General methods of test for pigments and extenders — Part 4: Determination of acidity or alkalinity of the aqueous extract
NORMA vydána dne 1.9.1981
Designation standards: ISO 787-4:1981
Publication date standards: 1.9.1981
The number of pages: 2
Approximate weight : 6 g (0.01 lbs)
Country: International technical standard
Kategorie: Technické normy ISO
Description / Abstract: The principle of the method consists in the hot extraction of the material by following the procedure specified in ISO 787/3, to the stage of obtaining a perfectly clear filtrate. The determination is carried out with indicator solution (method A). If the solution with the methyl red indicator is yellow (alkaline), titrate it with the hydrochloric acid solution to an orange end-point; if the solution with the methyl red indicator is red (acid), titrate it with the sodium or potassium hydroxide solution to an orange end-point. The other method (method B) is the potentiometric determination. Take 100 ml of the test solution, insert the electrodes of the pH measuring device and read the pH value.