Chemical Properties
Gallium is a lustrous, silvery liquid, metal, or
gray solid.
Chemical Properties
light grey solid
General Description
GALLIUM(7440-55-3) is a silvery-white liquid at room temperature. Ingestion of this material may be toxic. GALLIUM(7440-55-3) is corrosive to aluminum. If exposed to high temperatures, GALLIUM(7440-55-3) may emit toxic fumes which may form a corrosive alkaline solution with water. GALLIUM(7440-55-3) is soluble in most acids and alkalis. GALLIUM(7440-55-3) is used as a semiconductor material.
Reactivity Profile
Metals, such as GALLIUM METAL, are reducing agents and tend to react with oxidizing agents (i.e. hydrogen peroxide). Their reactivity is strongly influenced by their state of subdivision: in bulk they often resist chemical combination; in powdered form they may react more rapidly. Reacts violently with chlorine and other halogens at ambient temperatures [Bretherick, 5th Ed., 1995].
Air & Water Reactions
Stable in dry air, in moist air GALLIUM tarnishes
Health Hazard
Inhalation of vapors or contact with substance will result in contamination and potential harmful effects. Fire will produce irritating, corrosive and/or toxic gases.
Potential Exposure
A potential danger to those involved
in preparing such semiconductor compounds as gallium
arsenide. Used in light-emitting diodes, batteries, and
microwave equipment.
Fire Hazard
Non-combustible, substance itself does not burn but may react upon heating to produce corrosive and/or toxic fumes. Runoff may pollute waterways.
First aid
Eye Contact: Immediately remove any contact
lenses and flush with large amounts of water for at least
15 minutes, occasionally lifting upper and lower lids. Skin
Contact: Remove contaminated clothing. Wash contami nated skin with water. Breathing: Remove the person from
exposure. Begin (using universal precautions, including
resuscitation mask) if breathing has stopped and CPR if
heart action has stopped. Transfer promptly to a medical
facility. If swallowed, do not induce vomiting. Medical
observation is recommended for 24 to 48 hours after
breathing overexposure, as pulmonary edema may be
delayed. As first aid for pulmonary edema, a qualified med ical professional might consider administering a corticoste roid spray. Cigarette smoking may exacerbate pulmonary
injury and should be discouraged for at least 72 hours
following exposure. If symptoms develop or overexposure
is suspected, chest X-ray should be considered.
Shipping
UN2803 Gallium, Hazard class: 8; Labels:
8-Corrosive material.
Incompatibilities
Incompatible with oxidizers (chlorates,
nitrates, peroxides, permanganates, perchlorates, chlorine,
bromine, fluorine, etc.); contact may cause fires or explo sions. Keep away from alkaline materials, strong bases,
strong acids, oxoacids, and epoxides such as lyes, halogens,
and alloys of aluminum. Contact with hydrogen chloride/
hydrochloric acid or hydrogen peroxide may result in
explosion. Corrosive on contact with metals. Moisture,
oxygen, and air sensitive.
Description
Gallium is the 32nd most abundant element and constitutes
0.0005% of the Earth’s crust. It is found most commonly in
association with zinc, germanium, and aluminum and is found
primarily in the mineral germanite. Gallium(III) is the primary
oxidation state for gallium compounds; its chemistry resembles
that of aluminum(III).
Waste Disposal
Use a licensed professional
waste disposal service to dispose of this material. Dissolve
or mix the material with a combustible solvent and burn in
a chemical incinerator equipped with an afterburner and
scrubber. All federal, state, and local environmental regula tions must be observed.
Isotopes
There are 33 isotopes of gallium, two of which are stable. They are Ga-69, whichmakes up 60.108% of the element’s presence in the Earth’s crust, and Ga-71, which contributes39.892% of the gallium found in the Earth’s crust. All the other 31 isotopes areradioactive with half-lives ranging from a few nanoseconds to about 15 hours.
Origin of Name
Latin word Gallia, meaning “Gaul,” an early name for France.
Occurrence
Gallium is the 34th most abundant element, but it is not widely distributed as an elementalmetal. It is usually combined with other elements, particularly zinc, iron, and aluminum ores.It is found in diaspore, sphalerite, germanite, gallite, and bauxite. Although small amounts arerecovered from burning coal used for heating or generation of electricity, it is mostly recoveredas a by-product from the production of ores of other metals. Gallium is about as abundant aslead in the Earth’s crust.
Since 1949, the Aluminum Company of America has extracted gallium metal from aluminumbauxite ore. In the past gallium had few uses. Only recently, with the development ofmicroprocessors, chips, computer, and the like, has gallium found many profitable uses.
Characteristics
Gallium is truly an “exotic” element in that it has so many unusual characteristics. It canform monovalent and divalent as well as trivalent compounds. It is considered a “post-transitionalmetal” that is more like aluminum than the other elements in group 13. It has fewsimilar characteristics to the two elements just below it in group 13 (In and Ti).
Gallium reacts strongly with boiling water, is slightly soluble in alkali solutions, acids,and mercury, and is used as an amalgam. It has some semiconductor properties but only if“doped” with elements in group 14, such as As, P, and Sb. It is also used as a “dope” for othersemiconducting elements.
Production Methods
Most of the world’s gallium is produced in the United States.
The metal is recovered by controlled electrolysis of the concentrated
alkaline liquors that are by-products of the extraction
of aluminum and zinc from their ores. The purification of
bauxite by the Bayer process results in the concentration of
galliumin the alkaline solutions of an aluminum:galliumratio
of 5000:300. Electrolysis using a mercury electrode gives a
further concentration and further electrolysis using a stainless
steel cathode of the resulting sodium gallate affords liquid
galliummetal.Ultrapure (99.9999%)galliumfor semiconductor
electronics is obtainedby repeated fractional crystallization
of themetal.Gallium is relatively expensive because of its low
concentration inmostminerals and because the metalmust be
extremely pure for most applications.
Purification Methods
Dissolve the metal in dilute HCl and extract it with Et2O. Bubbling H2S through the solution removes many metals, and a second extraction with Et2O frees Ga further from metal impurities, except for Mo, Th(III) and Fe which are largely removed by precipitation with NaOH. The solution is then electrolysed in 10% NaOH with a Pt anode and cathode (2-5A at 4-5V) to deposit Ga, In, Zn and Pb, from which Ga was obtained by fractional crystallisation of the melt [Hoffman J Res Nat Bur Stand 13 665 1934]. Ga is also purified by heating to boiling in 0.5-1M HCl, then heating to 40o in water and pouring the molten Ga with water under vacuum through a glass filter (30-50 Y pore size), to remove any unmelted metals or oxide film. The Ga is then fractionally crystallised from the melt under water. [D.nges in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 837 1963.]
Hazard
Most gallium compounds are toxic, particularly the metal gallium arsenide. When forms ofgallium are used in the electronics industry, great care must be taken to protect workers.
Pharmaceutical Applications
Gallium has atomic number 31 in the periodic table of elements. It has a silvery-white colour with a melting point of only 29 C, which means that it melts when held in the hand. It has no known physiological role in the human body, but it can interact with cellular processes and proteins that are normally involved in iron metabolism.
It has been shown that gallium ions predominantly accumulate in the bone and therefore would be a good candidate for radiotherapy of bone cancer. Unfortunately, the radioactive isotope 72Ga has only a half-life of around 14h, which is not long enough for effective radiotherapy. Nevertheless, current clinical developments involve the use of radioactive gallium isotopes as tumour imaging reagents, gallium nitrate in metabolic bone disease, hypercalcaemia and as anticancer drug, as well as up-to-date research in the area of chemotherapeutic applications.
Industrial uses
An elementary metal, symbol Ga, gallium is silvery white, resembling mercury in appearance but having chemical properties more nearly like aluminum. Like bismuth, the metal expands on freezing, the expansion amounting to about 3.8%. Pure gallium is resistant to mineral acids, and dissolves with difficulty in caustic alkali. Commercial gallium has a purity of 99.9%. In the molten state it attacks other metals, and small amounts have been used in Sn Pb solders to aid wetting and decrease oxidation, but it is expensive for this purpose.
Gallium alloys readily with most metals at elevated temperatures. It alloys with tin, zinc, cadmium, aluminum, silver, magnesium, copper, and others. Tantalum resists attack up to 450 C, and tungsten to 800 C. Gallium does not attack graphite at any temperature and silica- base refractories are satisfactory up to about 1000 C.
Carcinogenicity
Gallium has not been tested for its ability to adversely affect reproduction. However, some gallium compounds are teratogenics and produce alterations in reproductive capacity.
Carcinogenesis：Gallium has not been tested for its ability to cause cancer in animals. However, gallium is capable of altering several cellular defense mechanisms involved in carcinogenesis. Genetic and Related Cellular Effects Studies. Concentrations of 480 mM cause DNA inhibition in human lymphocytes .
Other: Neurological, Pulmonary, and Skin Sensitization. Repeated exposure may damage the kidneys. Some gallium compounds may affect the nervous system. It is not known if pure gallium can do this. It is not known whether gallium causes lung damage.
Environmental Fate
Gallium compounds cannot be oxidized, and atmospheric
transformations would not be expected to occur during transport.
Particulate-phase gallium will be removed from the
atmosphere by wet and dry depositions. Gallium compounds
are expected to exist as ions in the environment and therefore
volatilization from water surfaces is not expected to be an
important fate process.
Structure and conformation
The space lattice of gallium (Ga) belongs to the orthorhombic system D2h18with lattice constants
a=0.45167 nm, b=0.45107 nm and c=0.76448 nm. A unit cell contains 8 atoms. It is
considered to form the molecular lattice of Ga2, which consists of 3 pairs of atoms with a
bond length of 0.271–0.280 nm and a pair with a short bond length of 0.244 nm.
Toxicity evaluation
Gallium can interfere with the structural integrity of transferrin,
the ircin-binding protein that transports iron in the serum.
Gallium is believed to bind in the protein methionine. In
microorganisms like Escherichia coli, gallium suppresses the
synthesis of low-molecular-weight polypeptides. It also concentrates
on the surface of the cell envelope.
