SILICA GEL 400-700 MESH
silica gel is used in chromatography as a stationary phase. In column chromatography, the stationary phase is most often composed of silica gel particles of 40–63 μm. Different particle sizes are used for different kinds of column chromatography as the particle size is related to surface area.
Silica particles used in chromatography have a high surface area, a requirement for good analytical retention. ... They are available for analytical columns and high-, middle- and low-pressure preparative applications.
Dosage
There's no expiration date. The gel packets can be "dried out" when they are full of moisture and reused. ... Silica gel will absorb moisture from any environment, so a sachet left out in the open will immediately start taking up water vapour.