1. The BET surface area can be used for calibration. Due the ageing processes of the material the material should be stored under comparable storage conditions when used for cross checks. The given AR range of the BET surface area displays a status quo of the IRM 100 material. Although this silica grade is considered rather stable, if stored adequately, the BET surface area will gradually decrease. It is to be expected that the average value of the material can decrease approximately up to 2 m2/g each year.
2. These tests are seldom subjected to ageing processes. The expected changes are negligible.