Abstract: To obtain highly purified, lamp grade ammonium paratungstate crystals from any of several different tungsten ores, the ore is reduced to finely divided status and slurried in heated HCl solution to convert tungsten values to WO.sub.3.H.sub.2 O. Recovered tungstic oxide is washed and dissolved in heated aqueous solution of sodium carbonate or sodium hydroxide with the pH maintained at about 8 to 8.5 to form soluble sodium tungstate. Sodium hydroxide is added to raise the pH to about 10.5 to 11.5, and magnesium chloride is added in amount sufficient to somewhat neutralize the solution. Sodium hydroxide is added to raise the pH to about 10.5 to 11.5 to precipitate as hydroxide the magnesium and additional metallic impurities. At least one of ammonium sulfide and thioacetamide is and the heated solution is acidified to a pH in the range from about 2 to 3 to precipitate any molybdenum as MoS.sub.3.

Abstract: The quality and useful life of regenerative-cycle type incandescent lamps that employ iodine as the halogen are enhanced by dosing the lamps with controlled amounts of SnI.sub.4 in combination with elemental iodine. Alternative dual-additives that provide iodine-bromine type lamps are SnI.sub.4 in combination with a compound such as methylene bromide (CH.sub.2 Br.sub.2) or mercury bromide which decompose within the energized lamp and release free bromine, and mercury iodide in combination with CH.sub.2 Br.sub.2. The combined use of two different additives or dosing materials to provide either an iodine or an iodine-bromine atmosphere within the operating lamp permits elongated tubular lamps having singly-coiled filaments to be operated in various non-horizontal burning positions at voltages above their nominal voltage ratings for much longer periods of time than lamps of the same rating and construction that are dosed with a single additive such as elemental iodine, SnI.sub.4 or CH.sub.2 Br.sub.2.

Abstract: The quality and useful life of regenerative-cycle type incandescent lamps that employ iodine as the halogen are enhanced by dosing the lamps with a carefully controlled amount of SnI.sub.4 which decomposes when the lamp filament is energized and provides from about 0.05 to 0.20 micromole of vaporized elemental iodine per ml. of bulb volume within the lamp during operation. The resulting increase in the amount of iodine that is converted into atomic rather than molecular form within the energized lamp permits elongated iodine-cycle lamps having singly-coiled filaments to be operated in any position in contrast to conventional iodine-cycle lamps of the same configuration and construction that exhibit early blackening of the top portion of the envelope when the lamp is operated in a vertical position. The undesirable light-absorption and color distortion effects characteristic of conventional iodine-dosed lamps are also reduced, thus increasing the lamp efficiency.

Abstract: The useful life of high-efficiency type bromine-tungsten cycle incandescent lamps, such as those used in TV-studio and theater lighting applications, is enhanced by dosing the lamps with a carefully controlled quantity of mercuric bromide (HgBr.sub.2) which dissociates when the filament of the finished lamp is energized and provides a predetermined amount of Br.sub.2 within the envelope during lamp operation. The quantity of HgBr.sub.2 dosed into the envelope is adjusted according to the design life and initial efficiency parameters of the specific lamp type so as to provide a concentration of Br.sub.2 within the envelope which is correlated with such parameters and prevents blackening of the envelope and premature failure of the filament at the particular "life-efficiency level" of operation for which the lamp is designed. For a 1000 watt 120 volt tubular incandescent lamp (DXW type) having a design life of 150 hours and an efficiency of 28 LPW, the HgBr.sub.2 dosage is such that it provides from about 2.

Abstract: Dissolved molybdenum is recovered from spent sulfuric acid-nitric acid solution by adding ammonium hydroxide to spent acid solution to raise pH thereof to from about 1.5 to about 3, and preferably from 2 to 3. Solution is then agitated and simultaneously heated at a temperature less than about 95.degree.C until substantially all dissolved molybdenum is precipitated as ammonium molybdate complex, from which the precipitate is then recovered.