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~. ,. <br />CYANIDE DETOXIFICATION USING CYTOX CHEMICAL <br />FREE CYANIDE TREATMENT <br />1. The Chemical of Use <br />The chemical is a ferrous sulphate wherein part of the Fe is replaced by zinc. <br />Thus it has the generic formula: <br />(Zn.Fe) 504.7H20 <br />Zinc and iron can each be varied between 0 and 1 and the total of Fe and Zn will <br />be 1, for example: <br />(0.66 Zn.0.34Fe)SOy.7H20 <br />2. Mechanism of Reaction (How is CN "Killed") <br />The basis for the reaction (and the reason Zn is added) is the formation of the <br />ferro-cyanide complex <br />Fe (CN)8-e <br />This complex is highly stable, highly reactive and highly soluble in water. Its <br />stability over a wide range of pH is why it is used in humans as the antidote to <br />CN poisoning. <br />Its one oossible drawback is that under U.V. radiation it is believed to <br />breakdown releasing free CN. This hypothesis is yet to be established beyond <br />doubt but, if it occurs, the reaction is reversed in the absence of U.V., and <br />immediately so! <br />This ferro-cynide complex reacts immediately with any available divalent metal <br />to form an insoluble compound - MZ Fe (CN)e. In ail cases Save one, these <br />compounds are totally stable over a wide pH range. <br />The exception to this stability is the iron-ferro-cyanide where the two major <br />species are: <br />Fee Fe (CN)a - Ferrous ferro-cyanide <br />Fe~LFe(CN)e]3 - Ferric ferro-cyanide <br />At pH>5 those compounds in water breakdown into metal hydrates and the ferro- <br />cyanide complex as follows: <br />FeZFe(CN)e+4H20 -> 2Fe(OH)Z+Fe(CN)a-~+4H* <br />Fe~(Fe(CN)s(3+12HZ0 -> 4Fe(OH)3+3Fe(CN)6-4+12H' <br />This again leads to the minor possibility of U.V. producing free CN from the <br />ferro-cyanide complex. <br />