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<br />A 5 C <br /> <br /> based on previous experience, it is not unusual for free cyanide <br /> determinations to be significant overestimates of the cyanide present when <br /> thiocyanate is present in the solutions being analysed. Thiocyanate is a <br /> positive interference in the free cyanide analytical method; and <br />' " <br />" <br /> if the WAD cyanide values determined by Laboratory <br />A <br />are not considered <br />' (as discussed abovel, and the total cyanide values are accepted as correct <br />(they are, in fact, overestimated), the free cyanide values determined by <br /> Laboratory "A" are not correct. This is because if the free cyanide value is <br /> added to the metallo-cyanide complexes which would report to the WAD <br />' cyanide analyses, (based on the metal values determined in the samples), <br /> these exceed even the total cyanide overestimate (e.g., sample 4: FCN = <br />' 93 mg/L, metal cyanide complexes require at least 80 mglL cyanide giving a <br /> total of 173 mglL cyanide. Total cyanide estimate is 160 mg/L by Laboratory <br /> "A" and 126 mg(L by Laboratory "C"). <br />' <br /> The computations given for sample 4 to illustrate the observations made above can <br />' be repeated for each of the samples, with similar conclusions. Accordingly, it is <br />concluded that the free cyanide values determined on these four samples are <br /> incorrect. <br /> <br /> <br />LJ <br /> <br />t <br /> <br /> <br /> <br />7 <br />