Why does Cody use Litharge? In many of the precious metal refining videos Cody (Cody's Lab) takes the sample with the precious metal and puts Litharge into it. After heating it in the furnace, while pouring it out the molten lead comes out and Cody says that the precious metal is all inside the molten lead(Later extracting it using cupellation). How does this happen?
https://www.youtube.com/watch?v=vltBwXncjCI&amp;t=369s
From 3:01
Edit: My doubt is specifically the processes involved during Litharge Smelting.(that result in the precious metal being alloyed with lead)Why is Cody confident that all of the silver has been alloyed with the lead? Why cant the silver form a separate mass? My speculation is that all the impurities except the precious metal melts, the litharge is reduced into lead, the molten lead being denser than other molten impurities sinks to the bottom ,the silver being the densest goes to the bottom to meet lead and they alloy. Is this possible?
Litharge is $\ce{PbO}$. It is probably introduced to save silver from compounds containing oxidized silver like $\ce{AgCl}$. If metallic silver powder is mixed with $\ce{AgCl}$, this compound will react with $\ce{PbO}$ according to $$\ce{2 AgCl + PbO -&gt; PbCl2 + Ag2O}$$ And $\ce{Ag2O}$ is an instable compound being easily transformed into $\ce{Ag + O2}$ at high temperature. So all metallic silver and silver from silver compounds are finally dissolved into lead, because lead dissolves metallic silver and not silver compounds. Without litharge, silver compounds like $\ce{AgCl}$ are lost.