Uranyl acetate

Uranyl acetate is the acetate salt of uranium oxide, a toxic yellow-green powder useful in certain laboratory tests. Structurally, it is a coordination polymer with formula UO₂(CH₃CO₂)₂(H₂O)·H₂O.

Uranyl acetate

Uranyl acetate
UO2(H2O)2+[CH3CO−2]2 Hydrated crystal structure
Names
IUPAC name Uranium bis((acetato)-O)dioxo-dihydrate
Other names Uranyl ethanoate; Uranyl acetate dihydrate
Identifiers
CAS Number	(anhydrous): 541-09-3 Y (dihydrate): 6159-44-0 Y
3D model (JSmol)	(anhydrous) ionic form (anhydrate): Interactive image (dihydrate): Interactive image coordination dimer (hydrate): Interactive image coordination dimer (anhydrous): Interactive image
ChemSpider	(anhydrous): 10468551 (dihydrate): 11567664
ECHA InfoCard	100.007.971
EC Number	(anhydrous): 208-767-5
PubChem CID	(anhydrous): 10915
UNII	(anhydrous): 285PN2K1AO Y (dihydrate): KJF3TEU4G6 Y
CompTox Dashboard (EPA)	(anhydrous): DTXSID3060243
InChI (anhydrous): InChI=1S/2C2H4O2.2O.U/c2*1-2(3)4;;;/h2*1H3,(H,3,4);;; Key: IXSMFXMQHOBORU-UHFFFAOYSA-N (dihydrate): InChI=1S/2C2H4O2.2H2O.2O.U/c2*1-2(3)4;;;;;/h2*1H3,(H,3,4);2*1H2;;;/q;;;;;;+2/p-2 Key: VVAHPLNXWRLLIG-UHFFFAOYSA-L
SMILES (anhydrous) ionic form (anhydrate): O=C(C)[O-].[O+]#[U]#[O+].O=C(C)[O-] (dihydrate): CC(=O)[O-].CC(=O)[O-].O.O.O=[U+2]=O coordination dimer (hydrate): O0[C-](C)O[U+6]01(=[O-2])(=[O-2])([OH2])O[C-](C)O[U+6]2(O[C-](C)O2)(=[O-2])(=[O-2])([OH2])O[C-](C)O1 coordination dimer (anhydrous): O0[C-](C)O[U+6]01(=[O-2])(=[O-2])O[C-](C)O[U+6]0(O[C-](C)O0)(=[O-2])(=[O-2])O[C-](C)O1
Properties
Chemical formula	UO2(CH3COO)2 (anhydrous) UO2(CH3COO)2·2H2O (dihydrate)
Molar mass	424.146 g/mol (dihydrate)
Appearance	yellow-green crystals (dihydrate)
Density	2.89 g/cm3 (dihydrate)
Melting point	decomposes at 80 °C (dihydrate)
Solubility in water	7-8 g/100 ml
Solubility	slightly soluble in ethanol[1]
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H300, H330, H373, H411
Precautionary statements	P260, P264, P270, P271, P273, P284, P301+P310, P304+P340, P310, P314, P320, P321, P330, P391, P403+P233, P405, P501
Safety data sheet (SDS)	External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Structure

Structure (from X-ray crystallography) of uranyl acetate dihydrate. Color code: red = O, gray = C, blue = U.

In the polymer, uranyl (UO₂²⁺) centers are bridged by acetate ligands. The remainder of each (heptacoordinate) coordination sphere is provided by an aquo ligand and a bidentate acetate ligand. One water of crystallization occupies the lattice.^[2]

Uranyl carboxylates are known for diverse carboxylic acids (formate, butyrate, acrylate).^[3]

Uses

Uranyl acetate is extensively used as a negative stain in electron microscopy.^[4] Most procedures in electron microscopy for biology require the use of uranyl acetate. Negative staining protocols typically treat the sample with 1% to 5% aqueous solution. Uranyl acetate staining is simple and quick to perform and one can examine the sample within a few minutes after staining. Some biological samples are not amenable to uranyl acetate staining and, in these cases, alternative staining techniques and or low-voltage electron microscopy technique may be more suitable.^{[citation needed]}

1% and 2% uranyl acetate solutions are used as an indicator, and a titrant in stronger concentrations in analytical chemistry, as it forms an insoluble salt with sodium (the vast majority of sodium salts are water-soluble). Uranyl acetate solutions show evidence of being sensitive to light, especially UV, and will precipitate if exposed.^{[citation needed]}

Uranyl acetate is also used in a standard test—American Association of State Highway and Transportation Officials (AASHTO) Designation T 299—for alkali-silica reactivity in aggregates (crushed stone or gravel) being considered for use in cement concrete.^{[citation needed]}

Uranyl acetate dihydrate has been used as a starting reagent in experimental inorganic chemistry.^[5]

Preparation and reactions

The compound can be prepared by treating uranium trioxide with acetic acid:

UO₃ + 2 CH₃COOH + H₂O → UO₂(CH₃COO)₂·2H₂O

The acetate ligands of uranyl acetate can be replaced to give a variety of uranyl complexes.^[6] Uranyl acetate can also be reduced by zinc to give the uranium(IV) acetate (U(OAc)₄).^[7]

Safety

In general, uranium salts exhibit nephrotoxicity. Normal commercial stocks from depleted uranium have typical specific activity 0.37–0.51 microcuries per gram (14–19 kBq/g), too weak to harm from outside the body.^[8] However, uranyl acetate is very toxic if ingested, inhaled as dust, or absorbed through cut or abraded skin.^{[citation needed]}

Microbiologists have developed a number of alternative stains:^[9] neodymium acetate,^[10][11] platinum blue,^[12] hafnium chloride,^[13] and oolong tea extracts.^[14][15]