57 



ciir\e drawn tangential to llie various border ciirxes, touching those 

 in the plait points. 



By plotting T/, the volume of tiie liquid against va a series of 

 curves are obtained wiiich clearly show the process of retrograde 

 condensation in the case of the SO'/» mixture'). 



A peculiarity of the last mixture is that all the lines in this graph 

 go through the point V/, =r half the volume of the small reservoir, 

 which means that the cor'responding line of constant division of 

 volume is a line of constant i^^, therefore in the /^^'.l diagram it 

 runs parallel to the p-axis^). 



If a dj, I graph is drawn, a diametei' is obtained which is 

 rectilinear (ae for a pure substance), but which is strongly curved 

 towards the temperature axis at the extreme end, though in this 

 zone, the position of the point as found must be necessarily rather 

 qualitative than quantitative. 



The plait-point constants were found to be : 



50° , C, Mixture. Ib'j, 0, Mixture. 



fseries XIV. 4.) (series IX. 5.) 



p 41.90 45.89 (observed) 



V,, 0.00358 0.00336 (from p,v^ graph) 



f* — 132°.66 — 125°.60 (observed) 



The critical point of contact constants were found to be: 



(series IX. 4.) (series X. 3). 



p 41.90 45.86 (from p,VA graph) 



v^ 0.00404 0.00375 ifrom d^^t graph) 



— 132°.53 — 125°.53 (observed) 



For the critical point of contact temperature it was found that, 

 at 0.01 of a degree above it no condensation was, of course, observed, 

 and at O.Oi below there was a momentary, but very evident con- 

 densation. 



1) J. E. Verschaffelt. These Proc. I. pg. 288 (Dec. 1898.) Leiden Coram. N". 45. 

 ») Leiden Comm. Suppl. N». 23, p. .M. Enc. Math. Wiss. V 10. 



