ISO 4277:1977
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ISO 4277:1977
10117

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 

  •  :  Withdrawn
     : 1977-11
  •  : 1
     : 3
  •  : ISO/TC 226 Materials for the production of primary aluminium
  •  :
    71.060.50 Salts

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