Model for Collection of Precious Metals in Fire Assaying

Fire assaying is the method in which the amount of precious metal in a sample is determined. This is done in several steps:

1. Mixing the weighed sample with various chemicals to make the sample melt at a relatively low temperature.
2. Heating the sample and chemicals in a furnace to form a slag that is easily removed from the lead and a lead button that contains the precious metal.
3. Removing the slag from the lead button.
4. Heating the lead button in a bone ash cupel so the lead is removed from the precious metals, leaving the precious metals in a small bead (doré) at the bottom of the cupel.
5. Weighing the doré bead to determine the fraction of precious metal in the original sample.

The second step, heating the sample to gather the precious metal into the lead as it falls through the molten sample, may be roughly modeled by the same process used to clarify water.