Ammonium Metatungstate SEM Micrograph

AMT-image

Ammonium metatungstate is also named AMT, which is a kind of white crystal powder. AMT is the raw material for making tungsten product, and also widely used in alloyed steel, fireproof industries. Further more, it is a good tungsten based flux in oil chemical and ceramic industries. The manufacturing standard of AMT in China is GB/T 23368, which is also used for measuring the content of ammonium metatungstate. Based on different manufacturing degree, the products manufactured out by factories have performed different chemical contents. Standard used manufacturing ammonium metatungstate, AMT is GB/T 23368. The content of WO₃ is 90.00% in most Chinese manufacturers, but 91.4~91.5% for Chinatungsten Online. For the different crystallized conditions, AMT can be analyzed as (NH₄)6H₂W₁₂OnH₂O, (NH₄)₆H₂W₁₂O₄₀.XH₂O and (NH₄)₆H₂W₁₂O₄₀.

SEM micrograph is short for Scanning Electron Microscope, a kind of scanning equipment using for micrograph by multiplying objects, which can be metal, powder, vegetables etc. Ammonium metatungstate is one of can-be scanned products. After scanning, the powder of AMT is showing ball shape with inner empty. All the balls are gathered together when the multiply value is low, but with gap when the value large enough, which means that the molecule of AMT are separate actually.

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Ammonium Metatungstate Producing Method

ammonium metatungstate photo

Ammonium metatungstate producing method includes neutralization method, tungstic acid method, thermal decomposition method, solvent extraction method and ion exchange method.

Neutralization method uses secondary ammonium metatungstate and nitrate as the raw material to produce metatungstate.

Tungstic acid method using ammonia tungstate tungstic acid dissolved, add a boil deionized water in the stirring, heating by ammonia, Ph=8, in the boiling solution by adding acetic acid.

Thermal decomposition method combines ammonium paratungstate and a small amount of citric acid catalyst after mixing into the far infrared, rotary furnace, controlled thermal decomposition temperature 200 ～ 280 ℃, decomposition of about 1 h.

Solvent extraction using ammonium tungstate solution and organic extractant phosphoric acid: two (2- ethylhexyl) ester (D2EHPA) or phosphoric acid butyl ester three (TBP) and kerosene solvent to form organic phase, extract ammonium ion from ammonium tungstate solution.

Ion exchange method uses ammonium paratungstate as raw material, heating ammonium paratungstate from 1 to 8 h at 130 ~ 140 ℃, the resultant tune into a paste, to 80 ~ 100 ℃ boiling for 2 ~ 6 h, generates ammonium metatungstate solution. And then obtain the product through concentrating crystallization, filtration and drying.

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Ammonium Metatungstate Preparing Tungsten Trioxide

Ammonium metatungstate is a tungsten chemical in the form of highly soluble hydrated crystals, it is white or slightly yellow crystals which has no harmful components and slightly acidic. Due to its solubility in water, it can be used as raw material to produce tungsten trioxide.

ammonium metatungstate picture

Use ammonium paratungstate as raw material and heat to 220-280℃. After that it will lose ammonium and crystal water and transform into ammonium metatungstate. Continuously heat ammonium metatungstate to 600℃ until it loses all ammonium and crystal water, cool it down and crystallize, after spray drying it turns into yellow tungsten trioxide.

Ammonium metatungstate preparing tungsten trioxide is easy to operate, the finished product is of good uniformity. Tungsten trioxide can be used to made tungsten product and shielding materials which is widely used in industry.

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Ammonium Paratungstate Preparing Ammonium Metatungstate

ammonium metatungstate powder picture

Ammonium metatungstate is an important tungsten-containing compound, mainly used as catalyst in petroleum cracking, organic synthesis, nitration, and so on. With the rapid development of petroleum refining, petrochemical engineering and other industries, the ammonium metatungstate usage is increasing very fast. In the prior art, ammonium paratungstate is used as a raw material, and a crystallization process is utilized for the preparation of ammonium metatungstate; this process is expensive, costly and energy-consuming, and the obtained product is unstable in quality, particularly the solubility is poor.

A process for preparing ammonium metatungstate using ammonium paratungstate as raw material comprising: (A) leaching wet ammonium paratungstate with nitric acid to obtain a dilute solution of ammonium metatungstate; (B) concentrating the dilute solution of ammonium metatungstate to be a concentrated solution of ammonium metatungstate; and (C) spray-drying the concentrated solution of ammonium metatungstate to obtain powder of ammonium metatungstate.

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Ammonium Metatungstate Molecular Weight

Ammonium metatungstate molecular weight generally refers to relative molecular mass of ammonium metatungstate (AMT), molecular weight differences between each other depending on its moisture content; while according the formula of (NH₄)₆H₂W₁₂O₄₀.XH₂O, the anhydrous basis of molecular weight should be 2956.08.
Wherein the relative molecular mass of each element is：N=14, H=1, W=183.84, O=16;
then Mr(AMT)=14*6+1*26+183.84*12+16*40=2956.08.

AMT molecular structure picture

Sum of relative atomic mass (Ar) of each element in the formula is the relative molecular mass, which represented by symbol of Mr. Relative molecular mass equal to the molar mass in value, but in different units. The unit of relative molecular mass is "1", while the unit of molar mass is g/mol. H₂O is the oxide with the minimum relative molecular mass, however, as for the polymer, its relative molecular mass can up to tens or even hundreds of thousands.
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What Is Ammonium Metatungstate

What is ammonium metatungstate? Ammonium metatungstate is a white crystalline powder, soluble in water, insoluble in aocohol.
Chinese Name: 偏钨酸铵

ammonium metatungstate picture

Abbreviation: AMT
Molecular Formula：H₈N₂O₄W；
Chemical Formula：(NH₄)₆H₂W₁₂O_{40.XH2O；
Molecular Weight：283.9145；
CB No.：CB41411564；
EC No.：234-364-9；
CAS No.: 14311-52-5；
HS Code：28418040；
Solubility(Water)：300g/100ml；
W valance in AMT： +6
W content in AMT：72%
Ammonium metatungstate has no harmful components, it has subacidity, often used in the preparation of tungsten products, catalyst in petroluem industry, nuclear shielding material, also ceramic industry, steel alloy, fire resistant fiber and inhibiter. In recent years, it is also used in emerging industry like semiconductor and thin film.
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