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



much as possible of the structure of the larger bands. The first 

 spectrogram is reproduced as a, the second as b, plate 4. The 

 strips corresponding to the pure alcohol solutions are adjacent to 

 the numbered scale, the spectrum of the solution containing 16 per 

 cent, water being next to the comparison spark spectrum. 



Although we found in considering plate 3 that some slight change 

 in the spectrum takes place where the percentage of alcohol is 

 changed from o to 83 per cent., yet this change is so small and 

 the bands due to the aqueous solution are so strong that we may 

 regard the spectrum of a solution containing 16 per cent, of water 

 as practically that of the aqueous solution. Accordingly, the spec- 

 trograms on plate 4 may be taken to show very nearly the whole 

 change which takes place when the solvent of neodymium chloride 

 is gradually changed from pure water to pure methyl alcohol. 



In a the ultra-violet band is rather too intense to allow its 

 structure to be seen. Accordingly, we see the whole band remains 

 sensibly unchanged as the water is varied from 16 per cent, to 8 

 per cent., and then shifts towards the red with .increasing rapidity as 

 the water is reduced to zero; the whole apparent shift amounting to 

 about twenty Angstrom units. On the negative the intense band 

 at X 3465 may, however, be clearly seen, and its intensity decreases 

 very slowly from the first to the third strips, counting from the 

 narrow comparison spark spectrum. In the fourth strip its inten- 

 sity is about half of what it was in the first strip, and from this it 

 decreases rapidly, vanishing entirely in the strip nearest the scale. 

 In b the structure of this band is seen very distinctly, and we find 

 that the bands characteristic of the aqueous solution gradually de- 

 crease in intensity, especially from the third to the sixth strips, while 

 the wider bands characteristic of the alcoholic solutions increase in 

 intensity, the two sets existing together. The change in the band 

 at A 4275 is the one that shows the best, because here the two bands 

 belonging to the aqueous and alcoholic solutions, respectively, are 

 both intense and narrow and clearly separated from each other. 

 The alcoholic band is clearly visible in the first strip, and it in- 

 creases continuously in intensity as the amount of water is de- 

 creased, but more rapidly from the fourth to the seventh strips 

 than from the first to the fourth. Its position also shifts somewhat 



