Of these we may notice libethenite, Cu 2 (OH)PO 4; chalcosiderite, a basic copper iron phosphate; torbernite, a copper uranyl phosphate; andrewsite, a hydrated copper iron phosphate; and henwoodite, a hydrated copper aluminium phosphate.
Various hydrates have been described, but they cannot be formed by precipitating a uranyl salt with an alkali, this reagent giving rise to salts termed uranates.
Change of temperature usually suffices to determine this, though in certain cases a variation in pressure is necessary; for instance, sodium magnesium uranyl acetate, NaMg(UO 2) 3 (C 2 H 3 O 2) 9.9H 2 O shows no change in density unless the observations are conducted under a considerable pressure.
Dilute sulphuric acid attacks it but slowly; hydrochloric acid, especially if strong, dissolves it readily, with the formation, more immediately, of a hyacinthcoloured solution of U 2 C1 6, which, however, readily absorbs oxygen from the air, with the formation of a green solution of UC1 4, which in its turn gradually passes into one of yellow uranyl salt, U02.
Uranyl nitrate is used in photography, and also in analytical chemistry as a precipitant for phosphoric acid (as uranyl ammonium phosphate, U02 NH4 P04).
I a the basic tellurate montanite, Bi 2 (OH) 4 TeO 4; the silicates eulytite and agricolite, B14(S104) 3; and the uranyl arsenate walpurgite, Bi(U02)3(OH)24(As04)4.
If forms two series of salts, one, the uranous compounds, are derived from the oxide U02, the other, the uranyl compounds, contain the divalent group U02.