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ISO 1693:1976

Cryolite, natural and artificial -- Determination of fluorine content -- Modified Willard-Winter method

This standard has been reviewed and then confirmed in 2009 
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Specifies the determination for natural and synthetic materials having a molar ratio sodium fluoride/aluminium trifluoride between 3 and 1,7 approximately. The principle consists in fusion of a test portion with sodium carbonate, separation of fluorine by distillation with sulphuric acid or perchloric acid. Titration with thorium nitrate solution in presence of sodium alizarinsulphonate/methylene blue as indicator. Alternatively, the thorium nitrate titration may be made using only sodium alizarinsulphonate, the end-point being*spectrophotometrically determined at 525 nm.


  • Edition: 1 (Monolingual) ICS: 71.060.50
    Status: Published Stage: 90.93 (2009-09-17)
    TC/SC: ISO/TC 226 Number of Pages: 6
  • No revision information available

  • No corrigenda or amendments available

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