Pumps high vacuum

Example The vacuum system of non-benchtop mass spectrometers consists of one to three rotary vane pumps and two or three turbo pumps. Rotary vane pumps are used for the inlet system(s) and as backing pumps for the turbo pumps. One turbo pump is mounted to the ion source housing, another one or two are operated at the analyzer. Thereby, a differentially pumped system is provided where local changes in pressure, e.g., from reagent gas in Cl or collision gas in CID, do not have a noteworthy effect on the whole vacuum chamber. 

Cryopumps adsorb (freeze) residual gas to a surface cooled to the temperature of liquid nitrogen. They are highly efficient and silent and provide clean vacuum, but cannot be operated without interruptions to recover the adsorber. Cryopumps are typically operated in combination with turbo pumps because they are only started after high vacuum conditions are reached. Otherwise, the adsorber would soon be saturated. 

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Mercury is extensively used in various pieces of scientific apparatus, such as thermometers, barometers, high vacuum pumps, mercury lamps, standard cells (for example the Weston cell), and so on. The metal is used as the cathode in the Kellner-Solvay cell (p. 130). 

Hafnium hydride is brittle and easily cmshed to very fine particle sizes. It is usually produced as an intermediate in the process of making hafnium powder from massive hafnium metal. The hydrogen can be removed by high vacuum pumping above 600°C. 

Fuels, Lubricants, and Transmission Fluids. Polyol esters of neopentanoic acid have been used as high vacuum pumping hquids that are stable in chemically aggressive environments (70). Esters such as 6- -ani1inophenoxy)hexy1 pivalate are used as antioxidants for synthetic ester lubricants (71). PivaUc anhydride [1538-75-6] has been claimed as an antiknock additive for gasoline (72). 

Hydroxyflavone [577-85-5] M 238.2, m 169-170 , 171-172 . Recrystd from MeOH, EtOH or hexane. Also purified by repeated sublimation under high vacuum, and dried by high vacuum pumping for at least one hour [Bruker and Kelly J Phys Chem 91 2856 1987]. 

Based on rough vacuum process pumps. Use 25 ft/s for high vacuum pumps. 

The volatile metal is separated by distillation and condensed. Mercury is the only metallic element that is liquid at room temperature (gallium and cesium are liquids on warm days). It has a long liquid range, from its melting point of — 39°C to its boiling point of 357°C, and so it is well suited for its use in thermometers, silent electrical switches, and high-vacuum pumps. 

When all the violet dye is off the column, begin to collect and evaporate 10-ml. fractions. Two or three fractions, which on evaporation yield little or no residue, will precede the appearance of the 7-benzene hexachloride. Continue to collect 10-ml. fractions and evaporate until no more 7-benzene hexachloride is obtained. Stop the column operation, dissolve the several 7-benzene hexachloride residues with a minimum quantity of n-hexane, and pour into a tared 125-ml. Erlenmeyer flask. Evaporate under vacuum, using the solvent evaporator, at 60° and finally at room temperature for 5 minutes with a high vacuum pump. Release the vacuum, wipe the flask with a clean, moist towel, and weigh after allowing the flask to come to equilibrium near the balance. Calculate the percentage of 7-benzene hexachloride in the original sample. 

Prior to functionalization the carbon nanomaterials were washed in concentrated nitric acid (65% Fisher Scientific) for 8 h using a Soxhlet device in order to remove catalyst residues of the nanomaterial synthesis as well as to create anchor sites (surface oxides) for the Co on the surface of the nanomaterials. After acid treatment the feedstock was treated overnight with a sodium hydrogen carbonate solution (Gruessing) for neutralization reasons. For the functionalization of the support media with cobalt particles, a wet impregnation technique was applied. For this purpose 10 g of the respective nanomaterial and 10 g of cobalt(II)-nitrate hexahydrate (Co(N03)2-6 H20, Fluka) were suspended in ethanol (11) and stirred for 24 h. Thereafter, the suspension was filtered via a water jet pump and finally entirely dried using a high-vacuum pump (5 mbar). 

Source of high-energy electrons, ion accelerator, magnetic/electrostatic analyser, detector and recorder, high vacuum pumping system. 

Some of the procedures described in the following chapters had to be carried out under an inert atmosphere, nitrogen or argon, to minimize contact with oxygen and moisture. It is then necessary to use Schlenk techniques including the utilization of a vacuum line connected to a high vacuum pump and an inert gas inlet. The use of such equipment requires experience in working under anhydrous conditions. 

The use of an Aldrich Kugelrohr oven allowed for distillation in a large flask. This is advantageous, since decomposition may ensue above 100°C.2 For this reason distillation has to be carried out at as low a pressure as possible. In most cases the submitters used a turbo pump, but application of a normal high vacuum pump with a distillation temperature of 90°C at 0.04 mm is also possible. 

Busch, K.L. High-Vacuum Pumps in Mass Spectrometers. Spectroscopy 2001, 16, 14-18. 

A 250-ml three-necked flask is fitted with metal stirrer, nitrogen inlet, Vigreux column (30 cm), and condenser for distillation with a vacuum adapter and round flask as receiv-er.The high-vacuum pump must be connected over a cold trap with the vacuum adapter. 

The throughput value is important in determining the size of the backing pump in relationship to the size of a high vacuum pump with which it is connected in series in order to ensure that the backing pump will be able to take off the gas moved by the high vacuum pump (see Section 2.32). 

At an intake pressure of p = 1 -10 mbar the pumping speed for the high vacuum pump as stated in the catalog is about 100 l/s, subsequently 50 % of this is 50 l/s. Therefore the pumping speed of the backing pump must amount to at least... 

If the high vacuum pump is only to be used at intake pressures below 10 mbar, a smaller backing pump will do in the case of the example given this will be a pump offering a pumping speed of 6 m /h. If the continuous intake pressures are even lower, below 10" mbar, for example, the required pumping speed for the backing pump can be calculated from equation 2.41a as ... 

Fig. 3.20 Schematic diagram of a high vacuum pump system with optionai operation of a Roots pump or a diffusion pump...

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