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<h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Alliage de Devarda</span></h1>
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<div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="fr" dir="ltr"><div class="mw-content-ltr mw-parser-output" lang="fr" dir="ltr"><p>L’<b>alliage de Devarda</b> (<a href="Num%C3%A9ro_CAS" title="Numéro CAS">numéro CAS</a> <span class="reflink neverexpand"><span class="noarchive"><a class="external text" href="https://tools.wmflabs.org/magnustools/cas.php?cas=8049-11-4&amp;language=fr&amp;title=Alliage_de_Devarda">8049-11-4</a></span></span>), nommé d’après le <a href="Chimiste" title="Chimiste">chimiste</a> <a href="Italie" title="Italie">italien</a> Arturo Devarda&nbsp;<a href="https://it.wikipedia.org/wiki/Arturo_De_Varda" class="extiw external" title="it:Arturo De Varda"><span class="indicateur-langue" title="Article en italien&nbsp;: «&nbsp;Arturo De Varda&nbsp;»">(it)</span></a> (1859-1944), est un <a href="Alliage" title="Alliage">alliage</a> d’<a href="Aluminium" title="Aluminium">aluminium</a> (44 - 46&nbsp;%), de <a href="Cuivre" title="Cuivre">cuivre</a> (49 - 51&nbsp;%) et de <a href="Zinc" title="Zinc">zinc</a> (4 - 6&nbsp;%).
</p><p>Sous forme de poudre, il est utilisé comme agent <a href="R%C3%A9action_d'oxydo-r%C3%A9duction" class="mw-redirect" title="Réaction d'oxydo-réduction">réducteur</a> en <a href="Chimie_analytique" title="Chimie analytique">chimie analytique</a>, en particulier pour la détermination de la quantité d'<a href="Azote" title="Azote">azote</a> dans des <a href="Nitrite" title="Nitrite">nitrites</a> et des <a href="Nitrate" title="Nitrate">nitrates</a>.
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<div class="mw-heading mw-heading2"><h2 id="Réaction_avec_les_nitrates"><span id="R.C3.A9action_avec_les_nitrates"></span>Réaction avec les nitrates</h2></div>
<p>En présence d’alliage Devarda, la réduction des <a href="Ion" title="Ion">ions</a> nitrate dans une solution aqueuse d’<a href="Hydroxyde_de_sodium" title="Hydroxyde de sodium">hydroxyde de sodium</a> peut être écrite sous la forme ionique&nbsp;:
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<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathrm {3\ NO_{3}^{-}+8\ Al+5\ OH^{-}+18\ H_{2}O\rightarrow 3\ NH_{3}+8\ [Al(OH)_{4}]^{-}} }">
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<annotation encoding="application/x-tex">{\displaystyle \mathrm {3\ NO_{3}^{-}+8\ Al+5\ OH^{-}+18\ H_{2}O\rightarrow 3\ NH_{3}+8\ [Al(OH)_{4}]^{-}} }</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/07a57477f92ee96dc27943eda034b7bdbc2392f4.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:59.866ex; height:3.176ex;" alt="{\displaystyle \mathrm {3\ NO_{3}^{-}+8\ Al+5\ OH^{-}+18\ H_{2}O\rightarrow 3\ NH_{3}+8\ [Al(OH)_{4}]^{-}} }" loading="lazy"></span>.</dd></dl>
<p>Le gaz <a href="Ammoniac" title="Ammoniac">ammoniac</a> libéré est converti en <a href="Ammoniaque" title="Ammoniaque">ammoniaque</a>, ce qui permet le dosage de l’azote total par la <a href="M%C3%A9thode_de_Kjeldahl" title="Méthode de Kjeldahl">méthode de Kjeldahl</a>.
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<div class="mw-heading mw-heading2"><h2 id="Liens_externes">Liens externes</h2></div>
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<li><div class="liste-horizontale"><span class="wd_identifiers">Notice dans un dictionnaire ou une encyclopédie généraliste</span>&nbsp;: <ul><li><a rel="nofollow" class="external text" href="https://denstoredanske.lex.dk//Devardas_legering/"><i>Den Store Danske Encyklopædi</i></a></li> </ul></div></li>
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