purgatory

to concoct pills of immortality

to condense milk (by evaporation); condensed milk

to refine; refining (e.g. oil, chemicals etc)

to polish a phrase

to toughen; to temper; to engage in physical exercise; to work out; (fig.) to develop one's skills; to train oneself

to refine with fire

to extract (ore, minerals etc); to refine; to purify; to process

(of Taoists) to practice austerities; to practice asceticism

to smelt metal