54 



ATLAS OF ABSORPTION SPECTRA. 



174. Neodyniium Ammonium Nitrate 

 Continued. 

 which were plane and parallel. 

 The cell was successively adjusted 

 to the following depths, viz : 0.53, 

 0.83, 1. 13, 1.43, 1.73, 2.03, 2.33, 

 and 2.63 cm. In other words, the 

 thickness of the absorbing layer 

 was increased by 3 mm. between 

 the successive photographic ex- 

 posures. As has been often re- 

 marked by other observers, the so- 

 lution in question has a large num- 

 ber of unusually narrow absorption 

 bands, some of which are very in- 

 tense and persistent. 



For the depth of 0.53 cm. all of the 

 ultra-violet is absorbed from o.20/t 

 to the zinc line at 3302.7, while for 

 the depth of 2.63 cm. only very 

 faint transmission obtains in the 

 immediate vicinity of 3407.7 A. U. 

 The general characteristics of the 

 most intense bands can be readily 

 seen by referring to fig. 96, hence 

 it will suffice to give the approxi- 

 mate wave-lengths of the absorp- 

 tion bands which were recorded 

 by the original negative. 



The centers of the bands were at 

 0.347/i, o.350;a, 0.355^^, 0.381JH, very 

 faint ; 0.418;^, faint ; 0.4275/x, sharp ; 

 0.433/^. very faint; 0.4437/*. dif- 

 fuse ; 0.461/i, faint and diffuse ; 

 0.4695^^, 0.4755^, faint; 0.4823/x, 

 0.S087/X, 0.51121H, with a hazy 

 boundary at the less refrangible 

 side; o.520yu, 0.5225/i, broad and in- 

 tense ; 0.5324/x, faint ; o.577S/i, broad 

 and intense, and 0.5925/u,, faint and 

 diffuse. 



Fig. 97 shows the absorption of the 

 same solution when placed in the 

 wedge-shaped cell. The angle of 

 the liquid wedge was 1 18' and 

 the depth increased linearly from 

 0.71 mm. to 1.24 mm. Except for 

 the transmission of the strong 

 metallic lines at 2558.0, 2573.1, and 

 2748.7, the ultra-violet absorption 

 is practically complete as far as 

 0.3250/i. The negative for fig. 97 

 recorded very faintly all of the ab- 

 sorption bands given above except 

 the ones at 0.347/1, 0.350/i, 0.381/*, 

 0.418/1, 0.461, and 0.5324/4. 



174. Neodymium Ammonium Nitrate 



Continued. 

 The angle of the cell was 39' for fig. 

 98, so that the thickness of the 

 absorbing layer varied from about 

 o to 0.36 mm. Absorption was 

 complete from o.20/i to 0.237/1. The 

 boundary of this region of ab- 

 sorption curved around rather 

 abruptly from 0.237/1 to 0.250/4 as 

 the depth of solution increased 

 from its least to its greatest value. 

 Transmission by the deepest part 

 of the liquid wedge was weakened 

 somewhat from 0.277/1 to 0.308/1. 

 Only the intense absorption band 

 at wave-length 5225 A. U. was re- 

 corded by the negative. 



175. Nickel Nitrate. 

 Fig. 81, pi. 21. 



Green crystals. In solution green, 

 light green. 



Saturated. 



Angle, about 6. Depth o to 3.2 mm., 

 approximately. 



Strong absorption in the orange and 

 red, also weaker absorption in the 

 extreme violet. The absorption 

 was nearly complete from 0.20/1 

 to about 0.312/4. The end of this 

 region of absorption curved 

 around from 0.312/1 to 0.326/1 with 

 increasing depth of solution. Un- 

 usual transparency from 0.326/x to 

 0.374/4. A symmetrical absorption 

 band, with its maximum at 0.391/t, 

 extended from 0.374/1 to 0.408/4. 

 Transmission was complete from 

 this point as far as the absorption 

 band in the orange. The sloping 

 end of the spectrogram calls atten- 

 tion to absorption in the orange. 



176. Nickel Sulphate. 

 Fig. 82, pi. 21. 



Green crystals. In solution green, 

 pale green. 



Saturated. 



Angle, about 6. Greatest depth, 3.2 

 mm., approximately. Absorption 

 in the extreme violet, orange, and 

 red. Using the faint comparison 

 spectrum as a standard of com- 

 parison, it becomes evident that 

 the solution was remarkably trans- 

 parent to the ultra-violet radia- 

 tions from 0.226/4 to about 0.365/4. 

 A symmetrical absorption band, 



