Calcium carbonate does get used as a base in some organic synthesis reactions. Its lack of solubility need not be a problem.

I'm wondering now if harmalol is behind the orange to pink colours of harmala citrates that I've made. The crude freebase was precipitated with ammonia around pH 10, then dissolved in BuAc, and precipitated with citric. When my lablet is up and running again for autumn I'll be sticking some of this colourful stuff through a little chroma column.

I think the colour comes from oxidation. I would also not be at all surprised to find that harmalol was light-sensitive. Therefore, anyone who really wants to get to grips with this stuff should get up to speed with inert atmospheres and work under dim red light. Does make it look rather like an acid lab, though :lol: