Barium uranate

Barium Uranate, BaU04, is formed by fusing together barium chloride and urano-uranic oxide, or by mixing solutions of barium chloride and uranyl chloride and passing in excess of ammonia. The reaction in the latter case proceeds according to the equation ... 

BBr2[g] BORON DIBROMIDE (GAS) 108 BaU04 BARIUM URANATE 158... 

Barium uranium oxide (barium uranate), BaU702, is uranium... 

Barium uranate(IV) or barium uranium oxide (BaU702) which is orange or yellow in colour may be related to uranium yellow and orange pigments (qq.v.). It is thought perhaps to have been used in the late nineteenth and/or early twentieth century. Modem synthesis is described by Allpress (1964) and Klima c/a/. (1966). 

For the treatment of camotite several methods are available. The method recommended by the United States Bureau of Mines2 is as follows The ore is leached with concentrated nitric acid at 100° C., neutralised with caustic soda, and barium chloride and sulphuric acid added to the solution to precipitate the radium as barium-radium sulphate. The precipitate settles in three or four days, after which time the clear liquid is decanted into tanks and is treated with excess of boiling sodium carbonate solution in order to precipitate any iron, aluminium and chromium present. The solution now contains sodium uranyl carbonate and sodium vanadate. It is nearly neutralised with nitric acid, and caustic soda is added in sufficient quantity to precipitate the uranium as sodium uranate. After filtering, the remaining solution is neutralised with nitric acid and ferrous sulphate added, whereupon iron vanadate is thrown down. By this method it is claimed that 90 per cent, of the radium, all the uranium, and 50 per cent, of the vanadium in the camotite are recovered. 

It is formed in solution by oxidising uranous chloride with nitric acid by dissolving uranic oxide in concentrated hydrochloric acid or by adding barium chloride to a concentrated solution of uranyl sulphate until precipitation is complete. Its aqueous solution on evaporation yields the monohydrate, UOaClj.HaO." The solution is unstable at ordinarj temperatures and slowly deposits uranic hydroxide, which after a time partly redissolves. The uranyl chloride may be reduced in solution to black uranous oxide by the action of magnesium or aluminium powder. The densities of aqueous solutions of uranyl chloride have been determined as follows ... 

Calcium Uranate, CaUO, and calcium diuranate, CaUaO , are similar to the corresponding barium salts and may be prepared by similar methods. The diuranate is highly refractory and does not fuse at red heat. 

Magnesium Uranate, MgU04, and magnesium diuranate, MgUjOy, may be obtained by the methods described for the barium salts. The diuranate yields yellowish-green needle-shaped crystals. 

Strontium Uranate, SrUOi, and strontium diuranate, SrU207, are similar in properties and are prepared by similar methods to the corresponding barium and calcium salts. 

Both uranium(VI) and plutonium(VI) form oxoanions. Uranium gives mono-, di-, tri-, tetra-, penta- and hexa-uranates the common diuranates, MgUgOy, correspond only formally to the dichromates. Barium hydroxide precipitates the triplutonate, BaPugO o, from solutions containing PuOg. ... 

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