Ammonium uranates, decompositions

Results of an i.r. study of the thermal decomposition of ammonium uranate have been interpreted in terms of the final self-reduction of the amide as represented by the equation... 

The thermal decomposition of ammonium uranate in flowing hydrogen has been shown to be accompanied by an initial decrease in the surface area of the pellets as the temperature was increased to 100 °C, but thereafter to be accompanied by an increase in the surface area as dehydration occurred. A sudden increase in the surface area at 325 °C was reported to be associated with nitrate decomposition. No significant evolution of ammonia was recorded below 190°C the maximum release of ammonia occurred at 330 °C with decomposition of the ammonium uranate. At 300 °C the predominant phases were identified as ammonium uranate and U03,2H20 with very minor amounts of P-UO3. At 350 °C complete disruption of the ammonium uranate lattice was observed. 

TJranyl nitrate forms double salts of the type E U02(N03)3, where R =K, NH4, Rb, Cs, or Tl. They may be prepared by crystallising a solution of the mixed nitrates in concentrated nitric acid or by crystallisation from a solution of the alkali uranate in excess of nitric acid. The crystals are all anhydrous, and in the case of the potassium salt are orthorhombic, whilst the rubidium and caesium salts are rhombo-hedral and isomorphous with each other. The ammonium salt yields both orthorhombic and rhombohedral crystals. All exhibit a yellowish-green fluorescence they are liygroscopic and readily decomposed by water into their components. The thallium salt is particularly unstable, being decomposed in moist air. On the other hand, the rubidium salt dissolves in water at 80° C. without decomposition. The corresponding salts of sodium, lithium, or of divalent metals have not been prepared. 

---