Dartboard is divided into different areas. Each region has a corresponding value, the magnetic dartboard can be carried out at any time is an all ages event . if darts landed on red and green color of the outer ring, then the score is twice the corresponding areas score. The dartboard includes a target board, a holding pole and two closure members. The target board includes a magnetic rubber sheet having a rectangular shape and containing iron, the two sheets of cotton flannel being attached to both surfaces of the magnetic rubber sheet and having raisings on their outer surfaces, and an upper fitted piece attached to the upper end of the front surface of one of said two sheets of flannel.

Each region has a corresponding value, if darts landed on red and green color of the outer ring, then the score is twice the corresponding areas score. For example, the double-digit area if the dart falls below 18, then the score is 36. Understand the inner red and green color score. If the magnetic landed on the red-green color of the inner ring, the score is the score three times the corresponding area. For example, if three times the area of magnetic dartboard falls under 18, then the score is 54. Learn dartboard central "bull's-eye" score. "Bull's-eye" is divided into two areas, inner (usually red) is called "double bull's-eye", the outer ring (usually green) called "single bull's-eye." The rest of the region on the dartboard is divided into 20 zones, each also has a specific value. The most common situation is black or yellow magnetic dartboard landed area, when the score is the number that corresponds to the region.

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Since the solubility of ammonium paratungstate increases rapidly at the high pH necessary to avoid molybdenum contamination, when very small molybdenum levels are desired, it may be desirable to leave some tungsten in solution, filter out the initial ammonium paratungstate precipitate, and recycle the filtrate. For example, if the precipitation is performed at a pH slightly above 8.5, 85 percent to percent of the tungsten will be precipitated as pure ammonium paratungstate. Further precipitation of tungsten may be obtained by boiling the filtrate in an open vessel. During this evaporation step ammonia and water are removed and the pH of the filtrate drops progressively to approximately 7.0. The molybdenum'content of the ammonium paratungstatethat is precipitated between the'pl-l values of 8.5 and 7.0'will rise from approximately 0.02 percentv t percent. This secondary precipitate will contain as high as 13 percent of the initial molybdenum. This material may then be recycled to a new batch of concentrated digester solution where it will raise the tungsten concentration. The filtrate resulting from this secondary precipitation step will contain approximately 2 percent or the initial tungsten and 92 percent of the initial molybdenum. If molybdenum is a desired byproduct, it may be obtained by any of a number f methods from this resulting filtrate.

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Ammonium paratungstate is a very desirable form of tungsten for many industrial applications. Much effort has been expended by industry in order to arrive at economical methods of producin this product. Tungsten is derived primarily ll'QIl'l scheelite ore which is substantially calcium tungstate. This is normally treated by dissolution under pressure in a sodium carbonate solution. In this manner an aqueous solution of sodium tungstate is formed which may be used as a starting point for the preparation of ammonium paratungstate. it will be obvious that this sodium paratungstate solution contains not only tungsten values but also impurities such as sodium carbonate, sodium molybdate, silica, sodium fluoride, phosphorous, and molybdenum. Of these contaminants, molybdenum is one of the most difficult to control. At the present time a complex multi-step process is needed for producing ammonium paratungstate from such industrial solutions while substantially avoiding serious contermination of the product. A large number of pH changes are required which entail th use of large quantities of various acids and alkali Even with this complex procedure, however, impurities are almost always present in the final product.

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Ammonium Paratungstate (NH₄)[H₂W₁₂O₄₂].4H₂O is the most important precursor for the majority of tungsten products. Exceptions are products of melting metallurgy and Menstrum WC produced directly from ore concentrates.

All other intermediates such as tungsten trioxide, tungsten blue oxide, tungstic acid and ammonium metatungstate can be derived from APT, either by thermal decomposition or chemical conversion.APT is a white crystallized powder having average crystal size between 30 and 100 µm. Especially crucial for the quality is the purity. Typical levels of todays commercial APT are (upper limits in µg/g):Al 1-7, As 5-10, Bi 0.5-1, Ca 1-10, Co 1-10, Cr 1-10, Cu 1-3, Fe 3-10, K 2-10, Mg 1-7, Mn 1-10, Mo 5-30, Na 5-10, Ni 1-7, P 5-7, Pb 1-5, S 5-7, Si 1-10, Sn 1-10, Ti 3-10, and U 3-10. APT is packaged in polyethylene-lined drums or woven bags up to 1 ton.

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There are some advantages of dart game ,especially the aspect of psychological:

It can improve brain balance and coordination skills. Dart game can develop the mussel consistent with the physical and mental. Make the heart, eyes, hands, force coordination to the optimum point, it may enhance balance and coordination ability of the brain, brain activity slows brain full of fine bubbles decreased ability to work full-time.

Improve the psychological quality in the technical details of darts. It emphasize the movement, honed by a certain time, for them, it is a challengeto overcome the psychological process of self-tolerance and exercise, anti-jamming capability.

Build self-confidence, individuality.

Darts game advantages would easy to use compared to other sports easy progress and achievement, and better reflect the personality can develop their skills and
Establish a strong self-confidence, initiative, and a sense of achievement and satisfaction.

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When concentrating an ammoniacal solution of tungstic acid (i.e. hydrous WO3), the product obtained is ammonium paratungstate. Below 50 C, the hexahydrate is formed, whereas when the temperature of the solution is above 50 °C, the pentahydrate or heptahydrate is formed. The former crystallizes as triclinic plates or prisms, whereas the latter as pseudorhombic needles.If a calcined WO3 is used, refluxing the ammonia solution is advisable to speed up the dissolution of the oxide.

Ammonium paratungstate is a white, crystalline powder with a very high degree ofchemical purity. It is used as a universal intermediate product for a variety of applications such as manufacturing tungsten oxides and tungsten metal powder, tungstic acid, ammonium paratungstate and organometallic components as well as in catalysis and fine chemistry.

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In more recent literature, the anion in (NH4)10(W12O41)·5H2O has been shown to be [H2W12O42]10−, containing two hydrogen atoms, keeping two hydrogen atoms inside the cage. The tungsten-oxygen cage, that is the heart of the anion requires 42 oxygen molecules. The correct formula notation for ammonium paratungstate is (NH4)10[H2W12O42]·4H2O. The [H2W12O42]10−ion is known as the paratungstate ion, as opposed to the paratungstate ion, that has the formula [W7O24]6−, similar to the paramolybdate ion. The existence of the paratungstate A ion, could not be confirmed by NMR spectroscopy, however.

Before about 1930, there has been some dispute about the exact composition of the salt, and both (NH4)10W12O41 and (NH4)6W7O24 were proposed. O.W. Gibbs remarked about this:

The alkali tungstates are numerous and unusually complex. Salts of essentially different formulae approach so closely in percentage composition, that the differences lie very near the unavoidable errors of analyses. The analyses are hardly sufficiently close to decide the question upon purely analytical grounds.

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Ammonium paratungstate(APT) is a white crystalline salt of ammonium and tungsten, with the chemical formula (NH4)10(H2W12O42)•4H2O.
Ammonium paratungstate is produced separating tungsten from its ore. Once the ammonium paratungstate is prepared, it is heated to its decomposition temperature, 600 C. Left over is WO3,tungsten(VI) oxide. From there, the oxide is heated in an atmosphere of hydrogen, reducing the tungsten to elemental powder, leaving behind water vapor. From there, the tungsten powder can be fused into any number of things, from wire to bars to other shapes.

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There are some advantage of dart games:

1.Rising chest and abdomen, can relieve fatigue cervical, lumbar, shoulder, elbow, wrist and other parts. Relax the mind, relieve stress. In particular, the health of people engaged in office work best effects, it is a modern way for people, especially for old.

2. One of arts game is that it can rivet restore movement and contraction mainly involved muscles and joints, wrist, elbow, shoulder, deltoid, triceps, wrist, finger muscles, especially for people of few muscle training exercise, exercise is not also adjust.

3, Advantage of dart games:relieve visual fatigue
When throw darts, there be completed on the basis of long-range targeting in the firing action, and after a long period of training, we can take the goal, vision tends to increase muscle strength. It is also alleviate eye fatigue caused by prolonged close work, such as regulating vision of eyes.

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