REACTIONS BETWEEN WATER AND LEAD CRYSTAL GLASS (24-PERCENT PBO)

The rates of removal of K, Na, Pb and Si from a commercially available lend crystal glass (24% PbO) in static deionised water under varied e xperimental conditions, short times (1/2-6 h) at temperatures in the r ange 50-95 degrees C and for long times (1-300 days) at 22.0+/-2.0 deg rees C are reported. The attack of glass by water can be described in terms of leaching of network modified cations and the uniform dissolut ion of network formers. The overall effect of water depends on the rat es at which both reactions proceed under the specified conditions of a ttack. With increasing time of attack three different stages could be distinguished. The initial parabolic stage through which the leaching of glass modifiers proceeds at a rate significantly higher than that o f dissolution of Si resulting in the increase of thickness of the leac hed layer The intermediate nonparabolic stage within which the two rea ctions proceed at equal rates giving rise to a leached layer of consta nt thickness. The final stage includes the disruption of the leached l ayer and exposing a nearly new unattacked surface to water. This seque nce of reactions is expected to be repeated with further increase of t ime of attack. The final stage is induced by the substantial increase of pH. The three stages could be observed by continuing the attack for a long time, e.g. 300 days. For times up to 6 h at temperatures up to 95 degrees C the attack remains in the initial stage.