Uranium tungstate

Uranium Tungstate. -When ammonium tungstate is added to a solution of uranium tetrachloride, a brownish-green ijrecipitate of composition U(W0,).2.W0g.6H20 is obtained. This compound is used in... 

Yttrotantalite, -which is found at Ytterby and other parts of Sweden, and in Norway. It is richer in tantalum than in niobium, and contains considerable proportions of yttrium, erbium, cerium, and uranium, together with calcium, iron, etc.2 Tungstates and stannates are also present. 

In the belief that the action of the enzyme might be modified by the presence of some of the more prevalent metals in trace amounts, the effects of cations on mammalian /3-glucuronidase were re-investigated186 195 of a large number studied, only Cu , Ag , and Hg were pronounced in their effects. (Inhibition was also seen with uranium acetate, ammonium chloroplatinate, osmium tetroxide, and sodium tungstate.83) Marked inhibition was seen with 2.5 X 10-6 M of Ag and 1.5 X 10 6 M of Hg00, and inhibition by these two ions was reversed by tissue constituents. 

Uranium-doped tungstates with ordered perovskite structure having compositions A2BWi xUx06 have been used for a detailed study of the luminescence properties of the octahedral uranate group 10-13,21,22,25) pgj alkaline-earth ions Ca " ", Sr , Ba i have been used the B ions were the alkaline-earth ions, or Cd ". This type of compounds is particularly suited for such a study in view of the high site symmetry of the hexavalent ions in compounds with this structure and because of the fact that only one crystallographic site can be occupied by hexavalent uranium (c.f. Sect. 1). 

In the excitation spectra of the uranium-doped tungstates several broad uranate excitation bands are observed at room temperature. The lowest energy excitation band is ascribed to a 127gu 477 magnetic dipole allowed transition. The zero... 

Section 3.2 provides information about the vibrational structure which is observed in the luminescence spectra of uranium-doped tungstates with ordered perovskite structure at low temperatures. 

Since the zero-phonon lines of the emissions of several uranium-doped tungstates are broadened compared with the zero-phonon Une peaking at 500.4 nm in the emission spectrum of Ba2MgW06—U, we conclude that the broadening of the lines in the vibronic spectra might be due to the fact that the emission in these compounds originates from various slightly different uranate centres. 

UFg complex in the spectrum indicates a distortion of the excited state, possibly by Jahn Teller interaction ). In contrast with observations that have been made in the emission spectra of uranium-doped tungstates no vibronic origins due to coupling with i 3 and 1 4 vibrational modes have been observed in the emission spectrum of 5% UFg/WFg crystals. 

C. M. Toume, G. Tourne, and M. C. Brianso, Cesium uranium germanium tungstate,... 

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