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Anhydrous

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	Anhydrous
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	Topics Anhydrous Topic Home As a general term, a substance is said to be anhydrous if it contains no waterWater Water is a tasteless, odorless substance that is essential to all known forms of life and is known as the universal solve... . The way of achieving the anhydrous form differs from one substance to another. Solvents In many cases, the presence of water can prevent a reaction from happening, or form undesirable products. To prevent this, anhydrous solvents must be used when performing certain reactions. Examples of reactions requiring the use of anhydrous solvents are the Grignard reactionGrignard reaction The Grignard reaction is an organometallic chemical reaction involving alkyl- or aryl-magnesium halides, also called Gri... and the Wurtz reactionWurtz reaction The Wurtz reaction, named after Charles-Adolphe Wurtz, is a coupling reaction in organic chemistry, organometallic chemistry... . Solvents are commonly rendered anhydrous by boiling them in the presence of a hygroscopic substance; metallic sodiumSodium Sodium is a chemical element which has the symbol Na , atomic number 11, atomic mass 22.9898 g/mol, oxidation number +1.... is one of the most common metals used. Other methods include the addition of molecular sieveMolecular sieve A molecular sieve is a material containing tiny pores of a precise and uniform size that is used as an adsorbent for gases a... s or alkali bases such as potassium hydroxidePotassium hydroxide The chemical compound potassium hydroxide, sometimes known as caustic potash, 'potassa, 'potash lye, and ... or barium oxideBarium oxide Barium oxide is a white hygroscopic compound formed by the reaction of barium with oxygen.... . Column solvent purification devices (generally referred to as Grubb's columns) recently became available, reducing the hazards (water reactive substances, heat) from the classical dehydrating methods. Ionic crystals An example of anhydration can be seen in copper(II) sulfateCopper(II) sulfate Copper sulfate, the chemical compound with the formula CuSO4, is a common salt of copper.... . If the water of crystallizationWater of crystallization Water of crystallization is water that occurs in crystals but is not covalently bonded to a host molecule or ion.... is removed from blue crystals of copper (II) sulfate, a white powder (anhydrous copper(II) sulfate) is formed. The formula for anhydration of pentahydrate copper (II) sulfate (CuSO₄·5H₂O) is as follows: CuSO₄·5H₂O + heat ? CuSO₄ + 5H₂O Another example is in the heating of magnesium sulfateMagnesium sulfate align="right" border="1" cellspacing="0" cellpadding="3" style="margin: 0 0 0 0.5em; background: #FFFFFF; border-collapse: collaps... heptahydrate, MgSO₄·7H₂O. On heating, it undergoes the following reaction: MgSO₄·7H₂O + heat ? MgSO₄ + 7H₂O Gases Several substances that exist as gases at standard conditions of temperature and pressure are commonly used as concentrated aqueous solutions. To clarify that it is the gaseous form that is being referred to, the term anhydrous is prefixed to the name of the substance: gaseous ammoniaAmmonia Ammonia is a compound of nitrogen and hydrogen with the formula NH3.... is generally referred to as anhydrous ammonia to distinguish it from household ammonia, which is an ammonium hydroxideAmmonium hydroxide Ammonium hydroxide, although it doesn't exist as an isolable chemical compound, is a name sometimes given to an aqueous solu... aqueous solution. gaseous hydrogen chlorideHydrogen chloride Hydrogen chloride, also known under the name HCl, is a highly corrosive and toxic colorless gas that forms white fumes... is generally referred to as anhydrous to distinguish it from the more commonly used 37% w/w solution in water. See also Air-free techniqueAir-free technique Air-free techniques refer to a range of manipulations in the chemistry laboratory for the handling of compounds that are air...