Alumina Aluminum Oxide

Of the sorbents available on prepared layers, alumina is one of the most unique. It can be made into different forms so that it not only has the basic character, but also neutral and acidic versions. This allows a great versatility for selectivity where the acid, neutral, or basic character need not be controlled with buffers in the mobile phase, certainly a disadvantage if doing TLC-MS work lest a buffer interfere in some manner. It also is a complex sorbent with hydroxyl groups, partial positive and negative surface charges, onto which water is also attracted. Only TLC precoated 

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All reactions and manipulations were carried out under an inert atmosphere (N2 or Ar gas) using the Schlenk technique. Solvents were freshly distilled under an Ar atmosphere using the standard procedures (Na/BC/benzophenone or CaH2). Chromatography was performed on alumina (aluminum oxide, activity Il-IV(Merck art 1097). The H- and C-NMR spectra were recorded on a Bruker AC-200 spectrometer ( H, 200 MHz) and Nippon... 

Alumina, 2 345t 5 582. See also Activated alumina Aluminum oxide (alumina) Bauxite(s) Calcined alumina Fused alumina Tabular alumina in the activated catalyst layer, 10 41 adsorption capacity vs. years of service, 1 630... 

Alumina. Aluminum oxide (A2O3). A white powder available in several commercial grades—technical, high purity, and CP. Used as a catalyst and catalyst support. 

Several minerals containing zirconium were known in ancient times, one of which, jacinth, is mentioned several times in the Bible. It was not until 1789 that Martin Heinrich Klaproth (1743-1817), a German analytical chemist who also discovered uranium, identified zirconium after many others before him had failed. Klaproth analyzed the mineral jargoon (ZnSiO ), as did other scientists, and found that it contained 25% silica, 5% iron oxide, and 70% zirconia. The other scientists confused zirconia with alumina (aluminum oxide, Al O ). Klaproth used more refined techniques and correctly identified the element zirconium. 

Alpine glacier A glacier that forms and flows in a mountain valley (compare with continental glacier). Alumina Aluminum oxide. 

Aluminum is the most abundant metallic element in the earth s crust, comprising approximately 8% of the crust (Brusewitz 1984). Aluminum does not occur naturally in the metallic, elemental state, but rather occurs in combination with oxygen, silicon, fluorine, and other elements (Browning 1969 Dinman 1983 IARC 1984 NRC 1982). The most important raw material for the production of aluminum is bauxite, which contains 40-60% alumina (aluminum oxide) (Dinman 1983 IARC 1984). Other raw materials sometimes used in the production of aluminum include cryolite, aluminum fluoride, fluorspar, corundum, and kaolin minerals (Browning 1969 Dinman 1983 IARC 1984). 

Like many elements, aluminum s name derives from the Latin because the Roman Empire used two of its naturally occurring minerals, alum (a potassium-aluminum sulfate) and alumina (aluminum oxide). It was isolated in 1825 by H. C. Oersted after decades of suspicion that it existed. 

Fillers used in large quantities to reinforce plastics are alumina (aluminum oxide), calcium carbonate, calcium silicate, cellulose flock, cotton (different forms), short glass fiber, glass beads, glass spheres, graphite, iron oxide powder, mica, quartz, sisal, silicon carbide, dtanium oxide, and tungsten carbide. Choice of filler varies and depends to a great extent upon the requirements of the end item and method of fabrication. 

P-ALUMINA y-ALUMINA ALUMINUM OXIDE o-ALUMINUM OXIDE P-ALUMNUM OXIDE y-ALUAHNUM OXIDE ALUMINUM SESQUIOXIDE ALUMTE ALUNDUM BROCKMANN, ALUMINUM OXIDE CAB-O-GRIP COMPALOX DIALUMINUM TRIOXIDE DISPAL DOTMENT 324 FASERTON G 2 (OXIDE) KHP 2 LUCALOX MICROGRIT WCA... 

Early chemists did not study the jacinth stone very carefully. They thought it was another form of alumina (aluminum oxide). Alumina was a well-known mineral at the time. In fact, it was not until Klaproth undertook the study of the jacinth stone that he realized it contained a new element. Klaproth at first referred to the stone as Jargon of Ceylon. When he knew that he had found a new element, he suggested the name zirconium for it. 

OSHA permissible exposure limit Alpha alumina (aluminum oxide) 15mgm total dust, 5mgm respirable fraction. Aluminum as me-... 

SYNONYMS alumina, aluminum oxide, aluminum trioxide, aluminite... 

Synonyms/Trade Names Alumina, Aluminum oxide, Aluminum trioxide [Note a-Alumina is the main component of technical grade alumina. Corundum is natural AI2O3. Emery is an impure crystalline variety ofAl203.] ... 

ALUMINA - Aluminum oxide occasionally found as an impurity in water in very small amounts. 

Alumina Aluminum oxide (AI2O3) which is very hard (Mohs hardness is 9) and strong. Single crystals are called sapphire or ruby depending on color. Alumina is used to fabricate hip joint socket components or dental root implants. 

Aluminum oxide Aluminum oxide (2 3). See Alumina Aluminum oxide hydrate. SeeAluminum hydroxide Aluminum oxide silicate. SeeAluminum silicate Aluminum phosphate Aluminum phosphate tribasic. SeeAluminum orthophosphate... 

A typical thermally conductive epoxy system used as an adhesive, as well as for other purposes, has a thermal conductivity of 0.0026 cal/cm/sec/°C and a volume resistivity of 1.5 x 10 ohm.cm (1.5 x 10 ohm.m). Fillers include alumina (aluminum oxide), beryllia (beryllium oxide), other unspecified inorganic oxides, boron nitride, and silica. Boron nitride is an excellent choice as a thermally conductive filler except that its content reaches a maximum at about 40% by weight in epoxy resins. The resultant products are always thixotropic pastes. BerylUa powder has excellent thermal conductivity by itself, but when mixed with a resin binder its conductivity drops drastically. It is also highly toxic and high in cost. Alumina is a commonly used filler to impart thermal conductivity in resins. ... 

Electrometallurgy. A major application of electrochemical principles and techniques occurs in the manufecture of such metals as aluminum and titanium. Plentiful aluminum-containing bauxite ores exist in lai e deposits in several countries, but it yms not until electrochemical techniques were developed in the United States and France at the end of the nineteenth century that the cost of manufecturing this light metal was sufficiently reduced to make it a commercially valuable commodity. This commercial process involved the electrolysis of alumina (aluminum oxide) dissolved in fused cryolite (sodium aluminum fluoride). During the century that followed this process s discovery, many different uses for this lightweight metal ensued, from airplanes to zeppehns. 

Many materials have been used as the stationary phase in column chromatography. Finely ground alumina (aluminum oxide, AI2O3) and silicic acid (silica gel, Si02) are by far the most common adsorbents (stationary phases). Many common organic solvents are used as the liquids (sometimes called eluents) that act as the mobile phase and elute (wash) materials through the column. Table 5.8 lists the better known column packing and elution solvents. 

As shown in Scheme 6.13, if the catalyst for the reduction is changed from Pt to Pd, the stereochemistry of the reduction is apparently altered. However, once it is recognized that Pd on alumina (aluminum oxide [AI2O3]) causes isomerization—a rearrangement vide infra) from one alkene to another—faster than reduction occurs, the result is explicable. Thus, (Scheme 6.13) 1,2-dimethylcyclohexene... 

Interestingly, as shown in Scheme 8.103, if furfural (furan 2-carboxalehyde) is reduced with hydrogen (H2) in the presence of a Ni catalyst, the corresponding primary alcohol, tetrahydrofurfuryl alcohol, results. Then, if the that primary alcohol is heated to 350°C in the presence of an alumina (aluminum oxide, AI2O3) catalyst, rearrangement and dehydration occur to yield dihydropyran (oxahex-2-ene). 

ALUMINA (ALUMINUM OXIDE). A naturally basic polar adsorbent with a variety of pore sizes that is used for chromatography after thermal dehydration at a specified temperature to control its activity grade. 

A rarely used polar stationary phase is alumina (aluminum oxide alox). It has a different selectivity to silica, and its packings show higher theoretical plate heights (i.e., the number of theoretical plates per unit length is lower). In contrast to silica, irreversible adsorption of analytes can be a problem. 

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