Uranyl acetate is the

acetate An acetate is a salt formed by the combination of acetic acid with a base (e.g. alkaline, earthy, metallic, nonmetallic or radical base). "Acetate" also describes the conjugate base or ion (specifically, the negatively charged ion called ...

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

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.

Structure

In the polymer,

uranyl The uranyl ion is an oxycation of uranium in the oxidation state +6, with the chemical formula . It has a linear structure with short U–O bonds, indicative of the presence of multiple bonds between uranium and oxygen. Four or more ligands may ...

(UO₂²⁺) centers are bridged by

acetate ligand Transition metal carboxylate complexes are coordination complexes with carboxylate (RCO2−) ligands. Reflecting the diversity of carboxylic acids, the inventory of metal carboxylates is large. Many are useful commercially, and many have attracted ...

s. The remainder of each (heptacoordinate) coordination sphere is provided by an

aquo ligand In chemistry, metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts, such as metal nitrates, sulfates, and perch ...

and a bidentate acetate ligand. One water of crystallization occupies the lattice.

Uses

Uranyl acetate is extensively used as a negative stain in

electron microscopy An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...

."Negative Staining"
University of Oxford 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 Low-voltage electron microscope (LVEM) is an electron microscope which operates at accelerating voltages of a few kiloelectronvolts or less. Traditional electron microscopes use accelerating voltages in the range of 10-1000 keV. Low voltage imaging ...

technique may be more suitable. 1% and 2% uranyl acetate solutions are used as an

indicator Indicator may refer to: Biology * Environmental indicator of environmental health (pressures, conditions and responses) * Ecological indicator of ecosystem health (ecological processes) * Health indicator, which is used to describe the health o ...

, and a titrant in stronger concentrations in

analytical chemistry Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separati ...

, as it forms an insoluble salt with

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

(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. 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. Uranyl acetate dihydrate has been used as a starting reagent in experimental inorganic chemistry.

Related compounds

Uranyl carboxylates are known for diverse carboxylic acids (formate, butyrate, acrylate).

Safety

Uranyl acetate is both radioactive and toxic. Normal commercial stocks prepared from depleted uranium have a typical

specific activity Specific activity is the activity per unit mass of a radionuclide and is a physical property of that radionuclide. Activity is a quantity (for which the SI unit is the becquerel) related to radioactivity, and is defined as the number of radi ...

of per gram. This mild level of radioactivity is insufficient to be harmful while the material remains external to the body. However, this reason has still lead others to find alternatives, such as neodymium acetate, platinum blue and

oolong Oolong (, ; (''wūlóngchá'', "dark dragon" tea)) is a traditional semi-oxidized Chinese tea (''Camellia sinensis)'' produced through a process including withering the plant under strong sun and oxidation before curling and twisting.Zhongguo ...

tea extracts.He X, Liu B (2017) Oolong tea extract as a substitute for uranyl acetate in staining of ultrathin sections based on examples of animal tissues for transmission electron microscopy. J Microsc 267:27–33 Uranyl acetate is very toxic if ingested, inhaled as dust or by skin contact if skin is cut or abraded. The toxicity is due to the combined effect of chemical toxicity and mild radioactivity and there is a danger of cumulative effects from long term exposure. Uranium salts are predominantly nephrotoxic.

References

{{Acetates Electron microscopy stains Uranyl compounds Nuclear materials Acetates