Uranyl arsenates

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

AS2O8U (s) U02(As03)2 (s) Uranyl Arsenate AS2O8U (s) U02(As03)2 (s)... 

AS2O11U2 (s) (U02)2AS207 (S) Uranyl Arsenate AS2O11U2 (s) (U02)2AS207 (s)... 

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. 

The uranyl phosphate chain in the structure of Cu2[(U02)(P04)2] is topologically identical to the uranyl arsenate chain found in walpurgite [104], Copper occurs in sixfold (4+2) coordination as elongated tetragonal bipyramids to form face-sharing chains that extend along the [010] direction. The chains of Cu polyhedra share vertices with adjacent phosphate tetrahedra of the parallel uranyl phosphate chains (Fig. 25). 

Gross E. B. et al. Heiiu-ichite and metaheinrichite, hydrated barium uranyl arsenate minerals. Am. Miner., 43, 1958, 1134-43. 

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