349 



repeated loweriiij;' of tlie capillary lube over known distanees by 

 means of the micrometer-screw JS/ (tig. od), and by repeating- tlie 

 readings of tlie manometer in every case. 



In all calculations we used the number 1333.2 Dynes as the 

 equivalent of J m.m. mercury-pressure at 0° C. ; the surface-energy 

 is expressed in Erg pro c.m.\ ^) 



§ 14. As an illustration of the general availability of the method 

 at all temperatures between — 80° C. and -}- 1650^ C, we will give 

 here already some few instances, relating to : loater, some colloidal 

 solutions, some organic liquids, and some molten salts. The specific 

 weights of the organic liquids were, after a pycnometrical control 

 at 25° C, calculated for other temperatures from the thermic expan- 

 sion-formulae, if they were already sufficiently and accurately 

 knowni in litterature. 



In other cases the densities at 'lö"^, 50°, and 75° C were pycnome- 

 trically determined, and a quadratic relation with three constants 

 was calculated from these observations ; this relation was used then 

 afterwards for the determination of tiie other specific weights. In 

 the case of the molten salts the specific weights must again be 

 determined by means of a method to be described later. To use the 

 numbers for the densities with more than three decimals, has no 

 real significance, because the experimental errors are always of an 

 order so as to make the influence of more decimals of no importance. 



^ 15. 



The curve (fig. 8) is evidently concucc- with respect to the tempe- 

 rature-axis ; the temperature-coefficient of j/ is only small, and amounts 

 to from 0,y to 1,05 Erg. per 1° C. 



Furthermore in this diagram the con'esi)onding curves are repro- 

 duced for a colloidal solution of iroit-vxide (XnAïov a colloidal solution 

 of siliciuni-dio.ride ; from both solutions the electrolytes were elimi- 

 nated as far as possible by longer continued dialysation. 



It appears, that both curves are evidently situated somewhat above 

 that for the pure solvent, although the deviations for / from the 

 values for jjure water are only very small. The temperature-coeffi- 

 cients are analogous to those for the solvent itself; however in the 

 case of the colloidal iron-oxyde it could be observed, that if 

 such a solution was heated to a higher temperature, and if afterwards 

 the determination of the surface-energy was repeated at the original 



1) The result is aftei all the same, as wheu expressed in "Dynes pro cm.". 



