CHEMICAL THEORY OF SOLUTIONS. FART I. 53 



{d) Physical Froj^eî'ties of Associated Liquids. 



The classical researches of Kopp and Landolt have called 

 forth a great many investigations on the relations existing between 

 physical properties and chemical composition, particnlarly of 

 liquids. But the work in this field slackened after a time, 

 partly owing to the rapid development of physical chemistry 

 which put forth so many interesting problems for solution, and 

 i^artly owing to the fact that the regularities found were mostly 

 imperfect and could not be brought into well defined simple 

 schemes. This is no doubt to a great extent due to the fact 

 that the investigators did not distinguish between normal and 

 associated liquids. It is self-evident that no good result can be 

 obtained when, for example, the system acetaldehyde ^ paral- 

 dehyde is treated as if it consisted of acetaldehyde alone. Such 

 irrational procedure has hitherto been quite general. But if the 

 molecular formulœ and the relative amounts of the chemical 

 species constituting associated liquids be determined by any 

 reliable method, then we shall be in a position to estimate the 

 physical properties of individual species. The comparison of 

 various chemical species will then no doubt show greater re- 

 gularities. 



§ 2. Quasi-ideal Solutions with a Normal and 

 an Associated Component. 



{a) Homogeneas EqaiUbriLun. 

 In the present case we have 



c,+a^+c^i, (30) 



