Charcoal outgassing

The charcoals outgassed at 750°C retained appreciable amounts of combined oxygen capable of evolving CO. These charcoals show less preference for ethanol... 

FIGURE 2.27 Adsorption-desorption hysteresis in adsorption of water vapor on sugar charcoal outgassed at different temperatures. (Source Puri, B.R. and Myer, Y.P., J. Sci. and Ind. Res., India, 16B, 52, 1957. With permission.)... 

Figure 12-40. Equilibrium capacity of activated coconut-shell charcoal for benzene. Gas volume measured in ml at standard conditions (0°C, 760 mm Hg) charcoal outgassed at 550 C before tests. Data of Coolidge (1924)...

On immersion of even well outgassed charcoal in water we must imagine that many of the micropores are not filled with water and thus an apparent diminution of the density of the solid occurs. These micropores cannot of course be empty for otherwise there is no reason why the liquid wetting the sides of the tubes should not fill them. If the micropores still contain small traces of gases not removed by the process of outgassing these will be compressed into pockets at the ends of the blind tubes, the pressure in the case of a micropore of 100 A. diameter would be about sixteen atmospheres. 

The IUPAC/SCI/NPL programme on surface area standards examined a number of carbon blacks, activated charcoals, and silicas, and in the resulting publication [33] the results obtained in a number of laboratories were compared. As a result, two carbon blacks and two silicas lacking microporosity were accepted as standards. A major conclusion of this work, namely that outgassing conditions determine results obtained with high-area solids, was reinforced by the unsuccessful attempts made by the European Union s Community Bureau of Reference to obtain reproducible results with silica gels intended as reference standards [8e]. 

Figure 9.13. Nitrogen adsorption isotherms ar 77 K (a) and corresponding as plots (b) for charcoal cloth JF012 after prc-adsoiption of nonane followed by outgassing at indicated temperature (after Carrott etal., 1989).

FIGURE 1.24 Composite adsorption isotherms for various samples of charcoal from sugar and coconut shell from methanol-benzene mixtures. Curves (a) original charcoals, (b) out-gassed at 400°C, (c) outgassed at 750°C, (d) outgassed at 1100°C. (After Puri, B.R., in Chemistry and Physics of Carbon, Vol. 6, P.L. Walker, Jr., ed., Marcel Dekker, New York, p. 191, 1970. With permission.)... 

FIGURE 3.17 Composite isotherms from methanol-benzene solutions on various charcoals. 0 1 = original sugar charcoal 2 = 1000°C outgassed sugar charcoal 3 = PVC charcoal A 4 = H202-treated sugar charcoal. (From Bansal, R.C. and Dhami, T.L., Carbon, 15, 153, 1977. With permission.)... 

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