Nitrogen curves

Fig. 1. Changes in the adsorption activity of ferric oxide after heating in oxygen (curve o) and in nitrogen (curve x). The quantities of ferric oxide required for adsorption of a fixed quantity of the adsorbate are shown on the abscissa. It will be seen that the adsorption capacity of a ferric oxide preparation declines more rapidly if it has been preheated in nitrogen than if it has been heated in oxygen.

Fio. 25. Isosteric heats of adsorption at 0°K. for nitrogen on rutile (curve A) and for argon on rutile (curve B) contribution due to the quadrupole attraction of nitrogen (curve C) contributions due to the electrostatic polarization of argon (curve D) and to the dispersion forces (curve E) [data from Morrison el al. (280)]. 

Fig. 10. Influence of hydrogen-oxygen ratio on third limit without additive (curve 1), with 100 mm nitrogen (curve 2) and 100 mm carbon dioxide (curve 3) at 586 °C in KCl coated vessel, 5.5 cm diameter (after Willbourn and Hinshelwood [27]). (By courtesy of The Royal Society.)...

We consider next another example. Years ago, gold faces were cut, mechanically polished—either with alumina or with diamond paste —and then electropolished. No AES was available to check the final chemical state of the faces. When solutions containing only ions, which adsorbed slightly, were deaerated with nitrogen, curves for all samples were of the type exemplified by the solid line of Fig. 17. When molecular hydrogen was bubbled in these solutions, for samples prepared with alumina , curves were of the type shown in curve 1 of Fig. 17 for samples prepared with diamond paste , curves were typically as shown in curve 2 of Fig. 

Fig. 43. Elongation against temperature under constant load obtained with high-pressure polyethylene samples subjected to various doses of 7-rays in vacuo and in an atmosphere of nitrogen [429]. Curve 0, unirradiated standard curve 1, 0.33 Mrad at 0.91 rads"1 in vacuo curve 2, 0.41 Mrad at 2.4 rads"1 in nitrogen curve 3, 0.68 Mrad at 2.4 rad s"1 in vacuo curve 4, 1.1 Mrad at 2.8 rad s"1 in vacuo curve 5, 1.3 Mrad at 0.91 rads"1 in vacuo curve 6, 1.8 Mrad at 9.2 rad s"1 in vacuo curve 7, 2.0 Mrad at 2.4 rads"1 in nitrogen curve 8, 1.6 Mrad at 2.4 rad s"1 in vacuo curve 9, 5.4 Mrad at 9.2 rad s"1 in vacuo.

At about 100°C, a weak endothermic peak due to the loss of sorbed water was observed in the nylon 66 curve. In air there was an exothermic reaction initiating at about 1855C and forming a small endothermic peak at a A7. n of about 250°C, the latter being caused by the fusion of the polymer (mp about 255°C). In nitrogen, the exothermic peaks were not present, suggesting thal the air reactions were due to an oxidation reaction. The two endothermic peaks in the nitrogen curve were due to the fusion of the polymer and to the... 

Fig. 10 Current passing through the upstream amperometric oxygen sensor at different flow rates for two solutions. Curve a, the solution was purged with a gas mixture of 10 % oxygen and 90 % nitrogen curve h, the solution was purged with air [8]...

Fig. 2.11 Curves of the differential enthalpy of adsorption of nitrogen against surface coverage 0 (= for samples of Sterling carbon black heated at the following temperatures (a) 1500°C (fc) 1700°C (c) 2200 C (d) 2700°C. The curve for 2000°C was similar to (c). but with a lower peak. The calorimetric temperature was 77-5, 77-7, 77-4, 77-4 K in (a), (fc), (c) and (d) respectively.

Fig. 2.15 Isosteric heat of adsorption of nitrogen on molecular (low-evergy) solids and on carbons (high-energy solids), plotted as a function of i/n . (A) Diamond (B) gruphitized carbon black. P.33 (D) Benzene (E) Teflon. The curve for amorphous carbon was very close to Curve (A). (Redrawn from a Figure of Adamson . )...

In view of the widespread use of nitrogen and argon in surface area and porosity studies, data for the construction of the standard a,-curves for these adsorbates on hydroxylated silica, are given in Table 2.14 (p. 93) for nitrogen and in Table 2.15 for argon. From the arguments of Section 2.12, these should be adequate for other oxides such as alumina, if high accuracy is not called for. 

Figure 3.26(a) and (h) gives results for nitrogen on a compact of silica. Curve (a) is a comparison plot in which the adsorption on the compact (ordinates) is plotted against that on the uncompacted powder (abscissae) there is a clear break followed by an increased slope, denoting enhanced adsorption on the compact, at p/p° = 0-15, far below the lower closure point ( 0-42) of the hysteresis loop in the isotherm (curve (b)). A second compact, prepared at 64 ton in" rather than 130 ton in", showed a break, not quite so sharp, at p/p° = 0-35. 

Eveluetion of specific surface from Type IV isotherms of nitrogen, from the aree under the curve of log(pVp) against n... 

To test the Brunauer approach, it was necessary to use standard isotherms of nitrogen having the same c-constants as the experimental isotherms of Table 4.7. Since nitrogen isotherms with c > 10 have not been reported in the literature, theoretical isotherms corresponding to the c-values of Table 4.6 were calculated by Brunauer s modification of Anderson s equation, and standard a,-curves were constructed from them. The corresponding a,-plots appear in Fig. 4.15 they are no longer parallel... 

Fig. 4.15 a,-plots for the adsorption of nitrogen on a sample of microporous titania, before and after nonane treatment. Curve (A), before nonane pre-adsorption curves (B), (C), (D) after nonane pre-adsorption, followed by outgassing at (B) 250° (C) 150°C (D) 25°C. The a,-plots were based on standard nitrogen isotherms having the same c-values as the isotherms of... 

Fig. 4.18 Plot of log (.x/(mg g" )) against log (p°/p) for the adsorption of nitrogen at 77 K on the samples of manganese dioxide referred to in Fig. 4.16. Outgassing temperature (A) room (B) 393 K (C)443 K (D) 493 K. For the points denoted by V in Curve A, a sample was outgassed at 493 K and charged with nonane before the final outgassing at room temperature. (Courtesy Lee and Newnham.)...

It is, however, possible to use a Type 111 isotherm of an adsorptive G, say, on a solid S for the evaluation of the specific surface of S, provided a standard sample of the solid is available to enable one to construct a standard a,-curve of G on S. The area of the standard sample must be known, usually from the nitrogen isotherm. 

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