Princeton,NJ/ 360prwire/ November 22/
In the field of physical science, potentiometric Titration is a considerable principle. In 1893, it was found by Robert Behrend to find the level of concentration of solute in a solution with the help of electrodes potential. That’s why it got the name of Potentiometric Titration, as it undergoes several titrations during the experiment.
Let’s have a detailed discussion about the principle, experiment procedure, types, applications etc., regarding the Potentiometric Titration.
What is Potentiometric Titration?
Potentiometric Titration is a technique used to determine the amount of electromotive force. Here the electrode itself is used as an indicator. It is a chemical analysis with a cell with a reference electrode, salt bridge, and analyte.
- Indicator electrode- Glass electrode or metal ion electrode.
- Reference electrode- Silver chloride electrodes, Hydrogen electrodes, and calomel electrodes.
- Analyte- Electrolyte solution.
These are commonly used solutions for the experiment.
Here, the electromotive force is also known as the potential difference between the rods.
Principle of Potentiometric Titration
The principle of Potentiometric Titration is to determine the potential difference between two electrodes when placed in the sample solution by adding titrations. The addition of titration creates disturbance and increases the concentration of ions.
According to the potentiometric titration principle, the pH value can also be measured in the place of potential difference. So, let’s know about the Potentiometric Titration Formula along with its procedure.
Formula and Experiment
Apparatus: Two electrodes, a stirrer, a beaker, and a burette.
Consider two electrodes as an indicator and a reference electrode. We use a saturated Calomel electrode as a reference electrode to maintain constant potential and remain stable even after dipping in the solution. Another electrode is a glass electrode that acts as an indicator. Salt bridge will look after the prevention of interference between the reference electrode and analyte.
Now take the test solution in a beaker. Through burette, we need to add titrates. After adding a few titrates, we can determine the endpoint with the help of the indicator method. Otherwise, titration curves can be drawn. We can plot a graph between those points and can determine the value of the endpoint. These titration curves are of three types. They are –
- Normal titration curve
- First derivative curve
- Second derivative curve
According to another theory, we have four different types of curves based on their reactions. They are as follows-
- Titration of a strong acid with a strong base.
- Titration of a strong acid with a weak base.
- Titration of a weak acid with a strong base.
- Titration of a weak base with a weak acid.
Now the formula of Potentiometric Titration is-
The electromotive force or the potential difference between electrodes can be calculated by using the following formula –
Ecell = Eind – Eref plus Ej
- Ecell = electromotive force of the complete cell
- Find = electromotive force of the indicator electrode
- Ej = electromotive force at the junction across the salt bridge
- If = electromotive force of the reference electrode
Types of Potentiometric Titration
Potentiometric Titration is a kind of chemical volumetric analysis to find out the potential difference between electrodes. We have four different types of Potentiometric Titrations. They all are explained below.
- Acid-base Titration:
It is a quantitative analysis done with acid and base to calculate the concentration of either acid or base. All this process can be carried out by neutralising the standard solution. The titration of hydrochloric acid ( HCl) with sodium hydroxide ( NaOH) is the best example of this type of titration.
- Redox Titration:
The name itself tells that it is a reaction between oxidation and reduction. Here, we use a Potentiometer or a redox indicator. And the reaction takes place between the titration and a compound. Iodometry, cerimetry, permanganometry, bromatometry, and dichromate are suitable examples. Here we use platinum, and Calomel is electrodes.
- Complexometric Titration:
In this type, we will take a compound sample and membrane electrodes. While determining the concentration of metal ions, a metal indicator complex is formed. The name itself specifies that it is not simple as it consists of four sub- titrations. Namely – direct, indirect, back and replacement titrations.
- Precipitation Titration:
Throughout the entire titration process, we can observe the continuous formation of precipitates. In this titration, the titrate always reacts with solute till the last drop. Then it results in the formation of an insoluble substance. We have different methods for this type of titration like Fagan’s method, Volhard’s method, Mohr’s method etc. So we can determine the electromotive force easily.
These are the four major types of titrations. Besides these four, we have another two. Namely –
Applications of Potentiometric Titration
Based on the principle of Potentiometric Titration, it has several applications. They all are listed below –
- For analysing metals in clinical chemistry, we use the potentiometric Titration principle.
- Potentiometric Titration is also used in environmental analysis.
- Several manufacturing industries may use this principle—Ex:- pharma, food, detergents etc.
- Even in the agricultural department, the Potentiometric Titration is used to detect the soil.
- We can find the equivalence point in acid-base reaction easily only with the support of Potentiometric Titration.
- Potentiometric Titration is also used to analyse ammonia and cyanide in both water and wastewater.
- The concentration of ions is directly proportional to the potential.
- It is an inexpensive method. It doesn’t require much equipment.
- Also, it used a limited quantity of solutions.
These are the various applications possessed by the Potentiometric Titration. As it is easy to use and simple to install, everyone prefers to utilise its benefits.
Hence, it is clear that the Potentiometric Titration is a technique used to determine the value of electromotive force or the potential difference between electrodes. Also, we came to know that it doesn’t require an indicator. The Potentiometric Titration principle is quite simple, understandable and beneficial. Though we discussed its types, method, benefits etc., a single article may not be sufficient to explain Potentiometric Titration. It is very cheap and easy to construct. Another advantage is, the apparatus contains very little equipment. But it has several applications.