Chemical Properties
Germanium is a grayish-white, lustrous, and
brittle metalloid. The powder is grayish-black and odorless. It
is never found free and occurs most commonly in ergyrodite
and germanite. It is generally recovered as a by-product in
zinc production, coal processing, or other sources.
Chemical Properties
greyish-white lustrous brittle solid, odourless
Potential Exposure
Because of its semiconductor proper ties, germanium is widely used in the electronic industry in
rectifiers, diodes, and transistors. It is alloyed with alumi num, aluminum magnesium, antimony, bronze, and tin to
increase strength, hardness, or corrosion resistance. In the
process of alloying germanium and arsenic, arsine may be
released; stibine is released from the alloying of germanium and antimony. Germanium is also used in the manufacture
of optical glass for infrared applications; red-fluorescing
phosphors; and cathodes for electronic valves; and in elec troplating; in the hydrogenation of coal; and as a catalyst,
particularly at low temperatures. Certain compounds are
used medically. Industrial exposures to the dust and fumes
of the metal or oxide generally occur during separation and
purification of germanium, welding, multiple-zone melting
operations, or cutting and grinding of crystals. Germanium
tetrahydride (germanium hydride, germane, and monoger mane) and other hydrides are produced by the action of a
reducing acid on a germanium alloy.
First aid
Move victim to fresh air. Call 911 or emergency
medical service. Give artificial respiration if victim is not
breathing. Do not use mouth-to-mouth method if victim
ingested or inhaled the substance; give artificial respira tion with the aid of a pocket mask equipped with a one-way valve or other proper respiratory medical device.
Administer oxygen if breathing is difficult. Remove and
isolate contaminated clothing and shoes. In case of contact
with substance, immediately flush skin or eyes with run ning water for at least 20 minutes. For minor skin contact,
avoid spreading material on unaffected skin. Keep victim
warm and quiet. Effects of exposure (inhalation, ingestion,
or skin contact) to substance may be delayed. Ensure that
medical personnel are aware of the material(s) involved
and take precautions to protect themselves. Medical obser vation is recommended for 24 to 48 hours after breathing
overexposure, as pulmonary edema may be delayed. As
first aid for pulmonary edema, a doctor or authorized para medic may consider administering a drug or other inhala tion therapy.
Shipping
UN3089 Metal powders, flammable, n.o.s.,
Hazard Class: 4.1; Labels: 4.1-Flammable solid. UN1759
Corrosive solids, n.o.s., Hazard class: 8; Labels:
8-Corrosive material, Technical Name required.
Incompatibilities
A strong reducing agent and flammable
solid. Finely divided metal is incompatible with oxidizing
and nonoxidizing acids, ammonia, bromine, oxidizers, aqua
regia, sulfuric acid, carbonates, halogens, and nitrates.
Explosive reaction or ignition with potassium chlorate,
potassium nitrate, chlorine, bromine, oxygen, and potas sium hydroxide in the presence of heat. Violent reaction
with strong acids: aqua regia, nitric, and sulfuric.
Incompatible with oxidizers (chlorates, nitrates, peroxides,
permanganates, perchlorates, chlorine, bromine, fluorine,
etc.); contact may cause fires or explosions.
Description
Germanium is extracted from zinc ores in a very complicated process as it has aqueous properties similar
to those of zinc. Once the germanium/zinc mixture has been sufficiently enriched with germanium, it is
heated in HCl with Cl2 in order to allow the formation of germanium tetrachloride (GeCl2).
Waste Disposal
Recovery and return to sup pliers for reprocessing is preferable.
Physical properties
Germanium has a gray shine with a metallic silvery-white luster. It is a brittle elementclassed as a semimetal or metalloid, meaning it is neither a metal such as iron or copper nora nonmetal, such as phosphorus, sulfur, or oxygen. Germanium has some properties likea metal and some like a nonmetal. It is a crystal in its pure state, somewhat like silicon. Itwill combine with oxygen to form germanium dioxide, which is similar to silicon dioxide(sand).
Germanium is not found in its free elemental state because it is much too reactive. For themost part, it is found combined with oxygen, either as germanium monoxide or as germaniumdioxide. Also, it is recovered from the ores of zinc, copper, and arsenic and the flue depositsof burning coal.
The crystal structure of germanium is similar to that of diamonds and silicon, and its semiconductingproperties are also similar to silicon.The melting point of germanium is 938.3°C, its boiling point is 2833°C, and its densityis 5.323 g/cm3.
Isotopes
There are a total of 38 isotopes of Germanium, five of which are stable. Thestable isotopes of germanium and their natural abundance are as follows: Ge-70 =20.37%, Ge-72 = 27.31%, Ge-73 = 7.76%, Ge-74 = 36.73%, and Ge-76 = 7.83%.Ge-76 is considered stable because it has such a long half-life (0.8×10+25 years)All theother 33 isotopes are radioactive and are produced artificially.
Origin of Name
Germanium’s name was derived from the Latin word Germania, meaning
“Germany.”
Occurrence
Germanium, the 52nd most abundant element in the Earth’s crust, is widely distributed,but never found in its natural elemental state. It is always combined with other elements,particularly oxygen.
Germanium’s main minerals are germanite, argyrodite, renierite and canfieldite, all ofwhich are rare. Small amounts of germanium are found in zinc ore, as well as in copper andarsenic ores. It is known to concentrate in certain plants on Earth, particularly in coal: commercialquantities are collected from the soot in the stacks where coal is burned.
Characteristics
Once germanium is recovered and formed into blocks, it is further refined by the manufacturerof semiconductors. It is melted, and the small amounts of impurities such as arsenic, gallium,or antimony, are added. They act as either electron donors or acceptors that are infused(doped) into the mix. Then small amounts of the molten material are removed and used togrow crystals of germanium that are formed into semiconducting transistors on a germaniumchip. The device can now carry variable amounts of electricity because it can act as both aninsulator and a conductor of electrons, which is the basis of modern computers.
Purification Methods
Copper contamination on the surface and in the bulk of single crystals of Ge can be removed by immersion in molten alkali cyanide under N2. The Ge is placed in dry K and/or Na cyanide powder in a graphite holder in a quartz or porcelain boat. The boat is then inserted into a heated furnace which, after a suitable time, is left to cool to room temperature. At 750o, a 1mm thickness of metal requires about 1minute, whereas 0.5cm needs about half hour. The boat is removed from the furnace, and the solid samples are taken out with plastic-coated tweezers, carefully rinsed in hot water and dried in air [Wang J Phys Chem 60 45 1956, Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 712 1963]. Care with the use of cyanide.
Hazard
Many of the chemicals used in the semiconductor industries are highly toxic. For example,germanium-halogen compounds are extremely toxic, both as a powder and in a gaseous state.Precautions should be taken when working with germanium as with similar metalloids fromgroup 14 (IVA).
Flammability and Explosibility
Notclassified
Industrial uses
A rare elemental metal, germanium (Ge) has agrayish white crystalline appearance and hasgreat hardness: 6.25 Mohs. Its specific gravityis 5.35, and melting point is 937°C. It is resistantto acids and alkalies. It has metallic-appearingcrystals with diamond structure, givesgreater hardness and strength to aluminum andmagnesium alloys, and as little as 0.35% in tinwill double the hardness. It is not used commonlyin alloys, however, because of its rarityand great cost. It is used chiefly as metal inrectifiers and transistors. An Au–Ge alloy, withabout 12% germanium, has a melting point of359°C and has been used for soldering jewelry.
Germanium is obtained as a by-productfrom flue dust of the zinc industry, or it can beobtained by reduction of its oxide from the ores,and is marketed in small irregular lumps. Germaniumcrystals are grown in rods up to 3.49cm in diameter for use in making transistorwafers. High-purity crystals are used for both P and Nsemiconductors. They are easier topurify and have a lower melting point than othersemiconductors, specifically silicon.
Industrial uses
Germanium lenses and filters have been usedin instruments that operate in the infraredregion of the spectrum. Windows and lenses ofgermanium are vital components of some laserand infrared guidance or detection systems.Glasses prepared with germanium dioxide havea higher refractivity and dispersion than docomparable silicate glasses and may be used inwide-angle camera lenses and microscopes.
Environmental Fate
Metals are recalcitrant to degradation; therefore, no biodegradation studies have been performed on germanium compounds. Naturally occurring germanium exists in mineral ores; therefore, the levels of free germanium are expected to be low and of low concern for bioaccumulation in aquatic and terrestrial species, due to negligible exposures.
