Alum
Encyclopedia
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
and a class of chemical compounds. The specific compound is the hydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
d potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
(potassium alum
Potassium alum
Potassium alum, potash alum or tawas is the potassium double sulfate of aluminium. Its chemical formula is KAl2 and it is commonly found in its dodecahydrate form as KAl2·12. Alum is the common name for this chemical compound, given the nomenclature of potassium aluminum sulfate dodecahydrate...
) with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
K
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
Al
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
(SO4
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
)2.12H2O
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
. The wider class of compounds known as alums have the related empirical formula, AB(SO4)2.12H2O.
Chemical properties
Alums are useful for a range of industrial processes. They are soluble in water; have an astringentAstringent
An astringent substance is a chemical compound that tends to shrink or constrict body tissues, usually locally after topical medicinal application. The word "astringent" derives from Latin adstringere, meaning "to bind fast"...
, acid, and sweetish taste; react acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
to litmus
Litmus
Litmus or litmus test may refer to:* Litmus test, a common pH test* Litmus , a test case management tool maintained by Mozilla* "Litmus" , an episode in the first season of the television series...
; and crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
lize in regular octahedra
Octahedron
In geometry, an octahedron is a polyhedron with eight faces. A regular octahedron is a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex....
. When heated they liquefy; and if the heating is continued, the water of crystallization
Water of crystallization
In crystallography, water of crystallization or water of hydration or crystallization water is water that occurs in crystals. Water of crystallization is necessary for the maintenance of crystalline properties, but capable of being removed by sufficient heat...
is driven off, the salt froths and swells, and at last an amorphous powder remains.
Industrial uses
Potassium alumPotassium alum
Potassium alum, potash alum or tawas is the potassium double sulfate of aluminium. Its chemical formula is KAl2 and it is commonly found in its dodecahydrate form as KAl2·12. Alum is the common name for this chemical compound, given the nomenclature of potassium aluminum sulfate dodecahydrate...
is the common alum of commerce, although soda alum
Soda alum
Sodium aluminium sulfate, NaAl2·12H2O or Na2SO4·Al23·24H2O, also known as soda alum or sodium alum, is a form of alum used in the acidity regulator of food as well as in the manufacture of baking powder...
, ferric alum
Ammonium iron(III) sulfate
Ammonium iron sulfate, NH4Fe2·12 H2O, also known as ferric ammonium sulfate or iron alum, is a double salt in the class of alums, which consists of compounds with the general formula AB2 · 12 H2O. It has the appearance of weakly violet, octahedrical crystals...
, and ammonium alum
Ammonium alum
Ammonium aluminium sulfate, also known as ammonium alum is a white crystalline double sulfate usually encountered as the dodecahydrate, formula Al2·12H2O. It is used in small amounts in a variety of niche applications...
are manufactured.
Alum is also used in purification of drinking water in industries. In a holding tank, some alum (phitkari) is added to the water so that the negatively charged light colloidal parts stick together and get lighter & float above (flocculate) when alum makes the colloidal particles neutralized by making its aluminum ions get loaded with the colloidal parts. When the colloidal parts get heavy they can be easily separated from the tank prior to further filtration and disinfection of the water.
Cosmetic
- Alum in block form (usually potassium alumPotassium alumPotassium alum, potash alum or tawas is the potassium double sulfate of aluminium. Its chemical formula is KAl2 and it is commonly found in its dodecahydrate form as KAl2·12. Alum is the common name for this chemical compound, given the nomenclature of potassium aluminum sulfate dodecahydrate...
) is used as a blood coagulant. - Styptic pencils containing aluminium sulfate or potassium aluminium sulfate are used as astringentAstringentAn astringent substance is a chemical compound that tends to shrink or constrict body tissues, usually locally after topical medicinal application. The word "astringent" derives from Latin adstringere, meaning "to bind fast"...
s to prevent bleeding from small shaving cuts. - Alum was used as a base in skin whiteners and treatments during the late 16th century. A recipe for one such compound was given thus:
"For the Freckles which one getteth by the heat of the Sun: Take a little Allom beaten small, temper amonst it a well brayed white of an egg, put it on a milde fire, stirring it always about that it wax not hard, and when it casteth up the scum, then it is enough, wherewith anoint the Freckles the space of three dayes: if you will defend your self that you get no Freckles on the face, then anoint your face with the whites of eggs." —Christopher Wirzung, General Practise of Physicke, 1654.
- 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 1950s, men sporting crewcut or flattop hairstyles sometimes applied alum to their front short hairs as an alternative to pomadePomadePomade is a greasy or waxy substance that is used to style hair. Pomade makes hair look slick and shiny. Unlike hair spray and hair gel, pomade does not dry and often takes several washes to remove...
. When the hair dried, it would stay up all day. - Alum's antibacterial properties contribute to its traditional use as an underarm deodorantDeodorantDeodorants are substances applied to the body to affect body odor caused by bacterial growth and the smell associated with bacterial breakdown of perspiration in armpits, feet and other areas of the body. A subgroup of deodorants, antiperspirants, affect odor as well as prevent sweating by...
. 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 alum is sold commercially for this purpose as a "deodorant crystal," often in a protective plastic case.
Medicinal
- Alum is used in many subunit vaccines as an adjuvantImmunologic adjuvantIn immunology, an adjuvant is an agent that may stimulate the immune system and increase the response to a vaccine, without having any specific antigenic effect in itself. The word “adjuvant” comes from the Latin word adiuvare, meaning to help or aid...
to enhance the body's response to immunogens. Such vaccines include hepatitis AHepatitis AHepatitis A is an acute infectious disease of the liver caused by the hepatitis A virus , an RNA virus, usually spread the fecal-oral route; transmitted person-to-person by ingestion of contaminated food or water or through direct contact with an infectious person...
, hepatitis B, and DTaP. - Alum in powder or crystal form, or in styptic pencilStyptic pencilAn antihemorrhagic agent is a substance that promotes hemostasis . It may also be known as a hemostatic agent....
s, is sometimes applied to cuts to prevent or treat infection. - Powdered alum is commonly cited as a home remedy for canker sores.
- Preparations containing alum are used by pet owners to stem bleeding associated with animal injuries caused by improper nail clipping.
- Alum is listed as an ingredient of some brands of toothpasteToothpasteToothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing...
or toothpowder. - Alum powder dissolved in 5 parts water has been used to shrink hemorrhoids and stop them from bleeding.
Culinary
- Alum powder, found in the spice section of many grocery stores, may be used in pickling recipes as a preservative to maintain fruit and vegetable crispness.
- Alum is used as the acidic component of some commercial baking powders.
- Alum was used by bakers in England during the 1800s to make bread whiter. In 1875, the Sale of Food and Drugs Act prevented this and other adulterations.
Flame retardant
- Solutions containing alum may be used to treat cloth, wood, and paper materials to increase their resistance to fire.
- Alum is also a component of foamite.
- Alum is also used in fire extinguisherFire extinguisherA fire extinguisher or extinguisher, flame entinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations...
s to smother chemical and oil fires.
Chemical flocculant
- Alum is used to clarify water by neutralizing the electrical double layer surrounding very fine suspended particles, allowing them to flocculate (stick together). After flocculation, the particles will be large enough to settle and can be removed.
- Alum may be used to increase the viscosityViscosityViscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
of a ceramic glazeCeramic glazeGlaze is a layer or coating of a vitreous substance which has been fired to fuse to a ceramic object to color, decorate, strengthen or waterproof it.-Use:...
suspensionSuspension (chemistry)In chemistry, a suspension is a heterogeneous fluid containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than 1 micrometer. The internal phase is dispersed throughout the external phase through mechanical agitation, with the use of certain...
; this makes the glaze more readily adherent and slows its rate of sedimentationSedimentationSedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained, and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration...
. - 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-DohPlay-DohPlay-Doh is a modeling compound used by young children for art and craft projects at home and in school. Composed of flour, water, salt, boric acid, and mineral oil, the product was first manufactured in Cincinnati, Ohio, USA as a wallpaper cleaner in the 1930s...
", a trademarked product marketed by American toy manufacturer HasbroHasbroHasbro is a multinational toy and boardgame company from the United States of America. It is one of the largest toy makers in the world. The corporate headquarters is located in Pawtucket, Rhode Island, United States...
).
In antiquity
The word "alumen" occurs in PlinyPliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...
's Natural History. In the 52nd chapter of his 35th book, he gives a detailed description. By comparing this with the account of stupteria given by Dioscorides in the 123rd chapter of his 5th book, it is obvious that the two are identical. Pliny informs us that alumen was found naturally in the earth. He calls it salsugoterrae. Different substances were distinguished by the name of "alumen"; but they were all characterized by a certain degree of astringency, and were all employed in dyeing and medicine, the light-colored alumen being useful in brilliant dyes, the dark-colored only in dyeing black or very dark colors. One species was a liquid, which was apt to be adulterated; but when pure it had the property of blackening when added to pomegranate
Pomegranate
The pomegranate , Punica granatum, is a fruit-bearing deciduous shrub or small tree growing between five and eight meters tall.Native to the area of modern day Iran, the pomegranate has been cultivated in the Caucasus since ancient times. From there it spread to Asian areas such as the Caucasus as...
juice. This property seems to characterize a solution of iron sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
in water; a solution of ordinary (potassium) alum would possess no such property. Pliny says that there is another kind of alum that the Greek
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
s call schistos. It forms in white threads upon the surface of certain stones. From the name schistos, and the mode of formation, it appears that this species was the salt which forms spontaneously on certain salty minerals, as alum slate
Slate
Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. The result is a foliated rock in which the foliation may not correspond to the original sedimentary layering...
and bituminous shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
, and which consists chiefly of sulfates of iron and aluminium. Possibly in certain places the iron sulfate may have been nearly wanting, and then the salt would be white, and would answer, as Pliny says it did, for dyeing bright colors. Several other species of alumen are described by Pliny, but we are unable to make out to what minerals he alludes.
The alumen of the ancients, then, was not always the same as the alum of the moderns. They certainly knew how to produce alum from alunite
Alunite
Alunite is a sulfate mineral that was first observed in the 15th century in Monti della Tolfa, north of Rome, where it was mined for the manufacture of alum. First called aluminilite by J.C. Delamétherie in 1797, this name was contracted by François Beudant in 1824 to alunite.Distinct crystals of...
, as this process is archaeologically attested on the island Lesbos. This site was abandoned in the 7th century but dates back at least to the 2nd century AD. Native alumen from Melos appears to have been a mixture mainly of alunogen (Al2(SO4)3.17H2O) with alum and other minor sulfates. The western desert of Egypt was a major source of alum substitutes in antiquity. These evaporites were mainly FeAl2(SO4)4.22H2O, MgAl2(SO4)4.22H2O, NaAl(SO4)2.6H2O, MgSO4.7H2O and Al2(SO4)3.17H2O. Any contamination with iron sulfate was greatly disliked as this darkened and dulled dye colours. They were acquainted with a variety of substances of varying degrees of purity by the names of misy, sory, and chalcanthum. As alum and green vitriol
Iron(II) sulfate
Iron sulfate or ferrous sulfate is the chemical compound with the formula FeSO4. Known since ancient times as copperas and as green vitriol, the blue-green heptahydrate is the most common form of this material...
were applied to a variety of substances in common, and as both are distinguished by a sweetish and astringent taste, writers, even after the discovery of alum, do not seem to have discriminated the two salts accurately from each other. In the writings of the alchemists
Alchemy
Alchemy is an influential philosophical tradition whose early practitioners’ claims to profound powers were known from antiquity. The defining objectives of alchemy are varied; these include the creation of the fabled philosopher's stone possessing powers including the capability of turning base...
we find the words misy, sory, chalcanthum applied to alum as well as to iron sulfate; and the name atramentum sutorium, which ought to belong, one would suppose, exclusively to green vitriol, applied indifferently to both. Various mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s are employed in the manufacture of alum, the most important being alunite, alum schist
Schist
The schists constitute a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is...
,
bauxite
Bauxite
Bauxite is an aluminium ore and is the main source of aluminium. This form of rock consists mostly of the minerals gibbsite Al3, boehmite γ-AlO, and diaspore α-AlO, in a mixture with the two iron oxides goethite and hematite, the clay mineral kaolinite, and small amounts of anatase TiO2...
and cryolite
Cryolite
Cryolite is an uncommon mineral identified with the once large deposit at Ivigtût on the west coast of Greenland, depleted by 1987....
.
Alchemical and later discoveries and uses
In the 18th century, J. H. Pott and Andreas Sigismund MarggrafAndreas Sigismund Marggraf
Andreas Sigismund Marggraf was a German chemist and pioneer of analytical chemistry from Berlin, which was then the capital of Brandenburg, a major principality of the Holy Roman Empire. He isolated zinc in 1746 by heating calamine and carbon...
demonstrated that alumina was a constituent. Pott in his Lithogeognosia showed that the precipitate
Precipitation (chemistry)
Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...
obtained when an alkali is poured into a solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
of alum is quite different from lime
Lime (mineral)
Lime is a general term for calcium-containing inorganic materials, in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide. It is also the name for a single mineral of the CaO composition, occurring very rarely...
and chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
, with which it had been confounded by G.E. Stahl
Georg Ernst Stahl
Georg Ernst Stahl was a German chemist and physician.He was born at Ansbach. Having graduated in medicine at the University of Jena in 1683, he became court physician to Duke Johann Ernst of Sachsen Weimar in 1687...
. Marggraf showed that alumina is one of the constituents of alum, but that this earth possesses peculiar properties, and is one of the ingredients in common clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
. He also showed that crystals of alum can be obtained by dissolving alumina in sulfuric acid and evaporating the solutions, and when a solution of potash
Potash
Potash is the common name for various mined and manufactured salts that contain potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era...
or ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
is dropped into this liquid, it immediately deposits perfect crystals of alum.
Torbern Bergman
Torbern Bergman
Torbern Olof Bergman was a Swedish chemist and mineralogist noted for his 1775 Dissertation on Elective Attractions, containing the largest chemical affinity tables ever published...
also observed that the addition of potash or ammonia made the solution of alumina in sulfuric acid crystallize, but that the same effect was not produced by the addition of soda or of lime
Lime (mineral)
Lime is a general term for calcium-containing inorganic materials, in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide. It is also the name for a single mineral of the CaO composition, occurring very rarely...
, and that potassium sulfate is frequently found in alum.
After M.H. Klaproth
Martin Heinrich Klaproth
Martin Heinrich Klaproth was a German chemist.Klaproth was born in Wernigerode. During a large portion of his life he followed the profession of an apothecary...
had discovered the presence of potassium in leucite
Leucite
Leucite is a rock-forming mineral composed of potassium and aluminium tectosilicate K[AlSi2O6]. Crystals have the form of cubic icositetrahedra but, as first observed by Sir David Brewster in 1821, they are not optically isotropic, and are therefore pseudo-cubic. Goniometric measurements made by...
and lepidolite
Lepidolite
Lepidolite Lepidolite Lepidolite (KLi2Al(Al,Si)3O10(F,OH)2 is a lilac-gray or rose-colored phyllosilicate mineral of the mica group that is a secondary source of lithium. It is associated with other lithium-bearing minerals like spodumene in pegmatite bodies. It is one of the major sources of the...
, it occurred to L.N. Vauquelin
Louis Nicolas Vauquelin
Nicolas Louis Vauquelin , was a French pharmacist and chemist.-Early life:Vauquelin was born at Saint-André-d'Hébertot in Normandy, France. His first acquaintance with chemistry was gained as laboratory assistant to an apothecary in Rouen , and after various vicissitudes he obtained an introduction...
that it was probably an ingredient likewise in many other mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s. Knowing that alum cannot be obtained in crystals without the addition of potash
Potash
Potash is the common name for various mined and manufactured salts that contain potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era...
, he began to suspect that this alkali constituted an essential ingredient in the salt, and in 1797 he published a dissertation demonstrating that alum is a double salt
Double salt
Double salts are salts containing more than one cation or anion. They form when more than one salt is dissolved in a liquid and when together they crystallize in a regular pattern. A well-known double salt is alum containing two cations and a sulfate anion...
, composed of sulfuric acid, alumina, and potash. Soon after, J.A. Chaptal
Jean-Antoine Chaptal
Jean-Antoine Claude, comte Chaptal de Chanteloup was a French chemist and statesman. He established chemical works for the manufacture of the mineral acids, soda and other substances...
published the analysis of four different kinds of alum, namely, Roman alum, Levant alum, British alum and alum manufactured by himself. This analysis led to the same result as Vauquelin.
Early uses in industry
EgyptiansEgyptians
Egyptians are nation an ethnic group made up of Mediterranean North Africans, the indigenous people of Egypt.Egyptian identity is closely tied to geography. The population of Egypt is concentrated in the lower Nile Valley, the small strip of cultivable land stretching from the First Cataract to...
reportedly used the coagulant alum as early as 1500 BC to reduce the visible cloudiness (turbidity
Turbidity
Turbidity is the cloudiness or haziness of a fluid caused by individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality....
) in the water. Alum was imported into England mainly from the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...
, and, from the late 15th century onwards, the Papal States
Papal States
The Papal State, State of the Church, or Pontifical States were among the major historical states of Italy from roughly the 6th century until the Italian peninsula was unified in 1861 by the Kingdom of Piedmont-Sardinia .The Papal States comprised territories under...
for hundreds of years. Its use there was as a dye
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
-fixer (mordant
Mordant
A mordant is a substance used to set dyes on fabrics or tissue sections by forming a coordination complex with the dye which then attaches to the fabric or tissue. It may be used for dyeing fabrics, or for intensifying stains in cell or tissue preparations. The term mordant comes from the Latin...
) for wool
Wool
Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits....
(which was one of England's primary industries, the value of which increased significantly if dyed). These sources were unreliable, however, and there was a push to develop a source in England especially as imports from the Papal States were ceased following the excommunication
Excommunication
Excommunication is a religious censure used to deprive, suspend or limit membership in a religious community. The word means putting [someone] out of communion. In some religions, excommunication includes spiritual condemnation of the member or group...
of King Henry VIII. 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
Yorkshire
Yorkshire is a historic county of northern England and the largest in the United Kingdom. Because of its great size in comparison to other English counties, functions have been increasingly undertaken over time by its subdivisions, which have also been subject to periodic reform...
to process the shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
which contained the key ingredient, aluminium sulfate
Aluminium sulfate
Aluminium sulfate, alternatively spelt aluminum sulfate, aluminium sulphate, or aluminum sulphate; is a chemical compound with the formula Al23...
, and made an important contribution to the Industrial Revolution
Industrial Revolution
The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...
. One of the oldest historic sites for the production of alum from shale and human urine are the Peak alum works in Ravenscar
Ravenscar, North Yorkshire
Ravenscar is a coastal village in the Scarborough district of North Yorkshire, England, approximately north of Scarborough. It is within the civil parish of Staintondale....
, North Yorkshire.
Alum (known as turti/sphatika in local Indian languages) was also used for water treatment
Water treatment
Water treatment describes those processes used to make water more acceptable for a desired end-use. These can include use as drinking water, industrial processes, medical and many other uses. The goal of all water treatment process is to remove existing contaminants in the water, or reduce the...
by Indians for thousands of years. Ayurveda describes sphatika as an astringent, haemostatic, antiseptic. It has anti-inflammatory, anti-pyretic and antibiotic properties. Sphatika’s use in treating tonsillitis has been referred in ancient Ayurvedic texts. Sphatika is used internally as well as externally.
From alunite
In order to obtain alum from aluniteAlunite
Alunite is a sulfate mineral that was first observed in the 15th century in Monti della Tolfa, north of Rome, where it was mined for the manufacture of alum. First called aluminilite by J.C. Delamétherie in 1797, this name was contracted by François Beudant in 1824 to alunite.Distinct crystals of...
, 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 and sulfuric acid, the
liquor decanted, and the alum allowed to crystallize. The alum schists employed in the manufacture of alum are mixtures of iron pyrite
Pyrite
The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
, aluminium silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
and various bituminous substances, and are found in upper Bavaria
Bavaria
Bavaria, formally the Free State of Bavaria is a state of Germany, located in the southeast of Germany. With an area of , it is the largest state by area, forming almost 20% of the total land area of Germany...
, Bohemia
Bohemia
Bohemia is a historical region in central Europe, occupying the western two-thirds of the traditional Czech Lands. It is located in the contemporary Czech Republic with its capital in Prague...
, Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
, and Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
. These are either roasted or exposed to the weathering
Weathering
Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...
action of the air. In the roasting process, sulfuric acid is formed and acts on the clay to form aluminium sulfate, a similar condition of affairs being produced during weathering. The mass is now systematically extracted with water, and a solution of aluminium sulfate of specific gravity
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
1.16 is prepared. This solution is allowed to stand for some time (in order that any calcium sulfate
Calcium sulfate
Calcium sulfate is a common laboratory and industrial chemical. In the form of γ-anhydrite , it is used as a desiccant. It is also used as a coagulant in products like tofu. In the natural state, unrefined calcium sulfate is a translucent, crystalline white rock...
and basic ferric sulfate may separate), and is then evaporated until ferrous sulfate crystallizes on cooling; it is then drawn off and evaporated until it attains a specific gravity of 1.40. It is now allowed to stand for some time, decanted from any sediment, and finally mixed with the calculated quantity of potassium sulfate, well agitated, and the alum is thrown down as a finely divided precipitate of alum meal. If much iron should be present in the shale then it is preferable to use potassium chloride in place of potassium sulfate.
From clays or bauxite
In the preparation of alum from clayClay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
s or from bauxite
Bauxite
Bauxite is an aluminium ore and is the main source of aluminium. This form of rock consists mostly of the minerals gibbsite Al3, boehmite γ-AlO, and diaspore α-AlO, in a mixture with the two iron oxides goethite and hematite, the clay mineral kaolinite, and small amounts of anatase TiO2...
, the material is gently calcined, then mixed with sulfuric acid and heated gradually to boiling; it is allowed to stand for some time, the clear solution drawn off and mixed with acid potassium sulfate and allowed to crystallize. When cryolite
Cryolite
Cryolite is an uncommon mineral identified with the once large deposit at Ivigtût on the west coast of Greenland, depleted by 1987....
is used for the preparation of alum, it is mixed with calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
and heated. By this means, sodium aluminate is formed; it is then extracted with water and precipitated
Precipitation (chemistry)
Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...
either by sodium bicarbonate
Sodium bicarbonate
Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...
or by passing a current of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
through the solution. The precipitate is then dissolved in sulfuric acid, the requisite amount of potassium sulfate added and the solution allowed to crystallize.
Types
Potash alum
Main article: Potash alumAluminum potassium sulfate, potash alum, KAl(SO4)2·12H2O is used as an astringent and antisepsis in various food preparation processes such as pickling and fermentation and as a flocculant for water purification among other things. A common method of producing potash alum is leaching
Leaching (chemical science)
Leaching is the process of extracting minerals from a solid by dissolving them in a liquid, either in nature or through an industrial process. In the chemical processing industry, leaching has a variety of commercial applications, including separation of metal from ore using acid, and sugar from...
of alumina from bauxite
Bauxite
Bauxite is an aluminium ore and is the main source of aluminium. This form of rock consists mostly of the minerals gibbsite Al3, boehmite γ-AlO, and diaspore α-AlO, in a mixture with the two iron oxides goethite and hematite, the clay mineral kaolinite, and small amounts of anatase TiO2...
which is then reacted with potassium sulfate
Potassium sulfate
Potassium sulfate is a non-flammable white crystalline salt which is soluble in water...
. As a naturally occurring mineral potash alum is known as kalunite. Other potassium aluminium sulfate minerals are alunite
Alunite
Alunite is a sulfate mineral that was first observed in the 15th century in Monti della Tolfa, north of Rome, where it was mined for the manufacture of alum. First called aluminilite by J.C. Delamétherie in 1797, this name was contracted by François Beudant in 1824 to alunite.Distinct crystals of...
(KAl(SO4)2·2Al(OH)3) and kalinite
Kalinite
Kalinite is a fibrous monoclinic type of alum distinct from isometric potassium alum, named in 1868. Its name comes from Kalium which is the Latin name for potassium, hence its chemical symbol, "K"...
(KAl(SO4)2·11H2O).
The molecular weight of potash alum is 474 g/mole.
Soda alum
Main article: Soda alumSoda alum
Sodium aluminium sulfate, NaAl2·12H2O or Na2SO4·Al23·24H2O, also known as soda alum or sodium alum, is a form of alum used in the acidity regulator of food as well as in the manufacture of baking powder...
Soda alum, NaAl(SO4)2·12H2O, mainly occurs in nature as the mineral mendozite
Mendozite
Mendozite is a sulfate mineral, one of the alum series, with formula NaAl2·11H2O. It is a hydrated form of sodium aluminium sulfate ....
. It is very soluble in water, and is extremely difficult to purify. In the preparation of this salt, it is preferable to mix the component solutions in the cold, and to evaporate them at a temperature not exceeding 60 °C. 100 parts of water dissolve 110 parts of sodium alum at 0 °C, and 51 parts at 16 °C. Soda alum is used in the acidulent
Acidulated
Acidulated describes something that has been rendered acid or sour.* Acidulated drops are an old-fashioned candy similar to modern lemon and lime drops....
of food as well as in the manufacture of baking powder.
Ammonium alum
Main article: Ammonium alumAmmonium alum
Ammonium aluminium sulfate, also known as ammonium alum is a white crystalline double sulfate usually encountered as the dodecahydrate, formula Al2·12H2O. It is used in small amounts in a variety of niche applications...
Ammonium alum, NH4Al(SO4)2·12H2O, a white crystalline double sulfate of aluminium, is used in water purification, in vegetable glues, in porcelain cements, in deodorants (though potassium alum is more commonly used), in tanning, dyeing and in fireproofing textiles.
Chrome alum
Main article: Chrome alumChrome alum
Chrome alum or Chromium potassium sulfate is the potassium double sulfate of chromium. Its chemical formula is KCr2 and it is commonly found in its dodecahydrate form as KCr2·12. It was formerly used in leather tanning....
Chrome alum, KCr(SO4)2·12H2O, a dark violet crystalline double sulfate of chromium and potassium, was used in tanning
Tanning
Tanning is the making of leather from the skins of animals which does not easily decompose. Traditionally, tanning used tannin, an acidic chemical compound from which the tanning process draws its name . Coloring may occur during tanning...
.
Selenate-containing alums
Alums are also known that contain seleniumSelenium
Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...
in place of sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
in the sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
anion, making selenate
Selenate
The selenate ion is SeO42–.Selenates are analogous to sulfates and have similar chemistry. They are highly soluble in aqueous solutions at ambient temperatures....
(SeO42-) instead. They are called selenium- or selenate-alums. They are strong oxidizing agent
Oxidizing agent
An oxidizing agent can be defined as a substance that removes electrons from another reactant in a redox chemical reaction...
s.
Aluminium sulfate
Aluminium sulfateAluminium sulfate
Aluminium sulfate, alternatively spelt aluminum sulfate, aluminium sulphate, or aluminum sulphate; is a chemical compound with the formula Al23...
is referred to as papermaker's alum. Although reference to this compound as alum is quite common in industrial communication, it is not regarded as technically correct. Its properties are quite different from those of the set of alums described above. Most industrial flocculation done with alum is actually aluminum sulfate.
Solubility
The solubility of the various alums in water varies greatly, sodium alum being readily soluble in water, while caesiumCaesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
and rubidium
Rubidium
Rubidium is a chemical element with the symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group. Its atomic mass is 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in group 1, such as very rapid...
alums are only sparingly soluble. The various solubilities are shown in the following table.
- At temperature T, 100 parts water dissolve:
T |
Ammonium Alum |
Potassium Alum |
Rubidium Alum |
Caesium Alum |
|---|---|---|---|---|
0 °C |
2.62 |
3.90 |
0.71 |
0.19 |
10 °C |
4.50 |
9.52 |
1.09 |
0.29 |
50 °C |
15.9 |
44.11 |
4.98 |
1.235 |
80 °C |
35.20 |
134.47 |
21.60 |
5.29 |
100 °C |
70.83 |
357.48 |
Crystal chemistry
Double sulfateSulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
s with the general formula A2SO4·B2(SO4)3·24H2O, are known where A is a monovalent cation such as sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
, potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
, rubidium
Rubidium
Rubidium is a chemical element with the symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group. Its atomic mass is 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in group 1, such as very rapid...
, caesium
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
, or thallium(I)
Thallium
Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray poor metal resembles tin but discolors when exposed to air. The two chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861 by the newly developed method of flame spectroscopy...
, or a compound cation such as ammonium
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...
(NH4+), methylammonium
Methylamine
Methylamine is the organic compound with a formula of CH3NH2. This colourless gas is a derivative of ammonia, but with one H atom replaced by a methyl group. It is the simplest primary amine. It is sold as a solution in methanol, ethanol, THF, and water, or as the anhydrous gas in pressurized...
(CH3NH3+), hydroxylammonium
Hydroxylamine
Hydroxylamine is an inorganic compound with the formula NH2OH. The pure material is a white, unstable crystalline, hygroscopic compound. However, hydroxylamine is almost always provided and used as an aqueous solution. It is used to prepare oximes, an important functional group. It is also an...
(HONH3+) or hydrazinium (N2H5+), B is a trivalent metal ion, such as aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, chromium
Chromium
Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
, titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
, manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
, vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
, iron (III)
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, cobalt(III)
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
, gallium
Gallium
Gallium is a chemical element that has the symbol Ga and atomic number 31. Elemental gallium does not occur in nature, but as the gallium salt in trace amounts in bauxite and zinc ores. A soft silvery metallic poor metal, elemental gallium is a brittle solid at low temperatures. As it liquefies...
, molybdenum
Molybdenum
Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
, indium
Indium
Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...
, ruthenium
Ruthenium
Ruthenium is a chemical element with symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most chemicals. The Russian scientist Karl Ernst Claus discovered the element...
, rhodium
Rhodium
Rhodium is a chemical element that is a rare, silvery-white, hard and chemically inert transition metal and a member of the platinum group. It has the chemical symbol Rh and atomic number 45. It is composed of only one isotope, 103Rh. Naturally occurring rhodium is found as the free metal, alloyed...
, or iridium
Iridium
Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...
. The specific combinations of univalent cation, trivalent cation, and anion depends on the sizes of the ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s. For example, unlike the other alkali metal
Alkali metal
The alkali metals are a series of chemical elements in the periodic table. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, along with hydrogen. The alkali metals are lithium , sodium , potassium , rubidium , caesium , and francium...
s the smallest one, lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
, does not form alums, and there is only one known sodium alum. In some cases, solid solution
Solid solution
A solid solution is a solid-state solution of one or more solutes in a solvent. Such a mixture is considered a solution rather than a compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single homogeneous phase...
s of alums occur.
Alums crystallize in one of three different crystal structures. These classes are called α-, β- and γ-alums.
Related compounds
In addition to the alums, which are dodecahydrates, double sulfates and selenates of univalent and trivalent cations occur with other degrees of hydration. These materials may also be referred to as alums, including the undecahydrates such as mendoziteMendozite
Mendozite is a sulfate mineral, one of the alum series, with formula NaAl2·11H2O. It is a hydrated form of sodium aluminium sulfate ....
and kalinite
Kalinite
Kalinite is a fibrous monoclinic type of alum distinct from isometric potassium alum, named in 1868. Its name comes from Kalium which is the Latin name for potassium, hence its chemical symbol, "K"...
, hexahydrates such as guanidinium
Guanidine
Guanidine is a crystalline compound of strong alkalinity formed by the oxidation of guanine. It is used in the manufacture of plastics and explosives. It is found in urine as a normal product of protein metabolism. The molecule was first synthesized in 1861 by the oxidative degradation of an...
(CH6N3+) and dimethylammonium
Dimethylamine
Dimethylamine is an organic compound with the formula 2NH. This secondary amine is a colorless, flammable liquified gas with an ammonia-like odor. Dimethylamine is generally encountered as a solution in water at concentrations up to around 40%...
((CH3)2NH2+) "alums", tetrahydrates such as goldichite, monohydrates such as thallium plutonium sulfate and anhydrous alums (yavapaiites). These classes include differing, but overlapping, combinations of ions.
A pseudo alum is a double sulfate of the typical formula ASO4·B2(SO4)3·22H2O, where A is a divalent metal ion, such as cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
(wupatkiite), manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
(apjohnite), magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
(pickingerite) or iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
(halotrichite
Halotrichite
Halotrichite, also known as feather alum, is a highly hydrated sulfate of aluminium and iron. It is formed by the weathering and decomposition of pyrite commonly near or in volcanic vents. Its chemical formula is FeAl24·22H2O. It forms fibrous monoclinic crystals. The crystals are water...
or feather alum), and B is a trivalent metal ion.
A Tutton salt
Tutton's salt
Tutton's salts are a family of salts with the formula M2M'26 or M2M'26 . These materials are "double salts," which means that they contain two different cations, M+ and M'2+.-Examples and related compounds:...
is a double sulfate of the typical formula A2SO4·BSO4·6H2O, where A is a univalent cation, and B a divalent
Divalent
In chemistry, a divalent ion or molecule has a valence of two and thus can form two bonds with other ions or molecules. An older term for divalent is bivalent....
metal ion.
Double sulfates of the composition A2SO4·2BSO4, where A is a univalent cation and B is a divalent metal ion are referred to as langbeinite
Langbeinite
Langbeinite is a potassium magnesium sulfate mineral with formula: K2Mg23. Langbeinite crystallizes in the isometric - tetartoidal system as transparent colorless or white with pale tints of yellow to green and violet crystalline masses. It has a vitreous luster. The Mohs hardness is 3.5 to 4 and...
s, after the prototypical potassium magnesium sulfate.
In popular culture
Much use was made of the supposed properties of alum as a comedy gag in films, primarily in the 1920s and 1930s. In a typical situation it would be introduced by accident or intent into foodstuffs, with ingestion causing the victim's mouth to assume a tight pucker. Speech was usually difficult or impossible. In animation, cartoon physicsCartoon physics
Cartoon physics is a jocular system of laws of physics that supersedes the normal laws, used in animation for humorous effect. Normal physical laws are referential , but cartoon physics are preferential ....
could magnify the effect- the victim's head might shrink (as in the 1949 Bugs Bunny
Bugs Bunny
Bugs Bunny is a animated character created in 1938 at Leon Schlesinger Productions, later Warner Bros. Cartoons. Bugs is an anthropomorphic gray rabbit and is famous for his flippant, insouciant personality and his portrayal as a trickster. He has primarily appeared in animated cartoons, most...
cartoon Long-Haired Hare
Long-Haired Hare
Long-Haired Hare is a 1948 Warner Brothers Looney Tunes theatrical cartoon short released in 1949, directed by Chuck Jones and written by Michael Maltese. In addition to including the homophones "hair" and "hare", the title is also a pun on "longhairs", a characterization of classical music lovers...
) or the voice alter to a shrill squeak.
See also
- List of minerals
- Potash alum
- Soda alumSoda alumSodium aluminium sulfate, NaAl2·12H2O or Na2SO4·Al23·24H2O, also known as soda alum or sodium alum, is a form of alum used in the acidity regulator of food as well as in the manufacture of baking powder...
- Aluminium sulfateAluminium sulfateAluminium sulfate, alternatively spelt aluminum sulfate, aluminium sulphate, or aluminum sulphate; is a chemical compound with the formula Al23...
(Papermaker's Alum)