DISCUSSION OF EVIDENCE. 181 



This fact was first noted by Jones and Anderson, and since repeatedly 

 confirmed by the work of Jones and Strong. We found that when 

 neodymium chloride was dissolved in a mixture of methyl alcohol and 

 water, it showed a definite set of "water" bands and a definite set of 

 "methyl alcohol" bands. As the amount of water in the solution 

 was decreased relative to the alcohol, the "water" bands decreased 

 in intensity but remained in the same position. As the amount of 

 alcohol in the solution was decreased relative to the water, the "alcohol " 

 bands decreased in intensity, but their position remained unchanged. 



Jones and Anderson interpreted these facts as strong evidence in 

 favor of the view that there are definite hydrates and definite alco- 

 holates in the solution. 



The spectroscopic evidence for solvation in solution furnished by 

 Jones and Anderson has, as has already been stated, been increased 

 many fold by the work of Jones and Strong. A large number of 

 solvents and a fairly large number of salts have been used, and the 

 existence of solvent bands in general has been established. 



The question of the relative stability of the different solvates with 

 respect to various physical and chemical agents has been studied at 

 length by Jones and Strong by means of absorption lines and bands. 

 It would lead us beyond the scope of this paper to discuss these results 

 in detail. Suffice it to say that the hydrates in general are the most 

 persistent of all the solvates, although this depends upon the conditions 

 to which the solution is subjected. 



Taking all of the spectroscopic work into account, I regard the evi- 

 dence from this source as strongly supporting the solvate theory of 

 solution as advanced by myself about fifteen years ago. 



EFFECT OF RISE IN TEMPERATURE. 



Jones and Strong studied the effect of rise in temperature on the 

 absorption spectra of solutions. Considerable work had already been 

 done on the effect of temperature on absorption spectra over the tem- 

 perature range to 100. This temperature limit could be studied 

 in open vessels. To work at higher temperatures closed apparatus 

 must, of course, be used. Such apparatus was devised and used up 

 to 200 . 1 



The general effect of rise in temperature is to increase the color of 

 the solution of the inorganic salt, the solution becoming less trans- 

 parent. The deepening of the color is usually due to a widening of 

 the absorption bands. The widening of the bands with rise in tem- 

 perature is frequently unsymmetrical. 



While the effect of rise in temperature is to cause the long wave- 

 length bands to increase in intensity, and in some cases to produce 

 new bands, in some solvents the effect of rise in temperature is to 

 cause the short wave-length bands to increase in intensity and even 



Carnegie Inst. Wash. Pub. No. 130. 



