SYSTEM NAPHTHALENE-CHLOEOBEXZEXE-PHENOL, ETC. 29 



and fell again slowly. This maximum temperature was read, 

 and the composition of the liquid phase corresponding to it \Yas 

 calculated in the following manner. 



To make the procedure clear let us suppose that the eutectic 

 point, or more properly the point on the eutectic line, had been 

 reached by cooling along the fusion curve of naphthalene. The 

 projection of this curve on the plane of composition is represented 

 by a straight line passing through the apex JV and the point 



P 



P+C 



Y= ^.-^, 



on the line CF. But the fusion curve was displaced somewhat 

 owing to the separation of a small quantity of phenol as the 

 second solid phase. In order to estimate this amount JP it is 

 necessary to know the quantity of heat required to heat the 

 system from t—Jt to t, and also the heat lost by radiation 

 during the rise of temperature. The latter can be estimated 

 from the rate of cooling, which for this duration amounted to Jt'. 

 The former amount of heat is again the sum of two heat quanti- 

 ties, viz., first the heat required simply to elevate the temperature 

 of the system ; and second the heat absorbed by the dissolution 

 of a small amount of naphthalene, because with the rise of 

 temperature the concentration of naphthalene in the solution must 

 again increase. Now the quantity so dissolved is 



at 

 l — x dt 



lx_ 



■U 



curve, if necessary by exterpolation ; hence JN can be estimated 



(It 



The value of x and ,\- at t can be determined from the fusion 



(it 



