A propane flame is hot enough to melt pure gold. It will also melt gold alloys but the melting process does not separate gold from other elements, like silver or copper. Gold is one of the most expensive elements in the world and is well known for its use in jewelry. Old gold jewelry can be recycled by melting it down, making it available for use in other applications. There are several different methods to melt gold and these should be carried out by a professional.
Gold's Physical Properties
Gold is a metallic element that has the atomic number 79. It is a very good conductor of heat and electrical currents, which is why it is frequently used as wires on printed circuit boards. Gold has a very high melting temperature of 1,943 degrees Fahrenheit (1,062 degrees Celsius). This means that the melting of gold can only be achieved with flames that reach this temperature.
Propane is a combustible fuel that consists of three carbon atoms and eight hydrogen atoms. It is typically obtained in small cylinders, and is used for a variety of applications, including cooking and heating. The maximum flame temperature that can be obtained with propane gas is 3,595 degrees Fahrenheit (1,979 degrees Celsius). This is hot enough to heat a crucible and melt pure gold as well as gold alloys commonly used in jewelry.
Melting Gold with a Torch
Melting gold should be carried out by qualified personnel that have the necessary safety wear. The gold is placed into a crucible, which is a container that can withstand temperatures above the melting point of gold. Crucibles that are used to melt gold are usually made of graphite. The crucible is placed upon a fireproof surface and a torch is directed at the gold within the crucible. The gold should melt within a few minutes.
Melting Gold Alloys
Gold jewelry is generally not made from pure 24-karat gold, which is too soft to be durable. Gold items below 24 karat are not pure, and contain a small percentage of silver, copper or zinc. The addition of these elements changes the melting point slightly, which means a propane torch should be able to melt lower purity gold more quickly. For example 18-karat gold has a melting point of 1,700 degrees Fahrenheit (926 degrees Celsius) and 14-karat gold has a melting point of 1,615 degrees Fahrenheit (879 degrees Celsius).
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About the Author
Samuel Markings has been writing for scientific publications for more than 10 years, and has published articles in journals such as "Nature." He is an expert in solid-state physics, and during the day is a researcher at a Russell Group U.K. university.