ISO 1620:1976

Cryolite, natural and artificial — Determination of silica content — Reduced molybdosilicate spectrophotometric method

Publication date:   Sep 1, 1976

General information

90.93 Standard confirmed   Nov 15, 2022


ISO/TC 226 Materials for the production of primary aluminium

International Standard

71.060.50   Salts



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Specifies methods of test for natural and synthetic materials having a molar ratio sodium fluoride/aluminium trifluoride between 3 and 1,7 approximately. The method is applicable to products the phosphorus pentoxide content of which does not exceed 0,02 % (m/m). The procedure consists in alkaline fusion of a test portion by means of a mixture of sodium carbonate and boric acid. Dissolution of the fused mass in excess nitric acid so that the pH value is between 0,7 and 0,9. Formation of the (Yellow) oxidized molybdosilicate under clearly defined conditions of acidity, temperature, time and concentration of reagents. Selective reduction in the presence of tartaric acid and measurement at a wvelength of about 815 nm.

Life cycle


ISO 1620:1976
90.93 Standard confirmed
Nov 15, 2022