CHEMISTRY — JONES. 21/ 



It was found that the finer absorption bands are different for the same salt 

 in different solvents, and for different salts of the same metal in the same 

 solvent. There may be a difference in the number of the bands present ; 

 there may be a difference in the intensity and width of the bands, or the 

 difference may be in the wave-lengths of the bands. The different salts of 

 neodymium in the same solvent often give very different absorption spectra, 

 and, what is more important, the same salt of neodymium in different solvents 

 often shows very different spectra. A neodymium salt dissolved in isomeric 

 organic solvents frequently shows absorption lines and bands characteristic 

 of the solvents. This is very important as showing the existence of "solvent 

 bands," on account of the bearing on the solvate theory of solution. 



The absorption spectra of a number of very rare substances were photo- 

 graphed and studied. These were salts of gadohnium, dysprosium, and 

 samarium. Ample quantities of these substances were loaned to Dr. Strong 

 by Urbain, and this phase of the work was thus made possible. 



Dysprosium and samarium salts show very sharp, characteristic absorption 

 bands, which are almost as interesting as those of salts of neodymium. 



The second problem investigated was the spectrophotography of certain 

 chemical reactions, or the changes produced in the spectra while certain 

 chemical reactions are taking place. 



We studied especially the action of oxidizing agents on uranous salts, 

 using both milder and stronger oxidizing agents, and dissolving the uranous 

 salt in single solvents and in mixed solvents. When uranous chloride is 

 dissolved in a proper mixture of water and alcohol, both the "water" and 

 "alcohol" bands come out simultaneously on the plate. While it is true in 

 general that the "water" bands are the most persistent of all the solvent 

 bands, yet a weak oxidizing agent oxidized the "hydrated" salt and left the 

 "alcoholated" salt unaffected. A strong oxidizing agent, on the other hand, 

 oxidized both the "hydrated" and the "alcoholated" salt. This is, therefore, 

 an example of "selective oxidation," or selective action of chemical reagents 

 on solvents, and, so far as is known to the writer, the first example thus far 

 discovered. 



The addition of aluminium and calcium chlorides to solutions of colored 

 chlorides seems to increase the persistency of the alcohol bands relative to the 

 water bands ; and in partial precipitation from unmixed solvents the filtrate 

 sometimes shows the presence of only one solvate. This may be denoted as 

 "selective solvate precipitation." A possible spectroscopic method of deter- 

 mining the relative strengths of acids was pointed out. 



The effect of rise in temperature on the absorption spectra of non-aqueous 

 solutions was studied up to nearly 200°, and this was the third problem inves- 

 tigated during the year. This investigation was carried out in a closed cell 

 devised for the purpose. 



