4 INTRODUCTION. 



drop rapidly to the values in 100 per cent acetone. This fact is important in con- 

 nection with the work of Mahin, to be considered later. Potassium iodide in mix- 

 tures of the alcohols with acetone gave conductivity curves which were very nearly 

 straight lines, either slightly convex or concave towards the axis, denoting percentages 

 of acetone. In mixtures of acetone and water the same salt gave pronounced 

 minima in the neighborhood of the 50 per cent mixtures. Calcium nitrate in mix- 

 tures of methyl and ethyl alcohols with acetone gave curves with maxima at both 

 and 25. In mixtures with water the results were again irregular. In the first 

 place, the values of p, v for calcium nitrate in acetone are surprisingly small, less than 

 those for lithium nitrate or potassium iodide, although it is a ternary electrolyte. 

 In consequence, the curves for acetone-water mixtures, at dilutions greater than 

 F = 400, reach a minimum in the 50 per cent mixture, and rise to the 75 per cent 

 mixtures in this point resembling the curves for potassium iodide but thereafter 

 sink to the small values on the ordinate representing 100 per cent acetone. 



The viscosity measurements brought to light the facts that the fluidity curves 

 of mixtures of the alcohols with acetone are nearly straight lines, while the acetone- 

 water mixtures give a minimum fluidity in the 50 per cent mixture. In general, 

 therefore, the relation found by Jones and Carroll holds for mixtures containing 

 acetone, that is, there exists a parallelism between the conductivity and fluidity 

 curves. However, the maximum conductivity obtained with solutions of calcium 

 and lithium nitrates in mixtures of acetone with the alcohols demands explanation. 

 Two possible causes suggest themselves at once. 



First, there may be an increase in dissociation in the 75 per cent mixtures, where 

 the maximum occurs. Secondly, there may be an increased mobility of the ions, 

 due to a diminution in the size of the ionic spheres. The idea of ionic spheres, pro- 

 posed by Jones, postulates the existence of an atmosphere of solvent molecules 

 clustered about the ion. To decide between these two possibilities, we may first 

 consider the increase in dissociation. The fluidity data show that the acetone- 

 alcohol mixtures are not more associated than the pure solvents; hence, using 

 Dutoit and Aston's hypothesis, we should not expect to find greater dissociation in 

 the mixtures. Moreover, while it is true that the maximum conductivity occurs in 

 the 75 per cent mixture, this is true only for dilute solutions, the maximum shifting 

 to the 25 per cent mixture as the concentration increases. This would not occur 

 if the 75 per cent mixture had the greatest dissociating power. Therefore, the tenta- 

 tive view is accepted, that the maximum in conductivity is due to a change in the 

 dimensions of the ionic spheres, and a consequent increase in migration velocity. 



The conclusion of Dutoit and Friderich, and of Jones and Carroll, that conduc- 

 tivity is proportional to dissociation and inversely proportional to viscosity, must be 

 supplemented by taking into consideration the possible changes in the size of the 

 ionic spheres of solvent molecules. 



Jones and Rouiller 1 undertook the study of silver nitrate. This salt gave results 

 practically identical with those obtained by Jones and Bingham for lithium and 

 calcium nitrates. The conductivity curves for acetone-water mixtures gave inflec- 

 tion-points in the higher concentrations and a pseudo-maximum in the 75 per 



Amer. Chem. Journ., 36, 427 (1906). 



