Sodium carbonate, also known as soda ash, is a compound with chemical formula Na2CO3. It is most commonly found as the colourless crystalline heptahydrate, though it also occurs in other forms. It effloresces in air to form the monohydrate and decomposes at 34 degrees Celsius.
Sodium carbonate is commonly produced by the Solvay Process (also known as the ammonia-soda process), which is a complex reaction between calcium carbonate (limestone) and sodium chloride (common salt) in the presence of ammonia. This is a widely used industrial process, with tens of billions of kilograms of the product manufactured each year. It can also be obtained from the ashes of seaweed and occurs in a range of minerals, such as natron (sodium carbonate decahydrate).
The compound is a vital component in many manufacturing processes. For many years it was the key ingredient in many household cleaners and washing powders, and also acts as a cotton bleaching agent. It is best to avoid prolonged exposure to the skin or eyes, however, as it is an irritant and, whilst not toxic in itself, in large doses can prove harmful. Perhaps the most common use of sodium carbonate is in the manufacture of soda lime glass, the most predominant form of glass used in windows and containers. It is thus a vitally important compound.
A further application of sodium carbonate is in electrolysis. It acts as an excellent electrical conductor, and is commonly used as a non-corrosive electrolyte. Other uses include as a cleaning agent for silver products, as a water softening agent and in the synthesis of numerous other sodium compounds. It is also used in the “sodium carbonate test” which is used to distinguish various metal ions.
Sodium carbonate can be dissolved in water to form a weak alkaline solution of pH 11.5. This solution will react with acids to release carbon dioxide. It is possible to create the hydrocarbonate form by bubbling carbon dioxide into a sodium carbonate solution.