Diffusion-controlled growth of a planar chemical garden wall before osmotic fracture

Abstract

Chemical gardens refer to a class of self-assembling structures of semi-permeable precipitates. They have been attracting significant interest due to their relevance to sub-oceanic hydrothermal vents and the origin of life. We have investigated the growth behaviour of chemical garden walls in a horizontal Hele-Shaw cell. The experiments have been conducted with pellets of either solid cobalt (II) or manganese (II) chloride contained in aqueous sodium silicate solutions. It is found that the growth of the chemical garden walls can be well described by a simple, diffusion-controlled dynamical model until their eventual osmotic fracture at a reproducible time. This provides a basis by which wall growth in more complex chemical garden systems can be characterised.