The major sources of error in the synthesis of alum from aluminum foil include loss of product through various means, human and systematic errors, contamination, and impurities in the reactants. Sources of error depend on the exact method of synthesis.
A potential source of error is loss of product. This may occur through spillage of the reactants or products, through evaporation of a material in a container that is not enclosed, or through crystals caught in the filter.
Human error is another potential source of error. Human error includes inaccurately measuring the reactants as well as failing to transfer the entire material to a new container, leading to the loss of product. Systematic errors include a malfunctioning scale, the ice bath not being cold enough, and fingerprints on a crucible, which increases its weight and causes an error in measurement.
Contamination of the samples causes error during the synthesis of alum from aluminum foil. Contaminants may react with one of the reactants, leading to a decrease in the desired reaction. The contaminants may also stop the desired reaction from occurring entirely.
Impurities in the reactants also cause errors. Iron and silicon are common impurities found in aluminum foil, and sodium is a common impurity found in potassium aluminum sulfate dodecahydrate. Like contaminants, impurities cause a decrease in the desired reaction.