This paper reports studies of the rates of dissolution of natural Brucite, optical grade , and commercial in aqueous solutions. Natural Brucite dissolves by means of a surface reaction requiring protons, and while some protonated ions accelerate the dissolution no inhibitors were found. Dissolution of less perfect is normally diffusion limited; several substances which reduced the rate of dissolution of such were found. first reacts with water to form an layer and the rate is controlled by dissolution of the .