ISO 787-9:1981 PDF

The water used shall be freshly distilled water, boiled before use, but for 5 to 10 min only, in order to avoid an increase of its pH value due to alkali dissolved from the glass. Preparation of a suspension of the material under test, stopper the container, shaking, allow to stand any time, removing the stopper and determination, to the nearest 0.1 unit, of the pH value of the suspension. - Cancels and replaces ISO Recommendation R 787/9-1970.