Recipes were used that allowed the growth of crystals within most of the crystalline systems. The main reference was Crystals and Crystal Growing, by Holden and Singer. The crystals grown include alum (cubic), rochelle salt (orthorhombic), epsom salt (unverified), nickel sulfate (tetragonal), sodium chlorate (cubic), sodium nitrate (hexagonal), monoamonium phosphate (unverified), potassium ferricyanide (monoclinic), copper acetate monohydrate (monoclinic), and calcium copper acetate hexahydrate (tetragonal).
Growing crystals requires patience, time, and the right materials. Certain necessary materials are listed: chemicals in propper amounts, gram scales, mason jars (quart and pint sizes), fine string (this experiment used dental floss), spoons to stir materials, bunsen burner, and small pot to heat liquids in. Preferable, mason jars, spoons, and pans should be chosen that are not intended for human food use in the future. Never take chances. The chemicals can be found or ordered from chemical supply houses, pharmacies, or as in the case of this experiment campus chemistry departments.
The first step in growing crystals is to form a saturated solution. The method used in this experiment, as outlined in Holden and Singer, was to supersaturate the liquid at higher temperatures. As the liquid cooled, excess materials would crystallize along the bottom, leading to a perfectly saturated solution within days. The bulk material that comes out of solution at the bottom will be the source of a seed crystal (a small, hopefully perfectly shaped crystal that will be suspended in the solution to allow further growth to occur on its surfaces).
From this point there are two paths to grow crystals. The evaporative method is slower but forms clearer and more perfect crystals (the slower a crystal forms the clearer it will be). In this method, an uncovered jar of saturated salt solution is seeded and as the liquid evaporates, the solution becomes supersaturated and deposits excess materials on the seed crystal. A week or more may be necessary for a two centimeter crystal to form.
The supercooling method is faster, but may lead to cloudy crystals or a large number of very small crystals forming throughout the liquid. In this method, the saturated solution is heated and a small amount of extra salt is added. It is seeded after cooling to almost room temperature (to prevent the seed crystal from being disolved at the higher temperature). The cooler liquid can't hold the extra salt so it is quickly deposited onto the seed crystal. Crystals of this type can be grown overnight or at most half a week. Alum and Rochelle Salt grow particularly quickly this way.
See the GROWING APPENDIX for actual recipes.
