APPENDIX I. 



CHEMISTRY OF FLUORESCING URANYL SALTS. 



The compounds studied in this work were those uranyl compounds which 

 showed a bright fluorescence. These in general were salts of the stronger 

 acids and usually double salts with the alkali metals. The further general 

 characteristics were high solubility and much water of crystallization, i. e., 

 the more water of crystallization the more intense the fluorescence, as in the 

 case of the lithium manganese acetates. The nonfluorescing compounds of 

 lower valence or those without the "uranyl" oxygen, as well as the sodium 

 carbonate and zinconium oxide solutions of uranic oxide, which, though having 

 peculiar and characteristic absorption, do not fluoresce, were not taken up. 

 The particular groups taken up largely were the nitrates, chlorides, sulphates, 

 and acetates, with potassium, rubidium, csesium, ammonium, and sodium in 

 double salts. The phosphates, fluorides, oxalates, and tartrates and some 

 double salts with the bivalent elements were studied in some cases. 



The material for use in this investigation was obtained at first from Kahl- 

 baum. Later a number (25) of compounds were prepared by G. O. Cragwall 

 in the Chemical Laboratory of Cornell University. The remainder were pre- 

 pared by the authors. Cragwall's material was a large quantity of uranium 

 residue originally from Kahlbaum, during the purification of which by con- 

 version to ammonium diuranate and hen to the chloride the first ammo- 

 nium uranyl chloride crystals with the resolved spectrum were observed. 



The material used by the author was chiefly uranyl nitrate hexahydrate 

 purchased as chemically pure, but which was found to contain noticeable 

 quantities of sodium nitrate crystals. This was dissolved in water, precipi- 

 tated with ammonium hydroxide, washed by decantation to incipient suspen- 

 sion, to which HC1 was added until nearly all the precipitate was dissolved. 

 This leaves most of the iron in suspension if present in small quantities and was 

 used to separate out iron in reworking material contaminated from spatulas, 

 etc. On boiling this solution, if much iron is present it further coagulates 

 and can be filtered, but if the acid concentration is low enough, quite a portion 

 of the uranium separates as H 2 U0 4 . The chloride solution was precipitated 

 again with ammonia, washed, and redissolved in nitric acid. The nitrate was 

 evaporated until the salt (trihydrate) began to crystallize out, and was then 

 carefully heated until decomposition took place, with the formation of the red 

 uranic oxide. Care was taken not to form the black uranous uranic oxide 

 U 3 8 by overheating. The red oxide containing some undecomposed nitrate 

 was digested with water, which converted the oxide into the hydroxide, or 

 acid H2U04, a bright yellow powder. This was washed free from nitrate by 

 decantation and air-dried and formed the major part of the material used. 



Some stock uranyl acetate was used, but as this usually contains sodium 

 acetate also, it is not advisable when preparing sodium-free salts to be com- 

 pared with sodium triple salts. 



Some material was also precipitated as the oxalate, but this does not give 

 complete precipitation, and as it gives the black UsOs on ignition, which is 

 not as readily soluble, it is not of much value except for preparing oxalates. 



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