Glass vacuum system

Similarly, the chemical reactivity of these two chlorine oxyfluorides differs vastly whereas ClFsO is extremely reactive and cannot be handled even in a well-dried glass vacuum system, FCIO3 reacts only slowly with water. 

It reacts rapidly with glass or quartz and, therefore, cannot be handled in standard glass vacuum systems (226). It reacts with numerous materials... 

A continuous-flow reactor with a fixed catalyst bed was employed under pressurized conditions. The reactor was made of stainless steel with an inner diameter of 6 mm. All products and unreacted feed materials were withdrawn in the gaseous state from the reactor through a heated pressure let-down valve, A quantitative analysis of the products was carried out by gas chromatography. The time factor, which corresponds to contact time, is expressed by W/F, where W is the weight of catalyst (g) and F is the total flow rate of feed (mol/hr). Chemisorption of H2, CO and methyl iodide (Mel) were measured by a conventional glass vacuum system. 

The manipulation of all volatile compounds is carried out in a Pyrex-glass vacuum system [consisting of four manifolds (volume about 150 mL) interconnected by a central manifold and pumping system and two sets of U-traps connecting adjacent manifolds], using conventional techniques.12 Greaseless Teflon-... 

All adsorptions were performed in a glass vacuum system. The pressures were measured with an MKS capacitance manometer. 

All reductions were carried out on a glass vacuum system under static H2 (Linde 99.999%) which was dried by passing through Drierite and molecular sieves prior to exposure to the sample. H2 uptakes were monitored using a capacitance manometer (MKS Instruments Inc.) N2 isotherms at 77 K were performed on the same vacuum system using pre-purified grade N2 (Linde) which was dried prior to use. Oxidations were performed under flowing 02 (Linde 99.999%) at 773 K and under static O2. The samples were evacuated at 623 K to a residual pressure of less than 5 X 10 5 torr prior to reduction or N2 isotherm measurements. 

The home-made heat-flow calorimeter used consisted of a high vacuum line for adsorption measurements applying the volumetric method. This equipment comprised of a Pyrex glass, vacuum system including a sample holder, a dead volume, a dose volume, a U-tube manometer, and a thermostat (Figure 6.3). In the sample holder, the adsorbent (thermostated with 0.1% of temperature fluctuation) is in contact with a chromel-alumel thermocouple included in an amplifier circuit (amplification factor 10), and connected with an x-y plotter [3,31,34,49], The calibration of the calorimeter, that is, the determination of the constant, k, was performed using the data reported in the literature for the adsorption of NH3 at 300 K in a Na-X zeolite [51]. 

This equation is a powerful tool for the description of the adsorption data in microporous material. In Figure 6.11, the Dubinin plot of the adsorption isotherm in the range 0.001 < P/P0 < 0.03, describing the adsorption of NH3 at 300 K in the natural clinoptilolite sample HC is shown (see Table 4.1) [25], The adsorption data reported in Figure 6.11 were determined volumetrically in a home-made Pyrex glass vacuum system, consisting of a sample holder, a dead volume, a dose volume, a U-tube manometer, and a thermostat [25,31], It is evident that, in the present case, the experimental data is accurately fitted by Equation 6.20. 

In Figure 6.12 [2,25], the plot of the linear form of the osmotic isotherm equation, with B = 0.5, using adsorption data of NH3 adsorbed at 300 K in an homoionic magnesium natural zeolite sample labeled CMT (see Table 4.1), is shown. The adsorption data reported in Figure 6.12 were determined volumetrically in a Pyrex glass vacuum system, previously described in the case of the Dubinin equation [25,31], With this plot, it is possible to calculate the maximum adsorption capacity of this zeolite, which is m = Na = 5.07mmol/g and b = UK = -0.92 (Torr)05. 

The catch to the vacuum method is that you must have a controlled boil without which the material and/or solvent are liable to be sprayed all over your vacuum system. Although a solvent can easily be pumped out of a vacuum system, it can cause serious problems if it remains in contact with stopcock grease, O-rings, or mechanical and/or diffusion pump oils. Any particulate material deposited within a vacuum line can only be removed from the vacuum line by disassembly and cleaning. With a glass vacuum system, such a cleaning may be difficult or impossible. 

What typically happens with a glass vacuum system is that first a mechanical pump removes a great deal of the loose, or free, gas particles. Then, greater vacuum is achieved with the combination of a diffusion pump (or similarly fastpumping unit) and traps that remove or bind up the various vapors within the system (for example, oil, mercury, and water). The only way a system can achieve a vacuum lower than 10 6 to 10 7 torr is if the pump can remove water vapor faster than the water vapor can leave the walls. Most diffusion pumping systems cannot achieve this goal, but even if they could, there is such a substantial amount of water vapor within the glass that, unless the walls are baked, a better vacuum cannot be obtained. 

For years, glass diffusion pumps provided (relatively) easy attachment to a glass vacuum system (but rather difficult removal), are mostly free from attack by corrosive substances, provide easy observation of the materials inside the pump, and can be cleaned (with some difficulty). 

Mechanical gauges can be easily attached onto metal vacuum systems, however, due to the construction materials of mechanical gauges, it is often impossible to make a direct seal onto a glass vacuum system. If necessary, a Swagelok or Cajon Ultra-Torr may be used for making a glass-to-metal seal (see Sec. 3.1.5). The glass-to-metal seal may then be fused onto the vacuum system. 

Among the items that may be initially checked on a glass vacuum system are to ensure that all plug numbers of glass vacuum stopcock plugs match their respective barrel numbers. As mentioned on page 193, these numbers must match. Another factor to consider with vacuum stopcocks is whether they are old, worn, or just defective. Additionally, you should examine that the vacuum stopcocks have been properly and recently greased/... 

R. Rondeau, Design and Construction of Glass Vacuum Systems, Journal of... 

The balance is a modification of the Nernst-Donau (20) apparatus which appeared most readily adaptable to an all glass vacuum system and to the techniques involved in the measurements to be made. 

The annular space between the two tubes is evacuated by a mercury diffusion pump and a Hyvac forepump, and the inner tube is connected to an all glass vacuum system. 

It is a volatile white solid (m.p., 43°C). The vapor pressure is given by the expression log Pmm = -2096/71 + 9.145. It is soluble in ether even at -78°C. Dissociation into NSF3 and HF increases rapidly with temperature and the presence of moisture. It is stable when stored at -78°C and can be handled in a dry glass vacuum system. In aqueous base, hydrolysis occurs. 

Two very different kinds of pump fluids have been employed in diffusion pumps. For many years, mercuiy diffusion pumps, were used in small laboratory-bench glass vacuum systems. Mercury pumps are now seldom used owing to the health hazards associated with mercury and the high probability of contamination of the vacuum system with mercury unless a cold trap is used (the vapor pressure of mercury at room temperature is —1.5 mTorr). The oil diffusion pump eliminates the safety hazard and can serve for both small glass and larger metal vacuum systems. 

The gases can be introduced into the vessel by the use of an all-metal system or a Kel-F lubricated-glass vacuum system equipped with a fluorine-resistant pressure gagef and a soda-lime trap to protect the vacuum pump. The author s preference for an overall system is the all-metal transfer line and the reaction... 

The evacuation of vessels is an important process and has many applications in teaching, research and industry. Although engineers and physicists make extensive use of metal systems, which are outside the scope of a glassblower, glass vacuum systems are widely used in chemistry laboratories for many short-term research projects and for teaching and demonstration purposes. 

Propene (SIAD), benzene and cumene (FLUKA) were products of high purity (99.5%). The propene/benzene mixtures were prepared in a glass vacuum system. 

All manipulations may be carried out in a standard glass vacuum system using greased stopcocks the reaction vessel itself is required to withstand internal pressure of 2-3 atmospheres and is best fitted with a greaseless stopcock. Caution. Shield well when under pressure. 

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