The Dangers Of Aqua Regia: Aqua regia cannot be boiled or simmered in the house or where it is not well ventilated. This can cause serious illness or KILL YOU! Use a vent hood with an exhaust fan or simmer in the open. Hydrochloric acid is very dangerous. It CAN BURN TO THE BONE and is extremely painful. In most cases, it has burned you before you know it. Nitric acid can be absorbed through the skin, causing nitric acid poisoning, which makes you very ill. WEAR RUBBER GLOVES! Aqua regia, nitric acid and hydrochloric acid CAN KILL IF SWALLOWED. Always wear rubber gloves, plastic safety glasses and a plastic or rubber apron. Aqua regia can ruin your clothes and shoes.
Equipment Used
- Furnace or oven for firing. It must heat to 1950 degrees F for the gold and 2100 degrees F for silver. A muffle furnace is best. It fires to about 2300 degrees F.
- Ash-free or coffee filter. An ash-free filter is best, but it costs more and is harder to find.
- Clay crucibles.
- A plastic funnel or strainer to use with filters.
- Beakers or Pyrex containers.
- Hot plate or camping stove.
Ingredients Used
- Hydrochloric acid.
- Nitric acid.
- Formic acid.
- Un-iodized table salt.
- Sodium sulfate.
- Soda ash.
- Borax.
CAUTION! When using this procedure, you will be working with dangerous acids and making a very dangerous solution-aqua regia. Always wear protective clothing and in a well ventilated area.
STEP 1: Dissolve precious metals into a liquid solution.
- Place jewelry and small electronic parts into a Pyrex container or beaker.
- Mix 1 part nitric acid to 3 parts hydrochloric acid in a separate Pyrex container or beaker. make enough of this mixture to more than completely cover the parts. CAUTION! Don’t breathe the fumes and don’t allow any acid to touch your body or clothes.
- Add the acid mixture, very slow, to the parts.
- Simmer on stove or hot plate until all of the precious metals are in solution and all of the nitric acid has been boiled off. It will look like maple syrup and will have a yellow to orange color.
- Add small amount of formic acid to make sure all of the nitric acid has been boiled off. If there is still nitric acid present, a reddish brown gas will be given off. Add hydrochloric acid, if necessary, to keep the parts covered. Continue to simmer until all the nitric acid is gone.
- Filter off any material that is not in solution through a plastic strainer or funnel lined with a filter. Soak this material in lime juice to neutralize the acid on it and discard.
STEP 2: Remove silver from solution and purify silver.
- Add enough water to the acid to double its volume.
- Drop a small amount of non-iodized table salt into the mixture to check for silver. If silver is present, a white substance will fall to the bottom of the container. This is silver chloride. Continue dropping in small amounts of salt until the silver chloride stops falling.
- Filter off the silver chloride through a plastic strainer or funnel lined with a filter. DO NOT DISPOSE OF THE ACID SOLUTION – SET IT ASIDE.
- Rinse the filter and silver chloride.
- Dry the filter and silver chloride.
- Place the filter and silver chloride in a clay crucible and burn the filter by lighting a match to it.
- Cover the silver chloride and burned filter with soda-ash.
- Place the crucible in a furnace or oven and heat to 2100 degrees F until the silver is a smooth honey-like liquid with no lumps in it.
- Immediately, pour the silver into a mold or let it set in the crucible until cool.
- Remove the silver and wash with soap and water.
STEP 3: Remove gold from solution and purify gold.
- Add sodium sulfate to the acid solution, a little at a time. The gold will start to fall. Continue to add the sodium sulfate until the gold stops falling. You could see black specks that look like pepper. This is gold sulfide.
- Filter off the gold sulfide through a plastic strainer or funnel lined with a filter.
- Rinse the filter containing gold sulfide with water.
- Dry the filter and gold sulfide.
- Place the filter and gold sulfide into a clay crucible and burn the filter by lighting a match to it.
- Cover the gold sulfide and burned filter with borax and place the crucible in a furnace or oven and heat to 1950 degrees F until the gold is a smooth, honey-like liquid with no lumps in it.
- Immediately pour the gold into a mold or let it set in the crucible until cool.
- Remove gold and wash with soap and water.
- Add ¼ cup lime juice to the acid mixture to neutralize it and dispose of it immediately.
