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~] <br />' A S C 1 <br />w~. <br />Sample 4: Collection Pond <br />' - total cyanide - 126 mg/L <br />- WAD cyanide - 1 12 mg/L <br />' - free cyanide - (WAD cyanide -minimum WAD metallo-cyanide <br />complexes =maximum theoretical value for free <br />cyanide) <br />' 1 12 - 80 = 32 mg/L <br />In practice, the above method gives the maximum potential free cyanide levels in <br />' samples. Amore realistic maximum estimate of the free cyanide levels can be made <br />by considering all the metal data and by choosing the most probable metallo-cyanide <br />complex and not the minimum metal oxidation state. The latter vuill mean more <br />cyanide is needed to account for the metallo-cyanide complexes, reducing the free <br />cyanide residual value. "Realistic" maximum free cyanide levels would be: <br />' • Sample #1: 184 mg/L <br />Sample #2: No estimate <br />' Sample #3: 22 mg/L <br />Sample #4: 15 mg/L <br />' These free cyanide values have been calculated using the mean metal analyses and <br />taking 10°~ of the copper cyanide as being as Cu(CN13 , with 90% of the copper <br />' cyanide being CuICNI 2. If any Cu(CNIq were to be present or the mass of Cu(CN~ <br />increased, the residual free cyanide value would decrease commensuraRely. <br /> <br />1 <br /> <br /> <br />1 <br /> <br />9 <br />