kept your reference electrode into sat. KCl solution (half deep).

it better to use Double Junction Ag/AgCl Reference Electrode. it is quit stable, no need to change the solution every time. you can kept in box also.

see the below file for electrode form Pine instrument, USA

Hello,

As Bapi Bera stated above, keep it in a KCl solution. In addition, it is always good to use a known internal reference and check your CV's periodically. In aqueous conditions, a standard known reference is potassium ferricyanide. It is best to reference against an internal standard if reporting very specific values. Don't use the reference during long-timescale experiments such as electrolysis.

Sincerely,

Dr. Grice

From the issues you are having with this reference electrode (RE) and especially the 'contamination' that comes with changing the internal electrolyte, I would suggest you discontinue using this particular RE if possible since it's possible that proper storage from henceforth may not restore its quality.

You can fabricate new Ag/AgCl REs just by anodizing a silver wire in KCl, placing it in a thin glass pipete. Seal the tip with Agar and fill it with KCl solution. Look for youtube videos on this. It's a very simple process. Then you can think of calibration and proper storage. See section 4 (especially pages 26, 27) of the pdf in the link below.

http://www.basinc.com/mans/epc.pdf

Dear Ingy,

if you are sure that the wire inside the electrode is indeed silver, and you are filling the electrode with reasonably pure KCl solution, then you need to answer the question: what is that black deposit on the wire?

Please check the color of all possible silver salts / oxides, then ask yourself: how is this possible that I am making this salt/oxide on my reference electrode wire? Possibly the connections to your potentiostat are mixed up. Maybe the potentiostat itself is broken.

If this black color appears immediately when you fill your RE with KCl solution - this is either not silver, or not KCl (or both).

In any case, it is a good idea to check if there is any significant current flowing through your RE (this should never be the case), and at which potential your RE is with respect to your CE. A multimeter connected between the RE and CE will tell. If this voltage is very high (over one volt) - your potentiostat is not working properly, or there is a problem with your CE. Also check the voltage between WE and CE - if this one is very high, the capillary at the bottom of your RE may be blocked. Placing it in a beaker with hot ultrapure DI water usually unblocks it.

Always rinse your RE after use with pure water, then store in a beaker with aqueous KCl solution of the same molarity as you use inside the RE.

Dear Ingy, a possible problem may came from the composition of your working solution. Typically when your electrolyte solution contains perchloric acid, or perchlorate ions, you needs to change the reference electrolyte from KCl to NaCl. That is because solid KClO4 is formed inside the reference junction, increasing the electrical resistance of the junction and originating malfunctioning of the reference electrode.

Of course I should use also a double junction electrode.

Could you tell us the composition of your electrolyte solution?

thank you all for your kind reply

Could anyone recommend an optimal molarity of KCl to prepared for Ag/AgCl R.E?? What is the molarity to be maintained inside the tube.Also, we will be keeping the R.E in separate KCL solution. What should be optimal molarity difference should be maintained.

1M or 3M or same 1M in tube and 1M outside.

we usually use 1 M concentration of KCl. I would recommend to use internal reference electrode.