PREFACE. 



This investigation, which is a continuation of the work of Jones and 

 Uhler on the absorption spectra of solutions (Carnegie Publication No. 60), 

 was carried out with the aid of a Grant generously awarded by the Carnegie 

 Institution. Salts of the following metals were brought within its scope: 

 Cobalt, nickel, copper, iron, chromium, neodymium, praseodymium, and 

 erbium; and about 1,200 solutions were studied. 



Spectrograms of salts of these metals in water, varying the concen- 

 tration but keeping the total amount of coloring matter in the path of the 

 beam of light constant, were obtained. In a similar manner spectrograms 

 were made, keeping the total number of molecules in the path of the beam 

 of light constant. The effect of such dehydrating agents as calcium chloride 

 and aluminium chloride, on absorption in solution, was also studied. 



A large number of salts were rendered anhydrous and dissolved in 

 methyl alcohol, ethyl alcohol, and acetone. The concentration of the solu- 

 tions in these solvents was varied, but the total amount of coloring matter 

 in the path of the light was kept constant. Finally, water was added to 

 the non-aqueous solutions, and its effect on absorption determined. 



Perhaps the most striking result was obtained with anhydrous neodym- 

 ium chloride in alcoholic solutions, to which small, increasing amounts of 

 water were added. Here entirely new bands appeared on the addition of a 

 small amount of water. 



An ample supply of the salts of neodymium and praseodymium was 

 furnished us with their characteristic liberality by the Welsbach Light 

 Company, and our thanks are especially due to their chemist, Dr. H. S. 

 Miner. 



We accept this opportunity to extend our thanks to Prof. J. S. Ames, 

 who has placed at our disposal the ideal conditions under which this inves- 

 tigation was carried out. 



HARRY C. JONES. 



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