All pH-oscillators reported to date function only under open (flow reactor) conditions. We describe an approach to generating pH-oscillations in a closed system by starting from an open system pH-oscillator, finding semibatch conditions under which it oscillates with an inflow of a single reactant to an otherwise closed reactor containing the remaining components, and replacing this inflow with a layer of silica gel impregnated with the key reactant. We present data showing the successful application of this technique to the BrO(3)(-) -Mn(2+) -SO(3)(2-) IO(3)(-) -Fe(CN)(6)(4-) -SO(3)(2-), and BrO(3)(-) -Fe(CN)(6)(4-) -SO(3)(2-) systems. In all three cases, sulfite ion is the species that is replenished via dissolution from the gel layer.