232 



HYDRATES IN AQUEOUS SOLUTION. 

 TABLE 116. 



On account of excessive undercooling it was not possible to freeze the solu- 

 tion of concentration 2.200 with the mixture of ethyl alcohol and solid carbon 

 dioxide. This solution became a light-green, very viscous jelly at 



75. 



GENERAL SUMMARY OF RESULTS. 



DISCUSSION OF THE SEVERAL THEORIES. 



The theory of Engel, that the blue color of solutions of cobalt chloride is 

 due to the presence of double salts, appears to us untenable for a number 

 of reasons. In the first place, it has been shown by Jones and Ota* and 

 Jones and Knightf that double chlorides in general, even in very concen- 

 trated solutions, are largely broken down into the single salts which are disso- 

 ciated in the usual manner. In such solutions we should not have simply 

 the molecules of the double salt, but a large number of the ions resulting 

 from the dissociation of such a compound. 



Again, this theory is entirely out of accord with the fact that a strong, 

 aqueous solution becomes blue when heated. The increase in the hydroly- 

 sis with the comparatively slight rise in temperature is not sufficient to 

 liberate enough hydrochloric acid to account for this color change on the 

 basis of a compound being formed with this acid. 



Further, this theory is not in accord with the color changes which mani- 

 fest themselves when water is added to solutions of cobalt chloride, etc., in 

 methyl and ethyl alcohols and acetone, where no double salt can be present. 



The following consideration would appear to have very direct bearing 

 upon the theory under discussion: An examination of the spectrogram 

 will show that with increasing amounts of the dehydrating agents or salt the 



*Amer. Chem. Journ., 22, 15 (1S99). 

 \lbid., 22, 110 (1899). 



