CONCLUSIONS. 259 



The solutions in question were studied with the spectroscope, the cell 

 having the same depth as for plate 35 (a). The solution in methyl alcohol 

 transmitted red and orange fairly well, but yellow and greenish-yellow faintly. 

 The spectrum began at 0.705/(, rose to a maximum at 0.640/*, and then 

 decreased to a region of very weak transmission which extended from 0.5S8/ 

 to 0.543/i. The methyl alcohol solution transmitted red and orange pretty 

 well, and yellow quite intensely. The spectrum was relatively weak in the 

 blue. Transmission began at about 0.716^ and reached its full value in the 

 neighborhood of 0.610^. The intensity decreased from about half its maxi- 

 mum value at 0.525/t to complete absorption at 0.4Sl/<. The spectrum of 

 copper bromide in methyl alcohol was very much more intense than that 

 for the solution of the same salt in ethyl alcohol. For the aqueous solution 

 transmission began near 0.636/<, rose to a maximum at about 0.5SO,, and 

 maintained a comparatively small intensity from 0.520, to 0.470/<. The 

 entire spectrum was a good deal weaker than the spectrum of the methyl 

 alcohol solution, and yet appreciably more intense than the solution in ethyl 

 alcohol. 



CONCLUSIONS. 



At the close of the account of the investigation of the absorption spectra 

 of certain aqueous solutions, a detailed discussion of the bearing of the spec- 

 troscopic results on the existence of hydrates was given. It was shown that 

 the theory was in complete agreement with the observed facts, without a 

 single exception. The fundamental interpretation given to the widening 

 of the absorption bands, either with increase in concentration of the colored 

 salt, or with increase in concentration of dehydrating agent, was that the 

 vibrations of the resonators were becoming less damped, due to the dehydra- 

 tion of the vibrating system. We should expect, then, that the absorption 

 bands characteristic of a given colored salt would become widest for the 

 anhydrous solutions, and would become narrower and narrower on adding 

 more and more water. No further details are necessary, since every spec- 

 trogram corresponding to the solutions that contained both a non-aqueous 

 solvent and water, bears out the theory in a most satisfactory manner. 

 The detailed explanation of the significance of the successive increments of 

 absorption need not be repeated for the solutions derived from non-aqueous 

 mother-solutions, since it was discussed so extensively in connection with 

 the aqueous solutions and the dehydrating agents. 



The complete spectroscopic investigation seems to leave no reasonable 

 doubt as to the correctness of the theory of hydrates as proposed in this 

 laboratory. 



In conclusion we wish to express our thanks to the Physical Department 

 of this University, for placing at our disposal the favorable conditions 

 under which the spectroscopic work was carried out. 



