COPPER BROMIDE IN ETftYL ALCOHOL. 257 



absorption in the orange and red. The strips corresponding to the solution 

 whose percentages of water were 10, 8, 6, and 4, showed that a region of weak 

 general absorption formed a continuation into the. blue and green, of the 

 region of intense absorption of the ultra-violet and violet. The strength of 

 this general absorption increased rapidly as the amount of water in the solu- 

 tions decreased. This is exactly the same phenomenon as was brought to 

 light by the negatives for the solutions of copper bromide in methyl alcohol 

 and varying amounts of water. The strip corresponding to the anhydrous 

 solution recorded extremely faint transmission from 0.544/ towards the red. 

 The negative for plate 33 (a) was taken with a Cramer trichromatic plate. 

 The spectra photographed corresponded to the five solutions of the series 

 that contained the smallest amount of water, which included, of course, 

 no water. The depth of the cell was 0.24 cm. The exposures to the light 

 from the Nernst filament were each two minutes long. The strip nearest to 

 the scales corresponds to the solution that contained 10 per cent of water. 

 The fifth strip, counting away from the scales, pertains to the mother-solution. 

 The negative strip, corresponding to the 6 per cent solution, recorded the 

 beginning of very faint transmission near 0.451/<, and showed that relatively 

 intense transmission did not commence until about 0.510/<. The wave-lengths 

 corresponding, respectively, to the beginning of faint and strong transmission 

 were given as 0.49S/< and 0.533/t by the strip for the 4 per cent solution. The 

 mother-solution, according to the negative, transmitted very weakly from 

 about 0.538/t to the end of the field of view of the spectrograph. Eye obser- 

 vations recorded qualitatively the facts revealed by the negative, and also 

 supplemented the latter by giving data for the red end of the spectrum. 

 The depth of cell was, as formerly, 0.24 cm. All light transmitted by the 

 mother-solution was very weak; yet the transmission in the red was relatively 

 intense, as compared with that in the yellow and green. More specifically, 

 transmission began at about 0.725/i, rose to a maximum at 0.653/*, and then 

 fell to a very small value in the neighborhood of 0.59S,. Faint light could 

 be observed from 0.598/t to about 0.51S/<. At the latter wave-length absorp- 

 tion became complete. The spectrum transmitted by the 4 per cent solu- 

 tion was similar to thatof the mother-solution. The yellowand green regions, 

 however, were somewhat stronger, but the blue was very much weakened. 

 The contrast between a relatively bright region of transmission, and a weak 

 region at the more refrangible side of the former, gradually disappeared as 

 the quantity of water in the solutions decreased. The gradations were shown 

 very well by the corresponding negative strips of the spectrogram. For the 

 solution that contained the greatest amount of water the spectrum began 

 near 0.758/1. The complete series of eye observations showed that the visible 

 end of the absorption band, whose center was in the infra-red, moved towards 

 this region as the percentage of water in the solutions increased. 



