This test method is useful for analysis of many natural waters that contain thiocyanate from organic decomposition products and waste water discharges. Some industrial wastes, such as those from the metallurgical processing of gold ores, steel industry, petroleum refining, and coal gasification, may contain significant concentrations of thiocyanate. Thiocyanate per se is not recognized as a toxic chemical compound. However, when chlorinated, thiocyanate is converted to the highly toxic and volatile cyanogen chloride at high pH. Oxidation of thiocyanate may also release toxic hydrogen cyanide. The user of the method is advised to perform holding time studies in accordance with Practice D 4841 whenever oxidants are present in the samples.

For information on the impact of cyanogens and cyanide compounds, see Appendix X1 of Test Method D 2036.

1.1 This test method covers the quantitative colorimetric laboratory measurement of dissolved thiocyanate in water, waste water, and saline water in the range from 0.1 to 2.0 mg/L. For higher concentrations, use an aliquot from the diluted sample.

1.1.1 Validation—This test method was validated over the range of 0.07 to 1.42 mg/L. This test method was validated at nine laboratories at four levels. This test method may be valid for reporting results down to lower levels as validated in individual user laboratories.

1.1.2 Application—This test method has been validated in reagent water, Type II, in multiple laboratories and 7 natural waters, 1 laboratory effluent, 1 steel mill effluent, and 2 dechlorinated and treated sanitary effluents in single laboratories. It is the user's responsibility to assure the validity of the test method on any untested matrices.

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

1.3 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 and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 9.