6Q 



Drs. Ramsay and Young on the Influence 



single determination at the boiling-point, 80°* 35, at a pressure 

 of 765-1 millim., is 93*4 to 93-5 calories. 



2. Heats of Fusion of Solid Benzene. — Peterson and Wid- 

 mann (J. prakt. Chem. xxiv. p. 129) give the number 29*09 

 calories ; and Fischer (loc. cit.) found 30*085 calories. 



3. Specific Heat of Liquid Benzene. — This has been often 

 observed. But isolated observations are for our purpose 

 comparatively valueless, for the specific heat varies with the 

 temperature. Formulae are given only by Schiiller (Pogg. 

 Ann., Erganzungs-Band, p. 5), and by SchifY (loc. cit.). We 

 have used SchifPs formula. It is, specific heat = a -f bt ; where 

 a= 0*3834 and b = 0*001043. Between narrow limits of tem- 

 perature this may be accepted as sufficiently correct. 



4. Specific Heat of Solid Benzene. — Fischer (loc. cit.) gives 

 0*319. 



Calculating the heat of vaporization at the boiling-point 

 under normal pressure from Regnault's total heats of volatili- 

 zation and Schiff *s specific heat of liquid benzene, the number 

 93*67 is obtained; while SchifF found by direct measurement 

 93*4 to 93*5. This is a strong presumption in favour of the 

 correctness of the data. 



The mean of the two determinations of the heats of fusion 

 of benzene was taken. 



The following Table summarizes the data for calculating 

 the vapour-pressures of the solid. But this calculation in- 

 volves the assumption that the heat evolved on solidification 

 at any low temperature is equal to that evolved at the ordinary 

 melting-point, minus the product of the specific heat of the 

 solid into the difference of temperature ; and that the specific 

 volume of the vapour in contact with solid is equal to that of 

 vapour in contact with liquid. It is certain that neither of 

 these assumptions is true ; hence it is not legitimate to calcu- 

 late the vapour-pressures of the solid from those of the liquid. 

 Still, for some degrees below the melting-point, the error 

 involved in these assumptions is probably not very great. 



Temp. 



P'. 



P'*-P'*-i. 



Yt-i. 



Fe-i. 



Yt-i 



P,-iV-i. 



P. 



o 



mm. 



mm. 



calor. 



calor. 







mm. 



5-58 



35-89 



1-86 



108-3 



29-4 



1-271 



2-365 



35-89 



4-58 



3403 



1-78 



108-4 



29-1 



1-268 



2-258 



33-52 



3-58 



3225 



1-69 



108-5 



28-8 



1-265 



2139 



31-27 



2-58 



30-56 



1-62 



108-6 



28-5 



1-262 



2-045 



2913 



1-58 



28-94 



1-54 



308-8 



28-2 



1-260 



1-941 



27-08 



0-58 



27-40 













25-14 



