Silica gel (also called silica, silica gel or drying beads, etc.) is the most commonly used drying agent in aeration drying. It consists of 99% silicon dioxide (SiO2). Narrow pore silica gel has a large internal surface area of up to 850 m²/g due to its high porosity. The pore structure is not uniform. The funnel-shaped openings have a diameter of about 2 to 12.5 nm. This allows loading with water molecules in several layers (capillary condensation), which explains the very high uptake capacity of this adsorbent. Due to its extreme hydrophilicity (attraction of polar substances, such as water) and easy regeneration by raising the temperature to about 120°C, it is preferably used as a desiccant.
Especially at a relative humidity of approx. 70 %rH, silica gel shows its excellent absorption capacity. The maximum water absorption capacity is approx. 37 % of the dry weight of the fill.
Silica gel orange colorless has a weaker color change than e.g. silica gel orange-green. In addition, the color change takes place only at a higher water loading of approx. 20-25%.
Other silica gels