ISO 1693:1976
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Cryolite, natural and artificial -- Determination of fluorine content -- Modified Willard-Winter method

This standard was last reviewed and confirmed* in 2015.

*Therefore this version remains current


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.


  • Document published on: 1976-09-01
    Edition: 1 (Monolingual) ICS: 71.060.50
    Status: Published Stage: 90.93 (2015-01-05)
    TC/SC: ISO/TC 226 Number of Pages: 6
  • This standard has not been revised

  • No corrigenda or amendments available

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