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.

Tungsten Powder Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

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.

Tungsten Powder Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

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.

Tungsten Powder Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

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.

Tungsten Alloy Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-alloy.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn