Surface area calculation

Molecular area, a ,(Ar), of argon at 77 K on nonporous oxides (Argon BET plots constructed withp (liquid) BET surface areas calculated from nitrogen isotherms, with a (Na) = 16-2 A )... 

Wynne-Jones and Marshfound somewhat similar results with a number of carbons made by pyrolysis of eight organic polymers at a series of temperatures. The isotherms of Nj at 77 K and of COj at 195 K were measured, and the apparent surface area calculated by the usual BET procedure. (Owing to the microporous nature of the solids, these figures for area will be roughly proportional to the uptake at saturation and therefore... 

The effective tube length, L, of the bundle for surface area calculations is the mean of the tube lengths between the outside tubes and the inside tubes. See Figure 10-27A. 

There are various methods for the determination of the surface area of solids based on the adsorption of a mono-, or polymolecular layer on the surface of the solid. These methods do not measure the particle diameter or projected area as such, but measure the available surface per gram or milliliter of powder. The surface measured is usually greater than that determined by permeability methods as the latter are effectively concerned with the fluid taking the path of least resistance thru the bed, whereas the adsorbate will penetrate thru the whole of the bed as well as pores in the powder particles. These methods appear to be more accurate than surface areas calculated from weight averages or number averages of particle size because cracks, pores, and capillaries of the particles are included and are independent of particle shape and size... 

Sca = Surface area calculated from microscopic data... 

Theoretical Pt surface area calculated from Pt particle sizes. 

Fig. 8. Calculated values of (top) /(0), (center) /(75), and (bottom) J (653) for acid-unfolded apoMb, pH 2.3, 25°C. The horizontal lines show the mean values of J (75) (0.19 ns rad-1) and /(653) (0.020 ns rad-1), and the 10% trimmed mean value of J (0) (0.97 ns rad-1). The average buried surface area, calculated using the values of Rose and co-workers (Rose et al., 1985) and averaged over a seven-residue window, is also shown in the center figure (solid line, no data points, right-hand scale). Black bars indicate the positions of the helices in the folded structure of myoglobin.

Pigna M, Colombo C, Violante A (2003) Competitive sorption of arsenate and phosphate on synthetic hematites (in Italian). Proceedings XXI Congress of Societa Italiana Chimica Agraria SICA (Ancona), pp 70-76 Quirk JP (1955) Significance of surface area calculated from water vapour sorption isotherms by use of the B. E. T. equation. Soil Sci 80 423-430 Rancourt DG, Fortin D, Pichler T, Lamarche G (2001) Mineralogical characterization of a natural As-rich hydrous ferric oxide coprecipitate formed by mining hydrothermal fluids and seawater. Am Mineral 86 834-851 Raven K, Jain A, Loeppert, RH (1998) Arsenite and arsenate adsorption on ferrihydrite kinetics, equilibrium, and adsorption envelopes. Environ Sci Technol 32 344-349... 

Specific surface area calculated by multiplot BET method. b Total pore volume calculated by BJH method. c Average pore diameter. 

Figure 2 shows a typical multipoint BET plot for bendroflumethiazide, and Table 2 summarizes the parameters and calculations used to obtain the surface area for this compound. The single-point surface area calculated from a PIP0 of 0.3108 is also presented in Table 2. Good agreement is evident between the two methods, considering the C constant given in Table 2 for this sample. 

C. The Meaning of Specific Surface Areas Calculated from... 

Table 5.2 Comparison of specific surface areas calculated from the ascending branch of the water isotherms of selected cellulosic materials by the BET theory, the ct procedure and the Zimm and Lundberg (ZL) cluster theory.

Dl, particle size calculated from the Sherrer equation Sjh, specific surface area calculated assuming cubic particles and a density of LaCo03 equal to 7.29 D2, equivalent cubic particle size calculated from BET surface area. P, perovskite C, cobalt oxide. 

Different gases (such as nitrogen) are normally used as the adsorbate if the surface area of a solid needs to be examined. The gas is cooled by liquid nitrogen. The tap to the sample bulb is opened, and the drop in pressure is determined. In the surface area calculations, a value of 0.162 nm2 is used for the area of an adsorbed nitrogen molecule. 

Body surface area calculation square root (height in cm x body weight in kg divided by 3600). High doses required in infants < 1 yr because of kinetic variability. 

For children who can swallow capsules and for whom the current capsule formulations allow appropriate weight or body surface area calculated dosing, additional options to replace LPV/r include SQV/r and IDV/r. 

The conclusion, based on the above factors, is that surface areas calculated from equation (4.13) usually give different results depending upon the adsorbate used. If the cross-sectional areas are arbitrarily revised to give surface area conformity on one sample, the revised values generally will not give surface area agreement when the adsorbent is changed. 

The surface area calculated by the above method is modelless and assumes no specific pore geometry. 

The surface area calculated in equation (11.10) represents the total area of all pores between ambient pressure (r = 7.25 /im) and 60000 psia (r = 0.00178 nm). 

Unlike surface area calculations, the volume distribution function and all subsequently discussed functions are based on the model of cylindrical pore geometry. 

Dividing the surface area calculated in the example by typical aggregation numbers gives the area per head group at the surface of the core. Using n values of 50 and 100 gives 0.69 and 0.35 nm2 per group, respectively, quite plausible numbers in view of the behavior of surfactants in monolayers. 

BET surface area m2/g ASTM D 3037 DIN 66131 DIN 66132 total specific surface area calculated from the nitrogen adsorption isotherm by using the BET equation... 

Recent work indicates that surface areas from COrisotherms on coal should be determined by the Langmuir rather than the BET equations. Surface areas calculated using the Langmuir equation were 174 and 200 sq. meters/gram for the Pittsburgh and Pocahontas coals, respectively. 

Table E1.5. BET Data for Specific Surface Area Calculation of Ca( OHh.

It can be seen in Figure 5 that when the amount of silicon in SAPO-37 is increased, the conversion increases up to 44 Si/unit cell and then decreases. In order to avoid the possible contribution of the free alumina (Table I), present in minor amounts in these samples, the first order kinetic rate constant per unit of BET surface area (calculated at cat/oil = 0.4) has been plotted as a function of the silicon content, Figure 6. The same behavior is observed. This behavior can be explained in an analogous way as in the case of zeolites, but considering that the acid sites in SAPO are related to the introduction of silicon. Therefore, in SAPO, the number and density of acid sites will be related to the number of silicon atoms. Consequently,... 

Van der Waals surface area calculated using a connection table approximation Van der Waals volume calculated using a connection table approximation Van der Waals volume calculated using a grid approximation... 

One must identify and enumerate the interactions that characterize each of the states relevant to the folding/unfolding partition function. This can be accomplished from the structure, if known, utilizing accessible polar and apolar surface area calculations and specific interactions as described below. 

As has been discussed recently (Murphy etal., 1992), the formalism developed by Lee (1991) predicts not only the convergence behavior discussed by the author (i.e., when the apolar and polar contributions to the enthalpy are identical). For the case in which the buried polar area per residue is constant it also predicts convergence at the point at which the apolar contribution to the enthalpy is zero. In Fig. 3 we have plotted AH0 versus ACp normalized either per residue (Fig. 3a) or per buried total surface area (Fig. 3b), in order to compare the results of the two approaches. It is clear that the linearity is better when the data are normalized to the number of residues than when they are normalized to the buried surface area. This is presumably due to variabilities in the surface area calculation. The slope of the line in Fig. 3a is —72.4, which corresponds to a convergence temperature, Th, of 97.4°C for this set of proteins. If the above analysis is correct, then this temperature corresponds to The value of AH is 1.32kcal (mol res)-1 or 33.6 cal (mol A2)-1 of polar surface area. 

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