416 Prof. G. Quincke on the Edge-angle and 



That the phenomena produced by the same liquids may 

 change with the nature of the solid substance follows from 

 the researches of Chevreul*,in which, when air was excluded, 

 olive-oil was driven away by water in porous porcelain, while 

 in porous whitelead water was driven away by olive-oil. 



This circumstance is therefore worthy of notice, since it 

 has often been said that fluids with a lesser capillary constant, 

 or tension of the free surface, drove away from solid bodies 

 the fluids with a greater capillary constant of the free surface. 

 If the fluids are brought into contact with the air, besides 

 being brought into contact with one another and with the 

 solid substance, then indeed the water is driven away by most 

 of the fluids 2 with which the researches recited above were 

 conducted; and I have already previously completely dis- 

 cussed | the cause of this phenomenon. Hence it follows 

 that the contact of air with fluids 2 and 3, which are in con- 

 tact with a solid body 1, may promote or initiate the driving 

 away of fluid 3 by fluid 2 from the surface of a solid body, 

 when once « 2 < a 3> an d in consequence the sum of the surface- 

 tensions a minimum %. 



This remark appears to me to be of importance for the 

 comprehension of the influence of the air, or of gases generally, 

 upon the processes of diffusion in the nourishment of plants 

 and animals, and in the influence upon the digestion of drinks 

 containing carbonic acid. 



If two fluids, which are mutually miscible in all proportions, 

 come into contact with the same solid body (with glass in the 

 present case) simultaneously, without access of air, there can 

 be no surface-tension at the surface of contact of the two 

 fluids, and the fluid of the lesser surface-tension a 12 of the 

 common boundary with the glass must drive away from the 

 solid body the fluid with the greater surface-tension. 



According to the figures of Tables VIII. and IX., water 

 must therefore drive away alcohol from a surface of glass. 

 This is in harmony with experience, since burnt clay and 

 quartz-sand, which behave similarly to glass, deprive aqueous 

 alcohol of water, as Wagenmann and I have found § . 



According to Table IX. turpentine must drive olive-oil 



* Comptes Hendus, lxiii. p. 63 (1866). 



t ~P ogg. Ann. cxxxix. p. 58 (1870); and Phil. Mag. June 1871, pp. 

 466-9. 



X Pogg. Ann. cxxxix. p. 61 (1870); and Phil. Mag. June 1871, 

 p. 471. 



§ Pogg. Ann. ex. p. 61 (1860). Compare also W. Schmidt, Pogg. 

 Ann. xcix. p. -370 (1856), and Duclaux, Ann. de Chim. et Phys. (4) xxv 

 p. 486 (1875). 



