Glass surface area

Table III. Melt Glass Surface Area and Size Analysis...

Some of the fibers in each batch were aged in humid air, in deionized (DI) water, or in silane solution. All of the aging was carried out at 35°C for 30 days. A commercial (Blue-M) controlled atmosphere chamber held the relative humidity (RH) at 70% and the temperature at 34°C. The silane solutions were prepared by adding the requisite amount (1% by volume) of unhydrolyzed y-APS (A-1100 Union Carbide) to triply distilled water or to acetic acid solution. A hydrolysis time of approximately 8 h was allowed prior to adding fibers to the solution. This yielded solutions at pH 10 and pH 4, respectively. The fibers were suspended in Nalgene containers, where the glass surface area-to-solution volume ratio was fixed at 50 cm1. In all cases, the fibers were dried in air at 75°C and the solutions were analyzed for their Si, Al, Ca, and B contents. Table 1 presents the results of these solution analyses. 

Jar tests are not without their drawbacks in that it is often difficult to reproduce the temperature and pressure conditions encountered in the field. In addition, extrapolation of jar test performance to operational conditions can be subject to serious scale-up problems. Table 3 illustrates the differenees in jar test performance which can occur due to wall effects with the glass test containers. The tests were carried out in a variety of glass containers with different volume to surface area ratios. The recoveries are a function of the glass surface area of the container to the... 

The surfaces of multicomponent glasses are significantly altered when exposed to aqueous solutions the extent of the alteration layer is dependent on a variety of parameters, including the glass composition, the duration of exposure, the temperature and pH of the solution, and the ratio of the glass surface area to the solution volume. This section is not intended to be a discussion of the aqueous corrosion of glass rather, several different studies are mentioned to provide an overview of the analytical tools that characterize such interactions. 

This is a disproportionation reaction, and is strongly catalysed by light and by a wide variety of materials, including many metals (for example copper and iron) especially if these materials have a large surface area. Some of these can induce explosive decomposition. Pure hydrogen peroxide can be kept in glass vessels in the dark, or in stone jars or in vessels made of pure aluminium with a smooth surface. 

Fig. 7. A bead filter, one of many types of biological filters, shown in association with a laboratory-scale recirculating water system. Small plastic beads inside the fiber glass chamber provide surface area for colonisation by bacteria that convert ammonia to nitrate.

Surface area can accelerate the decomposition of chlorine dioxide up to a point, but sufficient area appears to inhibit catalytic decomposition by adsorption of the intermediates. For example, the presence of fluffed wood pulp or glass wool is reported to stop the explosive decomposition of chlorine dioxide (27). 

Dry filters are usually deeper than viscous filters. The dry filter media use finer fibers and have much smaller pores than the viscous media and need not rely on an oil coating to retain collected dust. Because of their greater resistance to air flow, dry filters must use lower filtration velocities to avoid excessive pressure drops. Hence, dry media must have larger surface areas and are usually pleated or arranged in the form of pockets (Fig. 17-64), generally sheets of cellulose pulp, cotton, felt, or spun glass. 

As a result of the larger flues and the restric ted surface area per unit of gas passed, regenerators employed with this type of furnace exhibit much lower efficiency than would be reahzed with smaller flues. In view of the large amount of iron oxide contained in open-hearth exhaust gas and the alkah fume present in glass-tank stack gases, however, smaller checkerbrick dimensions are considered imprac tical. 

A circular specimen of about 38-mm (I.5-iu) diameter is a convenient shape for laboratory corrosion tests. With a thickness of approximately 3 mm Vh in) and an 8- or Il-mm- (yi6- or Vifi-in-) diameter hole for mounting, these specimens will readily pass through a 45/50 ground-glass joint of a distiUation kettle. The total surface area of a circular specimen is given by the equation ... 

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