<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (July 2018) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (July 2018) (Learn how and when to remove this template message) </Td> </Tr> <P> A glass electrode is a type of ion - selective electrode made of a doped glass membrane that is sensitive to a specific ion . The most common application of ion - selective glass electrodes is for the measurement of pH . The pH electrode is an example of a glass electrode that is sensitive to hydrogen ions . Glass electrodes play an important part in the instrumentation for chemical analysis and physico - chemical studies . The voltage of the glass electrode, relative to some reference value, is sensitive to changes in the activity of certain type of ions . </P> <P> The first studies of glass electrodes (GE) found different sensitivities of different glasses to change of the medium's acidity (pH), due to effects of the alkali metal ions . </P>

What part of the ph probe is sensitive to hydrogen ion concentration