Techniques for the determination of cyanide in a process environment: A review

The determination of cyanide in various forms is important for industrial p rocesses as well as for environmental investigations and monitoring associa ted with these processes. The accurate determination of cyanide is difficul t for various reasons. Depending on the pH of the solution, cyanide is pres ent both in molecular form (HCN) and ionic form (CN-). Furthermore, cyanide is a good complexing reagent and reacts with almost all cations resulting in complexes with widely varying properties, such as stabilities, solubilit ies and rates of reaction. Cyanide also breaks down in sunlight. and air, s o that sampling and sample treatment become very important aspects to consi der in the methodologies. During the last fifty years the determination of cyanide has been approached from various angles and a myriad of methods has been developed for its determination. This study represents a survey of me thods commonly used in industrial laboratories for the analysis of cyanide- containing solutions. An overview of the nomenclature often used for the va rious forms of cyanides is discussed and the values resulting from a partic ular analysis will be interpreted. Most common interferences in samples ori ginating from gold processing plants will be discussed.