SUMMARY AND GENERAL DISCUSSION OF RESULTS. 95 



confusion has been caused in the past by the fact that most of the uranous 

 salts contain uranyl salts mixed with them, and, therefore, their absorption 

 spectra include the uranyl bands. The complete independence of the two 

 sets of bands is very clearly shown on spectrograms of the absorption spectra 

 of a uranous salt as it is gradually oxidized to the uranyl salt by the addition 

 of hydrogen peroxide. 



(1) A problem of considerable interest, and one for which an answer 1 has 

 been partly obtained, is the complete correlation of the a, b, c, etc., bands 

 when one uranyl salt is transformed into another salt, or when the solvent 

 is changed. Thus, for instance, the a band could be traced from the nitrate 

 to the sulphate, acetate, etc., and also for these salts in various solvents. It 

 may be that the neodymium, erbium, and samarium bands can be studied 

 in the same manner, especially at low temperatures. The results of such a 

 study should extend very greatly our knowledge of chemical reactions. 



(2) If uranyl chloride and calcium nitrate are dissolved in water, uranyl 

 chloride and uranyl nitrate should both be present in the solution. In terms 

 of the theory of aggregates, then, it would be expected that the addition of 

 calcium nitrate to an aqueous solution of uranyl chloride would cause the 

 uranyl chloride bands to shift towards the violet. On the other hand, the 

 addition of aluminium or calcium chloride to an aqueous solution of uranyl 

 nitrate should cause the uranyl nitrate bands to shift towards the red. The 

 experimental results verify these conclusions. 



Preliminary spectrograms showed that the addition of calcium nitrate 

 to an aqueous solution of uranyl nitrate caused the uranyl nitrate bands to 

 shift slightly towards the violet, the amount of the shift, however, being very 

 small. This seems to show that calcium itself has very little if any effect upon 

 the absorption, and this is in agreement with the results of Becquerel and 

 others. 



(3) When an acid is added to a neutral uranyl salt in sufficient quantity, 

 this salt is changed to a salt of the acid added. Up to the present no quanti- 

 tative study of the strengths of acids by the spectroscopic method has been 

 made, but by means of radiomicrometric measurements this method should 

 give a reasonably accurate means of measuring the relative strengths of vari- 

 ous acids, especially in aqueous solutions. 



(4) The modus operandi by which uranyl salts are transformed into 

 uranous, and vice versa, is not known. This subject has, however, been dis- 

 cussed in the chapter dealing with the spectrophotography of chemical reac- 

 tions. It seems probable that there is not the usual dynamic equilibrium 

 between the uranyl and uranous salts 



AGGREGATES AND THEIR PROPERTIES. 



(1) The presence of free acid or of foreign salts 2 has been found to change 

 the frequency of many of the uranyl, uranous, and the neodymium bands. 

 At present our knowledge of these effects is practically restricted to aqueous 

 solutions, although similar effects are known to occur in other solvents. An 

 example of the above effect is that of the uranyl chloride and nitrate bands. 



1 Publication 130, Carnegie Institution of Washington. 

 2 Phys. Zeit., II, 668 (1910), 12, 269 (1911). 



