Oscillations in the dissolution kinetics of silicate glass in tris-buffered aqueous media

Abstract The dissolution of soda-lime glass in aqueous media was monitored as a function of time at 90°C. The introduction of the cationic buffer, tris (abbreviated name for tris[hydroxymethyl] aminomethane or H 2 NC[Ch 2 OH 3 ), in order to maintain a pH value of 8.1 resulted in the formation of a surface layer which caused a decrease in the extent of glass dissolution relative to that observed in tris-free media. This surface layer exhibited periodic cracking, which was correlated with sharp ‘spikes’ when the concentration of the leachates was monitored as a function of time. The presence of Mg in the tris-based leachants resulted in reduced ‘spike’ frequency. On the other hand, the use of the anionic buffer, CAPS (abbreviated name for 3-(cyclohexylamino)-1-propanesulfonic acid or C 6 H 11 NH[CH 2 ] 2 ] 3 SO 3 H), to maintain a pH level of 9.5 was not observed to cause oscillations associated with surface passivation and cracking. Likewise, such oscillations were not observed in solutions buffered at pH 8.1 using sodium borate instead of tris.