Gas flushing

Polyester. Poly(ethylene terephthalate) [25038-59-9] (PET) polyester film has intermediate gas- and water- vapor barrier properties, very high tensile and impact strengths, and high temperature resistance (see Polyesters, thermoplastic). AppHcations include use as an outer web in laminations to protect aluminum foil. It is coated with PVDC to function as the flat or sealing web for vacuum/gas flush packaged processed meat, cheese, or fresh pasta. 

Polyacrylonitrile (PAN) films have outstanding oxygen and CO2 barrier properties, but only modest water-vapor barrier properties. They are for processed-meat and fresh pasta packaging laminations where an oxygen barrier is required for vacuum or gas flush packaging. 

Inert gas flush packing in plastic-laminated pouches, although less effective than vacuum packing, can remove or displace 80—90% of the oxygen in the package. These packages offer satisfactory shelf life and are sold primarily to institutions. 

Warning Package integrity may be compromised when using coated elastomers, especially for vacuum-sealed or gas-flushed vials [11]. 

The finished product is then packed. If the product is going to a restaurant it will probably be packed in boxes. Product for supermarkets is then flow packed with or without a carbon dioxide gas flush. Those types of Naan most susceptible to oxidation receive the gas flush. Suitably packed Naan will keep for three or four months. 

Add 10.0 g of cold item 13 (cooled and nitrogen gas flushed) in a separate container with lid. Pass nitrogen gas at 20 to 40 psi pressure for 15 minutes. 

Fig. 1.26. Sublimation apparatus. Solids are introduced under inert-gas flush, and a loose plug of glass wool is introduced. The oil bath should extend above the glass wool. High vacuum may be applied through the standard taper joint. A lower vacuum may be applied through the sidearm.

Fig. 1.5. Joining two pieces of equipment under inert-gas flush. Both pieces are initially purged with inert gas separately before joining. Note the use of wire hooks and rubber bands to secure individual pieces of glassware. If the glassware is constructed using O-ring joints, the O-ring joint clamps hold the apparatus together.

Finally, it is often possible to generate quantitatively the desired gas from measured amounts of liquid or solid reagents. The generated gas is then quantitatively transferred by inert-gas flush into a reaction mixture. The automatic gasimeter developed by C. S. Brown and H. C. Brown is useful when it is necessary to know the quantity of gas consumed in the course of a reaction.8 This apparatus can be applied to the generation of a variety of gases, such as H2,8... 

Sublimation is readily performed in Schlenk apparatus of the type illustrated in Fig. 1.26. The sublimate, which collects on the upper walls, may be collected by positioning the apparatus horizontally and scraping the product into a receiver attached to the side joint while an inert-gas flush is maintained on the equipment. 

VOCs are purged from soil and water samples with a flow of an inert gas and concentrated in a trap kept at ambient temperature. After the purging has been completed, the trap is heated, and a reverse flow of inert gas flushes the VOCs from the trap onto the top of the column. 

These semi-preparative methods are useful where identification is required but for quantitative and comparative analytical purposes much more rapid sampling techniques, such as automated headspace and solid phase microextraction (SPME), may be preferred. Both of these techniques give similar results for most volatiles. In the former, the vapour above a heated sample is removed by a syringe or gas flushing and injected onto a GC column, either directly or after trapping on a suitable absorbent and thermal desorption. In SPME, the vapour is absorbed on to a suitable bonded medium on a special needle and then injected into the gas chromatogram. 

Trichlorosilane formation is finally caused by the reaction of HCl and a silylene species. A completely formed catalyst which was cooled to room temperature under reaction gas, flushed with H2 and treated again with a H2/SiCl4 mixture at the previous reaction temperature, is inactive. The reaction can be restarted on the silylene species-covered surface by a HCl pulse. The conversion reaches the original level. 

It consists of a ceramic cubic body, in which a cylindrical cavity is drilled. A channel is drilled perpendicular to the axis of the cavity and hosts two rods (electrodes) of the material to be vaporized, facing each other and separated by a gap of about 1 mm. A solenoid pulsed valve injects helium at the pressure of 20 bar through an insulating ceramic nozzle on the back of the cavity. The gap between the electrodes is off-axis, in such a way that the gas flushes on the cathode surface. A removable nozzle with cylindrical shape closes the front of the source. 

If chlorine does not evolve in the gas phase in normal process conditions, an inert gas flush in the reactor gas phase is recommended (see below). If a chlorine flow evolves from the liquid reaction mixture unreacted, enough inert gas flush must be provided in the reactor gas phase to lower the chlorine concentration below the minimum oxidizer concentration (MOC) of the fuel flammable range. 

Ever since the time of Aston, contamination problems have plagued the mass spectroscopists. Ions of hydrocarbon fragments which fall at almost every mass present a serious problem. These contamination problems are even greater when instruments of high sensitivity are used in low-level detection work. Small residual ion currents due to hydrocarbons persist even after long baking and inert gas flushing of the mass spectrom-... 

The purge vessel is made of Duran (Pyrex) glass [20 mm outer diameter (o.d.), 20 cm length] and accommodates a glass frit at the bottom (Schott, pore size Gl) the top S cm are widened to 40 mm o.d. to prevent bubbles entering the helium outlet. The above dimensions (ca. 50 mL internal volume) are chosen to minimize purge gas flushing time and are suitable... 

Avoid contact of the skin with liquid air or its cold boil-off gas. Flush liquid air spills with water to accelerate evaporation. Because of the preferential evaporation of nitrogen, initially... 

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