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• iii iiiiiiiiiiiuiii <br />CYTOX CHEMICALS ~-b~ <br />The cytox group of chemicals are all hybrids of ferrous sulphate, in that they <br />e contain zinc (Zn) stuffed into the ferrous sulphate lattice, in varying amounts. <br />I:, <br />Cytox behaves similarly to ferrous sulphate in that it complexes CN~, unlike all <br />the other methods of CN~ detoxification, but is unlike ferrous sulphate in that <br />the end product of reaction is a totally stable compound. Thus there are two <br />aspects to the use of cytox: <br />1. The ability to remove free CN from solutions <br />2. The ability of the end product of reaction to remain stable <br />Before discussing these two separate abilities it is valuable to understand the <br />background to the Fe- CN reaction. <br />Background <br />Iron (Fe) in the form of the ferrous ion is used in humans as the antidote to CN <br />poisoning because its reaction with CN is rapid and because the product of <br />reaction is not toxic. <br />This end product is the ferrocyanide radical Fe(CN)5~` which is stable across a <br />wide range of pH. <br />This reaction is the basis for the use of ferrous sulphate (FeSOd7Ht0) as a CN <br />destruction agent in the gold-mining industry, to the extent of 10,000 tons per <br />annum in 1991. <br />The basis for its use is represented by the equation: <br />6NaCN + FeSO. = Fe(CN)5-4 + Na~S01` 4Na0H <br />When ferrous sulphate is present in excess then a further step is represented by <br />the equation: <br />Fe(CN)6-4 + 4Na0H + 2FeS0; = Fe~Fe(CN)6 + 2Na2S0y + (OH)4 <br />Obviously, neither of these equations express all the possible reactions but they <br />are "generically" correct. <br />The Fe(CN)~'" radical is highly soluble in water whereas the compound Fe;Fe(CN)~ <br />is insoluble and precipitates thereby removing CN from the environment. <br />The Fe(CN)6; radical will just as equally form insoluble compounds with other <br />divalent metals such as Zn" and Cu`~ if and when they are available. Thus one <br />tries to remove CN by forming a compound of the type <br />MpFe(CN)a M = Divalent metal <br />However, despite the strength of the Fe(CN),~s radical which is nearly impassible <br />to break-down, when M is iron, as opposed to copper or zinc, then a compound of <br />considerable instability is formed. <br />