SALTS OF NEODYMIUM, PRASEODYMIUM, AND ERBIUM. 75 



The band which in the table is recorded as X 4740 to A 4770 has in B, 

 Plate 59, become a slightly hazy band having its middle at A 4760. Its 

 intensity is intermediate between that of the bands at A 4695 and A 4825, 

 and, hence, like them may be seen faintly even in B, Plate 72. 



The band which in A, Plate 59, has the limits A 5000 to A 5330 breaks up 

 into a rather complicated series of bands on dilution, some idea of which 

 may perhaps be gained from the following : B, Plate 59, shows some ab- 

 sorption throughout the region given, but with a deep, narrow band at 

 A 5090 and faint transmission at A 5100 and in the region A 5150 to A 5180. 

 Absorption is complete from A 5105 to A 5150, and from A 5180 to A 5270. 

 There is again incomplete absorption from A 5270 to A 5330, with indica- 

 tion of a band at A 5315. In A, Plate 60, the general shading has the limits 

 A 5050 to A 5330, and it shows the following : A narrow intense band at 

 A 5090; wide, hazy band at A 5125; a pair of very intense, narrow bands 

 at A 5205 and A 5222; very narrow band at A 5255; and faint, hazy band at 

 A 5315. B, Plate 60, shows the shading diminished very much in intensity, 

 and all the bands except the doublet A 5205 to A 5222 rather faint. The 

 absorption in the doublet is still almost complete. B, Plate 72, still shows 

 the doublet very strong, the remaining absorption bands faint, although 

 still visible. 



The limits of the yellow band in B, Plate 59, are A 5700 to A 5880 in the 

 strip corresponding to the most concentrated solution. The band narrows 

 by 30 Angstrom units on this spectrogram, the narrowing being due to a 

 decrease in the shading towards the red, with decrease in concentration. 

 In B, Plate 60, the limits of the band are A 5710 and A 5840. There is still 

 considerable shading, but it decreases only very slightly with dilution. 

 The band begins to show its structure, but not well enough to allow any 

 measurements to be made. 



In B, Plate 60, and B, Plate 72, the band has broken up into the fol- 

 lowing smaller bands : A 5725, narrow and moderately intense. A 5745 

 and A 5765, double band, not clearly resolved, the red component being 

 more intense than the violet. This double band is the most intense of the 

 group. A 5795, band having about the same intensity as the one at A 5725, 

 but being much wider and hazier. A 5380, very faint band. 



The group of absorption bands in the orange, given in the table, may 

 be seen faintly in B, Plate 59, and very faintly in A, Plate 60; but, like the 

 group in the red near A 6800, it shows no further breaking up into more 

 complicated bands on dilution. 



B, Plate 59, shows that the spectrum ends at A 7310 in what appears 

 to be an absorption band. In Plate 60, and B, Plate 72, it is seen that 

 there is a very intense, narrow band at A 7325; another narrow but fainter 

 band at about A 7350, and a wide, moderately intense band at A 7390 or 

 A 7400, beyond which the plates were not sufficiently sensitive to give any 

 appreciable photographic action with the length of exposure used. 



The most intense bands of neodymium chloride, and hence the ones 

 which would be most conspicuous in a very dilute solution, are the follow- 

 ing : A 3465, A 3540, A 4275, A 5205, A 5225, A 5745, A 5765, and A 7325. 



The wave-lengths of all the bands are collected in the following table, 

 together with a brief description of the appearance of each band. It is to 



