Rotary washing efficiency

Application of the models to washing on fiiU-scale eqiiipment raises the question of washing efficiency. One approach involves the use of a strai tforward efficiency fector which is related principally to the type of filter to be used and to the appUcation, as mentioned above. Purchas and Wakeman [1986] noted the relationship between the washing efficiency and the type of system found by Choudhury and Dahlstrom for rotary drum vacuum filters and proposed a correction of the diversion parameter rather than the use of an efficiency ctor. This correction may be expressed as ... 

A 100-mL volume of benzene is added to the 20 g of air-dried soil and the mixture is shaken vigorously for 2h. After extraction twice with 100 mL of benzene, the combined extract is filtered through filter paper and the filter cake is washed with an additional 20 mL of benzene. The benzene extracts are dried over anhydrous Na2S04 and concentrated to dryness using a vacuum rotary evaporator. The residue is dissolved in an appropriate volume followed by GC/ECD analysis. For the monitoring of pesticide residues in soil, methanol for bifenox and oxyfluorfen and acetonitrile for nitrofen were recommended as the solvents for efficient extraction. ... 

The aqueous hydrazide solution is evaporated from a tared 2000 ml flask on an efficient rotary evaporator, using a bath temperature of 40° and an ice-cooled condenser the 3000 ml siphon flask assembly is used as storage for the vacuum feed. The weight of the crude hydrazide so obtained is determined, it is dissolved in about 170 ml 1 N tartaric acid, the aqueous solution washed with three 30 ml portions ether, made alkaline with 190 ml 1 N ammonium hydroxide, and exhaustively extracted with successive portions of chloroform, the first two portions being 100 ml each, the following 50 ml. 

Dissolve 5.3 g (0.05 mol) of benzaldehyde (previously shaken with sodium hydrogen carbonate solution) and 0.25 g (0.67 mmol) of tetrabutylammonium iodide in 50 ml of dichloromethane. Place this solution in a 250-ml, three-necked round-bottomed flask equipped with an efficient sealed stirrer unit, a reflux condenser and a thermometer sited in a screw-capped adapter, and supported in an oil bath mounted on an electric hot plate. Introduce 50 ml of a 50 per cent (w/v) aqueous solution of sodium hydroxide, and then 10.2 g (0.05 mol) of finely powdered trimethylsulphonium iodide. Adjust the electric hot plate so that the oil bath is maintained at a constant temperature of 55 °C for 60 hours and during this period stir the reaction mixture rapidly (1). Pour the reaction mixture on to ice, separate the organic phase and extract the aqueous solution with one 20 ml portion of dichloromethane. Wash the combined organic phases successively with four 20 ml portions of water, two 10 ml portions of a saturated solution of sodium metabisulphite and finally two 20 ml portions of water. Dry the organic phase over anhydrous calcium sulphate, remove the dichloromethane on a rotary evaporator and distil the residue. Collect the phenyloxirane as a fraction having b.p. 191— 192 °C the yield is 4.7 g (78%). 

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