invention and are not to be regarded as limitative. All parts and proportions referred to herein and in the appended claims are by weight unless otherwise indicated.
Example I To a gold cyanide 10 cc. sample of a solution containing, per liter, 3.7 grams of gold as potassium gold cyanide, 21. grams of KCN, and 188 grams of KOH, there is added a mixture of 0.05 gram of sodium hydrosulfite and 0.05 gram of sodium acetate with agitation, the resulting mixture maintained at a temperature of about 180 F. for 20 minutes and the precipitated gold filtered off and weighed to determine the yield or percent recovery of the gold originally present in the solution. The same procedure is repeated for 40 and 60 minute durations to determine the degree of redissolution of precipitated gold.
For comparative purposes, the procedure of the preceding paragraph is repeated but using dextrose and sodium citrate, respectively, instead of sodium acetate. The results of these procedures are shown in the following table.
Percent Recovery Alter- Prccipitant 20 min. 40 min. 60 min.
The above results show that a 100% recovery is obtainable with each of the precipitant mixtures, but that Whereas redissolution of gold begins after 20 minutes using dextrose as additive and after 40 minutes using sodium citrate as additive, the use of sodium acetate as additive results in a 100% recovery after 40 minutes and an effective inhibition of subsequent redissolution of the precipitated gold. The use of 0.10 g. of sodium hydrosulfite as the sole precipitant in the above procedure yields results approximating those obtained with the mixture of 0.05 g. each of sodium hydrosulfite and dextrose. When other water soluble alkali metal alkanoates described above are employed in the procedure of this example instead of the sodium acetate, similarly improved results are obtained,
Example II When the procedure of Example I is repeated but using as the initial gold cyanide solution a cc. sample of a solution containing, per liter, 37 grams of gold as potassium gold cyanide, '30 grams of KCN, and 150 grams of KOH, and 0.5 gram each of sodium hydrosulfite and additive in each of the precipitant mixtures, similarly improved results are obtained with respect to percent recovery and inhibition of redissolution of precipitated gold.
This invention has been disclosed with respect to certain preferred embodiments, and it will be understood that various modifications and variations will become obvious to persons skilled in the art and are to be included within the spirit and purview of this invention and application and the scope of the appended claims.
I claim:
1. A method of recovering gold from an aqueous solution of alkali metal gold cyanide comprising adding to the solution an alkali metal hydrosulfite in a molar amount at least equivalent to the gold in said solution and about 0.2 to 20 parts of a Water soluble alkali metal alkanoate per part by Weight of the hydrosulfite, maintaining the resulting solution at an elevated temperature above about 150 F. until cessation of precipitation of the gold, and removing the precipitated gold from the solution.
2. A method of recovering gold from an aqueous solution of alkali metal gold cyanide comprising adding to the solution an alkali metal hydrosulfite in a molar amount at least equivalent to the gold in said solution and about 0.2 to 20 parts of alkali metal acetate per part by weight of the hydrosulfite, maintaining the resulting solution at an elevated temperature above about 150 F. until cessation of precipitation of the gold, and removing the precipitated gold from the solution.
3. A method of recovering gold from an aqueous solution of alkali metal gold cyanide comprising adding to the solution of sodium hydrosulfite in a molar amount at least equivalent to the gold in said solution and about 0.2 to 20 parts of sodium acetate per part by weight of the hydrosulfite, maintaining the resulting solution at an elevated temperature above about 150 F. until cessation of precipitation of the gold, and removing the precipitated gold from the solution.
4. A method of recovering gold from an aqueous solution of alkali metal gold cyanide comprising adding to the solution of sodium hydrosulfite in a molar amount at least equivalent to the gold in said solution and about 0.5 to 5 parts of sodium acetate per part by weight of the hydrosulfite, maintaining the resulting solution at an solution at an elevated temperature above about 150 F.
until cessation of precipitation of the gold, and removing the precipitated gold from the solution.
5. A method of recovering gold from an aqueous solution of alkali metal gold cyanide comprising adding to the solution of sodium hydrosulfite in a molar amount at least equivalent to the gold in said solution and about 1 part of sodium acetate per part by weight of the hydrosulfite, maintaining the resulting solution at an elevated temperature above about 150 F. until cessation of the precipitation of the gold, and removing the precipitated gold from the solution.
6. A method of recovering gold from an aqueous solution of alkali metal gold cyanide comprising adding to the solution an alkali metal hydrosulfite in a molar amount at least equivalent to the gold in said solution and about 0.2 to 20 parts of a Water soluble alkali metal alkanoate per part by weight of the hydrosulfite, and after cessation of precipitation of the gold, removing the precipitated gold from the solution.
7. A method of recovering gold from an aqueous solution of alkali metal gold cyanide comprising adding to the solution an alkali metal hydrosulfite in a molar amount at least equivalent to the gold in said solution and about 0.2 to 20 parts of alkali metal acetate per part by Weight of the hydrosulfite, and after cessation of precipitation of the gold, removing the precipitated gold from the solution.
8. A method of recovering gold from an aqueous solution of alkali metal gold cyanide comprising adding to the solution of sodium hydrosulfite in a molar amount at least equivalent to the gold in said solution and about 0.2 to 20 parts of sodium acetate per part by weight of the hydrosulfiite, and after cessation of precipitation of the gold, removing the precipitated gold from the solution.
References Cited by the Examiner UNITED STATES PATENTS 545,852 9/1895 De Wilde l06 1,426,517 8/ 1922 Sulyberger 75108 1,479,542 1/ 1924 Hirschkind 75l06 3,147,154 9/1964 Cole et al. 75108 3,215,524 11/1965 Fetscher et al 75l06 References Cited by the Applicant UNITED STATES PATENTS 2,100,865 11/ 1937 Mills et al.
2,913,336 11/1959 Dean.
2,945,757 7/ 1960 Hoekstra.
DAVID L. RECK, Primary Examiner.
N. F. MARKVA, Assistant Examiner.
KUTIPAN PATEN
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US545852 * 1
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