286 JONES AND ANDERSON— ABSORPTION SPECTRA OF [April 25, 



The slight changes taking place with some of the bands through- 

 out the spectrograms of plate 3 are perhaps sufficiently clear in the 

 reproductions. However, as a good 'deal of the detail shown by 

 the negatives is lost even in the most perfect processes of repro- 

 duction, we give here a description of the changes taking place in 

 two of the bands as seen on the original negative. We select the 

 bands at A 4275, and A 4760 from the negative for a, plate 3. 



In the aqueous solution the A 4275 band is very intense and nar- 

 row, its whole wadth being less than 5 Angstrom units. The edges 

 are only very slightly shaded. In the alcoholic solution the posi- 

 tion of the center of the corresponding band is A 4290. It has a 

 width of from 12 to 13 Angstrom units, and is not nearly as intense 

 as in the aqueous solution. 



Throughout the first six strips the A 4275 band maintains its 

 position and intensity almost unchanged. Its position does not 

 change in the least, but its intensity in the sixth strip is a trifle less 

 than in the others. In the seventh strip there is not the faintest 

 trace left of it. In the third strip, corresponding to the solution 

 whose alcohol content was 33^5 per cent., there appears at A 4285 an 

 extremely faint and narrow line. In the fourth strip it is some- 

 what wider and more intense, but its center is still at A 4285. In the 

 fifth strip it is beginning to be fairly conspicuous, and in the sixth 

 it is a band of moderate intensity having its center at about A 4287. 

 This band is undoubtedly the same one which in the pure alcoholic 

 solution has its center at A 4290 or very near there ; the exact wave- 

 length being perhaps nearer to A 4292. We see then that even when 

 the mixed solvent contains only about one-half alcohol this band 

 exists independent of and distinct from the band characteristic of 

 the aqueous solution ; that it is at first only a very narrow and faint 

 line which widens towards the red as the percentage of alcohol is 

 increased. 



The band whose center is at A 4760 has the following appear- 

 ance in the aqueous solution : Faint absorption begins at A 4748 and 

 rises rapidly to a maximum between A 4755 and A 4760, then de- 

 creases slowly to nothing at A 4775. The band is accordingly a 

 trifle asymmetrical, the slope towards the violet being considerably 

 steeper than that towards the red. The corresponding band in the 



