|
Search over 100 encyclopedias and dictionaries: |
Research categories | Follow us on Twitter |
Research categories
View all topics in the newsView all reference sources at Encyclopedia.com |
|||
phosphoric acid
phosphoric acid any one of three chemical compounds made up of phosphorus , oxygen, and hydrogen (see acids and bases ). The most common, orthophosphoric acid, H 3 PO 4 , is usually simply called phosphoric acid. Two molecules of it are formed by adding three molecules of water, H 2 O, to one molecule of phosphorus pentoxide (phosphoric anhydride, P 2 O 5 ). It occurs as rhombic crystals or as a viscous liquid; both are deliquescent. The crystals melt at about 42°C. It has specific gravity 1.834 at 18°C, is soluble in alcohol, and is very soluble in water. It is a tribasic acid and forms orthophosphate salts with either one, two, or all three of the hydrogens replaced by some other positive ion. When it is heated to about 225°C, it dehydrates to form pyrophosphoric acid, H 4 P 2 O 7 ; at still higher temperatures metaphosphoric acid, HPO 3 , is formed. Salts of pyrophosphoric acid are pyrophosphates; salts of metaphosphoric acid are metaphosphates. Phosphoric acid is prepared commercially by heating calcium phosphate rock with sulfuric acid; purer grades may be prepared by treating red phosphorus with nitric acid. It is used in pickling and rust-proofing metals, in acidifying jellies and beverages, and in preparing phosphate salts. |
|
|
Cite this article
"phosphoric acid." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "phosphoric acid." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1E1-phsphracid.html "phosphoric acid." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-phsphracid.html |
|
phosphoric acid
phosphoric acid Group of acids. Tetraoxophosphoric acid (H3PO4, formerly orthophosphoric acid) is a colourless liquid obtained by the action of sulphuric acid on phosphate rock (calcium phosphate); it is used in dental adhesives, flavoured syrups, fertilizers, soaps, detergents, and anticorrosive coatings for metals. Metaphosphoric acid (HPO3) is obtained by heating tetraoxophosphoric acid; it is used as a dehydrating agent. Heptaoxodiphosphoric (H4P2O7, formerly pyrophosphoric acid) is formed by moderately heating tetraoxophosphoric acid or by reacting phosphorus pentoxide (P2O5) with water; it is used as a catalyst and in metallurgy.
|
|
|
Cite this article
"phosphoric acid." World Encyclopedia. 2005. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "phosphoric acid." World Encyclopedia. 2005. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O142-phosphoricacid.html "phosphoric acid." World Encyclopedia. 2005. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-phosphoricacid.html |
|
phosphoric acid
phosphoric acid May be one of three types: orthophosphoric acid (H3PO4), metaphosphoric acid (HPO3), or pyrophosphoric acid (H4P2O7). Orthophosphoric acid and its salts are used as acidity regulators and in acid‐fruit‐flavoured beverages.
|
|
|
Cite this article
DAVID A. BENDER. "phosphoric acid." A Dictionary of Food and Nutrition. 2005. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. DAVID A. BENDER. "phosphoric acid." A Dictionary of Food and Nutrition. 2005. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O39-phosphoricacid.html DAVID A. BENDER. "phosphoric acid." A Dictionary of Food and Nutrition. 2005. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O39-phosphoricacid.html |
|
|
Search over 100 encyclopedias and dictionaries:
HighBeam™ Research, Inc. © Copyright 2012. All rights reserved.
The Encyclopedia.com advertising network includes:
