SALTS OF NEODYMIUM, PRASEODYMIUM, AND ERBIUM. 93 



alcoholic solutions, but the greater part of this is perhaps due to the broad- 

 ening, which is somewhat unsymmetrical. 



The band at A 4280 is about 15 A.U. wide and not very intense. The 

 other bands in the violet, blue, and blue-green are so faint as to make 

 measurements impossible. Apparently they agree pretty well in general 

 appearance and position with the corresponding bands in methyl alcohol. 

 However, much deeper layers of the solution than could possibty be used 

 with the apparatus employed in the present investigation would be needed 

 in order to study these bands at all carefully. 



At A 5110 there is a fairly intense, but wide and hazy band. A 5215 is 

 another similar in appearance to the one at A 5110, though not quite as 

 hazy. It is not entirely separated from the much more intense band at 

 A 5255. The latter corresponds to the doublet A 5225 and A 5240 in methyl 

 alcohol, and the hazy band at about A 5235 in ethyl alcohol. Its position 

 is therefore somewhat nearer the red end of the spectrum. 



In the yellow A shows absorption from A 5690 to A 5900. At A 6020 is a 

 moderately intense but rather wide band, which has a fainter and narrower 

 companion at A 6040. 



There is a set of bands in the region A 6100 to A 6300, which seems 

 to increase somewhat in intensity towards the red; but the absorption is 

 too faint to allow the individual bands to be picked out. There is a moder- 

 ately intense but hazy band at A 6760. The spectrum ends near A 7300. 

 B shows the yellow group broken up into two moderately intense but 

 rather wide bands at A 5725 and A 5775, and a much wider and stronger 

 band, with its center at A 5840, which is strongly shaded to both sides. 

 Indications are that this band is at least double, the more intense compo- 

 nent being towards the violet. The spectrum shown in B ends at A 7315, 

 and there is a slight indication that between this point and A 7400 there is 

 a group of three or more bands. 



In general, it appears that as the molecular weight of the solvent is 

 increased the absorption bands become wider and wider. In aqueous 

 solutions there are a number of bands having a width of only a few Ang- 

 strom units, while in methyl alcohol few bands are narrower than from 

 8 to 12 units. In ethyl alcohol no band is narrower than 10 to 15 units, 

 and in the acetone their width is still greater. 



NEODYMIUM NITRATE IN MIXTURES OF METHYL ALCOHOL AND WATER. 



(See Plate 76 A.) 



The concentration of the neodymium nitrate was constant throughout 

 and equal to 0.5 normal. The percentages of water in the solutions, begin- 

 ning with the one whose spectrum is adjacent to the numbered scale, were 

 0, 16.6, 33.3, 50, 66.6, 83.3, and 100 per cent. The common depth of 

 absorbing layer was 0.5 cm. 



The changes here are similar to those discussed in considering Plate 65; 

 that is, the change from the bands characteristic of the aqueous solution to 

 those belonging to the alcoholic solution takes place in passing from the 

 solution containing 16.6 per cent of water to the one containing no water. 

 The spectrogram, however, shows that the spectrum changes consider- 



