- Is a method in place to determine the solvent composition?
- Is there a method in place to determine the ratio of volatile solvent to non-volatile residue?
- Is there provision to initiate crystal formation? (seeding)
- Is there a provision for managed crystal growth?
- Is there provision for crystal size assessment?
- Is there a study of crystal aging(ripening)? Does the purity change depending on aging?
- Is there an IPC (in-process control -- CJ) to verify that the crystallization is complete and the correct quantity of residual product is left?
Crystal aging/ripening is something that can be an unpleasant surprise. You have to prepare yourself for the potentiality of leaving a tray of nice white/yellow crystals and coming back to a (figuratively) hot brown mess. Of course, Kilomentor's talking about something a lot less dramatic than that, I'm sure.
As a relatively young chemist, the one thing that I was surprised to learn was the density of seeding. I think we're all used to the concept of just a pinch of seed crystal from school. I was surprised to learn that seed crystals may need to be added in a much higher amount on larger scale reactions; 10% of total mass (or higher) may be necessary to induce appropriate levels of crystallization.