The first patent for electrolyzing brine was granted in England in 1851 to Charles Watt. His process was not an economically feasible method for producing sodium hydroxide though because it could not prevent the chlorine that formed in the brine solution from reacting with its other constituents. American chemist and engineer, Hamilton Castner, solved the mixing problem with the invention of the mercury cell and was granted a U.S. patent in 1894.[4] Austrian chemist, Carl Kellner arrived at a similar solution at about the same time. In order to avoid a legal battle they became partners in 1895, founding the Castner-Kellner Alkali Company, which built plants employing the process throughout Europe. The mercury cell process continues in use to this day.[5] Current-day mercury cell plant operations are criticized for environmental release of mercury[6] leading in some cases to severe mercury poisoning (as occurred in Japan). Due to these concerns, mercury cell plants are being phased out, and a sustained effort is being made to reduce mercury emissions from existing plants.[7]
Process details
Castner–Kellner apparatus
The apparatus shown is divided into two types of cells separated by slate walls. The first type, shown on the right and left of the diagram, uses an electrolyte of sodium chloride solution, a graphiteanode (A), and a mercurycathode (M). The other type of cell, shown in the center of the diagram, uses an electrolyte of sodium hydroxide solution, a mercury anode (M), and an iron cathode (D). The mercury electrode is common between the two cells. This is achieved by having the walls separating the cells dip below the level of the electrolytes but still allow the mercury to flow beneath them.[8]
The reaction at anode (A) is:
2 Cl− → Cl2 + 2 e−
The chlorine gas that results vents at the top of the outside cells where it is collected as a byproduct of the process. The reaction at the mercury cathode in the outer cells is
Na+ + e− → Na (amalgam)
The sodium metal formed by this reaction dissolves in the mercury to form an amalgam. The mercury conducts the current from the outside cells to the center cell. In addition, a rocking mechanism (B shown by fulcrum on the left and rotating eccentric on the right) agitates the mercury to transport the dissolved sodium metal from the outside cells to the center cell.
The anode reaction in the center cell takes place at the interface between the mercury and the sodium hydroxide solution.
2Na (amalgam) → 2Na+ + 2e−
Finally at the iron cathode (D) of the center cell the reaction is
2H2O + 2e− → 2OH− + H2
The net effect is that the concentration of sodium chloride in the outside cells decreases and the concentration of sodium hydroxide in the center cell increases. As the process continues, some sodium hydroxide solution is withdrawn from center cell as output product and is replaced with water. Sodium chloride is added to the outside cells to replace what has been electrolyzed.
^Pauling, Linus; General Chemistry 1970 ed. pp. 539–541 Dover publishing
^Trinder, Barrie Stuart; Stratton, Michael (2000). Twentieth century industrial archaeology. London: E&FN Spon. pp. 80–81. ISBN978-0-419-24680-0.
^. Salt and the Chemical Revolution. Salt Manufacturers' Association. Archived from the original on May 14, 2007.
^US 528322, Castner, H.Y., "Process of and apparatus for electrolytic decomposition of alkaline salts", issued 30 Oct 1984
^Kiefer, David M. (April 2002). "When the Industry Charged Ahead". Today's Chemist at Work. Chemistry Chronicles. American Chemical Society. 11 (3): 9.
^. Oceana. Archived from the original on 20 Jul 2011.
^(PDF). Archived from the original (PDF) on 2011-05-25.
^Newell, Lyman C.; Descriptive Chemistry p. 291; D. C. Heath and company, 1903
External links
Animation showing the mercury cell process
Producing chlorine in the chlorine-alkali industry - IUPAC
now a health issue
January 07, 2023
castner, kellner, process, method, electrolysis, aqueous, alkali, chloride, solution, usually, sodium, chloride, solution, produce, corresponding, alkali, hydroxide, invented, american, hamilton, castner, austrian, carl, kellner, 1890s, contents, history, proc. The Castner Kellner process is a method of electrolysis on an aqueous alkali chloride solution usually sodium chloride solution to produce the corresponding alkali hydroxide 1 invented by American Hamilton Castner and Austrian Carl Kellner in the 1890s 2 3 Contents 1 History 2 Process details 3 See also 4 References 5 External linksHistory EditThe first patent for electrolyzing brine was granted in England in 1851 to Charles Watt His process was not an economically feasible method for producing sodium hydroxide though because it could not prevent the chlorine that formed in the brine solution from reacting with its other constituents American chemist and engineer Hamilton Castner solved the mixing problem with the invention of the mercury cell and was granted a U S patent in 1894 4 Austrian chemist Carl Kellner arrived at a similar solution at about the same time In order to avoid a legal battle they became partners in 1895 founding the Castner Kellner Alkali Company which built plants employing the process throughout Europe The mercury cell process continues in use to this day 5 Current day mercury cell plant operations are criticized for environmental release of mercury 6 leading in some cases to severe mercury poisoning as occurred in Japan Due to these concerns mercury cell plants are being phased out and a sustained effort is being made to reduce mercury emissions from existing plants 7 Process details Edit Castner Kellner apparatus The apparatus shown is divided into two types of cells separated by slate walls The first type shown on the right and left of the diagram uses an electrolyte of sodium chloride solution a graphite anode A and a mercury cathode M The other type of cell shown in the center of the diagram uses an electrolyte of sodium hydroxide solution a mercury anode M and an iron cathode D The mercury electrode is common between the two cells This is achieved by having the walls separating the cells dip below the level of the electrolytes but still allow the mercury to flow beneath them 8 The reaction at anode A is 2 Cl Cl2 2 e The chlorine gas that results vents at the top of the outside cells where it is collected as a byproduct of the process The reaction at the mercury cathode in the outer cells is Na e Na amalgam The sodium metal formed by this reaction dissolves in the mercury to form an amalgam The mercury conducts the current from the outside cells to the center cell In addition a rocking mechanism B shown by fulcrum on the left and rotating eccentric on the right agitates the mercury to transport the dissolved sodium metal from the outside cells to the center cell The anode reaction in the center cell takes place at the interface between the mercury and the sodium hydroxide solution 2Na amalgam 2Na 2e Finally at the iron cathode D of the center cell the reaction is 2H2O 2e 2OH H2The net effect is that the concentration of sodium chloride in the outside cells decreases and the concentration of sodium hydroxide in the center cell increases As the process continues some sodium hydroxide solution is withdrawn from center cell as output product and is replaced with water Sodium chloride is added to the outside cells to replace what has been electrolyzed See also EditElectrochemical engineering Castner Medal Chloralkali processReferences Edit Pauling Linus General Chemistry 1970 ed pp 539 541 Dover publishing Trinder Barrie Stuart Stratton Michael 2000 Twentieth century industrial archaeology London E amp FN Spon pp 80 81 ISBN 978 0 419 24680 0 The Electrolysis of Brine Salt and the Chemical Revolution Salt Manufacturers Association Archived from the original on May 14 2007 US 528322 Castner H Y Process of and apparatus for electrolytic decomposition of alkaline salts issued 30 Oct 1984 Kiefer David M April 2002 When the Industry Charged Ahead Today s Chemist at Work Chemistry Chronicles American Chemical Society 11 3 9 Chlorine Plants Major Overlooked Source of Mercury Pollution Oceana Archived from the original on 20 Jul 2011 World Chlorine Council Submission on Global Mercury Partnership for the Reduction of Mercury in the Chlor alkali Sector PDF Archived from the original PDF on 2011 05 25 Newell Lyman C Descriptive Chemistry p 291 D C Heath and company 1903External links EditAnimation showing the mercury cell process Producing chlorine in the chlorine alkali industry IUPAC now a health issue Retrieved from https en wikipedia org w index php title Castner Kellner process amp oldid 1120103957, wikipedia, wiki, book, books, library,
