498 



Frederick Guthrie on some Thermal and 



together is greater. That 

 the increased expansion 

 is not due to the second 

 of these causes seems 

 proved by the fact that, 

 as the heating is con- 

 tinued, the expansion — 

 although, indeed, always 

 greater than that at 

 temperatures below the 

 separating point — is less 

 than the expansion du- 

 ring separation. Sepa- 

 ration produces some ex- 

 pansion ; and this being 

 superadded to the ex- 

 pansion due to the in- 

 creased temperature of 

 the separated constitu- 

 ents gives rise to the 

 elegant curve of fig. 1. 

 The lower and upper 

 parts of this curve are 

 straight lines at different 

 inclinations to the axis. 

 The region of separation 

 is indicated by a curve 

 tangent to both, and 

 whose mean tangent is 

 more inclined than either 

 to the axis of percentage. 

 Although, therefore, 

 the separation of the 

 mixed liquids into two 

 immiscible liquids (each 

 of which is mixed) is 

 accompanied by an ab- 

 normal volume-change 

 (increase), this increase 

 is not so much larger than 

 the increase attributable 

 to mere heat-dilatation as 

 to make the liquid even 

 at the brink of its critical 

 condition especially va- 

 luable as a calorimeter. 









Fig-. 



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