Phenomena of the Capillary Electroscope. 



93 



In order to test in a more searching manner whether during the 

 passage of an electric current movements occur at the boundary 

 surfaces of two liquids which are miscible with each other, similar to 

 those which take place at the mutual surfaces of a liquid metal and 

 electrolyte ; and also to ascertain whether any translation of the mass 

 of an aqueous solution occurred similar to the bodily movement of 

 the mercury, I employed the following apparatus (see fig. 1). 



A is a thick glass cup about 4 centims. wide and 10 centims. high, 

 having an accurately and tightly-fitting horizontal division of gutta- 

 percha B ; also a similarly well-fitting vertical one C. D and E are 

 electrodes of sheet platinum. F and Gr are thin glass tubes about 

 10 millims. high, and 3 millims. diameter, open at both ends, and fixed 

 liquid- tight in holes in B. H is a plug of beeswax. 



In preparing to use this apparatus, the division B was first fixed in 

 water-tight, the space below it filled with a nearly saturated aqueous 

 solution of cupric nitrate, and the plug H inserted ; the height of liquid 

 being adjusted so as to be about half way up the glass tubes. Corks 

 fixed upon the ends of platinum wire were now placed in the tubes. 

 The glass vessel was then nearly filled with a mixture (at 60° F.) of one 

 measure of sulphuric acid and 10 of water ; the electrodes immersed ; 

 the division C inserted and made as water-tight as possible ; and the 

 corks removed very carefully. 



An electric current from a single series of five or six Grove's 

 elements of one pint capacity each being now passed through the 

 liquids, the cupric solution appeared to descend slowly in one tube, 

 and ascend in the other, moving in the same direction as the positive 

 electricity, and occupying a period varying from fi^e to twenty 

 minutes for the movement. As the phenomena observed in this 

 kind of experiment were considerably different from those observed 

 with mercury in capillary tubes, I have made a separate examination 

 of them under the title of " The Influence of Voltaic Currents on the 

 Diffusion of Liquids" (" Proc. Roy. Soc," vol. 31, p. 250). As also 

 I could not readily obtain definite lines of separation of two miscible 

 liquids in tubes of as small a diameter as those employed with 

 mercury, I have been unable to solve as satisfactorily as I could have 

 wished the question whether perfect immiscibility of the liquids is 

 a necessary condition of the movements of the mercury in such ex- 

 periments ; Herschel stated ("Phil. Trans.," 1824, p. 189) that it is. 



5. Relation of the Movements to the Volume and Specific Gravity of the 



Mercury. 



In order to ascertain whether the whole of the mercurial column 

 moved in the direction of the motion of the meniscus, or expanded and 

 contracted coincident with the advance and retreat of that surface, I 



