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Thus pure ferrous sulphate injected in excess into tailings that contained free CN~, low Zn and Cu would produce the following end-products of reaction: FetFe(CN)S - ferrous ferrocyanide ~. Fe{[Fe(CN)o]3 - ferric ferrocyanide These compounds are only stable in pH's below 5. Above pH 5 they convert to metal oxide and the radical Fe(CN)fi~4. The danger of this is multifold: 1. Ground xater standards require a pH > 6 2. At pH > 6, Fe(CN)5~4 exists 3. Under U.V. radiation Fe(CN)B~y can liberate free CN 4. Since Fe(CN)E-4 is highly soluble in water then soluble Fe levels in ground water always exceed standard. The benefit of using Cytox is that it contains its own Controll4d Level of M'''. Hence it is tailored on a site specific basis to remove free CN~ as a stable insoluble compound as illustrated in the equation: 6NaCN + 3(0.66 Zn 0.33Fe) SOi ~ ZnZFe(CN)a + 3Na2S0~ Similar tailoring can help with the removal of free ions of Cu, Zn, etc. in the tailings. Abilitv of Cvtox to Remove CN from Aqueous Solution BEI believes that the evidence that Cytox can successfully remove CN~ from solutions is presented in its Report iti entitled "Destruction of CN in Ponds, etc" attached hereto. Abilitv of Cvtox to Produce a Stable Reaction Produce When Combjned With CN~ This evidence is more recent and comes from studies conducted by BEI in the laboratories of Hazen Research and Skyline Lab. Because of ground water regulations, the effects of U.V. radiation on the - Fe(CN)S-d radical, and the possible effects of pH on the er6d-products of reaction, BEI conducted a study to determine the stability of these end-products. Under laboratory conditions deionized water solutions of NaCN were mixed separately with a deionized water solution of Cytox and FeSO,. In both cases the ._. .,. -_. _. mixing caused a.precipitate, presumed, respectively, to be predominantly ZnpFe(CN)E and Fe~Fe(CN)~. These precipitates were removed, dried and then themselves, separately added to deionized water. These suspensions were then adjusted to pH's of 7, 6, 5, 4 respectively and, over -- a period of time, their dissolution was measured. The results are provided (briefly) in figure 1. It is evident that, regardless of pH, the reactant from Cytox is completely stable whereas that derived from ferrous sulphate becomes more unstable the higher the pH, as denoted by Schiller in his landmark publication.