Potassium tetraiodomercurate(II)

<h2 id="preparation">Preparation</h2>
<p>The compound crystallizes from a heated solution of <a href="/facts/Mercuric_iodide/3T73Agxs">mercuric iodide</a>, <a href="/facts/Potassium_iodide/6023uFnx">potassium iodide</a>, and precisely 2% <a href="/facts/Water/0lkXnJPK">water</a> in <a href="/facts/Acetone/cVyJxKqw">acetone</a>.  Attempted synthesis in concentrated <a href="/facts/Aqueous_solution/eRNr3MH2">aqueous solution</a> will give the pale orange <a href="/facts/Water_of_crystallization/sbaKJNJX">monohydrate</a> K[Hg(H2O)I3] instead.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>  
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<h2 id="applications">Applications</h2>
<p>K2[HgI4] is a precursor to analogous <a href="/facts/Copper/I8PEE8oX">copper</a> and <a href="/facts/Silver/xXe41BGg">silver</a> salts M2[HgI4] (M=Cu, Ag).<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a>
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<h3>Nessler's reagent</h3>
<p>Nessler's reagent, named after <a href="/facts/Julius_Ne%C3%9Fler/TzemtAeI">Julius Neßler</a> (Nessler), is a 0.09 mol/L solution of potassium tetraiodomercurate(II) in 2.5 mol/L <a href="/facts/Potassium_hydroxide/NBhPBuXc">potassium hydroxide</a>. This pale solution becomes deeper yellow in the presence of <a href="/facts/Ammonia/MtLtJFtz">ammonia</a> (NH3). At higher concentrations, a brown <a href="/facts/Precipitate/s3BgsLLY">precipitate</a> derivative of <a href="/facts/Millon%27s_base/XdWJ1EDs">Millon's base</a> (HgO·Hg(NH2)Cl) may form. The sensitivity as a <a href="/facts/Spot_test/3jQIXhak">spot test</a> is about 0.3 μg <a href="/facts/Ammonia/MtLtJFtz">NH3</a> in 2 μL.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>
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NH+4 + 2 [HgI4]2− + 4 OH− → HgO·Hg(NH2)I↓ + 7 I− + 3 H2O
<p>The brown precipitate is not fully characterized and may vary from HgO·Hg(NH2)I to 3HgO·Hg(NH3)2I2.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a>
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<h2 id="external-links">External links</h2>
<ul><li><a href="https://web.archive.org/web/20051015082344/http://www-cie.iarc.fr/htdocs/monographs/vol58/mono58-3.htm">IARC Monograph: "Mercury and Mercury Compounds"</a></li>
<li><a href="https://web.archive.org/web/20060425193836/http://www.npi.gov.au/database/substance-info/profiles/53.html">National Pollutant Inventory - Mercury and compounds fact sheet</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Vogel, Arthur I.; Svehla, G. (1979), Vogel's Textbook of Macro and Semimicro Qualitative Inorganic Analysis (5th ed.), London: Longman, ISBN 0-582-44367-9 – via the Internet Archive <a href="0-582-44367-9" target="_blank">0-582-44367-9</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Wagenknecht, F.; Juza, R. (1963). "Potassium Triiodomercurate(II)". In Brauer, G. (ed.). Handbook of Preparative Inorganic Chemistry. Vol. 1 (2nd ed.). Academic Press. p. 1100 – via the Internet Archive. <a href="https://archive.org/details/Handbook_of_Preparative_Inorganic_Chemistry_1_2_Brauer/page/n1155/" target="_blank">https://archive.org/details/Handbook_of_Preparative_Inorganic_Chemistry_1_2_Brauer/page/n1155/</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Wagenknecht, F.; Juza, R. (1963). "Copper(I) Tetraiodomercurate(II)". In Brauer, G. (ed.). Handbook of Preparative Inorganic Chemistry. Vol. 1 (2nd ed.). Academic Press. p. 1100 – via the Internet Archive. <a href="https://archive.org/details/Handbook_of_Preparative_Inorganic_Chemistry_1_2_Brauer/page/n1155/" target="_blank">https://archive.org/details/Handbook_of_Preparative_Inorganic_Chemistry_1_2_Brauer/page/n1155/</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Vogel, Arthur I. (1954), A Textbook of Macro and Semimicro Qualitative Inorganic Analysis (4th ed.), London: Longman, p. 319, ISBN 0-582-44367-9 <a href="0-582-44367-9" target="_blank">0-582-44367-9</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>Vogel, Arthur I.; Svehla, G. (1979), Vogel's Textbook of Macro and Semimicro Qualitative Inorganic Analysis (5th ed.), London: Longman, pp. 293–294, ISBN 0-582-44367-9 – via the Internet Archive <a href="0-582-44367-9" target="_blank">0-582-44367-9</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
</ol>

Potassium tetraiodomercurate(II) open-in-new

Potassium tetraiodomercurate(II)