Definition: The pH-value indicates whether an aqueous solution has an acidic or alkaline character. It refers to the activity of hydrogen ions and is a physical variable that is given as a pure and dimensionless number. Some chemical compounds change their structure depending on the pH-value, which can affect their color. The pH-value of materials also affects humans and nature, e.g. with respect to the ground and drinking water. The acidic or alkaline character of a medium also affects the selection of materials for the parts inside the pump that are in contact with the medium. For this reason, it is important to know the value to determine the suitable materials.

The pH-value provides information about the acidic or alkaline character of an aqueous solution.