Prussian Blue
<p ><b>Prussian blue</b> is a dark blue <a href="http://en.wikipedia.org/wiki/Pigment" title="Pigment" >pigment</a> with the idealized <a href="http://en.wikipedia.org/wiki/Chemical_formula" title="Chemical formula" >formula</a> <a href="http://en.wikipedia.org/wiki/Iron" title="Iron" >Fe</a><sub >7</sub>(<a href="http://en.wikipedia.org/wiki/Carbon" title="Carbon" >C</a><a href="http://en.wikipedia.org/wiki/Nitrogen" title="Nitrogen" >N</a>)<sub >18</sub>. Another name for the color <i>Prussian blue</i> is <i>Berlin blue</i> or, in <a href="http://en.wikipedia.org/wiki/Painting" title="Painting" >painting</a>, <i>Parisian blue</i>. <b>Turnbull's blue</b> is the same substance but is made from different <a href="http://en.wikipedia.org/wiki/Reagent" title="Reagent" >reagents</a>.
Prussian blue was one of the first synthetic pigments. It is employed as a very fine <a href="http://en.wikipedia.org/wiki/Colloidal_dispersion" title="Colloidal dispersion" class="mw-redirect" >colloidal dispersion</a>, as the compound itself is not soluble in water. It is famously complex,<sup id="cite_ref-Dunbar_0-0" class="reference" ><a href="http://en.wikipedia.org/wiki/Prussian_blue#cite_note-Dunbar-0" >[1]</a></sup> owing to the presence of variable amounts of other ions and the sensitive dependence of its appearance on the size of the colloidal particles formed when it is made. The pigment is used in <a href="http://en.wikipedia.org/wiki/Paint" title="Paint" >paints</a>, and it is the traditional "blue" in<a href="http://en.wikipedia.org/wiki/Blueprint" title="Blueprint" >blueprints</a>.
In medicine, Prussian blue is used as an <a href="http://en.wikipedia.org/wiki/Antidote" title="Antidote" >antidote</a> for certain kinds of <a href="http://en.wikipedia.org/wiki/Heavy_metal_poisoning" title="Heavy metal poisoning" class="mw-redirect" >heavy metal poisoning</a> (<a href="http://en.wikipedia.org/wiki/Caesium" title="Caesium" >caesium</a> and <a href="http://en.wikipedia.org/wiki/Thallium" title="Thallium" >thallium</a>).
Prussian blue lent its name to <a href="http://en.wikipedia.org/wiki/Prussic_acid" title="Prussic acid" class="mw-redirect" >prussic acid</a>, which was derived from it, and to <a href="http://en.wikipedia.org/wiki/Ferrocyanide" title="Ferrocyanide" >ferrocyanide</a> (originally meaning "blue compound of iron", from Latin <i>ferrum</i> and Greek κυανεος). As ferrocyanide is made of iron and CN <a href="http://en.wikipedia.org/wiki/Ligand" title="Ligand" >ligands</a>, reinterpreting the component "-cyanide" in the compound word, produced the word "<a href="http://en.wikipedia.org/wiki/Cyanide" title="Cyanide" >cyanide</a>" for compounds containing the CN radical.
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<h3 >Medicine</h3>
<p >Prussian blue's ability to incorporate monocations makes it useful as a sequestering agent for certain heavy metal poisons. Pharmaceutical-grade Prussian blue in particular is used for patients who have ingested <a href="http://en.wikipedia.org/wiki/Thallium" title="Thallium" >thallium</a> or <a href="http://en.wikipedia.org/wiki/Radioactive_decay" title="Radioactive decay" >radioactive</a> <a href="http://en.wikipedia.org/wiki/Caesium" title="Caesium" >caesium</a>. According to the <a href="http://en.wikipedia.org/wiki/International_Atomic_Energy_Agency" title="International Atomic Energy Agency" >International Atomic Energy Agency</a>, an adult male can eat at least 10 grams of Prussian blue per day without serious harm. The <a href="http://en.wikipedia.org/wiki/U.S._Food_and_Drug_Administration" title="U.S. Food and Drug Administration" class="mw-redirect" >U.S. Food and Drug Administration</a> (FDA) has determined that the "500 mg Prussian blue capsules, when manufactured under the conditions of an approved New Drug Application (NDA), can be found safe and effective therapy" in certain poisoning cases.<sup id="cite_ref-17" class="reference" ><a href="http://en.wikipedia.org/wiki/Prussian_blue#cite_note-17" >[18]</a></sup> Radiogardase (Prussian blue in soluble capsules <sup id="cite_ref-18" class="reference" ><a href="http://en.wikipedia.org/wiki/Prussian_blue#cite_note-18" >[19]</a></sup>) is a commercial product for the removal of <a href="http://en.wikipedia.org/wiki/Caesium-137" title="Caesium-137" >caesium-137</a> from the intestine and so indirectly from the bloodstream by intervening in the enterohepatic circulation of caesium-137,<sup id="cite_ref-19" class="reference" ><a href="http://en.wikipedia.org/wiki/Prussian_blue#cite_note-19" >[20]</a></sup> reducing the internal residency time (and exposure) by about two-thirds.</p>