Chem. and Min. [f. TRI- + SILICATE.] A compound of one or more basic oxides with silicon dioxide or silica, SiO2: a. in early nomenclature denoting a compound of silicon dioxide with three equivalents of the base (see note s.v. TRI- 5 a); thus trisilicate of iron denoted a compound of three equivalents of iron oxide and one of silicon dioxide, then called silicic acid; b. now used for compounds derived from hypothetical trisilicic acids, formed of three molecules of silicon dioxide (SiO2) with varying numbers of water molecules; e.g., 3 SiO2 . 2 H2O; 3 SiO2 . 5 H2O. c. In Mineralogy, denoting a silicate in which the oxygen in the silicon dioxide bears to the oxygen in the basic oxides the ratio 3 : 1. So Trisilicic a.: see b.

1

1850.  Daubeny, Atom. The. (ed. 2), 112. Trisilicate of iron [denotes] 3 of base to 1 of silicic acid.

2

1868.  Watts, Dict. Chem., V. 243. Silicates are sometimes distinguished by names which express directly the oxygen-ratio in the base and acid … 1 : 3 Trisilicates. Ibid., 251. Bohemian glass-tubing consists of potassio-calcic trisilicate,

        2(K2O . 3 SiO2) 3 (Ca″O . 3 SiO2).

3

1902.  Miers, Mineralogy, 208. Albite, Na2O . Al2O3 . 6 SiO2 or NaAlSi3O8…. According to [its] oxygen ratio, therefore … Albite is a trisilicate.

4

1905.  Newth, Inorg. Chem. (ed. 11), 637. By the partial withdrawal of water from three molecules of silicic acid a number of hypothetical trisilicic acids may be derived…. Felspar, or orthoclase, is a trisilicate, Al2K2(Si3O8)2.

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1911.  Roscoe & Schorlemmer, Treat. Chem. (ed. 4), I. 920. Derivatives of trisilicic acid, H4Si3O8[3Si(OH)4—4 H2O.

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