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Rr 112 Toxicity <br /> In order to determine the concentration of a compound at which a <br /> waste would fail the 50 mg/kg threshold, the equation can be solved <br /> for %A,: <br /> 100 T . <br /> $A: _ -------- ------ <br /> Calculated -LD,, <br /> To solve the a ation for sodium cyanide, let: <br /> alculated LD,, = 50 mg/kg (the regulatory threshold) <br /> T,= 6.4 mg/kg <br /> therefore: <br /> 100 6.4 mg/kg <br /> $ _ --------------------- <br /> 50 mg/kg <br /> $ 12.8%; or 128,000 ppm. <br /> If the concentration of sodium cyanide in a waste equals or exceeds <br /> 128,000 ppm, the waste would be considered extremely hazardous'. <br /> If the particul r cyanide compound is not known, or if only the <br /> concentration of the cyanide radical [CN-) (free cyanide) is known, <br /> it is possible to determine the proportion of the above <br /> concentration wh ch is CN' using the ratio of molecular weights: <br /> Molecular wfight sodium cyanide (NaCN) 49.01 <br /> Molecular w;fight cyanide radical (CN') 26.02 <br /> Percent (by weight) CN' in NaCN 53% <br /> 128 , 000 ppm 53% (0.53 ) 67,840 ppm. <br /> Therefore, if a waste has a concentration of "free cyanide" (CN') <br /> of greater than or equal to 67,840 ppm, it would be considered <br /> extremely hazardous waste. <br /> NOTE: If �th6 cyanide compound(s) is(are) .known, #hese <br /> 'These calculations to determine the threshold concentrations <br /> of cyanide in a waste are based on the assumption that the waste <br /> solution is in the alkaline range of the pH scale. If the solution <br /> were neutral or acidic, portions of the concentration of cyanide <br /> would be converted to HCN, and potentially release to the air, <br /> posing an inhalation hazard. The acute inhalation LCA, for HCN, <br /> however, is 484 ppm (for rats) , and not below the 100 ppm threshold <br /> in §66720(a) (3) ( herefore not extremely hazardous) . <br />