Crystals like jewels
Tartaric acid, dissolved in water with pH-indicating crystal violet, forms these beautiful images as crystals grow out of a supersaturated aqueous solution generated by evaporation of water. Originally yellow in the low-pH aqueous environment, the crystal violet changes colors as it becomes embedded in the crystals. The growth process can be watched live under the microscope and demonstrates complex phenomena of crystal formation such as nucleation, diffusion-limited growth, and formation of grain boundaries.
Microphoto of a tartaric acid crystallized from a supersaturated solution with crystal violet dye added. Image corresponds to ca. 1.3 mm by 1 mm field of view.
By Bernhard W. Adams (XSD, Argonne National Laboratory)