Aluminum hydroxide complex, soluble

Sucralfate, Sucralfate. 3.4.5.6-tctra-(polyhydn>xyalu-minum)-cr-i>-glucupyranusyl sulfate-2.3.4.5-tctra-(polyhj-druxyuluminum)-j D-fructofuranoside sulfate (Carafatc). is the aluminum hydroxide complex of the octasulfate ester ot sucrose. It is practically insoluble in water and soluble in strong acids and bases, it has a pK value between 0.43 anJ 1.19. 

Sucralfate is a salt of sucrose complexed to sulfated aluminum hydroxide. In water or acidic solutions it forms a viscous, tenacious paste that binds selectively to ulcers or erosions for up to 6 hours. Sucralfate has limited solubility, breaking down into sucrose sulfate (strongly negatively charged) and an aluminum salt. Less than 3% of intact drug and aluminum is absorbed from the intestinal tract the remainder is excreted in the feces. 

Adsorption isotherms, 178-190 Freundlich, 179 Langmuir, 183 S-type, 178-179 L-type, 178-179 C-type, 178-179 H-type, 178-179 Aerobic decomposition, 323 Alkalinity, 82—91 Definition, 88 Types of alkalinity, 82 Aluminosilicate clays, 102 Aluminum cation, 103, 160 Acidity, 160 Complexation, 160 Polymeric aluminum, 160 Exchangeable, 160,162 Hydrolysis, 69, 75 Solubility, 71 Soluble complexes, 69 Aluminum hydroxide, 78-80 Solubility, 78 pH effect, 79... 

Formation of Complex Ions.—In certain cases the solubility of a sparingly soluble salt is greatly increased, instead of being decreased, by the addition of a common ion a familiar illustration of this behavior is provided by the high solubility of silver cyanide in a solution of cyanide ions. Similarly, mercuric iodide is soluble in the presence of excess of iodide ions and aluminum hydroxide dissolves in solutions of alkali hydroxides. In cases of this kind it is readily shown by transference measurements that the silver, mercury or other cation is actually present in the solution in the form of a complex ion. The solubility of a sparingly soluble salt can be increased by the addition of any substance, whether it... 

Problem In order to present students with a cognitive conflict it is possible to precipitate a solid and to dissolve this solid by the same substance. One way is to add a small amount of sodium hydroxide solution to aluminum chloride solution aluminum hydroxide precipitates as a white solid. After that an excess of sodium hydroxide is added the white solid disappears because the soluble tetrahydroxide aluminum complex is formed. If this excess of hydroxide solution is added from the beginning, no precipitation occurs, the complex is just formed. 

The conclusion that polynuclear hydroxide complex ions do not constitute a significant part of the solute species of aluminum at equilibrium in the solutions studied here is in accord with the conclusions of Frink and Sawhney (4). The microcrystalline gibbsite itself is metastable in the sense that as crystals grow in size with longer aging time their solubility decreases. Although at equilibrium metastable species can be ignored, it can be so diflBcult to attain an equilibrium condition that the concept has little practical usefulness. 

A1(00CCH3)3) a white solid soluble in water. It is usually obtained as the dibasic salt, basic aluminum ethanoate, A1(0H)(CH3C00)2. It is prepared by dissolving aluminum hydroxide in ethanoic acid and is used extensively as a mordant in dyeing and as a size for paper and cardboard products. The solution is hydrolyzed and contains various complex aluminum-hydroxyl species and colloidal aluminum hydroxide. 

The chemistry of the precipitation of aluminum hydroxides and oxides is very complex (40). When the solubility is exceeded, gelatinous precipitates, which are found to be amorphous by X-ray diffraction, usually form initially. Al MAS NMR shows the predominance of octahedraUy coordinated Al ions in these amorphous hydroxides, as are present in the crystalline trihydroxides and oxyhydroxides. However, in the amorphous materials some pentacoordinated and tetracoordinated Al ions are also found (15). As discussed above, there are many different crystalline hydroxides or oxyhydroxides, and which of them will be formed depends on the conditions (4f). Primary factors are temperature and pH, as well as aging time however, the nature of the anions present and the possible presence of organic components (42,43) also play a role. At low temperature in an excess of water, the hydroxides are preferentially formed, specifically bayerite at pH values between 5.8 and 9 or gibbsite for pH values smaller than 5.8 or larger than 9. 

It is now clear that bioavailability varies with the form of Al. The chemical form of Al at the mucosal wall depends not only on the form ingested, but also on the pH, concentration of the dose, and the presence of dietary complexing factors such as citrate and F. Many experiments have been performed with soluble AICI3, which produces a low pH solution. If the pH is then raised, artificially or physiologically during entrance into the intestine, insoluble aluminum hydroxide will form unless alternative ligands... 

Aluminum ion may be precipitated from aqueous solution by addition of hydroxide ion, forming A1(0H)3. a large excess of hydroxide ion must not be added, however, because the precipitate of A1(0H)3 will redissolve to form a soluble alu-minum/hydroxide complex. How many grams of solid NaOH should be added to 10.0 mL of 0.250 M AICI3 to just precipitate all the aluminum ... 

Most metals will precipitate as the hydroxide in the presence of concentrated NaOH. Metals forming amphoteric hydroxides, however, remain soluble in concentrated NaOH due to the formation of higher-order hydroxo-complexes. For example, Zn and AP will not precipitate in concentrated NaOH due to the formation of Zn(OH)3 and Al(OH)4. The solubility of AP in concentrated NaOH is used to isolate aluminum from impure bauxite, an ore of AI2O3. The ore is powdered and placed in a solution of concentrated NaOH where the AI2O3 dissolves to form A1(0H)4T Other oxides that may be present in the ore, such as Fe203 and Si02, remain insoluble. After filtering, the filtrate is acidified to recover the aluminum as a precipitate of Al(OH)3. 

A commercial process which uses hydrothermal leaching on a large scale is the Bayer process for production of aluminum oxide (see Aluminum compounds). This process is used to extract and precipitate high grade alurninum hydroxide (gibbsite [14762-49-3]) from bauxite [1318-16-7] ore. The hydrothermal process step is the extraction step in which concentrated sodium hydroxide is used to form a soluble sodium aluminate complex ... 

The loaded organic phase is stripped of beryUium using an aqueous ammonium carbonate [506-87-6] solution, apparently as a highly soluble ammonium beryUium carbonate [65997-36-6] complex, (NH 4Be(C02)3. AU of the iron [7439-89-6] contained in the leach solution is coextracted with the beryUium. Heating the strip solution to about 70°C separates the iron and a smaU amount of coextracted aluminum as hydroxide or basic carbonate... 

Bauxite, the main aluminum ore, is a mixed oxide-hydroxide, A1(0)0H, contaminated with Si02, Fc2 O3, clay, and other hydroxide salts. To isolate the aluminumcontaining material, the ore is treated with a strongly basic solution, whose high hydroxide concentration causes the solid to dissolve as a soluble complex ion,... 

The Hydrolysis of Salts of Metals Other than the Alkalis and Alkaline Earths. The metal hydroxides other than the alkalis and alkaline earths are weak bases. Accordingly metal salts of strong acids, such as FeClg, CuSO, KA SOJo 12HoO (alum), etc., hydrolyze to produce acidic solutions the sour taste of these salts is characteristic. It is interesting that the hydrolysis of a metal salt need not produce the hydroxide of the metal, but may produce a soluble complex cation thus the hydrolysis of alum or of aluminum sulfate or nitrate takes place primarily according to the following equation ... 

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