214 Professor Liveing, On the Influence of Temperature, etc. 



to suppose that the absorption by a molecule would be altered 

 by its being charged with electricity. The absorptions which are 

 intensified by concentration and also by heat must be ascribed 

 to the condition of the molecules during encounters, which will be 

 more frequent in more concentrated as well as in hotter solutions. 

 The expansion of certain bands with increased concentration by 

 the nitrate, must be ascribed to encounters of molecules derived 

 from the metal with those derived from the acid, which are much 

 more massive than the molecules of water and also than those 

 derived from the chloride. During such encounters the absorbent 

 molecules will be as it were loaded by the influence of the other 

 molecules. This view seems confirmed by the influence which 

 other solvents and other acids have on the absorptions. Didymium 

 chloride in alcohol gives the same bands as the aqueous solution, 

 but generally more diffuse and more or less shifted a little towards 

 the red. The same solution acidified with hydrochloric acid ex- 

 aggerates greatly these modifications, almost washing out the more 

 refrangible bands and breaking up the very strong band in the 

 yellow into several separate bands. Glycerol as solvent gives 

 modifications similar to, but more strongly marked than, those 

 of alcohol. The acetate in acetic acid and the maleate in water 

 gives similar but much less marked modifications. The tartrate 

 and the citrate in ammoniacal solution also give similar modifi- 

 cations. The borate in solid glass of borax also gives bands which 

 are unmistakably modifications of those produced by the aqueous 

 solution. All these modifications seem to be of the same character, 

 though of greater intensity, than the differences between the 

 bands given by nitrate and chloride, and may be attributed to 

 the influence of the comparatively complicated influences of the 

 various molecules during the times of encounter. In such cases 

 as the acid alcoholic solutions there will certainly be at least four 

 chemical compounds mixed in the solvent, which may well produce 

 a complicated modification of the bands without destroying their 

 identity. 



