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Some Crystal Growing Tips By Dr. Maarten Dinger In theory, every soluble pure solid compound can be crystallized to give single crystals suitable for X-ray diffraction studies, this still being by far the least ambiguous and most complete characterization method available to synthetic chemists. A few general points should be noted: - Do not disturb crystallizations! Bumping them, swirling, etc can completely mess them up. - If using solvents, make sure everything is fully dissolved. If everything wont dissolve, then these are likely to be impurities, so filter them off. - The purer the compound, the better your chance of growing single crystals. At least 75% pure or better is probably a minimum if you want your chances to be good. - Dont give up too quickly! Solvent choice is critical, and sometimes multiple solvents are needed for the molecules to pack. Just try everything and youll find that you can almost always get a crystal. Five main methods present themselves for crystallization of compounds, all are valid for organic and inorganic materials: 1. Cooling The simplest, but nonetheless very successful, method for crystal growth is the cooling of a saturated solution of the compound to be crystallized. Any solvent is fair game for this method (with the exception of water and benzene in the freezer). Simply make a saturated solution of the compound and allow it to cool, usually by placing the solution in the freezer. Also a hot solution can be slowly cooled to room temperature, although this really only works for known compounds in undergraduate laboratories. 2. Evaporation This is the most common methodolgy for crystal growth, and involves simply evaporating solvent from the solution of the compound until saturation is reached and crystals form. This method is not the best and often leads to ugly crystals since the crystals tend to grow on the surface of the vessel . Also make sure you stopper it in time or solvate loss can occur, along with crystallinity. An ext