Question

Which do u think is the better way to produce large crystals from zinc sulfate-heating the evaporating dish until there is very little liquid left or leaving it to evaporate slowly?

Answer 1

Crystals that grow more slowly, tend to be larger. For crystals that were grown by slow cooling of the solvent: it usually improves the quality and size of the crystals, if the solution is slowly warmed up until alomst all crystals are dissolved again and than cooled dwon a second time very slowly.