SALTS OF NEODYMIUM, PRASEODYMIUM, AND ERBIUM. 77 



NEODYMIUM CHLORIDE IN WATER WITH CALCIUM CHLORIDE AND WITH 

 ALUMINIUM CHLORIDE. (See Plate 62.) 



The concentration of neodymium chloride in all the solutions was the 

 same, namely 0.23. The concentrations of calcium chloride, beginning with 

 the solution adjacent to the numbered scale of A, were 4.29, 3.68, 2.86, 2.29, 

 1.72, 1.14, 0.57, and 0.0; the corresponding concentrations of aluminium chlo- 

 ride in the solutions used in making the negative for B being 2.80, 2.40, 2.00, 

 1.60, 1.20, 0.80, 0.40, 0.00. Depth of absorbing layer throughout, 2.0 cm. 



These dehydrating agents, especially the aluminium salt, introduce con- 

 siderable general absorption in the ultra-violet. This, however, is due to 

 the foreign salt itself, and is in no way to be ascribed to its effect on the 

 neodymium salt in the solutions. This general absorption also accounts for 

 the apparent increase in intensity of the ultra-violet absorption band of 

 neodymium at A 3500. 



The shading on the red side of the yellow band is slightly increased by the 

 addition of calcium chloride, and somewhat more so by the addition of the alu- 

 minium salt. Beyond this no effect on the absorption spectrum of neodymium 

 chloride is produced by even large quantities of these dehydrating agents. 



NEODYMIUM CHLORIDE IN METHYL ALCOHOL BEER'S' LAW. (See Plate 63.) 



The concentrations of the solutions used in making the negative for 

 A, beginning with the one whose spectrum is adjacent to the numbered 

 scale, were 0.50, 0.40, 0.315, 0.25, 0.20, 0.16, and 0.125; the correspond- 

 ing depths of absorbing layer were 6, 7.5, 9.5, 12, 15, 19, and 24 mm. The 

 concentrations for B were, in the same order, 0.20, 0.16, 0.13, 0.10, 0.08, 

 0.06, and 0.05; the depths of cell were the same as used in A. 



There is some absorption in the extreme ultra-violet, which, however, 

 is to be ascribed to the solvent and not to the neodymium chloride. 



No trace of absorption due to the dissolved substance is visible until 

 we reach the group of bands near A 3500. There are three bands having 

 their centers at A 3475, A 3505, and A 3560. Of these the one at ^ 3560 is 

 the widest and also the most intense; the one at A 3475 being somewhat 

 fainter than that at A 3505. The bands are all much wider and hazier 

 than those occurring near the same place in the aqueous solution. No 

 change with dilution indicating a deviation from Beer's law can be detected 

 in these or any of the other bands in the alcoholic solutions of the chloride. 



In the violet and blue regions we find the following : A band at A 4290, 

 about 10 A.U. wide and only moderately intense. At A 4325, a band some- 

 what wider and fainter. At A 4460, a rather wide hazy band with a faint 

 hazy companion towards the violet. This is the band which is perhaps due 

 to praseodymium. The much greater concentration of the alcoholic solu- 

 tions of praseodymium chloride studied in this work makes it impossible 

 to verify this, by seeing whether the praseodymium band in dilute solution 

 really has this general character. 



There are bands at A 4700, A 4780, and A 4825, all of about the same 

 intensity, the one at A 4770 being, however, much narrower than the other 

 two, of which A 4825 is somewhat the wider. Both A 4700 and I 4780 have 

 faint companions to the violet. 



