Castner-Kellner process

The use of mercury for extracting precious metals by amalgamation has a long history and was extensively used by Spain in the sixteenth century when her fleet carried mercury from Almaden to Mexico and returned with silver. However, environmental concerns have resulted in falling demand and excess production capacity. It is still used in the extraction of gold and in the Castner-Kellner process for manufacturing chlorine and NaOH (p. 72), and a further major use is in the manufacture of batteries. It is also used in street lamps and AC rectifiers, while its small-scale use in thermometers, barometers and gauges of different kinds, are familiar in many laboratories. 

BMS A process for removing mercury from the effluent from the Castner-Kellner process. Chlorine is used to oxidize metallic mercury to the mercuric ion, and this is then adsorbed on activated carbon impregnated with proprietary sulfur compounds. Developed by Billingsfors Bruks, Sweden. 

The process is operated at 80 to 90°C with a slight excess of the calcium hydroxide. This was the only method used for making sodium hydroxide after the invention of the Leblanc process, and before the introduction of the Castner-Kellner process around 1890. The process is still used when the demands for chlorine and sodium hydroxide from the Castner-... 

CH2=CH2 + Cl2 + h2o = CH20H-CH2C1 + HC1 Chloroalcohols are important intermediates. Propylene chlorohydrin is made similarly and is used for making propylene oxide by hydrolysis with either calcium hydroxide or sodium hydroxide. If calcium hydroxide is used, the byproduct calcium chloride is useless and must be dumped. If sodium hydroxide is used, the byproduct sodium chloride can be recycled to the Castner-Kellner process. 

PuraSiv Hg An adsorptive process for removing mercury vapor from gaseous effluents from the Castner-Kellner process by TSA. The adsorbent is a zeolite molecular sieve containing silver. Developed by UOP... 

Chlorine gas is produced by the electrolysis of brine (sodium chloride) in Castner-Kellner cells (first operated in 1886), the main purpose of which is the production of sodium hydroxide solution. Williams (1972, p98) reports that the extent to which the Castner-Kellner process was worked in Britain depended on the ability to dispose of the chlorine. In this light the production of chlorinated organic compounds can be seen as a response to the need to use chlorine. The argument that we need to produce chlorinated organic compounds to use up chlorine was indeed put to me by manufacturers of polyvinyl chloride (PVC) at a DETR-organized seminar on the lifecycle assessment of PVC in July 2001 PVC is the only product made in sufficient quantities to use up all the chlorine produced by other processes. This suggests that if a particular use of a chemical is stopped, because there is a better (less hazardous) way of achieving that purpose, it will have knock-on effects on the availability of chemicals that are co-produced... 

Castner, Hamilton Young — (Sep. 11, 1858, Brooklyn, New York, USA - Oct. 11,1899, Saranac Lake, New York, USA) Castner studied at the Brooklyn Polytechnic Institute and at the School of Mines of Columbia University. He started as an analytical chemist, however, later he devoted himself to the design and the improvement of industrial chemical processes. He worked on the production of charcoal, and it led him to investigate the Devilles aluminum process. He discovered an efficient way to produce sodium in 1886 which made also the production of aluminum much cheaper. He could make aluminum on a substantial industrial scale at the Oldbury plant of The Aluminium Company Limited founded in England. However, - Hall and - Heroult invented their electrochemical process which could manufacture aluminum at an even lower price, and the chemical process became obsolete. Castner also started to use electricity, which became available and cheap after the invention of the dynamo by - Siemens in 1866, and elaborated the - chlor-alkali electrolysis process by using a mercury cathode. Since Karl Kellner (1851-1905) also patented an almost identical procedure, the process became known as Castner-Kellner process. Cast-... 

An interesting electrolytic process which may serve as a further example is the Castner-Kellner process for making chlorine and sodium hydroxide. If concentrated brine is electrolyzed, chlorine is formed at the anode and hydroxide ion at the cathode ... 

FIG. 14-5. The Castner-Kellner process for making chlorine and sodium hydroxide. 

Thus sodium metal is not the product of the cathode reaction, and indeed there is no need to bring sodium ion and sodium metal into the reaction at all. On the other hand, dilute sodium amalgam does not react with concentrated brine, to liberate hydrogen hence the cathode reaction in the Castner-Kellner process produces this amalgam rather than hydrogen. 

Hildebrand based his double-cup mercury cathode on the Castner-Kellner process for the industrial production of caustic soda. This process, which has been called the most elegant electrolytic process ever invented," was patented in 1894 by Hamilton Castner, an American analytical chemist. By 1902, Castner had increased its efficiency to 90 percent. The heart of the process was Castner s "rocking" mercury cell. The cell had two chambers through which mercury moved back and forth, continuously removed metallic sodium from the decomposing chamber, thus preventing the recombination of the sodium and chlorine. (24)... 

Castner-Kellner cell The cell used in the Castner-Kellner process. 

Castner-Kellner process The process of electrolysis of brine between graphite anodes and a flowing mercury cathode in a cell. 

The mineral ore is extracted, crushed, and then purified by chemical means. For examples of purification, see blast furnace (for the smelting of iron ore) Castner-Kellner process (for the production of chlorine) Frasch process (for the production of sulfur). 

The major processes for manufacturing chlorine and caustic soda are based on electrolytic procedures and have been since the 1890s. In the UK the introduction of the Castner Kellner process in 1897 was a major development in chlor-alkali technology. At present over 90% of the world s requirement for chlorine is obtained electrolytically from aqueous sodium chloride and the rest from the molten salt. The proliferation of cells used in the 1930s and 1940s has now been reduced to three cell types, two diaphragm cells and the mercury cell. The latter is being phased out, however, because of the hazardous nature of mercury. 

Castner-Kellner process A process once used to produce chlorine and sodium hy-droxidebythe electrolysis of sodium chloride solution. The electrolysis took place in a cell with a mercury cathode and graphite anode. The cell consisted of three compartments with a common bed of mercury and solution of sodium chloride above. The cathode was in the central com partment and anodes in the other two. It was invented independently by American industrial chemist Hamilton Young Castner (1858-99), who was working in the UK at the time, and Austrian chemical engineer Karl Kellner (1851-1905). The process was abandoned due to concerns over mercury pollution and replaced by various diaphragm-based electrolytic processes. 

The process operates at around 90°C with an excess of lime and the precipitated calcium carbonate separated. Developed in the nineteenth century, the process was used after the Leblanc process and before the Castner-Kellner process. 

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