Difference between revisions of "Germanium"

Revision as of 04:16, 14 June 2015

Germanium is a chemical element with symbol Ge and atomic number 32. It is a metalloid.

Properties

Chemical

Elemental germanium is stable in air, and slowly oxidizes to GeO₂ at 250 °C. Germanium is insoluble in dilute acids and alkalis, but reacts slowly with concentrated sulfuric acid and violently with molten alkalis to produce germanates ([GeO₃]²⁻).

Germanium halides hydrolyze in water or moist air.

Physical

Germanium is a brittle, silvery-white, semi-metallic element. It posses two allotrope forms:

• α-germanium: the form at standard conditions. It has a metallic luster and a diamond cubic crystal structure.
• β-germanium: forms at pressures above 120 kbar. It posses the same structure as β-tin.

Extremely pure germanium will spontaneously extrude very long screw dislocations. This is the primary reason why old transistors fail.

Along with antimony, bismuth, gallium, silicon and water, it is one of the few substances that expands as it solidifies. Germanium is a semiconductor.

Availability

Germanium can be found in very old transistors and diodes, albeit the amount is small.

Pure germanium can be purchased from Metallium, at $11/g. It is very easy to find extremely pure germanium, as it is used in certain semiconductors.

Preparation

Elemental germanium can be prepared by reducing germanium dioxide (germania) with hydrogen.

GeO₂ + H₂ → Ge + H₂O

Germanium is less reactive than silicon, so carbon can also be used as a reducing agent.

GeO₂ + C → Ge + CO₂

Unlike in the case of silicon, this reduction will yield only a small quantity of carbide.

Projects

• Make germanium dioxide
• Make germane (GeH₄)

Handling

Safety

Pure germanium has low toxicity, however its compounds have different biological effects. Inorganic germanium compounds tend to accumulate inside the body and will cause health related problems. Organic germanium compounds have been shown to be less toxic and some even have beneficial properties.

Storage

Germanium reacts very slowly in air to produce a thin protective layer of germania. No special storage is required.

Disposal

Germanium is present only in traces in nature. Germania is inert so it does not pose environmental hazard, and may be dumped in the trash. Inorganic germanium compounds should be converted to germania before discarding or recycling.

References

Relevant Sciencemadness threads

• Dissolving germanium metal