GENERAL DISCUSSION OF THE RESULTS. 



RESULTS OBTAINED BY STINE. 



When this work was undertaken by Dr. Stine the suggestion that we have hydra- 

 tion in aqueous solution was about six years old. 1 Jones and Ota 2 and Jones and 

 Knight 3 had observed the abnormally great depression of the freezing-point of water 

 produced by certain electrolytes, and Jones and Chambers 1 had taken up a systematic 

 study of a few substances in this connection. This work was continued at the sug- 

 gestion of Jones by Chambers and Frazer, 4 and it was found soon that the phenom- 

 enon in question is of a more or less general character. 



This problem was then taken up systematically and in a broad way for the first 

 time by Jones and Getman. 5 They studied carefully a large number of typical 

 substances, and found the apparently abnormally great freezing-point lowering to 

 be a general phenomenon. This was later made more comprehensive by Jones and 

 Bassett. 6 



A method was worked out during this period for calculating the approximate 

 composition of the hydrates formed by the more common electrolytes, over a wide 

 range of dilution; and such calculations were made for a large number of substances. 

 At the time the work recorded in this monograph was undertaken by Dr. Stine, 

 we knew the approximate hydrating power at different dilutions of many of the sub- 

 stances with which we have to deal in the chemical laboratory. 



The problem which Dr. Stine solved (and when we consider the number of factors 

 involved, solved very successfully) was the effect of one salt on the hydrating power 

 of another salt present in the same solution. That the problem was of necessity 

 very complex can be seen from a moment's consideration. If we mix two salts 

 with a common ion, as is well known, each salt drives back the dissociation of the 

 other. This alone complicates the problem tremendously; further, that conduc- 

 tivity is not an accurate measure of dissociation in concentrated solutions also com- 

 plicates the problem. 



The first pair of substances studied contained a salt with large hydrating power 

 calcium chloride, and one with very small hydrating power potassium chloride. 



It was found that the amount of water combined increases with increase in con- 

 centration in the mixture as in the separate solutions; yet the total amount of water 

 combined with the calcium chloride is less when potassium chloride is present. 

 This is but the application of the effect of mass. The mixture of calcium chloride 

 and potassium chloride contains less water than a solution of calcium chloride of the 

 same concentration. We find in the case of the mixture, as in that of the simple 

 salt, that the number of gram-molecules of combined water increases with the con- 



lAmer. Chem. Journ., 23, 103 (1900). 'Ibid., 23, 512 (1900). 



Vbid., 22 (1899). 6 Carnegie Institution of Washington Publication No. 60. 



*/&"<*., 22, 110 (1S99). 'Zeit. phya. Chem., 46, 244 (1903); Phys. Rev.. 18, 146 (1904). 



200 



