Capillary Attraction exhibited by Chloroform^ Sfc. 43 



the liquids. Even although this reasoning be not considered 

 sufficient to prove the perfect equality of the attractions of the 

 liquids for each other, yet if they be only nearly equal, their 

 resultant will still evidently act in opposition to the attraction 

 of the containing wall. And it obviously follows from this, 

 that the stronger the mutual attraction of the fluids, the less 

 will be the effective attraction of the walls of the vessel. We 

 have next then to consider the curvature of the surface of the 

 liquids as depending upon the resultant of the attractions of 

 the walls of the vessel, and the attractions of the particles of 

 each liquid among themselves. Now Clairaut has shown, 

 that when the attraction of the walls of the vessel is more than 

 half that of the molecules of the liquid for each other, it will 

 rise towards the solid ; and therefore the greater the excess 

 of the attractive power of the solid above this limit, the greater 

 will be the rise of the liquid, and the extent of the curvature 

 of its surface. The effect of the mutual attraction of the liquids 

 in diminishing the attraction of the walls of the vessel will 

 therefore evidently tend to reduce the curvature within nar- 

 rower limits, and thus to produce a flat surface. In other 

 words, the greater the mutual attraction of the liquids, the less 

 will be the effective attraction of the walls of the vessel ; and, 

 consequently, the smaller will be the tendency to curvature 

 due to the superior attraction of the solid for one liquid over 

 the other, enabling it to insinuate itself between the walls of 

 the vessel and the other liquid. 



It was already observed, that the effect of potash in flatten- 

 ing the surface of chloroform does not consist in the absolute 

 removal of its curvature, but only in reducing it within very 

 narrow limits; and this is precisely what might be expected ; 

 for while the mutual attraction of the liquids counteracts 

 their attractions to the walls of the vessel, it cannot remove 

 any previous inequality between those attractions. The most 

 wetting liquid will therefore still rise towards the solid ; but 

 the effective attraction being diminished, it will rise to a smaller 

 extent, and the curvature will thus be reduced within much 

 narrower limits than if there had been no force to counteract 

 the attraction to the solid. The attraction of the liquids is 

 also an obvious explanation of the flattening of the surface of 

 chloroform, observed by Dr. Wilson, where it is not in con- 

 tact with the walls of the vessel; and it likewise accounts for 

 the diffuse and irregular form of the globules of chloroform in 

 alkaline solutions observed by him. For it is evident that the 

 attraction of the potash must counteract that of the particles 

 of the chloroform for each other, and thus render it virtually 



