SPECTROPHOTOGRAPHY OF CHEMICAL REACTIONS. 71 



B, plate 25, is a spectrogram giving the result of the addition of a large 

 amount of acetic acid and a little zinc to uranyl chloride dissolved in acetone. 

 The chemical conditions in this solution are quite complex and, therefore, 

 little can be said about them. The composition of the red uranous band is 

 quite unique in this case. For a considerable amount of the solution the red 

 band resembles that of the red glycerol band of uranous chloride. On decreas- 

 ing the amount of salt the band breaks up into four very weak, diffuse bands, 

 resembling more or less the aqueous uranyl chloride bands. The extreme 

 red part of the absorption consists of a triplet with the central and strongest 

 band located at about X 6750. The other bands are approximately at X 6670 

 and X 6820. The uranyl bands are exceptionally strong, as will be seen from 

 the spectrogram. 



DIRECT SPECTROSCOPIC EVIDENCE FOR THE EFFECT OF MASS. 



According to the law of Mass Action if the salts, uranyl chloride and cal- 

 cium nitrate, were dissolved in water, uranyl chloride and uranyl nitrate would 

 both be present in the solution. According to the theory of aggregates the 

 addition of calcium nitrate should shift the uranyl chloride bands to the violet, 

 while the addition of calcium chloride to uranyl nitrate should shift the uranyl 

 nitrate bands to the red. This was found to take place. 



Preliminary tests showed that the addition of calcium nitrate to uranyl 

 nitrate caused a slight shift towards the violet. It appears, therefore, that 

 calcium has very little effect, it being only the acid radicle that is effective. 

 The result, then, is what would be expected according to the law of Mass 

 Action the effect of adding aluminium chloride to an aqueous solution of 

 uranyl nitrate causes the same shift of the uranyl bands that would be pro- 

 duced if uranyl chloride were added. 



A spectrogram was made of the absorption of uranyl nitrate in water 

 that showed about eight of the uranyl bands, the blue-violet band being about 

 300 Angstrom units in width. The addition of a concentrated solution of 

 calcium nitrate increased the general absorption of the blue-violet band very 

 greatly, so that only the a, b, and c uranyl bands remained. The position 

 and general appearance of these bands did not seem to be changed. Further 

 work of this kind will be done. 



To a solution of uranyl chloride in water a concentrated solution of 

 calcium nitrate was added. The uranyl chloride solution showed the a, b, 

 and c bands, and the blue-violet band was about 400 Angstrom units in width. 

 The addition of the calcium nitrate caused the blue-violet band to be shifted 

 towards t the violet, the shift being greater on the long wave-length edge of 

 the band. The uranyl bands also appear to be shifted towards the violet, 

 although in this particular spectrogram they are so weak that they can hardly 

 be detected. Work of this kind will be done with uranyl sulphate and uranyl 

 nitrate, since the neutral uranyl sulphate bands are quite sharp. The addition 

 of the other salts should also be gradual. 



A, plate 16, represents the spectrophotographs of the addition of increas- 

 ing amounts of calcium nitrate to a uranyl chloride solution in water. The 

 spectrogram shows the gradual shifting of the blue-violet band and the 

 decrease in intensity of the uranyl chloride bands. 



