4 HYDRATES IN AQUEOUS SOLUTION. 



were not limited to a few hygroscopic substances, but were shown by quite 

 a number. This but raised the question, How general is this phenom- 

 enon? Is it limited to certain classes of compounds, or is it shown by elec- 

 trolytes in general? The systematic investigation of typical compounds, 

 representing the whole field of the electrolytes, was then begun. We under- 

 took to study not only a large number of acids, bases, and salts, but also 

 to determine the freezing-points and conductivities of very concentrated 

 solutions of these substances. In this way it seemed reasonable to hope 

 that some light might be thrown on the nature of concentrated solutions. 



It was clearly recognized that the theory of dilute solutions, which has 

 proved so valuable in coordinating existing facts, and so fruitful in sug- 

 gesting new lines of investigation, did not apply at all to concentrated 

 solutions. Indeed, the theory was strictly applicable only to very dilute 

 solutions, not holding even for those concentrations with which we ordina- 

 rily have to deal in the laboratory. This fact has been advanced as an 

 objection to the present theory as to the condition of things in solution. 

 It has been justly said that we do not have a theory of solutions in 

 the broad sense, but only a theory that applies to ideal conditions; the 

 actual solutions with which we work and with which directly we are most 

 concerned, not coming within its scope. In a word, we had no theory of 

 concentrated solutions. 



It was with the ultimate object of ascertaining, as far as possible, the 

 nature and condition of the dissolved substance in the more concentrated 

 solutions, that the present systematic and somewhat extended investigation 

 was begun. 



A brief account of the apparatus used and the mode of procedure in 

 this earlier stage of the work are given. 



APPARATUS. 



FREEZING-POINT APPARATUS. 



Fig. 1 shows the apparatus used in determining the freezing-points of 

 the solutions. It will be seen to be essentially that devised by Beckmann. 

 The thermometers used were made expressly for this work. They were 

 of the Beckmann type, one having a range of 12, each degree being divided 

 into fiftieths; the other having a range of 25, each degree being divided into 

 twentieths. The thermometer with the greater range was used when work- 

 ing with very concentrated solutions, which gave a large depression, while the 

 more finely graduated instrument was used with the more dilute solutions. 



The stirrer in the freezing-tube consisted of a ring of stout platinum wire, 

 around which was wrapped a spiral of fine platinum wire. The size of 



