Sodium silicate

From PyroGuide

Formula: Na₂SiO₃

Description: Sodium silicate, also known as water glass or liquid glass, available in liquid and solid (prill) form, is used for passive fire protection.

Hazards: Sodium silicate is corrosive and may cause health problems with over exposure. It is best to avoid eye and skin contact and vapour or mist inhalation.

Sources: It can be bought from online pyrotechnic stores and ceramic supply shops. It can be bought in either liquid form or a dry powder. When dry it is mixed with water and a small amount is placed around pass fire holes and exhaust holes (see hummer).

Synthesis: Sodium silicate can be made by reacting elemental silicon with Sodium hydroxide.

Si + 2NaOH + H₂O → 2H₂ + Na₂SiO₃

If using powdered silicon, add in small portions, as it generate large amounts of heat and hydrogen. If a large amount of powdered silicon is added to concentrated Sodium hydroxide, the reaction will auto-ignite. Please be cautious.

-OR-

Sodium silicate can be made by reacting silicon dioxide with Sodium hydroxide.

SiO₂ + 2NaOH → H₂O + Na₂SiO₃

Silicon dioxide is available as silica gel, (clean) sand or glass. If using silica gel the above reaction can be carried out in solution. However, if sand or glass is being used, the reaction must be done using molten Sodium hydroxide instead. This is not terribly difficult, as Sodium hydroxide melts at 318^oC, which can be reached on a stove. Do not attempt the molten reaction in a glass container!