INTRODUCTION. 5 



cent mixture, the value of the molecular conductivities declining rapidly, however, 

 to the figures for pure acetone. The curves for mixtures of methyl and ethyl 

 alcohols are nearly straight lines, following the fluidity curves; and maxima are found 

 in the acetone-alcohol curves. 



The investigation was extended by McMaster 1 to a study of lithium bromide and 

 cobalt chloride. The former behaved normally in all the mixtures of the alcohols 

 and water; that is to say, a minimum was noticed in the conductivity curves at 

 and 25 in mixtures of the alcohols with water, while the results for mixtures of the 

 two alcohols obeyed the law of averages almost exactly. In mixtures containing 

 acetone, relations were found very closely analogous to those obtained by Bingham 

 in the case of lithium nitrate. The solutions in alcohol-acetone gave maxima of 

 conductivity in the 75 per cent acetone mixture; while the solutions in water gave 

 minima at the higher dilutions and inflection points at the lower dilutions. The 

 unusual behavior of the acetone mixtures is here again very evident. 



Cobalt chloride, on the other hand, gave unexpected results. In the first place, 

 the conductivity of its solutions in ethyl alcohol is surprisingly low, being only about 

 15 per cent as great as in water. In mixtures of ethyl alcohol and water, cobalt 

 chloride gave an inflection point in nearly all the solutions, but in the curves for 

 F = 200 to V= 1,600, at 0, the value of /jl v is greater in the 75 per cent than in the 

 50 per cent mixture, thereafter declining to the lower values in pure ethyl alcohol. 

 Exactly the same phenomenon is shown by calcium nitrate in acetone-water solu- 

 tions, where the curves rise from the 50 per cent to the 75 per cent mixture, and drop 

 off rapidly in pure acetone. Rouiller found similar results for silver nitrate. In 

 solutions of methyl alcohol and water, cobalt chloride is normal, giving pronounced 

 minima in the 50 or 75 per cent mixtures. Methyl alcohol-ethyl alcohol solutions 

 gave nearly straight lines, as did also solutions in acetone-methyl alcohol. In the last 

 cases the fluidity curves are also nearly straight lines, but the acetone-methyl alcohol 

 conductivity curves have a slope which is the reverse of the fluidity curve. Acetone 

 and ethyl alcohol gave a maximum in the 25 per cent mixture. 



In most of the above cases we see that the conductivity varies directly as the 

 fluidity, and fluidity minima are usually accompanied by conductivity minima. The 

 converse, that conductivity minima were accompanied by fluidity minima, was not 

 always found to be true, as, for instance, with cobalt chloride in acetone-ethyl 

 alcohol. Here a maximum of conductivity is found in mixtures giving a fluidity 

 curve which differs by less than experimental error from a straight line. Again, the 

 conductivity curves for acetone-water show inflection-points, while the fluidity curve 

 has a minimum. These apparently irregular results are to be considered again in 

 the work of Jones and Mahin. 



In explanation of the minimum of conductivity, Jones and McMaster adopt the 

 view that the diminution in the fluidity of the solvent is an important factor in 

 determining the conductivity minimum. But this does not account entirely for 

 the phenomenon. The change in the size of the ionic sphere, the atmosphere sur- 

 rounding the ion, must also be considered. The velocity of the ion depends not only 

 on its composition, but also on its attraction for the solvent. 



'Amer. Chem. Journ., 36, 325 (1900). 



