Abstract: A method is disclosed for producing fine size molybdenum trioxide powder which involves heating ammonium dimolybdate in ambient atmosphere at a temperature of from about 455.degree. C. to about 465.degree. C. for a time of from about 5 hours to about 6 hours to produce a first molybdenum trioxide which is granulated to about -10 mesh and then heated in a furnace in which there are three heating zones. The first molybdenum trioxide is heated in the first heating zone at a temperature of from about 550.degree. C. to about 590.degree. C., in the second heating zone at a temperature of from about 580.degree. C. to about 610.degree. C. and thereafter in the third heating zone at a temperature of from about 580.degree. C. to about 625.degree. C., with the feed rate of material in the three zones being from about 1.5 to about 3.0 kg/hr to produce a yellow molybdenum trioxide. The yellow molybdenum trioxide is then cooled and granulated to about -40 mesh.

Abstract: A process is disclosed for purifying molybdenum containing arsenic and phosphorus which involves leaching molybdenum trioxide in an acid at a temperature of above about 70.degree. C.

Abstract: A process for purifying molybdenum, which comprises first leaching impure molybdenum trioxide containing potassium in a liquid medium of nitric acid, and an ammoniacal liquor, wherein the nitric acid concentration is about 3.5 to 4.0 moles per liter and the ammonium nitrate concentration is about 0.5 to 1.0 moles per liter, at greater than 50.degree. C. to solubilize the major portion of the potassium and produce a once-leached molybdenum trioxide and a first liquor, removing the once-leached molybdenum oxide from the first liquor, re-leaching the once-leached molybdenum trioxide in nitric acid having a concentration of about 3.5 to 4.0 moles per liter, at greater than 50.degree. C. to produce a twice-leached molybdenum trioxide and a second liquor, removing the twice-leached molybdenum oxide from the second liquor, water washing the twice-leached molybdenum trioxide, digesting the molybdenum trioxide in ammonium hydroxide at greater than 50.degree. C. at a pH of greater than 9.

Abstract: A method is disclosed for purifying ammonium dimolybdate which comprises dissolving ammonium dimolybdate containing arsenic as an impurity in water to form an ammonium molybdate solution and insolubles containing essentially all of the arsenic, filtering off the insolubles from the solution, adjusting the pH of the solution to at least about 9.0 and then crystallizing pure ammonium dimolybdate from the solution wherein the arsenic content is less than about 8 weight ppm.