Sticking vacuum

Synthesis of Poly(phenylene sulfide)-4/ocit-Poly(TFE-co-PVE)- /ocit-poly(phenylene sulfide). The block copolymer can be demethylated by refluxing pyridine. AIL three-necked round bottom flask equipped with a mechanical stirring stick (vacuum sealing type), thermometer and reflux condenser was charged with obtained polymer (101.4 g) and acetonitrile (600 mL). The solution was stirred at room temperature for 2 hand pyridine (80 g, 1.01 mmol) was added to demethylate the polysulfonium. The reaction mixture was stirred at room temperature for 10 h. The pale yellow suspension changed to a white suspension. The reaction temperature was increased and the mixture was refluxed for 20 h and then precipitated in methanol (10 % HCl, 2 L), washed with water and methanol. The obtained polymer was refluxed in ethanol (1 L) for 5 h to wash the polymer and freon 113 (IL) to remove the Poly(TFE-co-PPVE) homopolymer for 15 h and dried in vacuo for 15 h at 60 <>C (66.8 g, yield 96.5 %). IR (KBr, cm-i) 3065, 1572, 1472, 1387, 1234, 1091, 1074, 1009, 812, 554, 481 CP/MAS 13C-NMR(... 

Most fiindamental surface science investigations employ single-crystal samples cut along a low-index plane. The single-crystal surface is prepared to be nearly atomically flat. The surface may also be modified in vacuum. For example, it may be exposed to a gas that adsorbs (sticks) to the surface, or a film can be grown onto a sample by evaporation of material. In addition to single-crystal surfaces, many researchers have investigated vicinal, i.e. stepped, surfaces as well as the surfaces of polycrystalline and disordered materials. 

For fine powders that tend to bridge or stick and are of low bulk density, some form of forced feed, such as the tapered screw feeder shown in Figure 9, must be used to deaerate, precompact, and pressurize the feed into the nip. Large machines are available with up to five screw feeders to spread the flow across the roUs, and vacuum hoppers are also used to remove air when densifying low density feeds. 

Preflmdizing has the advantage of reducing the volume of conveying air needed consequently, less power is required. The characteristics of the rest of this system are similar to those of regular pressure-or vacuum-type conveyors. Of special concern is the tendency of material to stick to and build up on surfaces of the system compo-... 

Before 1950, it was impossible to examine the true structure of a solid surface, because, even if a surface is cleaned by flash-heating, the atmospheric molecules which constantly bombard a solid surface very quickly re-form an adsorbed monolayer, which is likely to alter the underlying structure. Assuming that all incident molecules of oxygen or nitrogen stick to the surface, a monolayer will be formed in 3 x 10 second at 1 Torr (=1 mm of mercury), that is, at 10 atmosphere a monolayer forms in 3 s at 10 Torr, or 10 atmosphere but a complete monolayer takes about an hour to form at 10 Torr. The problem was that in 1950, a vacuum of 10" Torr was not achievable lO Torr was the limit, and that only provided a few minutes grace before an experimental surface became wholly contaminated. 

Because of the sensitivity of chromium(II) to air oxidation, synthetic work on these systems requires the use either of vacuum-line techniques12 or of a nitrogen-filled box,6 or both. This synthesis describes the preparation of chromium(II) complexes using a combination of a closed ground-glass filter stick 18 and a nitrogen-filled box.6 The filter stick enables preparations, filtrations, and recrystallizations to be carried out... 

The experimental approach discussed in this article is, in contrast, particularly amenable to investigating solvent contributions to the interfacial properties 131. Species, which electrolyte solutions are composed of, are dosed in controlled amounts from the gas phase, in ultrahigh vacuum, onto clean metal substrates. Sticking is ensured, where necessary, by cooling the sample to sufficiently low temperature. Again surface-sensitive techniques can be used, to characterize microscopically the interaction of solvent molecules and ionic species with the solid surface. Even without further consideration such information is certainly most valuable. The ultimate goal in these studies, however, is to actually mimic structural elements of the interfacial region and to be able to assess the extent to which this may be achieved. 

WARNING Do not just stick the vacuum adapter on the end of the condenser and hope that it will not fall off and break. 

If you want to measure the pressure in your vacuum distillation setup, you ll need a closed-end manometer. There are a few different types, but they all work essentially the same way. I ve chosen a stick type (Fig. 75). This particular model needs help from a short length of rubber tubing and a glass T to get connected to the vacuum distillation setup. 

If the mercury level in the inner tubes goes lower than that of the outer tube it does NOT mean that you have a negative vacuum. Some air or other vapor has gotten into the inner stick, and with the vacuum applied, the vapor expands and drives the mercury in the inner tube lower than that in the outer tube. This manometer is unreliable and you should seek a replacement. 

Suppose, by luck of the draw, you ve had to prepare and purify 1-octanol (B.P. 195°C). You know if you simply distill 1-octanol, you run the risk of having it decompose, so you set up a vacuum distillation. You hook your setup to a water aspirator and water trap and attach a closed-end stick manometer. You turn the water for the aspirator on full-blast and open the stick manometer. After a few minutes, nothing seems to be happening. You pinch the tubing going to the vacuum distillation setup, (but not to the manometer) closing the setup off from the source of vacuum. Suddenly, the mercury in the manometer starts to drop. You release the tube going to the vacuum distillation setup, and the mercury jumps to the upper limit. You have air leaks in your vacuum distillation setup. 

Surface characterization studies by X-ray photoelectron spectroscopy (XPS) were conducted using DuPont 650 and Perkin Elmer 5300 instruments. Samples were prepared by placing solid material on double stick adhesive tape, or by allowing solvent to evaporate from an acetone dispersion of a suspension placed on a stainless steel probe. A magnesium anode was used as the X-ray source (hv 1253.6 eV). The temperature of samples during the analysis was approximately 30-40°C and the vacuum in the analysis chamber was about 10 torr. Potential... 

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