336 F. B. Pitcher — Absorption Spectra of Blue Solutions. 



about one half. The addition of ammonia, to the extent neces- 

 sary to produce the color-change denoting alkalinity, further 

 widened and deepened the absorption band in the yellow and 

 increased the absorption throughout the entire spectrum. The 

 diminution in intensity was greater in the red, however, than 

 in the regions lying beyond the great absorption band. 



For the determination of the influence of ammonia upon 

 copper sulphate, a concentrated solution of the salt was pre- 

 pared and its curve obtained by the method * already described. 



3 



2\ 



. — h 



This solution when viewed by transmitted light, in a layer 

 only one centimeter in thickness, shows but feeble color, and 

 the intensity curve (figure 4, curve ^), indicates but little ab- 

 sorption excepting in the extreme red. Noteworthy is the 

 well-marked maximum between the E and F lines and the rela- 

 tively large amount of absorption in the violet. 



The addition of ammonia was found to produce strong ab- 

 sorption throughout the orange and yellow, the minimum cor- 

 responding in position with that observed in the case of alka- 

 line litmus (curve f). Beyond the point of maximum, between 

 E and F, in the curve of the neutral salt, the ammonio-sulphate 

 had become almost completely transparent, with just a trace 

 remaining of the small absorption band lying beyond the F line* 

 (See curve A.) 



The almost untouched domain of the spectro-photometric 

 investigation of absorption spectra is an extensive one ancl by 

 no means devoid of interest. The writer hopes ere long to 

 add to the present contribution, studies of some of the aniline 

 colors and of the influence of acids and alkalies upon the 

 spectra of the so-called " color-test " solutions. 



August 1, 1888. 



