# Lead's affinity for oxygen in the cupellation refining process

My inorganic chemistry textbook1 says:

Cupellation is a process, where crude gold is taken in a small bowl called cupell and melted in the presence of air. Due to high oxygen affinity of $$\ce{Pb}$$, it is converted to $$\ce{PbO}$$ (volatile) and escapes from the system.

Now, the affinity for sulphur and lead is explained by HSAB (soft acid-soft base). But how to account for the affinity of oxygen (hard base) and lead (soft acid)?

### References

1. Guha, Sudarsan. Concise Inorganic Chemistry for JEE (Main and Advanced). 4th ed., Wiley India Pvt. Ltd., 2017.
• More important is general resistance of noble metals to oxidation. – Mithoron Dec 3 '18 at 23:06
• @Mithoron Yes that is true, but noble metals generally resist reacting with most elements, don't they? While I have looked thorough a few books about cupellation,and they all talk about lead's affinity for oxygen, and I'm not quite sure about the rationale for this. – Yusuf Hasan Dec 4 '18 at 3:12