COPPER CHLORIDE IN ACETONE. 253 



COPPER CHLORIDE IN ACETONE. [See plate 30.] 



The concentration of the mother-solution of copper chloride in acetone 

 was 0.022. The percentages of water in the various solutions of the set were 

 28, 24, 22, 20, 18, 16, 12, 10, 8, 6, 4, 3, 2, 1, and 0. The first and sixth differ- 

 ences were 4 per cent. The last four increments were each 1 per cent, and all 

 the remaining increments 2 per cent. The solutions varied in color from 

 bluish-green to dark olive as the percentage of water decreased from 28 to 0. 

 The strip most remote from the numbered scale corresponds to the anhydrous 

 mother-solution ; the next strip pertaining to the solution which contained 1 

 per cent of water, and so on until the strip adjacent to the scale corresponds 

 to the solution which contained the greatest amount of water. The depth 

 of the cell was 2 cm. The complete spectrogram shows a region of strong 

 absorption in the ultra-violet and violet, and also a band in the blue-green. 

 The negative strip pertaining to the solution which contained 28 per cent 

 of water, recorded faintly the zinc doublet at 3345, but the continuous back- 

 ground practically ceased at 0.344,. The locus of the limits of the region of 

 absorption, which comprise the entire ultra- violet, is a smooth curve concave 

 towards this region. The strip corresponding to the 4 per cent solution 

 barely indicated the existence of an absorption band whose center was at 

 0.473/t. The remaining strips, which correspond to the solutions that con- 

 tain less than 4 per cent of water, show that the band both widened out 

 rapidly and had its center displaced slightly towards the red as the amount 

 of water decreased. In fact, a strip pertaining to the anhydrous solution 

 showed that the band in the blue-green had united with the wide region of 

 absorption in the ultra-violet, so that no light of wave-length shorter than 

 :527/t was transmitted. The middle of the transparent region between the 

 two bands of absorption in question was at about 0.436/*. 



Eye observations with the spectroscope, and with the cell 2 cm. deep, 

 brought out the following facts: The mother-solution transmitted freely 

 orange, yellow, and yellow-green. Its spectrum began at 0.706/t and ended 

 near 0.507/t. Since, when the cell was not in the path of the light incident 

 upon the slit of the spectroscope the spectrum began at 0.775/, it is evident 

 that the mother-solution absorbed all the deep red. The 2 per cent solution 

 began to transmit at 0.727/<. The transmission spectrum began to be much 

 weakened near 0.503,, and showed a weak band of partial absorption at 

 the more refrangible side of the wave-length. Faint light could be distin- 

 guished as far as 0.435 . The minimum of transmission in the blue-green 

 could also be observed in the case of the 4 per cent solution. The solution 

 which contained the greatest amount of water began to transmit at about 

 0.750.U. The entire series of observations showed that the more refrangible 

 limit of the band which absorbed the red, receded towards the infra-red as 

 the percentage of water in the solution increased. 



