Oxalic acid Calcium oxalate

Oxalic acid occurs in high concentrations in pineapple and rhubarb, among other plants, and is responsible for the sharpness of the fresh fruits. Ingestion of too much oxalic acid can cause gastroenteritis, commonly recognized as a stomach ache. A salt of oxalic acid, calcium oxalate, is the stuff of kidney stones. 

Disposition in the Body. Ethylene glycol is metabolised initially to glycoaldehyde and subsequently to lactic acid and oxalic acid. Calcium oxalate crystals are deposited in the kidneys and some oxalate may be excreted in the urine together with unchanged ethylene glycol. 

Representative Chemicals Oxalic acid Calcium oxalate Sodium oxalate... 

Anthracene Antimony Antimony trisulfide Barium carbonate Barium chlorate Barium nitrate Barium oxalate Boric acid Calcium carbonate Calcium oxalate Carbon black Charcoal Clay Copper... 

Euphorbia coraroides Thunb. E. lasiocaula Boiss. E. lunulata Bunge. E. pallasii Turcz. E. pekinensis Rupr. E. sampsoni Hance E. sieboldiana Moore et Decne. Da Ji (Peking spurge) (root) Euphorbon, euphorbias, butyric acid, calcium malate, calcium oxalate, vitamin C.48-50 Diuretic, emetic, emmenagogue, purgative. 

Human blood plasma Oxalic acid Calcium chloride Ammonium sulfate... 

A variety of crystals may be present in the urine, including uric acid, calcium oxalate, calcium phosphate, calcium magnesium ammonium pyrophosphate, and cystine. Many of these have a unique crystalline form which permits them to be identified with microscopy. 

Nephrolithiasis occurs in 10% to 25% of patients with gout. Factors that predispose individuals to uric acid nephrolithiasis include excessive urinary excretion of uric acid, an acidic urine, and a highly concentrated urine. The risk of renal calcuh approaches 50% in individuals whose renal excretion of uric acid exceeds 1100 mg/day. In addition to pure uric acid stones, hyperuricosuric individuals are at increased risk for mixed uric acid-calcium oxalate stones and pure calcium oxalate stones. Uric acid stones are usually small, round, and radiolucent. Uric acid stones containing calcium are radiopaque. Uric acid has a negative logarithm of the acid ioiuzation constant of 5.5. Therefore when the urine is acidic, uric acid exists primarily in the un-ionized, less soluble form. At a urine pH of 5.0, urine is saturated at a uric acid level of 15 mg/dL. When the urine pH is 7.0, the solubility of uric acid in urine is increased to 200 mg/dL. In patients with uric acid nephrolithiasis, urinary pH typically is less than 6.0 and frequently less than 5.5. When an acidic urine is saturated with uric acid, spontaneous precipitation of stones may occur. 

Carrot fiber, prepared as an alcohol-acetone insoluble residue of cell wall material, binds deoxycholate and chenodeoxycholate under physiological conditions with the release of protons. Removal of calcium pectate from this material by extraction with ammonium oxalate reduces the capacity of carrot fiber to bind bile acids. Calcium carboxymethyl cellulose exhibits similar binding activity, whereas free carboxymethyl cellulose shows no binding. Calcium pectate prepared from citrus pectin and dissolved in water was found to bind bile acids under conditions used with carrot fiber. These results suggest that binding occurs through formation of salt linkage between calcium pectate in the cell wall residue and a bile acid. 

Calcium Oxalate. Ethanedioic acid calcium salt... 

Calcium oxalate EiNECS 209-260-1 Ethanedioic acid, calcium salt (1 1) Oxalic acid, calcium salt (1 1). Cubic crystals d = 2.2 insoluble in H2O, AcOH, soluble in dilute HCI, HNOs-... 

Osmose K-33 Wood Preservative 982 Oxalic acid, calcium salt (1 1) 633... 

It is stated that the reaction is not given by sugars, citric, succinic, malic, or oxalic acids. Racemic tartrates give a coloration of half the intensity of the 1-tartaric acid. Calcium and phosphate apparently disturb the determination. Since a high number of substances give colored complexes with iron(III) ions, selectivity of the test is given by the ability of the substance to be examined to behave exactly as expected in the sequence of procedures. It is not possible to make a list of compoxmds tiiat could cause false positive reactions. 

Pathologists distinguish uric acid, calcium oxalate, ammonium magnesium phosphate, cysteine, and other types of stones. Reference to a specific mineral or biochemical compound concerns only that compound present in the largest amount, because in addition to the major compound, the stone contains other chemicals the nature of these chemicals will be discussed later. 

Urinary excretion of uric acid, oxalic acid, calcium, phosphate, hydroxyproline and cAMP was higher in patients with renal stones than that observed in patients without nephrolithiasis, but the difference was not statistically significant. 

Oxalic Acid 45 140 60 - E - E slurry. 35% sulluric acid, calcium oxalate, calcium sulfate. pH 1, moderate aeration... 

Caldum chloride test. Add CaCl2 solution to a neutrai solution of an oxalate a white precipitate of calcium oxalate is formed, insoluble in acetic acid, but soluble in dil. HCl. 

Eluorspar assay may be completed by fluoride determination alone, because the mineralogical grouping rarely iacludes fluorine minerals other than fluorite. Calcium can be determined as oxalate or by ion-selective electrodes (67). SiUca can be determined ia the residue from solution ia perchloric acid—boric acid mixture by measuriag the loss ia weight on Aiming off with hydrofluoric acid. Another method for determining siUca ia fluorspar is the ASTM Standard Test Method E463-72. 

Of nutrient chelates in the human diet, oxalates and phytates are the most common. OxaUc acid (8), found principally in spinach, rhubarb leaves, beet leaves, some fmits, and mushrooms, is a primary chelator of calcium. Oxalate present in pineapple, kiwifmit, and possibly in other foods, occurs as calcium... 

Ftiedel-Crafts acetylation of cyclohex ibenzene gave 4-cyclohexylacetophenone which was used as an iatermediate for the preparation of 2,4-dioxo-4-substituted-l-butanoic acid detivatives useful ia treating utinary tract calcium oxalate lithiasis (98). 

The sodium formate process is comprised of six steps (/) the manufacture of sodium formate from carbon monoxide and sodium hydroxide, (2) manufacture of sodium oxalate by thermal dehydrogenation of sodium formate at 360°C, (J) manufacture of calcium oxalate (slurry), (4) recovery of sodium hydroxide, (5) decomposition of calcium oxalate where gypsum is produced as a by-product, and (6) purification of cmde oxahc acid. This process is no longer economical in the leading industrial countries. UBE Industries (Japan), for instance, once employed this process, but has been operating the newest diaLkyl oxalate process since 1978. The sodium formate process is, however, still used in China. 

Quantitative Analysis. OxaUc acid is precipitated as calcium oxalate from a solution containing oxaUc acid, and the calcium oxalate obtained is then weighed. If there are no organic substances other than oxaUc acid present, oxaUc acid can be titrated quantitatively with potassium permanganate. 

The common treatment methods are acidification, neutralization, and incineration. When oxahc acid is heated slightly in sulfuric acid, it is converted to carbon monoxide, carbon dioxide, and water. Reaction with acid potassium permanganate converts it to carbon dioxide. Neutralization with alkahes, such as caustic soda, yields soluble oxalates. Neutralization with lime gives practically insoluble calcium oxalate, which can be safely disposed of, for instance, by incineration. 

Millet Jelly Production. Starch powder is heated together with oxahc acid and hydrolyzed to produce millet jelly. Oxahc acid functions as a hydrolysis catalyst, and is removed from the product as calcium oxalate. This apphcation is carried out in Japan. 

Calcium Oxalate. The monohydrate [5794-28-5], CaC2 04-H2 0, mol wt 128.10,is of importance principally as an intermediate in oxahc acid manufacture and in analytical chemistry it is the form in which calcium is frequentiy quantitatively isolated. Its solubihty in water is very low, lower than that of the other aLkahne-earth oxalates. The approximate solubihties of this and several related salts are indicated in Table 6. 

---