| Identification | More | [Name]
Tungsten | [CAS]
7440-33-7 | [Synonyms]
W
Tunsten
325mesh
W HC 40
ID(mm),7
#turns,9
Ht(mm),7
ID(mm),4
W 005358
W 000390
W 007929
W 000245
W 007910
W 000335
W 000310
W 005140
W 007915
W 005112
W 000090
W 000315
W 005155
W 000340
W 000200
W 000251
W 000255
W 005236
W 000275
W 005245
W 005137
W 005320
W 005130
W 005234
W 000160
W 000190
W 005362
W 005241
W 000279
W 005138
W 004500
W 005310
W 000317
W 000252
W 005305
W 000120
W 000270
W 000130
W 000219
W 007925
W 005135
W 005132
W 000225
W 008710
W 007930
W 005145
W 000221
W 000325
W 004600
W 000278
W 000170
W 004300
W 000150
W 005162
W 005315
W 000249
W 005115
W 000180
W 005170
W 000370
W 007932
W 005355
W 005308
W 005309
W 005200
W 005230
W 005148
W 005225
W 005260
W 005220
W 007928
W 007920
W 005330
W 006100
W 005808
W 007900
W 005240
W 005125
W 005105
W 005325
W 000220
W 000240
W 005131
W 008720
W 005335
W 005360
W 000247
W 005165
W 007941
W 005120
W 000330
W 000224
W 005250
W 005160
W 005351
W 007913
W 000215
W 005210
W 007935
W 005350
W 000250
W 005153
W 005110
W 005810
W 000345
W 000248
W 000226
W 000110
W 000100
W 000218
W 000290
W 005803
W 005147
W 005805
W 005802
W 000140
W 007940
W 005150
Ht(mm),9
#turns,8
ID(mm),9
TUNGSTEN
Ht(mm),14
ID(mm), 9
Ht(mm), 9
ID(mm), 4
Ht(mm), 7
ID(mm), 7
Tungsten1
Tungsten2
Tungsten3
Tungsten4
Tungsten5
# turns, 9
OD (mm), 7
OD (mm), 5
Ht(mm), 14
# turns, 8
mmTungsten
TSB 20X10ML
va[tungsten]
Tungsten rod
ID (MM), 4.8
Tungsten slug
tungsten atom
Tungsten Foil
TUNGSTEN BOAT
Tungsten wire
TungstenwireN
Zr in HNO3 5%
TUNGSTEN METAL
Tungsten, 99.9%
Tungsten, 12 μM
TUNGSTEN 99.98%
TUNGSTEN RIBBON
SOLUBLETUNGSTEN
Length (mm), 32
Wiredia(mm),0.51
Wiredia(mm),0.76
Tungsten powder
Tungsten Nanorods
Wireleads(cm),4.0
Tungsten solution
Length (MM), 24.7
Wireleads(cm),5.0
INSOLUBLETUNGSTEN
Wireleads(cm),3.5
TUNGSTEN STANDARD
TUNGSTEN CRUCIBLE
TUNGSTEN FILAMENT
TUNGSTEN ROD 99.9%
TungstenwireNmmdia
TUNGSTEN WIRE: 3N5
Wire dia(mm), 0.51
Tungsten rod5x30cm
Tungsten, Annealed
Wire dia(mm), 0.76
Tungsten powder（W）
10mg/l each of Ge
Wire leads(cm), 4.0
Wire leads(cm), 5.0
Wire leads(cm), 3.5
TungstenpowderNmesh
TUNGSTEN ROD 99.95%
TUNGSTEN BAR 99.50+%
TUNGSTEN PLATE 99.9%
Tungsten wire 99.95%
Tungstenpowdermicron
TUNGSTENMETAL,POWDER
TUNGSTEN DISCS 99.9%
TUNGSTEN BAR 99.95+%
Tungsten foil50x50mm
Tungsten wire basket
1000mg/l each of Mo
TUNGSTEN AA STANDARD
TUNGSTEN ICP STANDARD
Style, Varian plateau
Tungsten gauze75x75mm
TUNGSTEN GRANULAR 99%
TUNGSTEN PLATE 99.95%
TungstenpowderNmicron
Tungstenrodmmdiameter
TUNGSTEN DISCS 99.95%
TRYPTONE WATER 20X10ML
Tungsten foil100x500mm
Tungsten foil100x100mm
Tungsten foil150x300mm
Tungsten, 99.9%, 12 μm
Tungsten, powder, 12 μM
Tungsten gauze300x300mm
TUNGSTEN POWDER (99.9%)
Tungsten gauze150x150mm
Tungsten metal-325 mesh
TUNGSTEN GRANULAR 99.5+%
Graphite Furnace AA Tube
TUNGSTEN POWDER (99.95%)
Tungsten powder,spherical
Tungsten, Powder 100 Mesh
TUNGSTEN ICP/DCP STANDARD
TUNGSTEN STANDARD SOLUTION
TUNGSTEN POWDER: 99.9%, 3N
TUNGSTEN WIRE: 99.95%, 3N5
TungstenPowder99%(325Mesh)
Tungsten Rod 2 mm x 200 mm
Tungsten Powder 2.8 micron
Tungsten Powder 8-9 micron
Tungsten , wire , dark (W)
Tungsten powder (200 mesh)
Tungsten solution 1000 ppm
Tungsten ingot， mirror (W)
Tungsten , wire , white (W)
Tungsten, powder, 12 micron
Tungsten Rod 10 mm diameter
TUNGSTEN POWDER EXTRA PURE
Tungsten Rod 15 mm diameter
Tungsten Rod 20 mm diameter
TUNGSTEN POWDER 99.9% 100NM
TUNGSTEN POWDER: 99.9%, 3N8
Tungsten Rod 4.0 mm diameter
Tungsten Rod 8.0 mm diameter
Tungsten Rod 3.0 mm diameter
Tungsten Rod 2.5 mm x 500 mm
Tungsten Rod 5.0 mm diameter
Tungsten,99.9%,powder, 12 μm
Tungsten powder , sphere (W)
Tungsten rod annealed 99.98%
Tungsten ISO 9001：2015 REACH
Tungsten, nanopowder, >=99.9%
Tungsten Wire 0.1 mm diameter
Tungsten Wire 0.2 mm diameter
Tungsten Wire 0.3 mm diameter
Tungsten Wire 0.5 mm diameter
Tungsten Wire 0.7 mm diameter
Tungsten Wire 1.0 mm diameter
Tungsten Wire 1.4 mm diameter
Tungsten Wire 2.0 mm diameter
TUNGSTEN METAL POWDER W HC 40
TungstenrodannealedNmmdiacagcm
Tungsten Wire 0.01 mm diameter
Tungsten Wire 0.25 mm diameter
Tungsten ion standard solution
Tungsten, powder, 12 μm, 99.9%
TUNGSTEN FINE POWDER 99+ 100 G
Tungsten, 99.90%, powder, 12 μm
TUNGSTEN, AAS STANDARD SOLUTION
Tungsten, approx. 99,5%, powder
TUNGSTEN SINGLE ELEMENT STANDARD
TUNGSTEN WIRE (99.95%) 0.2MM DIA
TUNGSTEN SPUTTERING TARGET 99.9%
TUNGSTEN WIRE (99.95%) 0.5MM DIA
Tungsten Pellets 6.35 x 3.175 mm
Tungsten, Powder 100 Mesh 99.98%
Tungsten slug,6MM dia×6MM length.
Tungsten powder , crystalline (W)
TUNGSTEN SPUTTERING TARGET 99.95%
TUNGSTEN PLASMA EMISSION STANDARD
TUNGSTEN WIRE (99.95%) 0.25MM DIA
TUNGSTEN WIRE (99.95%) 0.05MM DIA
TUNGSTEN, PLASMA STANDARD SOLUTION
TUNGSTEN ROD ANNEALED: 99.98%, 3N8
TUNGSTEN WIRE (99.95%) 0.127MM DIA
TUNGSTEN, POWDER, 12 MICRON, 99.9%
Tungsten and its compounds soluble
TUNGSTEN, ROD, 4.0MM DIAM., 99.99%
Tungsten, powder, 12 , 99.9% 100GR
Tungsten rod, 4.0mm (0.16 in.) dia.
Tungsten rod, 12.7mm (0.5 in.) dia.
Tungsten Foil /0.025x50x50mm/99.95%
TUNGSTEN ATOMIC ABSORPTION STANDARD
TUNGSTEN AA SINGLE ELEMENT STANDARD
Tungsten Target /Φ50.8x6.3mm/99.95%
nm ,99.9% metals basistungsten atom
TUNGSTEN FOIL 1.0MM THICK 99.9+%
TUNGSTEN, WIRE, 0.5MM DIAM., 99.9+%
Tungsten rod, 1.5mm (0.06 in.) dia.
Tungsten Rod 1 mm diameter x 330 mm
Tungsten, powder, 12 micron, 99.90%
TUNGSTEN, WIRE, 1.0MM DIAM., 99.99%
TUNGSTEN, FOIL, 0.5MM THICK, 99.9+%
TUNGSTEN, WIRE, 0.25MM DIAM., 99.9+%
TUNGSTEN, FOIL, 0.25MM THICK, 99.9+%
Tungsten and its compounds insoluble
Tungsten Target /Φ101.6x3.2mm/99.95%
Tungsten Target /Φ101.6x6.3mm/99.95%
Tungsten Foil /0.05x100x100mm/99.95%
Tungsten Foil /0.10x100x100mm/99.95%
Tungsten Foil /0.20x100x100mm/99.95%
Tungsten Foil /0.50x100x100mm/99.95%
Tungsten Foil /1.00x100x100mm/99.95%
TUNGSTEN ATOMIC SPECTROSCOPY STANDARD
Multi-Element Solution - 5 components
TUNGSTEN, FOIL, 0.127MM THICK, 99.9+%
Tungsten wire, 0.2mm (0.008 in.) dia.
Tungsten wire, 0.25mm (0.01 in.) dia.
Tungsten wire, 0.75mm (0.03 in.) dia.
Tungsten wire, 1.4mm (0.055 in.) dia.
Tungsten Powder 5 micron (Mo < 1 ppm)
TUNGSTEN, POWDER, <10 MICRON, 99.99+%
TUNGSTEN: 99.995%, POWDER, -90 MICRON
TUNGSTEN: 99.9999%, POWDER, -90 MICRON
BPW BUFFERED PEPTONWATER 5 L KANNISTER
TUNGSTEN, POWDER, CA. 100 MESH, 99.95%
Tungsten Target /1.00x100x100mm/99.95%
Tungsten wire, 1.25mm (0.049 in.) dia.
Tungsten foil, 0.25mm (0.01 in.) thick
Tungsten Metal, 100 - 200 Mesh, Powder
Tungsten foil, 0.05mm (0.002 in.) thick | [EINECS(EC#)]
231-143-9 | [Molecular Formula]
W | [MDL Number]
MFCD00011461 | [Molecular Weight]
183.84 | [MOL File]
7440-33-7.mol |
| Chemical Properties | Back Directory | [Appearance]
Tungsten is a hard, brittle, steel-gray to tinwhite
metal or fine powder. | [Melting point ]
3410 °C (lit.) | [Boiling point ]
5660 °C (lit.) | [density ]
19.3 g/mL at 25 °C(lit.)
| [vapor pressure ]
0Pa at 3000℃ | [Fp ]
-23 °C | [storage temp. ]
no restrictions. | [form ]
wire
| [color ]
Silver-gray | [Specific Gravity]
19.3 | [Stability:]
Stable. Dust is flammable, though not likely to present a hazard if normal good practice is used. | [Resistivity]
4.9 μΩ-cm, 20°C | [Water Solubility ]
insoluble | [Merck ]
13,9884 | [Exposure limits]
ACGIH: TWA 2 ppm; STEL 4 ppm
OSHA: TWA 2 ppm(5 mg/m3)
NIOSH: IDLH 25 ppm; TWA 2 ppm(5 mg/m3); STEL 4 ppm(10 mg/m3) | [History]
In 1779 Peter Woulfe examined the mineral now
known as wolframite and concluded it must contain a new substance.
Scheele, in 1781, found that a new acid could be made
from tung sten (a name first applied about 1758 to a mineral
now known as scheelite). Scheele and Berman suggested the
possibility of obtaining a new metal by reducing this acid. The
de Elhuyar brothers found an acid in wolframite in 1783 that
was identical to the acid of tungsten (tungstic acid) of Scheele,
and in that year they succeeded in obtaining the element by
reduction of this acid with charcoal. Tungsten occurs in wolframite,
(Fe, Mn)WO4; scheelite, CaWO4; huebnerite, MnWO4;
and ferberite, FeWO4. Important deposits of tungsten occur in
California, Colorado, Bolivia, Russia, and Portugal. China is
reported to have about 75% of the world’s tungsten resources.
Natural tungsten contains five stable isotopes. Thirty-two
other unstable isotopes and isomers are recognized. The metal
is obtained commercially by reducing tungsten oxide with hydrogen
or carbon. Pure tungsten is a steel-gray to tin-white
metal. Very pure tungsten can be cut with a hacksaw, and can
be forged, spun, drawn, and extruded. The impure metal is
brittle and can be worked only with difficulty. Tungsten has the
highest melting point of all metals, and at temperatures over
1650°C has the highest tensile strength. The metal oxidizes
in air and must be protected at elevated temperatures. It has
excellent corrosion resistance and is attacked only slightly by
most mineral acids. The thermal expansion is about the same
as borosilicate glass, which makes the metal useful for glass-to-metal seals. Tungsten and its alloys are used extensively for
filaments for electric lamps, electron and television tubes, and
for metal evaporation work; for electrical contact points for
automobile distributors; X-ray targets; windings and heating
elements for electrical furnaces; and for numerous spacecraft
and high-temperature applications. High-speed tool steels,
Hastelloy?, Stellite?, and many other alloys contain tungsten.
Tungsten carbide is of great importance to the metal-working,
mining, and petroleum industries. Calcium and magnesium
tungstates are widely used in fluorescent lighting; other salts
of tungsten are used in the chemical and tanning industries.
Tungsten disulfide is a dry, high-temperature lubricant, stable
to 500°C. Tungsten bronzes and other tungsten compounds
are used in paints. Zirconium tungstate has found recent applications
(see under Zirconium). Tungsten powder (99.999%)
costs about $2900/kg. | [CAS DataBase Reference]
7440-33-7(CAS DataBase Reference) | [NIST Chemistry Reference]
Tungsten(7440-33-7) | [EPA Substance Registry System]
7440-33-7(EPA Substance) |
| Safety Data | Back Directory | [Hazard Codes ]
F,Xi,N,Xn | [Risk Statements ]
R11:Highly Flammable.
R36/38:Irritating to eyes and skin .
R67:Vapors may cause drowsiness and dizziness.
R65:Harmful: May cause lung damage if swallowed.
R62:Possible risk of impaired fertility.
R51/53:Toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment .
R48/20:Harmful: danger of serious damage to health by prolonged exposure through inhalation .
R38:Irritating to the skin. | [Safety Statements ]
S6:Keep under ... (inert gas to be specified by the manufacturer) .
S26:In case of contact with eyes, rinse immediately with plenty of water and seek medical advice .
S36:Wear suitable protective clothing .
S62:If swallowed, do not induce vomiting: seek medical advice immediately and show this container or label .
S61:Avoid release to the environment. Refer to special instructions safety data sheet .
S36/37:Wear suitable protective clothing and gloves . | [RIDADR ]
UN 3089 4.1/PG 2
| [WGK Germany ]
-
| [RTECS ]
YO7175000
| [TSCA ]
Yes | [HazardClass ]
4.1 | [PackingGroup ]
III | [HS Code ]
81011000 | [Safety Profile]
An inhalation hazard.
Mildly toxic by an unspecified route. An
experimental teratogen. Experimental
reproductive effects. A skin and eye irritant.
Flammable in the form of dust when
exposed to flame. The powdered metal may
ignite on contact with air or oxidants (e.g.,
bromine pentafluoride, bromine, chlorine
trifluoride, potassium perchlorate, potassium
dichromate, nitryl fluoride, fluorine, oxygen
difluoride, iodine pentafluoride, hydrogen
sulfide, sodlum peroxide, lead (IV)oxide).
See also TUNGSTEN COMPOUNDS and
POWDERED METALS. | [Hazardous Substances Data]
7440-33-7(Hazardous Substances Data) |
| Hazard Information | Back Directory | [Reactivity Profile]
TUNGSTEN is stable at room temperature. Very slowly attacked by nitric acid, sulfuric acid, and aqua regia. Dissolved by a mixture of hydrofluoric acid and nitric acid. No reaction with aqueous bases. Attacked rapidly by motlen alkaline melts such as Na2O2 or KNO3/NaOH. Vigorous reactions with bromine trifluoride and chlorine trifluoride. Becomes incandescent upon heating with lead oxide; becomes incandescent in cold fluorine and with iodine pentafluoride. Combustible in the form of finely divided powder and may ignite spontaneously. | [Potential Exposure]
Tungsten is used in ferrous and
nonferrous alloys, and for filaments in incandescent lamps.
It has been stated that the principal health hazards from
tungsten and its compounds arise from inhalation of aerosols
during mining and milling operations. The principal
compounds of tungsten to which workers are exposed are
ammonium paratungstate, oxides of tungsten (WO3, W2O5,
WO2); metallic tungsten; and tungsten carbide. In the production
and use of tungsten carbide tools for machining, exposure
to the cobalt used as a binder or cementing substance
may be the most important hazard to the health of the
employees. Since the cemented tungsten carbide industry
uses such other metals as tantalum, titanium, niobium, nickel,
chromium, and vanadium in the manufacturing process, the
occupational exposures are generally to mixed dust. | [First aid]
If this chemical gets into the eyes, remove any
contact lenses at once and irrigate immediately for at least
15 minutes, occasionally lifting upper and lower lids. Seek
medical attention immediately. If this chemical contacts the
skin, remove contaminated clothing and wash immediately
with soap and water. Seek medical attention immediately.
If this chemical has been inhaled, remove from exposure,
begin rescue breathing (using universal precautions, including
resuscitation mask) if breathing has stopped and CPR if
heart action has stopped. Transfer promptly to a medical
facility. When this chemical has been swallowed, get medical
attention. Give large quantities of water and induce
vomiting. Do not make an unconscious person vomit. | [Shipping]
UN3089 Metal powders, flammable, n.o.s.,
Hazard Class: 4.1; Labels: 4.1-Flammable solid. UN3189
Metal powder, self heating, n.o.s., Hazard Class: 4.2;
Labels: 4.2-Spontaneously combustible material. | [Incompatibilities]
Tungsten: The finely divided powder is
combustible and may ignite spontaneously in air.
Incompatible with bromine trifluoride; chlorine trifluoride;
fluorine, iodine pentafluoride. | [Description]
Tungsten was recognized as a distinct element in 1779 by
Peter Woulfe, but not isolated until 1783, by Jose and Fausto
d’Elhuyar. The average tungsten concentration in the earth’s
crust is ~0.006%. Tungsten occurs naturally as tungstate,
mainly in compounds such as wolframites and scheelites. | [Waste Disposal]
Recovery of tungsten from
sintered metal carbides, scrap and spent catalysts has been
described as an alternative to disposal. | [Isotopes]
There are 36 isotopes of tungsten. Five are naturally stable and therefore contributeproportionally to tungsten’s existence on Earth, as follows: W-180 = 0.12%, W-182 = 26.50%, W-183 = 14.31%, W-184 = 30.64%, and W-186 = 28.43%. The other31 isotopes are man-made in nuclear reactors and particle accelerators and have halflivesranging from fractions of a second to many days. | [Origin of Name]
Tungsten was originally named “Wolfram” by German scientists, after
the mineral in which it was found, Wolframite—thus, its symbol “W.” Later, Swedish scientists
named it tung sten, which means “heavy stone,” but it retained its original symbol
of “W.” | [Occurrence]
Tungsten is the 58th most abundant element found on Earth. It is never found in 100%pure form in nature. Its major ore is called wolframite or tungsten tetroxide, (Fe,Mn)WO4,which is a mixture of iron and manganese and tungsten oxide. During processing, the ore ispulverized and treated with strong alkalis resulting in tungsten trioxide (WO3), which is thenheated (reduced) with carbon to remove the oxygen. This results in a variety of bright colorchanges and ends up as a rather pure form of tungsten metal: 2WO3 + 3C → 2WO + 3CO2.Or, if hydrogen is used as the reducing agent, a more pure form of metal is produced: WO3+ 3H2 → W + 3H2O.
Tungsten ores (oxides) are found in Russia, China, South America, Thailand, and Canada.In the United States, the ores are found in Texas, New Mexico, Colorado, California, Arizona,and Nebraska. | [Characteristics]
Tungsten is considered part of the chromium triad of group six (VIB), which consists of24Cr, 42Mo, and 74W. These elements share many of the same physical and chemical attributes.Tungsten’s high melting point makes it unique insofar as it can be heated to the point thatit glows with a very bright white light without melting. This makes it ideal as a filamentfor incandescent electric light bulbs. Most metals melt long before they reach the point ofincandescence.
Chemically, tungsten is rather inert, but it will form compounds with several other elementsat high temperatures (e.g., the halogens, carbon, boron, silicon, nitrogen, and oxygen).Tungsten will corrode in seawater. | [Definition]
A transition metal
occurring naturally in wolframite
((Fe,Mn)WO4) and scheelite (CaWO4). It
was formerly called wolfram. It is used as
the filaments in electric lamps and in various
alloys.
Symbol: W; m.p. 3410 ± 20°C; b.p.
5650°C; r.d. 19.3 (20°C); p.n. 74; r.a.m.
183.84. | [Definition]
tungsten: Symbol W. A white orgrey metallic transition element(formerly called wolfram); a.n. 74;r.a.m. 183.85; r.d. 19.3; m.p. 3410°C;b.p. 5660°C. It is found in a numberof ores, including the oxides wolframite,(Fe,Mn)WO4, and scheelite,CaWO4. The ore is heated with concentratedsodium hydroxide solutionto form a soluble tungstate. Theoxide WO3 is precipitated from thisby adding acid, and is reduced to themetal using hydrogen. It is used invarious alloys, especially high-speedsteels (for cutting tools) and in lampfilaments. Tungsten forms a protectiveoxide in air and can be oxidizedat high temperature. It does not dissolvein dilute acids. It forms compoundsin which the oxidation stateranges from +2 to +6. The metal wasfirst isolated by Juan d’Elhuyer andFausto d’Elhuyer (1755–1833) in1783. | [Production Methods]
Tungsten occurs principally in the minerals wolframite (Fe,Mn)WO4, scheelite (CaWO4), ferberite (FeWO4), and hubnerite (MnWO4). These ores are found in China, Russia, Canada, Austria, Africa, Bolivia, Columbia, and Portugal. Wolframite is the most important oreworldwide; scheelite is the principal domestic U.S. ore. Scheelite, when pure, contains 80.6% WO3, the most common impurity being MoO3. The percentages of FeO and MnO in wolframite vary considerably; hubnerite is the term applied to ore containing more than 20% MnO and ferberite and to ore containing more than 20% FeO. Intermediate samples are called wolframite. | [Hazard]
Tungsten dust, powder, and fine particles will explode, sometimes spontaneously, in air.The dust of many of tungsten’s compounds is toxic if inhaled or ingested. | [Health Hazard]
The soluble compounds of
tungsten are distinctly more toxic than the
insoluble forms. | [Flammability and Explosibility]
Flammable | [Carcinogenicity]
Tungsten has been suspected to be involved in the occurrence of childhood leukemia, with the discovery of a cluster of diseases in Fallon, Nevada, associated with elevated levels of tungsten in urine and drinking water. The exact environmental source of exposure to tungsten was not clearly identi?ed and there is little evidence for an etiological role of tungsten in eliciting leukemia. | [Environmental Fate]
Tungsten in the environment largely exists as ions in
compounds and primarily insoluble solids. The potential for
particulate matter to spread is low as wet and dry deposition
removes it from the atmosphere. If released to air, most
tungsten compounds have low vapor pressures and are expected
to exist solely in the particulate phase in the ambient
atmosphere. Volatization is not expected to be an important
fate process. | [Purification Methods]
Clean the solid with conc NaOH solution, rub it with very fine emery paper until its surface is bright, wash it with previously boiled and cooled conductivity water and dry it with filter paper. [Hein & Herzog in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol II p 1417 1965.] | [Toxicity evaluation]
Reported inhalation effects are probably due to cobalt in
exposures, a competitive inhibitor of molybdenum utilization. |
| Questions And Answer | Back Directory | [History and Occurrence]
The discovery of tungsten occurred in the 1780’s. Peter Woulfe, in 1779, while examining the mineral now known as wolframite, established that it contained a new substance. Around the same time, Swedish chemist Carl Wilhelm Scheele was investigating another mineral, scheelite. This mineral was known at that time as tungsen, which in Swedish meant heavy stone. Scheele, in 1781, determined that tungsen contained lime and a new acid similar to molybdic acid. This new acid was tungstic acid. Scheele and Bergman predicted that reduction of this acid could produce a new metal. Two years later in 1783, J. J. de Elhuyar and his brother F. deElhuyar of Spain first prepared metallic tungsten from wolframite. They derived an acid from wolframite which was similar to acid obtained by Scheele from tungsten (scheelite), and succeeded in producing a new metal by reduction of this acid with charcoal. Also, they determined that the mineral wolframite contained iron and manganese. The metal took over the old name of its mineral tungsten. Also the metal is known as wolfram, derived from the name of its other mineral, wolframite. The word wolfram originated from the wolf-like nature of the mineral that it devoured tin during the tin smelting operation causing low recoveries. The element was given the symbol W for its old name wolfram.
Tungsten is widely distributed in nature, occurring in several minerals. It is found in scheelite, CaWO4; wolframite, (Fe,Mn)WO4; huebnerite, MnWO4; ferberite, FeWO4; tungstite, H2WO4; and cuprotungstite, CuWO4. Its abundance in the earth’s crust is estimated to be 1.25 mg/kg and average concentration in seawater is about 0.1 μg/L.
| [Chemical Properties]
Tungsten is a steel-gray to tin-white metal. It is a heavy metal. It is a very hard metal that is stable in dry air at ordinary temperatures. Although very difficult to work with, tungsten can be cut with a hacksaw, forged, or spun. Commercially, tungsten is obtained via the reduction of tungsten oxide with hydrogen or carbon. Due to its hardness, tungsten has the highest boiling point and highest tensile strength of all metals. Although the metal shows resistance to corrosion, it can oxidize in air with an increase in temperature (Robert and Golden, 1980; Gbaruko and Igwe, 2007).
Tungsten is a very hard metal with similar properties and functions to molybdenum and chromium. Unlike molybdenum, tungsten is not an essential trace metal. However, tungsten is a competitive inhibitor of molybdenum in bacteria, plants, and animals (Hainline and Rajagopalan, 1983; Smith, 1991).
| [Uses]
Industrially tungsten is a very important metal having wide applications. This is due to many outstanding physical properties. Among all the metals, tungsten has the highest melting point and the lowest vapor pressure. Also at high temperatures it has the highest tensile strength. The metal has an excellent resistance to corrosion and attack by mineral acids. Also it has a thermal expansion comparable to that of borosilicate glass.
Tungsten is extensively used in alloy steel to impart high strength and hardness to steel. Heavy metal alloys with nickel, copper and iron, produced by powder metallurgy, can be made machineable and moderately ductile for applications as high-density materials. Tungsten carbides are extremely hard and are excellent cutting materials. They are used extensivly in the tool and die industry for drilling and cutting tools, sand blasting nozzels, armor-piercing bullets, and studs to increase traction of tires.
Among the nonferrous tungsten alloys, its alloys with copper and silver are used as electrical contacts and switches and with molybdenum in aerospace components.
Unalloyed tungsten has several major applications. An important use is in the electric lamp filaments for light bulbs. Also, it is used as electrodes in arcwelding, in heating elements for high-temperature furnaces, in electron and television tubes, in glass-tometal seals, and in solar energy devices.
| [Physical Properties]
Grayish-white metal; body-centered cubic crystalline structure; density 19.3 g/cm3; melts at 3,422°C; vaporizes at 5,555°C; vapor pressure 1 torr at 3,990°C; electrical resistivity 5.5 microhm-cm at 20°C; modulus of elasticity about 50 to 57 × 106 psi (single crystal); Poisson’s ratio 0.17; magnetic susceptibilty +59 × 10–6; thermal neutron absorption cross section 19.2 + 1.0 barns (2,200m/sec); velocity of sound, about 13,000 ft/sec; insoluble in water; practically insoluble in most acids and alkalies; dissolves slowly in hot concentrated nitric acid; dissolves in saturated aqueous solution of sodium chlorate and basic solution of potassium ferricyanide; also solubilized by fusion with sodium hydroxide or sodium carbonate in the presence of potassium nitrate followed by treatment with water.
| [Production]
Tungsten is recovered mostly from mineral scheelite and wolframite. The recovery process depends on the mineral, the cost, and the end use; i.e., the commercial products to be made. Typical industrial processes have been developed to convert tungsten ores to tungsten metal and alloy products, tungsten steel, non-ferrous alloys, cast and cemented tungsten carbides, and tungsten compounds. A few processes are mentioned briefly below.
The first step in recovery is opening the ore. If the ore is scheelite, CaWO4, it is digested with hydrochloric acid:
CaWO4 + 2HCl → H2WO4 + CaCl2
Tungstic acid, H2WO4 precipitates out. The precipitate is washed and dissolved in sodium or ammonium hydroxide solution during heating:
H2WO4 + 2NaOH → Na2WO4 + 2H2O
Sodium tungstate is crystallized, separated from any impurities in the solution, and digested again with hydrochloric acid to form tungstic acid in purified form. The pure acid is dried, ignited and reduced with carbon to form tungsten powder from which most non-ferrous alloys are made.
| [Reactions]
Tungsten exhibits several oxidation states, +6 being most stable. Compounds of lower oxidation states show alkaline properties. They also are less stable than those produced in higher oxidation states. Tungsten exhibits remarkable stability to practically all substances at ambient temperature. The metal is not attacked by nonoxidizing mineral acid. Concentrated hydrochloric acid, dilute sulfric acid and hydrofluoric acid attack the metal very slightly even when heated to 100°C. Tungsten is stable to dilute or concentrated nitric acid under cold conditions. Cold acid passivates the surface forming a slight oxide film. Hot dilute nitric acid corrodes the metal, while hot concentrated acid slowly dissolves bulk metal but rapidly oxidizes metal in powder form. At room temperature, aqua regia oxidizes metal only on the surface forming tungsten trioxide. A hydrofluoric-nitric acid mixture rapidly oxidizes tungsten to its trioxide. Chromic acid-sulfuric acid mixture does not react with tungsten metal in ductile form at ambient temperatures.
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