EVIDENCE FOR THE EXISTENCE OF HYDRATES IN AQUEOUS SOLUTION, 

 AND THE APPROXIMATE COMPOSITION OF THE HYDRATES FORMED 

 BY A LARGE NUMBER OF ELECTROLYTES. 



The work of Dr. Getman and that of Dr. Bassett, having to deal with 

 the same general problems, are so closely correlated that it is best to treat 

 the two investigations as a unit. We shall depart at this point from the 

 historical sequence in which the various facts were brought to light, in order 

 to treat the subject of hydrates in aqueous solutions in a more logical manner. 



EVIDENCE FOR THE EXISTENCE OF HYDRATES. 



One line of evidence for the existence of hydrates in aqueous solution 

 has already been furnished. The minima in the boiling-point curves occur 

 at greater concentration than in the freezing-point curves. The hydrates in 

 solution would be less stable at the higher temperature, and, therefore, a 

 greater concentration would be required for a sufficient production of these 

 substances to change the direction of the curve, thus giving the minimum 

 point. 



EFFECT OF TEMPERATURE ON WATER OF CRYSTALLIZATION, AS BEARING 

 ON THE THEORY OF HYDRATES IN SOLUTION. 



Another line of evidence, which seems to have some bearing, at least 

 indirectly, on the question as to whether there is combination between the 

 solvent and dissolved substances, is the following: If dissolved substances 

 combine with the solvent, we know that the resulting compounds are unstable, 

 especially at elevated temperatures. That this is the case is shown by the 

 fact that most of the water can readily be driven off from solutions of salts at 

 the boiling-points of these solutions. Indeed, in most cases practically all 

 the water can thus be removed, except that which is held in combination by 

 the salt at the temperature in question as water of crystallization. We shall 

 show that salts which crystallize with water of crystallization can combine, 

 when in solution, at ordinary temperatures, with a much larger amount of 

 water than they can bring with them out of solution, when they crystallize. 

 These hydrates are, then, more stable the lower the temperature; and, in 

 terms of our hydrate theory, we should expect that a salt would be able to 

 bring with it out of solution more water, as water of crystallization, the lower the 

 temperature at which the crystals were formed. 



It created surprise, on examining the literature, to find how large an 

 amount of_evidence was available bearing on this point. A good many 



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