McLeod

This is sometimes made of mirror glass in order to eliminate the error due to parallax, t Manufactured by Edwards High Vacuum Ltd. This is essentially a form of McLeod gauge. 

If the pump is a filter pump off a high-pressure water supply, its performance will be limited by the temperature of the water because the vapour pressure of water at 10°, 15°, 20° and 25° is 9.2, 12.8, 17.5 and 23.8 mm Hg respectively. The pressure can be measured with an ordinary manometer. For vacuums in the range lO" mm Hg to 10 mm Hg, rotary mechanical pumps (oil pumps) are used and the pressure can be measured with a Vacustat McLeod type gauge. If still higher vacuums are required, for example for high vacuum sublimations, a mercury diffusion pump is suitable. Such a pump can provide a vacuum up to 10" mm Hg. For better efficiencies, the pump can be backed up by a mechanical pump. In all cases, the mercury pump is connected to the distillation apparatus through several traps to remove mercury vapours. These traps may operate by chemical action, for example the use of sodium hydroxide pellets to react with acids, or by condensation, in which case empty tubes cooled in solid carbon dioxide-ethanol or liquid nitrogen (contained in wide-mouthed Dewar flasks) are used. 

CM Topham, A McLeod, E Eisenmenger, JP Overmgton, MS Johnson, TL Blundell. Erag-ment ranking in modelling of protein structure. Conformationally constrained environmental ammo acid substitution tables. J Mol Biol 229 194-220, 1993. 

With the rotary and diffusion pumps in tandem, aided by a liquid-nitrogen trap, a vacuum of 10 Torr became readily attainable between the wars by degrees, as oils and vacuum greases improved, this was inched up towards 10 Torr (a hundred-billionth of atmospheric pressure), but there it stuck. These low pressures were beyond the range of the McLeod gauge and even beyond the Pirani gauge based on heat conduction from a hot filament (limit Torr), and it was necessary to... 

Lighting Research Center. (1998). Mary McLeod Bethune Elementary School, Rochester City School District, Rochester, New York. DELTA Portfolio, 2(3). Troy, NY Rensselaer Polytechnic Institute. 

Interactions between metal ions and living organisms in sea water. K. Kustin and G. C. McLeod, Top. Curr. Chem., 1977, 69,1-37 (136). 

The pressure of gas in the source chamber was determined from the pressure in the gas reservoir (measured with a McLeod gage) by using Dushman s (11) relations for viscous and molecular flow in the higher and lower ranges of pressure, respectively. 

Additional experimental verification that molecules of hydrogen in condensed phases are in states approximating those for free molecules is provided by the Raman effect measurements of McLennan and McLeod.13 A comparison of the Raman frequencies found by them and the frequencies corresponding to the rotational transitions / = 0—>/ = 2 and/= 1— / = 3 (Table II) shows that the intermolecular interaction in liquid hydrogen produces only a very small change in these rotational energy levels. 

Techniques other than UV-visible spectroscopy have been used in matrix-isolation studies of Ag see, for example, some early ESR studies by Kasai and McLeod 56). The fluorescence spectra of Ag atoms isolated in noble-gas matrices have been recorded (76,147), and found to show large Stokes shifts when optically excited via a Si j — atomic transition which is threefold split in the matrix by spin-orbit and vibronic interactions. The large Stokes shifts may be explained in terms of an excited state silver atom-matrix cage complex in this... 

Kasai and McLeod (57, 58) also studied a series of bimetallic diatomics, AgM (M = Mg, Ca, Sr, Be, Zn, Cd, or Hg), by ESR spectroscopy. For all of these species, the hyperfine coupling to the Ag nucleus was found to be isotropic. It was shown that the unpaired electron resides in an orbital resulting essentially from an anti-bonding combination of the valence s orbitals of the Ag and M atoms. A typical spectrum is shown in Fig. 13. 

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