Wet packing

FIG. 26-27 Some special arrester designs (a) liquid seal arrester (h) Linde hydraulic seal arrester (c) wetted packed-bed acetylene decomposition arrester. (Howai d, 19S2.)... 

During prolonged outages, remove wet packing and clean gasketed surfaces thoroughly. 

Solution Only the bottom one-foot was hand stacked and the rest of the bed was randomly packed using a wet-packing technique. 

Poor distribution reduces the effective wetted packing area and promotes liquid channeling. 

Wetted packing area may differ considerably from the physical area of a packing. This is of particular importance in comparing the effectiveness of different packings. 

The submitters mixed active anhydrous silica gel with water (12% v>/w) and stored it in a sealed container for at least 24 hours prior to use. A ratio of 60-80 g. of silica gel per gram of crude product was used for column chromatographic separations, and a column was chosen that would give a 10 1 height diameter ratio of adsorbent. Columns were wet-packed with distilled petroleum ether (b.p. 60-68c), and after the crude product had been applied a step-gradient was run rapidly through 2% vjv ether in petroleum ether, 5% ether, and 10% ether. The column was then eluted with 20% vjv ether in petroleum ether until the bromohydrin acetate was obtained. 

The checkers obtained roughly 30 g. of crude product in each run. Freshly opened Woelm silica gel (obtained from ICN Pharmaceuticals, 26201 Miles Ave., Cleveland, Ohio 44128) was deactivated as above, and 1800 g. was wet-packed with petroleum ether in a 65-mm. internal diameter column. In the first run the column was eluted as above, but a considerable amount of solvent was required to collect the product. Therefore, in the second run the crude product was applied to the column as a solution in petroleum ether, and 1-1. portions of 20% v/v ether petroleum ether, 30% ether, 40% ether, 50% ether, 60% ether, and 70% ether were run through. None of these six fractions contained a significant weight of material. Elution with 2 1. of 80% v/v ether petroleum ether then provided the bromohydrin acetate. 

It is important to wet-pack the column with the eluting solvent. Dry packing results in strong retention of the sample and poor separation, possibly because the small amount of ether in the eluting... 

Add lOg of wet packed cells to the lysis buffer and stir vigorously for 30 minutes. 

Assuming the reaction to occur within the wet packing volume Vs, the liquid phase balance for MEK is... 

Figure 4.16. Pressure drops in wet packings (logarithmic axes)...

This procedure utilises a glass column (130mmx5mn) wet packed with approximately 2gm of Silica Gel (Merck 7754 BDH Chemicals) prepared by heating to 500°C 20°C for two hours, cooled and deactivated to 1.0% w/w water. Solvents are n-pentane (glass distilled, Rathbum Chemicals Ltd) and diethyl ether (Distol, Fisons). 

The importance of the wetting efficiency results mainly from the fact that it is closely related to the reaction yield, and more specifically to the catalyst effectiveness factor (Burghardt et al., 1995). The reaction rate over incompletely covered catalytic particles can be smaller or greater than the rate observed on completely wetted packing, depending on whether the limiting reactant is present only in the liquid-phase or in both gas and liquid-phases. 

RNA does not normally precipitate like DNA, but it could still be a minor contaminant. RNA may be degraded during the procedure by treatment with ribonuclease after the first or second deproteinization step. Removal of RNA sometimes makes it possible to denature more protein using chloroform-isoamyl alcohol. If DNA in a highly purified state is required, several deproteinization and alcohol precipitation steps may be carried out. It is estimated that up to 50% of the cellular DNA is isolated by this procedure. The average yield is 1 to 2 mg per gram of wet packed cells. 

Bacterial cells, wet packed, 2 to 3 g. Use B. subtilis, Escherichia coli, or Clostridium wekhii. If lyophilized cells are available, use 0.5 g. Saline-EDTA, 0.15 M NaCl plus 0.1 M ethylenediaminetetraacetate, pH 8... 

Suspend 2 to 3 g of wet packed bacterial cells or 0.5 g of lyophilized cells in 25 mL of saline-EDTA solution in a 125-mL Erlenmeyer flask. Add 1.0 mL of the lysozyme solution (10 mg of lysozyme) and incubate the mixture at 37°C for 30 to 45 minutes. To bring about complete cell lysis, add 2.0 mL of 25% SDS solution and heat the mixture in a 60°C water bath for 10 minutes. To avoid excessive foaming, stir the mixture very gently. As the nucleic acid is released from the lysed cells, the solution will show an increase in viscosity and a decrease in cloudiness. 

To speed up formation of columns, both in dry and wet packing a slight suction is usually applied, carefully avoiding formation of cracks. 

Wet packing is quicker and gives more homogeneous adsorbents. Various types of columns are described in Ref 58. pp 14-18 and in Ref 78,pp 56-8... 

The acid-free sample was quantitatively transferred to the cation-exchange resin (oa. 150 ml) wet-packed as described above. Unreactive materials were eluted under an argon atmosphere with pentane for oa, 48 hours at a rate of 6 to 10 drops per minute. The reactive materials were recovered by eluting the resin with benzene and then with an 8% 2-propylamine in methanol solution (V/V). The two eluents were combined to yield the total base fraction. 

A chromatographic column was wet-packed to half capacity with a pentane slurry of Amberlyst A-29 (oa. 100-125 ml) and a glass-wool plug positioned on top of the resin bed. The remaining volume of the column was wet-packed with a pentane slurry of ferric chloride coated on Attapulgas Clay (120-125 ml). The acid-and base-free material was quantitatively transferred to... 

Continuous-phase wetted packing Preferential continuous-phase type... 

Dry-packed beds have higher pressure drops than wet-packed beds. Billet (56) and Kister (40) report cases where changing from dry to wet packing increased column capacity by 5 percent and reduced pressure drop by 10 percent. Ludwig (63) reports cases where this pressure drop reduction was 50 to 60 percent. The... 

Complete wetting of the packing by preflooding the column at the start of the operation or use of a self-wetting packing, such as protruded packing, can decrease the detrimental effects of poor liquid distribution. 

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