I'm a metallurgical engineer with extensive experience in the field of metal processing and refining. When it comes to the use of borax in melting metal, there are several key reasons why it is added to the process.

First and foremost, borax acts as a flux. A flux is a substance that is used to remove impurities from a metal during the melting process. It does this by chemically reacting with the impurities, forming a slag that can be easily separated from the molten metal. This is particularly important in the refining of precious metals like gold, where purity is highly valued.

The role of a flux in metal refining is similar to that of a cleaning agent. It helps to clean the metal by removing unwanted elements that could affect the quality and properties of the final product. By using borax as a flux, the refining process can be made more efficient and the end product can be of a higher quality.

One of the primary reasons for using borax specifically is its ability to lower the melting point of the metal. When borax is added to the metal, it forms a mixture that melts at a lower temperature than the pure metal would. This is particularly beneficial when working with ores that contain gold, as it allows the gold to be extracted more easily.

The melting point of gold is quite high, at approximately 1,064 degrees Celsius (1,947 degrees Fahrenheit). By adding borax, the melting point of the entire ore can be reduced, making it easier to melt and extract the gold. This is a significant advantage, especially when dealing with large quantities of ore.

Moreover, borax is also known for its ability to stabilize the molten metal against oxidation. When metals are heated to high temperatures, they can react with oxygen in the air, forming oxides that can reduce the purity of the metal. Borax helps to prevent this by creating a protective layer around the molten metal, shielding it from the oxygen.

In addition to its role as a flux and its ability to lower the melting point, borax also has other benefits in the metal refining process. It can improve the fluidity of the molten metal, making it easier to pour and cast into molds. This can lead to a smoother and more uniform final product.

Furthermore, borax can also act as a deoxidizing agent. It can help to remove oxygen from the molten metal, which can improve the metal's ductility and overall mechanical properties. This is particularly important in the production of high-quality metals that are used in critical applications.

In summary, the addition of borax when melting metal serves several important functions. It acts as a flux to remove impurities, lowers the melting point of the metal, provides protection against oxidation, improves fluidity, and can act as a deoxidizing agent. These properties make borax a valuable component in the metal refining process, contributing to the production of high-quality metals.

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It also plays an important role during the gold refining process as a flux. In metal refining, a flux is sort of like a cleaning agent because it helps remove impurities from a sample. ... This is because using borax as the flux reduces the melting point of all the elements in a piece of ore, including gold.Aug 7, 2013read more >>