Packing area water

Dgg. The total number of molecules in the SB region can be calculated by consideration of the close packing of water molecules in the area of a sphere consisting of the ion plus the first layer. Thus, the number of molecules of cross-sectional area will be given as... 

Fig. 5. The packing status of Form II complex (a) Both channel and cage type packing systems of 3 CyD molecules. Barbital and water molecules are drawn by full lines and circles, (b) The stacking of B CyD(2) and B--CyD(3) molecules in the channel type packing area, (c) The stacking of 3 CyD(4) and shifted 3-CyD(l ) molecules in the cage type packing area. Barbital molecule included in 3-CyD(4) is denoted by an asterisk.

Airington and Patterson [39] spread the fluoroalcohol H(CF2)iqCH20H on water and determined the area occupied per molecule from the force-area curve of the spread monolayers (Fig. 4.5). By extrapolating the upper part of the curve to zero pressure, a close-packed area of 29 A was obtained. The fluorocarboxylic acid H(CF2)i2COOH was spread on water and on 0.01 hydrochloric acid (Fig. 4.6). The force-area curve obtained for hydrochloric acid agrees with the curve shown for the fluoroalcohol in Fig. 4.5. When the fluorocarboxylic acid film on hydrochloric acid was recompressed, the curve was duplicated. The compression of the fluorocarboxylic acid film on water gave a smaller area per molecule than obtained on acid. A second compression gave even a smaller area (19 A"). 

Example 8.5-4 Overall mass transfer coefficients in a packed tower We are studying gas absorption into water at 2.2 atm total pressure in a packed tower containing Berl saddles. From earlier experiments with ammonia and methane, we believe that for both gases the mass transfer coefficient times the packing area per tower volume is 18 Ibmol/hrft for the gas side and 530 Ibmol/hrft for the liquid side. The values for these two gases may be similar because methane and ammonia have similar molecular weights. However, their Henry s law constants are different 75 atm for ammonia and 41,000 atm for methane. What is the overall gas-side mass transfer coefficient for each gas ... 

In Table 5.3, is compared with the total hydroxyl concentration (Ni, + N ) of the corresponding fully hydroxylated, sample. The results clearly demonstrate that the physical adsorption is determined by the total hydroxyl content of the surface, showing the adsorption to be localized. It is useful to note that the BET monolayer capacity n JH2O) (= N ) of the water calculated from the water isotherm by the BET procedure corresponds to approximately 1 molecule of water per hydroxyl group, and so provides a convenient means of estimating the hydroxyl concentration on the surface. Since the adsorption is localized, n.(H20) does not, of course, denote a close-packed layer of water molecules. Indeed, the area occupied per molecule of water is determined by the structure of the silica, and is uJH2O) 20A ... 

FIG. 14-61 Liq uid distribution in a 6-in column packed with 1/4-in broken-stone packing. Increments of radius represent equal-annual-area segments of tower cross section. Central-point inlet. Water rate = 500 lb/(b-fr). Air rate = 810 lb/(b-ft ). To convert pounds per bour-square foot to kilograms per second-square meter, multiply by 0.00L356 to convert inches to centimeters, multiply by 2.54. (Data from Baker, Chilton, and Vernon, in Shetxuood and Pigford, Absorption and Extraction, 2d ed., McGraw-Hill, New York, 1952. )... 

Liquid Dispersion Spray columns are used with slurries or when the reaction product is a solid. The absorption of SO9 by a hme slurry is an example. In the treatment of phosphate rock with sulfuric acid, offgases contain HF and SiF4. In a spray column with water, solid particles of fluorosilic acid are formed but do not harm the spray operation. The coefficient /cl in spray columns is about the same as in packed columns, but the spray interfacial area is much lower. Considerable backmixing of the gas also takes place, which helps to make the spray volumetri-caUy inefficient. Deentrainment at the outlet usually is needed. 

Equipment suitable for reactions between hquids is represented in Fig. 23-37. Almost invariably, one of the phases is aqueous with reactants distributed between phases for instance, NaOH in water at the start and an ester in the organic phase. Such reac tions can be carried out in any kind of equipment that is suitable for physical extraction, including mixer-settlers and towers of various kinds-, empty or packed, still or agitated, either phase dispersed, provided that adequate heat transfer can be incorporated. Mechanically agitated tanks are favored because the interfacial area can be made large, as much as 100 times that of spray towers, for instance. Power requirements for L/L mixing are normally about 5 hp/1,000 gal and tip speeds of turbine-type impellers are 4.6 to 6.1 i7i/s (15 to 20 ft/s). 

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