78 A STUDY OF THE ABSORPTION SPECTRA. 



more diffuse than at 9, but this change is very small. The bands from 

 X 4200 to X 5000 seem to be slightly shifted towards the red at the higher 

 temperatures. In all, this shift, however, is not greater than 2 or 3 Ang- 

 strom units. 



Neodymium Salts in Glycerol. 



A run was made to test whether Beer's law holds for glycerol solutions. 

 Plate 35, A, represents a spectrogram ranging from 0.84 to 0.105 normal, 

 the amount of absorbing matter being kept constant. The more dilute 

 solutions show greater general absorption in the ultra-violet. Otherwise 

 Beer's law is found to hold. 



Plate 43, A, is the spectrogram of a solution of neodymium chloride 

 in glycerol taken in the silica cell at various temperatures. The plate 

 shows a slight widening of the bands, but this is very small. Some of the 

 finer bands indicate a slight shift towards the red with rise in temperature. 

 This, however, is quite small and never amounts to more than 3 or 4 

 Angstrom units for any band. 



Plate 46, A, shows the effect of rise in temperature of solutions contain- 

 ing neodymium and aluminium or calcium chlorides in glycerol. In the 

 third and fourth strips it is to be noticed that the wide band at X 5800 is 

 shifted slightly to the red. The band at about X 4295 seems to be shifted 

 2 or 3 Angstrom units to the red. The shift is very small and is obscured 

 in part by the increased diff useness of the bands at the higher temperature. 



Plate 29, B, represents the effect of rise in temperature on the absorp- 

 tion spectra of pure neodymium chloride in glycerol. The shift of the bands 

 in this case can hardly be noticed. The effect of the presence of calcium 

 is to cause the temperature shift of the bands to be increased. The effect 

 is not as great as it is in aqueous solutions. 



The absorption spectrum of neodymium chloride (Plate 34, A and B) 

 in glycerol is very similar to that of an aqueous solution. The ultra-violet 

 bands XX 3475 and 3550 are quite strong and sharp. A weak band appears at 

 X 3520. For the 3 mm. depth of cell and smallest concentration the follow- 

 ing bands appear: XX 4290 (weak), 4710 (very weak), 5120 (wide, hazy, and 

 apparently a triplet), 5230, 5240 (strong and fairly sharp), 5250, 5270 (weak 

 and fuzzy), 5740 (wide and hazy), 5790, 5805, 5820, and 5850. The latter 

 three bands practically merge into a single band, the transmission between 

 them being very weak. 



The greatest concentration and the 9 mm. depth of cell (upper strip 

 of Plate 34, A) shows several additional bands: XX 3600, 4190 (very diffuse), 

 4288, and two very fine components at 4270 and 4305, 4330, 4345, 4365, a 

 wide (50 Angstrom units) band at 4460, and similar but weaker bands at 

 4620, 4840, 5340, 5940, 6240, 6265, 6400, 6800, with narrower and sharper 

 bands at 4710, 4730, 4760, 4790, 5170, and 5190. 



The "glycerol " bands are very similar to the "water " bands but are 

 all of slightly greater wave-length. The sharp "water " band at X 4274 is 

 composed of three bands in the glycerol solution. The "glycerol " bands 

 are quite persistent and for a solution containing 10 per cent water the 

 bands are practically "glycerol" bands. In general, the "water" and 

 " glycerol " bands are so close to one another that we can not tell whether 



