88 ABSORPTION SPECTRA OF SOLUTIONS. 



Let us consider first the band at A 4275. In the spectrum of the chloride 

 solution this band has the width of only a few Angstrom units and is very 

 intense. In the most concentrated nitrate solution this band has a width 

 of 15 A.U. and its center falls at about A 4280. Its edges are rather hazy, 

 but the band is very symmetrical. With increasing dilution the violet 

 edge increases in intensity, taking more and more the form of a narrow 

 absorption line with center at A 4275; while the red portion of the band 

 decreases in intensity, and at a concentration of 0.38 and a depth of layer 

 of 24 mm. it has taken the form of a slightly hazy band with its center 

 near A 4282. This band is here clearly separated from the more intense 

 and narrower one at A 4275. With a concentration of 0.19 normal and a 

 layer 24 mm. deep, the A 4282 band has become a mere shade on the red 

 side of the A 4275 band; and finally, with a concentration of 0.048 and a 

 24 mm. layer of the solution, it is no longer visible on the photograph. 



At A 4330 or A 4335 the concentrated chloride solutions show a rather 

 wide hazy band, the intensity of which is not sufficient to allow it to be 

 seen in solutions of less than 1.0 normal with a depth of layer of 5 mm. or 

 less. The more dilute solutions of the nitrate used in making A, Plate 70, 

 show this band with about the same intensity and character that it has 

 in solutions of the chloride; while the very concentrated nitrate solutions 

 show it very faintly; that is, the band increases in intensity with dilution. 

 In fact it behaves very much like the A 4275 band, indicating that the two 

 owe their origin to the same "absorber." 



The 3.4 normal chloride solution in a layer 3 mm. deep, shows a band 

 at A 4760, to which the following description applies : Absorption begins 

 at A 4750, rises gradually to a maximum at A 4760, then gradually falls 

 to zero at A 4770. This band remains practically constant throughout the 

 series of solutions used in making B, Plate 59, showing that it is practically 

 unaffected by change in concentration. 



The 2.96 normal solution of the nitrate, with a layer 3 mm. deep, shows 

 a band in the same region which has the following characteristics : Ab- 

 sorption begins at A 4730, rises to a maximum at A 4737, then falls to a 

 slight minimum at A 4742, from which it again rises to a maximum at 

 A 4755, falling off gradually to zero at A 4780, with indications of a faint 

 minimum near A 4765. We really have to deal with a group of three bands 

 then, their centers being approximately at A 4737, A 4755, and A 4772. With 

 dilution the bands at A 4737 and A 4772 rapidly lose their identity, while 

 the band whose center was at A 4755 increases in intensity and somewhat 

 asymmetrically, so that in the solution whose concentration was 0.99, 

 with a depth of layer of 9 mm., there remains but a single band, its center 

 being at A 4760, and shading off towards both sides a little more than the 

 corresponding band in the chloride solution. With increasing dilution 

 this band also becomes more and more like the A 4760 chloride band. 



The chloride solution whose concentration was 1.7 normal, with a 

 layer 3 mm. deep, showed a deep, narrow absorption band at A 5090, and 

 a wide, somewhat hazy one with its center at A 5125. There was a region 

 of transmission between the two about 15 A.U. wide. A, Plate 60, shows 

 that these bands do not change materially with dilution to 0.22 normal. 



