Synthesis of copper pigments, malachite and verdigris: Making tempera paint

摘要

Malachite and verdigris, two copper-based pigments, are synthesized in this experiment intended for use in a general chemistry laboratory. The preparation of egg tempera paint from malachite is also described. All procedures can be done with a magnetic stir plate, standard glassware present in any first-year laboratory, and household chemicals. Yields for the synthesis of malachite are about 95% making this an ideal activity for courses emphasizing green chemistry. Typical results from students enrolled in a general chemistry course are reported. While introducing the students to the composition of artists' paints, performing this experiment provides students an opportunity to apply concepts in topics such as stoichiometry (excess reactants and yields), solubility, precipitation, and properties of emulsions. The importance of reading the experiment before coming to the laboratory is emphasized as students must come up with timesaving strategies to finish both pigment syntheses in the time allotted.