Laserfiche WebLink
SENT BY~PMHS <br />A t I <br />5-26-92 ~ 1334 ; 3032,9,~3040~C0 MINED LAND REC'L ;# 2 <br />" based on previous experience, it is not unusual for fr6el cyanide <br />determinations to be significant overestimates of the cyanide pre ant when <br />thiocyenate is present in the solutions being analysed. Thiocy~nate is a <br />positive interference in the free cyanide analytical method; and <br />if the WAD cyanide values determined by Laboratory "A" are not donsidered <br />fas dlscussad ebovel, and the total cyanide values are accepted es correct <br />(they ere, in fact, overestimatedl, the free cyanide values determined by <br />Laboratory "A" are not correct. This is because if the free CyeniQe 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 samplesl, <br />these exceed even the total cyanide overestimate le.g., sample 4t FCN = <br />93 mg/L, metal cyanide complexes require at least 80 mg/L cyanidb giving a <br />total of 173 mg/L cyanide, Total cyanide estimate is 160 mg/L by Uaboratory <br />"A" and 126 mg/L by Laboratory "C"I. <br />The computations given for sample 4 to illustrate the ohservations made Above Can <br />be repeated for each of the samples, with similar conclusions. Accordingly, it is <br />concluded that the tree cyanidE values determined on these four sarhples are <br />incorrect. <br />7 <br />