﻿464 M. G. Quincke on the Capillary Phenomena 



common surface of mercury and water, and the diameter of the 

 drop increases. 



The motion of the particle of liquid on the surface of mercury 

 is considerably diminished by a thin layer of liquid which covers 

 the surface of the mercury. 



Lens-shaped drops of water and hyposulphite of soda with 

 angles of different magnitudes can swim simultaneously on a 

 surface (impure) of mercury. 



The thin layer of liquid with which an apparently pure surface 

 of mercury is covered may differ in thickness and in nature in 

 different places. The lens-shaped drops of water have then dif- 

 ferent angles on the different portions of the mercury surface. 



If by breathing on the surface of the mercury many such 

 lens-shaped drops of equal magnitude are produced, then the 

 places with equal and those with different angles are easily re- 

 cognized. A so-called Moserian figure {Hauchbild) is seen. To 

 the Moserian figures produced in a similar manner on solid sub- 

 stances, such as glass or metal plates, amongst which are to be 

 included the images (Daguerreotypes) generated on insolated 

 plates of iodide of silver by drops of mercury, I shall recur on 

 another occasion. 



Petroleum, alcohol, and ether produce phenomena similar to 

 fatty and volatile oils. Instead of placing the easily vaporized 

 liquids directly on the surface of mercury, it is frequently suffi- 

 cient to vaporize a drop of the liquid in question in the neigh- 

 bourhood of the surface of mercury and to allow the vapour to 

 be condensed, which then spreads itself out on the surface of the 

 mercury as a coherent layer, and gives rise to the movements or 

 changes in form of the lens-shaped drops of water on the mercury 

 in the manner described. 



The effect of the thin layers of liquid on the surface of water 

 and of mercury reaches a maximum when the thickness exceeds 

 a magnitude 21, — that is, twice the distance at which the mole- 

 cular forces of capillarity are still effective. By observing the 

 maximum effect which a measured quantity of liquid produces 

 on a surface of mercury of known magnitude, the magnitude 21 

 can therefore be determined. I shall take an opportunity of re- 

 turning to this. 



In the experiments described in § 8 on drops of mercury in 

 different liquids, a trifling impurity in the mercury has but little 

 disturbing influence, because the surrounding liquid 2 (for ex- 

 ample, the water in which the drop of mercury lies) has a 

 greater volume, and removes the impurity by dissolving it. The 

 determination of the capillary constant a 12 refers, therefore, to 

 the surface of contact of, at all events, approximately pure mercury 

 and water. 



