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Chemistry. — "llw soluhUltics of the isomeric chrouiic cldori(ies'\ 

 By Prof. H. W. Bakhuis Roozeboom and J. Olie Jr. 



(Communicated in the meeling of May 27, 1905). 



At the December meeting 1903, a communication was made by 

 Bakhuis Roozeboom and Aten as to tlie changes in form which may 

 occur in the sohibilitj-Unes of binary mixtures in dependence on the 

 quantities of the molecuJes of a compound which may be formed 

 from the components in the liquid mixtures. This subject is only 

 a part of a more extensive problem embracing the equilibria of 

 phases in systems composed of three kinds of bodies between 

 which a transformation is possible in liquid (or vapour). If that 

 transformation takes place with greater xelocitj than the setting 

 in of the equilibria of phases, the system will appear externally as 

 a binary one, although it is in reality ternary, and in order to 

 explain the course of the equilibria of phases we must take into 

 account that ternarj" nature. 



In those cases where the third kind of molecules consists of a 

 combination of the two others no instance has, as yet, been noticed 

 where a correct view could be formed Avilh certainty as to the inner 

 composition of the liquid phase. 



We, however, came across an example where this is quite possible, 

 namely in a case where two isomeric substances may be converted 

 into each other by dissolving in a third substance. Similar cases mvij 

 frequently occur with all kinds of organic isomers; but apart from 

 the fact that their behaviour has been little investigated from the 

 point of view of the equilibria of pliases we often lack the means 

 to determine the two kinds in solution. That possibility, however, 

 presented itself with the isomeric chromic chlorides, which not 

 only may be determined in each others' presence, but also require 

 when in solution much more time to reach an equilibrium than is 

 necessary to reach the equilibrium between solid matter and solution. 

 This rendered it also possible to study the change of the solubility 

 as a function of the progressive transformation in the solution. 

 Finally, this research could also serve to elucidate the cause of the 

 stability or unstability of the isomers, and the most rational method 

 of preparing the same from the solution. 



It has long been known that all kinds of salts of trivalent chromium 

 when in solution undergo molecular transformations depending on 

 temperature and concentration ^vhich are shown by the change in 

 colour of the solutions, which may vary from gi'cen to ^•iolet. 

 Only of late this matter has been better understood when various 



