The processing circuits where cyanide loss should be considered in the present paper include grinding and flotation. It is generally observed that in flotation circuits, the pulp pH is typically adjusted in the mildly alkaline range with little cyanide loss. However, the pH of the milling pulp drops significantly as a result of certain interactions including the hydrolysis of metal species to generate acid and carbon dioxide uptake from the air forming carbonic acid and oxidation of sulphur species in the sulphide minerals. Low pH may cause cyanide loss via HCN volatilisation during milling and probably change the cyanide speciation. In the present study, the HCN volatilisation rate from the flotation pulp with modified pH 10 is generally low as long as the cyanide is dosed after grinding circuit, while the majority of cyanide exists as CN− in the solution.