212 



FLUORESCENCE OF THE URANYL SALTS. 



solution above 40 per cent the so-called 7 form or monopotassium salt will 

 appear. In the 1 of uranyl nitrate to 2 of potassium nitrate, the double 

 nitrate crystallizes only above 50 per cent of nitric acid, and as the d phase or 

 the dipotassium salt and the metastable phase at this concentration is the 7 

 form. Presumably at higher concentrations of potassium nitrate the last- 

 found and undetermined form would appear. 



Grams of solute in 100 grams of solvent. 



Solid phases appearing are: 

 Potassium nitrate, KNOs. 

 Ammonium nitrate, NH 4 NOs. 



Uranyl nitrate hexahydrate, UCMNOs^ 6H 2 O, Hex. 

 Monopotassium uranyl nitrate, KUO 2 (NO 3 )3, y. 

 Dipotassium uranyl nitrate, K 2 UO2(NOs) 4 , 5. 

 Monoammonium uranyl nitrate, NH 4 UO2(NC>3)3, /3. 



From solutions 1 molecule of uranyl nitrate to 1 of ammonium nitrate, 

 uranyl nitrate hexahydrate crystallizes unless the per cent of nitric acid is at 

 least 50, above which the /3 or monoammonium form crystallizes, which is 

 metastable practically to water solution. From 2 molecules of ammonium 

 nitrate to 1 of uranyl the hexahydrate crystallizes up to 40 per cent, above 

 which the /3 form appears, which is also metastable to pure aqueous solution. 

 It will be noted that while potasisum nitrate is about as soluble as uranyl 

 nitrate and the phase in equilibrium with the more acid solutions corresponds 

 to the composition of the solution, the ammonium nitrate is much more solu- 

 ble and not only does not form the solid phase in case uranium is present, 

 but does not form the diammonium salt from solutions of that composition. 

 Laboratory experience showed that a large excess of ammonium nitrate and 



