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How Gold Is Refined: A Step-By-Step Guide
Updated: November 16, Reader-Approved References. You may want to make some extra money by refining your own gold at home, or you may be a jeweler who wants to refine gold in-house. There are multiple ways to refine gold on a small scale as long as you take appropriate safety measures.
This article will teach you to refine gold using the aqua regia method. How is the process of melting gold different if you're melting small pieces of jewelry instead of larger pieces? Not true! Gold melts at the same temperature regardless of whether it's a necklace or a ring.
Look for another response to explain how melting small pieces differs from large pieces. Choose another answer! Not quite! Your equipment should be the same for any size piece of jewelry. When melting gold, you'll need a crucible, tongs, a torch, and a fireproof surface. Pick another answer! When melting larger pieces, you have an extra step of making shot particles, which involves separating the heated gold into chunks and allowing them to harden.
You can skip this step if the jewelry is small to begin with. Read on for another quiz question. Use a crucible made of graphite for both large and small pieces of jewelry.
Graphite is a good choice because it won't melt with the gold when you apply the heat. Absolutely not! Always melt gold on a fireproof surface. Practice extreme caution when handling the torch and the heated crucible. Try another answer No way!The answer is very simple: We cannot use gold in its raw form.
It is a precious, noble metal that comes in different forms: As an alloy of silver and platinum, an amalgam, as a part of a stone, or in scattered particles. Gold must be refined from its alloys or amalgam forms in order to get the pure gold that you can use in whichever way you like. Several people think that their gold pieces are pure.
That may not be true, because an alloy of gold and copper still have a brilliant shining color, but it lacks other chemical properties of gold.
When gold is refined, this process increases its value and market worth. More so, it helps in the preservation of this noble metal because when exposed to some chemicals, gold could be oxidized. Generally, gold can be refined using these two-best-known gold-refining procedures: Aqua Regia and gold electrolysis. Both of these techniques can be used to separate gold from other metals.
This is because a little piece of other metals in gold can change its properties and value. Aqua Regia has been used to separate gold from other metals for a long time. Actually, Aqua Regia is a chemical solution which fumes, and it is corrosive in nature. It is either yellow or red in color. You can freshly prepared Aqua Regia by mixing concentrated hydrochloric acid with concentrated nitric acid. Aqua Regia gets its royal name from its ability to dissolve some noble metals such as gold and platinum.
The diagram below explains the Aqua Regia gold refining process:. Since gold naturally occurs as an alloy—in a mixture with other metals—a process such as Aqua Regia will be a good method to obtain gold in its purest form.
The physical steps involved in this procedure are highlighted below:. You will obtain pure gold powder, separated from the solution of other metals. Wash, dry, and granulate the gold powder. The final result will be your pure gold grain.
Since the purpose of the procedure above is to separate a pure gold from other metals, the same process can be used to obtain other noble metal such as silver and palladium. Here is the list of some of the equipment required to successfully carry out an Aqua Regia gold-refining process:.
Aqua Regia gold refining and sedimentation machine. Aqua Regia system is one of the best approaches anyone can use to obtain pure gold grain and bars from other metals. This is basically a series of chemical processes reactions. The actual chemical representations of this gold-refining procedure are provided below:. Step one: The base chemicals, concentrated hydrochloric acid and concentrated nitric acid are mixed together:. NOCl : Nitrosyl chloride. Step two: The Nitrosyl chloride can further dissociate into Nitric oxide and chlorine, as shown below:.
This indicates that the Aqua Regia solution also has nitric oxide, in addition to nitrosyl chloride and chlorine. Step three: The gold alloy is put into the Aqua Regia solution, and this causes only the gold to dissolve in the solution. The chemical equation for this step is shown below:.The quality of gold is measured by a rating known as carats. This is why gold items are stamped with 10k, 14k, 18k, etc. Gold with a higher carat rating has more gold content than gold with a lower carat rating.
For example, 14k gold is roughly 58 percent gold content, 18k gold is roughly 75 percent gold content and 24k gold is pure gold. The remaining percentage of gold that is not pure is made up of copper and other metals that were fused into the gold when it was in a molten state. It is possible to use a chemical process to remove these excess materials so that your gold is more refined.
Using this process, you can turn lower quality gold into pure 24k gold. Follow these steps to learn how to chemically refine gold to its pure state. Take proper safety precautions. You will be working with volatile chemicals during the process of refining the gold. Aqua regia, in particular, is a dangerous chemical that is capable of burning through human flesh.
Thick rubber gloves, a rubber apron and safety goggles should be worn at all times. Use a face mask if at all possible, similar to the ones worn by asbestos removal professionals. This will help protect you from any toxic fumes released by the chemicals. Place your gold in the bottom of a chemistry beaker. If you have enough gold that it is stacked more than a couple of inches in the bottom of the beaker, you may want to consider breaking it up into multiple portions rather than refining it all at the same time.
Slowly pour the aqua regia into the beaker.
How to Refine Gold: 2 Major Techniques of Gold Refining Process
Fill the beaker halfway with this chemical. Pour very slowly, being extra careful not to splash any of the chemical. Aqua regia is a volatile chemical that will burn through your clothing, skin and muscle tissue upon contact. Use the chemicals in a well-ventilated area to reduce the amount of toxic fumes in the air. Fill the remaining half of the beaker with sodium meta bisulphate.
Again, pour the chemical slowly, being careful not to splash or to overfill the container. Allow the mixture to sit for approximately one hour per ounce of gold being refined. The combination of aqua regia and sodium meta bisulphate will burn away any copper or other metals that are locked into the gold, leaving only pure 24k gold behind.
Recover the gold from the chemical solution. Carefully drain the chemicals from the beaker into a glass jar, where they can be stored for future use. Leave the gold in the bottom of the chemistry beaker until the remaining chemicals have evaporated.
Rinse the gold thoroughly with water and allow it to air dry. You have now chemically refined your gold to its pure 24k state. Do not use this process on jewelry expecting to have 24k gold jewelry at the end. You will have 24k raw gold rather than jewelry.Have you ever seen advertisements for how you can repurpose your old gold jewelry? Have you ever wondered what happens to your jewelry after you sell it? Certainly, you get paid in most cash-for-gold operations, but what happens to the gold itself?
What is it good for and why are people willing to pay for it in the first place? Because of this, a refiner must assess the material to calculate what percentage pure gold it is. To make it harder and stronger, manufacturers use other metals such as platinum, palladium, silver or copper.
The resulting gold alloy can be used to make all kind of things such as coins and jewelry. This means that when you sell your gold jewelry, a refiner has to determine how much of it is pure gold and how much is other alloyed metals. We use a unit of measurement called a karat to denote how much gold is in an alloy. A karat is one part out of By this measurement, then, pure gold would be 24 karats.
An karat gold ring would be 18 parts pure gold and six parts another metal alloy. Some jewelry goes one step further than this.
This jewelry consists of a thin layer of gold on top of another metal. In this case, the karat number of the gold refers just to the gold layer of plating and not the metal underneath. The most commonly used and one of the most accurate methods for refining gold is the fire assay method. This is an industry-standard procedure that, while reliable, is very involved and requires many steps. The process is worth the time and effort it takes, however, because it has been proven to be 20 times more accurate than any other method.
Even though this is the most used process for assessing gold, it can be time-consuming. The process needs to be precise, and there is a lot of room for something to go wrong and for the calculations to be inaccurate. Because of this, the process can only be relied upon if highly skilled workers carry it out meticulously. The same steps would also apply to things like gold coins or other things that are made mostly or entirely of gold.
Whatever the item in question is, the process begins when you decide you no longer want or need it and opt to sell it.
Perhaps you sold your gold directly to a refiner, in which case this step is skipped. If you sold your gold to a pawn shop or other place, however, the pawn shop may send your gold to a refinery so that it can be tested and refined. If the purpose is only to test the purity of the gold, the following process only requires a small sample of the gold. If the purpose is to refine all of the gold, however, this will be done on a much larger scale. The refiner takes either the sample or the entire portion of gold and mixes it in a crucible with a flux soda or borax and lead or silver.
The flux lowers the melting temperature of gold, making the process somewhat easier to complete, and the lead helps to collect the pure gold from the alloy. This mixture of gold and other additives is then heated and melted at a temperature between roughly and degrees Celsius.
When the mixture reaches this temperature, it melts. The metals in the alloy separate from one another upon melting and the gold sinks to the bottom of the crucible.
Once everything has cooled down, the refiner removes the lead button and places it in a porous cup known as a cupel. The refiner will then heat this in a cupellation furnace. When the cupel is heated, the lead seeps out through the porous holes in the cupel, leaving behind just the gold in a bead-like shape.The processes used to refine gold are many centuries old.
The two most common methods of refining gold are refining with flame and the use of chemicals. There are actually a few different methods of refining gold. Depending upon the quantity of gold you are working with and the desired level of purity, the two most common methods for refining gold are the use of high temperature flame and the use of chemicals to refine the gold.
Refining with flame is one of the oldest methods of refining metals. Mentioned even in the bible, refining by fire is the preferable method for larger quantities of gold. In ancient times, this form of refining involved a craftsman sitting next to a hot fire with molten gold in a crucible being stirred and skimmed to remove the impurities or dross that rose to the top of the molten metal.
With flames reaching temperatures in excess of degrees Celsius, this job was definitely a dangerous occupation for the gold refiner. The tradition remains largely untouched today with the exception of a few advancements in safety and precision. The second method of refining gold involves the use of chemicals. Strong acids are used to dissolve the impurities in the gold ore and afterwards, are neutralized and washed away, taking the impurities with them. The resulting product is a muddy substance that is almost pure gold This muddy substance is dried until it is a powdered residue and then heated with a torch or other source of heat to melt the gold powder into useable gold.
The acids used for this process are Nitric acid and Hydrochloric acid. Read more common gold questions. All rights reserved. Common gold questions. How to refine gold. How does gold get its name? How is gold mined? How many grams in an ounce of gold? How much gold is found in the human body?
How much gold is there in an Olympic gold medal? How much gold is gold worth? What family does the element gold belong to? What gold detectors actually work finding gold? What happened during the Klondike gold rush? What is gold used for? What is the boiling point of gold? What is the Latin word for gold?
What year was gold discovered in California? When did the Gold Rush end? When did the Gold Standard end? Where is gold found in the world?Workers add borax and soda ash to the molten metal, which separates the pure gold from other precious and less precious metals.
A sample is then taken to a lab for tests, or assays, that measure the gold content. In most cases, the gold is Workers cast the gold produced during refining into bars.
What happens next depends on how the gold will be used. Pure gold is generally too soft for most practical applications, so other metals are nearly always added to it. When gold is combined in this way, it forms an alloy. Scientists and goldsmiths often use colors to designate the various gold alloys that are possible. For example, white gold is made by combining gold with nickel, silver or palladium. Red or pink gold is an alloy of gold and copper.
And blue gold is the result of mixing gold with iron. A higher karatage indicates a higher proportion of gold in the sample. So, karat gold is percent gold, while karat gold has exactly half as much. The common karatages are shown in the accompanying sidebar. Interestingly, different cultures prefer different karatages. For example, the people of India are partial to karat gold, while Europeans prefer karat gold.
In the United States, karat gold, which offers a balance between gold content, hardness and affordability, is by far the most popular [source: World Gold Council: Jewelry Inspirations ].
The Art and Science of Refining Gold at Home
In the next section, we'll examine the other uses of gold. What Are Isotopes? Prev NEXT. Refining Gold. One result of refining: the white gold wedding rings made for Jennifer Aniston and Brad Pitt when the two married in These rings look like they may have a rhodium plating.
Many people don't like the look of white gold without the plating. Related What Are Isotopes?Gold usually exists in nature in combination with other rocks and minerals. Some of these, such as silver and copper, may also be precious or semi-precious, but a variety of base metals are usually also present. Though several different techniques exist, any process used to separate metal from impurities or unwanted material is called refining.
In addition to the refining of newly mined gold, mints and other facilities also recycle gold scrap, including jewelry, dental filings and metal found in consumer electronics, by removing impurities. If a large amount of base metals metals are present, the first step is to use a crucible to heat the metals to their melting points.
Because gold melts at degrees C, this is not generally a practical process for most amateurs. When the material is melted, borax or soda ash is stirred into the crucible to bind with the base metals. The liquid is poured into a mold, where the larger impurities collect on the top as slag. The more dense gold sinks to the bottom. When the mold has cooled, the gold can be broken off from the slag and remelted.
How Gold Works
Refining jewelry or scrap gold that has already been refined from ore, but is in a less than pure alloy can be done at home. First collect old rings, necklaces, earrings, dental fillings or anything else made of gold that's no longer wanted in its current form. Acid bath. Gold can be separated out of an alloy by soaking in a bath of nitric acid and hydrochloric acid.
Commercial refining acid products are available. Typically, the acid bath must be left to soak for anywhere between 1 to 24 hours. Neutralize acid. The gold that is lifted out of the alloy will be suspended in the acid and needs to be separated from the acid. But before that can be done, the acid must be neutralized by adding a mixture of boiling water and uric acid, a less caustic acid that will raise the pH of the acid bath.
Add to the mix a solution of borax and water, which will precipitate the gold out of solution over a period of several minutes.