Neue Modifikationen des Siliciumdioxids / New Modifications of Silica

Abstract A new family of modifications of silica is obtained by thermal dehydration of crystalline silicic acids with layer structures. Examples are SiO2 · 0.11 H 2 O, SiO 2 · 0.04 H 2 O, SiO 2 prepared by dehydration of H 2 Si 14 O 29 · 5.4 H 2 O, H 2 Si 8 O 17 · xH 2 O and H 2 Si 4 O 9 . The “water content” can amount up to 3 weight percent and results from uncondensed inter-layer silanol groups or from water molecules which are trapped between the layers. In some cases dehydration in the presence of organic interlayer molecules leads to different forms of silica.