I made PbC2O4 from Pb(OAc)2 and oxalic acid. The PbC2O4 is originally powdery so I attempted to recrystallise from nitric acid. I can't see anything
dissolving but after cooling, its suspension clear up sooner than the untreated powder. After filtering and drying, the powder do look sparkling so I
suspect the surface molecules rearranged to become more regular.