| Dictionary, Encyclopedia and Thesaurus - The Free Dictionary 1,504,655,952 visitors served. |
|
Dictionary/ thesaurus | Medical dictionary | Legal dictionary | Financial dictionary | Acronyms | Idioms | Encyclopedia | Wikipedia encyclopedia | ? |
alum |
Also found in: Dictionary/thesaurus, Medical, Acronyms, Wikipedia, Hutchinson | 0.06 sec. |
|
alum (ăl`əm), any one of a series of isomorphous double salts that are hydrated sulfates sulfate, chemical compound containing the sulfate (SO4) radical . Sulfates are salts or esters of sulfuric acid , H2SO4, formed by replacing one or both of the hydrogens with a metal (e.g., sodium) or a radical (e.g. ..... Click the link for more information. of a univalent cation (e.g., potassium, sodium, ammonium, cesium, or thallium) and a trivalent cation (e.g., aluminum, chromium, iron, manganese, cobalt, or titanium). The name alum commonly refers to potassium aluminum sulfate dodecahydrate, or potash alum, KAl(SO4)2·12H2O, a colorless-to-white, crystalline compound. It is used in water purification, leather tanning, mordant dyeing, as an astringent, and in baking powder; it occurs in nature as the mineral kalunite. Sodium aluminum sulfate, or soda alum, NaAl(SO4)2·12H2O, is also used in baking powder. Ammonium aluminum sulfate, or ammonia alum, NH4Al(SO4)2·12H2O, is used in tanning, in dyeing and fireproofing textiles, in vegetable glues and porcelain cements, and in water purification. Chromium potassium sulfate, or chrome alum, KCr(SO4)2·12H2O, is used as a mordant in dyeing, in tanning, and in photographic fixing baths to harden gelatin films and plates. Aluminum sulfate, Al2(SO4)3·18H2O, is also called alum. A pseudoalum is a double sulfate salt of a divalent cation (e.g., magnesium or calcium) and a trivalent cation (e.g., aluminum). alumInorganic compound, any of a class of hydrated double salts, usually consisting of aluminum sulfate, water of hydration (an essential part of the crystal makeup), and the sulfate of another element. The most important alums are those of potassium sulfate (potassium alum, or potash alum, K2SO4∙Al2(SO4)3∙24H2O), ammonium sulfate, and sodium sulfate. Alums occur naturally in various minerals and can be prepared and purified by crystallization from their solutions. Most are white crystals with an astringent, acid taste. They are used as paper-sizing agents, flocculating agents in water treatment, mordants in dyeing, and in pickles, baking powder, fire extinguishers, and medicines. alum 1. a colourless soluble hydrated double sulphate of aluminium and potassium used in the manufacture of mordants and pigments, in dressing leather and sizing paper, and in medicine as a styptic and astringent. Formula: K2SO4.Al2(SO4)3.24H2O 2. any of a group of isomorphic double sulphates of a monovalent metal or group and a trivalent metal. Formula: X2SO4.Y2(SO4)3.24H2O, where X is monovalent and Y is trivalent alum charm against evil eye. [Egyptian Folklore: Leach, 40] See : Protection How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
|
| ? Mentioned in | ? References in classic literature | ||
|---|---|---|---|
| The soil of this immense region is strongly impregnated with sulphur, copperas, alum, and glauber salts; its various earths impart a deep tinge to the streams which drain it, and these, with the crumbling of the banks along the Missouri, give to the waters of that river much of the coloring matter with which they are clouded. But it is time that we took our order, for methinks that between the Needle rocks and the Alum cliffs yonder I can catch a glimpse of the topmasts of the galleys. |
| Encyclopedia |
| Free Tools: |
For surfers:
Browser extension |
Word of the Day |
Help
For webmasters: Free content | Linking | Lookup box | Double-click lookup | Partner with us |
|---|