NEODYMIUM SALTS. 



81 



The spectrogram shows that Beer's law does not hold, the more con- 

 centrated solutions being the greater absorbers. This is especially true of 

 the alcoholic portion of the absorption. In strip 1 the " alcoholic " band 

 corresponding to the " water " band X 4274 has about the same intensity 

 as the " water " band. In strip 4, however, the " alcohol " band has become 

 very weak, indeed, while the water-band has slightly increased in absolute 

 intensity as compared with strip 1. Several other bands indicate the same 

 change. The " alcohol " bands thus weaken in intensity as the concen- 

 tration is decreased, while the " water " bands do not. 



In this connection experiments are now in progress in which it will be 

 tested whether changes in temperature, the addition of chemical reagents, 

 etc., affect the different bands in the same way. 



Plate 43, B, represents the effect of adding hydrobromic acid to an 

 aqueous solution of neodymium acetate. The first strip represents the 

 absorption of a solution of neodymium acetate in water to which about a 

 drop of hydrobromic acid has been added. Strip 2 represents the same to 

 which several more drops of hydrobromic acid have been added. The 

 remaining strips represent the absorption of the same solution to which 

 more and more hydrobromic has been added. 



The first strip gives the characteristic acetate spectrum. In order to 

 ?ive the effect of the acid the wave-lengths of the bands of the acetate meas- 

 ured on the film itself are given and compared with the spectrum of strip 2. 



Strip 1. 



4290 

 4450 



4715 



4775 



Strip 2. 



3465 

 3510 

 3543 

 3560 

 4285 

 / 4445 1 

 1 4460 f 

 4705 

 4775 



Strip 1. 



4800 to 5150 

 gen. absorp. 



5240 



5745 

 5760 



5790 

 5825 

 5870 



Strip 2. 



4830 

 5105 

 5140 

 5225 

 5240 

 5740 

 5760 

 5775 



5810 



The effect of adding a very small amount of hydrobromic acid is very 

 pronounced. The addition of larger amounts of hydrobromic acid has 

 ray little effect. The shifting effect of hydrobromic acid is very small as 

 compared with the same effect produced by nitric acid on the nitrate. The 

 3resence of a large amount of hydrobromic acid does not make the bands 

 lazy and wide. 



Plate 44, A, represents the effect of adding hydrochloric acid to an 

 iqueous solution of neodymium acetate. The first strip represents the 

 ibsorption of the pure aqueous solution of the acetate. The second strip 

 epresents the absorption of the same to which one drop of hydrochloric 

 icid has been added. The third strip represents the absorption of the 

 solution to which two more drops of acid have been added. The acid used 

 was concentrated. The following table represents in part the changes 

 vhich the addition of acid has caused to take nlac.p.. 



