Ammonium uranyl arsenate

TJranyl Pyroarsenate, (U02)2As207, remains as a yellow powder when the arsenate, U02HAs04.4H20, or ammonium uranyl arsenate (see below), is heated.7... 

Wilson and Lewis developed a method for arsenic, which includes precipitation as ammonium uranyl arsenate and subsequent ignition under controlled conditions to triuranium octaoxide. Phosphate and vanadate form similar insoluble ammonium uranyl salts and, in their presence the method is not applicable. 

Uranium minerals may be obtained in solution, in a suitable condition for estimation, by the following process. The ore is dissolved in aqua regia, or, if necessary, fused with alkali bisulphate and extracted mth hot hydrochloric acid. After evaporation to drjmess, the residue is taken up with dilute hydrochloric acid, and the solution saturated with hydrogeir sulphide in order to remove any copper, lead, bismuth, arsenic, antimony, or any other metal yielding an insoluble sulphide. The filtrate is concentrated and treated with ammonium carbonate, which precipitates the carbonates of the alkaline earths, iron, and most of the rare earths. The filtrate is neutralised by hydrochloric acid, evaporated to dryness, and the residue ignited to drive off ammonium salts, and then redissolved in dilute acid. The remaining rare earths, and particularly thorium, are next precipitated by the addition of oxalic acid. The filtrate, which contains the uranium in the uranyl condition, may now be precipitated by any of the methods described above. 

Arsenates. Arsenic acid and ammonium, sodium and potassium arsenate precipitate uranium as uranyl metal arsenate. Silver, titanium, zlrconliun, thorium and lead Interfere. Separation Is made from the alkali metals, alkaline earths, aluminum. Iron (ll), and rare earths. Including trlvalent cerium.-2 ... 

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