28 THE MECHANISM OF LIFE 



containing n molecules, each of which is composed of A: ions. 

 Then if a is the degree of dissociation, 



n' = n — an+ank, 

 n' = n [1+rt (A--l)l 



'i' = l+a (A-l) = j. 

 a 



We thus obtain i the coefficient of dissociation, in terms 

 of the degree of dissociation a and the number of ions in 

 each molecule k. 



If there is no dissociation, i.e. if u = i), then n'=n, and 

 j = l. If all the molecules are dissociated, a = 1, and ? = A: 



Faraday's Law. — Faraday found that the quantity of 

 electricity required to liberate one gramme-molecule of any 

 radical is 96"537 coulombs for each valency of the radical. 



Electrochemical Equivalent. — The electrochemical equivalent 

 of a radical is the weight liberated by one coulomb of electricity. 

 It is equal to the molecular weight of the ion, divided by 

 96'537 times its valency. 



Electrolytic Conductivity. — The conductivity of an electro- 



lyte is the inverse of its resistance. C= —. 

 J \\ 



For a given difference of potential the conductivity of 

 an electrolyte is proportional to the number of ions in unit 

 volume, the electrical charge on each ion, and the velocity of 

 the ions. 



The specific conductivity A of an electrolyte is the 

 conductivity of a cube of the solution, each face of which is 

 one square centimetre in area. The molecular conductivity of 

 an electrolyte is the conductivity of a solution containing one 

 gramme-molecule of the substance placed between two parallel 

 conducting plates, one centimetre apart. The molecular 

 conductivity is independent of the volume occupied by the 

 gramme-molecule of the solute, depending only on the degree 

 of dissociation. The molecular conductivity V is equal to the 

 product of V, the volume of the molecule, by A. its specific 



conductivity. U = YA. Whence A= , i.e. the specific 



