Have you ever wondered how gold is refined? I know it takes a lot but what, exactly, is the process? And is it something you can venture into?
This comprehensive guide explains how to refine gold, both raw and scrap. In the end, you will be able to decide if it is something you want to do.
Methods Used in Refining Gold
There are different ways to refine gold. But the popular ones are the Wohlwill method, the Miller method, and the fire assay method.
Method 1. Wohlwill Method
This method purifies gold to almost 100 percent purity. It uses electrolysis to do this. In the process, you lower a bar of impure gold into a solution of gold chloride and hydrochloric acid. This is otherwise known as an electrolyte solution.
When you do this, the gold moves to an electrode that is negatively charged. This is called a cathode. The migration to the cathode is influenced by an electric current.
This migration separates every impurity from the substance. It is the impurities you see left behind as residue. The real gold is left highly pure, 99.99 percent pure.
This method takes time and a lot of effort but the results are much better than any other method.
Method 2. Miller Method
In this method, gaseous chlorine is used to separate pure gold from impurities. This is done when the gold has reached its melting point.
What you will see at the end is the impurities floating atop the liquid gold that is purified.
This method is simpler than the Wohlwill method. However, it does not produce gold as pure as that from the former method.
Method 3. Fire Assay Method
This is the most detailed method of refining gold, especially scrap gold. It involves a lot of steps and they are as follows:
1. Testing the Gold
To check what quantity of pure gold you have, you will have to mix it with flux inside a crucible. Along with the flux, you mix in either silver or lead.
The job of the flux is to lower the gold’s melting temperature, to make the testing process easy to finish. And the silver or lead is to separate the real gold from every other metal.
You may choose to use just a sample of the gold you have or use all of the gold.
2. Heating the Gold
The temperature to use for heating the gold should be between 1,000 degrees and 12,000 degrees Celsius.
As soon as the gold, along with the other additives, reaches the temperature, it begins to melt. At this point, the gold drops to the crucible’s bottom while the other metals remain on top.
When the gold reaches the bottom, the lead or silver collects it, making it form a hard button that you can lift out of the crucible.
3. Separating the Gold from the Silver or Lead
Allow time for everything to cool. Then, lift the hard button out of the crucible and put it into a cupel, a porous cup made for this purpose. This is when you place the hard button into a cupellation furnace.
As it heats, the silver or lead mixed with the gold melts and seeps out of the cupel through the holes. If there is any silver left in the gold, putting it in a mixture of nitric acid and hydrochloric acid or just nitric acid will remove the silver.
4. Assessing the Gold
You can choose to send the gold to the right lab for assessment. There, you will know how many karats the gold is.
There are different methods for determining this and some of them are Atomic Inductively Coupled Plasma-Atomics Emission Spectrometry (ICP-AES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).
After this, you can choose what form you want the gold to be – coins and bars are popular.
The fire assay method is one that is industry-standard and highly reliable. It is also a lot more accurate in refining gold than other methods.
However, it involves many steps and requires a lot of effort and time. Therefore, only skilled refiners use it. Because of the meticulousness involved, there is room for mistakes. So if you are not skilled in this, use another refining method.
How to Refine Gold: Breaking It Down
The following are the step-by-step process of refining gold, from finding it to removing impurities:
1. Find the Gold
There are 2 main sources for finding gold.
One is from gold mines. You can hire miners to find the gold. It involves looking at the soil and rocks to determine which are likely to have raw gold under them. This type of gold usually has about 90 percent purity.
The second source of gold is from pawnbrokers. These pawnbrokers sell gold that they get from individuals. The gold usually comes in form of jewelry and is about 37 percent pure.
2. Melt the Gold
For gold that comes from pawnbrokers or any other such source, you can choose to melt it in a crucible with a temperature that is up to 14000C. if you do melt it, you have the freedom to change it into scrap gold bars.
3. Wash the Gold
When you get the gold, you wash it in chemicals, chlorine particularly. The number of washes you put it through is dependent on how much impurities it contains.
You remove base metals when you give it the first wash in the chemical. If there is silver in it, a second wash in the chemical will remove it.
4. Further Melting for Purification
To further purify it, melt the scrap gold bars and cool them. The gold from them will look like cornflakes. Afterwards, you pour the flakes into aqua regia, which is a chemical. You use the chemical to wash the gold.
Then, you turn the gold into liquid, in molten form. And when it dries this time, it looks like sand. In this sand form, it is the purest you can find.
Now, take the sand-like gold back to the crucible and melt it again. This time, when you cool it, you will not see flakes but grains, like rice grains.
This grain form is the final step. In this form, it is so pure, it is almost perfect.
Whatever you want to shape the gold into, you melt the grain and cast it.
Importance of Refining Gold
You may have asked yourself ‘if gold is already pure enough from the mines, can’t I just wash and use it? Why the thorough refining process?’ I will tell you why you need to refine gold, even when it is scrap gold.
You may be surprised to know that not all gold jewelry is made of pure gold. Pure gold is soft so it breaks easily.
Because of this, jewelers have to strengthen to be able to mould it into the shapes they want. Therefore, they add other metals to make it strong. Such metals include silver, platinum and even copper.
To remove the extra metal, a refiner has to wash it to be able to separate the pure gold from other metals.
Ways to Store Your Gold
How you store your gold will depend on the form it takes. If the gold is in the shape of bullion coins or even bars, the storage options are few.
However, if it takes the shape of jewelry or small coins, you have a lot of options.
So, store gold bars and bullion coins in the following ways:
1. Bank Safe Deposit Boxes
Using the safe deposit box in a bank is a good and affordable option. You can get the smallest box for as low as $50 and the biggest for $200 per year.
However, when storing, keep time in mind. Gold is the most liquid metal. But some gold forms are more liquid than others.
A bullion coin sells faster than other forms. You can take it from the box and sell it at any time without an assay.
You should also consider working hours. Storing your gold in a bank means you have to work with the bank’s hours. So if you need it urgently after the bank closes, you may have to wait until it resumes its official hours.
This is perhaps the cheapest option. You can buy or build a safe for the gold and deposit the gold there. But it is also unsafe to do so.
For one, if anyone knows you have pure gold at home, you make yourself a target for burglars. Other accidents may also cause you to lose it.
And once the gold is gone, you cannot replace it easily. This is because gold stored this way is usually not insured.
Private firms use depositories to store your gold, after insuring it. A depository is safe and easily accessible.
Some firms even give you the option of storage in different countries and cities. So not only do you get security but you also get geographic diversification.
In other words, the sale of your gold is not restricted to just one area. But it does not come cheap.
To refine gold, you need to:
- Find it
- Wash it
- Melt it
- Purify it
You should also know what refining method works best for you. But I have to point out that none is easy; they require expertise and professional tools.
If you have any questions about the refining process, ask me in the comments section.