Self-organization in the flow-driven copper-cobaltous-oxalate system

We experimentally investigate the precipitate pattern formed by the gravity current arising around the inlet as a dense liquid containing copper and/or cobaltous ion is pumped into a sodium oxalate solution. A quantitative study with the systematic variation of the parameters reveals that the macroscopic structure of the precipitate depends on the rate of precipitate formation, flow rate of pumping, and the density difference between the solutions. The two general forms of precipitate observed are ring around the inlet and filaments oriented radially. Our study includes equilibrium calculations for the various systems, thermogravimetric identification of the precipitate and the characterization of microstructure for the precipitate in the two regions by scanning electron microscopy. For composites containing copper and cobaltous ions, the spatial separation of the precipitate is also investigated.
Numerical study supports the experimental findings.