Gold Refinery Uganda – How to Refine Gold by the Aqua Regia Acid Method
The two acids which are used in this process are concentrated hydrochloric and nitric acids. Nitric acid is very corrosive. When combined with hydrochloric acid, the fumes become much more corrosive. So corrosive, in fact, that they will rust the highest grades of stainless steel with less than 1 second of exposure. For this reason, if you’re using nitric acid, it must be done outdoors, away from anything that may be damaged by exposure to these fumes. If you’re using a nitric acid substitute, it should still be outdoors, or within a self-contained system that neutralizes fumes
Having described its hazards, it must be pointed out that, like most industrial processes, refining gold in acid is quite safe when performed under controlled conditions. In addition, the results of doing your own refining can be quite lucrative. Based upon feedback we’ve received from several hundred shops, approximately 6-10% of your gold profit can be saved by refining gold yourself. For Uganda gold refinery , please contact us
Gather supplies
To refine gold in acid, you will need the following items:
- Heavy gauge plastic buckets or Visionware pots
- Wood or plastic stirring rod
- Protective clothing — minimum requirement: goggles, rubber gloves, rubber apron
- Filtration equipment (optional, but highly recommended)
- Hydrochloric (or muriatic) acid
- Nitric acid, or nitric acid substitute such as MX3 Concentrate
- Baking soda (sodium bicarbonate)
- Urea
- Precious metal detection liquid (stannous chloride)
- A selective gold precipitant, such as Quadratic Precipitant or Sodium Metabisulfite
- Aqua ammonia
- Tap water and distilled water
1. Melt your gold and make shot
This is optional, but recommended if you are using nitric acid instead of a substitute. Small open-up granules are best. If you are refining filigree or jewelry, shotting is not necessary.
2. Pour the shot into one or more Pyrex or plastic containers.
For every ounce of scrap gold you are going to refine you will need a capacity of 300 milliliter. So, for example, if you are refining 10 ounces, you need a 3,000 milliliter (3 liter or 3 quart) container.
3. Add your reagent to the container.
If you are using nitric acid, add 30 ml to the container for each ounce of metal. If you are using MX3 or other nitric acid substitute for each ounce of metal.
If you’re using a nitric acid substitute: add 120 ml of hydrochloric (or muriatic) acid to the container, along with your substitute reagent. The MX3 will not have any effect until this acid is added. Hydrochloric (or muriatic) acid is available in most hardware, paint, or pool supply stores.
4. Allow the mixture to sit for at least 30 minutes
This allows the reagent to dissolve your metal. You may or may not get a strong reaction with brown fumes.
Usually, but not always, the acid reacts slowly at first. After some minutes have passed, however, the acid will become very hot and brown, very corrosive fume (nitric oxides and other fumes) will be generated. Wait a minimum of one hour after the fumes have disappeared before pouring off or filtering the acid. If you can, wait overnight. This will ensure that the acid has had sufficient time to completely dissolve the gold.
5. Pour the acid into another, larger container.
Do not allow any particles to be poured off. If you have a filter funnel, preferably a Buchner filter funnel, use it. If any particles are poured off with the acid, they will contaminate your gold.
The acid will be an emerald green color and should be clear (not murky or cloudy). If the acid is murky, it may contain particles and should be refiltered.
6. Take one quart of tap water and heat it to boiling.
Remove from heat and add one pound of urea to the water. Despite the unpleasant name, this is just a harmless industrial chemical that has no smell and you will use to adjust the pH of the acid.
7. Add your water/urea mix to the acid.
Be sure to do this slowly, to ensure no gold particles are lost. The acid will foam with the addition of the water/urea mix.
Do not add the mix so quickly that the acid foams out of its container. When the acid stops reacting to the addition of water/urea mix, stop. This will raise the pH of the acid from 0.1 To 1.0, neutralizing the nitric acid but not the hydrochloric.
8. Add your precipitant to the solution
There are many different selective precipitants that can be used when refining gold. All will do the job well. However, your local supply house has one or two that they may favor. We recently developed Quadratic Precipitant to overcome many of the problems that refiners commonly experience. For whichever selective precipitant you decide to use, follow the instructions that accompany the product.
Take a quart of water and heat it to boiling in a Pyrex or Visionware container. Remove it from the heat and add to the water one ounce of storm precipitant for every ounce of metal you are refining. If you are refining many ounces of scrap gold, you may need to use more than one quart of water. Do not put your face near the opening of the container. The smell is very strong and pungent.
Add the water/precipitant solution slowly to the acid. Immediately the acid will change to a muddy brown appearance as brown particles of gold form in the water. This brown “mud” is, despite its appearance, pure gold.
9. Give the precipitant about 30 minutes to do its job.
10. Test the acid for the presence of dissolved gold.
Testing is generally done with an aqueous mixture of stannous chloride, hydrochloric acid and pure tin. Generally it’s more convenient to buy this premixed rather than concoct it yourself (see: ready-made detection liquid). The premixed is commercially available as Precious Metal Detection Liquid. Precious metal detection liquid will detect the presence of dissolved gold down to 4 parts of gold per million parts of acid, detecting the presence of about 1/1000th of 1 gram of dissolved gold. Testing for the presence of dissolved gold is absolutely necessary to insure that no dissolved gold is thrown away with the waste acid.
