Silica gel is a product of a porous structure with a highly developed inner surface, having solid glassy or matte grains of oval or spherical shape, colorless to dark with black inclusions. It is highly hydrophilic, a good sorbent. There are fine-pored and coarse-pored silica gel. The size of grains depending on the type and brand of silica gel varies from 0.2 to 7 mm.