ALKALI MANUFACTURE - AMERICAN PRACTICE The ammonia soda process, established about 187o, superseded the Le Blanc process which has never been used in America. The first American plant for the synthesis of soda ash by the am monia soda process was built in New York State during 1882.
In the ammonia soda process, salt, ammonia, and carbon dioxide are interreacted under controlled conditions of temperature and pressure.
The slightly soluble sodium bicarbonate is precipitated, collected on a filter, washed, and calcined to soda ash. The filtrate, consist ing largely of ammonium chloride in solution, is treated with lime to recover the ammonia which is recirculated to fresh brine (sodium chloride solution), so that the process may be repeated. The carbon dioxide evolved in calcining the sodium bicarbonate to soda ash is also recirculated to saturate the fresh brine. Calcium chloride is a by-product of the process. The steps in this process may be represented as follows : (I) Salt+Ammonia+Carbon Dioxide-I-Water —p Sodium Bicarbonate+Ammonium Chloride (2) Sodium Bicarbonate+Heat —3 Soda Ash+Carbon Dioxide • (3) Ammonium Chloride-I-Lime Ammonia+Calcium Chloride Caustic soda (NaOH) is produced by reacting soda ash with lime. More recently, the large demand for chlorine has led to the establishment of a large number of electrolytic plants in which salt is electrolyzed and chlorine and caustic are produced. The reactions in the electrolytic process may be indicated in a general way as follows: Sodium Chloride+Water-I-Electric Current —+ Chlo rine+Sodium Hydroxided-Hydrogen.
In 1938 approximately 5o% of our total caustic production was prepared by the electrolytic process. As a general rule, the am monia soda plants have been built in the vicinity of salt and lime stone deposits, such as those in Michigan, Ohio, New York, Vir ginia, Louisiana, and Texas. The first electrolytic plants were built near cheap sources of power and salt. More recently, a number of users of chlorine and caustic soda have built small plants at the point of use of these products. Soda ash, sodium bicarbonate, and trona are also produced from the natural alkaline lake brines of California and Washington, but the production is relatively unim portant as yet and is mainly for local consumption. It has been estimated that approximately i oo,000 tons of natural soda were produced in 1938. Sodium sulphate is also produced from natural reservoirs in California, Texas, Nevada, and Wyoming. Sodium sulphate is the only alkali imported in significant quantities, all the others being exported.
According to the review of the alkali and chlorine industries in Vol. 46, No. 2 (1939) of Chemical & Metallurgical Engineering, the major industrial uses for soda ash, caustic and chlorine were as follows: Estimated distribution in short tons of soda ash sales to the consuming industries in the United States for 1938 were: glass, 630,000; chemicals, 595,000; soap, 185,000; cleansers and modified sodas, iio,000; pulp and paper, 8o,000; water softeners, 33,000; textiles, 30,000; petroleum refining, 11,50o; exports, 5o, 000; miscellaneous, I12,500; total, 1,837,000. The estimated dis tribution in short tons of caustic soda sales to the consuming in dustries in the United States for 1938 were: rayon and cellulose film, 1S5,000; chemicals, 134,000; petroleum refining, 96,000; soap, 9 2,000 ; lye, 40,000 ; textiles, 36,000 ; pulp and paper, 3 5,000 ; vegetable oil, 17,000 ; rubber "reclaiming, I i ,000 ; exports, I oo,000 ; miscellaneous, 68,000; total, 784,000. The estimated production of chlorine in 1938 was 420,00o tons. In 1936 the chlorine pro duced was distributed among the consuming industries in the fol lowing percentages : production of chemicals, 51 % ; bleaching pulp, 3o%; sanitation, 6%; bleaching textiles, 5%; miscellaneous, 8%. According to the Census of Manufactures, U.S. Dept. of Com merce, 142,161 tons of sodium bicarbonate were produced in literature on the alkali industry may be found in the regular technical periodicals such as the J. Am. Chem. Soc.; J. Phys. Chem.; Ind. Eng. Chem.; J. Soc. Chem. Ind.; Trans. Electro chem. Soc.; Z. Elektrochem.; Z. physik. Chem.; Z. angew. Chem.; etc. The following works may also be consulted: G. Lunge, The Manufac ture of Sulphuric Acid and Alkali, vols. 2 and 3 (19o9-11) ; Thorpe's Dictionary of Applied Chemistry (revised ed. 1927) ; H. Schreib, Die Fabrikation der Soda nach dem Ammoniaksverfahren (1905) ; H. Tedesco, Studien caber den Ammoniaksoda Prozess (191o) ; H. Molitor, Die Fabrikation der Soda (1925) ; J. R. Partington, The Alkali In dustry (1925) ; Te-Pang Hou, "Manufacture of Soda," A.C.S. Mono graph Series No. 65 ; J. E. Teeple, "Industrial Development of Searles Lake Brines," A.C.S. Monograph Series No. 49 (1929) ; A. J. Alimand and H. J. T. Ellingham, The Principles of Applied Electro chemistry (end ed., 1924) ; C. L. Mantell, "Industrial Electrochem istry," Chemical Engineering Series (1931) . Consult also the Annual Reports on Alkali (Govt. pub.) (I. E. M.)