RESISTANCE OF ELECTROLYTES. 407 



the resistance of mercury. Foussereau* finds about 3.io 5 ohms for 

 the resistance of ordinary distilled water. The resistance in the 

 solid state is far greater than in the liquid state. The same specimen 

 which in the liquid state had a resistance of 3*231. io 5 ohms, had a 

 resistance of 3*987. io 10 at 0, and of 4*380. io 10 at - 15. 



M. Boutyf has shown that the resistance of any weak solutions 

 follows a very simple law ; the conductivity is the same for solutions 

 which contain weights of salts proportional to the chemical equiva- 

 lents ; in other words, the molecular conductivity is the same for all 

 the salts. The equivalents which satisfy this law are those which 

 are determined by electrolysis that is to say, electrochemical 

 equivalents properly so called. M. Bouty's law should be considered 

 as a limiting case, the phenomena becoming more complicated when 

 the solution contains more than a few millionths of its weight of 

 salts. 



The resistance of all solutions, and especially of electrolytes, 

 diminishes when the temperature increases ; the conductivity c may 

 be represented by an expression of the form 



1004. Wiedemann,J considering the resistance of an electrolyte 

 as due to the material transport of the elements of the salt through 

 the mass of the solvent, investigated if there were no relation 

 between the electrical resistance and the internal friction of a 

 liquid. 



Let us suppose that a liquid moves parallel to a fixed plane, the 

 velocity of a point being a function f (r) of its distance from the 

 plane. Two infinitely near slices, parallel to the plane, and at 

 distances r and r + dr> exert an action on each other parallel to the 

 motion, proportional to their relative velocity, and equal to f]f'(r} 

 for unit surface, ^ being a constant which depends on the nature of 

 the liquid. 



The constant 77, which is called the coefficient of internal friction, 

 may be deduced from experiments relative to the flow of liquids in 

 capillary tubes. Poiseuille has shown that, if D is the diameter of 



* FOUSSEREAU. Ann. de Chim. et de Phys. [6], Vol. v., p. 317. 1885. 



t BOUTY. Ann. de Chim. et de Phys. [6], Vol. ill., p. 433. 1884. 



J WIEDEMANN. Fogg. Ann., Vol. xcix., p. 228. 1856. Die Lehre von der 

 Elekt., Vol. ii., p. 946. 



POISEUILLE. Mem. des Sav. Etrang., Vol. xi., p. 433. Ann. de Chim. et 

 de. Phys. [3], Vol. vii., p. 50. 1843. 



