Traps vacuum-line

Caution. The reagents used in this synthesis are air-sensitive. The synthesis and associated sample handling should be carried out under rigorous inert conditions. This requires the use of an inert-atmosphere glovebox (He atmosphere, < 1 ppm total H.fO and O2) (Vacuum Atmospheres Corp.) and a liquid-nitrogen trapped vacuum line ( <10 torr). 

Fig. 8. Magnetherm reactor central electrode, A secondary circuit, B grounding electrode, C refractory lining, D carbon lining, E primary material feed, F slag taphole to FeSi recovery, G vacuum line, H water spray ring, I condenser, cmcible, K trap, L filter, M and transformer, N.

Manipulations involving materials sensitive to air or water vapour can be carried out by these procedures. Vacuum-line methods make use of quantitative transfers, and P(pressure)-V(volume)-T(temperature) measurements, of gases, and trap-to-trap separations of volatile substances. 

When 5.00 mL of ether has been delivered by the syringe pump, the pump is shut off The reactor is allowed to run an additional 15 min before the fluorine and the mercury arcs ate shut off. The preaerosol furnace, the evaporator heater unit, and the coolant pump are shut off. Once the system approaches ambient conditions, all the helium carriers are shut off and the product trap valves are closed The product trap and its Dewar flask filled with liquid nitrogen are removed to the vacuum line where the trap is evacuated... 

The contents of the trap are transferred to the glass vacuum line by vacuum distillation. The contents are condensed into a 150-mL stainless steel cylinder containing an excess of 20% aqueous sodium carbonate and allowed to react with occasional shaking for 24 h The products are fracbonated through 5, -78, -131, and -196 °C traps under active pumping (3 pm of Hg) The product (8.5 g) is collected in the -131 °C tiap. The remaining vacuum line traps were virtually empty. 

Complex I is formed if l,4-difluoro-2,3,5,6-tetramethyl-l,4-diboracyclohexa-2,5-diene and Ni(CO>4 are condensed with dry, degassed toluene into a tube on a vacuum line. When the tube is allowed to warm to RT for 30 min, the complex can be trapped as yellow crystals at — 30 C when all volatile material is pumped off. The sandwich... 

The catalyst for the in situ FTIR-transmission measurements was pressed into a self-supporting wafer (diameter 3 cm, weight 10 mg). The wafer was placed at the center of the quartz-made IR cell which was equipped with two NaCl windows. The NaCI window s were cooled with water flow, thus the catalyst could be heated to 1000 K in the cell. A thermocouple was set close to the sample wafer to detect the temperature of the catalyst. The cell was connected to a closed-gas-circulation system which was linked to a vacuum line. The gases used for adsorption and reaction experiments were O, (99.95%), 0, (isotope purity, 97.5%), H2 (99.999%), CH4 (99.99%) and CD4 (isotope purity, 99.9%). For the reaction, the gases were circulated by a circulation pump and the products w ere removed by using an appropriate cold trap (e.g. dry-ice ethanol trap). The IR measurements were carried out with a JASCO FT/IR-7000 sprectrometer. Most of the spectra were recorded w ith 4 cm resolution and 50 scans. 

Cold finger refrigerant traps are often used in vacuum lines as a substitute for the more efficient total immersion traps which, however, tend to cut down the pumping speed of the system. In constructing a cold finger trap a Dewar seal is first made, then, before... 

Two 4 1 cylindrical glass(QVF) vessels with stainless steel end plates, serve as reservoirs(Figure 1) for surfactant solution(B) and water(9). Facility is available to evacuate these vessels as required by means of a rotary vacuum pump with glass cold trap in line to minimise water vapour. Another pipeline permits supply of pure nitrogen, or other gas, at low pressure, to the vessels, to provide a blanket, as desired. Proper operation and safety from over pressure is ensured by a pressure relief valve(10 in Figure 1) and the pressure gauge(P in Figure 1). 

Isobutylene (Philips Research Grade) was purified as described [17] by distillation on a vacuum line through a trap containing sodium at 350 °C. It was stored as liquid on a sodium mirror. Solutions in methyl bromide were made up by distilling the required quantities of solvent and isobutylene from hanging burettes along a vacuum line into a reservoir with Teflon tap, which was subsequently cut from the vacuum line and fused to a burette with Teflon tap which was then fused to the main vacuum manifold as shown in Figure 1. 

The nitrosobenzenes 293a,b (2.00 mmol) in an evacuated 250-mL flask were connected via vacuum line with a 250-mL flask containing NO (1 bar, 11 mmol) that had been freed from traces of NO2 by storing over 4-chloroaniline. After 24 or 48 h rest in a refrigerator at 4 °C, excess gas was recovered in a cold trap at 77 K. Pure 294 was quantitatively obtained. 

Dicyclohexylborane bumps during the drying step, and the checkers found that it is advantageous to use a vacuum adapter containing a glass frit and an auxiliary cold trap to prevent contamination of the vacuum line with the product. 

Fig. 4. Schematic vacuum system for metal atom reactions. X represents the stopcock or Teflon-in-glass valve. Satisfactory components (for a general discussion of vacuum line design see References 1 and 4) forepump, 25 L/min free air capacity diffusion pump, 2 L/sec main trap is removable and measures about 300 mm deep main manifold has a diameter of about 25 mm, stopcock or valve in manifold should be at least 10 mm substrate container is removable container with 1-2 mm Teflon-in-glass needle valve connected to bottom of container. Connection between this needle valve and the reactor may be 1/8 in. od. Teflon tubing is used. Alternatively, the substrate may be added as shown in Fig. 3.

With the reaction flask closed off from the vacuum line, the bath at -196° is replaced by a bath at -111° (CS2 slush bath), which results in a gradual increase in pressure to approximately 50 torr as observed on the blow-out manometer. As the reaction proceeds, the pressure slowly diminishes and stabilizes after about 2 hours. When no further pressure change is observed, the reaction mixture is frozen again at -196°. The reaction vessel is then warmed by removing the cold bath, while the contents are subjected to pumping of the volatile products through successive cold traps at -126 (methylcyclohexane slush bath), -140, (Skelly F) and-196°. 

The vacuum line used in the following preparations is similar to that described by Shriver.14 It consists of a pump station, a main reaction manifold with six reaction stations, a fractionation manifold with four U-traps and a reaction station at each end, a McLeod Guage, and a Topler pump. The pump station employs a two-stage mechanical forepump and a two-stage mercury diffusion pump. Operating vacuum is 1.0 X 10"S torr. Teflon valves are employed throughout. 

In the schematic diagram of the vacuum line (Fig. 2.1) a U-bend is shown between the main tap T, and the manifold, which has two functions (a) It lends an extra element of mechanical flexibility to the system by absorbing small movements at the traps or along the main manifold (WL or WL ) which might otherwise lead to fracture and (b) it acts as a sink for non-volatile residues in the line and for grease which may be washed away from the taps 7, 7 and 7. ... 

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