Alkali manufacture
- This is a historical article, primarily based on the Encyclopædia Britannica Eleventh Edition. 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 carbonate, potassium hydroxide and potassium carbonate.
A number of processes have been proposed for the manufacture of alkali from various metals, the most common being the Leblanc and ammonia-soda processes.[1]
The Lime process
Historically, sodium hydroxide was produced by treating sodium carbonate (usually from seaweed ash or "glasswort"-plant ash) with calcium hydroxide (aka Lime) in a metathesis reaction. (Sodium hydroxide is soluble while calcium carbonate is not.) This process was called causticizing.[2]
The Leblanc Process
The Leblanc process, which was invented by Nicolas Leblanc around 1790, begins with the decomposition of sodium chloride by sulfuric acid, by which sodium sulfate and hydrochloric acid are produced. The sodium sulfate is afterwards fired with calcium carbonate and coal. Sodium carbonate can be extracted from this mixture by washing the mixture with water.[1]
Until the rise of the ammonia-soda process, which has better economics, the Leblanc process was used extensively making the United Kingdom the lead in alkali production. By the early 20th century, the UK's production outstripped that of all other producers combined.[1]
Most of the British alkali works are situated in South Lancashire and the adjoining part of Cheshire, near the mouth of the Tyne and in the West of Scotland.[1]
The Ammonia-Soda Process
Despite improvements made to the
There are a number of reasons for this:
- The sodium used in the process is practically free.
- The fuel requirement is halved.
- Efficiency improvements have reduced 'waste' in the process to a minimum.
The only way in which the Leblanc process could still hold its own was by being turned in the direction of making
The ammonia-soda process was first patented on 30 June 1838 by Harrison Gray Dyar and John Hemming,
Other processes
- Castner-Kellner process
References
- ^ a b c d e f public domain: Chisholm, Hugh, ed. (1911). "Alkali Manufacture". Encyclopædia Britannica. Vol. 1 (11th ed.). Cambridge University Press. pp. 674–685. One or more of the preceding sentences incorporates text from a publication now in the
- ^ Deming, Horace G. (1925). General Chemistry: An Elementary Survey Emphasizing Industrial Applications of Fundamental Principles (2nd ed.). New York: John Wiley & Sons, Inc. p. 452.
- ^ "Soda ash, Solvay style". American Chemical Society. Retrieved 21 April 2017.
- ^ Newton, William (1839). The London Journal of Arts and Sciences, and Repertory of Patent Inventions. Vol. 14. p. 400.