3 Ways to Assay Gold - wikiHow
To assay gold using fire, start by placing the gold into a heat-resistant crucible. Then, add lead oxide, sodium bicarbonate, potassium carbonate, and flour to create a flux, and heat everything to between 1,100 and 1,200 degrees Celsius. Next, pour off the top layer of molten glass, and pour the metal underneath into a mold to cool. ...