Abstract: A precipitating agent for precipitating precious metals such as gold from aqueous cyanide solution of the precious metal ions includes aluminum powder and a reducing agent such as sodium hydrosulfite, sodium borohydride or hydrazine. The precipitating agent may also include an alkali metal carbonate, such as potassium carbonate, as an activator. The precipitating agent efficiently reduces the precious metal ions to elemental metal for recovery and also consumes a portion of the cyanide content, which is often high in such solutions.The method of use includes adjusting the precious metals cyanide solution to a high pH, adding the precipitating agent with agitation, preferably in incremental portions of the amount required. The solution is allowed to stand to permit the precipitated metal to settle, and the metal is separated from the solution.

Abstract: Precious metals such as gold and silver are recovered from aqueous cyanide solutions thereof by a stepwise process. The pH of the solution is, if necessary, initially adjusted to about 13 and thereafter is adjusted and maintained at 10 or above throughout the process. A "starter" carbonyl compound (e.g., formaldehyde or dextrose) which reacts with free cyanide ions is dissolved in the solution. Following this, an "accelerator" (e.g., hydrogen peroxide or a persulfate) is added and the solution is heated to aid in conversion of free cyanide ions to other chemical species. Finally, a "clarifier" (e.g., hydrazine or a hydrosulfite) is added and the elevated temperature is maintained for at least a brief period after the addition. The solution is then cooled and the elemental precious metal particles formed are allowed to settle and are separated from the supernatant solution.

Abstract: A process for making high purity alkali produced is sulfite substantially free from chloride ions includes the step of admixing gold chloride solution with magnesium oxide at an alkaline pH to form magnesium aurate which is recoverable as a coating upon the magnesium oxide precipitate. The magnesium aurate is thereafter admixed with a solution of alkali metal sulfite at an alkaline pH to produce alkali metal gold sulfite and a precipitate of magnexium oxide.When the alkali metal gold sulfite being produces ia a potassium gold sulfite, the process desirably includes the step of admixing the potassium gold sulfite with a sulfamic acid compound to provide stability. The magnesium aurate precipitate is desirably rinsed to remove chloride ion contamination.