When gold is mined from the earth’s crust it is guaranteed to have impurities. Many people think that smelting and melting are interchangeable terms, but they are slightly different. Gold melting is the process of turning solid gold into liquid, but gold smelting is the process of removing the impurities from the gold by using pressure, heat and chemicals.
The smelting process has been around for thousands of years dating back to ancient civilizations. Although they conducted the process slightly different, the concept was practically the same. Gold ore was dug from the ground, crushed with tools, washed with water and finally smelted in earthen kilns. Technological advances have given us the ability to conduct this process with more accuracy and in less time.
Processing the gold ore is the first step in the smelting process that is used today. When gold is extracted from the ground, it will always contain impurities. Many times there is crude matter holding the gold together. One of the first steps in smelting calls for the extraction of the gold minerals from the ore. The gold ore is pulverized into fine particles by using pressure. The gold is then heated over 1064 degrees Celsius in a furnace to burn off most of the impurities. At this point, there are still other metals mixed within the gold.
Impurity and Chemical Removal
Mercury and iron are often used to extract pure gold from the gold ore in a process called amalgamation and distillation. Mercury is in liquid form at room temperature and acts as a great solvent for other metals. Mercury and potassium cyanide help the pure gold coagulate into nuggets and separate from any other material. The Merrill-Crowe and Elecrowinning processes call for mercury, but inhaling mercury fumes is toxic to the human body. Before conducting the next step in the smelting process, mercury and other chemicals must be extracted to keep smelters safe from harm. It is also crucial that any iron is extracted before smelting because iron can corrode smelting pots and increase smelting costs.
Melting and Refining
Once the gold is in its purest form, the melting process can begin. This process is pretty straightforward as the gold is put into a furnace and melted into its liquid form. While in its liquid form, the pure gold can be formed into ingots of many sizes. Finished gold is used for a number of applications. It can be used for jewelry, wires, electronics components, and more.
Refining is done after the smelting process depending on the type of application that the gold will be needed for. There are a few refining methods that can be utilized, but the best process for refining gold to its purest form is called the Wohlwill Process. After the Wohlwill Method is used, the gold ingot is 99.999% pure gold and refined enough to sell on the market.
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