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<br />' bird-kill. The method recommended is the use of BEI's "Cytox" <br />chemical. Cytox (derived from ~anide detoxification) is a ferrous <br />sulphate compound "stuffed" with differing levels of zinc. <br />A full description of the chemical and its reactivity is provided in <br />Section 4. Suffice to say if forms a compound with CN that is <br />insoluble and stable over a wide pH range. At a cost of $140 per <br />ton delivered, it will cost approximately $0.07 - $0.14 per ton of <br />ore to remove CN on a continuous basis. Thus, CN in the tailings <br />will be removed quickly and cheaply. <br />The CN becomes locked in a compound that is typically Zn;Fe(CN)-, <br />precipitates and is thus removed by settling. It is totally stable <br />' (see Section 4) unlike the compound formed when pure FeS0.7H~0 is <br />used. In this case, depending upon stoichiometry and pH one or all <br />of three compounds form: <br />' Fe(CN)64 - ferrocyanide <br /> Fe2Fe(CN)66 - ferrous ferrocyanide <br />' Fe~[Fe(CN)6]1 - ferric ferrocyanide <br />' <br /> s above 5 both compounds breakdown into the metal oxide and <br />At pH <br /> Fe(CN)E-". The ferrocyanide, which is highly soluble, remains in <br />' solution and can liberate CN- in the presence of U.V. radiation. <br /> 2. Steo 2: Cu Elimination <br /> Unquestionably Cu can be removed, however, the best and most <br /> economical procedure is yet to be determined. Laboratory work to <br /> determine the exact pH for Cu-CN stripping and then the best <br />' complexing compound is strongly suggested. <br /> BEI feels that the first step is to eliminate Cu in the pond, using <br /> the AVR to modify pH, then adding, before stripping, a complexing <br />' compound to remove the ionized copper. The second phase would be to <br /> complex CN and Cu simultaneously, once the pond has been "cleaned- <br />1 ~p .. <br /> C. SPECIAL COMMENT ON ANALYTICAL TECHNIQUE <br />' We feel that, in the specific case of San Luis, the analytical method in <br /> use is not providing the correct data - and this is positively not a <br /> reflection of the analyst. <br />' The silver nitrate method of CN determination provides exact data on the <br /> amount of CN available to extract gold since the stripping ability of Ag <br /> is similar to Au. However, how to distribute this CN ahalysis is the <br />' problem. For example: <br /> <br /> <br />BE/ <br /> <br />