Dense silica spheres produced by reacting SiCl sub 4 with water

Submicrometer, equiaxed, spherical silica particles with a low surface area and high density were synthesized by the controlled hydrolysis of SiCl{sub 4} with water. Two approaches were used: low-temperature synthesis in acetonitrile ({minus}20{degree}C, 10 {times} surplus of water) and synthesis in a water-in-hexane emulsion (10{degree}C, stoichiometric amounts of water). The yield of spherical powder synthesized in acetonitrile was 29% and in the water-in-hexane emulsion, 84%.