Hydroxide, 43 aluminum

Aluminum hydroxide (C.P. or better) is dissolved with moderate heating in sodium iQ droxide solution (saturated in the cold) until saturation is attained. The solution is diluted with water to a density of 1.1, suction-filtered through hard filter paper, and stored for two weeks in a closed vessel. The mother liquor is decanted from the precipitate of Ai(OH) 3 formed. The residue is digested for several days with cold water and then washed with hot water until no alkaline reaction is detectable with litmus. The product is dried first over CaClg, then over PsOg. The entire preparation is carried out in Pyrex glassware. 

Aluminum hydroxide is precipitated from solution by a cold solution of (NH )aC03 the crystals are thoroughly washed on a leaf filter and added in small portions to a 50% NaOH solution until no further solution occurs. The greater part of the solution is filtered. The remainder, which contains a small quantity of un-dlssolved aluminum hydroxide, is used to seed the filtrate. Well-developed crystals of hydrargyllite form in about eight days. They are then washed free of alkali. 

Poor adsorptivity. Converted into boehmite (AlOOH) at 180 to 200°C. d (20°C) 2.424. 

Pure aluminum ribbon is cut into strips, degreased and rinsed with freshly distilled acetone. The pieces are covered with a layer of amalgam by a short dip in a O.IN solution of HgClg and thoroughly washed with distilled water, followed by a final rinsing with double-distilled water. The pieces are then transferred to a Pyrex flask closed off with a soda-lime tube, and covered with double-distilled water. White flakes of bayerite form after a few days. 

Most aluminum hydroxide is produced by treating bauxite with a hot, concentrated solution of sodium hydroxide 

Aluminum hydroxide. Red atoms are oxygen white atoms are hydrogen and turquoise atom is aluminum, publishers RESOURCE GROUP 

Aluminum hydroxide is an effective antacid because it is, chemically, a base. As such, it reacts with stomach acid (hydrochloric acid HC1), to reduce the symptoms of heartburn, upset stomach, acid indigestion, and gastritis, an inflammation of the stomach lining. The compound can also be used to treat peptic ulcers on a long-term basis. A peptic ulcer is an open sore in the lining of the stomach or the first part of the small intestine. 

Aluminum hydroxide also has a number of industrial applications, such as  

An additive for cosmetics, paper, plastics, and rubber to give the final product more bulk  

Primary raw material for aluminum hydroxide manufacture is bauxite 

Continuous digestion of bauxite with sodium hydroxide in autoclaves or tubular reactors at 140 to 250°C under pressure using the Bayer process 

The raw material for the manufacture of aluminum hydroxide is bauxite, a mineral with ca. 45 to 60% AI2O3 in the form of hydrargillite (gibbsite), bdhmite and diaspore with iron oxides or hydroxides, silica (as kaolinite) and titanium dioxide as minor constituents. The largest deposits are to be found in Africa and Australia. 

Bauxite is digested with sodium hydroxide under pressure and at high temperature using the Bayer process, whereupon soluble sodium aluminate is formed  

Upon cooling, the liquor becomes supersaturated and aluminum hydroxide precipitates out in a reversal of the formation reaction. The solution is seeded with solid aluminum hydroxide to increase the precipitation rate. The hydrargillite formed is filtered off and washed. A large part of it is mashed and returned as seed for the following precipitation and the rest is carefully dried. Coarse particulate aluminum hydroxide is obtained, which can be processed by grinding and sieving to particulate particle size fractions between 10 and 100 pm. 

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At the anode, a chemical oxidation reaction is bound to take place. In normal fixers, sulfite (SOj ) is oxidized and acid (H ) is released as a consequence of this oxidation. Due to the decrease of the sulfite concentration and the decrease in the pH, the fixing solution becomes unstable and sulfur precipitation starts to occur when the pH of the fixer decreases below 4.0. In the case of hardening fixers, there is also an upper limit to the pH, since aluminum-hydroxides starts to precipitate when the pH exceeds 5.0. 

Now the easy part -isolating your product. One of the most attractive features of this new synthesis is that the standard Ai/(Hg) amination mixture must be tediously filtered to separate the product from the spent aluminum hydroxide sludge at this point. The following remedies this most frustrating step and will probably give many a new outlook on the potential of the AI(Hg) reduction. 

The function, fitted to the measured values for the aluminum hydroxide tested, was in the form ... 

The third process involves careflil addition of aluminum hydroxide to fluorosiUcic acid (6) which is generated by fertilizer and phosphoric acid-producing plants. The addition of Al(OH)2 is critical. It must be added gradually and slowly so that the siUca produced as by-product remains filterable and the AIF. -3H20 formed is in the soluble a-form. If the addition of Al(OH)2 3H20 is too slow, the a-form after some time changes into the insoluble P-form. Then separation of siUca from insoluble P-AIF. -3H20 becomes difficult. 

The FD C certified colors are all water-soluble dyes, but can be transformed into insoluble pigments known as lakes by precipitating the dyes with alurninum, calcium, or magnesium salts on a substrate of aluminum hydroxide. The lakes are useful in appHcations that require color whereas in dry form, such as cake mixes, or where water may be present and bleeding is a problem, such as food packaging. FD C Red Lake No. 3 was deHsted in Febmary... 

Aluminum Hydroxide Gel. CoUoidal aluminum hydroxide [21645-51 -2] (Amphogel), AlOH, is a suspension. Each 100 g contain the... 

Aluminum hydroxide gel may be prepared by a number of methods. The products vary widely in viscosity, particle size, and rate of solution. Such factors as degree of supersaturation, pH during precipitation, temperature, and nature and concentration of by-products present affect the physical properties of the gel. 

Mag nesia. ndAlumina. Suspension. A mixture of salts, available as Maalox, Mylanta, Gelusil, and Aludrox, contains magnesium hydroxide [1309-42-8] Mg(OH)2, and variable amounts of aluminum oxide in the form of aluminum hydroxide and hydrated aluminum oxide, ie, 2.9—4.2% magnesium hydroxide and 2.0—2.4% aluminum oxide, Al O, for a mixture of 4.9—6.6% combined magnesium hydroxide and aluminum oxide. This mixture may contain a flavoring and antimicrobial agents in a total amount not to exceed 0.5% (see Aluminum compounds, aluminum oxide). 

Magaldrate is an antacid having somewhat more efficacy than aluminum hydroxide. It does not appear to disturb electrolyte balance or bowel function. 

Aluminum. All primary aluminum as of 1995 is produced by molten salt electrolysis, which requires a feed of high purity alumina to the reduction cell. The Bayer process is a chemical purification of the bauxite ore by selective leaching of aluminum according to equation 35. Other oxide constituents of the ore, namely siUca, iron oxide, and titanium oxide remain in the residue, known as red mud. No solution purification is required and pure aluminum hydroxide is obtained by precipitation after reversing reaction 35 through a change in temperature or hydroxide concentration the precipitate is calcined to yield pure alumina. 

Synthetic Marble. Synthetic marble-like resin products are prepared by casting or molding a highly filled monomer mixture or monomer—polymer symp. When only one smooth surface is required, a continuous casting process using only one endless stainless steel belt can be used (52,53). Typically on the order of 60 wt % inorganic filler is used. The inorganic fillers, such as aluminum hydroxide, calcium carbonate, etc, are selected on the basis of cost, and such properties as the translucence, chemical and water resistance, and ease of subsequent fabrication (54,55). 

Molten aluminum reacts violently with water [7732-18-5] and the molten metal should not be allowed to touch damp tools or containers. In finely divided powder form, aluminum also reacts with boiling water to form hydrogen and aluminum hydroxide [21645-51 -2], this reaction proceeds slowly in cold water. 

Aluminum hydroxide and aluminum chloride do not ionize appreciably in solution but behave in some respects as covalent compounds. The aluminum ion has a coordination number of six and in solution binds six molecules of water existing as [Al(H20)g]. On addition of a base, substitution of the hydroxyl ion for the water molecule proceeds until the normal hydroxide results and precipitation is observed. Dehydration is essentially complete at pH 7. 

Aluminum fluoride is also made by the reaction of fluosiUcic acid [16961 -83-4] H2SiFg, a by-product from phosphoric acid production (see Phosphoric ACID AND THE PHOSPHATES), and aluminum hydroxide from the Bayer process. 

The CAS registry Hsts 5,037 aluminum-containing compounds exclusive of alloys and intermetaUics. Some of these are Hsted in Table 1. Except for nepheline and alunite in the USSR and Poland, bauxite is the raw material for all manufactured aluminum compounds. The term bauxite is used for ores that contain economically recoverable quantities of the aluminum hydroxide mineral gibbsite or the oxide—hydroxide forms boehmite and diaspore. 

Further deprotonation, dehydration, and polymerization of monomers and dimers may yield ringlike stmctures of hydroxy—aluminum complexes (10). Coalescence of ring compounds into layers by further growth results in the formation of crystalline aluminum hydroxide at pH 6, the point of minimum aqueous solubiUty. 

In high caustic Bayer Hquor, Al(OH) 4 ions exist because there is not enough water to hydrate them. Aluminum hydroxide is capable of reacting as either an acid or a base (18). 

The aluminum containing compound having the largest worldwide market, estimated to be over 30 x 10 t in 1990, is metal grade alumina. Second, is aluminum hydroxide. In 1990 the market for Al(OH)2 should approach or exceed 3.5 million metric tons which is equivalent to 2.3 million tons on an alumina basis. The spHt between additive and feedstock appHcations for Al(OH)2 (16) is roughly 50 50. Additive appHcations include those as flame retardants (qv) in products such as carpets, and to enhance the properties of paper (qv), plastic, polymer, and mbber products. Significant quantities are also used in pharmaceuticals (qv), cosmetics (qv), adhesives (qv), poHshes (qv), dentifrices (qv), and glass (qv). 

Aluminum sulfate has largely replaced alums for the major appHcations as a sizing agent in the paper industry and as a coagulant to clarify municipal and industrial water suppHes. In terms of worldwide production, it ranks third behind alumina and aluminum hydroxide, with markets in excess of 3 x 10 t/yr (19). 

Aluminum chloride hexahydrate, AIQ 6H20, manufactured from aluminum hydroxide and hydrochloric acid [7647-01-0], HQ, is used in pharmaceuticals and cosmetics as a flocculant and for impregnating textiles. Conversion of solutions of hydrated aluminum chloride with aluminum to the aluminum chlorohydroxy complexes serve as the basis of the most widely used antiperspirant ingredients (20). 

Zeolites. A large and growing industrial use of aluminum hydroxide and sodium alurninate is the manufacture of synthetic zeoHtes (see Molecular sieves). ZeoHtes are aluminosiHcates with Si/Al ratios between 1 and infinity. There are 40 natural, and over 100 synthetic, zeoHtes. AH the synthetic stmctures are made by relatively low (100—150°C) temperature, high pH hydrothermal synthesis. For example the manufacture of the industriaHy important zeoHtes A, X, and Y is generaHy carried out by mixing sodium alurninate and sodium sHicate solutions to form a sodium alurninosiHcate gel. Gel-aging under hydrothermal conditions crystallizes the final product. In special cases, a small amount of seed crystal is used to control the synthesis. 

The hexahydrate of aluminum chloride is a deUquescent, crystalline soHd soluble in water and alcohol and usually made by dissolving aluminum hydroxide [21645-51 -2] A1(0H)2, ia concentrated hydrochloric acid. When the acid is depleted, the solution is cooled to 0 °C and gaseous hydrogen chloride is introduced. Crystalline aluminum chloride hexahydrate, AIQ 6H20, is precipitated, filtered from the Hquor, washed with ethyl ether, and dried. 

The class of compounds identified as basic aluminum chlorides [1327-41 -9] is used primarily ia deoderant, antiperspirant, and fungicidal preparations. They have the formula Al2(OH)g where x = 1 5, and are prepared by the reaction of an excess of aluminum with 5—15% hydrochloric acid at a temperature of 67—97°C (18). The same compounds are obtained by hydro1y2ing aluminum alkoxides with hydrochloric acid (19,20) (see Alkoxides, METAl). Basic aluminum chloride has also been prepared by the reaction of an equivalent or less of hydrochloric acid with aluminum hydroxide at 117—980 kPa (17—143 psi) (20). 

Aluminum bromide hexahydrate [7784-11-4] AIBr. 6H20, may be made by dissolving aluminum or aluminum hydroxide ia hydrobromic acid [10035-10-6] HBr. This white, crystalline soHd is precipitated from aqueous solution. 

Aluminum iodide [7884-23-8] AIL, is a crystalline soHd with a melting poiat of 191°C. The presence of free iodine ia the anhydrous form causes the platelets to be yellow or brown. The specific gravity of this soHd is 3.98 at 25°C. Aluminum iodide hexahydrate [10090-53-6] AIL -6H20, and aluminum iodide pentadecahydrate [65016-30-0], AIL -15H20, are precipitated from aqueous solution. They may be prepared by the reaction of hydroiodic acid [10034-85-2], HI, with aluminum or aluminum hydroxide. 

Aluminum nitrate nonahydrate is prepared by dissolving aluminum or aluminum hydroxide in dilute nitric acid, and crystaUi2ing the product from the resulting aqueous solution. It is made commercially from aluminous materials such as bauxite. Iron compounds may be extracted from the solution with naphthenic acids (21) before hydrate precipitation. In the laboratory it is prepared from aluminum sulfate and barium nitrate. 

The activated aluminas comprise a senes of nonequilibrium forms of partially hydroxylated aluminum oxide [1344-28-1], AI2O2. The chemical composition can be represented by Al20 2 ranges from about 0 to 0.8. They are porous soHds made by thermal treatment of aluminum hydroxide... 

The large majority of activated alumina products are derived from activation of aluminum hydroxide, rehydrated alumina, or pseudoboehmite gel. Other commerical methods to produce specialty activated aluminas are roasting of aluminum chloride [7446-70-0], AIQ calcination of precursors such as ammonium alum [7784-25-0], AlH2NOgS2. Processing is tailored to optimize one or more of the product properties such as surface area, purity, pore size distribution, particle size, shape, or strength. 

Rehydration Bonded Alumina. Rehydration bonded aluminas are agglomerates of activated alumina, which derive their strength from the rehydration bonding mechanism. Because more processing steps are involved in the manufacture, they are generally more expensive than activated aluminum hydroxides. On the other hand, rehydration bonded aluminas can be produced in a wider range of particle shape, surface area, and pore size distribution. 

The term alumina hydrates or hydrated aluminas is used in industry and commerce to designate aluminum hydroxides. These compounds are tme hydroxides and do not contain water of hydration. Several forms are known a general classification is shown in Figure 1. The most weU-defined crystalline forms ate the trihydroxides, Al(OH) gibbsite [14762-49-3], bayerite [20257-20-9], and nordstrandite [13840-05-6], In addition, two aluminum oxide—hydroxides, AIO(OH), boelimite [1318-23-6] and diaspote [14457-84-2], have been clearly defined. The existence of several other forms of aluminum hydroxides have been claimed. However, there is controversy as to whether they ate truly new phases or stmctures having distorted lattices containing adsorbed or intedameUar water and impurities. 

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