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XLVIIL Latent Heats of Fusion. — Part I. Benzophenone> 

 Phenol, and Sulphur. By Mrs. K. Stratton, M.Sc, and 

 Prof. J. E. Partington, D.Sc* 



rt^HE determination o£ the latent heat of fusion of a 

 I substance has been carried out in one of two ways : — 

 (1) Calorimetrically, (2) Indirectly from van't HofPs 

 equation: E = 0'02T 2 /L, where E = molecular depression of 

 the freezing-point for 100 grams of solvent ; L = latent 

 heat of fusion of substance in gram calories per gram ; 

 T = melting-point (absolute). 



No systematic investigation of Latent Heats of Fusion 

 seems to have been made ; the nearest approach is a classical 

 research of J. F. Eykmann f, to which frequent reference is 

 made by later experimenters. Eykmann's results, however, 

 were all found indirectly from the Molecular Depressions of 

 Freezing Point by means of van't Hoff's equation, and an 

 inspection of some series of values reveals very large dis- 

 crepancies between different experiments. These apparently 

 can be explained only on the assumption that the materials 

 used were not pure, or that the errors of experiment were 

 unduly large. The first supposition is confirmed by 

 Eykmann's results for phenol. Two samples of phenol were 

 used, the melting-points being given as 36° C. and 39° C. 

 respectively, whilst the melting-point of pure phenol we 

 find to be 41°*5 C. In no case does Eykmann discuss in 

 detail the purity of his -materials, . and it can hardly be 

 questioned that the whole of his results fall far short of the 

 accuracy which may be attained. This method, apart from 

 its indirect character, did not appear to us suitable for the 

 object we had in view. It is also not at all certain that the 

 addition of a second substance may not modify, to an 

 unknown extent, the molecular constitution of the first in 

 the liquid state. A comparison of the values of the latent 

 heat determined, with the same degree of accuracy, by the 

 direct and indirect methods is expected to throw light on 

 this question. 



The direct calorimetric methods, as applied by former 

 experimenters J, although simple in execution, involve a 

 knowledge of additional data which is not always available. 

 Apart from the somewhat large cooling corrections for the 

 calorimeter, it is necessary to know the specific heats of the 



* Communicated by the Authors. 

 t Zeitschr. physikal. Chem. iv. p. 497 (1889). 



X Person, Annates de Chimie, xxx. p. 73 (1850) ; Brunei-, Ber. vol. xi.. 

 p. 2102 (1894) ; Battelli, Att. Accad. Lincei, p. 621 (1885). 



