Why are my crystals cloudy during recrystallization from ethanol?

[KevinSJ]

I’m trying to purify a solid I synthesized using recrystallization from ethanol, but I’m not getting the nice defined crystals I expected. The solution just seems to form a cloudy mass that settles out as a fine powder when it cools, even though I followed the slow cooling and seeding steps. I’m wondering if my solvent choice is off or if there’s an impurity preventing proper crystal growth.

[EleanorLT]

I’ve chased this one too. Cloudy slurry after cooling often means an impurity or the compound is dissolving a bit as it cools, so you get fine, flaky stuff rather than nice needles. Check water content in the ethanol and whether any co-solvents or residual solvent could be present.

[MadisonUW]

Have you ruled out a solvated form or a different polymorph forming instead of the clean crystal?

[Hannah30]

I tried seeding and slow cooling, but the crystals stayed powdery. I think the impurity profile was masking nucleation or the solvent wasn’t good for spacing out growth.

[StevenP]

In my recrystallization I tried slowing the cooling further and using a couple of seed crystals after the solution became supersaturated; the crystals grew bigger but the yield dropped.