It is an ionic compound consisting of sodium cations Na+ and the polymeric metasilicate anions [–SiO2−3–]n. It is a colorless crystalline hygroscopic and deliquescent solid, soluble in water (giving an alkaline solution) but not in alcohols.

[1] The anhydrous compound can be prepared by fusing silicon dioxide SiO2 (silica, quartz) with sodium oxide Na2O in 1:1 molar ratio.

[2] The compound crystallizes from solution as various hydrates, such as In the anhydrous solid, the metasilicate anion is actually polymeric, consisting of corner-shared {SiO4} tetrahedra, and not a discrete SiO32− ion.

[5] The pentahydrate and nonahydrate forms have their own CAS Numbers, 10213-79-3 and 13517-24-3 respectively.

Sodium Metasilicate reacts with acids to produce silica gel.