ence can exist over a spacial angle greater than 180°. Making use 

 of the tilling up of the space round the quadruple line by two- 

 phase coexistences, he came to the quadruple point rule. The follow- 

 ing figures liave been constructed by him through application of 

 the same principles for the quintuple points. The P, T-figures round 

 the quintuple point were derived thi-ough the application of the 

 principle of the filling up of the space round the quintuple point, 

 which is now four-dimensional, and must consist of three-phase 

 coexistences, combined with the rule that three phase coexistences 

 in stable state can only occur over angles which are smaller than 180°. 



Fig. 9. 

 In the figures 8, 9, and 10 are given three-phase-coexistences 

 which successive regions have in common and which must lie 



