Gallium
So I could completely bore you with facts like
solid gallium is a blue-gray metal and that pure gallium is a very
silvery color. I could tell you that its melting point is 29.8 °C,
that it has 6 isotopes and that its atomic mass is 69.72 g.mol
-1. But you wouldn't really care about any of that, or
remember it, would you?
So instead, let's talk about some of its more
interesting features, like the fact that it is soft enough to be
cut with a knife and dissolves in acids and alkalis. What else can
I tell you about it? Read on!
Applications
Liquid gallium wets porcelain and glass surfaces;
it forms a bright, highly reflective surface when coated on glass.
It can be used to create brilliant mirrors. Gallium easily alloys
with most metals, so it is used to form low-melting alloys. The
plutonium pits of nuclear weapons employ an alloy with gallium to
stabilize the allotropes of plutonium.
Analog integrated circuits are the most common
application for gallium, with optoelectronic devices (mostly laser
diodes and light-emitting diodes) as the second largest end use.
Gallium has semiconductor properties, especially as gallium
arsendite (GaAs). This can convert electricity to light and is used
in light emitting diodes (LEDs) for electronic display and
watches.
Gallium in the environment
Gallium does not exist in pure form in nature,
and gallium compounds are not a primary source of extraction.
Gallium is more abundant than lead but much less accessible because
it has not been selectively concentrated into minerals by any
geological process, so it tends to be widely dispersed. Several
ores, such as the aluminum ore bauxite, contain small amount of
gallium, and coal may have a relatively high gallium content.
Health effects of gallium
Gallium is an element found in the body, but it
occurs in a very small amount. For example, in a person with a mass
of seventy kilograms, there are 0.7 milligrams of gallium in the
body. If this amount of gallium was condensed into a cube, the cube
would only be 0.49 millimeters long on one side. It has no proven
benefit towards the function of the body, and it most likely is
only present due to small traces in the natural environment, in
water, and in residue on vegetables and fruits. Several vitamins
and commercially distributed waters have been known to contain
trace amounts of gallium with less than one part per million. Pure
gallium is not a harmful substance for humans to touch. It has been
handled many times only for the simple pleasure of watching it melt
by the heat emitted from a human hand. However, it is known to
leave a stain on hands. Although it is not harmful in small
amounts, gallium should not be purposefully consumed in large
doses. Some gallium compounds can actually be very dangerous,
however. For example, acute exposure to gallium(III) chloride can
cause throat irritation, difficulty breathing, chest pain, and its
fumes can cause even very serious conditions such as pulmonary
edema and partial paralysis.
Environmental effects of gallium
One controversy with gallium involves nuclear
weapons and pollution. Gallium is used to hold some nuclear bomb
pits together. However, when the pits are cut and plutonium oxide
powder is formed, the gallium remains in the plutonium. The
plutonium then becomes unusable in fuel because the gallium is
corrosive to several other elements. If the gallium is removed,
however, the plutonium becomes useful again. The problem is that
the process to remove the gallium contributes to a huge amount of
pollution of water with radioactive substances. Gallium is an ideal
element to use in the bomb pits, but pollution is destructive to
the earth and to the health of its inhabitants. Even if efforts
were taken to remove the pollution from the water, it would
significantly increase the costs of the procedure of turning
plutonium into a fuel by about 200 million dollars. Scientists are
working on another method to clean the plutonium, but it could take
years to be completed.