250 THE REALITIES OF MODERN SCIENCE 



tion of the solvent, in pursuing their haphazard motions 

 through the liquid have but a negligible chance of col- 

 liding with ions of the opposite electrical sign. On the 

 other hand, if the dilution is not infinite there will 

 be collisions between ions of opposite sign, and hence 

 at any instant a number of recombinations are taking 

 place. Of course, a similar number of molecules are 

 dissociating at this instant or otherwise the solution 

 would be changing in its ionization. The number of 

 molecules of the solute is increased if the concentration 

 is increased. Unless therefore the dissociation a de- 

 creases proportionately, the total number of ions 

 available for transferring electricity will also increase. 

 There will be a higher conductivity, as concentration 

 increases, until a point is reached where the dissociation 

 decreases equally. Then, for further increases in con- 

 centration the dissociation decreases even more rapidly, 

 resulting finally in a solution of essentially zero dis- 

 sociation and hence negligible conductivity. 



The value of a may be determined from measure- 

 ments of the conductivity, or more strictly the molecu- 

 lar conductivity, which is the ratio of the conductivity 

 to the concentration. The molecular conductivity is, 

 then, an actual conductivity of the solute molecules 

 and changes only as these molecules change by dis- 

 sociation. Represent it by L and let K be the factor of 

 proportionality. Then L = Ka. Calling the maximum 

 value Loo corresponding to the dissociation o=l, 

 we have K = Loo. Hence the dissociation, a, corre- 

 sponding to any observed molecular conductivity, 

 L, is 



(2) 



