Reference number
ISO 4277:1977
© ISO 2024
ISO 4277:1977
Cryolite, natural and artificial — Conventional test for evaluation of free fluorides content
Edition 1
1977-11
Withdrawn
Withdrawn (Edition 1, 1977)

Abstract

Applicable to products having contents of AlF3 of more than 0.15 % (m/m) or of NaF of more than 0.4 % (m/m). Covers sintering of a test portion with a known quantity of sodium fluoride in a muffle furnace at a temperature of (790 10) °C. Under these conditions, aluminium fluoride in excess of that required by the stoichiometric formula AlF3 .3NaF reacts to form cryolite; extraction of the ground sintered mass with boiling water. Acidification with hydrochloric acid solution to a pH less than 3.7 and titration of the excess sodium fluoride with thorium nitrate solution in the presence of alizarin-S as indicator. Has also been approved by the IUPAC.

General information

  • Status
     : Withdrawn
    Publication date
     : 1977-11
    Stage
    : Withdrawal of International Standard [95.99]
  • Edition
     : 1
    Number of pages
     : 3
  • Technical Committee :
    ISO/TC 226
    ICS :
    71.060.50 
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