SALTS OF NEODYMIUM, PRASEODYMIUM, AND ERBIUM. 



73 



than about 1.5 normal Beer's law seems to hold very accurately indeed, 

 with the exception of the shading towards the red accompanying the band 

 near X 5800, which seems to decrease somewhat with dilution for concen- 

 trations of normal or less. 



In the following table the measurements of the positions of the bands 

 were made on the seventh strip of A, Plate 59, and, therefore, refer to a 

 concentration of 1.7 normal with a depth of layer of 24 mm. The remarks 

 referring to changes with dilution apply to a change in concentration from 

 3.4 to 1.7 normal, the depths of layer being so varied that the product of 

 concentration and depth remains constant. 



Character. 



Remarks. 



2810 



2890-2910 

 2970-2995 



3220-3330 

 3380-3400 



3435-3595 

 4180 

 4275 

 4290 



4330 

 4410-4465 



4580-4050 

 4G65-4710 



4740-4770 



4820 

 5000-5330 



5660-5930 

 6235 



6260 



6270-6310 

 6360-6390 



6730 

 6770-6840 



6890 



7250 



Faint transmission begins. 

 Band with well-defined sharp edges. 

 A double band, strongest component to 

 violet. 



Strong band of complete absorption, 



sharp edges. 

 Rather faint band. Most intense 



towards red. 

 Complete absorption. Edges sharp. 



Hazy, not very intense 



Very intense and sharp 



Narrow and faint 



Hazy. 



Edges rather hazy. 



Band with hazy edges, not completely 



separated from 4665-4710. 

 More sharply defined on red than on 



violet side. 



Fairly sharp edges 



Hazy on violet side 



Red limit sharp, violet a little hazy. . . . 



Violet limit sharp. Red edge hazy. . . . 

 First and strongest band in orange 

 group. 



Narrow and rather faint 



Faint band 



Faint band 



Fault. In shading of principal red band . 



Principal red band. Edges hazy 



Band with hazy edges 



End of transmission 



The observed narrowing with dilution per- 

 haps due largely to general U.V. absorp- 

 tion. 



Narrows slightly with dilution. 



Narrows somewhat with dilution. 



Narrows considerably at first. 



Between this and A 4275 is fairly strong ab- 

 sorption in the most concentrated solution. 

 This absorption has disappeared in the 

 spectrum measured. 



This band is coincident with band due to 

 praseodymium, and is to be ascribed to 

 this element, which had not been com- 

 pletely separated from the neodymium. It 

 does not change with dilution. 



Narrows slightly with dilution. 



Partly due to praseodymium. Does not 



change with dilution. 

 Not affected by dilution. 

 Due at least partly to praseodymium. 

 Violet shading a little greater in concentrated 



solutions. 



Shading on red side decreases with dilution. 

 Not affected by dilution. 



Do. 

 Do. 

 Do. 

 Do. 

 Do. 

 Do. 

 Do. 



The most marked change produced by dilution from 3.4 to 1.7 normal, 

 excepting that in the red shading of the X 5660 to X 5930 band, is that tak- 

 ing place on the red side of the narrow absorption line at X 4275. In the 

 spectrum of the most concentrated solution the red edge of this line falls 

 at X 4280, from which place a uniform absorption extends to X 4295. In 

 the third spectrum counting from the numbered scale, the shading has 

 almost completely disappeared, leaving a very narrow line at approximately 

 X 4290. The width of this line is only 2 or 3 A.U., and it persists with 

 unchanged intensity throughout the remaining strips of the spectrogram. 

 Its intensity is, however, not sufficient to make it show in the reproduc- 

 tion, and not even great enough to make it visible on the negative for B, 

 Plate 59. 



