568 wick. 



solution of praseodymium sulphate, .083 normal concentration, made 

 from material furnished by the Welsbach Company, showed little 

 change when subjected to a pressure of 1700 atmospheres. A nitrate 

 solution made from pure praseodymium oxalate furnished by James, 

 showed a narrowing and intensifying of the components of the broad 

 band with crests at 5882 and 5964. Bands at 4813 and 4688 appeared 

 to have their red sides shifted slightly toward the red but these bands 

 are not sharp and the effect is doubtful. 



From observations made by other observers, it is known that the 

 absorption bands of praseodymium solutions change very little with 

 variations in temperature and concentration in comparison with the 

 changes which occur in solutions of the neodymium salts. 



Erbium Nitrate with Yttrium. 



Erbium nitrate with traces of yttrium in aqueous solution made from 

 material furnished by James, shows an absorption spectrum in which 

 some of the bands are very narrow and sharp. The effect of a pressure 

 of 1500 atmospheres was found to be so small that it appeared uncer- 

 tain as to whether or not any change took place. Bands 6535 and 

 6490 and the very narrow crest at 5231 appeared to be narrowed and 

 intensified by pressure. 



Uranyl Salts. 



Solutions of the uranyl salts were suggested by E. L. Nichols as 

 substances upon which to try the effect of pressure. The absorption 

 bands in aqueous solutions of uranyl potassium sulphate and uranyl 

 ammonium chloride appeared to be made somewhat more distinct 

 by a pressure of 1500 atmospheres but the effect was not pronounced. 



Cobalt Chloride. 



Aqueous solutions of cobalt chloride are well known to be sensitive 

 to variation in temperature, changing from a purplish-red color at 

 room temperature to a decided blue at higher temperatures in the 

 more concentrated solutions. As a result of repeated observations 

 of the absorption spectra of solutions varying from .2 to 1.6 normal, 

 at pressures up to 1500 atmospheres, the conclusion may be drawn 

 that the effect of increasing the pressure is similar to that of lowering 

 the temperature. There is a broad absorption band in the middle 

 part of the visible spectrum with transmission bands at both ends, 



