You can melt scrap gold at home to purify it using a few specialised tools and some common materials you can purchase at your local hardware store. Pure gold is 24 carats and has a melting point of 1060 degrees Celsius. If a piece of gold jewellery is labelled as having less than 24 carats (e.g., 14 carats), it means the jewellery piece is an alloy containing other metals in addition to gold to make it stronger. Gold dust and flakes obtained from prospecting is known as "fine" gold and it usually contains some impurities that need to be flushed out with a flux mixture. The flux also keeps the fine gold from blowing away when a blow torch is turned on it.
Protect yourself before you begin by donning heat-resistant gloves, glasses or goggles, and a respirator face mask.
Put your scrap gold in the crucible until it is completely full. A crucible used for melting gold looks similar to a bowl with no lid or top on it. Add a few pinches of sodium carbonate and a few pinches of Borax for your flux.
Turn on the torch and very slowly touch it to the gold itself in the crucible. Keep torching until all gold melts down to molten form. Use the crucible tongs, if necessary, to break up any pieces that won't dissolve.
Pour the liquid gold very slowly and carefully with the tongs into a bar-type mould.
Allow to completely cool and harden. Unscrew the two-part mould before removing the solid gold.
Don't use a ceramic crucible in this case because it could spring a leak and spew molten gold onto you.