Several studies have highlighted that nucleation reactions can occur via multi-step mechanisms with nanoscale intermediates. Whereas some nucleation pathways are well characterized and described in bulk solutions, their evolution in Single-Digit Nanoconfinement (SDN) is still unknown. The goal of this proposal is to explore the precipitation in 3 nm silica SDN of several sulfate phases XSO4 (with X= Mg, Ca, Sr, Ba) using our reliable experimental methods. To reach this goal, 3 nm nanochannels, already filled with Na2SO4 solution will be immersed in electrolyte solutions of XCl2 (with X= Mg, Ca, Sr, Ba) and characterized using Hard-ray reflectivity. The electrolyte transport in the nanochannels, especially pore clogging, will be characterized as a function of the ability of ions to form various ion pairs in solution.