RE is needed to know exactly what potential the reactions occur. If u don't want, the RE may not necessary. I usually electrically connect the RE with testing solution by an ion bridge.

Usually RE should be in contact with the test electrolyte. If u know the potential where the reaction occurs exactly. Then u can use dummy electrode in place of electrode.

If you have a three-electrode instrument, but want to avoid the use of the reference electrode, then you can use the CE and RE terminals shorted. However, if you leave the RE socked unconnected, then your WE will be poised at the maximum potential, usually leading to a gas evolution due to water electrolysis.

Thank you all for your answers. My question is more about the role of RE inside the test electrolyte. If I place RE such that it is not in contact with the test electrolyte, I get a bogus graph while running CV, but when RE is in contact with the test electrolyte I get the expected graph. But in principle, since RE is used just to maintain a fixed potential, what difference does it make if it is in contact or not with the test electrolyte. I am trying to think of an answer for this. Really appreciate if someone could help me with this.

The further from WE you place it, the more IR drop (solution resistance) there will be and the more the CV will be distorted. A nice explanation is here: https://www.gamry.com/application-notes/understanding-ir-compensation/

https://www.gamry.com/application-notes/understanding-ir-compensation/

Thank you Mila. This is quite helpful. :)

yes it is very necessary for the RE to be in contact with the solution. otherwise there will be connection problem which may even lead to electrolyzation of the working.

for example, when I use modified ITO as WE, platinum or gold as CE and Ag/AgCl as RE, and the RE is by accident removed from the solution, ITO is "burning" - it is reduced to pure tin and indium. be careful with that, cause it can destroy the surface of your WE!

thank you all. I now understand that if the the RE electrode is not touching the test electrolyte, then the IR compensation circuit which is inbuilt in every potentiostat, adds erroneous values to the applied voltage, which causes decomposition/electrolyzation of the WE.

Thank u saranya... for raising a valid question..

Reference electrode is a non-polarizable electrode and therefore variation of potential in between RE and WE doesn't affect the double layer potential difference at RE electrode/electrolyte interface as charges leak through. Hence, potential variation with reference to RE manifests itself at the WE. The current due to REDOX reactions pass between WE and CE and hence RE can maintain the desired PD at the WE. To minimize IR drop the luggin tip of RE should be as close to WE as possible though provision for compensation is there in potentioscans. This is particularly important in case of non-aqueous system where electrolyte resistance is high.

Hi Christian,

I have few doubts based on your answer. You said ''When the reference electrode is removed from the solution, the voltage measurement will result in a random value since the electrode terminal is floating. Due to the high internal resistance of the built-in electrometer situated between working and counter electrode terminals, the measured voltage can assume any value within the measurement range (e.g. +/- 10 V). Whatever the result of the (now erroneous) measurement, the potentiostat will apply as much current as possible to the counter electrode to correct the mismatch between measured and desired voltage. This current may have a positive or negative sign, but in either case will damage at least your working electrode, possibly also the counter electrode.''

When I say I am removing the reference electrode from the test electrolyte, i do not mean that I keep it air. I maintain it at a constant potential in its own salt solution. Now this is not a floating terminal. The high internal resistance between WE and CE would arise if the test electrolyte is less to non conducting, if my test electrolyte is conducting, and I am maintaining a constant potential at the RE by immersing it in its own salt solution, then can I place the RE NOT in contact with the test electrolyte?

I really appreciate you taking time to share your knowledge.

@Saranya. For the completion of the electric circuit you you may have to connect the WE and RE even though they are in separate solution via salt bridge. 

I think the circuit is complete because WE and CE are connected and are in the same solution .

I feel even if you need to measure the potential the whole circuit should be complete it can be ionic or metallic conduction medium. And it is common understand that a single electrode cannot exist and it always measure w.r.to another. If I am wrong please correct me

The whole circuit will be complete, only that the current flows through the WE and CE, and we measure the potential at WE using an RE. We don't want any current to flow through RE and to alter its std potential anyway. 

A single electrode can exist, i.e. open circuit voltage, just that we cannot measure its potential directly and so we take the help of an RE whose potential is known and constant.

Thank you Christian, I did do some small experiments to visualize this and I think I do understand now why the circuit should be complete to do potential measurements too.

Bihag, you were right.

dear all

kindly read  a good book on Electro chemistry

Yes! Bockris and Reddy 2A

i followed a book ectrokinetics - written by Vetter in 1970's (German)

No doubt  tJOMB0ckeris - Reddy book Vol 2 is a Bible -- it came in 1971 to India based on Reddy's class notes @Texas

dear Sarnya

all the three electrodes should be immersed in electrolyte -whether it is galvanostatic or potentio static  modes

Thank you Prof Muralidharan. I did come to realize that. I am trying to get hold of the books you recommended to get a better understanding on electrochemistry.

even you can see the book by Allan J Bard and Faulkner--

for cyclic voltammetery see web-

dear all pl see

dear all see

blessings

[email protected]