41 fi 



Chemistry. — "The Te mper-ahire-co efficients of the free Surface- 

 ener(jy of Liquids, at Temperatures from — 80° to 1650° C: 

 VI. General Remarks'. By Prof. Dr. F. M. Jaeger. (Commu- 

 nicated by Prof P. Romburgh). 



§ 1. If we wish to use the results up to now obtained in the 

 study of these more than seventy organic and about ten inorganic 

 liquids, to draw some more general conclusions, the following remarks 

 in this respect may find a place here. 



In the first place it is proved once more, that the free surface- 

 energy of liquids, — also in the peculiar case of the elect rolytically 

 conductimj, molten salts studied at very high temperatures, — ahoays 

 decreases with increasing temperature. This fact, an exception to 

 which also within the temperature-interval hitherto investigated 

 has never been stated, must be esteemed in every respect quite in 

 concordance with the views about the origin of such surface- 

 tensions. It is immediately connected with the other fact, that 

 a decrease of the molecular surface-layer must be accompanied 

 b}' a \ieat-evolutio?i, an increase of that layer however with a heat- 

 absorption, if the temperature is to remain constant. Furthermore 

 this gradual diminution of / with increasing temperature is in full 

 agreement with the continual levelling of the diiferences in properties 

 between the liquid phase and its coexistent vapour, when the 

 temperature is gradually rising: at the critical temperature the value 

 of X must have become zero ^). 



Of more importance for our purposes however are the following 

 results : 



I. A linear dependence of x and t appears in general not to exist, 

 j^j The observations prove the possibility 



of all the three imaginable principal spe- 

 cies of x-^-curves : the type 1, with a 

 concave shape towards the temperature- 

 axis ; the type 3 with a shape convex to 

 that axis; and the rectilinear type 2. 

 Besides there are found some rare cases 

 of combinations of these three principal 

 types. Characteristic for type N". 1 is, 



d'A . ... 



that — ' will increase with rising tempe- 



dt 



. rature, while it decreases under those 



circumstances on the curves of type 3; 



1) The critical temperatures of the studied liquids, are as far as known, in the 

 diagrams indicated between ( ), behind the names of the different subsslances. 



