Reference number
ISO 1690:1976
ISO 1690:1976
© ISO 2024
International Standard
ISO 1690:1976
Sodium and potassium silicates for industrial use — Determination of silica content — Gravimetric method by insolubilization
Edition 1
1976-02
1976-02
ISO 1690:1976
6306
Published
(Edition 1, 1976)
This publication was last reviewed and confirmed in 2023.
Therefore this version remains current.
Abstract
The procedure is based on evaporation to dryness of a test portion previously acidified with hydrochloric acid. Dissolution of the soluble salts, filtration and washing of the insoluble matter. Second evaporation of the filtrate and washings under the same conditions, further dissolution of the soluble salts, filtration and washing. Calcination and weighing of the two lots of insoluble matter simultaneously. Volatilization of silica by heating with hydrofluoric and sulphuric acids and weighing of the residue after calcination. The*difference in mass represents the silica present in the test portion.