114 



A STUDY OF THE ABSORPTION SPECTRA. 



from the neutral nitrate bands to the neutral sulphate bands, approxi- 

 mately. There is in this case a gradual shift of the bands to the red. 



Plate 79, B, represents the effect of adding hydrochloric acid to an 

 aqueous solution of uranyl nitrate. The depth of cell was 15 mm. The 

 concentration of the uranyl salt was kept constant. The percentages of 

 acid were increased. 



In the first strips the b and c bands are very weak. They become 

 stronger and shift gradually to the red. The other bands are quite sharp 

 until the last strip, where they appear very weak. Their wave-lengths are 

 but slightly changed. In the above table the wave-lengths of the neutral 

 chloride and nitrate bands are taken from the other tables. Strip 1 of this 

 plate and strip 1 of Plate 81, B, are entirely different. 



Plate 83, B, represents the absorption spectra of uranyl nitrate to 

 which acetic acid had been added. Plate 82, A, represents the same effect, 

 except that here the original uranyl nitrate solution was only 1 mm. in 

 thickness; so that the ratio of acetic acid to the amount of uranyl salt was 

 much larger. 



The first effect which the addition of acetic acid produces is to shift 

 slightly the uranyl bands of the nitrate to the red, and to cause them to 

 become much sharper. When some twenty times as much strong glacial 

 acetic acid had been added as was equivalent to the uranyl nitrate solu- 

 tion, the uranyl bands became quite weak, and shifted very greatly 

 towards the red, as is shown in Plate 82, A. The e and / bands are each 

 shifted nearly 200 Angstrom units. When this enormous shift towards 

 the red takes place a new band appears between /and g. This new band 

 will be called/,. Further addition of acetic acid causes the uranyl bands 

 to become stronger again, producing at the same time a small shift to 

 the red. 



