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Instructions
Ensure the chemical product resulting from your purification procedure is completely free of any residual solvent that might have been used. If necessary, you can allow the product to sit at room temperature for several days to allow solvent to evaporate, or use gentle heating to speed up the process, assuming the product is stable on heating.
Weigh the dry product and record the weight. Remember to remove any extra material, such as filter paper that might have been used to catch the product during purification; alternately, subtract that weight of that material. For example, you might have performed the purification by recrystallization of a chemical in a school lab and obtained a dry mass of 2.86 g.
Divide the dry mass of the purified product that you just determined by the mass of the chemical you started with prior to the purification process. Note that the mass of the starting material must be in the same units as the purified product. In the case of the example, if you started with 5.00 g of your chemical before the recrystallization procedure, you would calculate 2.86 divided by 5.00 to obtain 0.572.
Multiply the result of your last calculation by 100. The result is your percent recovery of that chemical for the procedure. For the example, you would multiply 0.572 by 100 and report that you observed a recovery of 57.2 percent.