| 摘要 |
<p>PURPOSE:To recover simply and easily high purity gold by mixing crude gold with NaCl powder and melting the mixture at a specified temp. CONSTITUTION:Copper and silicon are removed from a precipitate produced by electrolyzing copper, and the copper-free precipitate is suspended in an NaCl soln. Gaseous chlorine is blown into the resulting NaCl slurry to fix silver as residue and to prepare a soln. contg. leached gold. Ammonia is added to the soln. to precipitate impurities such as Pt and Pd, and gold is extracted by adding a solvent which dissolves selectively gold such as dibutylcarbitol. A reducing agent such as oxalic acid is added to the solvent phase contg. the extracted gold to deposit gold by reduction. The resulting reduced crude gold powder of about 99.3-99.5% purity is uniformly mixed with about 1-10 times as much NaCl powder as the gold powder, and the mixture is charged into a high purity graphite crucible and melted at 1,100-1,200 deg.C. After taking out NaCl as scum, gold of >=about 99.998% purity is obtd.</p> |
