Germanium


from Wikipedia, the free encyclopedia
properties
General
Name , symbol , atomic number Germanium, Ge, 32
Element category Semi-metals
Group , period , block 14 , 4 , p
Appearance grayish white
CAS number 7440-56-4
EC number 231-164-3
ECHA InfoCard 100.028.331
Mass fraction of the earth's envelope 5.6 ppm
Atomic
Atomic mass 72,630 (8) u
Atomic radius (calculated) 125 (125) pm
Covalent radius 122 pm
Van der Waals radius 211 pm
Electron configuration [ Ar ] 3 d 10 4 s 2 4 p 2
1. Ionization energy 7th.899 435 (12) eV 762.18 kJ / mol
2. Ionization energy 15th.934 610 results (25 eV) 1 537.46 kJ / mol
3. Ionization energy 34.0576 (12) eV3 286.1 kJ / mol
4. Ionization energy 45.7155 (12) eV4 410.9 kJ / mol
5. Ionization energy 90.500 (19) eV8 732 kJ / mol
Physically
Physical state firmly
Crystal structure Diamond structure
density 5.323 g / cm 3 (20 ° C )
Mohs hardness 6.0
magnetism diamagnetic ( Χ m = −7.1 10 −5 )
Melting point 1211.4 K (938.3 ° C)
boiling point 3106 K (2830 ° C)
Molar volume 13.63 · 10 −6 m 3 · mol −1
Heat of evaporation 330 kJ / mol
Heat of fusion 31.8 kJ mol −1
Speed ​​of sound 5400 m s −1 at 293.15 K.
Specific heat capacity 308.3 J kg −1 K −1
Work function 5.0 eV
Electric conductivity ( Intrinsic conduction ) 2 A · V −1 · m −1 at 300 K.
Thermal conductivity 60 W m −1 K −1
Chemically
Oxidation states −4, 2, 4
Normal potential 0.247 V (Ge 2+ + 2 e - → Ge)
Electronegativity 2.01 ( Pauling scale )
Isotopes
isotope NH t 1/2 ZA ZE (M eV ) ZP
68 Ge {syn.} 270.8 d ε 0.106 68 Ga
69 Ge {syn.} 39.05 h ε 2.227 69 Ga
70 Ge 20.5% Stable
71 Ge {syn.} 11.43 d ε 0.229 71 Ga
72 Ge 27.4% Stable
73 Ge 7.8% Stable
74 Ge 36.5% Stable
75 Ge {syn.} 82.78 min β - 1.177 75 As
76 Ge 7.44% (1.84 +0.14 -0.10 ) 10 21 a β - β - 76 Se
77 Ge {syn.} 11.30 h β - 2.702 77 As
For other isotopes see list of isotopes
safety instructions
GHS labeling of hazardous substances

powder

02 - Highly / extremely flammable

danger

H and P phrases H: 228
P: 210
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .

Germanium (from Latin Germania ' Germany ', after the country in which it was first found) is a chemical element with the element symbol Ge and the atomic number 32. In the periodic table it is in the 4th period and in the 4th main group (14th . IUPAC group , p- block and carbon group ). It was first detected in the mineral argyrodite in 1886 .

history

Clemens Winkler , first manufacturer of pure germanium
Preparations of the element germanium made by Clemens Winkler.
Above: The preparations shown at the 1904 World Exhibition in St. Louis
Below: Germanium sulfide from February 6, 1886

When Dmitri Mendeleev designed the periodic table in 1871 , he came across a gap below silicon and postulated a previously unknown element, which he called eka-silicon. Mendeleev made predictions about the properties of eka-silicon and its compounds, but these were rejected by science.

In 1885, Clemens Winkler (1838–1904), a chemist at the Bergakademie Freiberg , found, when he was working with the newly discovered mineral argyrodite, that its quantitative analysis always yielded a shortfall of around seven percent. As often as the analysis was repeated, the shortfall remained more or less constant and Winkler finally suspected that the mineral contained a previously unknown element. After four months of work, he finally managed to isolate a white sulphide precipitate on February 6, 1886 , which could be reduced to a metallic powder in a stream of hydrogen . Based on the previously discovered planet Neptune , Winkler initially wanted to name the new element Neptunium . However, since this name had already been used for another suspected element, he named it germanium after the place of discovery. Winkler initially suspected that the germanium was the eka stibium postulated by Mendeleev , while Mendeleev initially wanted to classify it as eka cadmium rather than eka silicon. After further properties were determined, it was confirmed that it was probably the predicted element eka-silicon. Mendeleev had derived its properties from his periodic table, so this discovery contributed to the recognition of the periodic table:

property Eka silicon
(predicted)
Germanium
(certain)
Atomic weight 72 72.32
specific weight 5.5 5.47
Atomic volume 13 13.22
Value IV IV
Specific heat 0.073 0.076
Specific weight of the dioxide 4.7 4.703
Molecular volume of the dioxide 22nd 22.16
Boiling point of the tetrachloride below 100 ° C 86 ° C
Specific weight of the tetrachloride 1.9 1.87
Molecular volume of the tetrachloride 113 113.35

The origin and etymology of the name germanium could also result from a semantic misunderstanding in connection with its predecessor element gallium , because there are two theories for the naming of gallium. After the first, the French chemist Paul Émile Lecoq de Boisbaudran named the element after Gaul , the Latin name of his native France . The second gives the Latin word gallus (cock) as the source of the name, which in French means le coq ("the cock"). Paul Émile Lecoq de Boisbaudran would have named the new element after his own name. Winkler assumed that the previous element gallium was named after the nationality of the French discoverer. He named the new chemical element “germanium” in honor of his country (Latin Germania for Germany).

Occurrence

Renierite

Germanium is widespread, but only occurs in very low concentrations. The Clarke value , i.e. the average content in the earth's crust, is around 1.5 g / t . In nature it occurs mostly in the form of sulfides or thiogermanates and is often found as a companion in copper and zinc ores , including in the Mansfeld copper shale . The most important minerals are argyrodite (Ag 8 GeS 6 ), canfieldite , germanite (Cu 6 FeGe 2 S 8 ) and renierite . Some plants enrich germanium. This property leads to highly controversial theses regarding the physiology of plants (“plant defense against viruses”), with which applications in homeopathy are justified.

Extraction and manufacture

According to the USGS , annual production in 2014 was an estimated 165 t, 120 t of which in China. The price for 1 kg of germanium was around 1,900 USD in 2014  . According to the EU, the price was USD 300 per kg in 2003 and rose to USD 1,000 by 2009.

The germanium oxide (GeO 2 ) -containing flue gases from zinc ore processing are particularly suitable for producing germanium. The germanium is enriched from the flue gas by dissolving the flue dust in sulfuric acid. After the dissolved GeO 2 and ZnO have been precipitated, further processing is carried out by distilling the metal chlorides. The hydrolysis then leads back to the oxide, which is reduced to germanium with hydrogen. The representation of high purity germanium can, for. B. be done by the zone melting process.

properties

Elemental germanium

Germanium is in the semimetallic series in the periodic table , but according to the more recent definition it is classified as a semiconductor . Elemental germanium is very brittle and very stable in air at room temperature. It is only oxidized to germanium (IV) oxide (GeO 2 ) when it is heavily glowing in an oxygen atmosphere . GeO 2 is dimorphic and is converted from the rutile modification (CN = 6) to the β-quartz structure (CN = 4) at 1033 ° C. In powder form, it can be easily ignited and continues to burn after removing the ignition source. In compact form, it is not flammable.

Germanium is bivalent and tetravalent. Germanium (IV) compounds are the most persistent. Germanium is not attacked by hydrochloric acid , potassium hydroxide solution and dilute sulfuric acid . In alkaline hydrogen peroxide solutions, concentrated hot sulfuric acid and concentrated nitric acid , on the other hand, it is dissolved with the formation of germanium dioxide hydrate. According to its position in the periodic table , its chemical properties are somewhere between silicon and tin .

Germanium is one of the few substances that shows a density anomaly . Its density in the solid state is lower than in the liquid. Its band gap is about 0.67 eV at room temperature  .

Germanium wafers are significantly more fragile than silicon wafers.

use

electronics

As a semiconductor , germanium in single crystal form was the leading material in electronics in the middle of the 20th century, especially for the manufacture of the first diodes and bipolar transistors available on the market , until it was replaced by silicon in these areas. Applications are found today in high-frequency technology (e.g. as silicon-germanium compound semiconductors) and detector technology (e.g. as X-ray detectors). For solar cells made of gallium arsenide (GaAs), wafers made of germanium are sometimes used as the carrier material. The lattice constant of germanium is very similar to that of gallium arsenide, so that GaAs can grow epitaxially on germanium single crystals.

Glasses and fibers

Its second main application is in infrared optics in the form of windows and lens systems made of poly- or monocrystalline germanium as well as optical glasses with infrared permeability, so-called chalcogenide glasses. Areas of application for this include military and civil night vision devices and thermal imaging cameras .

Other essential uses are in the production of optical waveguides and polyester fibers: In modern glass fibers for telecommunications, germanium tetrachloride is used to generate an enrichment of germanium dioxide in the inner fiber core during chemical vapor deposition . This results in a higher refractive index in the core compared to the fiber cladding , which ensures that the light waves are guided. In polyester chemistry, germanium dioxide is used as a catalyst in the production of certain polyester fibers and granulates, especially for recyclable PET bottles (PET = polyethylene terephthalate ).

Nuclear medicine and nuclear engineering

68 Ge is used in the Gallium-68 generator as the mother nuclide for the production of Gallium-68. Also found 68 Ge as a source for Detektorkalibration in positron emission tomography application.

As a high-purity single crystal , germanium is used as a radiation detector.

Germanium in food supplements

The substance bis (carboxyethyl) germanium sesquioxide ( Ge-132 ) has been touted as a dietary supplement for use in a number of diseases including cancer , chronic fatigue syndrome , immune deficiency , AIDS , high blood pressure , arthritis and food allergies . So far, no positive effects on the course of the disease have been scientifically proven.

According to the European Directive 2002/46 / EC on the approximation of the laws of the Member States on food supplements , germanium should not be used in food supplements. In many EU countries that have already aligned their national legislation, including Germany and Austria, the addition of germanium as a mineral source in food supplements is therefore not allowed.

The responsible authorities expressly warn against the consumption of Ge-132 , as serious damage to health and death cannot be ruled out.

Medicinal use of germanium

A therapeutic efficacy of the anti- neoplastic substance Spirogermanium in cancer diseases has not been proven. There are no approved finished medicinal products with the active ingredient spirogermanium. In Germany, medicinal products (recipes) containing germanium, apart from homeopathic dilutions from D4, are considered questionable. Their production and their distribution are therefore prohibited. Germanium metallicum is available in the form of homeopathic medicines . Di- potassium germanium citrate lactate is described as a component of homeopathic preparations .

physiology

Germanium and its compounds have a relatively low acute toxicity . Traces of germanium can be found in the following foods: beans , tomato juice , oysters , tuna and garlic . According to the current state of science, it is not an essential trace element. There is no known biological function for germanium. No germanium deficiency diseases are known.

toxicity

Health damage caused by germanium occurred several times in humans after prolonged intake of germanium compounds as a dietary supplement. This leads to functional disorders of the kidneys up to (irreversible) kidney failure, which can be fatal for the patient . Peripheral neuropathy and other secondary neurological damage have also been reported.

It is known from animal experiments that germanium has a low acute oral toxicity. In rats, the LD 50 value (the dose at which half of the test animals die) is 3700 mg per kilogram of body weight.

By currently available data from animal experiments Germanium is not teratogenic or carcinogenic .

The mechanism of toxicity of germanium is not yet fully understood. However, specific pathological effects on the mitochondria of different cells were observed.

Interactions

It is also discussed whether germanium might interact with silicon in bone metabolism. It can block the action of diuretics and reduce or block the activity of a number of enzymes , such as dehydrogenases . In animal experiments , mice show an increased hexabarbital-induced sleep duration when they were additionally treated with germanium compounds. This suggests that cytochrome P450 activity is also restricted. There have been reports of organic germanium compounds that block the detoxification enzyme glutathione-S-transferase .

Bioavailability and metabolism

Germanium is very easily absorbed by the body when ingested. It is distributed over the entire body tissue, primarily in the kidneys and the thyroid . In contrast to inorganic germanium compounds, organogermanics do not accumulate in the human body. However, there are only a few studies of germanium metabolism.

It is essentially excreted in the urine. Excretion via bile and faeces also takes place.

links

Germanium forms Ge (II) - u. more stable Ge (IV) compounds, only a few are of technical importance.

Of the germanium halides, Ge (II) - u. Ge (IV) representative known. Germanium tetrachloride , (GeCl 4 ), a liquid with a boiling point of 83 ° C, forms when germanium oxides are exposed to hydrogen chloride and is an important intermediate product in the production of germanium. Highly pure GeCl 4 is used in the manufacture of optical waveguides made of quartz glass in order to produce a high-purity germanium (IV) oxide layer on the inside of the quartz fibers. The disproportionation of germanium (II) iodide with the formation of germanium and germanium (IV) iodide can also be used to produce highly pure germanium layers :

Germanates are compounds of germanium that are derived from its oxide. The germanium is present as germanate in almost all minerals containing germanium.

Germans are the name given to the hydrogen compounds of germanium, which form a homologous series of chain molecules of different lengths. Monogerman or germanium hydride (GeH 4 ) is a gas and is used in the semiconductor industry for epitaxy and doping.

literature

  • Mike Haustein: The gap in the periodic table: germanium. In: Chemistry in Our Time. Volume 45, Issue 6 (2011), pp. 398-405 ( doi: 10.1002 / ciuz.201100549 ).

Web links

Wiktionary: Germanium  - explanations of meanings, word origins, synonyms, translations
Commons : Germanium  - album with pictures, videos and audio files

Individual evidence

  1. a b Harry H. Binder: Lexicon of the chemical elements. S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 .
  2. The values ​​for the properties (info box) are taken from www.webelements.com (Germanium) , unless otherwise stated .
  3. ^ IUPAC, Standard Atomic Weights Revised 2013 .
  4. Manjeera Mantina, Adam C. Chamberlin, Rosendo Valero, Christopher J. Cramer, Donald G. Truhlar: Consistent van der Waals Radii for the Whole Main Group. In: J. Phys. Chem. A. 113, 2009, pp. 5806-5812, doi: 10.1021 / jp8111556 .
  5. a b c d e Entry on germanium in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 11, 2020.
  6. a b c d e entry on germanium at WebElements, https://www.webelements.com , accessed on June 11, 2020.
  7. ^ NN Greenwood, A. Earnshaw: Chemistry of the elements. 1st edition. VCH, Weinheim 1988, ISBN 3-527-26169-9 , p. 482.
  8. David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Properties of the Elements and Inorganic Compounds, pp. 4-142-4-147. The values ​​there are based on g / mol and are given in cgs units. The value specified here is the SI value calculated from it, without a unit of measure.
  9. a b Yiming Zhang, Julian RG Evans, Shoufeng Yang: Corrected Values ​​for Boiling Points and Enthalpies of Vaporization of Elements in Handbooks. In: Journal of Chemical & Engineering Data. 56, 2011, pp. 328-337, doi: 10.1021 / je1011086 .
  10. Ludwig Bergmann, Clemens Schaefer, Rainer Kassing: Textbook of Experimental Physics . Volume 6: Solids. 2nd Edition. Walter de Gruyter, Berlin 2005, ISBN 3-11-017485-5 , p. 361.
  11. J. Phys. G: Nucl. Part. Phys. 40 (2013) 035110 doi: 10.1088 / 0954-3899 / 40/3/035110
  12. a b Entry on germanium, powder in the GESTIS substance database of the IFA , accessed on April 30, 2017(JavaScript required) .
  13. a b c O. Brunck: Clemens Winkler . In: Reports of the German Chemical Society . tape 39 , no. 4 , November 1906, p. 4491-4548 , doi : 10.1002 / cber.190603904164 .
  14. Klaus people: Clemens Winkler's 100th anniversary . In: Chemistry in Our Time . tape 38 , no. 5 , October 2004, p. 360 , doi : 10.1002 / ciuz.200490078 .
  15. Clemens Winkler: Germanium, Ge, a new, non-metallic element . In: Reports of the German Chemical Society . tape 19 , no. 1 , January 1886, p. 210 , doi : 10.1002 / cber.18860190156 .
  16. a b Clemens Winkler: Mittheilungen about the germanium . In: Journal for Practical Chemistry . tape 34 , no. 1 , August 14, 1886, p. 177 , doi : 10.1002 / prac.18860340122 .
  17. a b Eka-Cadmium and Eka-Stibium are two elements postulated by Mendeleev between cadmium and mercury and between antimony and bismuth, which are nowadays mostly ignored as not-so-famous blanks .
  18. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 .
  19. ^ A b c d Wiberg, Egon., Wiberg, Nils ,: Textbook of Inorganic Chemistry . 102nd, heavily reworked and verb. Ed. De Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1003 .
  20. MINERAL COMMODITY SUMMARIES 2015. (PDF 2.3 MB, p. 68 (65)) USGS , accessed on September 5, 2015 (English).
  21. Germanium. (No longer available online.) Setis.ec.europa.eu, archived from the original on March 5, 2016 ; accessed on September 5, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / setis.ec.europa.eu
  22. Eckert & Ziegler product catalog, p. 15. ( Memento of the original from January 3, 2007 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.ezag.de
  23. Federal Office for Safety in Health Care, AGES PharmMed: " Dietary supplements" with toxic effects. ( Memento from July 20, 2012 in the web archive archive.today )
  24. Directive 2002/46 / EC of the European Parliament and of the Council of June 10, 2002 (PDF) .
  25. Federal Institute for Risk Assessment : BgVV warns against the consumption of 'Germanium-132 capsules' from the Austrian company Ökopharm. September 8, 2000.
  26. Austrian Agency for Health and Food Safety (AGES) warns: Product contains a harmful concentration of germanium ( Memento of July 28, 2013 in the Internet Archive ) October 17, 2008.
  27. Medicines Commission of German Pharmacists: Questionable Prescription Medicines (PDF; 423 kB).
  28. ^ Germanium-Citrate- Lactat at DailyMed , accessed on September 16, 2012.
  29. a b c d Nephrotoxicity and neurotoxicity in humans from organogermanium compounds and germanium dioxide. PMID 1726409 .
  30. a b Tubulointerstitial nephropathy persisting 20 months after discontinuation of chronic intake of germanium lactate citrate. PMID 8488824 .
  31. a b Germanium poisoning: clinical symptoms and renal damage caused by long-term intake of germanium. PMID 1650857 .
  32. ^ Hazard assessment of germanium supplements. doi : 10.1006 / rtph.1997.1098 .
  33. Federal Institute for Occupational Safety and Health (Ed.): Germanium and Germanium dioxide . May 2018, p. 7th ff . ( baua.de [PDF; 447 kB ; accessed on August 4, 2019]).
  34. Federal Institute for Occupational Safety and Health (Ed.): Germanium and Germanium dioxide . May 2018, p. 7 ( baua.de [PDF; 447 kB ; accessed on August 4, 2019]).
  35. Federal Institute for Occupational Safety and Health (Ed.): Germanium and Germanium dioxide . May 2018, p. 14th ff . ( baua.de [PDF; 447 kB ; accessed on August 4, 2019]).
  36. ^ Germanium dioxide induces mitochondria-mediated apoptosis in Neuro-2A cells. doi : 10.1016 / j.neuro.2006.05.018 .
  37. ^ The pathogenesis of experimental model of mitochondrial myopathy induced by germanium dioxide. PMID 12899328 .
  38. ^ Roy A. Henry, Keith H. Byington: Inhibition of glutathione-S-aryltransferase from rat liver by organogermanium, lead and tin compounds . In: Biochemical Pharmacology . tape 25 , no. 20 , 1976, p. 2291-2952 , doi : 10.1016 / 0006-2952 (76) 90012-5 .
  39. a b Federal Institute for Occupational Safety and Health (Ed.): Germanium and Germanium dioxide . May 2018, p. 4th ff . ( baua.de [PDF; 447 kB ; accessed on January 18, 2020]).
  40. BgVV warns against the consumption of 'Germanium-132 capsules' from the Austrian company Ökopharm. In: Federal Institute for Risk Assessment. September 8, 2000, accessed January 18, 2020 .