Alum

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At the time, potassium "potash" was believed to be exclusively found on plants. However, in , 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 he published a dissertation demonstrating that alum is a double salt , composed of sulfuric acid, alumina, and potash. 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 3. When heated to nearly a red heat, it gives a porous, friable mass, which is known as "burnt alum". 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 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.

Potassium alum is used in medicine mainly as an astringent or styptic and antiseptic. 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.

Example sentences containing 'alum'

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. It is used in dentistry especially in gingival retraction cords because of its astringent and hemostatic properties. 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 [34] [35] contribute to its traditional use as an underarm deodorant. Today, potassium or ammonium alum is sold commercially for this purpose as a "deodorant crystal". Potassium alum was the major adjuvant used to increase the efficacy of vaccines , and has been used since the s.

Alum may be used in depilatory waxes used for the removal of body hair or applied to freshly waxed skin as a soothing agent. In the s, men sporting crewcut or flattop hairstyles sometimes applied alum to their hair, as an alternative to pomade , to keep the hair standing up. Potassium alum may be an acidic ingredient of baking powder to provide a second leavening phase at high temperatures although sodium alum is more commonly used for that purpose [ citation needed ].

Usage Tips

Alum was used by bakers in England during the s to make bread whiter. This was theorized by some, including John Snow , to cause rickets. Potassium alum, under the name "alum powder", is found in the spice section of many grocery stores in the US.

I used Alum to help with canker sores. I read about it online, and Walmart was the easiest place to order it from.

About This Item

Good for the price. Bboatk, March 12, Used for a Science Fair Project. My 10yr old son had used it for his science fair project. He was growing crystals on egg shells. Big crystals grew on the eggshells. So he was very happy.

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Candy, January 23, Keeps hydrangeas fresh for days. The various solubilities are shown in the following table. Aluminium-based alums have been used since antiquity, and are still important in many industrial processes. The most widely used alum is potassium alum. It was used since antiquity as a flocculant to clarify turbid liquids, as a mordant in dying , and in tanning. It is still widely used to purify piped water, in medicine, for cosmetics in deodorant and antitranspirants , in food preparation in baking powder and pickling , and to fire-proof paper and cloth.

Sodium alum is used in substitution to potassium alum in baking powders. Ammonium alum has a few niche uses.

McCormick® Alum

Other alums have mostly research interest. In traditional Japanese art , alum and animal glue were dissolved in water, forming a liquid known as dousa ja: Alum in the form of potassium aluminum sulphate in a concentrated bath of hot water is regularly used by jewelers and machinists to dissolve hardened steel drill bits that have broken off in items made of aluminum, copper, brass, gold any karat and silver both sterling and fine. This is because alum does not react chemically to any significant degree with any of these metals, but will corrode steel.

A detailed description of a substance called alumen occurs in Pliny the Elder 's Natural History. Pliny informs us that a form of alumen was found naturally in the earth, and calls it salsugoterrae. Pliny wrote that different substances were distinguished by the name of alumen , but they were all characterised by a certain degree of astringency, and were all employed in dyeing and medicine.

This property seems to characterize a solution of iron sulfate in water; a solution of ordinary potassium alum would possess no such property. Contamination with iron sulfate was greatly disliked as this darkened and dulled dye colours.

In some places the iron sulfate may have been lacking, so the salt would be white and would be suitable, according to Pliny, for dyeing bright colors. Pliny describes several other species of alumen but it is not clear as to what these minerals are.

Definition of 'alum'

The alumen of the ancients then, was not always potassium alum, not even an alkali aluminum sulfate. The production of potassium alum from alunite is archaeologically attested on the island Lesbos. The western desert of Egypt was a major source of alum substitutes in antiquity.

Alum and green vitriol iron sulfate both have sweetish and astringent taste, and they a had overlapping uses. Therefore, through the Middle Ages , alchemists and other writers do not seem to have discriminated the two salts accurately from each other. In the writings of the alchemists we find the words misy , sory , and chalcanthum applied to either compound; and the name atramentum sutorium , which one might expect to belong exclusively to green vitriol, applied indifferently to both.

In the early s, Georg Ernst Stahl claimed that reacting sulfuric acid with limestone produced a sort of alum. 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.

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