| http://www.w3.org/ns/prov#value | - More specifically, in a preferred embodiment of the present invention white monochromal spheres prepared in the first step, are suspended in water and thereto is (i) added an oxidizing agent such as cerium ammonium nitrate or chromic acid, in an amount of from about 0.05 to about 0.1 percent by weight of the monochromal sphere, followed by stirring for an effective period, for example from about 1
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