Precipitates product solubility

Solubility can often be decreased by using a nonaqueous solvent. A precipitate s solubility is generally greater in aqueous solutions because of the ability of water molecules to stabilize ions through solvation. The poorer solvating ability of nonaqueous solvents, even those that are polar, leads to a smaller solubility product. For example, PbS04 has a Ks of 1.6 X 10 in H2O, whereas in a 50 50 mixture of H20/ethanol the Ks at 2.6 X 10 is four orders of magnitude smaller. 

Magaldrate is prepared by precipitation from aqueous solutions of sodium or potassium aluminate and a magnesium salt under controlled conditions of concentration and temperature. The precipitated product is collected by filtration, washed to remove soluble by-products, and dried. 

Soluble sodium sibcate glass sobd and bquid (anhydrous). Excludes quantities consumed in the manufacture of meta-, ortho-, and sesquisibcates. Includes quantities consumed in the manufacture of glass powder, hydrated glasses, and precipitated products. Shipment figures include unspecified amounts shipped to other plants for the manufacture of meta-, ortho-, or sesquisibcates. 

Precipitate Formation Solubility Product Constant (ffsp)... 

Syn-sedimentary chemical deposits form by chemical and biochemical precipitation of valuable metal components carried in solution, concomitant with the formation of the enclosing sedimentary rock. The manner of such deposition depends on the concentration of the metal in the solvent, the solubility of the precipitating product, the solution chemistry, and the deposition environment. Iron, manganese, phosphorus, lead, zinc, sulfur and uranium are some of the elements that have formed economically valuable deposits by chemical precipitation during sedimentation. 

The thermodynamic feasibility of a reaction with precipitating products can be assessed by comparing the mass action ratio to the equilibrium constant of a reaction. This requires estimation of solubilities, using melting points of reactants in combination with the reaction equilibrium constant [39]. 

For charged products the situation is significantly different. For many reactions involving zwitterions, the presence of undissolved substrates did not lead to precipitated products in enzymatic synthesis reactions [11]. These observations are related to differences in the solubility properties of zwitterions as compared to acids, bases, or uncharged compounds. Because of the low concentration of the... 

A comparison of the synthesis of Z-Phe-Leu-NH2 in ten different solvents revealed that the highest overall yields could be expected in solvents where the substrate solubility is minimized. The highest yields in terms of solid product were found in solvents where both substrate and product solubility are minimized [45]. These simple rules may not hold when special factors apply, such as the formation of solid solvates. This may account for a few apparent exceptions, such as the product precipitation in dichloromethane of both a peptide and a sugar fatty acid ester [45, 63]. 

The direction of a reaction can be assessed straightforwardly by comparing the equilibrium constant (Keq) and the ratio of the product solubility to the substrate solubility (Zsat) [39]. In the case of the zwitterionic product amoxicillin, the ratio of the equilibrium constant and the saturated mass action ratio for the formation of the antibiotic was evaluated [40]. It was found that, at every pH, Zsat (the ratio of solubilities, called Rs in that paper) was about one order of magnitude greater in value than the experimental equilibrium constant (Zsat > Keq), and hence product precipitation was not expected and also not observed experimentally in a reaction with suspended substrates. The pH profile of all the compounds involved in the reaction (the activated acyl substrate, the free acid by-product, the antibiotic nucleus, and the product) could be predicted with reasonable accuracy, based only on charge and mass balance equations in combination with enzyme kinetic parameters [40]. 

Decrease in pH. After heating at 140°C for 20 min, the pH of milk has decreased to about 5.8 due to acid production from pyrolysis of lactose, precipitation of soluble calcium phosphate as Ca3(P04)2, with the release of H+, and dephosphorylation of casein with subsequent precipitation of the liberated phosphate as Ca3(P04)2 with the release of H+. The heat-induced precipitation of Ca3(P04)2 is partially reversible on cooling so that the actual pH of milk at 140°C at the point of coagulation is much lower than the measured value and is probably below 5.0. 

Since both halides precipitate, both solubility product requirements must be met at the same time. 

The above process is repeated ten times, the broths obtained are combined, the pH is adjusted to 6, the combined broths are filtered, and the resulting filtrate is extracted countercurrently at the rate of 128 gallons per hour with about the same rate of butanol, in a 12" diameter by 11 ft. high Karr extraction column. A water backwash of 0.2 times the butanol rate is employed at the top of the extraction column to minimize the carry-over of water soluble components. The butanol extract is concentrated to approximately a 5% solution which comprises the feed to the center of a 3" diameter by 20 ft. high Karr fractional liquid extraction column. This column is operated at a water to butanol ratio of about 10 to 1, and the butanol extract contains the product. The butanol extract is concentrated by evaporation to a solution or paste containing about 5 to about 20% ent solids then about 25 to about 50 volumes of n-hexane are added, and the resulting slurry filtered. The precipitated product is then vacuum-dried to give a solid compound. 

Preliming. A small amount of lime (0.12-0.3% CaO is added to the juice, increasing the juice pH from about 6.2 to 10.8-11.4. The lime reacts with nonsugar impurities in the juice to make insoluble precipitates and soluble products. Calcium carbonate in the form of recycled first carbonation sludge is added to provide colloid adsorption and stabilization. Temperature may be cool (50°C) or hot (80°C) depending on the factory design. Insoluble precipitates are formed quickly. Retention time is 15-30 minutes. 

For this precipitate the solubility product can be taken from Table 1.12 ... 

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