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What are the reactions going on in Ag/AgCl reference electrode?
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Natalie Feldman
What are the reactions going on in Ag/AgCl reference electrode?
I have problem obtaining inner filling solution for my electrolyte analyser. The manufacturer only says the inner solution is nacl and kcl. Can I use 3.5molar kcl or 3molar nacl or both?
I have problem obtaining inner filling solution for my electrolyte analyser. The manufacturer only says the inner solution is nacl and kcl. Can I use 3.5molar kcl or 3molar nacl or both?
A variety of filling solutions are used. The most commonly used are saturated KCl or 3.0 M KCl. KCl has the ability to form a crusty layer of solid KCl where the solution is exposed to the air. NaCl (3M ) is preferred and used. LiCl is used in special instances. Advantage Saturated solutions of KCl or NaCl are used because the concentration is reproducible even if the temperature changes (if solid salt is present) and are immune to the effects of water evaporation. Disadvantage However, the solid salts harden into an impenetrable block which may lead to a high impedance electrode. A "nearly saturated" solution (3.5M KCl or 3M NaCl) can change concentration due to evaporation.
A variety of filling solutions are used. The most commonly used are saturated KCl or 3.0 M KCl. KCl has the ability to form a crusty layer of solid KCl where the solution is exposed to the air. NaCl (3M ) is preferred and used. LiCl is used in special instances. Advantage Saturated solutions of KCl or NaCl are used because the concentration is reproducible even if the temperature changes (if solid salt is present) and are immune to the effects of water evaporation. Disadvantage However, the solid salts harden into an impenetrable block which may lead to a high impedance electrode. A "nearly saturated" solution (3.5M KCl or 3M NaCl) can change concentration due to evaporation.
Hi, In addition to the answers above and trying to show you the reactions you asked for, I hope they will be useful: Ag/AgCl is a second type electrode in which the metal is in contact wit its low soluble salt and the anion of that salt. In your case, the metal is Ag in contact with its low soluble salt AgCl + its anion Cl(-) and the reaction is AgCl + e = Ag + Cl(-). This reaction is the half cell of Ag/AgCl ref.electrode. Other reactions which are unwanted, are the complexes formed between AgCl and the high concentration of Cl(-) in satd. KCl. which are: AgCl + Cl(-) = AgCl2(-) and further to AgCl3(2-). These Complexes will cause the dissolution of AgCl and canceling its action as a reference El. That is why few drops of Ag(+) ion is added to the El.half cell to form AgCl Saturated in the solution minimizing that effect. Also, about your question : why Kcl is used and not NaCl? the answer is: You know the electrode has a liquid junction frit to have contact with the solution to close the electrical circuit, this junction causes movement of the ions [Ci(-) and K(+)] in opposite directions through the junction. This movement produces a potential which is unwanted. Now, using Kcl is because the movent of the two mentioned ions, are very close from each other and because they are in an opposite direction they nearly cancel each other. This is not the case if NaCl has been used, because the movements of the two ions are not close to each other. Thank You and Good Luck
Hi, In addition to the answers above and trying to show you the reactions you asked for, I hope they will be useful: Ag/AgCl is a second type electrode in which the metal is in contact wit its low soluble salt and the anion of that salt. In your case, the metal is Ag in contact with its low soluble salt AgCl + its anion Cl(-) and the reaction is AgCl + e = Ag + Cl(-). This reaction is the half cell of Ag/AgCl ref.electrode. Other reactions which are unwanted, are the complexes formed between AgCl and the high concentration of Cl(-) in satd. KCl. which are: AgCl + Cl(-) = AgCl2(-) and further to AgCl3(2-). These Complexes will cause the dissolution of AgCl and canceling its action as a reference El. That is why few drops of Ag(+) ion is added to the El.half cell to form AgCl Saturated in the solution minimizing that effect. Also, about your question : why Kcl is used and not NaCl? the answer is: You know the electrode has a liquid junction frit to have contact with the solution to close the electrical circuit, this junction causes movement of the ions [Ci(-) and K(+)] in opposite directions through the junction. This movement produces a potential which is unwanted. Now, using Kcl is because the movent of the two mentioned ions, are very close from each other and because they are in an opposite direction they nearly cancel each other. This is not the case if NaCl has been used, because the movements of the two ions are not close to each other. Thank You and Good Luck
May I ask what will happen is KCl solution concentration is very low, something like 10mM? I understand the potential of the reference will be difference. but can it still be used as reference? will the potential of the reference electrode still stable?
May I ask what will happen is KCl solution concentration is very low, something like 10mM? I understand the potential of the reference will be difference. but can it still be used as reference? will the potential of the reference electrode still stable?
Naimish P Sardesai , Even I was looking to replace the KCl with NaCl inside the Ag/AgCl, because my electrolyte has NaCl as a supporting electrolyte. But, Can you provide me any relevant references which permits this?
Naimish P Sardesai , Even I was looking to replace the KCl with NaCl inside the Ag/AgCl, because my electrolyte has NaCl as a supporting electrolyte. But, Can you provide me any relevant references which permits this?
Hi, In addition to the answers above and trying to show you the reactions you asked for, I hope they will be useful: Ag/AgCl is a second type electrode in which the metal is in contact wit its low soluble salt and the anion of that salt. In your case, the metal is Ag in contact with its low soluble salt AgCl + its anion Cl(-) and the reaction is AgCl + e = Ag + Cl(-). This reaction is the half cell of Ag/AgCl ref.electrode. Other reactions which are unwanted, are the complexes formed between AgCl and the high concentration of Cl(-) in satd. KCl. which are: AgCl + Cl(-) = AgCl2(-) and further to AgCl3(2-). These Complexes will cause the dissolution of AgCl and canceling its action as a reference El. That is why few drops of Ag(+) ion is added to the El.half cell to form AgCl Saturated in the solution minimizing that effect. Also, about your question : why Kcl is used and not NaCl? the answer is: You know the electrode has a liquid junction frit to have contact with the solution to close the electrical circuit, this junction causes movement of the ions [Ci(-) and K(+)] in opposite directions through the junction. This movement produces a potential which is unwanted. Now, using Kcl is because the movent of the two mentioned ions, are very close from each other and because they are in an opposite direction they nearly cancel each other. This is not the case if NaCl has been used, because the movements of the two ions are not close to each other. Thank You and Good Luck
Hi, In addition to the answers above and trying to show you the reactions you asked for, I hope they will be useful: Ag/AgCl is a second type electrode in which the metal is in contact wit its low soluble salt and the anion of that salt. In your case, the metal is Ag in contact with its low soluble salt AgCl + its anion Cl(-) and the reaction is AgCl + e = Ag + Cl(-). This reaction is the half cell of Ag/AgCl ref.electrode. Other reactions which are unwanted, are the complexes formed between AgCl and the high concentration of Cl(-) in satd. KCl. which are: AgCl + Cl(-) = AgCl2(-) and further to AgCl3(2-). These Complexes will cause the dissolution of AgCl and canceling its action as a reference El. That is why few drops of Ag(+) ion is added to the El.half cell to form AgCl Saturated in the solution minimizing that effect. Also, about your question : why Kcl is used and not NaCl? the answer is: You know the electrode has a liquid junction frit to have contact with the solution to close the electrical circuit, this junction causes movement of the ions [Ci(-) and K(+)] in opposite directions through the junction. This movement produces a potential which is unwanted. Now, using Kcl is because the movent of the two mentioned ions, are very close from each other and because they are in an opposite direction they nearly cancel each other. This is not the case if NaCl has been used, because the movements of the two ions are not close to each other. Thank You and Good Luck
Dear Mr. Abrar, completing the answer of Dr. Najib, the Ag/AgCl is immersed in a high concentration of chloride ions to maintain the measured potential independent of the chloride ions concentration present in the sample. If you just use a wire of silver covered with silver chloride, the reference electrode also responds to chloride ions. Therefore, this affect the measurements of the indicator electrode. Generally, is used a concentration from 1 to 3 M, because these are about ten times higher than chloride ions concentration in the sample. But, other anions can also affect the potential of reference electrode. The subject is very interesting and complex. See the best review about new developments of reference electrodes: U. Guth, F. Gerlach, M. Decker, W. Oelßner, W. Vonau; Solid-state reference electrodes for potentiometric sensors. Journal of Solid State Electrochemistry. January 2009, Volume 13, Issue 1, pp 27-39. I think this paper can help you in your doubts. Kind regards.
Dear Mr. Abrar, completing the answer of Dr. Najib, the Ag/AgCl is immersed in a high concentration of chloride ions to maintain the measured potential independent of the chloride ions concentration present in the sample. If you just use a wire of silver covered with silver chloride, the reference electrode also responds to chloride ions. Therefore, this affect the measurements of the indicator electrode. Generally, is used a concentration from 1 to 3 M, because these are about ten times higher than chloride ions concentration in the sample. But, other anions can also affect the potential of reference electrode. The subject is very interesting and complex. See the best review about new developments of reference electrodes: U. Guth, F. Gerlach, M. Decker, W. Oelßner, W. Vonau; Solid-state reference electrodes for potentiometric sensors. Journal of Solid State Electrochemistry. January 2009, Volume 13, Issue 1, pp 27-39. I think this paper can help you in your doubts. Kind regards.
Dear Mr. Abrar, completing the answer of Dr. Najib, the Ag/AgCl is immersed in a high concentration of chloride ions to maintain the measured potential independent of the chloride ions concentration present in the sample. If you just use a wire of silver covered with silver chloride, the reference electrode also responds to chloride ions. Therefore, this affect the measurements of the indicator electrode. Generally, is used a concentration from 1 to 3 M, because these are about ten times higher than chloride ions concentration in the sample. But, other anions can also affect the potential of reference electrode. The subject is very interesting and complex. See the best review about new developments of reference electrodes: U. Guth, F. Gerlach, M. Decker, W. Oelßner, W. Vonau; Solid-state reference electrodes for potentiometric sensors. Journal of Solid State Electrochemistry. January 2009, Volume 13, Issue 1, pp 27-39. I think this paper can help you in your doubts. Kind regards.
Dear Mr. Abrar, completing the answer of Dr. Najib, the Ag/AgCl is immersed in a high concentration of chloride ions to maintain the measured potential independent of the chloride ions concentration present in the sample. If you just use a wire of silver covered with silver chloride, the reference electrode also responds to chloride ions. Therefore, this affect the measurements of the indicator electrode. Generally, is used a concentration from 1 to 3 M, because these are about ten times higher than chloride ions concentration in the sample. But, other anions can also affect the potential of reference electrode. The subject is very interesting and complex. See the best review about new developments of reference electrodes: U. Guth, F. Gerlach, M. Decker, W. Oelßner, W. Vonau; Solid-state reference electrodes for potentiometric sensors. Journal of Solid State Electrochemistry. January 2009, Volume 13, Issue 1, pp 27-39. I think this paper can help you in your doubts. Kind regards.
The mobility difference of K+ and Cl- in KCl is the least among chlorides, which creates smaller liquid junction potential and a minor correction to the standard potential.Therefore, 3.5 M KCl is recommended.
The mobility difference of K+ and Cl- in KCl is the least among chlorides, which creates smaller liquid junction potential and a minor correction to the standard potential.Therefore, 3.5 M KCl is recommended.
I have problem obtaining inner filling solution for my electrolyte analyser.
The manufacturer only says the inner solution is nacl and kcl.
Can I use 3.5molar kcl or 3molar nacl or both?
I have problem obtaining inner filling solution for my electrolyte analyser.
The manufacturer only says the inner solution is nacl and kcl.
Can I use 3.5molar kcl or 3molar nacl or both?
More
VOTE
A variety of filling solutions are used. The most commonly used are saturated KCl or 3.0 M KCl. KCl has the ability to form a crusty layer of solid KCl where the solution is exposed to the air. NaCl (3M ) is preferred and used. LiCl is used in special instances.
Advantage
Saturated solutions of KCl or NaCl are used because the concentration is reproducible even if the temperature changes (if solid salt is present) and are immune to the effects of water evaporation.
Disadvantage
However, the solid salts harden into an impenetrable block which may lead to a high impedance electrode. A "nearly saturated" solution (3.5M KCl or 3M NaCl) can change concentration due to evaporation.
A variety of filling solutions are used. The most commonly used are saturated KCl or 3.0 M KCl. KCl has the ability to form a crusty layer of solid KCl where the solution is exposed to the air. NaCl (3M ) is preferred and used. LiCl is used in special instances.
Advantage
Saturated solutions of KCl or NaCl are used because the concentration is reproducible even if the temperature changes (if solid salt is present) and are immune to the effects of water evaporation.
Disadvantage
However, the solid salts harden into an impenetrable block which may lead to a high impedance electrode. A "nearly saturated" solution (3.5M KCl or 3M NaCl) can change concentration due to evaporation.
More
VOTE
Hi,
In addition to the answers above and trying to show you the reactions you asked for, I hope they will be useful:
Ag/AgCl is a second type electrode in which the metal is in contact wit its low soluble salt and the anion of that salt. In your case, the metal is Ag in contact with its low soluble salt AgCl + its anion Cl(-) and the reaction is AgCl + e = Ag + Cl(-). This reaction is the half cell of Ag/AgCl ref.electrode. Other reactions which are unwanted, are the complexes formed between AgCl and the high concentration of Cl(-) in satd. KCl. which are: AgCl + Cl(-) = AgCl2(-) and further to AgCl3(2-). These Complexes will cause the dissolution of AgCl and canceling its action as a reference El. That is why few drops of Ag(+) ion is added to the El.half cell to form AgCl Saturated in the solution minimizing that effect.
Also, about your question : why Kcl is used and not NaCl? the answer is:
You know the electrode has a liquid junction frit to have contact with the solution to close the electrical circuit, this junction causes movement of the ions [Ci(-) and K(+)] in opposite directions through the junction. This movement produces a potential which is unwanted. Now, using Kcl is because the movent of the two mentioned ions, are very close from each other and because they are in an opposite direction they nearly cancel each other. This is not the case if NaCl has been used, because the movements of the two ions are not close to each other.
Thank You and Good Luck
Hi,
In addition to the answers above and trying to show you the reactions you asked for, I hope they will be useful:
Ag/AgCl is a second type electrode in which the metal is in contact wit its low soluble salt and the anion of that salt. In your case, the metal is Ag in contact with its low soluble salt AgCl + its anion Cl(-) and the reaction is AgCl + e = Ag + Cl(-). This reaction is the half cell of Ag/AgCl ref.electrode. Other reactions which are unwanted, are the complexes formed between AgCl and the high concentration of Cl(-) in satd. KCl. which are: AgCl + Cl(-) = AgCl2(-) and further to AgCl3(2-). These Complexes will cause the dissolution of AgCl and canceling its action as a reference El. That is why few drops of Ag(+) ion is added to the El.half cell to form AgCl Saturated in the solution minimizing that effect.
Also, about your question : why Kcl is used and not NaCl? the answer is:
You know the electrode has a liquid junction frit to have contact with the solution to close the electrical circuit, this junction causes movement of the ions [Ci(-) and K(+)] in opposite directions through the junction. This movement produces a potential which is unwanted. Now, using Kcl is because the movent of the two mentioned ions, are very close from each other and because they are in an opposite direction they nearly cancel each other. This is not the case if NaCl has been used, because the movements of the two ions are not close to each other.
Thank You and Good Luck
More
VOTE
May I ask what will happen is KCl solution concentration is very low, something like 10mM?
I understand the potential of the reference will be difference.
but can it still be used as reference?
will the potential of the reference electrode still stable?
May I ask what will happen is KCl solution concentration is very low, something like 10mM?
I understand the potential of the reference will be difference.
but can it still be used as reference?
will the potential of the reference electrode still stable?
More
VOTE
Naimish P Sardesai , Even I was looking to replace the KCl with NaCl inside the Ag/AgCl, because my electrolyte has NaCl as a supporting electrolyte. But, Can you provide me any relevant references which permits this?
Thanks a lot.
Regards,
Khantesh
Naimish P Sardesai , Even I was looking to replace the KCl with NaCl inside the Ag/AgCl, because my electrolyte has NaCl as a supporting electrolyte. But, Can you provide me any relevant references which permits this?
Thanks a lot.
Regards,
Khantesh
More
VOTE
Hi,
In addition to the answers above and trying to show you the reactions you asked for, I hope they will be useful:
Ag/AgCl is a second type electrode in which the metal is in contact wit its low soluble salt and the anion of that salt. In your case, the metal is Ag in contact with its low soluble salt AgCl + its anion Cl(-) and the reaction is AgCl + e = Ag + Cl(-). This reaction is the half cell of Ag/AgCl ref.electrode. Other reactions which are unwanted, are the complexes formed between AgCl and the high concentration of Cl(-) in satd. KCl. which are: AgCl + Cl(-) = AgCl2(-) and further to AgCl3(2-). These Complexes will cause the dissolution of AgCl and canceling its action as a reference El. That is why few drops of Ag(+) ion is added to the El.half cell to form AgCl Saturated in the solution minimizing that effect.
Also, about your question : why Kcl is used and not NaCl? the answer is:
You know the electrode has a liquid junction frit to have contact with the solution to close the electrical circuit, this junction causes movement of the ions [Ci(-) and K(+)] in opposite directions through the junction. This movement produces a potential which is unwanted. Now, using Kcl is because the movent of the two mentioned ions, are very close from each other and because they are in an opposite direction they nearly cancel each other. This is not the case if NaCl has been used, because the movements of the two ions are not close to each other.
Thank You and Good Luck
Hi,
In addition to the answers above and trying to show you the reactions you asked for, I hope they will be useful:
Ag/AgCl is a second type electrode in which the metal is in contact wit its low soluble salt and the anion of that salt. In your case, the metal is Ag in contact with its low soluble salt AgCl + its anion Cl(-) and the reaction is AgCl + e = Ag + Cl(-). This reaction is the half cell of Ag/AgCl ref.electrode. Other reactions which are unwanted, are the complexes formed between AgCl and the high concentration of Cl(-) in satd. KCl. which are: AgCl + Cl(-) = AgCl2(-) and further to AgCl3(2-). These Complexes will cause the dissolution of AgCl and canceling its action as a reference El. That is why few drops of Ag(+) ion is added to the El.half cell to form AgCl Saturated in the solution minimizing that effect.
Also, about your question : why Kcl is used and not NaCl? the answer is:
You know the electrode has a liquid junction frit to have contact with the solution to close the electrical circuit, this junction causes movement of the ions [Ci(-) and K(+)] in opposite directions through the junction. This movement produces a potential which is unwanted. Now, using Kcl is because the movent of the two mentioned ions, are very close from each other and because they are in an opposite direction they nearly cancel each other. This is not the case if NaCl has been used, because the movements of the two ions are not close to each other.
Thank You and Good Luck
More
VOTE
Dear Mr. Abrar, completing the answer of Dr. Najib, the Ag/AgCl is immersed in a high concentration of chloride ions to maintain the measured potential independent of the chloride ions concentration present in the sample. If you just use a wire of silver covered with silver chloride, the reference electrode also responds to chloride ions. Therefore, this affect the measurements of the indicator electrode. Generally, is used a concentration from 1 to 3 M, because these are about ten times higher than chloride ions concentration in the sample. But, other anions can also affect the potential of reference electrode. The subject is very interesting and complex. See the best review about new developments of reference electrodes: U. Guth, F. Gerlach, M. Decker, W. Oelßner, W. Vonau; Solid-state reference electrodes for potentiometric sensors. Journal of Solid State Electrochemistry. January 2009, Volume 13, Issue 1, pp 27-39. I think this paper can help you in your doubts. Kind regards.
Dear Mr. Abrar, completing the answer of Dr. Najib, the Ag/AgCl is immersed in a high concentration of chloride ions to maintain the measured potential independent of the chloride ions concentration present in the sample. If you just use a wire of silver covered with silver chloride, the reference electrode also responds to chloride ions. Therefore, this affect the measurements of the indicator electrode. Generally, is used a concentration from 1 to 3 M, because these are about ten times higher than chloride ions concentration in the sample. But, other anions can also affect the potential of reference electrode. The subject is very interesting and complex. See the best review about new developments of reference electrodes: U. Guth, F. Gerlach, M. Decker, W. Oelßner, W. Vonau; Solid-state reference electrodes for potentiometric sensors. Journal of Solid State Electrochemistry. January 2009, Volume 13, Issue 1, pp 27-39. I think this paper can help you in your doubts. Kind regards.
More
VOTE
Dear Mr. Abrar, completing the answer of Dr. Najib, the Ag/AgCl is immersed in a high concentration of chloride ions to maintain the measured potential independent of the chloride ions concentration present in the sample. If you just use a wire of silver covered with silver chloride, the reference electrode also responds to chloride ions. Therefore, this affect the measurements of the indicator electrode. Generally, is used a concentration from 1 to 3 M, because these are about ten times higher than chloride ions concentration in the sample. But, other anions can also affect the potential of reference electrode. The subject is very interesting and complex. See the best review about new developments of reference electrodes: U. Guth, F. Gerlach, M. Decker, W. Oelßner, W. Vonau; Solid-state reference electrodes for potentiometric sensors. Journal of Solid State Electrochemistry. January 2009, Volume 13, Issue 1, pp 27-39. I think this paper can help you in your doubts. Kind regards.
Dear Mr. Abrar, completing the answer of Dr. Najib, the Ag/AgCl is immersed in a high concentration of chloride ions to maintain the measured potential independent of the chloride ions concentration present in the sample. If you just use a wire of silver covered with silver chloride, the reference electrode also responds to chloride ions. Therefore, this affect the measurements of the indicator electrode. Generally, is used a concentration from 1 to 3 M, because these are about ten times higher than chloride ions concentration in the sample. But, other anions can also affect the potential of reference electrode. The subject is very interesting and complex. See the best review about new developments of reference electrodes: U. Guth, F. Gerlach, M. Decker, W. Oelßner, W. Vonau; Solid-state reference electrodes for potentiometric sensors. Journal of Solid State Electrochemistry. January 2009, Volume 13, Issue 1, pp 27-39. I think this paper can help you in your doubts. Kind regards.
More
VOTE
The mobility difference of K+ and Cl- in KCl is the least among chlorides, which creates smaller liquid junction potential and a minor correction to the standard potential.Therefore, 3.5 M KCl is recommended.
The mobility difference of K+ and Cl- in KCl is the least among chlorides, which creates smaller liquid junction potential and a minor correction to the standard potential.Therefore, 3.5 M KCl is recommended.
More
VOTE