Before ever starting a project or business it is important to know that safety precautions. Protective eye-ware, hands, and breathing mask are needed to insure a safe completion of the gold refining process.
Survey and Measure
First, measure up how much gold feed stock is being refined and weight it by the gram. Then you must calculate the amount of silver needed to get gold to 6k. The ratio is 2: 1, meaning twice the amount of gold to silver. This means for example, if your gold jewelry weights 50.4 grams, then 16.8 grams of silver is needed.
First step is to take the gold and incinerate it, not to melt but only to remove external impurities with a propane torch. By adding 1/3, which is the calculated amount of silver to the incinerated gold, the process called ” Inquarting “, resulting in alloy that will be 6k gold.
Place the scrap gold jewelry, with the inquarting silver into a crucible, and then apply a flame MAPP gas torch. Make sure to stir well with a graphite rod. Once all the content in the crucible are melted, use a metal container of tap water and dump the contents into the container. Next just dump the tap water out and rinse the inquarted 6k gold with the distilled water to avoid silver chloride formation in your reaction vessel. Simply let dry and gather the smelted gold mix up and place on a piece of paper or within a bowl container.
Adding Nitric Acid
This must be done outdoors away from people and pets, because the fumes are deadly poison. It good to use a heavy Pyrex coffee pot with a lid placed on low heat. One eye hot plates with a flat burner surface are preferred for low heating of glass containers. By adding nitric acid to the inquarted gold that is covered with distilled water, most of the base metals are dissolved in the nitric acid. Notice that the fumes are light. This indicates that the nitric acid is used up. All that remains is nearly pure gold in the bottom of the coffee pot.
The solution should turn rather a blue color. Save the blue liquid, it is mostly silver nitrate and the silver can be recovered. The solution turns blue because of the silver contents and the nitric acid reaction. Next, pour off the nitric acid solution leaving the gold in the bottom of the Pyrex coffee pot. Now, the washed gold is given a second treatment with concentrated nitric acid, but without the distilled water. The solution should be kept on medium heat for 30 minutes. Save the poured off acid because it can be used to treat silver for a later date, plus contains some silver. Next, pour hot distilled water into the glass container to clean the gold. Save the water it has silver in it.
Add Aqua Regia
Aqua Regia is a solution mix of hydrochloric and nitric acid. Add aqua regia to the gold while off the heat source. Place the glass container coffee pot on low heat to help the reaction. By adding about 10 drops of sulfuric acid to precipitate out any lead with a dropper, further refines the gold in the aqua regia solution. Next, by filtering this should remove precipitated lead, and other solids left behind in the filter paper and funnel. The solution should be bright yellow. It's good to test the solution with stannous chloride, which is a chemical that detects if gold residue is prevalent. Adding a drop on a napkin with a drop of the aqua regia solution will show if gold is in the solution. It should be within the solution.
Dropping the Solution
We use sodium metabisulfite dissolved in distilled water to drop the gold out of the aqua regia solution through a process called precipitation. Two tablespoons of sodium metabisulfite and stirring should start the precipitation. Wait 24 hours before checking to complete the process. Once the gold has dropped to the bottom of the glass container, pour off the liquid, and wash the gold several times with boiling distilled water. Next, pour off the water and dry slowly over low heat.
Transfer the gold to a melt dish and begin to heat with a MAPP gas torch. Pour the bar into a preheated mold. Flip the graphite mold over into a metal container with water. This bar should be the result of a single refining, and it should take about 8-10 hours.