DISCUSSION OF THE SEVERAL THEORIES. 233 



absorption bands widen out. With increasing amounts of the dehydrating 

 agents used in this work more and more of the double halides, if they existed, 

 would be formed, since the solutions would be more and more concentrated. 

 This would mean that the vibrating, charged particle was becoming more 

 and more complex. The above facts are not in harmony with one another. 

 The most probable interpretation of the widening of the absorption bands 

 with increase of concentration, is that the vibrating charged particle is becom- 

 ing of smaller and smaller mass, and can thus vibrate in resonance with a 

 larger number of wave-lengths. 



There are also a number of objections to the theory proposed by Ostwald 

 to account for the color changes of cobalt chloride. It will be recalled that 

 Ostwald takes the view that the blue color is due to the cobalt molecule, 

 and the red color to the cobalt ion. This would not account for the great 

 color change produced by warming a concentrated, aqueous solution of cobalt 

 chloride. The dissociation would decrease a very small amount for the 

 change in temperature from, say, 25 to 75 or 80, as is shown by the work 

 of Jones and West* and especially by that of Noyes and Coolidge.t This 

 slight change in the dissociation would be entirely incapable of accounting 

 for the marked color changes produced. Further, the amount of hydro- 

 chloric acid liberated as the result of the increased hydrolysis with rise in 

 temperature would be far too small to drive back the dissociation sufficiently 

 to produce such marked changes in color. 



Another objection to this view is that the amount of water required to 

 color a blue alcoholic solution red is altogether too small to produce a suffi- 

 cient increase in the dissociation to cause the observed color change. 



Further, the amount of water that is required to change very appreciably 

 the color of a solution of cobalt chloride rendered blue by the presence of 

 aluminium chloride is very small, indeed, as is shown by table 108. The 

 small amount of water could not, of course, materially increase the dissocia- 

 tion of the solution of cobalt chloride. 



This shows that we can not account for the color changes solely, or even 

 primarily, on the basis of dissociation. 



That there are serious objections to the theory of Donnan and Bassett, 

 that the blue color is due to complex ions of cobalt, is made evident by the 

 following considerations: 



The alcoholic solutions show in general the same color changes when water 

 is added, as are manifested by the aqueous solutions in the presence of dehy- 

 drating agents. A comparison of the spectrograms in this section, and the 

 eye observations, with those in the latter part of this monograph, will show 

 that the same absorption bands appear in the aqueous and in the non-aqueous 



*Amer. Chem. Journ., 34, 357 (1905). 

 f Ztschr. phys. Chem., 46, 323 (1903). 



