Cool it in the freezer, add HCl until pH 5 or 4. 4MMC.HCl should precipitate by then, if not then back into the freezer. Filter the precipitate and wash it with freezer cold acetone, but only few times - the paste will still have some color and if you keep washing it until white then you'll lose all precipitate while doing so. Dry the paste and then do several rounds of repeated recrystallization. In each round collect just the crystal, wash it with a little bit of freezer cold acetone and recrystallize again using fresh distilled water. In 2-3 rounds you should get pure crystals.