| http://www.w3.org/ns/prov#value | - A preferred group of the above water-insoluble siliceous fibers are exceptionally porous, having a surface area of at least about 500 m2 /g, a pore volume of about 0.2 to about 0.75 cc/g, an average pore diameter of about 10 to about 100 A, and an essential chemical composition corresponding to the above formula in which x is a fractional or whole number from about 0.5 to about 6.
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