230 HYDRATES IN AQUEOUS SOLUTION. 



0.600. and 0.550. At the latter wave-length the light decreased abruptly 

 to zero. There was no visible return of transmission in the region of the 

 shorter waves. 



Transmission began at 0.730/<, rose to a maximum at0.660/(, and decreased 

 to almost no color near 0.59CV for the solution of concentration 3.050. An 

 extremely weak region of transmission extended from a little beyond 0.590/t 

 to 0.575/t. Because of its faintness, the subjective color throughout this 

 region was gray. 



The solution of concentration 3.304 transmitted chiefly bright red. The 

 extreme limits of the spectrum were approximately 0.733/t and 0.625/^, the 

 brighest spot being at 0.670/(. Only red from about 0.730ju to 0.640^ was 

 transmitted by the solution of concentration 3.558. Finally, the most con- 

 centrated solution of the series transmitted red from about 0.725/i to 0.650/<. 

 The most intense portion of this spectrum was near 0.6S4/<. 



The lowerings of the freezing-point of water produced by the solutions 

 which contained copper bromide and calcium bromide are given in table 

 115, page 229. 



The solution of concentration 3.558 could not be frozen within the range 

 of the scale of the thermometer, i.e., between zero and 80. 



COPPER BROMIDE AND ALUMINIUM CHLORIDE. [See plates 21 (a) and 21 (6).] 



The concentrations of the mother-solutions of copper bromide and alumin- 

 ium chloride were, respectively, 2.186 and 2.75. In the series of solutions 

 discussed below, the constant concentration of the copper salt was 0.219. 

 The concentrations of the dehydrating agent were 0.000, 0.275, 0.550, 0.825, 

 1.100, 1.375, 1.650, 1.925, 2.200, 2.480. All the successive differences in 

 concentration are equal to 0.275, except the last increment, which equals 

 0.280. As the amount of the dehydrating agent increased, the solutions 

 changed from greenish-blue to brown, passing through various intermediate 

 shades of bluish-green, green, olive, and brownish-green. The photographic 

 strips corresponding, respectively, to the solutions which contained none of 

 the aluminium chloride, and the greatest amount of this salt, are adjacent 

 to the numbered scale and to the comparison spectrum. The depth of the 

 cell was 1.41 cm. The most noticeable facts shown by the negative of plate 

 21 are the following: 



The faintest trace of the intense cadmium doublet at 3612 was recorded 

 by the strip corresponding to the aqueous solution which contained only 

 copper bromide. The continuous background, however, faded out at about 

 0.371^. The spectrogram shows very clearly that for the first seven or eight 

 solutions the absorption band, which included the entire ultra-violet region, 

 advanced by ever-increasing increments as the concentration of the alu- 

 minium chloride became greater and greater. The seventh negative strip 



