scope:

This test method covers the determination of free cyanides in waters and wastewaters. Free cyanide is here defined as the cyanide which diffuses as cyanide (HCN), at room temperature, from a solution at pH 6.²

This test method does not include complexes that resist dissociation, such as hexacyanoferrates and gold cyanide, nor does it include thiocyanate and cyanohydrin.

This test method may be applied to water and wastewater samples containing free cyanide from 10 to 150 μg/L. Greater concentrations may be determined by appropriate dilution.

This test method has been fully validated by collaborative testing as specified by Practice D2777.

The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see 8.6, 8.9, Section 9, and 12.2.1.

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

² The paper by J. M. Kruse and L. E. Thibault, "Determination of Free Cyanide in Ferro- and Ferricyanides," Analytical Chemistry, 45(13): 2260-2261; 1973 Nov., recommends a diffusion at pH 7. The ANSI modification (ANSI PH 4.41-1978) uses pH 6. Using the conditions of the ANSI method, diffusion is completed within 4 hours at pH 6. Longer diffusion time was required at pH 7 on the samples analyzed.