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~ ::,lU ~Jtld pv cl ~,b. c JdC' <br />~- <br />/ ~~ <br />` APPENDIX I <br />GENERAL COMMENTS <br />It may be beneficial for all of us to discuss now, certain future considerations <br />that the state must address to help prepare the way. There is no particular <br />order to these comments. <br />1. Cyanide Definitions <br />Definitions within the mining, chemical and medical industry abou cyanide" are <br />quite varied. In the gold processing industry we talk about 3 c snide "types," <br />namely Free, MAD and Total. We at 9EI agree with the generally h~1d definitions <br />of the industry, as follows: <br />Free - Limited to only 2 species: (CN)- and HCN. (CN) is highly soluble <br />in water but it exists exclusively only at pH > 11.0.E NCN exists, <br />exclusively, at pH < 8.5. At pH's between 8.5 and 11.10 Doth species <br />mutually exist in proportion to the pH, see attached fig. i. <br />The only exact way to be certain of free-cyanide content ib to adjust the <br />pH to 11.0 or greater and analyze for (CN)~, once all HCN fs converted to <br />(CN)~, by ion chromatography. The silver nitrate technique is accurate, <br />but interference often occurs from WAD's, <br />MAD - "Weak Acid Dissociable Complexes" are those metal-cy~nide complexes <br />which can, under certain acidic conditions, liberate (CN) to the "free" <br />stale but which, under typical analytical conditions are often not <br />revealed. Attached as table 1 are these complexes in rder of their <br />strength (resistance to breakdown). WAD analysis is first ccomplished by <br />distillation and therefore WAD inevitably also includes t e free-cyanide <br />component of the solution, <br />Hence WAD cyanide analyses must show a greater cyanide 1ev~1 than a free- <br />eyanide analysis. <br />Total - A total cyanide analysis is composed of all the fr e-cyanide, all <br />the WAD cyanide and all the cyanide not recovered by disti lotion. Thus, <br />immutable compounds such as Zn2Fe(CN)8 also then "give-up their (CN) to <br />the total_analysis. This is accomplished by digestion, they complexing to <br />free (CN) . <br />The writer considers the key components to be Free and WAO since immutable <br />compounds present no hazard. <br />2. Cyanide Concentrations at San Luis (Doc No 2382F) Point ( U <br />BMG has been restricted to "must attain total cyanide levels of 1 ss than 4.4 ppm <br />or less, and the weak-acid-dissociabte levels of less than 3.8 pm." <br />With respect, these are unattainable anywhere in the world in any ~go1d extraction <br />process. Before further discussion, however, two points of cl riflcation are <br />offered. ~ <br /><SiE'd wd6r:LO 26. LO adH <br />