Metal salts Molybdate

Chemical inhibitors, when added in small amounts, reduce corrosion by affecting cathodic and/or anodic processes. A wide variety of treatments may be used, including soluble hydroxides, chromates, phosphates, silicates, carbonates, zinc salts, molybdates, nitrates, and magnesium salts. The exact amount of inhibitor to be used, once again, depends on system parameters such as temperature, flow, water chemistry, and metal composition. For these reasons, experts in water treatment acknowledge that treatment should be fine tuned for a given system. 

Cyclization of 3,4,5,6-tetrachlorophthalic anhydride (8) in the presence of urea, Ihe appropriate metal salt and catalytic amounts of ammonium molybdate(VI) in nitrobenzene at high temperature leads to phthalocyanine 9. 

Mixed condensation of 4-sulfophthalic acid with other substituted phthalic acids (typically >200 °C, metal salt, urea, ammonium molybdate catalyst Figure 6) again gives mixtures.246-248 Routes which lead predominantly to monosulfonic acids of zinc(II) phthalocyanine and related compounds have been described.247,250... 

Decomposes on heating or on treatment with alkalies reacts with lead chloride and other metal salts to form their metal molybdates ... 

Molybdate, chromates, iodides, bromides, cerium(IV) ions and also large amounts of coloured metallic salts reduce the sensitivity of the reaction. 

Like all the other transition elements, molybdenum is a metal, and it is widely used as an alloying element and as a metallic coating. Some of its physical properties are listed in Table 3.2. In chemical reactions it shows little tendency to form cations, which is usuaily a characteristic of metals. In fact its sait-forming properties resembie those of non-metals, in that it has the ability to form salts (molybdates, sulphomolybdates, etc) or other complex compounds with another metal and a non-metal such as oxygen, sulphur or a halogen. The chemistry of molybdenum is very... 

The important chalcogenides are the disulphide, diselenide and ditelluride, and their use in lubrication is described later. Other selenides and tellurides have also been identified and studied to a limited extent, but as a class these materials tend not to be stoichiometric. One group of relatively simple compounds is that of the molybdates. These are salts of ammonia or metals with molybdic acid H2M0O4. 

Molybdates of the Rare Earth Metals. —Salts of the type M2(Mo04)3 have been described. The cerous salt is obtained as yellow crystals by fusing together anhydrous cerous chloride and sodium molybdate. The density of the molten salt is 4-56. The crystals are similar to those of lead and bismuth molybdates, as also are those of didymium molybdate. ... 

One of the simplest methods of preparation is by decomposition of a thermally unstable compound. The nitrate or chloride is often preferred, sulphates tend to decompose at higher temperatures. Where the presence of residual traces of anion is to be avoided, the metal salts of organic acids are particularly useful. Formates, oxalates, acetates etc, decompose at low temperatures and often reduce the metal at the same time. For the preparation of catalysts from anions, the ammonium salt is frequently used. Metallic salts of complex acids can be used as a source of metal oxide mixtures. Decomposition of the appropriate chromate, tungstate, molybdate or vanadate will produce the mixed oxide. 

Olefin oxidation with an aqueous palladium chloride solution according to eqs. (2)-(4) occurs stoichiometrically. A catalytic reaction is only possible if the metallic palladium can be reoxidized immediately. With gaseous oxygen, conditions to oxidize even finely divided palladium black are not optimal. However, metal salts such as cupric and ferric chlorides, chromates, heteropoly acids of phosphoric acid with molybdic and vanadic acids, or other oxidants - e. g., ben-zoquinone is used in kinetic investigations [10] - are suitable for reoxidation of the palladium metal. This fact explains the increase of the yield of acetaldehyde in the first experiments of the Consortium carried out in the presence of cupric and ferric chlorides, as mentioned above. 

A variety of metal salts, transfer agents, complexes and liquids were examined. Some gave higher yields and rates than others and acceptable yields. However, all of them suffered from either no activity, off-line catalyst preparation, tar formation, product contaminated with catalyst or a requirement for a co-solvent. Emulsion and tar formations were troublesome. This resulted in yield loss and contaminated product after difficult work-up procedures that would be unsatisfactory for large-scale production. The best overall result was obtained using sodium molybdate (5 mole%) and tris[2-(2-methoxyethoxy)ethyl]amine 3 (TDA-1, 5 mole %) at 60°C. The yield was >90% and the catalyst system could readily be removed by water washing. 

Benzyl phenyl sulphide, norbornene, cw-cyclooctene, and 4-vinyl-1-cyclohexene were obtained from Aldrich and (IS)-(-)-a-pinene from Fluka. Phenyl sulphide was prepared from benzene and sulphur chloride following the literature procedure[9]. Reference samples of sulphoxides and sulphones were prepared by oxidation of sulphides with sodium periodate[10] and hydrogen peroxide[ll] respectively. Reference samples of epoxides were made by following Kaneda et al.[ 2 procedure. Metal phthalocyanines[13] were prepared from appropriate metal salt, 1,2-dicyanobenzene with ammonium molybdate as catalyst and were characterized by elemental analysis. 

The sensitivity of the mercury test with diphenylcarbazone depends on the acidity of the test solution, and decreases with increasing acidity. In neutreil or very weakly acid solutions, other heavy metals (Cu, Fe, Co and others) also give colored compounds with diphenylcarbazone. In 0.2 N nitric acid solution, the diphenylcarbazone reaction is specific for mercury, in the absence of chromates and molybdates (which give colored compounds under the same conditions, see page 188). The interference of chromates is prevented by reducing them, by means of sulfurous acid or hydrogen peroxide, to nonreacting chromic salts. Molybdates may be masked with oxalic acid, since the complex molybdenum-oxalic acid does not react with diphenylcarbazone. 

When testing for molybdenum in mixtures containing metal salts, it is best to boil the test material with sodium carbonate or to fuse it with potassium sodium carbonate, to form water-soluble alkali molybdate. If a mixture of acid-insoluble sulfides is being tested, the sulfur can be roasted off and the alkali molybdate then dissolved out by digesting with alkali hydroxide. 

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