sodium silicate

: any of various water-soluble substances obtained in the form of crystals, glasses, powders, or aqueous solutions usually by melting silica with a sodium compound (such as sodium carbonate or sodium hydroxide): such as

a or sodium orthosilicate : a corrosive crystalline substance regarded as a salt Na₄SiO₄ or 2Na₂O.SiO₂ of orthosilicic acid or as a mixture of sodium metasilicate with sodium hydroxide and used chiefly in heavy-duty cleaning compositions

b or sodium metasilicate : a crystalline salt Na₂SiO₃ or Na₂O.SiO₂ either in the anhydrous or hydrated form used chiefly as a detergent

c or sodium sesquisilicate : a corrosive crystalline salt regarded as intermediate in composition between sodium orthosilicate and sodium metasilicate and used in heavy-duty cleaning compositions —not used systematically

d : water glass