ISO 4281:1977
Subscribe to updates

Sodium hexafluorosilicate for industrial use -- Determination of free acidity and total hexafluorosilicate content -- Titrimetric method

This standard was last reviewed* in 2011.

*ISO standards are reviewed every five years.


With respect to the free acidity, applicable to products having contents, expressed as H2 SiF6 , equal to or more than 0,1 % (m/m). First, determination of the free acid contents by titration of an ice-cooled test portion with a standard volumetric sodium hydroxide solution in the presence of potassium nitrate and using bromothymol blue as indicator, then, followed by titration at near boiling temperature with standard volumetric sodium hydroxide solution to the appearance of a permanent blue colour.


  • Document published on: 1977-03-01
    Edition: 1 (Monolingual) ICS: 71.060.50
    Status: Published Stage: 90.93 (2011-10-13)
    TC/SC: ISO/TC 47 Number of Pages: 2
  • 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).