Zinc tungstate

Zinc Tungstates.—The anhydrous normal salt, Z11WO4, is obtained as rhombic crystals by fusing together sodium tungstate (1 part), sodium chloride (2 parts), and zinc chloride (2 parts). The monc-hjdrate, ZnW04.H20, is obtained by double decomposition as a white amorphous precipitate, slightly soluble in water. ... 

Zinc and calcium siUcates, and calcium tungstate doped with activators such an Mn, Pb, Sn, and Eu are just a few examples of a large number of known ionicaHy bonded luminescent pigments. HaUde phosphates of the general formula 3Ca(P0 2 CaX2, where X = F or Cl, and Sb " and are... 

H. 8-Hydroxyquinaldine (XI). The reactions of 8-hydroxyquinaldine are, in general, similar to 8-hydroxyquinoline described under (C) above, but unlike the latter it does not produce an insoluble complex with aluminium. In acetic acid-acetate solution precipitates are formed with bismuth, cadmium, copper, iron(II) and iron(III), chromium, manganese, nickel, silver, zinc, titanium (Ti02 + ), molybdate, tungstate, and vanadate. The same ions are precipitated in ammoniacal solution with the exception of molybdate, tungstate, and vanadate, but with the addition of lead, calcium, strontium, and magnesium aluminium is not precipitated, but tartrate must be added to prevent the separation of aluminium hydroxide. 

Determination of tungsten as the trioxide (tannic acid-phenazone method) Discussion. Tungstic acid is incompletely precipitated from solutions of tungstates by tannic acid. If, however, phenazone (2,3-dimethyl-l-phenyl-5-pyrazolone) is added to the cold solution after treatment with excess of tannic acid, precipitation is quantitative. This process effects a separation from aluminium, and also from iron, chromium, manganese, zinc, cobalt, and nickel if a double precipitation is used. 

Sodium tungstate 699 Sodium zinc uranyl acetate 467 Sol 419... 

All commercial materials are based on calcium hydroxide and liquid alkyl salicylates (Prosser, Grolfman Wilson, 1982) and are supplied as a two-paste pack. Zinc oxide is sometimes added to the calcium hydroxide, as are neutral fillers. A paste is formed from this powder by the addition of a plasticizer examples include A-ethyl toluenesulphonamide (o- orp-) and paraffin oil, with sometimes minor additions of polypropylene glycol. The other paste is based on an alkyl salicylate as the active constituent containing an inorganic filler such as titanium dioxide, calcium sulphate, calcium tungstate or barium sulphate. Alkyl salicylates used include methyl salicylate, isobutyl salicylate, and 1-methyl trimethylene disalicylate. An example of one commercial material, Dycal, is given in Table 9.7, but its composition has been subjected to change over the years. 

Anhydrous sodium tungstate, 25 382 Anhydrous stannic chloride, 24 803 Anhydrous stannous chloride, 24 802-803 Anhydrous zinc chloride, 26 617 Anhydrous zinc sulfate, 26 617 Aniline, 2 783-809, 17 250, 259 alkylation, 2 197 Bechamp process, 2 490 from benzene, 3 619t, 620 chemical reactions, 2 783-789 derivatives, 2 783-809 economic aspects, 2 790-791... 

Reduction of MoIybdenum(VI) and Tungsten VI) Compounds. Pour 3 ml of an ammonium molybdate solution into each of four test tubes, acidify with a 2 N hydrochloric acid solution, and heat up to boiling. Add solutions of sulphuric acid, hydrogen sulphide, and tin(Il) chloride to three of the tubes, respectively, and throw one or two small pieces of zinc into the last tube. Perform similar experiments using sodium tungstate as the initial reactant. Write the equations of the reactions. 

Although flotation was developed as a separation process for mineral processing and applies lo the sulfides of copper, lead, zinc, iron-molybdenum, cobalt, nickel, and arsenic and to nonsullides, such as phosphates, sodium chloride, potassium chloride, iron oxides, limestone, feldspar, fluorite, chromite, tungstates, silica, coal, and rhodochrosilc, flotation also applies to nonmineral separations. Flotation is used in the water disposal field, particularly in connection with petroleum waste water cleanup. 

Fig. 12.49. Action of corrosion inhibitors, (a) Anodic inhibitors. Examples Chromate, nitrite, molybdate, tungstate, orthophosphate, silicate, benzoate, (b) Cathodic inhibitors. Examples Ca(HC03)2, ZnS04, Cr2(S04)3, NiS04 phosphate, aminoethylene phosphate (AMP), Ag3+, Sb3+ (on iron) Hg (on zinc), (c) Mixed inhibitors. Examples organic inhibitors containing nitrogen and/or sulfur (e.g., amines, triazoles, thiazoles, alkylthioureas) inorganic inhibitors (e.g., arsenite, arsenate, selenate). (Reprinted from G. Ranglen, Corrosion of Metals, p. 165,1985 with permission from Chapman Hall.)...

Lead-based inhibitors and zinc phosphate inhibitors are thought to plug up the discontinuities in the natural oxide layer and hence offer protection. This is akin to the repair of an imperfect oxide film of iron by chromates, molybdates or tungstates. 

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