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<br />18. Table 5: Would bismuth nitrate be better that: cadntiunr rtirrnte if suede is <br />present? Both nitrate and nitrite are irr[erferents in the cyanide analysis <br />' procedure and will need to be corrected for by the analyst. Will nitrates oxidize <br />arty cyanide in the sample leading to low results? <br />' RESPONSE: There is no real difference in the use of bismuth nitrate or cadmium nitrate in the <br />removal of sulfide. EPA protocols suggest that cadmium nitrate be used. If <br />CMLRD prefers bismuth nitrate to be used, this can be done. <br />' Nitrate and nitrite interferences in the analysis are corrected by adding sulpltamic <br />acid prior to the distillation step in the test protocol. Nitrate and nitrite <br />interferences are usually positive. <br />Nitrates do not oxidize cyanide at ambient temperatures, but only ender the reflux <br />' conditions of the analysis. Nitrates can form HCN during the distillation step of <br />the analysis and produce positive, not negative, interference in the analysis. <br />' 19. The general description of the QA/QC protocol as described se¢nrs reasonable <br />and the cyanide analysis methods proposed /rave worked for EPA water and waste <br />water samples. Since dtere will 6e a major tluantiry of paperwork crcnted in the <br />' course of the analyses, l would suggest an on-going trend report for the <br />constituents of major concern (cyanide arrd specific »retals) at: a biweekly or <br />ntontltly basis so that the trends arc not lost sight of in the mass of results. These <br />tread analyses should be distributed as are the analytical results tl:entselves. <br />' RESPONSE: The request for a trend analysis is one of many data reduction tools potentially <br />used in the analysis of such data. BMR believes it is neither useful or prudent <br />at this stage to impose such additional source of unnecessary paperwork into the <br />process. <br />20. wilt respect to die cyanide analyses, it is prudent to continue to monitor for both <br />' free and complex cyanide so -ltat drere is an opponuniry to check mass balance <br />relationships for total acrd conrplexed cyanides as art internal clreok orr arrolytical <br />validity. /t may also be appropriate to consider mralysis for the cyanides not <br />' amenable to chlorination (CNATC) as a species of possible ftrttrr~ concern. <br />RESPONSE: The issue of free cyanide monitoring was addressed in Harry Posey's Comment <br />' No. 4. BMR is proposing monitoring for WAD cyanide plus those metals present <br />in the tailings which may form WAD cyanide complexes to calculate the mass <br />balance and residual free cyanide concentrations. CNATC analysis offers no <br />advantage over total cyanide and WAD cyanide analyses. <br />' -20- <br />1 <br />LJ <br />