| 摘要 |
<p>PURPOSE:To produce high-purity gold having >=99.99% purity efficiently, by reducing the greater part of gold from a cyanoauric acid soln. contg. impurities with a reducing agent and filtering the same, reducing the remaining gold together with the impurities, mixing the resulted impure gold with the above-mentioned soln. and melting the same. CONSTITUTION:A reducing agent such as Al is added to a cyanoauric acid soln. contg. impurities such as silver, copper, Ni, Pt or the like to reduce the greater part of gold. The reduction curve 2 of impurities in this case rises sharply when the rate of reduction in a reduction curve 1 for gold exceeds 95% as shown in the figure; therefore, the reduction is stopped just before the curve rises. The greater part of high-purity gold having >=99.99% purity is filtered and recovered from said soln., whereafter the impure gold is fully reduced from the soln. contg. gold in a decreased concn., to obtain impure gold. The impure gold is then remelted to prepare a cyanoauric acid soln. Said soln. is mixed with the next cyanoauric acid soln. and the soln. is subjected again to the reduction treatment. Gold having high purity is recovered in succession by repeating the above-mentioned operations.</p> |
