Silicon Dioxide

Products

Pharmacopeial grade pure silicon dioxide is available in pharmacies and drugstores. Note: In English, silicon is called silicon and silicon dioxide is called silicon dioxide.

Structure and properties

Silicon dioxide (SiO2, Mr = 60.08 g/mol) is the oxide of silicon. It exists, for example, as a fine white powder and is practically insoluble in water and in most mineral acids. This is with the exception of hydrofluoric acid (HF). It is also soluble in hot caustic soda. Silicon dioxide has a high melting point of 1710 °C. The pharmacopoeia distinguishes between different grades:

  • Highly dispersed silicon dioxide (Silica colloidalis anhydrica).
  • Highly dispersed hydrophobic silicon dioxide (Silica hydrophobica colloidalis).
  • Silicon dioxide for dental use (Silica ad usum dentalem).
  • Silicon dioxide hydrate (Silica colloidalis hydrica).

The various products differ, for example, in their behavior towards water (hydrophilic, hydrophobic), grain size (powder, granules), pH, surface size and density. Silica occurs very frequently in nature, for example in sand and quartz (e.g. rock crystal). Quartz is also a component of granite. Silicon dioxide is the most important component of glass. Furthermore, it is also found in living organisms, for example in diatoms. In crystal, silica typically exists in a network with a tetrahedral arrangement, where each oxygen atom is shared by two silicon atoms:

Effects

Silica has a wide variety of uses in pharmaceuticals including as a flow regulator, carrier, viscosity control, adsorbent, gelling agent (oleogels), disintegrant, antistatic agent, thixotropic agent, anti-clumping agent, and stabilizer.

Fields of application

  • As a pharmaceutical excipient, for example for solid, semisolid and liquid dosage forms. For example, it is contained in very many tablets, but also, for example, in capsules, gels, ointments and suppositories.
  • As a food additive (E 551), in cosmetics and personal care products.

Adverse effects

When working powdered silica, respiratory protection should be worn to prevent inhalation, which can lead to pneumonia and lung disease, among other effects.