Measurement of the pH-value
In practice, the pH value is measured with indicator solutions, indicator paper and measuring electrodes. Indicators (lat. indicare = to indicate) are substances that change their colour in response to certain influencing factors. The colour of pH indicators changes depending on the hydrogen ion concentration. A universal indicator is usually used. In weakly to strongly acidic solutions, it shows a colour from yellow-orange to deep red. Neutral solutions are coloured yellow-green, alkaline solutions show a colour gradation from green to deep blue.
Acidic cleaning agents are not suitable for:
- Limestones (e.g. marble)
- PVC, clinker, fittings, jointing material
- enamelled surfaces
- aluminium, coloured plastic surfaces
Strong alkaline cleaning agents are not suitable for:
- Linoleum, rubber coverings, maintenance films, lacquered surfaces
- Polished limestone
- Aluminium