Sodium metasilicate, Na₂SiO₃, can be synthesized with various degrees of hydration. This very alkaline substance is formed by combining and melting sodium carbonate with silicon dioxide,

Na₂CO₃ + SiO₂ ' Na₂SiO₃ + CO₂'

Sodium metasilicate has hundreds of uses, many of them related to its sealant properties. Although stable in alkaline and neutral environments, it reacts with acids to produce silica gel.

With the loss of a little water, sodium metasilicate becomes an excellent cement or binding agent, especially for higher-temperature applications, or applications involving exposure to water or acids.

One principal use of sodium metasilicate is in the pulp and paper industry. It is used in sizing and coating paper. It is also used, coupled with hydrogen peroxide, in the cellulose bleaching process, in which it acts as a buffer and stabilizing agent.

Due to a combination of excellent properties, including good emulsifying and suspension properties, along with reserve alkalinity, sodium metasilicate is finding uses in soaps and detergents, including those for automatic dish-washing use.

Elevated temperature is the key to sodium metasilicate's usefulness in automotive applications.

The U.S. government CARS program utilizes sodium metasilicate to destroy clunker automobiles. A concentrated solution is used to replace all of a car's motor oil. The car is started, and in just minutes, the heat has become sufficient to decompose the chemical, which causes the engine to seize up irreparably. The temperature required is in the 210-degree Fahrenheit and above range.

The same sodium silicate can be used to repair engines, as well. Head gasket leaks can be repaired by putting some sodium metasilicate in the coolant water. The water circulates, and some passes through the hole in the gasket. The gasket's elevated temperature changes the sodium metasilicate at the metal's surface, producing a film that seals the leak.

Sodium metasilicate is also used to make minor repairs to mufflers.

Historically, eggs have been preserved by immersion in a sodium silicate solution. This solution seals eggs, thus preserving them from bacteria, which leads to spoilage. The coating preserves eggs for a number of months.

During the twentieth century, chemical "gardens" containing various transition metal ions and sodium metasilicate were kept in homes for entertainment and decorative purposes. The metasilicate formed colorful "stalagmites" by reacting with and precipitating the metal ions. The gardens have been likened to moonscapes.