Atoms , Ions and Molecules. 415 



" The term dissociation as applied to electrolytes in which 

 this independence of the ions does not exist is obviously a mis- 

 nomer. There is said to be an electrical force acting between 

 the various oppositely charged ions into which a dissolved 

 molecule separates, which in some way binds them. Even in 

 dilute solutions this force is very considerable and must make 

 the condition of charged ions moving independently in the 

 liquid so unstable as to be dynamically .impossible unless other 

 important forces operate at the same time." 



From these various considerations the following conclusions 

 may be drawn. 



1. When highly colored inorganic substances are composed 

 of colorless ions, then if these substances can be brought into 

 solution as electrolytes, the color wholly disappears. A num- 

 ber of instances are given above and no exceptions were met 

 with. Much that is important follows from this. It is proved 

 that the ions have become so far separated that they no longer 

 influence each others' vibration periods. For example, anti- 

 mony pentasulphide is an intensely colored substance. It dis- 

 solves easily in solution of alkaline sulphides forming absolutely 

 colorless solutions, because the ions of antimony and of sul- 

 phur are colorless and in the act of solution they separate 

 sufficiently to no longer change each others' vibration periods, 

 without however passing oat of each others' sphere of influence. 

 The ion theory is the only one capable of explaining this loss 

 of color, and on the other hand the reactions are so exactly 

 conformable to that theory that they constitute a new proof of 

 its correctness : perhaps the best proof yet presented. 



2. The union of ions colored and colorless gives rise to the 

 most surprising changes of color. Two similar colored ions 

 may unite to form a colorless element. Two similar colorless 

 ions may unite to form a strongly colored element. No black 

 ion is known. There is absolutely no relation traceable between 

 the color of an ion and that of the element which it aids to 

 form. 



3. The change of color of an acid indicator placed in con- 

 tact with an alkali in no way depends upon dissociation. Dis- 

 sociation may result, but the change of color is independent 

 of it. 



4. Selective absorption of the visual rays by an element can 

 never constitute a basis for classification, but the relation of 

 ions to the visual rays leads to a classification which is in abso- 

 lute harmony with the chemical characteristics of the elements. 

 Quite recently two chemists, Thomsen and deBoisbaudran, 

 have proposed new systems of classification, in both of which 



