Hydrophobic colloidal silica has nano-sized primary particles and a large specific surface area, which provide desirable flow characteristics in dry powders used in tableting and capsule filling. The hydrophobic grades absorb less moisture and may offer an advantage in moisture-sensitive formulations. Hydrophobic colloidal silica is also used to thixotropically control viscosity, to thicken and stabilize emulsions, or as a suspending agent in gels and semisolid preparations. It is suspending agent, thermal stabilizer, viscosity-increasing agent.