194 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



the conductance curve exhibits a pronounced maximum. The curve for 

 ethyl alcohol mixtures exhibits a pronounced inflection point, while that 

 for water merely exhibits a minimum corresponding to the minimum in 

 the fluidity curve of the mixtures of acetone and water. At the higher 

 concentration, the curve for water initially rises steeply to a very flat 

 maximum and minimum, after which it rises with increasing concentra- 

 tion of water, the curve corresponding roughly to the fluidity curve of the 

 mixtures within the region of these compositions. The conductance of 

 solutions in mixtures of acetone and methyl alcohol rises sharply for 

 initial additions of methyl alcohol, after which it remains practically 

 constant until the axis of the pure methyl alcohol is reached. With ethyl 

 alcohol the conductance likewise increases markedly for the initial addi- 

 tions. Thereafter, the curve passes through a maximum, after which it 

 gradually diminishes to the final value of the conductance in pure ethyl 

 alcohol. It is only in solutions in which the percentage of ethyl alcohol 

 has fallen as low as 25 per cent that the curves begin to approach in form 

 the fluidity curves of the mixtures. For mixtures containing larger 

 amounts of acetone the form of the curve is due largely to the change in 

 the ionization of the electrolyte. On the addition of a second solvent to 

 acetone, the ionization of lithium bromide is greatly increased. In the 

 water mixtures, the viscosity is increased so greatly for small additions 

 of this solvent that the conductance diminishes. In the case of methyl 

 alcohol, however, the fluidity is only slightly reduced by the addition of 

 alcohol and consequently the conductance curve rises initially due to the 

 increased ionization of the salt. At higher concentrations of alcohol, 

 however, the increasing viscosity of the solvent finally makes itself felt 

 and the conductance again falls. At the higher concentration of the salt, 

 the addition of water causes a sufficient increase in the ionization of the 

 electrolyte to overbalance the decrease due to the decreasing fluidity of 

 the mixture. Initially, therefore, the conductance curve for lithium 

 bromide in the mixture increases with the addition of water, passing 

 through a slight maximum, after which the curve approximates the 

 fluidity curve of the solvent. 



As a rule, higher types of salts are ionized to a much smaller extent 

 than are binary electrolytes, particularly the salts of metals which exhibit 

 a pronounced tendency to form solvates with water. In Table LXXIX 

 are given values for the conductance of calcium nitrate in mixtures of 

 acetone with methyl and ethyl alcohols and water. 20 



The relation between the conductance and the composition of these 

 mixtures is shown graphically in Figure 47. It is evident that solutions 

 of calcium nitrate in mixtures containing acetone present a very complex 



*> Jones, Bingham and McMaster, loc. tit., p. 193. 



