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Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery, cutting tools, abrasives, armor-piercing rounds, other tools and instruments, and jewelry.
Tungsten carbide is approximately two times stiffer than steel, with a Young's modulus of approximately 530–700 GPa (77,000 to 102,000 ksi), and is double the density of steel-- nearly midway between that of lead and gold. It is comparable with corundum (α-Al2O3) in hardness and can only be polished and finished with abrasives of superior hardness such as cubic boron nitride and diamond powder, wheels, and compounds.
A method is disclosed for producing ammonium paratungstate from cemented tungsten carbide which comprises subjecting the cemented tungsten carbide to electrolysis by passing about 0.5 to about 20 volts through an ammoniacal solution selected from the group consisting of ammonium hydroxide-ammonium chloride solution, ammonium hydroxide-ammonium carbonate solution, and ammonium hydroxide-ammonium sulfate solution, wherein platinum and the cemented tungsten carbide serve as the anode and wherein the anode is immersed in the solution, to decompose the cemented tungsten carbide and form a solution of ammonium tungstate from which is crystallized ammonium paratungstate.
A process is disclosed for producing ammonium paratungstate which involves adding hexamethylenetetramine to a first solution of ammonium tungstate, adjusting the pH to about 2 with an acid to form a precipitate which contains the major portion of the tungsten and the hexamethylenetetramine and separating the precipitate from the resulting mother liquor. The tungsten hexamethylenetetramine precipitate is then dissolved in aqueous ammonia to form a second ammonium tungstate solution which is then heated at from about 90℃ to about 100℃ to form a precipitate essentially all of which is ammonium paratungstate and a mother liquor which contains essentially all of the hexamethylenetetramine. The ammonium paratungstate precipitate is then separated from the mother liquor.