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By WILLIAM A. TILDEN, D.Sc, T,ond., F.C.S. 



SOLUTION. 



IN order to narrow the discussion within reasonable limits and 

 to avoid unnecessary repetition, I do not propose, in 

 describing the phenomena of solution, to refer directly to the 

 following cases : 



a. The absorption of gases by liquids. 

 h. The intermixture of liquids. 



c. The simultaneous solution of two or more solid substances 



in the same liquid. 



d. Those cases of solution which are preceded or accom- 



panied by very obvious chemical changes, such as 



occur, for example, when chalk is dissolved in water 



by the aid of an acid. 



The kind of question then, that I propose to consider is this : 



Given a solid such as common salt or sugar, and a liquid in which 



it can dissolve without apparent decomposition, and from which 



it can be recovered with unchanged properties by evaporation or 



otherwise, what happens when the two are mixed together so as 



to form a solution ? This question is one which has occupied 



the attention of many chemists and physicists and has been the 



theme of extensive additions to scientific literature. Many 



doubtful points yet remain to be cleared up, but some light is 



beginning to dawn upon the obscurity in which the whole matter 



has so long been involved. 



In the resume which follows, I propose first to enumerate 

 briefly the principal phenomena whicli attend the act of solution, 

 and to describe the chief properties of simple solutions. An 

 attempt will then be made to enunciate a theory which will 



