fiOO 



Formerly (communication \^ and VI) we have deduced several 

 rules for the movement of the sides of a threepliasetriangle on change 

 of pressure. When a saturationcurve under its own vapourpressure 

 and its corresponding vapourcurve are removed comparatively far 

 from the point F, the formation of vapour from F -\- L takes place 

 on increase of volume and the formation of liquid from F + (} on 

 decrease of volume. The threephasetriangle turns on increase of 

 pressure in such a way that the conjugationline solid-vapour goes 

 ahead ; on decrease of pressure it turns in opjiosite direction. If in 

 fig. 2 we make triangle Faa^ or Fbh^iwYw towards higher or lower 

 pressures, we see that these movements are in accordance with the 

 previous rules. 



Also we may imagine on curve luihii a point of maximum pressure 

 if and on curve li^aj)^n^ the corresponding point M^; the points i^, 

 M and M^ are then situated on a straight line. The pressure then 

 increases from h and n towards M. Triangle Faa.^ must then also have 

 another position as is drawn in tig. 2 ; the line Fa must viz. be 

 situated closer to the side Fli^ than the line Fd^. Therefore, when 

 we take two threephasetriangles, situated on different sides of the 

 line FMM^, they turn their sides solid — gas towards each other. 

 We see that this is also in accordance with our previous considerations. 

 We may also imagine a point of minimum pressure m on curve 

 liabn and the corresponding point iii^ on curve 

 //, n^ (6j 11^. Triangle Fhb^ must then have another 

 position ; the line Fh^ must tlien be situated 

 closer to the side Fii than the line Fh. 



Tx <C J^'<C ^^V- We now take a temperature 

 7Miigher than the point of maximum sublimation 

 7/v, but lower than the minimum-meltingpoint 

 7'/' of the substance F. In a similar way as 

 we have deduced for the general case fig. 7 (1), 

 we now find a diagram as fig. 3. Curve hab?i 

 is circumphased, curve li^aj)^n^ exphased. Fur- 

 ther, it is assumed again that on these curves 

 neither a point of maximum- nor a point ot 

 minimum pressure occurs. Because the points a and a^ are removed 

 comjiaratively far from the point F, the above mentioned rule 

 applies again to the moving of triangle Faa^ on change of pressure; 

 we see that its turning is in accordance with this rule. 



It is different with triangle Fbb^, its points b and b^^ are to 

 be imagined close lo n and n^. Let us at first contemi)late the 

 equilibrium F -f- liquid n -\- vapour n-^ of the binary system BC. 



