ISO 995:1975
Withdrawn
A Withdrawn Standard is one, which is removed from sale, and its unique number can no longer be used. The Standard can be withdrawn and not replaced, or it can be withdrawn and replaced by a Standard with a different number.
Potassium hydroxide for industrial use Determination of silica content Reduced molybdosilicate photometric method
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27-02-2019
English, French
01-09-1975
The method is applicable to products having silica contents exceeding 10 mg/kg. The principle is based on the formation of yellow oxidized silico-molybdic complex in a strongly acid medium, in the presence of boric acid to suppress interference by fluorides. Selective reduction of this complex with a mixture of aminonaphtholsulphonic acid (4-amino-3-hydroxynaphthalene-1-sulphonic acid), sodium metabisulphite and sodium sulphite, in the presence of oxalic acid and in a strongly acid medium so as to suppress interference by phosphates. Photometric measurement of the blue-coloured complex at a wavelength of about 795 nm.
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