Keltham doesn't have memorized that many processes for producing chemicals at scale. He knows one bulk process for producing an akaline substance, the same way he knows a process for bulk-producing the most industrially important kind of acid. Lady Avaricia is trying to identify Golarion materials in terms of the underlying constituents of matter that Keltham is familiar with; she'd be the one charged with figuring out what 'soda ash' and 'bleaching powder' might be.
Oh, also he shouldn't take it personally if Lady Avaricia thinks he falls far below her standards or seems rude, Lady Avaricia is one of those people who can't bear to fake outward appearances and thinks that everyone and everything is terrible; it's nothing personal if she thinks it about him.
What sort of incredibly finicky processes are there for producing small amounts of very expensive things, such that substantially higher demand would exist if the cost decreased? Spellsilver itself is one of those things from Keltham's viewpoint; it's being produced in very small quantities via a finicky process that Keltham hopes Prestidigitation can smoothen and regularize, and there'd be demand for much higher quantities of spellsilver if those were available.