68 



Dr. G. Gore. 



surfaces of mutual contact of the liquids, various phenomena, such as 

 layers of liquid of different specific gravities and adhesive powers, 

 lines, layers of colour, alterations of forms of meniscus, downward 

 liquid currents, &c, are produced. That also by the heat of con- 

 duction resistance evolved in the tubes in consequence of the reduced 

 area of section of the solutions ; by the surfaces of the layers of liquid 

 acting as electrodes ; and by the chemical union of acids and bases set 

 free in contact with each other at the meniscuses, thermic expansion and 

 streaming upwards of liquids, &c, are produced. In order to be able 

 to understand the results of each separate experiment, these and the 

 subsequent explanations require to be applied to the particular case. 



The apparent transfer of mass may be partly explained upon the 

 assumption that the colouring matter acts as a base towards acids, 

 and as an acid towards bases, and is transferred accordingly, thus 

 producing in the former case, b}^ diminution of colour at the negative 

 and increase of it at the positive end, an appearance of bodily transfer 

 of the heavier liquid in the direction of the current. Others may be 

 explained upon the supposition that basic matter is set free at the 

 liquid cathodes, and acid matter at the liquid anodes ; thus, with the 

 lower liquid containing a salt (such as cupric sulphate) composed of 

 a coloured base and a colourless acid, the blue basic matter accumu- 

 lated at the liquid cathode, and the colourless acid at the liquid 

 anode, and the liquid appeared to move in the direction of the 

 current ; but with one containing a salt (such as potassic chromate) 

 composed of a coloured acid and a colourless base, a reverse move- 

 ment appeared to occur. 



The downward movement of the meniscus under the cathode which 

 occurs in some cases (see Experiments 41, 42, and 43), may probably 

 be explained as follows : — By the upward passage of the electric 

 current and the meniscus acting as a kind of diaphragm, a greater 

 volume of liquid was transferred by electric diffusion from the 

 negative to the positive side of the division than in the reverse 

 direction (see "Experiments on Electric Osmose," " Proc. Roy. Soc," 

 No. 208, 1880, vol. 31, p. 253). This explanation, however, does not 

 appear very consistent with the fact that the lines when first observed 

 are not usually close to the coloured surface of the true meniscus, and 

 do not separate farther from it by continuance of the current. 



The influence of chemical composition of the liquids upon the 

 formation of lines is illustrated on page 85. The greater the differ- 

 ences of specific gravity of the two liquids, the more easily were the 

 lines produced. The line occurs more frequently where the current 

 goes from concentrated to dilute solutions of different substances than 

 the reverse ; out of 42 lines, 28 were at the positive, and 14 at the nega- 

 tive meniscus. The definiteness of the lines where the current passes 

 upwards, and the indefiniteness usually produced where it passes 



