Crystal Growing Definitions and Tips
There are many methods for growing crystals. One of the most common is the solution method. In this process, much as in nature, a saturated solution is created and allowed to cool. Crystallization progresses from the liquid state into an ordered solid state in two steps - nucleation and growth.
Nucleation may occur at a seed crystal, that is, a small "proto-crystal" formed by precipitation out of the cooling (now supersaturated) solution. Nucleation may also begin on some particle of dust or on some imperfection in the surrounding vessel. Crystals grow by the ordered deposition of material from the liquid state to a surface of the crystal.
As in nature, crystals will only form when the correct conditions exist. This usually involves the proper "environment" and the presence of the right starting material. Here are a few things you can check to insure success in your crystal growing project.
- The chemical sample should be as pure as possible. When crystallization attempts consistently yield oils, the sample is probably not pure enough.
- The solvent material should be as pure as possible. Use distilled water instead of tap water.
- The glassware should be thoroughly clean but "used". New glassware is so smooth that there are no nucleation sites available on the exposed surfaces. If no seed crystals are forming from your cooling solution try scratching the interior surface of the flask with a glass rod. This will create tiny, sharp fragments of glass that act as sites for seed crystals to begin forming.
Liquid - A state of matter characterized by free movement of atoms or molecules among themselves but without the tendency to separate from one another as in gases.
Solid - A state of matter with a definate shape and volume in which compressed atoms or molecules occupy relatively fixed positions.
Crystal - Most solids, including metals, are characterized by an orderly arrangement of atoms or molecules (groups of atoms). This orderly pattern gives crystals their distinctive shape.
Nucleation - The beginning of crystal growth at one or more points.
Saturated Solution - A solution that has as much solid dissolved in it at a given temperature as possible.
Supersaturated Solution - A special solution that has more solid dissolved than normal. Such a solution may occur when a saturated solution cools gradually so that nucleating crystals do not form. They are extremely unstable and will precipitate with the addition of even one or two "seed" crystals or by shaking or stirring.