ISO 10349-7:1992

Photography — Photographic-grade chemicals — Test methods — Part 7: Determination of alkalinity or acidity

The method is based on weighing the test portion, dissolution in carbon-dioxide-free water, adding phenolphthalein indicator, and observing the colour of the test solution: if the test solution turns pink, determination of the alkalinity, if it remains colourless, determination of the acidity.