Gallium

1871
Dmitrii Ivanovich Mendelev predicts the existance and properties of the element
after zinc in the periodic table. He Gives it the name "eka aluminium".

1875
Paul Emile Lecoq de Boisbaudran discovers gallium.
Its properties closely match those predicted by Mendelev.


Gallium, atomic number 31, is very similar to aluminum in its chemical
properties. It does not dissolve in nitric acid because of the protective film of
gallium oxide that is formed over the surface by the action of the acid. Gallium
does however dissolve in other acids, and alkalies.

Gallium was discovered (1875) by Paul Emile Lecoq de Boisbaudran, who observed
its principal spectral lines while examining material seperated from zinc blende.
Soon after he isolated the metal studied its properties, which coincided those that
Dmitrii Ivanovich Mendelev had predicted a few years earlier for eka-aluminium, the
then undiscovered element lying between aluminum and indium in his periodic table.

Though widely distributed at the Earth's surface, gallium does not occor
free or concentrated in independant minerals, except for gallite. It is extracted as
a by-product from zinc blende, iron pyrites, bauxite, and germanite.

Silvery white and soft enough to be cut with a knife, gallium takes on a bluish
tinge because of superficial oxidation. Unusual for its low melting point
( about 30 degrees C, 86 degrees F ), gallium also expands upon solidification and
supercools readily, remaining a liquid at temperatures as low as 0 degrees C ( 32 degrees F ).

Gallium has the longest usefull liquid range of any element. The liquid metal
clings to glass and similar surfaces. The crystal structure of gallium is orthorhombic.
Natural gallium consists of a mixture of two stable isotopes: gallium-69 ( 60.4 percent )
and gallium-71 (39.6 percent ).

Somewhat similar to aluminum chemically, gallium slowly oxidizes in moist air
until a protective film forms, and it becomes passive in cold nitric acid.

Gallium has been considered as a possible heat-exchange medium in nuclear reactors,
although it has a high neutron cross section. Radioactive gallium-72 shows some promise
in the study of bone cancer; a compound of this isotope is absorbed by the cancerous
portion of the bone.

The most common use of gallium is in a gallium scan. Gallium scans are often used
to diagnose and follow the progression of tumors or infections. Gallium scans can also be
used to evaluate the heart, lungs, or any other organ that may be involved with inflammatory
disease.

A gallium scan usually requires two visits to the Nuclear Medicine Department.
On the first day you recieve an injection in a vein in your arm, you will then be scheduled
to return beetween 2 and 5 days later, depending on your diagnosis. Your initial scan can
take several hours, while you lay on a stretcher, or imaging table, and a camera is positioned
above you or below you, taking pictures as it moves slowely along the length of your body.
No special preperation must be taken before the scan, and the gallium is usually excreted
through the bowel.