Module 101 Properties of Uranium
The lower oxidation states, UO2 and U3O8, tend to
be dark brown or black. The higher oxidation states,
UO3 and UO4, are generally orange or yellow,
especially in solution or if water or crystallization
are present (e.g., UO4·2H2O). Furthermore, the
higher oxides usually flake of more easily and are
usually more soluble in water. Being flaky, they are
more easily inhaled. Being more soluble, they are
more easily absorbed into the body.
Uranyl compounds, such as uranyl nitrate, or
UO2(NO3)2, are chemical forms of uranium that are
often found in solution with water. They are
generally yellow in color and are used in criticality
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Uranium reacts readily with air and water. For
example, when uranium is machined, small chips
catch fire from the heat of the machining process.
Shavings placed in water react to produce hydrogen
gas. The surfaces quickly oxidize to a hard black
coating that is at first protective; however, under
adverse conditions, it corrodes and flakes.
Uranium also reacts with hydrogen or tritium gas to
form uranium hydride (UH3). Uranium "beds" are
commonly used to store tritium.