Specific surface area, changes constant

For KSF montmorillonite, the number of silanol and aluminol sites was found to be less by an order of magnitude. It is in accordance with the ratios of specific surface areas (10 m2/g for KSF montmorillonite, and 93.5 m2/g for montmorillonite [Istenmezeje]). This is an interesting observation because KSF montmorillonite is an acid-treated substance. Thus, it seems that acidic treatment causes the decrease of the layer charges (the CEC decreases montmorillonite content of Ca-, Cu-, and Zn-montmorillonites is 91%, and that of KSF montmorillonite is 53%). The acidic treatment, however, does not change the nature of silanol and aluminol sites, the stability constants of the edge charge reactions remains the same, and the number of edge sites is proportional to the specific surface area. 

Hurd, D. C. and Theyer, F. Changes in the physical and chemical properties of biogenic silica from the central equatorial Pacific-- . Solubility, specific surface area, and solution rate constants of acid-cleaned samples, 211 230, in COLbb, Jr., T. R. P., editor) "Analytical Methods in Oceanography," Adv. Chem. Ser. 147, 1975. 

As noted in the title, the first section of this research deals with the changes in solubility, specific surface area, and solution rate constants of the substances studied. Since it is important to understand the extent to which these properties change with changes in crystal form, we first... 

The most convenient method of study of adsorption at small coverage is gas chromatography. By this method it is possible to determine the constant of adsorption equilibrium (retention volume) and from the retention volumes at different temperatures to calculate the heat of adsorption and changing of differential standard entropy of adsorption. If the support for fullerene crystals is the adsorbent with inert and small specific surface area so the retention of compounds will be determined by intermolecular interaction of compounds with fullerene crystal surface. The deposition of fullerene crystals on support surface is quite difficult owing to small solubility of fullerene in organic solvents [21, 22] as well as small vapour pressure of fullerene [23]. 

Fig. 4. Changes in specific surface area and crystallinity index by enzymatic hydrolysis (reproduced from [18]). Specific surface area (SSA) and crystallinity index (CrI) change quickly as enzymatic hydrolysis proceeds until leveling out at a constant level. Initial enzymatic action breaks cellulose into smaller particles (increased SSA) and attacks amorphous regions (increased CrI)... 

Exposing porous silica to water or water vapor at an elevated temperature causes changes in the pore structure of the silica by hydrothermal treatment. As a result, the specific surface area diminishes, and the average pore diameter increases however, the specific pore volume remains constant. The magnitude... 

We can see that when the stirring rate is increased so much that the specific surface area is increased Hvefold (assuming the mass transfer coefficient does not change much), the reaction time for reaching 99% conversion of B would go down from 3300 to 2S(X) s. An increase in pressure would increase the solubility of A and reduce the reaction time accordingly. An increase in temperature would mainly affect the reaction rate constant, ff this were increased by a factor of 5, and the other variables were not changed, the Hatta number

still applicable. The necessary reaction time for 99% conversion of B would become 1460 s. When both the reaction rate constant and the specific surface area were increased by a factor of 5, the reaction time for 99% conversion of B would be only 660 s. 

The main conclusion of these studies is that clear functional dependences can be obtained for series of samples by varying sequentially their structural characteristics and dissolution conditions. Such dependences interrelate the dissolution rate with the heat treatment temperature of solid phases, their specific surface area, pore structure and structural changes associated with transition from amorphous to polycrystal and even monocrystal state. Meanwhile, a strong dependence of the dissolution rate on the number of defects in the crystal structure of soHd phases leads to another regularities an increase in the heat treatment temperature may decrease the dissolution rate of samples at a constant value of specific surface area samples with a greater number of struetural defects and a smaller specific surface area may dissolve faster than the samples having a much larger surface area but a defectless structure. 

With constant total porosity of a HCP, the c-s-f on micro level can be changed by changing the specific surface area of the pores. We not only got the clear view of the role of size and shape of pores on the micro level and that on meso level to effect the strength of HCP, but also obtained the critical specific surface area, above which the total porosity would have no effect on the strength(2). 

---