405 



Resorcine-Dimethylether. 



dn 

 Temperature- interval : -— m Erg: 



between 



-22° and 0° 

 0° „ 210° 



2,83 

 2,25 



Hydrochinon-Dimethylether. 

 Temperature- in terval : 



dft 



^ in Erg: 



between 66° and 106' 2,11 



106° „ 166° 2,46 



166° „ 206° 2,88 



Up to 166°, this y-^curve coincides 



practically with that of guajacol and of 



resorcine-dimethylether. 



§ 5. Also for these substances one can state, that a decom- 

 position of the compound causes an extraordinarily rapid decrease 



of the values for / or n with increasing temperature 



0/ 



becomes 



much larger in such cases with rising temperature. Furthermore it 

 can be seen from the cases of salol, dielhylbenzyJmnloiiatp, resorcine- 

 inonometliylether, etc., that an extraordinarily great viscosity of the 

 liquid can appreciably diminish the accuracy of the measurements; 

 however the case of dimi'thyltartrate on tlie contrary proves, that 

 sometimes reliable results can be obtained, even with very high 

 values of the internal friction. 



Gronimjen, June 1914. Laboratory Inorganic Chemistry 



of the University. 



Chemistry. — '-The Temperature-coefficients of the free Surface^ 

 enen/y of Liquids, at Temperatures from — 80° to 1650° C: 

 V. Mea.mrements of homologous Aromatic Hydrocarbons and 

 some of their HaIo(/enderivatives'\By Prof. Dr. F. M. Jaegkr. 

 (Communicated by Prof. P. van Roxburgh.) 



§ 1. In order to answer also the question of an eventual depend- 

 ence between the chemical constitution of liquids and the values 

 of their free surface-energv and of its temperature-coefficient, in 



27 



Proceedings Royal Acad. Amsterdam. Vol. XVII, 



