Ссылочный номер
ISO 4277:1977
© ISO 2025
ISO 4277:1977
Cryolite, natural and artificial — Conventional test for evaluation of free fluorides content
Версия 1
1977-11
В время отменен
Отозвано (Версия 1, 1977)

Тезис

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.

Общая информация

  • Текущий статус
     : Отозвано
    Дата публикации
     : 1977-11
    Этап
    : Отмена международного стандарта [95.99]
  • Версия
     : 1
  • Технический комитет :
    ISO/TC 226
    ICS :
    71.060.50 
  • RSS обновления

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