COPPER CHLORIDE IN METHYL ALCOHOL. 251 



comparison spectrum corresponds to acetone. The remaining strip resulted 

 from light transmitted by ethyl alcohol. The depth of the cell was 1.41 cm. 

 As is well known, water is exceptionally transparent to short light waves, 

 so that the negative strip for this liquid recorded as many lines in the remote 

 ultra-violet as was shown by the comparison spectrum. The shortest wave- 

 length given by the strip for methyl alcohol was 2313.0. The strong cadmium 

 line, however, was just barely visible on the negative. The intense lines at 



2558.0, 2573.1, and 2712.6 were rather fully transmitted. The continuous 

 background for waves more refrangible than 2748.7 was extremely weak. 

 The third strip showed that ethyl alcohol was more transparent than methyl 

 alcohol to the remote ultra-violet, since it recorded distinctly the lines at 



2265.1, 2288.1, 2313.0, and 2321.2. On the other hand, the lines at 2558.0, 

 2573.1, and 2721.6 were not quite as strong after passing through the ethyl 

 alcohol as the}' were after emerging from the methyl alcohol. Taking the 

 continuous background into account, as well as the spark lines, the negative 

 shows that methyl alcohol has a one-sided region of absorption in the ultra- 

 violet, whereas ethyl alcohol has a region of semi-transparency in the neigh- 

 borhood of 0.230/t, with strong absorption on both sides. For all ultra- 

 violet and visible waves less refrangible than 274S.7 the transmission of these 

 two alcohols seems to be identical. Acetone showed intense selective ab- 

 sorption in the ultra-violet, since the associated photographic strip recorded 

 nothing beyond 3282.4. This line was very much weakened, and the correct 

 limit of this region of absorption was 3302. 7 A. U. The conclusion is that 

 the ultra-violet absorption of the cobalt chloride was only masked by that 

 of the solvent in the case of acetone. In all of the other cases studied, the 

 ultra-violet absorption was due largely to the cobalt chloride in the solution, 

 and riot so much to the solvents as such. 



COPPER CHLORIDE IN METHYL ALCOHOL. [See plate 28.] 



The concentration of the mother-solution of copper chloride was 0.283. 

 The percentages of water in the solutions of the series were 40, 36, 32, 28, 

 26, 24, 22, 20, 16, 12, 8, 4, and 0. All the successive differences in this 

 sequence of numbers were equal to 4 per cent, except the fourth, fifth, sixth, 

 and seventh. Each of the four exceptional increments was equal to 2 per 

 cent. To obtain a general idea of the dependence upon the amount of water 

 present, of the limit of absorption of the band which included the ultra- 

 violet, it is convenient to omit the fifth and seventh photographic strips from 

 consideration. As the amount of water decreased, the color of the solutions 

 varied from greenish-blue through pure green, to a green with a yellow tint. 



The strip corresponding to the 40 per cent solution is adjacent to the num- 

 bered scale, and that belonging to the mother-solution lies next to the com- 

 parison spectrum. The depth of the cell was 2.40 cm. The negative showed 

 only one region of absorption, and it included the entire ultra-violet; the 



