Sodium films vapour

I. Sodium. Probably the best known active hydrogen remover is sodium. When used outside a vacuum system, for instance as sodium wire to dry solvents, the sodium is little more than a support for a skin of sodium hydroxide. Inside a vacuum system, however, one can prepare films of sodium metal and one can prepare really clean sodium which will give a colourless solution of sodium ethoxide (see Section 5.2.1.). The method of making sodium films for the removal of acidic compounds from liquid reagents will be described and also a very much less well-known method involving sodium vapour and colloidal sodium. 

To resolve the problem applying methods of collimated atom beams, equilibrium vapour as well as radioactive isotopes, the Hall effect and measurement of conductivity in thin layers of semiconductor-adsorbents using adsorption of atoms of silver and sodium as an example the relationship between the number of Ag-atoms adsorbed on a film of zinc oxide and the increase in concentration of current carriers in the film caused by a partial ionization of atoms in adsorbed layer were examined. 

Sodium ignites in fluorine gas but is inert in the liquefied gas [1]. Cold sodium ignites in moist chlorine [2] but may be distilled unchanged in the dry gas [1]. Sodium and liquid bromine appear to be unreactive on prolonged contact [3], but mixtures may be detonated violently by mechanical shock [4]. Finely divided sodium luminesces in bromine vapour [1], Iodine bromide or iodine chloride react slowly with sodium, but mixtures will explode under a hammer-blow [1]. Interaction of iodine pentafluoride with solid sodium is initially vigorous, but soon slows with film-formation, while that with molten sodium is explosively violent... 

The first high-intensity sodium lamp was introduced in Europe in 1931. Figure 9.26 shows a schematic view of a sodium lamp it comprises a glass shell containing sodium vapour at low pressure, metal electrodes to generate a current, and neon gas. The pressure inside the tube is at a relatively low pressure of 30 Pa, so some of the sodium evaporates to become a vapour. The inner side of the lamp is coated with the remainder of the metallic sodium as a thin film. 

The second method of developing surface cracks is to expose the surface to hot sodium vapour.1 With various kinds of glass, this treatment produces visible markings (Fig. 45). It is interesting that neither the metallic films nor the sodium vapour show scratches or drawing marks etching with hydrofluoric acid, on the other hand, shows scratches, but does not show the Griffith cracks,2 as Andrade has called them. 

A major advance in technique has permitted the calorimetric determination of heats of adsorption of hydrocarbons on thin single-crystal surfaces of metals. " Films of about 200 mn thickness are grown epitaxially by vapour deposition on the surface of a sodium chloride crystal cut to expose the desired face it is then dissolved in water, and the film, the surface of which mimics that of the crystal, is then rescued. Its small thermal mass means that the heat liberated is rapidly equilibrated throughout the metal, and the temperature rise can be measured by a remote infrared detector. By using a pulsed molecular beam, simultaneous estimates of sticking probability can be made. Heats of adsorption of hydrocarbons on supported metals at various temperatures have also been reported (Section 4.5). 

Binions, R., Carmalt, C. J. and Parkin, 1. P. (2004) Aerosol-assisted chemical vapour deposition of sodium fluoride thin films. Thin Solid Films 416,469-70. 

Fabra, M.J., Talens, P., Chrralt, A. Influence of calcium on tensile, optical and water vapour permeability properties of sodium caseinate edible films. J. Food Eng. 96, 356-364 (2010)... 

Figure 3.2 Infrared spectra of chemically treated polymers (a) spectrum of sodium polyacrylate before and after exposure to hydrogen chloride vapour and the heated film of the hydrogen chloride treated acrylate, sodium polyacrylate film, sodium polyacrylate film exposed to HCl vapour, sodium polyacrylate film exposed to HCl vapour and then heated (b) spectra of copolymer of acrylic acid and vinylidene chloride and the film after exposure to ammonia vapour, acrylic acid-vinylidene chloride copolymer film, acrylic acid-vinylidene chloride copolymer film exposed to ammonia vapour. Source Author s own files)...

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