Abstract: The dissolution process of the 25Na₂O-25CaO-50P₂O₅ glass with different initial surfaces
was analyzed with the help of the surface weight loss and the morphology of the glass surface. The experiment of weight loss of the glass shows that
the dissolution process of the glass has two stages. the first stage, diffusion stage, at which the weight loss of the glass is proportional
to the square root of the dissolution time; the second stage, linear dissolution stage, at which the weight loss of the glass is in direct
proportion to the dissolution time. During the dissolution process of the glass, The etched pit forming stage and the etched pit stable stage were
observed, and these two stages agree with the two stages of the weight loss. The results also demonstrate that the initial surface of the glass has
remarkable effect on the dissolution process of the glass.

Key words: phosphate glass, controlled release, morphology