Reference number
ISO 1691:1976
ISO 1691:1976
© ISO 2025
International Standard
ISO 1691:1976
Sodium and potassium silicates for industrial use — Determination of carbonates content — Gas-volumetric method
Edition 1
1976-07
1976-07
ISO 1691:1976
6307
Published
(Edition 1, 1976)
This publication was last reviewed and confirmed in 2023.
Therefore this version remains current.
Abstract
Three cases, defined by a preliminary test, are envisaged: silicates containing neither sulphides nor chlorates; silicates containing sulphides; silicates containing chlorates. The method based on boiling of an acidified test portion containing methyl orange and with a lead paper strip in the vapour. The presence of sulphides produces blackening of the paper and the presence of chlorates decolorizes the methyl orange. Volumetric*measurement of carbon dioxide evolved from silicates containing neither sulphides nor chlorates by reaction with a hydrochloric acid solution. The principle for the oxidation of sulphides and the reduction of chlorates are specified.