    
|
 Helping San Diego, California and beyond since 1997 |
|
|
Helping San Diego, California and beyond since 1997 |
Click here and add this page to your favorites!
|
Encyclopedia Britannica - Main :: ORC-PAI |
|
|
OXALIC ACID, 112 C203 .21120, one of the oldest known organic acids. Scheele prepared it by oxidizing sugar with nitric acid, and showed it to be identical with the acetosellic acid obtained from wood
wood
Oxalis
starch
The hydrated acid crystallizes in prisms which effloresce in air, and are readily soluble in water. It loses its water of crystallization at too C., and begins to sublime at about 150-160 C., whilst on heating to a still higher temperature it partially decomposes into carbon dioxide and formic acid, or into carbon dioxide. carbon Monoxide and water; the latterdecomposition being also brought about by heating oxalic acid with concentrated sulphuric acid. The anhydrous acid melts at 189.5 C. (E. Bamberger, Ber., 1888, 21, p. 1901) and is frequently used as a condensing agent. Phosphorus pentachloride decomposes it into carbon monoxide and dioxide, the reaction being the one generally applied for the purpose of preparing phosphorus oxychloride. When heated with glycerin to too C. it yields formic acid and carbon dioxide; above this temperature, allyl. alcohol is formed. Nascent hydrogen reduces it to glycollic acid. Potassium permanganate in acid solution oxidizes it to carbon dioxide and water; the manganese sulphate formed has a catalytic accelerating effect on the decomposition. Oxalic acid is very poisonous, and by reason of its great
wall
ordinary acid and neutral salts, a series of salts called quadroxalates is known, these being salts containing one molecule of acid salt, in combination with one molecule of acid, one of the most common being " salt of sorrel," KHC2 04 H2 C2 04.2H2O. The oxalates are readily decomposed on' heating, leaving a residue of carbonate, or oxide
Potassium ferrous oxalate, FeK2(C204)2H2O, is a strong reducing agent and is used as a photographic developer. Potassium ferric oxalate, FeK3(C204)3, is used in the preparation of platinotypes, owing to the fact that its solution is rapidly decomposed by sunligght, 2FeK2(C204)3=2FeK2(C204)2+K2C204+2CO2. Ethyl oxalate, (CO.002H5)2, prepared by boiling anhydrous oxalic acid with absolute alcohol, is a colourless liquid which boils at 186 C. Methyl oxalate (CO.00H3)2, which is prepared in a similar manner, is a solid melting at 54 C. It is used in the preparation of pure methyl alcohol. On treatment with zinc and alkyl iodides or with zinc alkyls they are converted into esters of hydroxy-dialkyl acetic acids. An impure oxalyl chloride, a liquid boiling at 7o C., has been obtained by the action of phosphorus pentachloride on ethyl oxalate. Oxamic acid, HO2CCONH2, is obtained on heating acid ammonium oxalate; by boiling oxamide with ammonia; and among the products produced when amino-acids are oxidized with potassium permanganate (J. T. Halsey, Zeit. f. physiol. Chem., 1898, 25, p. 325). It is a crystalline powder difficultly soluble in water and melting at 21o C. (with decomposition). Its ethyl ester, known as oxamaethane, crystallizes in rhombic plates which melt at 114-115'C. Phosphorus pentachloride converts it into cyan-carbonic ester, the ethyl oxamine chloride first formed being unstable: ROOC.CONH2 )ROOCC(C12)NH2>CNCOOR. Oximide,[CO]2NH, produced by the action of a mixture of phosphorus pentachloride and oxychloride on oxamic acid (H. Ost and A. Mente, Ber., 1886, 19, p. 3229), crystallizes in prisms, and when boiled with water is rapidly hydrolysed to oxamide and oxalic acid. Oxamide, (CONH2)2, is best pre-pared by the action of ammonia on the esters of oxalic acid. It is also obtained by the action of hydrogen peroxide on hydrocyanic acid, or of manganese dioxide and sulphuric acid on potassium cyanide. It is a white crystalline powder which is almost insoluble in cold water. It melts at 417419 C. (with decomposition) when heated in a sealed tube (A. Michael, Ber., 1895, 28, p. 1632). When heated with phosphorus pentoxide it yields cyanogen. It is readily hydrolysed by hot solutions of the caustic alkalis. Substituted oxamides are produced by the action of primary amines on ethyl oxalate. Semsoxamazide, H2NCOCONHNH2, is prepared by the action of hydrazine hydrate on oxamaethane (W. Keep and K. Unger, Ber. 1897, 30, p. 586). It crystallizes in plates which melt at 220221 C. (with decomposition). It is only slightly soluble in water, but is readily soluble in acids and alkalis. It reduces silver salts rapidly. It condenses with aldehydes and ketones to produce semioxamazones. End of Article: OXALIC ACID, 112 C203 If you wish, you can link directly to this article.
<a href="http://jcsm.org/StudyCenter/Encyclopedia/ORC_PAI/OXALIC_ACID_112_C203.html"> OXALIC ACID, 112 C203 </a> |
|
|
(Previous) OWOSSO |
(Next) OXALIS |
Jesus Christ Saves Ministries, P.O. Box 70696, Pasadena, CA 91117JCSM is a 501(c)(3), non-profit organization. Copyright © 1997-present. |
Free & Cheap Cell
Phones |
Cheap Long Distance
Phone Service Carriers |
Talk America Local Phone Service
|
Ztel & MCI - Unlimited Long Distance
Compare
Cell Phone Plans & Companies |
International Calling Cards & Prepaid Phone Cards |
Voice Over IP Broadband Internet Phone
Service | Wireless
Phone Plans & Cheap Cell Phones
|
_____________________________________________________________________________
