CHAPTER IX. 

 PRASEODYMIUM SALTS. 



Introduction. Praseodymium chloride. Praseodymium nitrate. 



INTRODUCTION. 



Very little work has been done upon praseodymium compounds, for 

 the reason that the absorption bands are much wider than those of erbium 

 or neodymium. Bois and Elias have worked on Pr 2 (S0 4 ) 3 8H 2 0. At 

 -190 they found bands at XX 5990 to 5993 and XX 6009 to 6014. These 

 bands broadened slightly when a magnetic field of 40,000 c.g.s. units was 

 applied. The widening was much less than that obtained by Becquerel for 

 neodymium bands. 



Jones and Anderson found that the ultra-violet band X 3000 was a 

 "methyl alcohol" band and was very weak for aqueous solutions, if it 

 existed at all. They think that there are other "alcohol " bands, but that 

 they are not far enough separated from the "water " bands to appear by 

 themselves. Similar results are found in the region X 5900. 



Praseodymium Chloride. 



A spectrogram (Plate 31, A) was made of a 2.56 normal aqueous 

 solution of praseodymium chloride 3 mm. deep. Exposures were made to 

 the Nernst glower (current 0.8 ampere and slit-width 0.20 mm.) for 20 

 seconds. The time of exposure to the spark was 4 minutes. Starting with 

 the strip nearest the numbered scale, the temperatures were 7, 23, 40, 

 52, 68, and 84. 



The ultra-violet is absorbed up to X 2700 and this absorption does not 

 vary greatly with temperature, increasing slightly, however. At 7 there 

 are bands from X 4385 to X 4500, X 4640 to X 4720, X 4810 to X 4845, X 6860 

 to X 6990. This latter band is double, the red component being much the 

 narrower and having its center at X 6980. Throughout the remainder of 

 the spectrum there is complete transmission. 



At 84 the absorption bands are located at XX 4380 and 4510, XX 4640 

 and 4730, XX 4810 and 4845, and XX 6870 and 6775. The bands all widen 

 slightly except the latter. At 7 the latter band consisted of two separate 

 bands. At 84 the X 6980 band has diffused into the other band and the 

 general transmission throughout the band has been greatly increased. In 

 this respect this band is very peculiar indeed, and behaves with respect 

 to temperature changes in just the opposite way from practically all other 

 bands investigated. 



A spectrogram (Plate 31, B) was made of a 0.043 normal aqueous solu- 

 tion of praseodymium chloride 196 mm. deep. This spectrogram was to show 

 whether changes due to temperature in the spectrogram were affected by the 

 concentration of the solution. The length of exposures to the Nernst glower 

 (current 0.8 ampere and slit-width 0.20 mm.) was 20 seconds. The length of 



5 65 



