1145 



mediately or, before il (leci-eayus, liist increase. Tliis latter is 

 certainly tlie case when tlie temperature also increases a little at first, 

 but it may also take place then when the temperature decreases 

 immediately. 



We have assumed in all our previous considerations of the equi- 

 librium F -\- F' -\- L -\- G that the four phases have a different 

 composition; now we shall consider the case that two of these phases 

 have the same composition. This will amongst others be the case 

 when F and F' are modifications of the same solid substance or 

 also when F or F' is one of tlie components and \vhen the vapour 

 consists only of this component. This latter is e. g'. the case for the 

 cryohj'dric cnrve nnder its own vapourpressure F -\- Ice -\- L -{- (r 

 when of the three components only the water is volatile and the 

 gasphase contains conseqnently only watervapour. 



Let us first consider the latter case ; we take, therefore, the 

 cryohydric curxe under its own vaponrpressure F -\- Ice -\- L -\- G 

 and we preassume that the gas contains only watervapour. The results, 

 therefore, of course remain also valid, when we replace the ice by 

 another component. Now we must equate in our previous consider- 

 ations «' = 0, /?' = 0, ,r, =: and ?/, =r= ; from this follows: F z=. 

 utj — jS.t' and E^ = 0, from (6) follows \^^x = V x — v' and H^x^= FI^~ ->/. 

 Now it follows from (10) : 



^^//^^/A^ 



dT F,., l\ —v' ^ ^ 



Herein H^ and I", represent the entropy and the volnme of the 

 gas, therefore of the waterxapour ; ?/ and r' are the entropy and 



the volume of" the ice. From this follows, therefore, that — is the 



(IT 



same for the ternaiT equilibrium A -j- /ce -)-/_> -|- G and for the 



nnary equilibrium fee -[- watervajiour. This i,s evident, also witliout 



calculation; removing viz. from the ternary equilibrium F -{- Ice -{- 



L -f- (jT the solid substance F and the licpiid L, we retain, as (i 



consists only of watervapour, the unary equilibrium ice-\- waterv^apour. 



If we imagine the sublimationcurve of the ice and the cryohydric 

 curve F -\- ice -\- L -\- (r to be drawn in a /^, 7^-diagram the two 

 curves must, therefore, coincide. As the first curve is experimentally 

 known, we know, therefore, also the curve F -\- ice -\- L -\- G. 



A cryohydric cur\'e under constant pressure (consequently the 

 equilibrium F -\- ice -\- L) has in the c-oncentrationdiagram the point 

 of maximumtemperature in its point of intersection with the line, 

 which joins the two solid phases F and ice. This is also the case 



