Subsequent pH decrease: Magnesium hydroxide precipitates (III) into the pores and on the surface of MgO. The Mg2 þ concentration decreases rapidly, subsequently remaining at the quasi-equilibrium state. What is observed here is the apparent Mg2 þ concentration after MgO dissolves and before magnesia ions are consumed by hydroxide formation. This can be described as a transition con- centrationofMg2þ ionfluxbetweentheMgOdissolutionandthe Mg(OH)2 precipitation processes