Castner–Kellner process

Castner–Kellner process

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[2] Karl Kellner in the 1890s.[3]


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 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 cathode (M), and an iron anode (D). Note that the mercury electrode is shared 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.[4]

The reaction at anode (A) is:

2Cl → Cl2 + 2e

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

2Na+ + 2e → 2Na

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 As the process commences some sodium hydroxide solution is withdrawn from center cell as output product and is replaced with water.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.


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. Hamilton Castner solved the mixing problem with the invention of the mercury cell and was granted a U.S. patent in 1892. Austrian chemist, Karl 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 Ontario Minamata disease. 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]


  1. ^ Pauling, Linus; General Chemistry 1970 ed. pp. 539–541 Dover publishing
  2. ^ Trinder, Barrie Stuart; Stratton, Michael (2000). Twentieth century industrial archaeology. London: E&FN Spon. pp. 80–81. ISBN 0-419-24680-0. 
  3. ^ Salt Manufacturers' Association: Salt and the Chemical Revolution
  4. ^ Newell, Lyman C.; Descriptive Chemistry p. 291; D. C. Heath and company, 1903
  5. ^ Chemistry Chronicles
  6. ^ Chlorine Plants: Major, Overlooked Source of Mercury Pollution, Oceana
  7. ^ WCC Submission to United Nations Environment Program on Reduction of Mercury in the Chlor-alkali sector

External links

Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Castner-Kellner process — 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,Pauling, Linus; General Chemistry 1970 ed. pp. 539 541 Dover… …   Wikipedia

  • Castner , Hamilton Young — (1858–1898) American chemist Born in New York City, Castner studied at Brooklyn Polytechnic and at Columbia University, New York. He started as a chemical consultant in 1879 and moved to Britain in 1886 when he failed to gain any backing in… …   Scientists

  • Hamilton Castner — Infobox Scientist name = Hamilton Young Castner birth date = birth date|1858|9|11|df=y birth place = Brooklyn, New York death date = death date and age|1899|10|11|1858|9|11|df=y death place = Saranac Lake, New York residence = United States,… …   Wikipedia

  • Chloralkali process — The chloralkali process is an industrial process for the electrolysis of sodium chloride solution (brine). Depending on the method several products beside hydrogen can be produced. If the products are separated, chlorine and sodium hydroxide are… …   Wikipedia

  • Mercury (element) — gold ← mercury → thallium Cd ↑ Hg ↓ Cn …   Wikipedia

  • Sodium hydroxide — Sodium hydroxide …   Wikipedia

  • Electrolysis of water — is the decomposition of water (H2O) into oxygen (O2) and hydrogen gas (H2) due to an electric current being passed through the water. Simple setup for demonstration of electrolysis of water at home. Contents …   Wikipedia

  • Downs cell — The Downs process is an electrochemical method for the commercial preparation of metallic sodium, in which molten NaCl is electrolyzed in a special apparatus called the Downs cell.[1] How it works Schematic diagram of the Downs cell …   Wikipedia

  • Alkali manufacture — This is a historical article. For current information see Sodium hydroxide#Manufacture and Chloralkali process. Alkali manufacture is the process by which an alkali is made. Typical alkalis, produced commercially, include sodium hydroxide, sodium …   Wikipedia

  • James Hargreaves (chemist) — James Hargreaves (May 1834 ndash;4 April 1915) was an English chemist and an inventor.He was born at Hoarstones, Pendle Forest, Lancashire, the eldest child of James Hargreaves, a schoolmaster at Slaithwaite near Marsden. His father moved to… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”