Trouton — On the Crcc2')in(j of Liquids, etc. 3 



surrounding atmosphere of the more volatile portions of the liquid, 

 and the process is consequently an irreversible one. The condition 

 necessary to enable this influx of energy to produce a directed effect 

 of the kirid required is that the surface-tension of the liquid remaining 

 after the loss of the more volatile constituents shall be greater than 

 before. In this way, as the liquid passes along the strip, its surface 

 tension increases, and more liquid is enabled to be drawn up and 

 ultimately to pass over.^ 



In accordance with this view of the phenomenon, the creeping 

 activity of paraffin should be increased by the addition of any liquid 

 which is more volatile and which has a lower surface tension. The 

 addition of benzoline, ether, and of a number of other liquids, was 

 found to increase the rate of creeping immensely. 



On the other hand, the addition of a more volatile liquid, with a 

 higher surface-tension, which, on mixing with the paraffin, increases 

 its surface-tension, should tend to prevent creeping. Yarious liquids, 

 such as benzene and chloroform, which are more volatile, but have 

 a higher surface-tension, were tried with this view. These were 

 found, however, not to prevent, but to actually increase, the creeping 

 activity. 



On account of these unexpected results, experiments were made 

 with the object of ascertaining the effect produced on the surface- 

 tension of paraffin by the addition of these liquids, and afterward 

 experiments were made with mixtures of various liquids to investi- 

 gate the law of the surface-tension of mixtures in general.^ 



The curve in fig. 2 exhibits the determinations made of the 

 surface-tension of mixtures of paraffin and chloroform; and on 

 examining the curve, the reason becomes obvious why the addition of 

 chloroform does not prevent but rather facilitates the creeping of 

 paraffin, for the value of the surface-tension is there seen to be 

 diminished by tlie addition of small quantities of chloroform. The 

 like was found to hold good for benzene. 



Mixtures, then, of various liquids were examined, and it was 

 invariably found that the surface-tension of a given mixture was 



^ A single liquid might coaceivably creep through a similar gradient in 

 surface-tension, brought about by the cooling due to evaporation alone increasing 

 the surface tension. 



2 Sinoe then the author has had the opportunity, through the courtesy of 

 Prof. W. Ramsay, of consulting a hitherto unpublished paper of his on the 

 surface-tension of mixtures of liquids. 



A2 



