Range of A PH Glass Electrode
The pH range at constant concentration can be divided into 3 parts:
- Complete realization of general electrode function, where dependence of potential on pH has linear behavior and within which such electrode really works as ion-selective electrode for pH.
where F is Faraday's constant.
- Alkali error range - at low concentration of hydrogen ions (high values of pH) contributions of interfering alkali metals (like Li, Na, K) are comparable with the one of hydrogen ions. In this situation dependence of the potential on pH become non-linear.
The effect is usually noticeable at pH > 12, and concentrations of lithium or sodium ions of 0.1 moles per litre or more. Potassium ions usually cause less error than sodium ions.
- Acidic error range – at very high concentration of hydrogen ions (low values of pH) the dependence of the electrode on pH becomes non-linear and the influence of the anions in the solution also becomes noticeable. These effects usually become noticeable at pH < -1.
There are different types of pH glass electrode, some of them have improved characteristics for working in alkaline or acidic media. But almost all electrodes have sufficient properties for working in the most popular pH range from pH = 2 to pH = 12. Special electrodes should be used only for working in aggressive conditions.
Most of text written above is also correct for any ion-exchange electrodes.
Read more about this topic: Glass Electrode
Famous quotes containing the words range of, range and/or glass:
“A girl must allow others to share the responsibility for care, thus enabling others to care for her. She must learn how to care in ways appropriate to her age, her desires, and her needs; she then acts with authenticity. She must be allowed the freedom not to care; she then has access to a wide range of feelings and is able to care more fully.”
—Jeanne Elium (20th century)
“The more the specific feelings of being under obligation range themselves under a supreme principle of human dependence the clearer and more fertile will be the realization of the concept, indispensable to all true culture, of service; from the service of God down to the simple social relationship as between employer and employee.”
—Johan Huizinga (1872–1945)
“When God at first made man,
Having a glass of blessings standing by,
“Let us,” said He, “pour on him all we can:
Let the world’s riches, which dispersed lie,
Contract into a span.””
—George Herbert (1593–1633)