502 



Dr. Arthur Schuster 



[Jan. 28, 



of the spectrum. But though there is an apparent tendency in this 

 direction, no rule can be given which shall be absolutely true what- 

 ever the substance which is dissolved. Fig. 2 shows the absorption 

 spectrum of cyanin when dissolved in different liquids. The measure- 

 ments made by Claes * are employed. We have here an interesting 



Fig. 2. 



5500 



GOOO 



6500 



A =: Absorption of Cyanin in Bisulphide of Carbon. 

 B = „ ,, Nitrobenzene. 



C = „ ,, Benzene. 



D = „ „ Ether. 



E — „ „ Alcohol. 



proof that a solution is sometimes much more of a chemical compound 

 than is generally supposed. The solvent and the substance must, 

 indeed, be closely connected in order to produce a shifting of the 

 absorption band. On the other hand, it is not astonishing that no 

 general law can be given which connects the dis2)lacement with the 

 physical properties of the solvent, for the closeness of connection 

 depending on the special chemical affinity for each solvent has as 

 much to do with the amount of shifting observed, as the molecular 

 weight or the dispersion or refractive power may have. The shifting 

 of the absorption bands in different solutions of the same substances 

 is only one of many applications of spectroscopes to the examination 

 of molecular phenomena in liquids. Into the interesting researches 

 of Professor Eussell, who has greatly extended this field of inquiry, 

 we have no time to enter. 



* Wied. Aun., ill. p. 388, 1878. 



