Is Sodium Carbonate a Hydrate?

Sodium carbonate is a sodium salt of carbonic acid and typically occurs in a crystal form. There are three different types of sodium carbonate hydrates, and minor alteration of these hydrates allows for various uses in common household processes.

Hydrates and Sodium Carbonate

Sodium carbonate is also referred to as soda ash or washing soda. It is a chemical that scientists label as a "base," the opposite of an acid. Baking soda is very similar to sodium carbonate and has one additional carbon molecule, making it sodium bicarbonate. Hydrated sodium bicarbonate involves adding additional water molecules, thereby hydrating the sodium carbonate.

Sodium Carbonate Decahydrate

This is the most common type of hydrated sodium carbonate. The name indicates that there are 10 water molecules attached to the sodium carbonate. As additional water molecules bind to the carbonate, the "heavier" it becomes and more water-soluble. It also means that you will need to use larger amounts of the hydrated molecule to accomplish the same results as the non-hydrated molecule. Sodium carbonate decahydrate is commonly called "washing soda."

Sodium Carbonate Heptahydrate

Sodium carbonate heptahydrate can be derived from plant structures. It is a white powder in granulated form. According to Genghem.com, it is 45.7 percent carbonate and 54.3 percent water crystallization. The problem with this molecule is that it is only stable at high temperatures between about 90 and 95 degrees Fahrenheit.

Sodium Carbonate Monohydrate

Sodium Carbonate Monohydrate is 85 percent carbonate and 14 percent water crystallization. At higher temperatures, it separates crystals from water solutions. Unlike heptahyrdate, it is more stable and can be formed by heating water with soda ash.


There are various commercial uses for sodium carbonate. The most prominent use of sodium carbonate is its use in glass making. It is combined with sand and calcium carbonate. Glass manufacturers heat these molecules to very high temperatures, which causes them to melt together and form glass. Since sodium carbonate is a strong base, municipal pools often use it to balance the pH or the acidity of the pool. Finally, many people use it for cleaning purposes, which is how it got its name, washing soda. Additionally, the hydrated forms of sodium carbonate are used to create alkaline solutions and are used as water softeners.

About the Author

Graham Beckett is an attorney in Los Angeles who has practiced in California since 2006, providing thoughtful analysis and writing on various legal issues. Additionally, he is an avid surfer, runner, and comedy writer, writing and performing in various sketch shows throughout Los Angeles.