• The Solvay process, also referred to as the ammonia- soda process, is the major industrial process for the production of soda ash ( sodium carbonate). The ammonia-soda process was developed into its modern form by Ernest Solvay during the 1860s. The ingredients for this process are readily available and inexpensive: salt brine (from inland sources or from the sea) and limestone (from mines).
The Solvay process results in soda ash (predominantly sodium carbonate (Na2CO3)) from brine (as a source ofsodium chloride (NaCl)) and fromlimestone (as a source of calcium carbonate (CaCO3)). The overall process is: 2 NaCl + CaCO3 → Na2CO3 + CaCl2The actual implementation of this global, overall reaction is intricate.  Asimplified description can be given using the four different, interacting chemicalreactions illustrated in the figure. In the first step in the process,carbon dioxide (CO2) passes through a concentrated aqueous solution of sodium chloride (NaCl) and ammonia(NH3). NaCl + CO2 + NH3 + H2O → NaHCO3 + NH4Cl
• Soda ash is used in many industrial processes, and its production is sometimes used as an indicator of economic health. The principal current uses include:• Glass making: More than half the worldwide production of soda ash is used to make glass. Bottle and window glass (Soda-lime glass) is made by melting a mixture of sodium carbonate, calcium carbonate and silica sand ( silicon dioxide (SiO2)).• Water treatment: Sodium carbonate is used to soften water (precipitates out Mg2+ and Ca2+ carbonates). This is used both industrially and domestically (in some washing powders).
• The name "soda ash" is based on the principal historical method of obtaining alkali, which was by using water to extract it from ashes. Wood fires yielded potash and the active ingredient potassium carbonate• The word "soda" (from the Middle Latin) originally referred to certain plants that grow in salt marshes; it was discovered that the ashes of these plants yielded the useful alkali "soda ash.".
• Variations in the Solvay • Variations in the Solvay process have been process have been proposed for carbon sequestration. One idea proposed to convert is to react carbon carbon dioxide dioxide, produced emissions into sodium perhaps by the carbonates, but carbon combustion of coal, to form solid carbonates sequestration by calcium (such as sodium or magnesium bicarbonate) that could carbonates appears be permanently stored, more promising . thus avoiding carbon dioxide emission into the atmosphere .
• The principal byproduct of the Solvay process is calcium chloride (CaCl2) in aqueous solution. The process has other waste and byproducts as well. Not all of the limestone that is calcined is converted to quicklime and carbon dioxide (in reaction II); the residual calcium carbonate and other components of the limestone become wastes. In addition, the salt brine used by the process is usually purified to remove magnesium and calcium ions, typically to form carbonates; otherwise, these impurities would lead to scale in the various reaction vessels and towers. These carbonates are additional waste products.