'«p,=-è + ^, 



1208 



and 



/nP, = -^,+ C, 



(4) 



From a graphical representation In P^ =zf\{T~^) and biP,=/\{T-'^) 

 the slopes of the two straight lines can then be determined. Then 



the tangent of the angle of inclination amonnts to — 



R 



resp.-- 



The difference mnltiplied by R yields the heat of melting Q, — Q^, 

 which is eqnal here to the energy of melting E, — A\ ^), and from 

 this follows by the aid of equation (1) the value of 7i and with it 

 the composition of the hydi-ate. 



Accordingly for the application of this method of analysis the 

 three-phase lines SSB(jr and *SLtr must be experimentally determined. 



4. The system snlphnretled hydrogen-water presents great analogy 

 with the ideal system of § 3. As was demonstrated in the above- 

 mentioned papers by one of us, a quadruple point *SZ>,Zyj6r appears 

 in this system, indicated in tig. 2 by D. The stable part of the 



Kig. 2. 



three-phase line SL^G, a number of points of which was already deter- 

 mined before"), terminates in the quadruple point SSbL^G, indicated in 



') It appears from the transformations given in § 3 that Qi = £'j -f- RT and 

 Qo = E^-j- RT. as one gramme molecule of gas is formed in both conversions. It 

 follows from this that Q^—Qi = E^ — E^. The volumes of solid and liquid are 

 neglected by the side of these of gas. and the expansion at melting does not 

 cause an appreciable difference between melting energy and heat. 



2) These Proceedings. 13. 829 (1911). 



