Ion exchange with ammonium paratungstate as raw material, ion exchange Prepared metatungstate: heating paratungstate 1 ~ 8 h at 130 ~ 140 ℃, the resultant slurried, boil 2 ~ 6 h at 80 ℃ ~ 100 ℃ generate metatungstate solution. Then concentrated

Neutralization with PAT and nitrate as raw material provisioning metatungstate: ammonium paratungstate deionized water and slurry containing ammonium citrate dubbed WO312% ~ 30% concentration. Press paratungstate: nitric acid = 1:20 3% to 5% dilute nitric acid to ammonium paratungstate slurry, controling solid-liquid ratio of 1: (3 ~ 4), Ph value rang from 2 to 4, dissolved by heating, and the solution relative density about 1.18 ~ 1.20, heated to 80 ~ 90 ℃, constant temperature and volume control Ph value, the reaction was stirred for 4h, aged for several hours, the supernatant was concentrated to a WO3 content of about 50%, insoluble was filtered off, the supernatant concentration was continued, cooling and crystallization, to 80 ℃ drying system.

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Also commonly termed APT, it is the "mother salt" or fundamental intermediate for downstream manufacturing of most tungsten materials and is used in tungsten-bearing catalysts. APT is quoted on the LME where its price is used as the precursor for the tungsten market.Ammonium paratungstate is a white crystalline powder having a minimum WO3 content of 88.5%, it is traded in container loads and priced in USD/mtu WO3. Its composition is typically:

WO3  =88.5%

Mo  <0.002%

Others  <0.001%

Also commonly termed AMT. It is has higher water-solubility than APT which suits its predominant application in tungsten-bearing catalysts. It is also a white crystalline powder of up to 99.95% purity AMT.Two grades are used in the industry having WO3 contents of minimum 83% and 90%.AMT is generally priced in USD/mt of material based on its WO3 content.

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The hydrogen and tungsten content and the high solubility of ammonium metatungstate suggest that a saturated aqueous solution of this salt may make a good neutron-gamma shield for 252Cf. Comparative attenuation experiments with a saturated aqueous solution and pure water show that the ammonium metatungstate solution is a significantly better shielding material for gamma rays and slow neutrons, and is also better than water for fast neutrons. For 252Cf sources of less than 500 [mu]g, a shield consisting of a thick paste of ammonium metatungstate is recommended as a useful shielding material in place of a saturated solution to reduce the hazard in case of container leakage. A saturated solution of ammonium metatungstate is relatively clear and may be used as an absorber in windows of hot cells.

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The interaction of nickel hydroxocarbonate, ammonium paramolybdate, and ammonium metatungstate (Ni:Mo:W= 3: 1:1) is reported.Under mechanical activation conditions, nickel hydroxocarbonate particles undergo comminution and ammonium paramolybdate and ammonium metatungstate particles soften and aggregate.It is demonstrated by DTA,X-ray diffraction and IR spectroscopy that heat treatment of the mechanically activated mixture at400–450°C yields the salts NiMoO4 and NiWO4.Nickel Hydroxocarbonate, Ammonium Paramolybdate and Ammonium Metatungstate

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Ammonium metatungstate applied in the manufacture of various petrochemical catalysts, It's the basic raw material of W-base catalyzer used in oil refinery.  

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There are some several suggest for dart practice:

In nearly all settings, a shared set of darts is used, rather than every competitor having their own darts. So if you were to retrieve the darts you just threw, all you would then do is immediately hand them to the next player. With that in mind, it is simply quicker for the incoming shooter to remove the darts from the board, rather than the awkward process of the preceding shooter removing them, then (carefully) passing a handful of three sharpened steel darts to the next player.

The next player can view and verify the score of the preceding player. This eliminates the need for a scorekeeper to stand near the board.

Dart maintenance supplies (like a potato, for moistening the dart tips, or a sharpening stone) are often kept at the board. Thus requiring every player to go the board before they throw rather than after, allowing him or her prepare quickly in the darts practical.

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The thin wires separating the scoring sections on the board occasionally overlap slightly, due to the manufacturing process. Any dart splitting the wires (landing in the tiny area where two wires overlap) is credited in the shooter's favor. For example, if the dart splits the wires separating the two and three point zones, the player is awarded three points. If the dart splits the wires separating the three point zone and the blue ring, the player is credited with three points.

Since the shafts of the darts are made from wood, and the tips are sharpened metal, it is possible for a dart to stick into the shaft of a previously thrown dart. The scoring of any dart is determined by where the tip of the dart lands, and since the tip of this dart is not in the board, the dart that is stuck in the barrel of another scores no points at all. It is considered the same as if it missed the board.

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The key rule of Strikeout is that the first dart to land in the 20-number scoring area sets that shooter's "number" for the remainder of the inning. Once that number is set, that number is the only number that can be scored for the remainder of the inning (with the exception of the center cork, which is always in play, regardless of the set "number"); the other nineteen numbers on the board are worth zero points for the remainder of the shooter's inning. So if a player throws his or her first dart at 20, in order to score the maximum possible points, but he or she misses and it lands in the 1 area, that player has established 1 as their number for darts #2 and #3. Thus, even if the last two darts were to land in 20, they would be scored as zero. Once a player establishes a poor number, the best strategy for the remainder of the inning is to just shoot at the 100-point cork, since even three darts in triple 1 would score only nine points. If the first dart does not land in one of the 20 scoring numbers (either misses the board completely, or hits the 100-point cork), the "number" is not yet established for that inning, and the shooter is still free to score in any of the 20 numbers on the second dart (likewise for dart #3, if both darts #1 and #2 do not land in any of the 20 numbers).

Since the first dart sets the number, players will sometimes shun shooting at the 20, since a small miss will result in either a 1 or a 5 being set as the number. Often two adjacent numbers with solid values, such as 11/14 and 10/15 are chosen by lower-skilled players, since a small miss there does not result is such a large penalty (if you miss the 14 you'll still land in the 11, etc.).

The maximum score in an inning is 300 points (3 corks). The maximum score for a team (two players) is 600 points. Corks and scoring numbers can be combined; for instance, if a player shoots a double 20, a cork, and a single 20, that player would score 160 points (40 + 100 + 20). If a player shoots a single 20, a double 5, and a single 20, that player would score 40 points (20 + 0 + 20), since the dart in the 5 would not count (20 having been established as the "number" for that inning).

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