The remaining particles on the original paper will be fine gold and non-magnetic black sands. Again, the gold can be separated from the black sands by lightly blowing across the paper. Spearation can be encouraged by lightly tapping or vibrating the paper and insuring that only a little concentrate is present on the paper. The remaining fine gold can be placed in a storage bottle. One such method,which has been widely used in the past, involves the cleaning the concentrate with nitric acid then recovering gold by amalgamation with mercury.
Nitric acid are dangerous and mercury is poisonous.
Another method uses cyanide to dissolve gold into a solution with a pH greater than 10. The resulting powder after throughly rinsing can be melted. The zinc will float on top of the gold and can be skimmed off. If the pH of the dissolution solution is not controlled, hydrogen cyanide can form if the pH becomes to low. Hydrogen cyanide is what is used in gas chambers.