The Leblanc-Deacon process is a modification of the Leblanc process.  The Leblanc process was notoriously environmentally unfriendly, and resulted in some of the first Air and Water pollution acts.  In 1874, Henry Deacon had derived a process to reduce HCl emissions as mandated by the Alkali Act.  In this process, hydrogen chloride is oxidized by oxygen over a copper chloride catalyst, resulting in the production of chlorine.  This was widely used in the paper and textile industries as a bleaching agent, and as a result sodium carbonate was no longer the primary product of these plants, and henceforth sold at a loss.