Alkalinity is a measure of a solution's ability to neutralize acids and is usually caused by carbonates, bicarbonates, and hydroxides in the solution. The alkalinity of glass is caused when sodium and potassium oxides in the glass absorb moisture from the air, react with carbon dioxide, and leach out, damaging the glass. High alkalinity can negatively impact vaccines, parenteral products, and solutions packaged in glass by reducing stability over time. Glass alkalinity is tested by heating containers of water in an autoclave and then titrating the water to determine acid needed for neutralization.