NSCI 3022 Study Guide - Midterm Guide: Miscibility, Stopcock, Evaporation
11 Nov 2015
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Document Summary
Dissolving materials to be crystallized in a hot solvent and cooling the solvent slowly. The solubility of the dissolves material decreases as the temp decreases and therefore becoming oversaturated and crystallizes out of the solvent. When crystals are being formed, the same individual molecules will fit in a specific crystal lattice structure. The slower the crystal formation then the more pure the crystals will be. Also multiple recrystallizations results in a more pure crystal. If an impurity is less soluble at high temperatures then it can be filtered off prior to crystallization. If the impurity is more soluble than the compound of interest then cooling the solution results in the formation of pure crystals with the impurity remaining in the solution. Ideal solvent: the best solvent is a poor solvent at room temperature and a good solvent at high temperatures so that the substrate will dissolve at high temps and will recrystallize at low temps.
