62 MOLECULAR WEIGHT AND POLYMERISM 



freezes ; hence we have a departure from the assumptions 

 made in determining the formula 



O-O2 T 2 



~W~' 



and it will appear later that for that reason the lowering 

 of the freezing point should be smaller. 



The phenomenon in question has been applied by 

 Ciamician and Garelli 1 to settle doubtful cases of iso- 

 morphism, and by that means the constitutional formula, 

 since it is known that isomorphism goes hand in hand 

 with similarity of constitution. 



4. Abnormal Results for Electrolytes. 



Lastly we must consider the great exceptions which 

 occur in electrolytes, i.e. especially solutions of salts, 

 strong acids, and bases in water, where the lowering of 

 the freezing point often amounts to twice or more times 

 the normal amount 2 . It was just this phenomenon that 

 so long stood in the way of the discovery of the simple 

 laws applicable to dilute solutions, which first came to 

 light when Raoult made his freezing-point measurements 

 on non-electrolytic solutions, i.e. on solutions in solvents 

 other than water, and solutions in water of organic 

 substances not of a salt character. It is well known 

 that the phenomenon in question led to the theory of 

 electrolytic dissociation, which now requires special 

 treatment. 



The Theory of Electrolytic Dissociation. Arrhenius 

 attributed the abnormally large change of freezing point 

 just mentioned, and the abnormally high osmotic pressure 

 deduced from it, to a decomposition into ions, i. e. electri- 

 cally charged portions <af molecules. The extensive data 



1 Zeitschr.f. Phys. Chem. 13. i, 18. 51, 21. i. 



2 The greatest deviation has lately been found by Crum Brown for the 

 salts of sex-basic mellitic acid. 



