Tubular Precipitation Structures From Alum‐Copper(II) Sulfate Crystals

Using the “chemical garden” or “silica garden” reaction, we investigate the growth dynamics of hollow tubes formed from mixed metal seed crystals. The latter crystals are composed of potassium aluminum sulfate (alum) and copper(II) sulfate. During the experiment, a single crystal is placed in a small volume of sodium silicate and monitored by a time‐lapse camera. At low concentrations of sodium silicate, tube growth is characteristic of the budding regime. For high concentrations of sodium silicate, tubes are initially directed by a single gas bubble and over long periods of time chemical balloon formation is observed. We quantify the spatial and temporal dynamics of tubular growth using procedures of image acquisition and processing. Specifically, we measure the tube radius, induction period, volume, and growth velocity. The precipitation structures are characterized by scanning electron microscopy (SEM) and x‐ray diffraction (XRD).