Filling phase, pressure filters

For milk, transfer the entire sample extract into a separatory funnel (250-mL), add an equivalent volume of dichloromethane plus a half equivalent volume of sodium chloride solution (5%, w/v). Shake the separatory funnel for 2 min and allow the phases to separate. Partially fill a glass filter funnel with anhydrous sodium sulfate (approximately 10 g) and filter the lower dichloromethane layer through the sodium sulfate, collecting the filtrate in a round-bottom flask (250-mL). Wash the sodium sulfate with dichloromethane (5 mL) and collect the washings in the same round-bottom flask. Rotary evaporate the sample to dryness under reduced pressure with a water-bath temperature of 40 °C. Dissolve the residue in 4 mL of ethyl acetate-toluene (3 1, v/v) and transfer the solution to a suitable vial ready for GPC cleanup. 

Filling Phase. Here the sludge is punqjed at low pressure into the filter chambers. The filling time is related to the total volume of the press and the pun ) capacity. 

Fig. 9. Apparatus for sluijy packing of columns. After the properly fittul column tube is attached to the bottom of the reservoir, both are filled up with the slurry ofthe micropartic-ulate stationary phase. Thereafter a displacement liquid is pumped into the reservoir by the constant pressure pump, e.g., Haskel Model DST>I00, which is driven by preuurized air. Upon displacement, the slurry from the reservoir is filtered over the porous etal frit at the bottom of the column tubing which becomes densely packed with the partic s. By intermit-tently operating the liquid shut-off valve between the pump and the reservoirpressure waves can te generated in order to flirther compact the column packing. Reprinted from Bakalyar et at. U05) with permission from Spectra-Physics.

Sulphonic acids and their salts are analysed by GC after esterification with diazomethane or after chlorination with thionyl chloride or phosgene [119]. Reaction with thionyl chloride proceeds according to Scheme 5.14. A 0.5-g sample of sulphonic acid or its salt is placed into a round-bottomed flask fitted with a magnetic stirrer and a reflux condenser, 0.5 ml of dimethylformamide and 20 ml of thionyl chloride are added and the mixture is refluxed for several minutes up to 2 h (according to the character of the sample) until the evolution of gas from the reaction mixture ceases (detection with the aid of a bubbler filled with chlorobenzene). If a salt is chlorinated, solid chloride produced in the reaction mixture must be removed by dilution with dichloromethane and by careful filtration through a fine glass filter. Excess of thionyl chloride and solvent is evaporated carefully under decreased pressure. The residue is dissolved in a suitable solvent (CCU) and analysed by GC (silicone stationary phase, temperature 160°C). 

At 60 °C, N-chlorosuccinimide (28 mmol) dissolved in 30 ml acetonitrile was added to the product from Step 1 (28 mmol) dissolved in 50 ml acetonitrile and the mixture stirred 20 minutes, cooled, and concentrated. The residue was suspended in 50 ml of toluene for about 90 minutes, filtered, filled into a mini autoclave, and an ethylene pressure of 30 bar applied. Over a period of 5 hours, a solution of NaHCOj (4.7 g) dissolved in 50 ml water was metered in and the mixture stirred at 30 bar ethylene pressure 5 hours. Thereafter, the phases were separated, the toluene phase washed twice with NaHCOj, once with water, dried, concentrated, and the product isolated in 86% yield, mp = 100-105 °C. H-NMR data supplied. 

Incomplete filling in any phase of the filter operation Filter going on-stream before precoat clears up Poor clarity when on-stream Low or high pressures Too thick filter cakes Power failures... 

Sedimenting and Filtering Centrifuges Under centrifugal force, the solid phase assumed to be denser than the liquid phase settles out to the bowl wall—sedimentation. Concurrently, the lighter, more buoyant liquid phase is displaced toward the smaller diameter—flotation. This is illustrated in Fig. 18-149a. Some centrifuges run with an air core, i.e., with free surface, whereas others run with slurry filled to the center hub or even to the axis in which pressure can be sustained. 

When a test gas (for example ambient air) is applied over a water moistened filter, just below the pressure level of the bubble point, test gas diffusion will occur through the water in the wetted membrane filter. This diffusion happens in all water filled pores, not only in the largest. This principle is the basis for two tests, which use different approaches to measure gas diffusion the pressure hold test and the diffusive-flow (forward flow) test. Other names for the same principle tests exist. These tests are performed at a pressure of about 80 % of the theoretical bubble point pressure of the filter. It is important that the largest pores are still filled with liquid. In this phase, diffusion occurs more or less linearly with the pressure drop over the... 

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