【Article overview】Glass used for various purposes all require a certain degree of chemical stability. For example, flat glass with poor chemical stability tends to absorb moisture and stick together during storage and transportation.

　　All types of glass used for various purposes are required to exhibit a certain degree of chemical stability. For example, flat glass with poor chemical stability tends to absorb moisture and stick together during storage and transportation; lenses used in optical instruments can become moldy and unusable under the influence of air and water; chemical instruments may suffer from impaired analytical results due to glass corrosion; bulb casings made of glass can become fuzzy as a result of weathering. In particular, glass products used for packaging pharmaceutical injectables—such as ampoules and saline solution bottles—must withstand prolonged contact with medicinal solutions under conditions of steam sterilization and various climatic environments. If the glass lacks adequate chemical stability, it may dissolve into the medicinal solution or even flake off in sheets (commonly referred to as "flake-off"). In mild cases, this can compromise the quality of the medicinal solution; in severe cases, it can seriously endanger the health of patients and even threaten their lives. Therefore, all glass products must meet the specified chemical stability standards. (P122) The chemical stability of glass is a highly complex physicochemical phenomenon. Generally, most glass products only need to demonstrate good resistance to atmospheric conditions and aqueous solutions. Packaging bottles for liquid pharmaceuticals or chemical reagents should have their glass compositions carefully selected based on the properties of the liquid being contained. Medical ampoules often require particularly high-quality packaging materials due to the complex nature of the injected drug solutions they hold; thus, "neutral glass" is typically used. (P128)

　　§7-4 Several Special Erosion Cases

　　I. Glass “delamination”

　　Alkali-resistant delamination is an important product inspection standard for glass used in medical ampoules. When alkaline (pH 8–12) injectable solutions are stored in glass ampoules made of chemically unstable glass, delamination and turbidity may occur after autoclaving or prolonged storage due to the corrosive action of the solution. Injectables containing such delaminated particles can seriously harm the health of patients and even pose a threat to their lives. Therefore, ampoules that exhibit delamination are strictly prohibited for medical use.

　　The delamination inspection method generally mimics the aseptic filling and sterilization conditions used by pharmaceutical manufacturers for ampoules. Cleaned ampoule bottles are filled with 0.01 N HCl and 0.001 N NaOH, then placed in an autoclave and heated at a gauge pressure of 1.05 kg/cm² (121°C) for 30 minutes. After cooling, the ampoules are visually inspected under daylight illumination. Typically, no acid-resistant delamination should be observed, while alkali-resistant delamination must not exceed 2%; in practice, no confirmed instances of delamination should be found. (P129–130)

　　— Excerpted from “Principles of Glass Technology,” published by the Building Industry Press, 1981

　　Compiled by East China Institute of Chemical Technology, Wuhan Institute of Building Materials Industry, and Zhejiang University