| 摘要 |
<p>Noble metals such as gold and silver are recovered from ores by lixiviating with an acid solution of thiourea in the presence of an oxidising agent and a reducing agent ; the concentrations of thiourea and formamidine disulphide in the solution are determined by analysis, eg by liquid chromatography, and an amount of oxidising agent or reducing agent is added to maintain the molar ratio of thiourea : formamidine disulphide to between 2:1 and 5:1. The oxidising agent may be ferric ion or hydrogen peroxide, the reducing agent may be SO<SB>2</SB> or sodium metabisulphite and the acid may be sulphuric.</p> |
