Molybdates


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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Molybdates

 

salts of molybdic acids. Two types of molybdates are known: normal molybdates (salts of molybdic acid, H2MoO4) and polymolybdates (salts of isopolymolybdic acids). All normal molybdates, except the molybdates of alkali metals and magnesium, are poorly soluble in water. The most important soluble molybdate is Na2MoO4, which is used in the manufacture of dyes and varnishes; soluble molybdates are widely used as trace fertilizers.

Naturally occurring calcium, iron, and lead salts are among the most valuable poorly soluble molybdates. Calcium molybdates are also used to introduce molybdenum in the manufacture of alloy steels. Examples of isopolymolybdates include sodium di-, tri-, and tetra-molybdates, Na2Mo2O7, Na2Mo3O10, and Na2Mo4O13, respectively. Polymolybdates such as sodium paramolybdate, Na6Mo7O24 · xH2O, and ammonium paramolybdate, (NH4)6Mo7O24 · xH2O, have acquired wide practical significance. The latter is usually the final product in the processing of molybdenum concentrates and is widely used as a reagent.

A. N. ZELIKMAN

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
[34], the vibrational modes observed in Raman spectra of molybdates can be classified into two groups, internal and external modes.
The Raman spectrum can be separated into two parts with a wide empty gap in the range 500-700 [cm.sup.-1] that is commonly observed in molybdates containing Mo[O.sub.4] tetrahedra [22, 37-43].
The formation of compound can be attributed to the flame degradation of precursor, ammonium molybdate tetrahydrate, and entrapment of ammonia and water vapors inside the powders during particle formation.
Sahni, "Crystallization of mixed rare earth (didymium) molybdates in silica gel," Bulletin of Materials Science, vol.
By comparing the XRD pattern of the standard [gamma]-[Bi.sub.2]Mo[O.sub.6] sample (JCPDS PDF# 72-1524 or 71-2086), it can be realized that all of the Bragg diffraction peaks of each as-fabricated bismuth molybdate sample in the 20 range of 10-80[degrees] could be well indexed, as indicated in Figure 1 (S1-S4).
In this research, 0.03 mole of sodium molybdate ([Na.sub.2]Mo[O.sub.4]) and 0.06 mole of bismuth nitrate (Bi[(N[O.sub.3]).sub.3]) were dissolved in 600 mL deionized water.
Aqueous molybdenum, cobalt and platinum solutions were prepared from ammonium heptamolybdate (AHM, Merck), sodium molybdate dihydrate (SoMo, Merck), cobalt (II), nitrate hexahydrate (CoNi, Sigma), cobalt (II) chloride hexahydrate (CoCl, Aldrich), cobalt (II) acetate tetrahydrate (CoAc, Aldrich) and hexachloroplatinic acid (Sigma); deionized water (Milli Q quality, 18.2[mu][OMEGA]) was used in all cases.
(52), (53) In this experiment, it could be clearly appreciated and confirmed that the protective layer is a molybdate film that dissolved as corrosion continued over time (see Fig.
Szenicsite joins ferrimolybdite, lindgrenite, powellite and wulfenite as a simple molybdate.
Our doctoral research at the University has focused on the phosphates, arsenates, vanadates, molybdates and other secondary minerals in the oxidation zones of Pb-Zn-Fe-Cu orebodies in Extremadura; thus far we have studied and sampled over 40 such deposits, and have identified a sizeable number of mineral species, including many not previously reported from this area.
The third assay involves colorimetric determination of the liberated phosphate [9] based on the complex reaction between phosphate and molybdate in an acid environment.