804 



division as point of issue, the new division can come al)Oiit in two 

 dilFerent ways. 



In the P-T-üguves this comes to this that the region is enclosed 

 by two four-phase lines. The question is therefore reduced to this: 

 divide tlie concentration figure into triangles, and gradually change 

 this division, so that every time one fonrphase coexistence shows 

 the transition. When the division has been moditied five time, we 

 have passed round the quintuple point, and we ha\e again the 

 original division. 



In this way the three figures are easy to reconstruct. In the figures 

 the corresponding division is indicated in every region and it has 

 been indicated liy hatching on the quadruple lines what four phase 

 coexistences make the transition between successive divisions possible. 

 .Strictly speaking regions of one single homogeneous phase and the 

 two-phase coexistence would still have to be indicated in the con- 

 centration figures; for the survey and the construction these are, 

 however, not necessary. |Wlien the four-phase line is passed some 

 three-phase coexistences are left undisturbed repeatedly. Thus it will 

 be clear among others that in fig. 10 the coexistence 125 is not 

 disturbed by the four-phase line 2345; it occurs both on the left 



Fig. 1«. 



