92 ABSORPTION SPECTRA OF SOLUTIONS. 



In the yellow, A shows absorption from A 5700 to X 5870, shading off 

 towards the red, with a band at X 5965. B shows a band at A 5720, which 

 is perhaps double; deep absorption from A 5755 to A 5845, with faint bands 

 at A 5760 and A 5835, and a very intense band at A 5790. 



The spectrum ends near A 7320 in a band, which does not seem espe- 

 cially intense. 



NEODYMTUM NITRATE IN ETHYL ALCOHOL BEER'S LAW. (See Plate 74.) 



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 0.32, 0.26, 0.20, 0.16, 0.13, 0.10, and 0.08, and for B they were in the 

 same order, 0.16, 0.13, 0.10, 0.08, 0.06, 0.05, and 0.04; the corresponding 

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



The solutions used in making A of this plate had the same concentra- 

 tions as those used in making B of Plate 73, and as the depths of absorbing 

 layer were also the same, the two plates are directly comparable. 



The two spectra are very similar, but nevertheless there are some well- 

 marked differences. The bands at A 5225 and A 5240, which were quite 

 sharp and intense in the methyl alcohol solution, here show simply as one 

 hazy band of moderate intensity, its middle being near A 5235. Even in 

 B, where the concentration is much less, this band does not break up into 

 two, but simply diminishes in intensity without change of character. 



The yellow group shows a wide, faint band at A 5730, a moderately 

 intense band at about A 5790, much less intense and sharp than in methyl 

 alcohol. There is a pair of poorly defined bands at A 5825 and A 5845, 

 apparently corresponding to the band at A 5835, observed in the solutions 

 in methyl alcohol. 



The spectrum ends at A 7315 in a band which is not very intense or 

 sharp. In general, the absorption in the two alcohols is about the same, 

 the tendency being for all absorption bands to be narrower in the methyl 

 alcohol than in the ethyl alcohol solutions. 



NEODYMIUM NITRATE IN ACETONE BEER'S LAW. (See Plate 75.) 



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 0.60, 0.48, 0.37, 0.30, 0.24, 0.19, and 0.15. For B they were 

 0.19, 0.15, 0.12, 0.095, 0.075, 0.060, and 0.047; the depths of absorbing 

 layer were in both cases 6, 7.5, 9.5, 12, 15, 19, and 24 mm. 



The nitrate was found to be much more soluble in acetone than in ethyl 

 alcohol, being in this respect quite different from the chloride, which, when 

 anhydrous, dissolves quite readily in ethyl alcohol, but scarcely at all in 

 acetone. 



The spectrum in the ultra-violet ends at about A 3300, as is usual in 

 acetone solutions. The bands in the ultra-violet absorption near A 3500 

 have the positions A 3475 and A 3555, are both rather faint, and have a 

 width of about 15 or 20 A.U. They are hence both wider and fainter than 

 they were in the methyl alcohol solution. Their position is apparently 

 about 10 A.U. nearer the red end of the spectrum than was the case in the 



