Electron microscope investigation of the thermal aging of barium sulphate precipitates.

Barium sulphate precipitates, formed by four different analytical methods, dried and ignited at different temperatures, have been examined with an electron microscope. The study of the dissolution of precipitates has been found useful for the investigation of thermal aging. On heating the precipitates, diffusion, which takes place at temperatures depending on structure, permits structural changes such as reordering to take place. Consequently, the structure of the ignited precipitates approaches the ideal arrangement.