Calcium oxalate salt

A. Oxalic acid solutions are highly irritating and corrosive. Ingestion and absorption of oxalate cause acute hypocalcemia resulting from precipitation of the insoluble calcium oxalate salt. Calcium oxalate crystals may then deposit in the brain, heart, kidneys, and other sites, causing serious systemic damage. 

Ethylene glycol works very well as a m or ingredient in antifreeze but its use is not without problems. Just as ethanol may be oxidized to the carboxylic acid known as acetic acid, so may ethylene glycol s two hydroxyl groups be oxidized by liver enzymes known as alcohol dehydrogenases to give oxalic acid. At physiological pH, oxalic acid is converted to its calcium salt, calcium oxalate. 

When an ionic compound is dissolved in water, it usually goes into solution as the ions. When an excess of a slightly soluble ionic compound is mixed with water, an equihbrium occurs between the solid compound and the ions in the saturated solution. For the salt calcium oxalate, CaC204, you have the following equilibrium ... 

There have been two main approaches to this assay. The first is to precipitate the oxalic acid as its insoluble salt, calcium oxalate, over a period of 48 h and then to determine the concentration of this colorimetrically after reduction to glycollie acid, conver-... 

A Some calcium salts, such as calcium fluoride and calcium hydrogen phosphate, have beneficial uses, but another calcium salt, calcium oxalate (CaC204), can be harmful. The photo is a scanning electron microscope image of calcium oxalate crystals, a common type of kidney stone that can form in the human kidney. 

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. 

Crucibles fitted with permanent porous plates are cleaned by shaking out as much of the solid as possible, and then dissolving out the remainder of the solid with a suitable solvent. A hot 0.1 M solution of the tetrasodium salt of the ethylenediaminetetra-acetic acid is an excellent solvent for many of the precipitates [except metallic sulphides and hexacyanoferrates(III)] encountered in analysis. These include barium sulphate, calcium oxalate, calcium phosphate, calcium oxide, lead carbonate, lead iodate, lead oxalate, and ammonium magnesium phosphate. The crucible may either be completely immersed in the hot reagent or the latter may be drawn by suction through the crucible. 

Ash value normally designates the presence of inorganic salts e.g., calcium oxalate found naturally in the drug, as well as inorganic matter derived from external sources. The official ash values are of prime importance in examination of the purity of powdered drugs as enumerated below ... 

Step 2 Conversion of calcium salt to corresponding insoluble calcium oxalate, and... 

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. 

The oxalate, [Cr(NH3)4H20.Cl]C204, separates in violet-red crystals on the addition of potassium oxalate to a solution of the chloride. It is sparingly soluble in water, and the solution gives a precipitate of calcium oxalate with calcium chloride. A freshly prepared solution of the salt in nitric acid gives no precipitate with silver nitrate. The chlorine atom in the chloro-aquo-salts is within the complex, and hence silver chloride is not at first precipitated by silver nitrate on boiling with nitric acid and silver nitrate, however, chlorine is precipitated as silver chloride. 

Catalytic effects.—Within certain limits, the stimulating action exerted by the presence of hydrochloric acid upon the speed of inversion of cane sugar 28 is less the more dil. the acid. Thus, W. Ostwald found the velocity constant with a soln. containing a mol. of acid per 2 litres of soln. is 20 52 per 10 litres, 3 335 and per 100 litres, 0 3128. The action is favoured by the presence of neutral salts, and this the more, the lower the mol. wt. of the salt in the same family group of the periodic system. The temp, coeff. of the inversion is 17 92 at 100°, and. 0 04104 at 25°. W. Ostwald, R. Hopke, and H. Trey have likewise studied the accelerating influence of the acid on the hydrolysis of methyl and ethyl acetates. Similar studies have been made by W. Ostwald and A. Villiers on the hydrolysis of methyl and ethyl acetates, calcium oxalate, and ethyl bromide and iodide. 

Dissolution of Sparingly Soluble Salts. Obtain precipitates of calcium carbonate and calcium oxalate in test tubes by reacting the relevant salts. Decant the solutions and pour an acetic acid solution onto the moist precipitates. What happens Repeat the experiment, but use hydrochloric acid instead of the acetic acid. Write the equations of the chemical reactions in the molecular and net ionic forms. Explain the results obtained on the basis of the dissociation constants of the acids and the solubility product. 

Indicate the salts of calcium, strontium, and barium that are poorly soluble. How can you prove experimentally which of the calcium salts is the least soluble How does calcium oxalate react with acetic and hydrochloric acids How and why does the thermal... 

Calcium Oxalate. CaCtOj, white precipitate, insoluble in weak acids, but soluble in strong acids, formed by reaction of soluble calcium salt solution and ammonium oxalate solution. Solubility at I8°C 0.0056 g anhydrous salt per liter of saturated solution. 

Of nutrient chelates in the human diet, oxalates and phytules arc Ihe most common. Oxalic acid, found principally in spinach, rhubarb leaves, beet leaves, some fruits, and mushrooms, is u primary chelator of calcium. Oxalate present in pineapple, kiwifmil, and possibly in other foods, occurs as calcium oxalale. CaCiOj. This compound is in the form of needle-like crystals, known as raphidcs. which can produce painful sensations in the mouth when eaten raw. The effects of oxalic acid in the diet may he twofold. First, it forms strong chelates with dietary calcium, rendering the culcium unavailable for absorption and assimilation. Secondly, absorbed oxalic acid causes assimilated Ca to be precipitated as insoluble salts that accumulate in the renal glomeruli and contribute to the formation of renal calculi. 

Solubility of Salts.—The calcium salts of oxalic and tartaric acids are very sparingly soluble in cold water, calcium citrate is sparingly soluble in hot water. In some instances, as in the analysis of mixtures where an... 

Most kidney stones consist of insoluble calcium salts, such as calcium oxalate. 

Approximately two thirds of all renal stones contain calcium phosphate or calcium oxalate. Many patients with such stones exhibit a renal defect in calcium reabsorption that causes hypercalciuria. This can be treated with thiazide diuretics, which enhance calcium reabsorption in the distal convoluted tubule and thus reduce the urinary calcium concentration. Salt intake must be reduced in this setting, as excess dietary NaCl will overwhelm the hypocalciuric effect of thiazides. Calcium stones may also be caused by increased intestinal absorption of calcium, or they may be idiopathic. In these situations, thiazides are also effective, but should be used as adjunctive therapy with decreased calcium intake and other measures. 

---