# tungsten

properties
[ Xe ] 4 f 14 5d 4 6 s 2
74 W
General
Name , symbol , atomic number Wolfram, W, 74
Element category Transition metals
Group , period , block 6 , 6 , d
Appearance grayish white, shiny
CAS number 7440-33-7
EC number 231-143-9
ECHA InfoCard 100.028.312
Mass fraction of the earth's envelope 64 ppm
Atomic
Atomic mass 183.84 (1) u
Atomic radius (calculated) 135 (193) pm
Covalent radius 162 pm
Electron configuration [ Xe ] 4 f 14 5d 4 6 s 2
1. Ionization energy 7th.86403 (10) eV758.76 kJ / mol
2. Ionization energy 16.37 (15) eV1 580 kJ / mol
3. Ionization energy 26th.0 (4) eV2 510 kJ / mol
4. Ionization energy 38.2 (4) eV3 690 kJ / mol
5. Ionization energy 51.6 (3) eV4 979 kJ / mol
Physically
Physical state firmly
Crystal structure body-centered cubic
density 19.25 g / cm 3 (20 ° C )
Mohs hardness 7.5
magnetism paramagnetic ( Χ m = 7.8 10 −5 )
Melting point 3695 K (3422 ° C)
boiling point 6203 K (5930 ° C)
Molar volume 9.47 10 −6 m 3 mol −1
Heat of evaporation 774 kJ / mol
Heat of fusion 35.2 kJ mol −1
Speed ​​of sound 5174 m · s −1
Specific heat capacity 138 J kg −1 K −1
Work function 4.55 eV
Electric conductivity 18.52 · 10 6 A · V −1 · m −1
Thermal conductivity 170 W m −1 K −1
Chemically
Oxidation states 6 , 5, 4, 3, 2
Normal potential −0.119 V (WO 2 + 4H + + 4e -
→ W + 2H 2 O)
Electronegativity 2.36 ( Pauling scale )
Isotopes
isotope NH t 1/2 ZA ZE (M eV ) ZP
178 W {syn.} 21.6 d ε 0.091 178 days
179 W {syn.} 37.05 min ε 1.060 179 days
180 W 0.13% 1.8 · 10 18 a α 2.516 176 Hf
181 W {syn.} 121.2 d ε 0.188 181 Ta
182 W 26.3% Stable
183 W 14.3% Stable
184 W 30.67  % Stable
185 W {syn.} 75.1 d β - 0.433 185 Re
186 W 28.6% Stable
187 W {syn.} 23.72 h β - 1,311 187 Re
188 W {syn.} 69.4 d β - 0.349 188 Re
For other isotopes see list of isotopes
NMR properties
Spin
quantum
number I
γ in
rad · T −1 · s −1
E r  ( 1 H) f L at
B = 4.7 T
in MHz
183 W 1/2 1.128 · 10 7 1.07 · 10 −5 4.166
safety instructions
GHS labeling of hazardous substances

powder

danger

H and P phrases H: 228
P: 210-240-241-280-370 + 378
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .

Tungsten [ ˈvɔlfram ] is a chemical element with the element symbol W and the ordinal number 74. It is one of the transition metals , in the periodic table it is in the 6th subgroup (group 6) or chromium group . Tungsten is a white, shiny heavy metal of high density that becomes brittle with very little contamination . It is the chemical element with the highest melting and boiling point . Its best-known use is therefore the filament in light bulbs .

## history

As early as the 16th century, the Freiberg mineralogist Georgius Agricola described the occurrence of a mineral in Saxon tin ores that made tin extraction considerably more difficult due to the slagging of the tin. The part of the name “wolf” comes from this property, as the mineral “ate” the tin ore like a wolf. Whether it was wolframite is still controversial today, as he spoke of the “lightness” of the mineral. He named the mineral lupi spuma , which translated from Latin means "wolf (s) foam". Later it was called tungsten , from mhd. Rām “soot, cream, dirt”, as the black-gray mineral can be easily ground and then reminds of soot. Its chemical symbol W comes from tungsten.

The word tungsten , commonly used in English, Italian and French, is derived from tung sten ( Swedish for "heavy stone"). In Sweden at that time this was not used to refer to tungsten itself (Swedish volfram ), but calcium tungstate . In 1781, the German-Swedish chemist Carl Wilhelm Scheele recognized a previously unknown salt in it. Pure tungsten was first produced in 1783 by the Spanish brothers Fausto and Juan José Elhuyar by reducing tungsten trioxide , which is extracted from wolframite.

## Occurrence

Wolframite from Portugal

The tungsten content of the continental crust is around 1 ppm or 0.0001% by weight. The metal was not found in nature so far gediegen be detected (in pure form). The Doklady Akademii Nauk in Russia published a report on solid tungsten in 1995 without it being examined by the Commission on new Minerals, Nomenclature and Classification (CNMNC) belonging to the IMA . Some minerals , especially oxides and tungstates, are known. The most important tungsten ore minerals are wolframite (Mn, Fe) WO 4 and scheelite CaWO 4 . There are also other tungsten minerals such as Stolzite PbWO 4 and Tuneptite WO 3  · H 2 O.

The largest deposits can be found in China , Peru , the USA , Korea , Bolivia , Kazakhstan , Russia , Austria and Portugal . Tungsten ores can also be found in the Ore Mountains . The safe and probable world deposits are currently 2.9 million tons of pure tungsten.

The most important known occurrence of tungsten in Europe is in the Felbertal in the Hohe Tauern (state of Salzburg in Austria ).

### Promotion worldwide

In 2017, tungsten production was 95,000 tons. By far the largest producer of tungsten is China. More than 80% of the tungsten produced in the world is extracted there. The states with the greatest extraction of tungsten are:

country 2006 2007 2013 2014 2015 2016 2017 Reserves
(in tons )
Australia 320 600 160,000
Bolivia 870 870 1,250 1,300 1,460 1.110 1.110 53,000
People's Republic of China 79,000 77,000 68,000 68,000 73,000 72,000 79,000 1,800,000
Canada 2,560 2,600 2.130 2,220 1,680 0 290,000
Democratic Republic of Congo 830 800 not specified
Mongolia 753 150 63,000
North Korea 600 600 not specified
Austria 1,300 1,300 850 850 861 954 950 10,000
Portugal 780 800 692 700 474 549 680 3,100
Rwanda 730 700 850 820 650 not specified
Russia 4,000 4,400 3,600 3,600 2,600 3,100 3,100 160,000
Spain 835 650 570 54,000
United Kingdom 150 736 1,100 43,000
Vietnam 1,660 2,000 5,600 6,500 7,200 95,000
other countries 1,680 2,040 1,290 1,700 1.910 880 860 950,000
total 90,800 89,600 81,400 82,400 89,400 88,100 95,000 3,200,000

### Promotion in Austria

In Austria, Scheelite was first discovered in 1815/16 on the Schellgaden gold deposit in the municipality of Muhr ( State of Salzburg ). As a result, beautiful scheelite crystals, sometimes several centimeters in size, were found in many crevices of the Hohe Tauern. All of these finds were of no practical use. The large deposit in the Felbertal remained undiscovered for the time being.

In 1950 it became known that large amounts of scheelite appeared in the magnesite deposit on the Wanglalm near Lanersbach / Tux (Tyrol) in the rear of the Zillertal, which had been being mined since 1927 . It was coarse scheelite intergrown with magnesite and quartz . In the following years around 10,000 tons of ore with an average tungsten oxide content of 1.8% were extracted. Because of the low market price, tungsten extraction was stopped at the end of the 1960s, but resumed in 1971 and continued until the end of magnesite mining in 1976.

In 1967 the largest deposit of scheelite in Europe was discovered in the Felbertal. The pieces of ore in streams were traced with the help of UV light (Scheelite fluoresces). The difficult exploration work in the high alpine terrain (highest mining site on the Brentling at 2100 m above sea level) began in 1971, while the mining company Wolfram Bergbau und Hütten AG (WBH) began in the Felbertal in 1976. From 1979 ore was also extracted in civil engineering and open-cast mining was stopped in 1986 for environmental reasons. Since then, the tungsten ore from the Felbertal has been transported to Mittersill via an underground conveyor system and processed there by WBH. From here the scheelite concentrate reaches Sankt Martin im Sulmtal (Styria). The Wolframhütte, which has been producing tungsten oxide, tungsten metal and tungsten carbide powders from concentrates from Mittersill and other countries, was built on the site of the Pölfing-Bergla underground lignite mine, which was closed in 1976. From the beginning of 1993 to mid-1995, mining was temporarily suspended due to the low market price for tungsten. The most important processors in Germany are the HC Starck company , and in Austria the WBH and the Plansee Group .

## Extraction and presentation

vapor-deposited tungsten crystals

Tungsten cannot be obtained from oxidic ores by reduction with coal, as this results in tungsten carbide .

Ores containing tungsten are initially enriched to WO 3 concentrations of 10 to 75% by processes such as gravity separation or flotation . The concentrate is then calcined in an oxidizing atmosphere at 500-600 ° C. in order to remove impurities such as additives from the flotation process. Wolframite ores are then reacted with sodium hydroxide solution , Scheelite ores with a sodium carbonate solution, with sodium tungstate Na 2 WO 4 being formed, which is then purified by a series of reprecipitations . Tungsten (VI) oxide is precipitated as ammonium paratungstate from the purified solution obtained by liquid-liquid extraction with ammoniacal solutions or ion exchange with ammonium ions . Scrap containing tungsten, such as hard metal scrap, can also be converted into sodium tungstate after oxidation and then into ammonium tungstate. This complex is filtered off and then converted into relatively pure tungsten (VI) oxide at 600 ° C. Annealing gives anhydrous tungsten (VI) oxide (WO 3 ), which is reduced at 800 ° C in a hydrogen atmosphere:

${\ displaystyle \ mathrm {WO_ {3} +3 \ H_ {2} \ longrightarrow W + 3 \ H_ {2} O}}$

This results in steel-gray tungsten powder, which is usually compacted in molds and electrically sintered into bars . At temperatures above 3400 ° C, a compact tungsten metal can be melted in special electric furnaces with a reducing hydrogen atmosphere ( zone melting process ).

## recycling

Due to the high material value, the recycling of tungsten is of considerable economic importance. Technologically, a distinction is made between soft scrap and hard scrap. Tungsten soft scrap is grinding sludge, powder and chips from the processing of workpieces containing tungsten. Tungsten hard scraps, on the other hand, are pieces of hard metal, tungsten metal and tungsten alloys.

Soft tungsten scrap is roasted in deck or rotary kilns . The resulting tungsten oxide is reacted under pressure with sodium hydroxide solution to form sodium tungstate. Tungsten hard scrap requires oxidizing fusion with sodium nitrate. A raw sodium tungstate solution is obtained from the resulting melt cake. For pure, clean hard metal scrap, there is a process with which hard metal powder can be recovered without going through oxidation. In a zinc melt, the hard metal pieces are heated to 900 to 1,000 ° C under protective gas . Zinc penetrates the binding metal and breaks the bond with the tungsten carbide powder. The zinc is then evaporated and the powder made from tungsten carbide and binder metal is processed into new hard metal products.

In addition to the main product tungsten, the recovery of cobalt, nickel, copper, silver and tantalum is technically possible and practiced in all processes. Around 30% of the tungsten contained in end-of-life scrap is recovered worldwide. The recycling of hard metal tools works better than the recycling of tungsten-containing alloys, chemicals and catalysts. In consumer goods such as B. lamps, pens and smartphones contains tungsten, but its concentration is too low for recycling.

Together with the new scrap that occurs during production and further processing, this results in a scrap usage rate of approx. 35% in tungsten production.

## properties

### Physical Properties

Tungsten is a shiny white, in its pure state malleable metal of medium hardness , as well as high density and strength . The density is almost the same as that of gold , the Brinell hardness is 250  HB , the tensile strength 550–620  N / mm 2 to 1920 N / mm 2 . The metal exists in a stable body-centered cubic α- modification with a lattice plane spacing (= lattice constant ) of 316 pm at room temperature. This type of crystal structure is often called the tungsten type. In contrast, a substance known as metastable β-modification of tungsten (distorted body-centered cubic) is the tungsten-rich oxide W 3 O.

With 3422 ° C of tungsten has the highest melting point of all chemical elements ( carbon does not melt but proceeds at 3642 ° C directly into the gaseous state) and 5930 ° C also has the highest boiling point .

The metal is a superconductor with a transition temperature of 15 mK.

### Chemical properties

Tungsten is a chemically very resistant metal that is hardly attacked even by hydrofluoric acid and aqua regia (at least at room temperature). However, it dissolves in mixtures of hydrofluoric and nitric acid and molten mixtures of alkali nitrates and carbonates.

## Isotopes

33 isotopes and five core isomers are known of tungsten . In nature there are five isotopes before 180 W, 182 W, 183 W, 184 W and 186 W. The tungsten isotope 184 W has the greatest frequency. All five natural isotopes could theoretically be unstable, but it was not until 2004 that the CRESST experiment at the Laboratori nazionali del Gran Sasso, as a secondary result of the search for dark matter, was able to prove that the 180 W isotope is subject to alpha decay . The half-life is an extremely long 1.8 trillion years, so this decay cannot be detected in a normal laboratory environment. The radioactivity of this natural isotope is so low that it can be ignored for all practical purposes. According to current knowledge, the possible half-lives of the other four natural isotopes should be longer than at least eight trillion years. The artificial radioactive isotopes of tungsten, on the other hand, have short half-lives between 0.9 ms at 185 W and 121.2 days at 181 W.

## use

### Science, technology and medicine

Tungsten after first use (2016, in%)

Approx. 65 percent of the quantities of tungsten produced worldwide are processed into tungsten carbide , which is used to manufacture hard metal tools. In addition, tungsten is primarily used as an alloying element.

Clamped end of the double filament of an incandescent lamp

Because of its high melting point, the most important application of pure tungsten is in the lighting industry as a filament in incandescent lamps and fluorescent tubes , and also as an electrode in gas discharge lamps and in electron tubes . In incandescent lamps, a higher specific resistance of tungsten is more of an advantage, as it allows a sufficiently high resistance to be generated with a wire that is not too thin - often as a double helix. Thin wire is sensitive to vibrations. A particularly compact luminous surface is achieved by an upright, flat, square filament of comparatively thick tungsten wire, which has to be operated with low voltage in slide projectors because of the low resistance. The melting point of a tungsten filament limits the operating temperature and thus the light color of an incandescent lamp without a color filter. At a high operating temperature, the longer the operating time, the tungsten recrystallizes and typically shortens and stiffens the filament, and when switching on and off, changes in length due to the temperature change occur. Incandescent filaments are therefore resiliently suspended with some scope for shortening.

In applications in the lamp industry, tungsten is characterized by its low thermal expansion, which means that it can be melted directly into special borosilicate glasses , for example as a contact bushing . Such glass-metal connections are extremely tight .

Tungsten inert gas welding

Because of its high resistance to corrosion, tungsten can also be used as a material for equipment in chemical plants. However, because of the poor machinability of tungsten (tungsten can only be welded using laser or electron beams), this form of application is rarely used. The same applies to a conceivable application in medical technology. In addition, electrodes for welding processes are made from tungsten, for example for resistance welding, especially when materials such as copper, bronze or brass are to be welded. Even with universal TIG welding ( tungsten inert gas welding ), an electrode consists of tungsten or an alloy thereof. These electrodes are not melted off in the welding process. The arc burns as a plasma in a protective gas between the electrode and the component. The filling material is supplied separately in the form of rods.

Due to its high melting point, tungsten is an important alloy component of tungsten-molybdenum alloys for turbine blades in the hot gas area of ​​the turbine of every jet engine.

Due to its high density, it is used for balance weights and for shielding against radiation. Although its density and thus the shielding effect are much higher than that of lead , it is used less often than lead for this purpose because it is more expensive and difficult to process.

The and lines of the characteristic X-ray radiation are around 59 keV and 67 keV, respectively. In scanning tunneling microscopy , tungsten is often used as the material for the probe tip. In physiology , especially neurophysiology , tungsten microelectrodes are used for extracellular recordings . ${\ displaystyle K _ {\ alpha}}$${\ displaystyle K _ {\ beta}}$

Tungsten is also used in the generation of X-rays as a target material in X-ray tubes or in linear accelerators . When accelerated electrons hit the cooled tungsten target, the X-rays are generated as bremsstrahlung . The X-rays generated in this way are used, among other things, in medicine for X-ray diagnostics .

### military

Because of the high density of tungsten, armor-piercing ammunition with a projectile core made of tungsten carbide is used in some armies instead of the depleted uranium , which is technically and collaterally deadly, and which is more deadly, from the uranium enrichment . During the Second World War , tungsten projectiles were first used by the German Wehrmacht and are still used today in the Bundeswehr. The Nazi regime went to great lengths to obtain large quantities of tungsten, which was considered essential for the war effort. Portugal exported tungsten to both the Allies and the German Empire during this period. In Norway, the Knabengrube produced MO concentrate for Germany. The mine was owned by IG Farben and Friedrich Krupp AG . The OKW reported in 1944 that it covered 25% of its needs from Finland and 40% from Norway.

### Sports

In sport, tungsten is used for high-quality dart barrels and for the tips of special arrows in archery . In hammer throwing , hammer heads were also made of tungsten to reduce air resistance and the radius of rotation. In addition, tungsten plates are used as additional weights in Formula 1 in order to achieve the prescribed minimum weight for Formula 1 cars. In sailing, too, it has been used in the keel bombs of large racers for some time . The water resistance is greatly reduced due to the greater density compared to conventional materials such as lead or cast iron. There are also rackets in tennis that have tungsten fibers incorporated into their carbon frame mesh. In this way, specific areas of the racket frame can be additionally stabilized in order to increase the playing precision. In golf , tungsten is sometimes used as a counterweight for smaller, more precise club heads.

In fly fishing , fishing lures are weighted down with pierced tungsten beads that are pushed onto the shank of the hook so that they dive faster and deeper. In fishing , especially spin fishing, tungsten is used as an environmentally friendly and even better sinking substitute for lead.

### Others

Ring (jewelry) made of tungsten carbide

Since the beginning of the 21st century, tungsten carbide, incorrectly referred to as tungsten, has also been used in jewelry (tungsten jewelry), e.g. B. rings processed. This is very easy to determine from the hardness and density. WC has a Mohs hardness of 9.5, tungsten only 7.5. So far, all jewelry parts on the market have been made from tungsten carbide.

Strings for musical instruments are sometimes wound with tungsten in order to increase their weight and thereby reduce the pitch.

Due to the similar density of tungsten and gold, there are repeated reports that tungsten (Tungsten) is used to counterfeit gold bars (tungsten core with gold coating).

## physiology

Tungsten is used as a positive bio-element by bacteria and archaea . Various enzymes that have tungsten as part of the cofactor from the hypertermophilic and strictly anaerobic archaeon Pyrococcus furiosus have been particularly well studied . Such tungsten enzymes could also be examined from anaerobic bacteria such as Eubacterium acidaminophilum . E. acidaminophilum is an amino acid fermenting bacterium that uses tungsten in the enzymes formate dehydrogenase and aldehyde oxidoreductase . In these organisms, tungsten replaces molybdenum because it is much more common in their natural environment (volcanic vents on the sea floor). But mesophilic facultative anaerobic microorganisms also have tungsten enzymes and have already been investigated.

### toxicology

According to the current state of knowledge, tungsten and its compounds are considered physiologically harmless. Lung cancer among workers in hard metal producing or processing plants is attributed to the cobalt that is also present .

In the animal model it was found that the largest amount of orally ingested tungsten compounds is quickly excreted in the urine . A small part of the tungsten goes into the blood plasma and from there into the erythrocytes . It is then deposited in the kidneys and the bone system. Three months after administration, most of the very small amounts of tungsten absorbed by the body are found in the bones.

In 2003 in Fallon / Nevada with 16 children suffering from leukemia since 1997 and in Sierra Vista / Arizona with nine children also suffering from blood cancer, two so-called cancer clusters - these are local areas with an above-average rate of cancer cases - were identified. In both places the drinking water has exceptionally high concentrations of tungsten. In the urine of the population significantly increased tungsten concentrations were detected. Both places are known for their tungsten ore deposits. In the following investigations by the Center for Disease Control (CDC), which lasted about a year , no direct connection between tungsten and leukemia could be established. Tungsten did not show any carcinogenic effects in any test method , and no cancer clusters were found in other places in Nevada with similarly high tungsten values ​​in the urine of the population.

## safety instructions

As a powder or dust it is highly flammable, in compact form it is non-combustible.

## links

### Oxides

Tungsten forms several oxides. Between the initial link:

and the end link:

there are also the following intermediate oxides:

• W 10 O 29 blue-violet, homogeneity range WO 2.92 -WO 2.88
• W 4 O 11 red-violet, homogeneity range WO 2.76 -WO 2.73
• W 18 O 49 , WO 2.72 , red-violet crystal powder. Semiconductor. Density 7.72 g / cm 3 , crystal structure: deformed DO 6 type, monoclinic , space group P 2 / m (space group No. 10) , lattice parameters: a = 1832 pm, b = 379 pm, c = 1404 pm, β = 115.2 °.
• W 20 O 50 , WO 2.50

### Use of the connections

Tungsten carbide is used as a neutron reflector in nuclear weapons to reduce the critical mass . Tungsten carbides ( hard metal ) are used in material processing due to their high hardness.

Tungstates are used to impregnate fabrics to make them flame-retardant.

Tungsten-containing paints are used in painting as well as in the ceramic and porcelain industries.

Lead tungstate is used as a modern scintillator in particle physics .

## Web links

Commons : Wolfram  - collection of images, videos and audio files
Wiktionary: Wolfram  - explanations of meanings, word origins, synonyms, translations

## Individual evidence

1. ^ 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 (Wolfram) , unless otherwise stated .
3. Entry on tungsten 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 13, 2020.
4. entry on tungsten at WebElements, https://www.webelements.com , accessed on June 13, 2020.
5. ^ NN Greenwood, A. Earnshaw: Chemistry of the elements. 1st edition. VCH, Weinheim 1988, ISBN 3-527-26169-9 , p. 1291.
6. Robert C. Weast (Ed.): CRC Handbook of Chemistry and Physics . CRC (Chemical Rubber Publishing Company), Boca Raton 1990, ISBN 0-8493-0470-9 , pp. E-129 to E-145. Values ​​there are based on g / mol and given in cgs units. The value specified here is the SI value calculated from it, without a unit of measure.
7. a b c 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 .
8. E. Lassner, W.-D. Schubert, E. Lüderitz, HU Wolf: Tungsten, Tungsten Alloys, and Tungsten Compounds. In: Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag, Weinheim 2005, doi: 10.1002 / 14356007.a27_229 .
9. Hütte , Das Ingenieurwissen 34th Edition, Table 16-6, Springer Vieweg 2012
10. a b c Entry on tungsten (powder) in the GESTIS substance database of the IFA , accessed on April 26, 2017(JavaScript required) .
11. Kluge: Etymological dictionary of the German language. 24th edition. Walter de Gruyter, Berlin 2002, ISBN 3-11-017473-1 , pp. 995-996.
12. ^ KH Wedepohl: The composition of the continental crust. In: Geochimica et Cosmochimica Acta . Volume 59, Issue 7, 1995, pp. 1217-1232; doi: 10.1016 / 0016-7037 (95) 00038-2 .
13. IMA / CNMNC List of Mineral Names - Tungsten (English, PDF 1.8 MB, p. 290).
14. a b c d
15. a b
16. a b c d
17. a b
18. The WOLFRAM company. In: wolfram.at. February 1, 2014, accessed August 26, 2018 .
19. Wolfram Bergbau- und Hütten-GmbH Nfg. KG ( Memento from September 15, 2013 in the Internet Archive ), accessed on April 21, 2009.
20. ^ Sverker Wahlberg: Nanostructured Tungsten Materials by Chemical Methods. Dissertation 2011, urn : nbn: se: kth: diva-42702
21. ^ Gerhard Gille, Andreas Meier: Recycling of refractory metals. In: Thomé-Kozmiensky / Goldmann (ed.): Recycling und Rohstoffe Vol. 5, TK-Verlag, Neuruppin 2012, ISBN 978-3-935317-81-8 , pp. 537-560.
22. Wolfram recycling profile. (PDF) Rewimet eV, p. 8 , accessed on April 21, 2020 .
23. a b Recycling of Tungsten - Current Share, Economic Limitations and Future Potential. (PDF; 4.21 MB) In: itia.info. International Tungsten Industry Association (ITIA), May 2018, p. 6 , accessed on August 25, 2018 .
24. ^
25. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 .
26. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1426.
27. Cristina Cozzini et al. a .: Detection of the natural α decay of tungsten. In: Physical Review C . 70, 064606, 2004, doi: 10.1103 / PhysRevC.70.064606 .
28. Tobias Gohlis: Seven times more gold. In: The time . No. 5, 2003.
29. ^ Robert Bohn (ed.): Neutrality and totalitarian aggression: Northern Europe and the great powers in World War II . Steiner, Stuttgart 1991, ISBN 978-3-515-05887-2 , from page 290 .
30. Beware of counterfeiting, tungsten in a gold jacket. manager magazin online, April 5, 2012, accessed October 24, 2012 .
31. A Kletzin: Tungsten in biological systems . In: FEMS Microbiology Reviews . tape 18 , no. 1 , March 1996, p. 5-63 , doi : 10.1016 / 0168-6445 (95) 00025-9 ( wiley.com [accessed July 29, 2019]).
32. M. Chan, S. Mukund, A. Kletzin, M. Adams, D. Rees: Structure of a hyperthermophilic tungstopterin enzyme, aldehyde ferredoxin oxidoreductase . In: Science . tape 267 , no. 5203 , March 10, 1995, p. 1463-1469 , doi : 10.1126 / science.7878465 .
33. Roopali Roy, Swarnalatha Mukund, Gerrit J. Schut, Dianne M. Dunn, Robert Weiss: Purification and Molecular Characterization of the Tungsten-Containing Formaldehyde Ferredoxin Oxidoreductase from the Hyperthermophilic Archaeon Pyrococcus furiosus: the Third of a Putative Five-Member Tungstoenzyme Family . In: Journal of Bacteriology . tape 181 , no. 4 , February 1999, p. 1171-1180 , PMID 9973343 , PMC 93494 (free full text).
34. D. Rauh et al. a .: Tungsten-containing aldehyde oxidoreductase of Eubacterium acidaminophilum. In: Eur J Biochem . , 271/2004, pp. 212-219; PMID 14686934 .
35. Martin Luther University Halle-Wittenberg, Wolframat -aufnahme Gram-positive anaerobic bacteria , accessed on November 23, 2007.
36. LE Bevers, PL Hagedoorn, WR Hagen: The bioinorganic chemistry of tungsten . In: Coord Chem Rev . tape 253 , 2009, p. 269–290 , doi : 10.1016 / j.ccr.2008.01.017 .
37. Fabian Arndt, Georg Schmitt, Agnieszka Winiarska, Martin Saft, Andreas Seubert: Characterization of an Aldehyde Oxidoreductase From the Mesophilic Bacterium Aromatoleum aromaticum EbN1, a Member of a New Subfamily of Tungsten-Containing Enzymes . In: Frontiers in Microbiology . tape 10 , January 31, 2019, doi : 10.3389 / fmicb.2019.00071 , PMID 30766522 , PMC 6365974 (free full text).
38. ^ Agency for Toxic Substances & Disease Registry: Toxicologic Profile for Tungsten , accessed February 22, 2009.
39. George Kazantzis, Per Leffler:? In: Handbook on the Toxicology of Metals. 3. Edition. 2007, pp. 871-879.
40. Wolfram jointly responsible for the development of leukemia? In: innovations-report.de , February 4, 2003.
41. ^
42. Heinrich Remy: Textbook of Inorganic Chemistry. Volume I + II, Leipzig 1973.
43. Georg Brauer: Handbook of preparative inorganic chemistry . 3., reworked. Edition. tape III . Enke, Stuttgart 1981, ISBN 3-432-87823-0 , pp. 1565 .
44. Heinrich Remy : Textbook of Inorganic Chemistry. Volume II, Akademische Verlagsgesellschaft Geest & Portig, Leipzig 1961, p. 218.