To describe the leaching, a simple mass balance is set up around the minerals calcium and magnesium. One assumption is that it is a batch process with no ingoing or outgoing process streams. Thus, only the chemical reaction is considered. Furthermore, no volume change occurs during leaching, so the mass balance can be converted into a concentration balance. The amount of material used in the batch process at the beginning is described in the constant 𝐶 ∞,𝑖 :