Abstract: A platewarmer system comprises a platewarmer and platewarmer lid. The platewarmer has a base, a heat storage member supported on the base, and a retainer covering the heat storage member and fixed to the base whereby the heat storage member is fixed to the base. The platewarmer lid has a body and an insert fixed to the underside of the body for reflecting heat radiated from the surface over which the lid is placed. The method of manufacturing the platewarmer includes forming a heat storage member, forming a retainer, and molding a plastic base wherein the heat sotrage member and retainer are encapsulated in the base as a unit. The method of manufacturing the platewarmer lid includes forming an insert and molding a plastic base wherein the insert is encapsulated inside the base.

Abstract: Dissolved molybdenum is removed from sodium tungstate solutions by adding sulfuric acid to lower the pH value of the solution to between about 8 and about 5, adding to the sodium tungstate solution a water-soluble sulfide in an amount of at least 0.5 gram per liter (gpl) in excess of that required to precipitate as sulfides molybdenum and certain other metals, then lowering the pH value of the sodium tungstate solution to between about 4.0 and about 1.5 as rapidly as possible with sulfuric acid in such a way as to precipitate molybdenum trisulfide while minimizing co-precipitation of tungsten.

Abstract: A process for producing a high purity ammonium heptamolybdate and/or ammonium dimolybdate product by which a particulated molybdenum oxide concentrate is purified to remove contaminating metal cations, whereafter it is leached with an ammoniacal leach solution to extract the molybdenum trioxide constituent therein as soluble ammonium molybdate compounds. The resultant ammoniacal leach solution is thereafter concentrated at an elevated temperature, whereafter at least a portion thereof is adjusted to provide an ammonia-to-molybdenum trioxide mol ratio ranging from about 0.86:1 to about 1.25:1, and the adjusted solution thereafter is cooled to effect a precipitation of ammonium heptamolybdate crystals which are separated and recovered, and the balance of the cooled solution is recirculated for admixture with additional ammoniacal leach solution.

Abstract: A simple, efficient and economical process for purifying molybdenum disulfide concentrates by contacting and digesting the molybdenum disulfide feed material with an aqueous acid solution containing a controlled combination of hydrofluoric acid and sulfuric acid in a manner to convert substantially all of the contaminating silica bearing minerals therein to aqueous soluble fluoride and sulfate compounds and any contaminating lead sulfide compounds to lead sulfate compounds, and thereafter washing, neutralizing and drying the purified molybdenum disulfide powder product. In accordance with a preferred practice, when the molybdenum disulfide feed material contains in excess of about 0.1% iron as an indication of pyrite concentration, the concentrate is calcined at an elevated temperature in a nonoxidizing atmosphere prior to the digestion step to effect a conversion of the pyrites to synthetic pyrrhotites, which are softer and less abrasive and are more acid soluble.

Abstract: A process for purifying concentrates of molybdenum oxide containing a variety of naturally-occurring contaminating metals, such as potassium, copper, calcium, magnesium, iron, aluminum, lead, zinc, bismuth, and the like, as well as compounds thereof, by roasting the impure concentrate at an elevated temperature in an oxygen atmosphere to convert sub-oxides of molybdenum to molybdenum trioxide and contaminating metal molybdites to corresponding metal molybdates, which are extracted by a hot aqueous leaching of the concentrate and the solubilized molybdate ions are recovered. The aqueous leached concentrate, after separation from the aqueous leach solution, is leached with an ammoniacal leach solution for converting the molybdenum trioxide constituent therein into soluble ammonium molybdate compounds, and the resultant leach solution is removed from the remaining insoluble residue, which is discarded.