Soda, Ammonia Leblanc

The Leblanc process was replaced by the ammonia soda (Solvay - 1860 ) process, in which sodium chloride brine is treated with ammonia and carbon dioxide to produce sodium bicarbonate and ammonium chloride. Sodium carbonate is obtained from the bicarbonate by heating. Ammonium chloride treated with lime gives calcium chloride and ammonia. The chlorine in the original salt becomes calcium chloride that is used for melting snow and ice. The ammonia is reused in the process (99.9% recovery). 

Ammonia-soda Also called the Solvay process. A process for making sodium carbonate. The basic process was invented and partially developed in the first half of the 19th century by several workers, but the key invention was made by E. Solvay in Belgium in 1861. The first plant was built at Couillet, Belgium, in 1864 and thereafter the process became accepted worldwide, displacing the Leblanc process. The raw materials are limestone and salt calcium chloride is a waste product. The overall reaction is ... 

The black product was extracted with water and the sodium carbonate in it was recovered by concentration and crystallization. The residue, chiefly calcium sulfide, known as galigu, was dumped on land and created an environmental nuisance for many years because it never hardened. The process was invented by N. Leblanc in France in 1789, in response to a competition organized by the French Academy of Sciences. Operation of the first factory was delayed for several years because of the French Revolution. The process was operated widely until it was progressively superseded by the Ammonia-soda process in 1872. But it was still in use in Bolton, UK, until 1938, and the last plant in Europe closed in 1992. See also Black ash. 

In 1864 Ernest Solvay, a Belgian chemist, invented his ammonia-soda process. A few years later the soda ash price was reduced one third. The Solvay process had completely replaced the LeBlanc method by 1915. The Solvay method is still very popular worldwide. However, in this country large deposits of natural trona ore were found in the 1940s in Green River, Wyoming. In the last few years there has been a tremendous conversion from synthetic to natural soda ash. The first and last Solvay plant in the U.S. closed in 1986 (a large Allied Chemical plant in Solvay, NY). Trona ore is found about 500 m below the surface. It is called sodium sesquicarbonate... 

The LeBlanc process was the principal method of producing soda ash until 1860 when the Belgian Ernest Solvay (1838-1922) developed the process that bears his name. The Solvay process, sometimes called the ammonia method of soda production, utilized ammonia, NH3, carbon dioxide, and salt to produce sodium bicarbonate (baking soda), NaHCOj. Sodium bicarbonate was then heated to give soda ash. The series of reactions representing the Solvay process are... 

W. P. Bloxam does not recommend the preparation of this salt by passing hydrogen sulphide into an alcoholic soln. of ammonia because a complex salt, (NH S.wNHiS, is obtained, and the crystals contain alcohol. R. Laming made an aq. soln. of ammonium hydrosulphide by heating ammonium carbonate or gas liquor with sodium sulphide P. Spence, by heating the tank waste from the Leblanc soda process or gas lime with ammonium salts in a stream of steam and J. J. Berzelius recommended subliming a mixture of ammonium chloride and potassium sulphide—not in excess. 

E. D.onath prepared a cone. aq. soln. by distilling ammonium chloride with a hot soln. of sodium sulphide until half the liquid has passed to the receiver. E. W. Parnell and J. Simpson patented a process for making ammonium sulphide by heating the mixed residues of the Leblanc and ammonia-soda processes they also used calcium or barium sulphide instead of the Leblanc residue. Ammonium carbonate with calcium or barium sulphide can also be used (NH COj-l-BaS =BaC03-t-(NH4)2S. According to J. Habermann, ammonium sulphide free from arsenic can be obtained only by using materials free from that element. 

In 1864, Ernest Solvay, a Belgian chemist, invented his ammonia-soda process (Fig. 1), which has replaced the LeBlanc process. 

By that time the Leblanc process was facing competition from the newer Solvay (ammonia soda) alkali. The dominance of Leblanc soda was extended by improvements, most notably the Deacon process (1868), which converted the wasteful and harmful hydrochloric acid gases into chlorine, and the... 

Mond and Co. By 1890, the Leblanc process was entering the final stages of its death struggle with the Solvay process, and the electrolytic process was about to help Solvay finish off Leblanc before turning its attention to an ultimately similar fate for ammonia soda. 

The following year, in 1807, the big glass manufacturer St Gobain started to use Leblanc soda for mirror glass. The method spread over the European continent and reached a production maximum of 545 000 tonnes in 1880. Then the Solvay method, the ammonia-soda process, gradually took over. 

---