DISCUSSION OF THE RESULTS. 



THE CONDUCTIVITY MEASUREMENTS. 



The conductivities of about 110 salts and mineral acids have been measured and 

 the results are herein recorded. These have been studied from about the most con- 

 centrated solution that could be prepared, up to a volume of from 1000 to 4000. The 

 temperature range is from to 65. Salts of nearly all of the more common 

 metals have been included within this Avork. 



It is almost self-evident that in an investigation of this scope certain peculiarities 

 would be presented by some of the substances studied. 



The salts of lithium crystallize with more water than the corresponding salts of the 

 other alkali elements. This means that the lithium ion is more hydrated in aqueous 

 solution than the potassium, sodium, or ammonium ion. The result is that the 

 lithium ion moves more slowly than the other alkali ions, and, consequently, the 

 conductivities of lithium salts are smaller than those of the corresponding salts of 

 sodium and potassium. Before we had the solvate theory it was very difficult to 

 account for the fact that the lithium ion, which has a much smaller mass and smaller 

 atomic volume than either sodium or potassium, should have a smaller velocity. 

 But we now have the explanation of this fact. The larger conductivity of lithium 

 sulphate, especially at high dilutions, as compared with other salts of lithium, is due 

 to this being a ternary electrolyte, while the other three salts are binary electrolytes. 



The salts of sodium with the simpler acids call for no special comment. The con- 

 ductivities are larger than those of the corresponding salts of lithium, since the 

 sodium ion is less hydrated than lithium, and, consequently, moves faster through 

 the solution. Sodium carbonate has very great conductivity, especially at high 

 dilution and elevated temperatures. This is undoubtedly due to large hydrolysis 

 under these conditions. The very large conductivity of disodium phosphate is also 

 probably due to hydrolysis. Sodium ammonium acid phosphate (microcosmic salt) 

 begins, in fairly concentrated solutions, to give off ammonia at 25, and this is still 

 more marked at 35. 



The unusually high conductivity of sodium ferrocyanide, especially at N = 1024 

 and 65, is due in part to the large number of ions yielded by this substance, and in 

 part to hydrolytic dissociation. 



The salts of potassium have somewhat larger conductivity than those of sodium. 

 The potassium ion has less hydrating power than sodium, as is shown by the fact 

 that potassium salts show less tendency to crystallize with water than sodium. Not- 

 withstanding the greater mass of potassium, the ion moves faster than sodium, since 

 it drags less water with it through the solution. This would increase the conduc- 

 tivity of potassium salts over that of sodium. The large conductivities of potassium 

 carbonate, dipotassium phosphate, and tripotassium phosphate are due to hydroly- 

 sis. The large values for potassium nickel sulphate, and for both the violet and 

 green potassium chromium sulphates are due chiefly to the large number of ions into 

 which these compounds dissociate. It was shown some time ago by Jones and 



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