330 



A probable relaiion ibiiiideJ upon the law of corresponding states, 

 between the value of the temperature-coefficient of the expression: 



x( — ) , and the degree of molecular association of a liquid was 



first suggested by Eötvos '), and later by Ramsay and Shields') and 

 a number of others'). These observations appeared to prove, that 

 the values of these coetncients do not differ much from 2,2 Erg 

 per degree C. for "normal" liquids, while for associated ones they 

 are considerably less. In any event some definite knowledge of the 

 dependence of the free surface-energy -/ upon the temperature will 

 be of high importance for the consideration of all problems, relating 

 to the internal state of liquids. 



It can hardly be supposed with any probability, that the law of 

 corresponding states will be found to apply in the case of molten 

 salts, because they are really electrolytes and more or less dissociated. 

 Notwithstanding this, if the investigation should chance to reveal 

 relations in any way analogous to those hitherto supposed to be 

 characteristic of organic liquids, this fact must carefully be considered 

 in estimating the significance of the theoretical speculations mentioned, 

 and especially is this the case, where criteria are sought forjudging 

 about the molecular state of liquids in general. In fact, one can 

 better hope to elucidate the influence of chemical constitution on 

 characteristic properties in the case of molten salts, than in the case 

 of the much more complicated organic molecules. 



These and other considerations, some years ago (1910) suggested 

 the development') of an experimental method, which should permit 

 the study of the dependence of the molecular surface-energy upon 

 temperature, — even up to temperatures in the vicinity of J650°C. 



1) EöTvös, Wied. Ann. 27. 448. (1886) ; van der Waals, Zeits. f. phys. Gbem. 

 13. 713. (1894). Einstein. Ann. d Phys. 34. 165. (1911) 



2) Ramsay and Shields, Zeits. f. phys. Chemie 12. 433. (1893). 



3) Vid.: GuYE and collaborators, Journ. de Gliim. phys. 5. 81, 97. (J907); 9. 

 505 (1911); etc.; Walden and Swinne, Zeits. f. phys. Ghein. 79, 700. (1912) 

 Bull. Acad. St. Pétersbouig, (1914) 405. 



^) Preliminary experiments of this kind were begun during my stay at the 

 Geophysical Laboratory in Washington, (U. S. A.), in tbe winter 1910-1911, 

 and I wish to express my thanks here once more to my friend Dr. A. L. Day 

 lor his kind assistance and most valuable advice in this matter. Through these 

 preliminary experiments the availability of the method up to 1200° G. was clearly 

 established by me, and it became quite clear, in what directions improvements 

 were necessary. The further development was hindered by the building and equip- 

 ment of the new Ghemical Laboratory of the University of Groningen : not earlier 

 than November 1913 could the first measurements of the present series be made. 



