Uranate sodium

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. 

Uranium Arsenide, U3As4, may be obtained i by passing hydrogen over a fused mixture of sodium uranous chloride and sodium arsenide. It is a greyish powder which readily burns in the air. Sometimes it is obtained in a pyrophoric condition. An aluminium-containing product results when the aluminothermic process, using an oxide of uranium and arsenious oxide, is employed. The purest arsenide is obtained, in the crystalline form, when a mixture of hydrogen and arsenic vapour is passed over sodium uranium chloride. It is rapidly decomposed by nitric acid. 

IJmnate. Sodium uranate, uranium yellow, Na2U04, yellow solid, insoluble, formed by reaction of soluble uranyl salt solution and excess sodium carbonate solution. Used (1) in the manufacture of yellowish-green fluorescent glass, (2) in ceramic enamels, (3) as a source of uranium for chemical reactions. 

Alkaline leach mills will use NaOH for final product recovery (in the form of sodium uranate, Na2U207). Often these uranium ore concentrates (yellowcake) are transformed into U3Os by drying at 200°C to remove water and calcining, that is, heating until decomposition. 

Uses.—Uranium compounds are produced as by-products in the extraction of radium, and are consequently available in considerable quantity. They are not, however, as yet employed in industry to any great extent. Sodium uranate, or uranium yellow, is used to a limited extent for colouring glass, to which it imparts a yellow opalescence, and in the ceramic industries, as also is the oxide UjOg in the preparation of yellow, brown, and green glazes. - Certain salts are employed... 

On a commercial scale uranous oxide is prepared by fusing at red heat a mixture of 35 parts of common salt and 20 parts of sodium uranate with 1 part of powdered charcoal, the heating being continued until the escape of gas ceases. After cooling, the mass is lixiviated with water, and the residue of uranous oxide is washed by decantation. By washing with 5 per cent, hydrochloric acid, any iron, aluminium, or vanadium compounds may be removed, and a commercial product of purity equivalent to 97 per cent. U3O3 is obtained. If the uranous oxide is required for the production of ferro-uranium, the complete removal of iron is not necessary. 

Uranous Phosphide, U3P4, is obtained in the form of a black microcrystalline powder by fusing together sodium uranous chloride and aluminium phosphide at 1000° C. in a stream of hydrogen or... 

Uranous Antimonide, UgSb4, is not obtained by the ordinary methods used for the arsenide (see p. 332). By fusing a mixture of sodium uranous chloride, antimony, and aluminium Colani obtained a silvery white mass practically free from aluminium. The product resembled the phosphide and arsenide in properties, and produced vivid sparks when projected into the Bunsen flame. 

Sodium Uranyl Carbonate, Na4U02(C03)g, is obtained by evaporation of a solution of freshly precipitated sodium uranate in sodium bicarbonate solution or by the addition of sodium carbonate in excess to a solution of uranyl acetate. It separates as a yellow crust. 

Table III. Schematic Representation of Lithium and Sodium Uranates (VI) and Transuranates (VI)...

The Haynes-Engle process consists in digesting the coarsely ground ore with a solution of sodium carbonate until the uranium and vanadium are extracted. Sodium hydroxide is added to precipitate sodium uranate and slaked lime to precipitate the vanadium. 

Simple uranyl carbonates arc not known, but double carbonates arc easily formed as, for example, a salt of the composition U02C03 2 NajCOj is obtained as a yellow crust, when freshly precipitated sodium uranate is treated with sodium bicarbonate, or when an excess of sodium carbonate is added to a solution of uranyl acetate. 

Sodium uranate(VI) monohydrate Na3U30,-H30 13721-34-1 662.049 yel powder i HjO s acid... 

Similar products can be formed by reactions of liquid sodium with solid oxides, and some of these reactions are of technical importance. The failure of fuel element canning tubes causes the contact of uranium dioxide fuel with liquid sodium at high temperatures. The stoichiometric UO2 does not react with sodium at temperatures of 400 and 600 °C due to its very high thermodynamic stability. Non-stoichiometric compounds, however, which may contain some UO3 or U3O8, are able to react. In this case, the sodium uranate-V, Na3U04, is formed, a face-centered cubic cell with a = 0.474 nm The same product is formed at temperatures above 550 °C by the reaction... 

Because vanadium pentoxide, V Oj, which coprecipitates simultaneously with sodium uran-ate, is always present in the impure yellow cake, at levels ranging from 5 to 6 wt.%, it must be removed by roasting the impure yellow cake with sodium carbonate at S60°C for 30 min, and after cooling the solid calcinated mass is leached with water to extract the soluble sodium vanadate, NaVOj. The leached product is filtered and the washed yellow cake is dried, while the solution from which vanadium can be recovered is stored. 

Baran, V., and M. Tympl, 1966. Infrared spectra of sodium uranates. Z. fur Anorganische und Allge-meine Chemie 347 175. 

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