Vacuum method

Everhart, E., 1996, Making Corrector Plates by Schmidt s Vacuum Method, Appl. Optics 5,713... 

Evaporation at atmospheric pressure, called the free release static coating method, has not been as widely used or evaluated as the vacuum method [146,226,234]. The experimental , arrangement is... 

Vacuum was applied to shift the equilibrium forward by removal of the activated alcohol formed [30, 31, 37, 38]. In the enzymatic polycondensation of bis(2,2,2-trifluoroethyl) sebacate and aliphatic diols, the polymer with Mw of more than 1 x 104 was obtained using lipases CC, MM, PPL, and Pseudomonas cepacia lipase (lipase PC) as catalyst and lipase MM showed the highest catalytic activity [37]. Solvent screening indicated that diphenyl ether and veratrole were suitable for the production of the high molecular weight polyesters under vacuum. In the PPL-catalyzed reaction of bis(2,2,2-trifluoroethyl) glutarate with 1,4-butanediol in veratrole or 1,3-dimethoxybenzene, periodical vacuum method improved the molecular weight (Mw 4 x 104) [38]. 

Ion Beam Deposition The most commonly used vacuum method for the rapid deposition of films (thin or thick) is sputtering (2M. This can be combined with ion beam techniques in a variety of ways (25) including (Figure 18) ion beam sputter deposition (IBSD) eg of oxide films or of hard carbon (26). In reactive systems the reactive gas is added to the argon ion beam. The properties of the deposited materials are modified substantially by varying the gas composition (Figure 19). 

The methodology of surface electrochemistry is at present sufficiently broad to perform molecular-level research as required by the standards of modern surface science (1). While ultra-high vacuum electron, atom, and ion spectroscopies connect electrochemistry and the state-of-the-art gas-phase surface science most directly (1-11), their application is appropriate for systems which can be transferred from solution to the vacuum environment without desorption or rearrangement. That this usually occurs has been verified by several groups (see ref. 11 for the recent discussion of this issue). However, for the characterization of weakly interacting interfacial species, the vacuum methods may not be able to provide information directly relevant to the surface composition of electrodes in contact with the electrolyte phase. In such a case, in situ methods are preferred. Such techniques are also unique for the nonelectro-chemical characterization of interfacial kinetics and for the measurements of surface concentrations of reagents involved in... 

Describe the pressure-vacuum method of filling an IR cell equipped with inlet and outlet ports. 

The specimens should wherever possible be examined in a configuration corresponding to their later application - components for vacuum applications using the vacuum method and using the positive pressure method for parts which will be pressurized on the inside. 

Today leak tests for vacuum systems are usually carried out with helium leak detectors and the vacuum method (see Section 5.7.1). The apparatus is evacuated and a test gas is sprayed around the outside. In this case it must be possible to detect (on the basis of samplings inside the apparatus) the test gas which has passed through leaks and into the apparatus. Another option is to use the positive-pressure leak test. A test gas (helium) is used to fill the apparatus being inspected and to build up a slight positive pressure the test gas will pass to the outside through the leaks and will be detected outside the device. The leaks are located with leak sprays (or soap suds, 5.4.5) or - when using He or H2 as the test gas - with a leak detector and sniffer unit (5.7.2). 

Alfred E. Stock. Former director of the Chemical Institute of the Tech-nische Hochschule of Karlsruhe. Former student of Henri Moissan and author of an excellent biographical sketch of him. Visiting lecturer at Cornell University in 1932. He is an authority on the high-vacuum method for studying volatile substances, the chemistry of boron, the preparation and properties of beryllium, and chronic mercurial poisoning. 

Although the next item is mainly concerned with non-vacuum methods, it is worth a close look ... 

In order to analyse, by polarography compounds which have been purified in a h.v.s., it is not necessary to have a cell which operates under vacuum. Methods have been described whereby a solution made up under vacuum can be admitted via a burette fitted with a pressure equaliser to a polarography cell operating at atmospheric pressure under nitrogen or, preferably, under argon (Kabir-ud-Din and Plesch, 1978). See also Chapter 3. 

All ampules rejected by the dye-vacuum method must also be rejected on the ampule crack detection machine. 

Comparisons with the Dye-Vacuum Method on Actual Product Lots... 

To compare the effectiveness of the machine with the dye-vacuum method, production batches are passed through the crack detection machine and then through the dye-vacuum chamber. The hnal check after that is carried out again on the crack detection machine. 

The crack detection machine shall recognize more bad ampules than the dye-vacuum method and shall reject an equivalent number of good ampules as the dye-vacuum method. 

Tire rate of heat input to the frozen material is a function of the operating-vacuum method of heal transfer and the properties of ihe dried product. The operating vacuum determines the pressure difference and. in turn, the rate of mass transfer, which must be in balance with the rate of heat input. Otherwise, either melting will occur at the sublimation interface and the purpose of freeze-drying will be defeated or the sublimation temperature will decrease and the cost of processing will increase. 

Another dry process is run continuously [57], The dry, powdered reaction mixture is fed into a rotary furnace kept at 180°C, and the dry product is discharged into a drum at a yield of 96% [36,37], A vacuum method for the preparation of relatively pure CuPc is described in [58],... 

With vacuum systems, the accepted method ( vacuum method) of leak detection/measurement is to evacuate the object/system under test and with the MSLD coupled via its inlet port, apply He externally and observe the response from the MSLD. 

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. 

Narrow polydispersity diblock copolymers of PS—PMMA and PS—PEO were produced by anionic polymerization using conventional high-vacuum methods. The average AB copolymer composition was determined by NMR (model EM30, Varian, UK). Narrow dispersity PS and PMMA standards (Polymer Laboratories) were used for both instrument and SEC column calibrations. Samples were prepared as nominally 1-mg/mL solutions in the eluent and spiked with toluene as a flow rate marker before full loop 100-fxh injection. Each copolymer was analyzed three times. 

Liquid ADMET monomers often become so viscous that magnetic stirring is impossible. There are several solutions to this. One is to attach a strong horseshoe or other magnet to a mechanical stirrer and rotate it very slowly under the vessel and temperature bath to slowly agitate the polymer melt. Another solution is to use a high viscosity mechanical stirrer if the polymer is a viscous melt Vacuum adapters for the stirring shaft are available, so that the vacuum method may be used with mechanical stirrers. 

The Elmore vacuum method was an outcome of the above. This is an oil flotation process, as distinct from an oil separation process. The pulp of ore and water, mixed with a very small quantity of oil and enough sulphuric acid to make tho mixture slightly acid, is exposed to a partial vacuum the air dissolved in the water rises up through it in the form of bubbles, floating the oiled sulphides to the top, whence they are drawn off. From a 2 to 3 per cent, copper ore, concentrates of up to 20 per cent, can be produced. 

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