Ammonium tetrathiotungstate, also known as ammonium thiotungstate and ammonium tetrathiot, it is a bright orange crystals with a metallic luster. The physical properties of ammonium tetrathiotungstate as follows: chemical formula: H8N2S4W, molecular weight: 348.18, density 2.71. Related System Number as follows: CAS registry number: 13862-78-7, MDL registry number: MFCD00061410, PubChem registry number: 24860418. Ammonium tetrathiotungstate has some harm to the environment, so during the operation can not be discharged it directly into lakes and rivers or sewer.
Making ammonium tungstate and tungstate to react to generate ammonium tetrathiotungstate and the producing process are as follows:
1. The ammonium tungstate by ammonia dissolved.
2.And then reaction with ammonium sulfide solution, the molar ratio S / W = 4-6：1, the reaction temperature: room temperature to 90 ℃, reaction time: 0.5 to 3 hours, static crystallization time: 8to24 hours.
3. Finally, the crystals were filtered, washed with water and washed with percutaneous ethanol, and finally dried to obtain ammonium tetrathiotungstate.

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Spherical calcium tungstate microcrystals were prepared with heat treatment at 100 ℃ and using a calcium tungstate muddy solution by precipitation with natrium tungstate and calcium nitrate as starting materials, and with cetyltrimethyl ammonium bromide as a surfactant. The spherical calcium tungstate microcrystals were characterized by X-ray diffraction and transmission elec-tron microscopy. The results indicate that the crystallites of the calcium tungstate samples are excellent, and the diameters of the calcium tungstate microcrystals with outstanding spherical morphology are 2.1-3.2 μm, and the particles are well dispersed and not aggregated. Cetyltrimethyl ammonium bromide plays an important role in the formation of spherical calcium tungstate microcrystals. When excited at 265 nm, the luminescence of calcium tungstate microcrystals exhibits a luminous peak in the blue band. The luminescent intensity of spherical calcium tungstate microcrystals is about two times greater than that of the aggregate particles.

 

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301
Number of Players: Any number of players may play, but normally two individuals or two teams play.
Numbers in Play: All the numbers are in play, but some receive greater use than others. The 19 and 20, for instance are used extensively for scoring points since they are the highest numbers on the tungsten dartboard. All the numbers may be used to throw the necessary doubles in the game.
This game is generally played by two people but can be played by teams. Each player starts with 301 points. The goal for each player is to reach zero, exactly, by subtracting the amount they score in a turn from the amount they had left from the previous turn. The player cannot start subtracting until they double in (hits one of the 21 doubles on the tungsten dartboard including the double bull). Once the double is hit, then all scores will count. To end the game, the player must also double out (ie. If they have 32 left, then they will need use tungsten dart to hit a double 16 to win. If they then hit a single sixteen, leaving 16, their next target would be a double 8. If they should hit more points than they have left, then they have busted. Their turn is over and they will resume with the same score they started with on that throw the next time it is their turn to throw.). If they hit the double leaving them zero points, then they have won the game.

501
Number of Players: Any number of players may play, but normally two individuals or two teams play.
Numbers in Play: All the numbers are in play, but some receive greater use than others. The 19 and 20, for instance are used extensively for scoring points since they are the highest number on the tungsten dartboard. All the numbers may be used to throw the necessary doubles in the game.
This game is generally played as a team event, though we also play it in our single events. All players/teams start with 501 points. Unlike 301, you do not have to double-in, but can start on any number. Each player/team subtracts the amount they score from the amount they have left. To win, like 301 above, the player/team will need to double-out to reach zero.

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Calcium tungstate nanocrystalline was successfully synthesised via a microwave irradiation method using Ca(NO₃)₂ and Na₂WO₄ in ethylene glycol, without the requirement of any calcination. The product was analysed by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and photoluminescence spectrometry. XRD, SAED and TEM revealed that the product was body-centred tetragonal CaWO₄ with an average particle size of 12 nm. Different oscillation modes were detected by Raman spectroscopy and FTIR. They showed the strong W–O stretching in [WO₄]²⁻ tetrahedrons at 711–933 cm⁻¹. Photoluminescence (PL) of CaWO₄ nanocrystalline showed the maximum emission peak at 422 nm.

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