Calcium salts, purification

Additional phosphonic acid is derived from by-product streams. In the manufacture of acid chlorides from carboxyUc acids and PCl, phosphonic acid or pyrophosphonic acid is produced, frequentiy with copious quantities of yellow polymeric LOOP. Such mixtures slowly evolve phosphine, particularly on heating, and formerly were a disposal problem. However, purification of this cmde mixture affords commercial phosphonic acid. By-product acid is also derived from the precipitate of calcium salts in the manufacture of phosphinic acid. As a consequence of the treatments of the salt with sulfuric acid, carbonate is Hberated as CO2 and phosphonic acid goes into solution. 

Salts of Organic Acids. Calcium salts of organic acids may be prepared by reaction of the carbonate hydroxide and the organic acid (9). Calcium lactate [814-80-2] is an iatermediate ia the purification of lactic acid from fermentation of molasses. Calcium soaps, soaps of fatty acids, ate soluble ia hydrocarbons, and are useful as waterproofing agents and constituents of greases (9). 

Of the removal processes that have attained commercial status, the current favorite employs a shiny of lime or limestone. The activity of the reagent is promoted by the addition of small amounts of carboxylic acids such as adipic acid. The gas and the shiny are contacted in a spray tower. The calcium salt is discarded. A process that employs aqueous sodium citrate, however, is suited for the recoveiy of elemental sulfur. The citrate solution is regenerated and recycled. (Kohl and Riesenfeld, Gas Purification, Gulf, 1985, p. 356.)... 

Fructose-1,6-diphosphate (trisodium sait) [38099-82-0] M 406.1, pKj 6.14, pK 6.93 (free acid). For purification via the acid strychnine salt, see Neuberg, Lustig and Rothenberg [Arch Biochem 3 33 1943]. The calcium salt can be partially purified by soln in ice-cold M HCl (Ig per lOmL) and repptn by dropwise addition of 2M NaOH the ppte and supernatant are heated on a boiling water bath for a short time, then filtered and the ppte is washed with hot water. The magnesium salt can be pptd from cold aqueous soln by adding four volumes of EtOH. 

Of some interest is the ability of 3-acyltetramic acid to form stable complexes with ions of transition metals, e.g. Cu2+, La3+, Sm3+, Eu +, Gd3+, and boron complexes [1]. Indeed, examples are available in which the tetramic acid occurs naturally as magnesium or calcium salts. Methods of isolation or purification involving acidic solvents generate conditions that... 

It can be further purified by precipitation with calcium salts. During extraction and purification, some degradation of the polymer takes place and the preparations show varying degrees of polymerization ranging from 1000 to 10000. 

Chromatography on silica gel yielded 13.2 g racemate of lactone - trans-(+/-)-5-(4-fluorophenyl)-2-(l-methylethyl)-N,4-di-diphenyl-l-[2-(tetrahydro-4-hydroxy-6-oxo-2FI-pyran-2-yl)ethyl]-lFI-pyrrole-3-carboxamide. This racemate was divided by chiral synthesis which was made analogously the method in US Pat. No. 4,581,893. Then each isomer was saponificated with NaOFI and purificated by FIPLC. The calcium salt corresponding acid was prepared by reaction with 1 eq. of CaCl2-2Fi20 in water. 

Knowledge of the chemistry of the raw beet juice is important in controlling the phases of juice purification. The addition of increasing amounts of lime and carbon dioxide should precipitate pectinaceous materials and insoluble anions such as phosphate, sulfate, oxalate, and others, as calcium salts, cause alkaline degradation of invert sugar into lactic and other acids, and flocculation of colorants. Lime is also essential for promoting good fitration. 

Small quantities of calcium sulfate dihydrate are formed in the production or purification of organic acids such as citric, oxalic or tartaric acids by way of their calcium salts ... 

Electrodialysis uses stacks of pairs of anion- and cation-exchange membranes in deionizing water and in recovery of formic, acetic, lactic, gluconic, citric, succinic, and glutamic acids from their sodium and potassium salts in fermentation broths.114 This may have an advantage over processes that involve purification through calcium salts. Electrodialytic bipolar membranes have been used to recover concentrated mineral acids from dilute solution.115 They can be used to convert sodium chloride to hydrogen chloride and sodium hydroxide in a process that avoids the use of chlorine.116 Soy protein has been precipitated by... 

Purification of calcium salts-. Very pure calcium oxide, such as needed in the preparation of phosphorus, is obtained according to Tiede and Riemer in the following way ... 

The test ensures that the substance to be examined has a total content of calcium (Ca ), which is below the limit defined in the individual monograph. The calcium is like the rest of the alkaline-earth metals — a divalent cation. It forms soluble halogen and nitrate salts, whereas the carbonate, sulfate, phosphate, and oxalate are insoluble. Calcium is not toxic but on the contrary an essential mineral in the human diet. So, the main reason for limiting its presence in substances used in pharmaceuticals is that it could be used as a marker for insufficient reagent cleanup during synthesis of the substance. Some carboxylic acid, like lactic acid, is first precipitated as calcium salts upon which purification steps are then performed. After this the carboxylic acid can be reprecipitated as whatever salt needed. At the present reference to calcium is given in more than 100 monographs. 

Currently, (J )-pantothenic acid is industrially produced by conventional chemical synthesis and marketed as the calcium salt (calpan). The global market of calpan was valued at approximately 75 million US dollars in sales in 2005 with a world output over 10 000 ton. The key starting material for large-scale chemical processes is (J )-pantolactone. This molecule can be coupled with either calcium P-alanine to form (J )-pantothenate or with 3-aminopropanol to form panthenol, an important ingredient in skin and hair care consumer products. Purification of (7 )-pantolactone from racemic mixtures occurs by chemical or enzymatic racemic resolution [320, 321]. 

This salt is isolated by filtration in the final step, washed with water and acidified with sulfuric acid to liberate free lactic acid with formation of calcium sulfate as solids. When ammonia is used for the neutralization, the ammonium lactate is formed and directly converted into butyl lactate by esterification with n-butanol, as shown in Scheme 1.2. Here, the ammonia is recovered and recycled. The following distillation and hydrolysis of butyl lactate gives an aqueous lactic acid with high efficiency. The lactic acid obtained by this method has higher purity than that obtained by the calcium salt method. The technologies for the above lactic acid fermentation and purification have well been established, and the production of both D- and L-lactic acids is conducted industrially in a plant scale of 100000 ton year. ... 

The purification of pantothenic acid in the form of its calcium salt was eventually accomplished only, however, to the extent of obtaining about 10 mg of material of estimated 90% purity and larger amounts of material with less potency . Autolyzed beef liver was the source material and a prominent procedure involved a fractional distribution of brucine salts between water and chloroform. The extremely hydrophilic nature of the active compound was a serious drawback in its isolation even the brucine salt was a thousand times more soluble in water than in chloroform. 

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