﻿470 M. G. Quincke on the Capillary Phenomena 



a 23 <a 2 — a 3 , and produces currents in the interior of liquid 2, 

 and rolls off, as it were, the thin layer of liquid 2 from the sur- 

 face of liquid 1. Hereby liquid 3 comes into contact with liquid 

 1 j and it now depends on the magnitudes a 2 , ct 3 , ct l<2t a 23 , and 

 a 31 whether or not liquid 3 drives liquid 2 from the surface of 

 liquid 1. 



Moreover the more or less unknown friction of the particles of 

 liquid against one another plays a part in this complicated process. 



Hence it is entirely false to say that as soon as « 2 >a 3 , liquid 

 3 drives away liquid 2. Thus, for example, olive-oil (« 3 =3*76 

 milligrms.) drives the alcohol (a 2 = 2*599 milligrms.) from a 

 surface of mercury upon which two drops of these liquids are 

 placed together, although a 3 >« 2 . The reason is, that for mer- 

 cury and olive-oil a l3 =34*19 milligrm., for mercury and alcohol 

 a 12 = 40*71 milligrms., hence in the latter case is considerably 

 greater. a 23 = 0*226 milligrm. for alcohol and olive-oil has, on 

 account of its smallness, only a slight influence in this pheno- 

 menon. 



For the case in which the capillary constant of the common 

 surfaces can be neglected (that is, when the liquids brought 

 together are miscible in every proportion, or the a with double 

 index are small), the liquid with small capillary constant of the 

 free surface will certainly drive away the liquid with greater ca- 

 pillary constant. 



If liquids miscible in all proportions be so arranged that each 

 one following spreads out on the free surface of the foregoing, then 

 the same series will be obtained as if the liquids were arranged ac- 

 cording to the magnitudes of their capillary constants*. 



The foregoing consideration also holds good for the case in 

 which a solid body 1 is substituted for liquid 1. Although the 

 mobility of the particles of the liquid in contact with this solid 

 body 1 is materially diminished, we must nevertheless, as I shall 

 more closely argue presently, attribute a definite surface-ten- 

 sion to the liquid in contact with the surface of the solid body. 



* Frankenheim (Theory of Cohesion, p. 142, 1835) has already re- 

 marked that the intensity with which a drop of liquid strives to spread 

 itself out is greater in proportion as the specific cohesion of the liquid in 

 question is less. Although, further on, he ascribes to the formation of va- 

 pour an influence on the spreading, still he appears to have had a correct, 

 if not in many points a clear conception of this phenomenon. 



More recently Liidtge (Pogg. Ann. vol. cxxxvii. p. 377s subject 4 to 6) 

 has enunciated the general law for any liquids, that the series of liquids ar- 

 ranged according to the magnitude of their capillary constants agrees with 

 the order in which the liquids spread — and has at the same time stated 

 " that the spreading takes place more distinctly the less the miscibility of 

 two liquids and the greater the difference of their cohesions." But as « 12 

 appears to be less the more readily liquids 1 and 2 mix together, this state- 

 ment is in contradiction to equation (4) § 25 of this memoir. The series 

 only agree with one another in the case of the most perfect miscibility. 



