258 HYDRATES IN AQUEOUS SOLUTION. 



A series of solutions could not be prepared from copper bromide and acetone, 

 since the latter oxidizes the acetone; it itself probably being reduced to the 

 cuprous condition and immediately precipitated. The spectrograms that 

 were taken for the purpose of comparing with one another the absorption 

 spectra of certain solutions of copper bromide in water, in methyl alcohol, 

 and in ethyl alcohol, are reproduced as plates 35 (a) and 35 (/>). 



Since the mother-solutions are too opaque to give satisfactory spectrograms, 

 each was diluted with the proper solvent. The concentrations of the solutions 

 of copper bromide in water, in methyl alcohol, and in ethyl alcohol were, 

 respectively, 0.874, 0.036, 0.032. When placed in the cell at a depth of 

 0.24 cm., the solutions in the order given above were green, light yellow, and 

 yellow with a brownish tinge. For plate 35 (&) the strip adjacent to the 

 numbered scale corresponds to the solution in ethyl alcohol. The middle 

 strip pertains to the solution in methyl alcohol, and the strip nearest to the 

 spark spectrum corresponds to the aqueous solution. The strip for the ethyl 

 alcohol solution showed that transmission began at about 0. 445 /<, and remained 

 comparatively weak as far as 0.527/*. From this latter point on towards the 

 red, transmission was relatively strong. The negative strip pertaining to the 

 solution in methyl alcohol showed that transmission began near 0.419/, and 

 continued intense as far as the limit of sensibility of the photographic film. 

 The negative strip corresponding to the aqueous solution showed that trans- 

 mission began at 0.403^. and remained strong to the limit set by the absence 

 of sensitiveness of the film to orange light. The fact that the middle strip 

 extends beyond the adjacent strips at their less refrangible ends, shows that 

 slight general absorption of the orange was exerted by the solutions in ethyl 

 alcohol and in water. 



The negative for plate 35 (a) was taken with a Cramer trichromatic plate. 

 The cell depth was 1.5cm., and each exposure to the light from the Nernst 

 filament was two minutes long. At this depth the solution of methyl alcohol 

 had a deep, dull-brown color. The solution in methyl alcohol was a deep 

 brownish-yellow. The aqueous solution was dark green. The strip adja- 

 cent to the scales corresponds to the aqueous solution, the middle strip per- 

 taining to the solution in methyl alcohol as solvent. The negative showed 

 that the ethyl alcohol solution transmitted very weakly from 0.554^ to the 

 end of the plate. The photographic maximum of transmission was near 

 0.595/i. The middle strip showed that the methyl alcohol solution began to 

 transmit at about 0.480/*, and that transmission was practically complete 

 from 0.510/i to the end of the field of view of the spectrograph. The negative 

 strip next to the spark spectrum showed that the aqueous solution began to 

 transmit at 0.455ju ; but the brightness of the transmitted light increased 

 very slowly to a maximum in the vicinity of 0.556/. Transmission ended at 

 O.G03/J. 



