Tungstic acid, H2WO4, is formed as an amorphous yellow precipitate when an excess of hot hydrochloric acid is added to a solution of an alkali tungstate. If cold acid is used a white precipitate of the hydrate, H2WO4.H2O, results, from which the acid may be obtained either by boiling the mixture or by drying over sulphuric acid. It may also be prepared by the following methods:

1.By digesting a tungsten mineral with hydrochloric acid and then with aqua regia until the iron and manganese are dissolved and a yellow residue remains. This, after washing, is shaken with ammonia, which dissolves the free tungstic acid. The liquid is filtered, and on concentration tungstic acid crystallises out.

2.By heating the mineral under pressure with concentrated potash solution and lime, the tungstic acid being subsequently separated from the resulting solution by fractional precipitation.

3.By fusion of the finely powdered mineral with alkali carbonates, sodium chloride, or calcium chloride. The residue is treated with water and then with nitric or hydrochloric acid to decompose any insoluble tungstates. The acid may be further purified by solution in ammonia and precipitation with dilute nitric acid, or by means of chlorine.

The white hydrate, H2WO4.H2O, is produced by the decomposition of tungsten pentachloride, or the oxychlorides, in presence of moist air.

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Easy to Clean

Since the tungsten carbide trepanning tool is designed typically for cutting an annulus and leaving a centre core with large diameter, and does not remove the whole material in drilling operation, it generates fewer chips, and which ease the cleaning processes for the operator. With this easy and fast cleaning operation, sometimes the worker could continue their work without unnecessary stop.



Higher Accuracy

It is indicated that tungsten carbide trepanning tool owns very close tolerances, which enables the tool to achieve higher level of accuracy.

Specially, the cylinder eliminated by the tungsten carbide trepanning tool could be recycled and adopted as a raw material for other products.


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Hydrates of Tungsten Trioxide, Tungstic Acid. - Two well defined hydrates of tungsten trioxide are known:

1.A yellow monohydrate, WO3.H2O, and

2.A white dihydrate, WO3.2H2O. With bases, both hydrates produce the same series of salts, and the first appears to be the true acid, tungstic acid, H2WO4, whilst the second is the hydrate, H2WO4.H2O. Both are insoluble in water, but colloidal forms of the acid exist. Several other hydrates have been described, but except in the case of the complex hydrate known as metatungstic acid their existence has not been established.

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Tungsten carbide trepanning tool refers to a metal cutting tool that is used for toroidal shape cutting and deep hole boring. It is also used to grooves creating. It normally has one carbide tip and could be widely applied in various materials that are flat, such as sheet metal, rods, plates or any ferrous or non ferrous materials.

Since the tungsten carbide trepanning tool is typically for cutting an annulus and leave a centre core with large diameters, compared to a standard drill, it displays more economical and feasible in hole making application. Specially, the tungsten carbide trepanning tools usually require water to cool down the cutting tips and eliminate chips from the hole making processes.


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Tungstic acid is obtained by the action of strong acids on solutions of alkali metallic tungstates. It may also be prepared from the reaction between hydrogen carbonate and sodium tungstate.

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1、For the mordant, analytical reagents, catalysts, water treatment chemicals, manufacturing fireproof, waterproof material, and phosphorus tungstate, tungsten, boron salts.
2、For the manufacture of tungsten, tungsten acid, tungstate,etc.
3、For the mordant, pigments, dyes, inks.
4、As a weighting agent for fabric by weavers. This product is used as textile assistants. And a mixture of tungsten acid, ammonium sulfate, ammonium phosphate and other components used in fiber fire and water. This kind of fibers can be made into fireproof rayon and rayon. It can also be used in tanning leather.
5、As anti-corrosion coating for electroplating.
6、As a co-solvent playing a role in reducing firing temperature and complementary color when introducing enamel pigment.
7、For petroleum and aerospace manufacturing industry, aerospace materials.
 

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A rocket engine requires one or more current carrying loops surrounding the reaction region to produce the magnetic field that deflects the plasma and charged radiation from the drive pulses. Typically, these loops are made of superconductors, since any normal conductor would quickly melt or vaporize under the high currents needed to produce the field. The field coils are backed by a high tensile strength support to withstand the magnet-current back reaction from bursting the superconductor.

These field coils must be protected from the intense neutral radiation that the drive pulses produce. This is because a superconductor that becomes too hot will cease to superconduct. A common shielding design is a sheet of tungsten with a "V"-shaped cross section at a very narrow opening angle, resembling a knife-edge. The point of the V faces the radiation source, the field coil runs along the open top of the V. At very small angles of incidence, tungsten makes a good reflector of x-rays so that most x-rays are simply reflected at low angles away from the field coils and into space. Since tungsten atoms are much heavier than neutrons, a collision between a tungsten nucleus and a neutron results in the neutron rebounding with most of its original energy, delivering only 1% of its energy on average to the tungsten shield. This scatters the neutrons away from the field coils. The narrow opening angle means that the tungsten knife edge is essentially a sheet perpendicular to the incoming radiation, allowing a large radiator area compared to the cross section exposed to the radiation.

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Government regulations on lead and other hazardous substances in various electronic and electrical equipment are forcing medical device OEMs and others to find suitable substitutes for parts that have been manufactured from lead and other restricted materials, with plastics coming to the rescue.

A material has been found, that alternative to those being restricted by government regulations: poly-tungsten thermoplastic. This material can be machined and fabricated in a variety of configurations, and has the density of traditional metals without the safety issues associated with lead. Poly-tungsten is more durable than other lead substitutes and offers equal or better radiation-shielding capabilities in electronic and electrical products. Because it is malleable, poly-tungsten offers increased design flexibility and the opportunity to create molded parts in lieu of multi-part assemblies.

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Names

IUPAC name   dihydroxy-dioxotungsten

Other names   Orthotungstic acid

CAS Registry Number   7783-03-1

Properties

Chemical formula   H2WO4

Molar mass    249.853 g/mol

Appearance    yellow powder

Density   5.59 g/cm3

Melting point        100 °C (212 °F; 373 K) (decomposes)

Boiling point 1,473 °C (2,683 °F; 1,746 K)

Solubility in water        insoluble

Solubility      soluble in HF, ammonia

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

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Tungstic acid refers to hydrated forms of tungsten trioxide, WO₃. The simplest form, the monohydrate, is WO₃·H₂O, the dihydrate WO₃·2H₂O is also known. The solid state structure of WO3•H2O consists of layers of octahedrally coordinated WO₅(H₂O) units where 4 vertices are shared. The dihydrate has the same layer structure with the extra H₂O molecule intercalated between the layers. The monohydrate is a yellow solid and insoluble in water. The classical name for this acid is 'acid of wolfram'.

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