SPECTROPHOTOGRAPHY OF CHEMICAL REACTIONS. 65 



of the uranous sulphate solution oxidized by hydrogen peroxide, showing that 

 probably some uranyl aggregate is formed that contains some N0 3 groups. 



The addition of the first amount of nitric acid causes the transmission 

 in the ultra-violet to be increased very greatly, with the appearance of a large 

 number of the uranyl bands. In the red the wide uranous sulphate band is 

 decreased in intensity. Strips 2 and 3 show the narrow red sulphate water 

 band, but in strip 4 this band has completely disappeared and is replaced 

 by a single weak band 300 Angstrom units wide. 



B, plate 45, represents the change in the absorption spectrum of a solu- 

 tion of uranous chloride in methyl alcohol and acetone, to which nitric acid 

 is added. This spectrogram shows the rapid disappearance of the alcohol 

 bands. The various uranous bands seem to be replaced by the bands of 

 some hydrate of a uranous nitrate aggregate, and this aggregate is then grad- 

 ually oxidized. The ultra-violet transmission increases until the last strip, 

 which shows a very great increase in the ultra-violet absorption. The last 

 strip still shows the presence of a considerable amount of uranous salt, and 

 the absorption bands are entirely new. 



A, plate 37, represents the absorption spectrum of uranous chloride as it 

 is gradually changed into uranous nitrate by the addition of nitric acid. B, 

 plate 37, represents the corresponding changes in the absorption spectra that 

 take place, when to a solution of uranous chloride in equal parts of water and 

 methyl alcohol is added nitric acid also dissolved in equal parts of water and 

 methyl alcohol. The upper strip represents the absorption of the resultant 

 uranyl salt after oxidization with hydrogen peroxide. As the bands are quite 

 wide and strong most of the changes can be seen on the plate itself. It will be 

 seen that the absorption spectrum of the nitric acid solution of uranous chlo- 

 ride is very different from that of the neutral chloride. This spectrogram also 

 seems to indicate that there is not a gradual shifting of the chloride bands 

 into the nitrate bands, but in the case of the X 6300 chloride band there is a 

 decrease in intensity without being shifted; and this is replaced by the uranous 

 nitrate band at about X 6100. B shows that the addition of nitric acid results 

 in a rapid and almost complete disappearance of the alcohol bands, while the 

 uranous nitrate water bands increase in intensity. 



URANOUS ACETATE AND THE EFFECT OF THE ADDITION OF 



NITRIC ACID. 



The reduction of uranyl acetate to the uranous salt is not complete, and 

 a precipitate was formed, so that the resultant solution here used was quite 

 dilute. A spectrogram (B, plate 36) was made of this solution, and the first 

 four strips represent the absorption of layers of different thicknesses, for the 

 last layer this being about 20 cm. To this solution were added 10, 20, and 40 

 drops of concentrated nitric acid, the absorption being represented by strips 

 6, 7, 8. The first five strips represent quite well the absorption of uranous 

 acetate, and they also show very clearly the uranyl acetate bands. The 

 addition of nitric acid causes a great increase in the general transmission 

 throughout the spectrum, and a very rapid decrease in the intensity of the 

 uranous bands. The resultant uranous bands are, of course, those of uranous 

 nitrate. This spectrogram shows that uranous acetate is quickly oxidized 

 in the presence of nitric acid, whereas this is not the case with uranous chloride. 



5 



