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Ammonium heptamolybdate
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<h2 id="synthesis">Synthesis</h2> <p>Ammonium heptamolybdate is easily prepared by dissolving molybdenum trioxide in an excess of aqueous ammonia and evaporating the solution at room temperature. While the solution evaporates, the excess of ammonia escapes. This method results in the formation of six-sided transparent prisms of the tetrahydrate of ammonium heptamolybdate.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> </p><p>Solutions of ammonium paramolybdate react with acids to form <a href="/facts/Molybdic_acid/Wcl8KGqz">molybdic acid</a> and an <a href="/facts/Ammonium/jYm8wc1n">ammonium</a> salt. The pH value of a concentrated solution will lie between 5 and 6. </p> <h2 id="structure">Structure</h2> <p>The compound was first analyzed crystallographically by Lindqvist, but has been reanalyzed.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> All Mo centers are octahedral. Some oxide ligands are terminal, some doubly bridging, and a few are triply <a href="/facts/Bridging_ligand/E4ytba8I">bridging ligands</a>. </p> <h2 id="uses">Uses</h2> <ul><li>as an analytical <a href="/facts/Reagent/c3GLInCu">reagent</a> to measure the amount of <a href="/facts/Phosphate/FDGVCxUG">phosphates</a>, <a href="/facts/Silicates/7NdthSRM">silicates</a>, <a href="/facts/Arsenate/IWco5TAH">arsenates</a> and <a href="/facts/Lead/EYljasJN">lead</a> in <a href="/facts/Aqueous_solution/eRNr3MH2">aqueous solution</a> (e.g. pigments, river water, sea water etc.)<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a></li> <li>in the production of <a href="/facts/Molybdenum/RX6vp2bF">molybdenum</a> metal and <a href="/facts/Ceramic/9JKudpqX">ceramics</a></li> <li>in the preparation of dehydrogenation and <a href="/facts/Desulfurization/YLIGdUcX">desulfurization</a> <a href="/facts/Catalyst/LPBS7TQC">catalysts</a></li> <li>in the fixing of metals</li> <li>in <a href="/facts/Electroplating/HbKf0SBb">electroplating</a></li> <li>in fertilizers for crops.</li> <li>as a negative stain in biological electron microscopy, typically in the 3–5% (vol/vol) concentration range and in the presence of trehalose;<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> or at saturated concentration to perform cryo-negative staining.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a><a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a></li> <li>For the detection of recreational drugs as a component of the <a href="/facts/Froehde_reagent/Jfh19wPq">Froehde reagent</a></li></ul> <h2 id="related-compounds">Related compounds</h2> <p>Potassium heptamolybdate, also obtained as the tetrahydrate, is very similar to the ammonium salt.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p> <h2 id="safety">Safety</h2> <p>Molybdates are typically of low toxicity, so much so that few reports of incidents have ever been reported.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Sebenik, Roger F.; et al. (2000). "Molybdenum and Molybdenum Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007. ISBN 978-3-527-30673-2. <a href="978-3-527-30673-2" target="_blank">978-3-527-30673-2</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>L. Svanberg & H. Struve, J. pr. Ch. 44 [1848], p. 282; cited in Gmelin's Handbuch für Anorganische Chemie, 53, p. 255. <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Evans, H.T., Jr.; Gatehouse, B. M.; Leverett, P. "Crystal Structure of the Heptamolybdate(VI) (paramolybdate) ion, (Mo7O24)6−, in the ammonium and potassium tetrahydrate salts" Journal of the Chemical Society. Dalton Transactions, Inorganic Chemistry1975, p.505-p514. <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Parsons, T.; Maita, V. & Lalli, C. (1984). A manual of chemical and biological methods for seawater analysis. Oxford: Pergamon. <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Harris, J. R. and Horne, R. W. 1991. "Negative staining", in Harris J. R. (Ed.), Electron Microscopy in Biology, Oxford University Press, Oxford. <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Adrian, Marc; Dubochet, Jacques; Fuller, Stephen D.; Harris, J. Robin (1998). "Cryo-negative staining". Micron. 29 (2–3): 145–160. doi:10.1016/S0968-4328(97)00068-1. PMID 9684350. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>De Carlo, S.; El-Bez, C.; Alvarez-Rúa, C.; Borge, J.; Dubochet, J. (2002). "Cryo-negative staining reduces electron-beam sensitivity of vitrified biological particles". Journal of Structural Biology. 138 (3): 216–226. doi:10.1016/S1047-8477(02)00035-7. PMID 12217660. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Evans, H.T., Jr.; Gatehouse, B. M.; Leverett, P. "Crystal Structure of the Heptamolybdate(VI) (paramolybdate) ion, (Mo7O24)6−, in the ammonium and potassium tetrahydrate salts" Journal of the Chemical Society. Dalton Transactions, Inorganic Chemistry1975, p.505-p514. <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Sebenik, Roger F.; et al. (2000). "Molybdenum and Molybdenum Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007. ISBN 978-3-527-30673-2. <a href="978-3-527-30673-2" target="_blank">978-3-527-30673-2</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> </ol>