Chemistry Reference
In-Depth Information
for renal toxicity involves the accumulation of urani-
um in the tubular epithelium and subsequent irritation
that progresses to damage and necrosis on the basis of
exposure level and duration. This may be associated
with increased cellular oxidative stress, altered expres-
sion of genes involved in cell signaling, and inhibited
sodium-dependent phosphate and glucose transport
systems. The impact on liver enzymes and receptors
might affect drug therapy regimens. Uranium can also
interfere with bone remodeling and liver integrity. The
health effects from exposure by normal routes are pri-
marily to the kidney, and this damage has been shown
to be reversible. Even before efforts began to produce
uranium for nuclear weapons and energy production
purposes, uranium was recognized for its ability to in-
duce nephritis in laboratory animals. Less severe effects
have been observed for the liver, lung, nervous, and re-
productive system. Cancer is not expected, because it
has not been observed in high-dose human and animal
studies. If it should occur, bone sarcomas are regarded
as the most likely to occur, because uranium and radi-
um deposit long term in bone, and radium dial painters
developed bone sarcomas.
and named after the planet Uranus. It occurs with a
typical natural abundance of 2-4 ppm (mass fraction
of 2-4 × 10
−6
) in the crust. The highest concentrations in
the United States are found in the four corners region
(Arizona, Colorado, New Mexico, and Utah), whereas
the highest on earth to date are in Canada (>25% ura-
nium by mass). The most active mines are in Canada,
Russia, that region's independent states (Kazakhstan,
Ukraine, and Uzbekistan), Australia, and Central Africa
(Namibia, Niger, and South Africa). A series of mining,
milling (through acid leach or alkali roast), and puri-
fi cation steps produce a mixture of oxides that can be
reduced to form a silvery white metal that is malleable,
ductile, slightly paramagnetic, and almost as dense as
tungsten. Three metallostructural confi gurations are
known (orthorhombic, tetragonal, or body-centered
cubic). Like aluminum, it reacts in air to produce a pro-
tective oxide coating. The metal powder is pyrophoric,
igniting at elevated temperatures in air, CO
2
, and N
2
to
form the oxide, carbide, and nitride, respectively. The
periodic table places uranium in the actinide series of
elements, and similarly, it can exist in any of six oxi-
dation states (0, +2, +3, +4, +5, and +6). The +4 state
is relatively stable and is associated with hydroxides,
phosphates, and fl uorides. The +6 state is the most sta-
ble when present as octaoxide (U
3
O
8
or yellow cake),
but as hexafl uoride it dissociates rapidly on contact
with liquid water or water vapor in air. These last two
states are the most relevant to human exposure and
commercial efforts. Table 1 summarizes the chemical
1 PHYSICAL, CHEMICAL,
AND RADIOLOGICAL PROPERTIES
Uranium (U) was discovered in 1789 by the Ger-
man chemist Martin Heinrich Klaproth (1743-1817)
TABLE 1
Chemical and Physical Properties of Uranium and Compounds
Uranium
Uranium
Uranium
Uranium
Uranyl
Uranyl
Uranyl
Property
Uranium
dioxide
trioxide
octa-oxide
tetra fl uoride
hexafl uoride
fl uoride
nitrate
At./Mol weight
238.029
270.03
286.03
842.08
314.02
352.02
308.03
502.13
Formula
U
UO
2
UO
3
U
3
O
8
UF
4
UF
6
UO
2
F
2
UO
2
(NO
3
)
2
Color
Silvery
Brown-
Yellow-
Dk olive
Green
Colorless
Pale
Yellow
Black
red
green
yellow
Dec
a
Dec
a
Dec
a
Dec
a
Melting Pt (°C)
1135
2878
960
Sublimes
at NTP
b
at 1300
at 300
at 100
NR
c
NR
c
NR
c
NR
c
Boiling Pt (°C)
4131
No data
No data
56.2
Vss
d
Dec
a
Solubility in
Insol
Insol
Insol
Insol
Sol
Miscible
water
Solubility
Acids
HNO
3
HNO
3
,
HNO
3
,
Conc
CC1
4
,
Ethanol
Ethanol
other
HCI
H
2
SO
4
base/acid chloroform
Density (g/cm
3
)
18.95
10.96
7.29
8.30
6.70
4.68 at 21°C
6.37
2.81 at 13°C
Conv
e
(pCi/
µ
g)
0.67
0.59
0.56
0.57
0.45
0.45
0.52
0.32
a
dec, Decomposes.
b
NTP, Normal temperature and pressure.
c
NR, Not relevant.
d
Vss, Very slightly soluble.
e
Conv, Mass to radioactivity conversion (based on isotopic ratio in undisturbed crustal rock).
Adapted from ATSDR (1999).
