THE ABSORPTION SPECTRA OF NEODYMIUM CHLO- 

 RIDE AND PRASEODYMIUM CHLORIDE IN WATER, 

 METHYL ALCOHOL, ETHYL ALCOHOL AND 

 MIXTURES OF THESE SOLVENTS. 



(With six plates.) 



Twenty-first Communication. 



By harry C. JONES and JOHN A. ANDERSON. 



{Read April 25, 1908.) 



(This is a preliminary report on part of an investigation carried out with the 

 aid of a Grant from the Carnegie Institution of Washington.) 



The absorption spectra of salts of cobalt, nickel, copper, iron, 

 chromium, neodymium, praseodymium and erbium have been stud- 

 ied in the present investigation. Of these the salts of neodymium 

 and praseodymium are perhaps the most interesting and important. 

 This is due to the large number of absorption bands shown by these 

 substances, and, further, to the very unusually sharp character of 

 these bands. 



The method employed in making the spectrograms consists in 

 allowing light from a spark, or from a Nernst filament, to pass 

 through the solution in question, fall upon a grating and then upon 

 the photographic plate. 



For visual work a small direct vision grating pocket spectroscope 

 was found very convenient and useful. For photographing the 

 spectra the vertical grating spectroscope used by Jones and Uhler^ 

 was employed. 



In making the photographs the Seed L-ortho film was used for 

 the region from A 2000 to about X 6000. 



For photographing the red end of the spectrum a Wratten and 

 Wainwright panchromatic glass plate was used. 



^Carnegie Publication No. 60. 



276 



