Harkins and Jura method

The heat measured in step (3) corresponds to the adsorption of an unknown amount of vapor on the carbon surface. Now, in case of a wetting system, we know that the conditions are then fulfilled to have a multilayer adsorbed. This means that the heat measured in step (4) corresponds to the immersion energy of a precovered solid, so that it can be used for the surface area determination by the modified Harkins and Jura method [7]. The addition of the heats measured in steps (3) and (4) after suitable correction leads to the usual immersion energy. If the full wetting is not reached at saturation pressure it is then needed to proceed to step (5). More details about this procedure and the way to get experimental data are described elsewhere [9]. 

The extent of the solid surface for a given liquid—solid system, the immersion energy increases with the surface area (applications measurement of the surface area either by comparison, using a reference material, or by applying a modified absolute Harkins and Jura method). 

Gas Adsorption Method. A technique for the determination of specific SURFACE (q.v.) variants of the method include the brunauer, emmett ani> TELLER METHOD (q.V.) and the HARKINS AND jura method (q.v.). 

Harkins and Jura Method. A gas-adsorption method for the determination of the specific surface of a powder. The sample is first evacuated and then exposed to a vapour near to its... 

This assumption was invoked by Harkins and Jura [21] in applying the method, with some success, to a nonporous powder. A concern, however, is... 

Harkins and Jura (Ref 5) have described an improved modification of the basic B.E.T. method for the calculation of surface area. Eigsti Dwiggins(Ref 16) evaluated this method for the determination of the particle size of chemical delay compns vs other methods, as described earlier in this article (see Table 9)... 

Data taken from the adsorption leg of the isotherm of Figure 17.11 are listed in the first two columns of the following table. Test the applicability of the following equilibrium theories (a) Langmuir (b) infinite BET and (c) Harkins and Jura. From (a) and (b) obtain estimates of the surface area of the adsorbent and compare the values with that obtained by the point B method. One molecule of nitrogen adsorbed on alumina occupies 0.162 nm2. 

In some instances Harkins and Jura found two or more linear regions of different slopes when ln(P/Po) is plotted versus W. This indicates the existence of two or more liquid condensed states in which different molecular packing occurs. When this situation appears, the slope that gives best agreement with an alternate method, for example, the BET method, must be chosen. Alternatively, the temperature or the adsorbate can be changed to eliminate the ambiguity. 

In addition to the relative method, Harkins and Jura have also developed an absolute method for surface area measurement which is independent of... 

An important contribution made by the Harkins and Jura absolute method, however, must not be overlooked. Their measurements of some specific surface areas give confirmation to the value of 16.2 for the cross-sectional area of nitrogen. This value, when employed with the BET theory, gave exactly the same specific surface area as the HJ absolute method. 

The second method, that described by Harkins and Jura (14), applies the semiempirical equation... 

Figure 6.2. Principle of the Harkins and Jura absolute method for determining the surface area.

The total surface area needs to be known to determine the change of internal surface energy from the heat of immersion. This is often done by adsorption measurements [94,83]. An alternative method was suggested by Harkins and Jura 92. They proposed not to immerse a clean solid but to expose the solid first to the vapor of the liquid. If the liquid wets the solid at the saturating vapor... 

Whilst the use of the Kelvin equation can be questioned in the case of smaller mesopores, this is not the case in the present case where, on the contrary, the pores are situated in the upper mesopore range. However, use of the BJH method implies the use of a t-curve. On commercial adsorption equipment, the software proposes the use of several equations to fit the t-curve. In the present case, the Harkins and Jura equation or Halsey equation is proposed. Unfortunately neither of these fit the original t-curve data of de Boer very well. 

Nevertheless, bearing in mind the above-mentioned reservations, it is possible to interpret the pore size distributions obtained using the BJH method with the Harkins and Jura t-curve (Fig. 2). Firstly, it would seem obvious that the peaks centred on 4 nm relate to the closing of the hysteresis at around p/p° = 0.42. One should ignore these, as they are artefacts due to the non-stability of the nitrogen meniscus under these conditions. However, the peaks observed in the case of mlO and mVT4, centered on 40 nm and 100 nm respectively, are significant. It is these peaks that can be confidently used for further comparison. 

Textural Parameters. Adsorption-desorption isotherms of N2 at 77K were determined in a Micromeritics ASAP 2010 with a micropore system. Prior to measurement, the samples were outgassed at 140 C for at least 16 h. The specific surface area was determined by the BET method, assuming that the area of a nitrogen molecule is 0.162 nm [12]. Micropore volume was calculated by the t-plot method using the Harkins and Jura [13] thickness. We used model isotherms calculated from density functional theory (DFT) to determine the pore size distributions and cumulative pore volume of the pillared samples by taking the adsorption branch of the experimental nitrogen isotherm, assuming slit-like pores [14]. 

The BET theory, of course, is still the basis for the most widely used method of determining surface areas. Especially after the confirmatory work of Harkins and Jura (46), it now seems clear that the determination of surface areas from the BET theory is fortunately not very sensitive to the simplifying assumptions in the BET model, and that BET surface areas are the best that can be had at the present time. 

More extensive and accurate data and additional calculations are necessary to obtain s , e , and from isotherm data over what is required to get the differential energy and entropy from the isosteric equation. The first complete calculation of ss, e and , as well as the differential quantities, has recently been made by Hill, Emmett, and Joyner (95). This paper shows in detail how the methods of this section can be applied in practice. Using heats of immersion, Harkins and Jura (96) made earlier equivalent calculations, but the relationship of their calculated quantities to the thermodynamic functions of the adsorbed molecules was not pointed out until recently by Jura and Hill (92). 

The adsorption isotherm yields the amount of gas adsorbed on the surface. Unless the molecular area occupied by the adsorbed gas is known, the adsorption isotherm yields only relative surface areas rather than the absolute values. This is the reason for using only one gas (nitrogen or krypton) to determine the surface areas of different solids. However, Harkins and Jura [45] developed an absolute method of... 

Areo3a of Solids Calculated by the New Method of Harkins and Jura and by that of Brunauer, Emmett and Teller ... 

Table III, Harkins and Jura, J. Am. Chem. Snc. A6, 1360 (1944) with a column of calculations for the areas by B.E.T. method using water isotherms with an assumed cross-section of 11.3 A. for the water molecule. 

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