A: Borax acts as a flux when used with gold. It helps to lower the melting point of impurities present in the gold, such as oxides and other non - gold materials. This allows the impurities to separate from the gold more easily during the melting process, floating to the surface and forming a slag, which can then be removed. As a result, borax helps to purify the gold, improving its quality and making it easier to work with for various applications like casting or refining.