Aluminum column

Cover plate material Aluminum Column diameter 50 pm... 

Increased Surface Area of Walls. If glass columns are used the surface area may be increased by treatment with hot ammonium or sodium hydroxides. If aluminum columns are used a similar treatment can be employed. In the former case a layer of porous silica is formed, in the latter a layer of porous alumina. 

Chromatographic System (See Chromatography, Appendix IIA.) Use a gas chromatograph equipped with a thermal-conductivity detector and containing a 6-m x 3-mm aluminum column, or equivalent, packed with 10 weight percent tetra-ethylene glycol dimethyl ether liquid phase on a support of crushed firebrick (GasChrom R, or equivalent), which has been calcined or burned with a clay binder above 900° and silanized, or equivalent. Use helium as the carrier gas at a flow rate of 50 mL/min, and maintain the temperature of the column at 33°. 

Radionuclidic Purity Radionuclidic purity is defined as the fraction of the total radioactivity in the form of the desired radionuclide present in a radiopharmaceutical. Radionuclide impurities may arise from impurities in the target material or from fission of heavy elements in the reactor [2], In radionuclide generator systems, the appearance of the parent nuclide in the daughter nuclide product is a radionuclidic impurity. In a "Mo/"mTc generator, "Mo may be found in the "mTc eluate due to breakthrough of "Mo on the aluminum column. The presence of these extraneous radionuclides increases the radiation dose to the patient and may also obscure the scintigraphic image. 

Figure 14. Effect of office size (a) in a multilayer filter with 0.6 x 0.6 mm cell on the height of liquid aluminum column required for melt transition through a filter. (1) Without cavitation action (2) Under cavitation action.

Fia. 37. Gas chromatogram of a synthetic mixture of Ca to Cu fatty acids as the free acids. Aluminum column, 2 metersX% inch 0.25% Carbowax and 0.4% isophthalic acid on 200-/t glass microbeads (acid-washed). Temperature-programmed from 90° to 175° at 3.3° per minute. Sample 02 /il flow rate, 80 ml of helium per minute. Identification of peaks 1, acetic S, propionic S, isobutyric 4> butyric 5, isopentanoic 6, pentanoic 7, hexanoic 8, 2-ethylhexanoic 9, octanoic 10, non-anoic 11, decanoic 12, undecanoic 13, undecenoic. Reproduced from Nikelly (N4) with permission. 

Analyzed on a 6-foot X 1/4-inch aluminum column packed with 20% UCON WS on 60/80 Chromosorb W. 

The solubility properties of coenzyme Q constitute the basis for its purification. The coenzyme can be extracted with heptane or isooctane, then treated with an alkaline solution containing pure alcohol, and after chromatographic analysis on aluminum columns, it can be crystallized from ethanol or methanol. Samples obtained by such procedures all have the same characteristics on silicon-treated paper and present identical visible and infrared spectra as well as identical coenzyme activities. 

Figure 1.1 Various columns and materials used for packed column gas chromatography (a) 6 ft X 0.25 in. o.d. copper tubing b) from left to right 4 ft x 0.25 in. o.d. aluminum column, 20 ft X I in. o.d. aluminum column for preparative GC, 10 ft x 1/8 in. o.d. stainless steel column, 3 ft x in. o.d. stainless steel column coiled in a pigtail configuration (c) glass packed gas chromatographic columns, 2 m x 0.25 in. o.d. x 4 mm i.d. Note the differences in the length configuration of the ends, specific to two different chromatographs.

Glc separation of the volatile compounds was achieved using a 12-ft X 1/4-in Teflon-lined aluminum column packed with 20% Apiezon-L on Chromosorb-W 60/80 with manual temperature programming from 150 to 230 . Two compounds were isolated. The most volatile compound gave an nmr spectrum (6 1.65, s, 6H 6 2.25, t, 2H 6 3.4, t, 2H in CDCl.) identical to the spectrum of an authentic sample of 2,2-dimethylthietane (14). A mass spectrum of 14 gave fragmentation ions at m/e values of 102, 87, 74, 69, 68, 59, 56 (base peak), and 41 which are consistent with its structure. 

Fig. 1.8. GC-AED of redistribution of ligands on gallium and aluminum. Column 5 m X 0.2 mm i.d. FSOT SE 30 capillary at 108°C. (a) Carbon detection at 247.9 nm, (b) gallium detection at 294.3 nm, (c) aluminum detection at 396.1 nm. (Reproduced by permission from J. Analytical Atomic Spec., 1988, 3, 919 copyright 1988, Royal Society of Chemistry.)...

Packed Columns A packed column is constructed from glass, stainless steel, copper or aluminum and is typically 2-6 m in length, with an internal diameter of 2-4 mm. The column is filled with a particulate solid support, with particle diameters ranging from 37-44 pm to 250-354 pm. 

In France, Compagnie Europnene du Zirconium (CEZUS) now owned jointly by Pechiney, Eramatome, and Cogema, uses a separation (14) based on the extractive distillation of zirconium—hafnium tetrachlorides in a molten potassium chloride—aluminum trichloride solvent at atmospheric pressure at 350°C. Eor feed, the impure zirconium—hafnium tetrachlorides from the zircon chlorination are first purified by sublimation. The purified tetrachlorides are again sublimed to vapor feed the distillation column containing the solvent salt. Hafnium tetrachloride is recovered in an enriched overhead fraction which is accumulated and reprocessed to pure hafnium tetrachloride. 

The reaction of chlorine gas with a mixture of ore and carbon at 500—1000°C yields volatile chlorides of niobium and other metals. These can be separated by fractional condensation (21—23). This method, used on columbites, is less suited to the chlorination of pyrochlore because of the formation of nonvolatile alkaU and alkaline-earth chlorides which remain in the reaction 2one as a residue. The chlorination of ferroniobium, however, is used commercially. The product mixture of niobium pentachloride, iron chlorides, and chlorides of other impurities is passed through a heated column of sodium chloride pellets at 400°C to remove iron and aluminum by formation of a low melting eutectic compound which drains from the bottom of the column. The niobium pentachloride passes through the column and is selectively condensed the more volatile chlorides pass through the condenser in the off-gas. The niobium pentachloride then can be processed further. 

Aluminum geodesic dome roof tanks are becoming popular. These are often the economic choice. They offer superior corrosion resistance for a wide range of conditions, and are clear span stmctures not requiring internal supports. They can also be built to any required diameter. However, domes caimot handle more than a few inches of water column internal or external pressure. 

Reagent grade dichloromethane is dried by passing over a column of aluminum oxide (activity I). 

Aluminum triethyl (triethyl aluminum) [97-93-8] M 114.2, b 69°/1.5mm, 76°/2.5mm, 129-131°/55mm, d 0.695, n 1.394. Purified by fractionation in an inert atmosphere under vacuum in a 50cm column containing a heated nichrome spiral, taking the fraction 112-114°/27mm. It is very sensitive to H2O and should be stored under N2. It should not contain chloride which can be shown by hydrolysis and testing with AgN03. [J Am Chem Soc 75 4828 51937953 NMR J Am Chem Soc 81 3826 7959.]... 

Cyclohexene can be prepared on a large scale still more rapidly and efficiently by the distillation of cyclohexanol over silica geP or, better, activated alumina. Using a 25-mm. tube packed with 8- to 14-mesh activated alumina (Aluminum Company of America) and heated to 380-450 over a 30-cm. length, 1683 g. of cyclohexanol was dehydrated in about four hours. After separating the water, drying with sodium sulfate, and fractionating with a simple column, 1222 g. (89 per cent yield) of cyclohexene, b.p. 82-84 , was obtained. 

The checkers used a 30-mm. (I.D.) chromatographic column charged with approximately 250 g. of activated (400° for 12 hours), acid-washed, chromatographic aluminum oxide (Merck and Co., Inc.). 

Preparation of cholesta-5,7-diene-ia,3/3-diol a solution of 500 mg of the 1,4-cyclized adduct of cholesta-5,7-dien-3/3-ol-ia,2a-epoxideand 4-phenyl-1,2,4-triazoline-3,5-dione in 40 ml of tetrahydrofuran is added dropwise under agitation to a solution of 600 mg of lithium aluminum hydride in 30 ml of THF. Then, the reaction mixture liquid Is gently refluxed and boiled for 1 hour and cooled, and a saturated aqueous solution of sodium sulfate is added to the reaction mixture to decompose excessive lithium aluminum hydride. The organic solvent layer is separated and dried, and the solvent Is distilled. The residue Is purified by chromatography using a column packed with silica gel. Fractions eluted with ether-hexane (7 3 v/v) are collected, and recrystallization from the methanol gives 400 mg of cholesta-5,7-diene-la, 3/3-diol. 

A mixture of 50 g of betamethasone, 50 cc of dimethylformamide, 50 cc of methyl orthobenzoate and 1.5 g of p-toluenesulfonicacid Is heated for 24 hours on oil bath at 105°C while a slow stream of nitrogen is passed through the mixture and the methanol produced as a byproduct of the reaction is distilled off. After addition of 2 cc of pyridine to neutralize the acid catalyst the solvent and the excess of methyl orthobenzoate are almost completely eliminated under vacuum at moderate temperature. The residue Is chromatographed on a column of 1,500 g of neutral aluminum oxide. By elution with ether-petroleum ether 30 g of a crystalline mixture are obtained consisting of the epimeric mixture of 170 ,21 -methyl orthobenzoates. This mixture is dissolved without further purification, in 600 cc of methanol and 240 cc of methanol and 240 cc of aqueous 2 N oxalic acid are added to the solution. The reaction mixture is heated at 40°-50°C on water bath, then concentrated under vacuum. The residue, crystallized from acetone-ether, gives betamethasone 17-benzoate, MP 225°-231°C. 

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