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SENT BY~PMHS <br />A S G I <br />w,a~.w~n.n~mtwo.e~a <br />5-26-92 ~ 1335 <br />303~3040~C0 MI(~ED LAND REC'L ~# 4 <br />Samole 4: Collection Pond <br />total cyanide - 12t3 mg/L <br />_ WAD cyanide - 112 mg/L <br />- free cyanide - (WAD cyanide -minimum WAD motallo-cyanide <br />complexes =maximum theoretical value !for free <br />cyanide) <br />112 - 80 = 32~a/L/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 den be made <br />by considering all the metal data and by choosing the most probable met~llo-cyanide <br />complex end not the minimum metal oxidation state. The letter will mean more <br />cyanide is needed to account for the motallo-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 bean calculated using the mean metal a~halyses and <br />-- taking 10% of the Copper cyanide as being as Cu(CN13 , with 9096 of the copper <br />cyanide being CufCN) 2. If any CufCN-q were to be present or the mass bf CuICN~ <br />increased, the residual free cyanide value would decrease commensurately. <br /> <br /> <br />1 <br />9 <br />M. <br />