ISO 2124:1972
Withdrawn
A Withdrawn Standard is one, which is removed from sale, and its unique number can no longer be used. The Standard can be withdrawn and not replaced, or it can be withdrawn and replaced by a Standard with a different number.
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05-10-2019
English, French
06-01-1972
The principle consists in neutralization of the alkalinity of a test portion, previously dissolved, in presence of methyl red as indicator. Addition of sodium fluoride, which reacts with the silicic acid, forming a euaivalent quantity of sodium hydroxide. Addition of a measured volume of standard volumetric hydrochloric acid solution in excess, followed for diluting by ethanol. Filtration of the silicic compound thus obtained, which is insoluble under these conditions. Titration of the excess of hydrochloric acid in the filtrate with standard volumetric sodium hydroxide solution in presence of methyl red as indicator.
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