488 



J. H. van't Hoff on the Origin 



mercury (Tammann), thiophene in benzene, antimony in tin, 

 naphthol in naphthalene (van Bylert), indol in naphthalene, 

 carbazol in anthracene (Ferratina and Garelli), and also with 

 ketopentene derivatives. 



According to Ferratina and Garelli it would appear that a 

 too small lowering of the freezing-point is a simple means 

 for determining the constitution of a substance, as the freezing 

 out of the dissolved substance is very often to be inferred 

 from similarity of constitution. In this way it was shown, 

 e. g., that nicotine probably was not a dipyridyl derivative, 

 and this is confirmed by the work of Pinner and Blau. 



Abnormally Large Depressions of the Freezing-point. — To 

 return once more to the osmotic experiment of de Vries. 

 The so-called isotonic coefficients, which are obtained by 

 comparison of isotonic solutions, express the relative osmotic 

 force in solutions which contain the same number of molecules 

 in equal volumes, or, in other words, the relative osmotic 

 force of molecular quantities. 



The so-called isotonic coefficients, which occur in so many 

 physiological experiments as conditional factors, should 

 according to the theory be equal to unity ; they are thus 

 obviously of serious importance in the development of a 

 " theory of solutions" and have imposed on me, in my Swedish 

 memoir, a certain amount of restraint in speaking of a 

 remarkable property frequently occurring in rarefied matter. 



Since that time, however, the state of affairs has altered. 

 Arrhenius has shown that the abnormally high values occur 

 only in solutions which conduct electricity, and numerous 

 reasons have been adduced to explain the abnormally high 

 values in consequence of the presence of ions obtained by the 

 splitting up of the molecules in solution. In the following table 

 I give the numbers which have been obtained in some of the 

 most significant cases, and a glance suffices to show what has 

 already been attained in this way: — 



Substance. 



Isotonic coefficient 

 found. 



Do. calculated from 

 the conductivity. 



KC1 



1-81 



1-82 



2-48 



1-92 

 2-8-2-3 

 1-2-1-4 



3-09 



6-02 



1-2 



2-47 



1-85 

 1-84 

 2-46 

 1-84 

 2-48 

 1-35 

 3-07 

 5-93 

 T37 

 2-39 



NH 4 C1 



Ca(NO,) 



LiOl 



MffOl, 



MgS0 4 



FeCy 6 K 4 



Co,Cy 10 JL, 





Tartar-emetic 





