Pressure removable

Tri-p-tolyl phosphate [20756-92-7, 1330-78-5 (isomeric tritolyl phosphate mixture)] M 368.4, b 232-234 , d 1.16484, n 1.56703. Dried with CaCl2, then distd under vacuum and percolated through a column of alumina. Passage through a packed column at 150°, with a counter-current stream of nitrogen, under reduced pressure, removed residual traces of volatile impurities. 

The slam-shut valve cuts off the gas supply in the event of predetermined pressure criteria being exceeded. It must be manually reset, having made safe the downstream pipework and the cause of the abnormal pressure removed. 

Polymerization was carried out in NaOH aqueous solution. Table 4 summarizes the reaction conditions and polymer yields. The first step of the polymerization was hydrolysis and oligomerization of the silylethers at low temperatures from 90°C to 150 °C. In order to increase the polymer yield and the softening point of the polymers, the second step was carried out at higher temperatures under reduced pressure, removing alcohol and water, 1H-NMR, 13CNMR and IR spectroscopy of each polymer show that these polymers have the polysiloxane structure substituted with a phenol group. 

As soon as micro-bubbles only are being produced in the nitrometer close the stop-cock on the connecting tube, detach the rubber connecting tube from the combustion tube, close the latter with a cap made from rubber tubing, and leave to cool whilst maintaining the internal carbon dioxide pressure. Remove the nitrometer to a somewhat cooler room (room in which the barometer is kept preferably) after raising the bulb so that the surfaces of the two columns of liquid are at the same level. 

As illustrated for compounds 85 and 86 in Scheme 20, different methods were used for the syntheses of 85-87 (87 was prepared analogously to 86). Compound 85 was synthesized at 40°C in acetonitrile under reduced pressure (removal of part of the solvent along with the dimethylamine formed), whereas 86 and 87 were prepared in acetonitrile at room temperature. All products were isolated in good yields as crystalline solids. 

After the preform had been felted from a water slurry, it was compacted at atmospheric pressure, removed from the die dried at 140°F in a steam-heated, circulating air oven. The dried preform was then soaked in the impregnating resin soln, drained, and finally flash-dried in a vacuum oven to a point where it could be post formed... 

Extract the aqueous phase with six 250-m portions of methylene chloride wash the solid cake with three of the portions prior to their use on the solution. Dry the combined extracts over 40 g of anhydrous magnesium sulfate and inhibit with 0.5 g of hydroquinone. Remove the drying agent by filtration and strip the methylene chloride by distillation at atmospheric pressure remove final traces of this solvent by stripping at 20 mm pressure and room temperature. Then separate the mixture of crude vinyl isomers by distillation at reduced pressure. By heating to a pot temperature of 90°C, the 2-methyl-5-vinyltetrazole is conveniently and almost completely removed at 1.0 mm pressure. A well cooled condenser and a receiver chilled in an ice-water bath are needed to prevent loss of the condensate. The weight of once distilled 2-isomer is 89.9 g the index of refraction at 25°C is 1.4814, corresponding to a purity of 97.2 percent. The corrected yield amounts to... 

Determine what the viscous dissipation effects are in a melting with pressure removal problem. Use the notation of Fig. 6.65. 

With many systems, especially those containing microporcs, low pressure hysteresis (indicated by the dashed lines in Figure 3), may be observed extending to the lowest attainable pressures. Removal of the residual adsorbed material is then possible only if the adsorbent is outgassed at higher temperatures. This... 

Procedure Immerse the sample bottle in a water bath, maintained between 96° and 100°, to the same depth as that of the mixture in the bottle. Heat in the water bath for 30 to 60 min, using 60 min for Polyethylene Glycols having molecular weights of 3000 or higher, then remove the bottle from the bath and allow it to cool to room temperature. Uncap the bottle carefully to release any pressure, remove the bottle from the fabric bag, add 5 drops of a 1 100 phenolphthaleimpyridine solution, and titrate with 0.5 N sodium hydroxide to the first pink color that persists for 15 s, recording the volume, in milliliters, of 0.5 N sodium hydroxide required as S. Perform... 

With glacial acetic acid, temperatures up to its boiling point, 118°C, may be used. This higher washing temperature—without pressure— removes impurities in less time than methanol, and at temperatures between 105° and 110°C, the raw sugar is refined in 45-90 min. 

With all other quantities held constant increasing the number of gas particles increases the pressure. These added particles are at the same temperature as the other particles so they donT hit the container any harder. Because there are more particles though they hit the walls of the container more often. More collisions with the container mean a higher pressure. Removing gas particles decreases the pressure because there are fewer collisions with the walls of the container. 

Figure 14.4 Schematic representation of an apparatus for FVP As with all high vacuum work, care must be taken. After all of the substrate has passed through the hot tube, turn off the furnace and allow to cool to room temperature (still under vacuum). Then turn off the pump and admit nitrogen to atmospheric pressure. Remove the traps to a fume cupboard and allow to warm to room temperature, and work up in the usual way. If the desired product is unstable towards air, water, or is simply very reactive, then a more sophisticated pyrolysis system might be required, and more elaborate work up procedures used.

Citric acid (Kahlbaum), CsHsOy H2O. Molecular weight 210.0. Commercial samples may be recrystallized twice from water and then dried to constant weight over deliquescent sodium bromide. The acid contains one molecule of water of crystallization. Sorensen specifies that solutions of the acid should be clear and give no reaction with barium and silver nitrates. The ash content of 5 g, should be less than 1 mg. Drying at 70° and 20-30 mm. pressure removes the water of crystallization, which corresponds to an 8.58% db 0.1% loss in weight. 

In a well-ventilated hood a 1-1. three-necked flask is immersed in an oil bath and fitted with a mechanical stirrer and condenser with aT-piece at the top with one lead connected to a nitrogen supply and the other to a gas bubbler. The flask is charged with 60 g. (0.49 mole) of c/i-3,4-dichlorocyclobutene (this volume) in 250 ml. of benzene, and the system is flushed with nitrogen. A first 50-g. batch of diiron nonacarbonyl (2) is added and the mixture is heated at 50-55° with stirring. After about 15 min. the initial rapid evolution of carbon monoxide becomes greatly diminished and a further 25 g. of Fe2(CO)9 is added. Further 25-g. portions are added until no more carbon monoxide is liberated a total of approximately 275 g. of Fe2(CO)9 is required and the total reaction time is about 5 hrs. The mixture is then filtered with suction through Celite and the Buchner funnel is washed thoroughly with pentane until the filtrate is colorless. Fractional distillation at reduced pressure removes benzene, then iron pentacarbonyl (b.p. 20730 mm.) when the Fe(CO)5 has been removed, cyclobutadieneiron tricarbonyl is collected as a pale yellow oil, b.p. 4773 mm. 

Some time later Before you shut off the pump, take one last pressure reading. Shut off the vacuum pump and slowly open the bleeding valve. As the system comes to atmospheric pressure, remove the vacuum tubing from one side of the trap to prevent pump oil from siphoning into the trap. 

Release the pressure, remove and clean the sample prior to testing. 

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