280 



JONES AND ANDERSON— ABSORPTION SPECTRA OF [April 25, 



A Character. 



4740-4770 Fairly sharp edges. 

 4820 Hazy on violet side. 



5000-5330 Red limit sharp, violet a little 



hazy. 

 5660-5930 Violet limit- sharp. Red edge 



hazy. 

 6235 First and strongest band in 



orange group. 

 6260 Narrow and rather faint. 



6270-6310 Faint band. 

 6360-6390 Faint band. 

 6730 Faint, in shading of principal 



red band. 

 6770-6840 Principal red band. Edges 



hazy. 

 6890 Band with hazy edges. 



7250 End of transmission. 



Remarks. 



Not afifected by dilution. 



Due at least partly to prase- 

 odymium. 



Violet shading a little greater 

 in concentrated solutions. 



Shading on red side decreases 

 with dilution. 



Not affected by dilution. 



Not affected by dilution. 

 Not affected by dilution. 

 Not affected by dilution. 

 Not affected by dilution. 



Not affected by dilution. 



Not affected by dilution. 

 Not affected by dilution. 



The most marked change produced by dilution from 3.4 to 1.7 

 normal, excepting that in the red shading of the A 5660-5930 band, 

 is that taking place on the red side of the narrow absorption line 

 at A 4275. In the spectrum of the most concentrated solution the 

 red edge of this line falls at A 4280, from which place a uniform 

 absorption extends to A 4295. In the third spectrum, counting from 

 the numbered scale, the shading has almost completely disappeared, 

 leaving a very narrow line at approximately A 4290. The width of 

 this line is only 2 or 3 A. U. and it persists with unchanged intensity 

 throughout the remaining strips of the spectrogram. Its intensity 

 is, however, not sufficient to make it show in the reproduction, and 

 not even great enough to make it visible on the negative for b, 

 plate I. 



The limits of transmission for the yellow band, as shown by the 

 spectrum of the most concentrated solution, are A 5660 and A 5950; 

 hence the narrowing of its red side amounts to 20 A. U. 



b, plate I, starts at the same concentration as a, but the effective 

 depth of absorbing layer is only one-fourth of that used in a. 

 Hence this spectrogram represents the spectrum of a solution of 

 neodymium chloride 24 mm. deep and having a concentration of 

 0.43 normal. The absorption bands are all much narrower, and 



