ISO 2833:1973
Subscribe to updates

Sodium fluoride for industrial use -- Determination of fluorine content -- Modified Willard-Winter method

This standard was last reviewed* in 2011.

*ISO standards are reviewed every five years.


The principle consists in separation of the fluorine from a test portion by distillation with sulphuric acid or perchloric acid. Titration with thorium nitrate solution using sodium alizarinsuphonate and methylene blue as indicators. Alternatively the thorium nitrate titration may be carried out using sodium alizarinsuphonate alone as indicator, the end-point being determined spectrophotometrically under carefully defined conditions. The absorbance at a wavelength of 525 nm shall reach the arbitrary value of 0.6. Has also been approved by the IUPAC.


  • Document published on: 1973-12-01
    Edition: 1 (Monolingual) ICS: 71.060.50
    Status: Published Stage: 90.93 (2011-10-13)
    TC/SC: ISO/TC 47 Number of Pages: 5
  • No revision information available

  • No corrigenda or amendments available

Related standards

  • PDF

    This format preserves the paper layout, and is watermarked

  • EPUB

    This format allows documents to be read on tablets and smartphones


    Enhanced user-friendly colour PDF format


    See any updates made from previous versions at a glance


    Normally A4 size documents. Shipping costs apply


Swiss francs CHF 38

Add to basket

Got a question?

Check out our FAQs

Email customer services
or call us on +41 22 749 08 88
09:00 – 12:30, 14:00 – 17:00 (UTC+1).