ISO 995:1975
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ISO 995:1975
5439

Abstract 

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.


General information 

  •  :  Withdrawn
     : 1975-09
  •  : 1
     : 3
  •  : ISO/TC 47 Chemistry
  •  :
    71.060.40 Bases

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