52 



ATLAS OF ABSORPTION SPECTRA. 



165. Copper Chloride in Acetone. 



Fig. 91, pi. 23, and fig. 93, pi. 24. 



Fig. 91 shows the changes in the posi- 

 tions of the ends of the regions of 

 absorption and transmission of cop- 

 per chloride produced by varying the 

 solvent. The depth of the cell was 

 1.50 cm. Counting from the com- 

 parison spectrum towards the oppo- 

 site side of the spectrogram, the four 

 photographic strips correspond to 

 solutions of anhydrous copper 

 chloride in absolute acetone, in ab- 

 solute ethyl alcohol, in anhydrous 

 methyl alcohol, and in water, re- 

 spectively. The acetone solution was 

 brownish yellow. The ethyl solution 

 was dark green. The color of the 

 methyl solution was yellowish green. 

 The aqueous solution was blue. The 

 concentrations of the solutions, in 

 the order named, were, respectively, 

 0.022, 0.321, 0.283, and 0.795 normal. 



The aqueous solution absorbed all 

 radiations from 0.20/x to 0.387/x and 

 from 0.588/* into the red. 



The solution having methyl alcohol for 

 solvent absorbed all of the ultra- 

 violet from 0.20/J, to near 0.462/*. It 

 transmitted from 0.462/1 to beyond 

 the region of photographic sensibility 

 of the Seed films. 



The solution in ethyl alcohol absorbed 

 from o.20/i to about 0.515/1 and again 

 from o.59/t into the red. 



The acetone solution absorbed from 

 0.20/1 to near 0.510/1. It transmitted 

 from 0.510/1 to beyond the region of 

 sensibihty of the film used. 



These results were supplemented by 

 the aid of a Cramer "Trichromatic" 

 plate. A bluish-green, aqueous solu- 

 tion of concentration 1.590 normal 

 was substituted for the one referred 

 to above. The depth of cell and the 

 concentrations of the three remain- 

 ing solutions were unaltered. This 

 photograph showed that the new 

 aqueous solution transmitted from 

 o. 434/1 to 0.588/1, the methyl solution 

 from 0.462/1 to beyond 0.625/i, the 

 ethyl solution from 0.513/1 to 0.604/4, 

 and the acetone solution from 0.510/4 

 to be3-ond 0.625/*. 



165. Copper Chloride in Acetone Cont'd. 

 The exposures for the Seed film and 



the Cramer plate were, respectively, 

 1.5 and 2 minutes long. 



Fig. 93 shows the way in which the 

 limits of absorption change when 

 water is added to solutions of anhy- 

 drous copper chloride dissolved in 

 absolute acetone. The depth of the 

 cell was 2 cm. The solutions were 

 made up as explained under No. 158, 

 which see. 



The percentages by volume of the 

 water in the solutions under consid- 

 eration were o, i, 2, 3, 4, 6, and 8. 

 The concentration of the mother- 

 solution was 0.022 normal. 



The photographic strip nearest to the 

 comparison spectrum corresponds to 

 the solution which was anhydrous. 

 The next strip pertains to the solu- 

 tion which contained i per cent of 

 water, etc., across the entire spectro- 

 gram. The mother-solution ab- 

 sorbed completely all radiations from 

 0.20/1 to 0.517/4. The next four solu- 

 tions had a region of transmission 

 the center of which was at 0.436/t. 

 This region was followed by an ab- 

 sorption band whose middle was dis- 

 placed towards the ultra-violet as 

 the amount of water in the solutions 

 was increased. For the i and 2 per 

 cent solutions the center of the ab- 

 sorption band had the approximate 

 wave-lengths 0.478/* and 0.475/1, re- 

 spectively. The solution which con- 

 tained 8 per cent of water absorbed 

 all radiations from 0.20/1 to about 

 0.393/t and transmitted from this 

 wave-length to beyond 0.62/4. 



166. Copper Chloride in Ethyl Alcohol. 

 See No. 165. 



167. Copper Chloride in Methyl Alcohol. 

 Sec No. 165. 



168. Diamond. 

 Sec No. 154. 



169. Erbium Chloride.* 



Fig. loi, pi. 26. In solution very faint 

 pink. 



Concentrated (filtered). 



The solution was poured into a quartz 

 cell, the ends of which were plane 

 and parallel. The cell was succes- 

 sively adjusted to the following 



* A specimen from the collection of the late Prof. Henry A. Rowland. 



