What is "leblanc process"

The Leblanc process was an early industrial process for the production of soda ash ( sodium carbonate) used throughout the 19th century, named after its inventor, Nicolas Leblanc. It involved two stages: production of sodium sulfate from sodium chloride, followed by reaction of the sodium sulfate with coal and calcium carbonate to produce sodium carbonate. The process gradually became obsolete after the development of the Solvay process.