INTERACTION BETWEEN LEAD CRYSTAL GLASS (24-PERCENT PBO) AND ACETIC-ACID

On commercially available lead crystal glass tumblers (24 % PbO), the interaction between their bulk and grain forms and aqueous solutions o f various concentrations of acetic acid at different temperatures (22 to 95 degrees C), and for different times (30 min to 300 d) was studie d. The extent of interaction was evaluated by determining the concentr ations of K+, Na+, Pb2+ and Si4+ ions extracted by acetic acid, the ch ange in the pH value of aqueous acetic acid solutions and the weight l oss of glass grains. The results showed that: a) Pb2+ was released fro m the glass studied under the standard testing conditions in concentra tions that were smaller than those specified in the various standard s pecifications. b) The extraction of the different cations was signific antly affected by the form of the test sample; glass grains were more reactive than the bulk form. c) Extraction of modifier cations, K+, Na + and Pb2+, during short times of attack, up to 6 h at temperatures up to 95 degrees C or during long-time attack up to 20 d at 22 degrees C , could be represented by a straight-line relationship when plotted ag ainst t(1/2). Deviation was observed for times longer than 20 d but th e straight-line relationship could be restored by plotting the extract ion data against t. Such behaviour indicates that the leached layer be came sufficiently thick after 20 d, so that the leaching and etching r eactions proceeded at equal rates. d) The dissolution of glass increas ed with increasing temperature of attack up to 95 degrees C, but the m echanism of attack remained essentially of the leaching type. e) The e xtraction of K+, Na+, Pb2+ and Si4+ ions was affected by changing the concentration of acetic acid, which was correlated with the correspond ing change in its pH value. f) The quantities of Pb2+ ions released by 4% acetic acid solution were several orders of magnitude greater than that released by 40% ethyl alcohol solution indicating that the stand ard 4% acetic acid test solution is quite suitable for Pb2+ release sa fety.