Stretching, filter media

In the true gravity case, pumps are not used. If, however, the liquid is highly viscous, to achieve efficient operation, pumps are required to force the fluid through the pressure filters. The pump can be considered essentially as a press with a plate-and-frame filter. The plate-and-frame filter consists of a series ot frames over which the filter medium is stretched. A centrifugal basket of fine mesh is another method of particulate removal. 

Cotton filter cloths Woven cotton cloth stretched on a frame to produce a filter medium. 

A solution of Pd(PPhj)4 (767 mg, 0.665 mmol), Af-phenyldiphenylketenimine (2.93 g, 10.9 mmol) and (l-methylethylidene)cyclopropane (2.03 g, 35.6 mmol) in anhyd toluene (30 mL) was placed in a 200-mL stainless steel autoclave. The autoclave was pressurized with 4 MPa of Nj at rt and then heated to 123 °C for 30 h with stirring. After the reaction was complete (most easily monitored by the disappearance of the ketenimine stretching vibration in the IR spectrum), the mixture was filtered through a pad of alumina (EtjO) in order to remove the solid elemental palladium. After removal of the readily volatile components (bp up to 30 C/10" Torr), the brown, vi.scous residue was purified by medium-pressure chromatography (silica gel, CHjClj/cyclohexane 1 1). Under these conditions, most of the impurities were washed off, while the cycloadduct remained on top of the column and was finally eluted with pure Et20 yield 3.3 g (93%) brown needles 98% pure (as determined by GC) mp 148°C (toluene). 

In the membrane filter process, larger quantities of water can be pressed or sucked through a sterile membrane filter inserted in the sterile filtering device. The filter is then stretched free of bubbles on the surface of the soldified nutrient medium in a Petri culture dish and the culture thus... 

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