ISO 804:1976, Aluminium oxide primarily used for the production of aluminium -- Preparation of solution for analysis -- Method by alkaline fusion

The procedure for the preparation of a principal solution for chemical analysis requires at first an alkaline fusion of the test portion, either with a mixture of sodium carbonate and boric acid or with a mixture of sodium carbonate and sodium tetraborate. Subsequent dissolution of the molten mass in an excess of nitric acid and adjustment of an appropriate aliquot portion to pH 2. Replaces ISO Recommendation R804/1968.