1909.] OF VARIOUS SALTS IN SOLUTION. 227 



slightly broader. The bands that have widened appreciably are 

 AA5195 to 5260 and AA5700 to 5880. The change in the absorption 

 is greatest when the temperature is changed from 68° to 83°. Up 

 to 68° there is practically no change in the absorption spectrum at all. 



A spectrogram (B, Plate XII.) showing the effect of temperature 

 was made, using an aqueous solution of .055 normal concentration 

 of neodymium bromide, the depth of the layer being 197.4 mm. 

 This spectrogram was made to compare with that taken with a 1.66 

 normal concentration of the same salt and a depth of layer of 6 mm. 

 The exposures to the Nernst glower lasted 90 sec. in this case, 

 current 0.8 amperes and slit width of 0.20 mm. The length of ex- 

 posure to the spark was 6 mins. Starting with the strip nearest to 

 the comparison scale the temperatures of the solution were 5°, 16°, 

 29°, 42°, 55°, 68° and 84°. 



At 5° there is practically complete transmission of light between 

 A 3400 and A 2600, no ultra-violet bands appearing, as was the case 

 for the more concentrated solution. The bands AA4445, 4^93, 4760, 

 4825 and 5095 were somewhat sharper than they were in the con- 

 centrated solutions. The two largest bands extended from A 5200 

 to A 5250 and from A 5710 to 5850. As in the case of the more 

 concentrated solution, so here, the greatest change in the absorption 

 took place in the change from 68° to 84°. The ultra-violet absorp- 

 tion increased up to A 2900. The bands at A 3500 became consider- 

 ably stronger, but they widened very little. The bands AA4445, 

 4693, 4760 and 4825 are somewhat weaker than at 5°. The wide 

 bands remained practically as wide as at 5°, A 5200 to A 5250 and 

 A 5705 to 5870. This indicates a widening of about 25 Angstrom 

 units for the latter band. For the more concentrated solution the 

 widening of these two bands was 25 and 40 Angstrom units re- 

 spectively. It is thus seen that in the more concentrated solutions 

 the bands widen more with rise in temperature than they do in the 

 less concentrated solutions. At 42° in the dilute solution there ap- 

 pears a narrow band at A 6710. This increases in intensity with 

 rise in temperature. This band does not appear at all in the con- 

 centrated solution. 



A spectrogram (A, Plate XIII.) was made of neodymium chlo- 

 ride and calcium chloride in water. Exposures were made for 30 sec. 



