What is the mexican stuff they use for making masa? That is not pickling lime, but when you add water to it turns into it. We had a thread going about it at one time that I jumped into to give some basic chemistry background. Chemically, its the same thing they use to make cement from, but rather in a food grade version.

CaO + H2O ---> CaOH2 + heat

CaO is true lime (Calcium Oxide), as opposed to pickling lime.