3D model (JSmol)
|E number||E522 (acidity regulators, ...)|
|Molar mass||258.192 g/mol (anhydrous)|
474.37 g/mol (dodecahydrate)
|Melting point||92 to 95 °C (198 to 203 °F; 365 to 368 K)|
|Boiling point||200 °C (392 °F; 473 K)|
|14.00 g/100 mL (20 °C) |
36.80 g/100 mL (50 °C)
|Solubility in other solvents||Insoluble in acetone|
Refractive index (nD)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Potassium alum, potash alum, or potassium aluminium sulfate is a chemical compound: the double sulfate of potassium and aluminium, with chemical formula KAl(SO4)2. It is commonly encountered as the dodecahydrate, KAl(SO4)2·12H2O. It crystallizes in cubic structure with space group P a -3 and lattice parameter of 12.18 Å. The compound is the most important member of the generic class of compounds called alums, and is often called simply alum.
Potassium alum is commonly used in water purification, leather tanning, dyeing, fireproof textiles, and baking powder as E number E522. It also has cosmetic uses as a deodorant, as an aftershave treatment and as a styptic for minor bleeding from shaving.
- 1 History
- 2 Characteristics
- 3 Natural occurrence
- 4 Industrial production
- 5 Uses
- 6 Toxicology and safety
- 7 See also
- 8 References
Potassium alum was known to the Ancient Egyptians, who obtained it from evaporites in the Western desert and reportedly used it as early as 1500 BCE to reduce the visible cloudiness (turbidity) in the water.
Potassium alum was described under the name alumen or salsugoterrae by Pliny, and it is clearly the same as the stupteria described by Dioscorides. However, the name alum and other names applied to this substance — like misy, sory, chalcanthum, and atramentum sutorium — were often applied to other products with vaguely similar properties or uses, such as iron sulfate or "green vitriol".
In the middle and modern ages
Potassium alum was imported into England mainly from the Middle East, and, from the late 15th century onwards, the Papal States for hundreds of years. Its use there was as a dye-fixer (mordant) for wool (which was one of England's primary industries, the value of which increased significantly if dyed).
Historically, potassium alum was used extensively in the wool industry from Classical antiquity, during the Middle Ages, and well into 19th century as a mordant or dye fixative in the process of turning wool into dyed bolts of cloth.
In the 13th and 14th centuries, alum (from alunite) was a major import from Phocaea (Gulf of Smyrna in Byzantium) by Genoans and Venetians (and was a cause of war between Genoa and Venice) and later by Florence. After the fall of Constantinople, alunite (the source of alum) was discovered at Tolfa in the Papal States (1461). The textile dyeing industry in Bruge, and many other locations in Italy, and later in England, required alum to stabilize the dyes onto the fabric (make the dyes "fast") and also to brighten the colors.
With state financing, attempts were made throughout the 16th century, but without success until early on in the 17th century. An industry was founded in Yorkshire to process the shale, which contained the key ingredient, aluminium sulfate, and made an important contribution to the Industrial Revolution. One of the oldest historic sites for the production of alum from shale and human urine are the Peak alum works in Ravenscar, North Yorkshire. By the 18th century, the landscape of northeast Yorkshire had been devastated by this process, which involved constructing 100-foot (30 m) stacks of burning shale and fuelling them with firewood continuously for months. The rest of the production process consisted of quarrying, extraction, steeping of shale ash with seaweed in urine, boiling, evaporating, crystallisation, milling and loading into sacks for export. Quarrying ate into the cliffs of the area, the forests were felled for charcoal and the land polluted by sulfuric acid and ash.
Identification of the formula
In the early 1700s, Georg Ernst Stahl claimed that reacting sulfuric acid with limestone produced a sort of alum. The error was soon corrected by Johann Pott and Andreas Marggraf, who showed that the precipitate obtained when an alkali is poured into a solution of alum, namely alumina, is quite different from lime and chalk, and is one of the ingredients in common clay.
Marggraf also showed that perfect crystals with properties of alum can be obtained by dissolving alumina in sulfuric acid and adding potash or ammonia to the concentrated solution. In 1767, Torbern Bergman observed the need for potassium or ammonium sulfates to convert aluminium sulfate into alum, while sodium or calcium would not work.
At the time, potassium ("potash") was believed to be exclusively found on plants. However, in 1797, Martin Klaproth discovered the presence of potassium in the minerals leucite and lepidolite.
Louis Vauquelin then conjectured that potassium was likewise an ingredient in many other minerals. Given Marggraf and Bergman's experiments, he suspected that this alkali constituted an essential ingredient of natural alum. In 1797 he published a dissertation demonstrating that alum is a double salt, composed of sulfuric acid, alumina, and potash. In the same journal volume, Jean-Antoine Chaptall published the analysis of four different kinds of alum, namely, Roman alum, Levant alum, British alum and alum manufactured by himself, confirming Vauquelin's results.
Potassium alum crystallizes in regular octahedra with flattened corners and is very soluble in water. The solution is slightly acidic and is astringent to the taste. Neutralizing a solution of alum with potassium hydroxide will begin to cause the separation of alumina Al(OH)
When heated to nearly a red heat, it gives a porous, friable mass, which is known as "burnt alum". It fuses at 92 °C (198 °F) in its own water of crystallization.
Potassium alum dodecahydrate occurs in nature as a sulfate mineral called alum-(K), typically as encrustations on rocks in areas of weathering and oxidation of sulfide minerals and potassium-bearing minerals.
In the past, potassium alum has been obtained from alunite (KAl(SO
3), mined from sulfur-containing volcanic sediments. Alunite is an associate and likely potassium and aluminium source. It has been reported at Vesuvius, Italy; east of Springsure, Queensland; in Alum Cave, Tennessee; Alum Gulch, Santa Cruz County, Arizona and the Philippine island of Cebu.
In order to obtain alum from alunite, it is calcined and then exposed to the action of air for a considerable time. During this exposure it is kept continually moistened with water, so that it ultimately falls to a very fine powder. This powder is then lixiviated with hot water, the liquor decanted, and the alum allowed to crystallize.
Potassium alum historically was mainly extracted from alunite.
Potassium alum is now produced industrially by adding potassium sulfate to a concentrated solution of aluminium sulfate. The aluminium sulfate is usually obtained by treating minerals like alum schist, bauxite and cryolite with sulfuric acid. If much iron should be present in the sulfate then it is preferable to use potassium chloride in place of potassium sulfate.
Medicine and cosmetics
Styptic pencils are rods composed of potassium alum or aluminum sulfate, used topically to reduce bleeding in minor cuts (especially from shaving) and abrasions, nosebleeds, and hemorrhoids, and to relieve pain from stings and bites. Potassium alum blocks were rubbed over the wet skin after shaving.
Potassium alum was also used topically to remove pimples and acne, and to cauterize aphthous ulcers in the mouth and canker sores, as it has a significant drying effect to the area and reduces the irritation felt at the site.. It has been used to stop bleeding in cases of hemorrhagic cystitis. and is used in some countries as a cure for hyperhidrosis.
Potassium and ammonium alum are the active ingredients in some antiperspirants and deodorants, acting by inhibiting the growth of the bacteria responsible for body odor. Alum's antiperspirant and antibacterial properties contribute to its traditional use as an underarm deodorant. It has been used for this purpose in Europe, Mexico, Thailand (where it is called sarn-som), throughout Asia and in the Philippines (where it is called tawas). Today, potassium or ammonium alum is sold commercially for this purpose as a "deodorant crystal". Beginning in 2005 the US Food and Drug Administration no longer recognized it as a wetness reducer, however it is still available and used in several other countries, primarily in Asia.
Potassium alum was the major adjuvant used to increase the efficacy of vaccines, and has been used since the 1920s. But it has been almost completely replaced by aluminium hydroxide and aluminium phosphate in commercial vaccines.
Alum may be used in depilatory waxes used for the removal of body hair or applied to freshly waxed skin as a soothing agent.
Alum was used by bakers in England during the 1800s to make bread whiter. This was theorized by some, including John Snow, to cause rickets. The Sale of Food and Drugs Act 1875 prevented this and other adulterations.
Potassium alum, under the name "alum powder", is found in the spice section of many grocery stores in the US. Its chief culinary use is in pickling recipes, to preserve and add crispness to fruit and vegetables.
Potassium alum is used in leather tanning, in order to remove moisture from the hide and prevent rotting. Unlike tannic acid, alum doesn't bind to the hide and can be washed out of it.
Potassium alum has been used since remote antiquity for purification of turbid liquids. It is still widely used in the purification of water for drinking and industrial processes water, treatment of effluents and post-storm treatment of lakes to precipitate contaminants.
Between 30 and 40 ppm of alum for household wastewater, often more for industrial wastewater, is added to the water so that the negatively charged colloidal particles clump together into "flocs", which then float to the top of the liquid, settle to the bottom of the liquid, or can be more easily filtered from the liquid, prior to further filtration and disinfection of the water. Like other similar salts, it works by neutralizing the electrical double layer surrounding very fine suspended particles, allowing them to join into flocs.
Dissolving iron and steel
Alum solution has the property of dissolving steels while not affecting aluminium or base metals. Alum solution can be used to dissolve steel tool bits that have become lodged in machined castings, for instance.
Alum is an ingredient in some recipes for homemade modeling compounds intended for use by children. These are often called "play clay" or "play dough" for their similarity to "Play-Doh".
Toxicology and safety
- "Alum-(K) Mineral Data". Mineralogy Database. Retrieved 2013-04-19.
- International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC–IUPAC. ISBN 0-85404-438-8. Electronic version.
- "Aluminium potassium sulfate dodecahydrate". ChemExper. Retrieved 2013-04-19.
- Crystallography Open Database http://crystallography.net/cod/1011177.html. Missing or empty
- Bottomley, L.; Bottomley, L.A. (2010). Chemistry 1310: Laboratory Manual. Plymouth, MI: School of Chemistry & Biochemistry, Georgia Institute of Technology and Hayden-McNeil Publishing. ISBN 978-0-7380-3819-3.
- Editors, The. "alum | chemical compound". Britannica.com. Retrieved 2016-01-18.
- Helmenstine, Anne Marie. "What is Alum?". About.com. Retrieved 2013-04-19.
- Alumen, and the Several Varieties of it; Thirty-eight Remedies., Pliny the Elder, The Natural History, book 35, chapter 52; on the Perseus Digital Library at Tufts University. Last accessed 27 December 2011.
- Dioscorides, book 5, chapter 123.
- Chisholm 1911, pp. 766-767.
- A. Archontidou 2005, "Un atelier de preparation de l'alun a partir de l'alunite dans l'isle de Lesbos" in L'alun de Mediterranée. ed P. Borgard et al.
- "How alum shaped the Yorkshire coast". National Trust, UK.
- See Henry VII of England trade section. Henry broke the Pope's monopoly by financing shipping bootstrapping a trading system with the Ottoman Empires mines
- "Color in Relation to the Political and Economic History of the Western World" by Sidney M Edelstein, Proceedings of the Perkin Centennial, American Association of Textile Chemists and Colorists, September, 1956
- "Worldly Goods: A New History of the Renaissance", Lisa Jardine, 1996, Norton&Co, pages 114-116 ISBN 978-0393318661
- Stephen Chance. "Was alum the first example of the north-east's 'dirty' industries? | UK news". The Guardian. Retrieved 2017-03-25.
- George Ernst Stahl (1703), Specimen Beccherianum. Johann Ludwig Gleditsch, Leipzig.
- George Ernst Stahl (1723), Ausführliche Betrachtung und zulänglicher Beweiss von den Saltzen, daß diesselbe aus einer zarten Erde, mit Wasser innig verbunden, bestehen (Detailed treatment and adequate proof of salts, that they consist of a subtile earth intimately bound with water) Wäysenhaus, Halle.
- Johann Heinrich Pott (1746), Chymische Untersuchungen, welche fürnehmlich von der Lithogeognosia oder Erkäntniß und Bearbeitung der gemeinen einfacheren Steine und Erden ingleichen von Feuer und Licht handeln, volume 1, p. 32.
- Andreas Sigismund Marggraf (1754), "Expériences faites sur la terre d'alun" (Experiments made on the earth of alum), Mémoires de l'Académie des sciences et belles-lettres de Berlin, pp. 41-66.
- Chisholm 1911, p. 766.
- Marggraf (1754) "Expériences qui concernent la régénération de l'alun de sa propre terre, l'après avoir séparé par l'acide vitriolique ; avec quelques compositions artificielles de l'alun par moyen d'autres terres, et dudit acide". Mémoires de l'Académie des sciences et belles-lettres de Berlin, pp. 31-40.
- Torbern Bergman (1767), "IX. De confectione Aluminis". In Opuscula physica et chemica, I. G. Müller, Leipzig, 1788), volume 1, pp. 306-307.
- Martin Heinrich Klaproth (1797), Beiträge zur Chemischen Kenntniss Der Mineralkörper (Contributions to [our] chemical knowledge of mineral substances). Decker and Co., Posen, and Heinrich August Rottmann, Berlin; pp. 45-46 and [https://babel.hathitrust.org/cgi/pt?id=nyp.33433066422746;view=1up;seq=213 p. 193.
- Martin Heinrich Klaproth (1801), Analytical Essays Towards Promoting the Chemical Knowledge of Mineral Substances. T. Cadell, Jr. & W. Davies, London. His finding of potassium in leucite appears on pp. 353-354.: "On the contrary, I was surprised in an unexpected manner, by discovering in it another constituent part, consisting of a substance, the existence of which, certainly, no one person would have conjectured within the limits of the mineral kingdom … This constituent part of leucite … is no other than pot-ash, which, hitherto, has been thought exclusively to belong to the vegetable kingdom, and has, on this account, been called VEGETABLE ALKALI. — This discovery, which I think of great importance, cannot fail to occasion considerable changes in the systems of natural history, … .". The discovery of potassium in lepidolite is mentioned on p. 472.
- Vauquelin (1797), "Sur la nature de l'Alun du commerce, sur l'existence de la potasse dans ce sel, et sur diverses combinaisons simples ou triples de l'alumine avec l'acide sulfurique" (On the nature of commercial alum, on the existence of potash in this salt, and on various simple or triple compounds of alumina with sulfuric acid). In Annales de Chimie et de Physique, 1st series, volume 22, pages 258-279.
- Jean-Antoine Chaptal (1797), "Comparée des quatre principales sortes d'Alun connues dans le commerce; et Observations sur leur nature et leur usage" (Comparison of the four main types of commercial alum; and observations on their nature and use). In Annales de Chimie et de Physique, 1st series, volume 22, pages 280-296.
- Bottomley (2010) p. 35.
- "Alum-(K) mineral data and information". MinDat. Retrieved 2013-04-19.
- "Kalinite Mineral Data". MinDat. Retrieved 2013-04-19.
- Otto Helmboldt, L. Keith Hudson, Chanakya Misra, Karl Wefers, Wolfgang Heck, Hans Stark, Max Danner, Norbert Rösch "Aluminium Compounds, Inorganic" in Ullmann's Encyclopedia of Industrial Chemistry 2007, Wiley-VCH, Weinheim.doi:10.1002/14356007.a01_527.pub2
- Chisholm 1911, p. 767.
- Handa, Parvesh (1982). Herbal beauty care. New Delhi: Orient Paperbacks. p. 12. ISBN 9788122200249. Retrieved 7 January 2016.
- Kennedy, C; Snell, ME; Witherow, RE (1984). "Use of Alum to Control Intractable Vesical Haemorrhage". British Journal of Urology. 56 (6): 673–675. doi:10.1111/j.1464-410X.1984.tb06143.x.
- Kanlayavattanakul, M.; Lourith, N. (1 August 2011). "Body malodours and their topical treatment agents". International Journal of Cosmetic Science. 33 (4): 298–311. doi:10.1111/j.1468-2494.2011.00649.x. PMID 21401651.
- Aguilar, T. N.; Blaug, S.M.; Zopf, L.C. (July 1956). "A study of the antibacterial activity of some complex aluminum salts". Journal of the American Pharmaceutical Association. 45 (7): 498–500. doi:10.1002/jps.3030450720. PMID 13345689.
- US patent 5399364, Francis Verdan, "Cosmetic assembly defined by encased stick of alum", issued 1995-05-21
- Baki, Gabriella; Alexander, Kenneth S. (2015-04-27). Introduction to Cosmetic Formulation and Technology. John Wiley & Sons. p. 324. ISBN 9781118763780.
- Mbow, M Lamine; De Gregorio, Ennio; Ulmer, Jeffrey B (2011). "Alum's adjuvant action: grease is the word". Nature Medicine. 17 (4): 415–416. doi:10.1038/nm0411-415. PMID 21475229.
- Marrack, Philippa; McKee, Amy S.; Munks, Michael W. (2009). "Towards an understanding of the adjuvant action of aluminium". Nature Reviews Immunology. 9 (4): 287–293. doi:10.1038/nri2510. ISSN 1474-1733. PMC 3147301. PMID 19247370.
- "On the adulteration of bread as a cause of rickets" (PDF). ucla.edu.
- Church Pastoral-aid Society, London (January–June 1847). "Brown Bread". The Church of England Magazine. 22: 355.
- Hassall, Arthur Hill (1857). "Adulterations detected; or, Plain instructions for the discovery of frauds in food and medicine".
- Harampolis, Alethea; Rizzo, Jill (2013). The Flower Recipe Book. Artisan Books. ISBN 9781579655303.
- Young, Laura S. (1995). Bookbinding & Conservation by Hand: A Working Guide. Oak Knoll Press. ISBN 9781884718113.
- berger, g (1840). The Mechanic and Chemist.
- Samuel D. Faust, Osman M. Aly (1999). Chemistry of water treatment (2nd ed.). Chelsea, MI: Ann Arbor Press. ISBN 9781575040110.
- "Storm water treatment will strip phosphorus from Arboretum pond, College of Engineering @ The University of Wisconsin-Madison, initiatives in energy, health, nanotechnology, security, and information technology". Engr.wisc.edu. Retrieved 2016-01-18.
- Bratby, John (2006). Coagulation and flocculation in water and wastewater treatment (2nd ed.). London: IWA Publ. ISBN 9781843391067.
- Rice, J. K. (June 1957). "The use of organic flocculants and flocculating aids in the treatment of industrial water and industrial waste water". Symposium on Industrial Water and Industrial Waste Water (207): 41–51.
- Dackerman, Susan (2002). Painted Prints: The Revelation of Color in Northern Renaissance & Baroque Engravings, Etchings, & Woodcuts. Penn State Press. ISBN 978-0271022352.
- https://www.youtube.com/watch?v=fqZYgReuywM AvE demonstrates use of alum to remove a broken stud from an aluminium engine head
- "What did you do today? (2014)". Model Engineer. Retrieved 2017-03-25.
- Gallego H, Lewis EJ, Crutchfield CE 3rd (July 1999). "Crystal deodorant dermatitis: irritant dermatitis to alum-containing deodorant". Cutis. 64 (1): 65–6. PMID 10431678.CS1 maint: Multiple names: authors list (link)