Sodium Carbonate

The process for obtaining sodium carbonate has changed significantly over time. It was originally produced by burning seaweeds that were rich in sodium. When the weeds were burned, sodium would be left in the ashes in the form of sodium carbonate. Although this process was effective, it could not be used to produce large volumes.

The first process that allowed production of significant amounts of sodium carbonate was a synthetic process known as the LeBlanc process, developed by the French chemist Nicolas LeBlanc (1742-1806). In this process, salt was reacted with sulfuric acid to produce sodium sulfate and hydrochloric acid. The sodium sulfate was heated in the presence of limestone and coal and the resulting mixture contained calcium sulfate and sodium carbonate, which was then extracted out.

Two significant problems with the LeBlanc process, high expense and significant pollution, inspired a Belgian chemical engineer named Ernest Solvay (1838-1922) to develop a better process for creating sodium carbonate. In the Solvay process, ammonia and carbon dioxide are used to produce sodium carbonate from salt and limestone. Initially, the ammonia and carbon dioxide are reacted with water to form the weak electrolytes ammonium hydroxide and carbonic acid. These ions react further and form sodium bicarbonate. Since the bicarbonate barely dissolves in water, it separates out from the solution. At this point, the sodium bicarbonate is filtered and converted into sodium carbonate by heating.

Synthetic production is not the only method of obtaining sodium carbonate. A significant amount is mined directly from naturally occurring sources. The largest natural sources for sodium carbonate in the United States are found around Green River, Wyoming, and in the dried-up desert Lake Searles in California.