Saltpeter
<p >Iodine was discovered by <a href="http://en.wikipedia.org/wiki/Bernard_Courtois" title="Bernard Courtois" >Bernard Courtois</a> in 1811.<sup id="cite_ref-court_13-0" class="reference" ><a href="http://en.wikipedia.org/wiki/Iodine#cite_note-court-13" >[14]</a></sup><sup id="cite_ref-14" class="reference" ><a href="http://en.wikipedia.org/wiki/Iodine#cite_note-14" >[15]</a></sup> He was born to a manufacturer of <a href="http://en.wikipedia.org/wiki/Potassium_nitrate" title="Potassium nitrate" >saltpeter</a> (a vital part of <a href="http://en.wikipedia.org/wiki/Gunpowder" title="Gunpowder" >gunpowder</a>). At the time of the <a href="http://en.wikipedia.org/wiki/Napoleonic_Wars" title="Napoleonic Wars" >Napoleonic Wars</a>, <a href="http://en.wikipedia.org/wiki/France" title="France" >France</a> was at war and saltpeter was in great demand. </p>
<p>
Saltpeter produced from French <a href="http://en.wikipedia.org/wiki/Niter" title="Niter" >niter</a> beds required <a href="http://en.wikipedia.org/wiki/Sodium_carbonate" title="Sodium carbonate" >sodium carbonate</a>, which could be isolated from <a href="http://en.wikipedia.org/wiki/Seaweed" title="Seaweed" >seaweed</a> collected on the coasts of <a href="http://en.wikipedia.org/wiki/Normandy" title="Normandy" >Normandy</a> and <a href="http://en.wikipedia.org/wiki/Brittany" title="Brittany" >Brittany</a>. To isolate the sodium carbonate, seaweed was burned and the ash washed with water. The remaining waste was destroyed by adding <a href="http://en.wikipedia.org/wiki/Sulfuric_acid" title="Sulfuric acid" >sulfuric acid</a>. Courtois once added excessive sulfuric acid and a cloud of purple vapor rose. He noted that the vapor crystallized on cold surfaces, making dark crystals. Courtois suspected that this was a new element but lacked funding to pursue it further.</p>