Effect of surface area

FIGURE 11 Effect of surface area on rate of drug release from polymer discs prepared from 3,9-bis(ethylidene-2,4,8,10-tetraoxaspiro-[5,5]undecane) and a 50 50 mole ratio of trans-cyclohexane dimethanol and 1,6-hexanediol at pH 7.4 and 37 C. Polymer contains 4 wt% drug and 0.2 wt% poly(sebasic anhydride). (From Ref. 20.)... 

In Lab 17.1, you learned about the effect of temperature and concentration on reaction rate. Another factor that affects reaction rate is the amount of surface area of the reactants. If a chemical reaction is to take place, the molecules of reactants must collide. Changing the amount of surface area modifies the rate of collision, and, thus, the rate of reaction. If surface area increases, collision frequency increases. If surface area decreases, so does the number of collisions. In this lab, you will examine the effect of surface area on rate of reaction. You will also determine how a combination of factors can affect reaction rate. 

Many studies have been conducted to look at the effect of particle size on dissolution and the bioavailability of insoluble drugs [69-84], One study looked at the effect of surface area on the bioavailability of griseofulvin, which has an aqueous solubility of 0.014 mg/mL and an average dose of 500 mg. The authors showed that an approximately sixfold increase in the surface area led to a 2.5-... 

Other studies have been performed to investigate the effect of surface area and tablet lubricant efficacy. In a comparison study between sodium stearyl fumarate and magnesium stearate, it was found that sodium stearyl fumarate was effective as a lubricant to about the same degree as magnesium stearate [15]. It was also reported that the lubricating properties correlated better to the surface area of the lubricant than to the amount of lubricant used. A micronized lubricant was more efficient than a coarse fraction, and it was suggested that the surface area be standardized to obtain reproducible effects. 

You can also use simple collision theory to explain why increasing the surface area of a solid-phase reactant speeds up a reaction. With greater surface area, more collisions can occur. This explains why campfires are started with paper and small twigs, rather than logs. Figure 6.8 shows an example of the effect of surface area on collision rate. 

Borggaard, O.K. (1983) Effect of surface area and mineralogy of iron oxides on their surface charge and anion-adsorption properties. Clays Clay Min. 31 230-232 Borggaard, O.K. (1983 a) The influence of iron oxides on phosphate adsorption by soil. J. 

Fig. 39 Plots showing the effect of surface area factor on the extent of property improvement. Symbols represent experimental values, and the lines are their apparent fitting. Encircled data points are taken from unpublished research work on NR latex-based NA nanocomposites. Vertical dotted line indicates the critical point...

Solid-state investigation of immiscible phase diagrams and the effect of surface area and carbon on them. 

Heterogeneous photocatalytic reaction products and their production rates depend on the kind of photocatalysts. As noted above, each photocatalyst powder has different properties. In the case of the sonophotocatalytic reaction, products or their yields also depend on the kind of photocatalysts. The effect of surface area on product ratio was discussed in section (12.2.1C). The influence of surface area on product ratio was noted, but factors other than surface area must be introduced to explain the difference in product ratios. It is known that there are several crystal structures of Ti02. The major structures are anatase and rutile. 2... 

Fig. 3.1 Schematic representation of effect of surface area on photocatalytic activity. If constant density and complete absorption of incident photons are assumed, the number of e and h+ is independent of particle size, i.e., surface area. The amount of the substrates adsorbed on the photocatalyst increases with the increase in the surface area, which, therefore, enhances the reaction of e and h+ with the substrates.

We use equations (12.69) to (12.75) when we want to calculate the effect of surface area on a total thermodynamic property. But we also want to know relationships between the different thermodynamic properties of the surface. With the aid of equations (12.57) to (12.63), in combination with equations (12.69) to (12.76), we can derive such relationships. For example, to obtain an equation for Us, we differentiate equation (12.57) and get... 

Properties estimated by interpolation within the range of conditions over which a QSAR was calibrated should be reliable, but extrapolations beyond this range cannot be made with certainty. A similar restriction applies to experimental variables factored out of the training set data before deriving the QSAR (e.g., the effect of pH on oxidation of phenolic compounds, or the effect of surface area on reductions with Fe°). 

Pederson, L. R. Buckwalter, C. Q. McVay, G. L., "The Effects of Surface Area to Solution Volume on Waste Glass Leaching." PNL-SA-10306, Pacific Northwest Laboratory,... 

Another consequence of the effect of surface area on vapor pressure is that large regions of liquids will grow at the expense of small droplets. Also, in... 

Detailed studies on the effect of surface-area and heat of wetting are not available. However, it is known that the heat of wetting of silica gel, which is a highly porous material, is approximately 30 cal per g (approximately 200 times that of coarse quartz as shown in Table 46). 

An anatase sample P2 of specific surface area 55 m2/g was heated at 600°C for 3 h and the specific surface area was found to decrease to 25m2/g. The transformation characteristics of these two samples were studied (fig. 4b). Since the growth in the crystallite size is negligible in the 400-600°C region and the particle size is nearly the same for the two samples, the observed effect may be interpreted as due to the effect of surface area. It can be seen from fig. 4b that the effect of surface... 

Effects of Surface Area Consider a single large block of ice melting. Will it melt faster than a set of smaller ice cubes of equal mass People who want the ice in their coolers to melt more slowly will use a larger block of ice. A larger block of ice has less surface area, and thus less of the ice is exposed to the warmer temperatures present in the cooler. Smaller ice cubes of the same mass will melt faster because they collectively have more surface area exposed. Chemists often avoid putting whole chunks of salts in their reactions. To increase the speed of the reaction, the solids are chopped up into a finer powder rather than left as larger pieces. 

THE RESULTS OF SCREENING TESTS ON ISOBUTANE/TRANS-2-BUTENE ALKYLATION OVER VARIOUS RESIN/BF complexes at 40 C and 2.6 C WHSV. (Effect of Surface Area of Resin). ... 

Figure 3.2 a- Effect of surface area Effect of surface area and polarizability on boiling point... 

The physical form of sulfide mineral components may vary from a state of fine sub-division to massive form with consequent variation in available surface area, rmd this may be further affected by the mode of association of the gangue material. The effect of surface area on rates of mineral sulfide oxidation is well established (Torma et al., 1970, 1972 Torma and Legault, 1973). 

Figure 17. Effect of Surface area on soft coke.

V.L. Cherginets, T.G. Deineka, O.V. Demirskaya and T.P. Rebrova, Potentiometric Investigation of Oxide Solubilities in Molten KCl-NaCl Eutectic. Effect of Surface Area of Solid Particles on the Solubilities, J. Electroanal. Chem. 593 (2002) 171-178. 

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