44 



STUDY OF ABSORPTION SPECTRA 



" sol vent" bands when the photographic method was employed. 

 Working in this way, even with the small dispersion of the glass prism, 

 fairly definite indications were obtained of the existence of " hydrate" 

 and "alcoholate" bands. It will, however, be necessary to use a spec- 

 troscope with higher resolving power to bring out more clearly the exist- 

 ence of "solvent" bands. Such a piece of apparatus is now completed. 

 The curves in figure 19 present many interesting features. The 

 intensity of absorption for neodymium chloride in 100 per cent water 

 is much greater than that for neodymium chloride in 100 per cent 

 alcohol. It can be stated, in general, that the intensity of the absorp- 



100 



90 



80 



70 



o 



60 



a 

 J 



a 

 <u 

 o 



& 



50 



40 



30 



20 



10 



NdCI 3 O.I 41 N 

 Depth 10mm 



.70 



.75 .80 



FIG. 19. Wave-lengths. 



.85 



.90 



tion increases as the water-content increases. Neodymium chloride 

 in water has a band whose center is at X = 0.739/4, and here the percent- 

 age transmission is about 29. For neodymium chloride in alcohol it 

 is nearly 50 per cent for the above wave-length. The transmission of 

 neodymium chloride in water for this wave-length of light is therefore 

 about 40 per cent less than the transmission for this same salt in pure 

 alcohol. The ratio of intensities of the hydrate and of the alcoholate 

 bands is about the same at 0.8/4, where the center of the second band 

 for neodymium chloride in water is located. The much less intense 

 neodymium water-band, whose center is at A = 0.875/4, is barely 30 per 



