I think you should improve your explanation a bit. First, was your filling solution saturated with Ag+ as well? Did you empty the previous solution before filling the electrode? Can you read your pH standards in millivolts and make a calibration curve outside your instrument?

I emptied the electrode before filling it with a fresh solution which is saturated with kcl 3,5M only, I don't have the commercial one which is saturated with agcl+kcl.

For the curve calibration, Can you explain to me how to do it Outside my instrument?

Thanks

Hi, Amel

You can prepare your KCl solution and just add one drop of AgNO3 solution and stir the mix. You will have an instant formation of AgCl precipitation. You can wait for the precipitation to settle and collect the supernatant. Or you can filter the solution. In both cases, the solution is then a KCl solution saturated with Ag+. You shouldn't use KCl without Ag+ saturation inside your electrode.

The Calibration Curve: Your instrument must have an option to read the measurements in millivolts. Thus you can write down the numbers for each standard and table them (pH x millivolts). You should plot pH in (x) and millivolts in (y) using - for example - an Excel spreadsheet that can show the plot and also use linear regression to calculate the best equation for your calibration curve and the correspondent correlation coefficient as well as the coefficient of determination.

I prepared a video explaining the whole process, which I make available to my students every semester. Unfortunately, it is in Portuguese. After your doubts, I am thinking that I should make an English version of it and make it available on YouTube.

Hi Pr. Ademario,

You're right, I shouldn't use kcl saturated solution only, I hope I didn't damaged my electrode.

Thanks for your explanation, it is clear for me now, I will do it and let you know.

For the video, I will watch it and try to undestand, for the English version, It will help a lot.

Thanks for your answers and your time.

You are welcome.

The Portuguese version is in two videos that can be found at:

https://youtu.be/a6-zv3f_zQc

https://youtu.be/nH4Z6hUyhSw

I will try to produce an English version. However, I can only do it in a couple of weeks or more. These videos in Portuguese cannot be found without their addresses since they are not listed.

Please, let me know the evolution of your calibration.

Regards,

Ademario

Thanks for sharing videos links, I didn't find them on YouTube.

I will let you know any evolution.

Looking forward for your english version.

Regards

Amel

Hi Pr. Ademario,

I would like to know the molarity or the concentration of Agno3 solution in order to prepare it.

Thanks

Hi, Amel

You should notice that you need only a drop of the AgNO3 solution and the precipitant (AgCl) is highly insoluble. Besides, AgNO3 is normally expensive. Thus, prepare the smallest amount that you can. I think you can prepare a 0.100 mol/L solution or even a more diluted solution. You should also acidify the AgNO3 solution with a few drops of concentrated HNO3 to avoid Ag2O precipitation and avoid exposure to light when you store this AgNO3 solution. You can need it in the future.

Hi Pr. Ademario,

Okay, I will prepare 0.1 M then.

Thanks for your advices and your explication.

Hi Pr.Ademario,

I refilled my eletrode with the saturated solution of kcl+Agcl.

In attached files you can find my calibration curve in 2 points (pH 4 and pH7), i watched your videos and followed your explanations. I hope i did it correctly.

I rely on your corrections and explanations.

Thanks

Hi, Amel

It seems your electrode is ok. However, you can improve your calibration using more than two standard buffers. I normally use 5, although the everyday calibration is just the one you did. When you use 5 standards, you are also verifying the reliability of your standards because they must align themselves with a good R2. After verifying their reliability, you can proceed using just two of them to calibrate for your everyday usage.

I have started my video translation. There is already a 10 min video in English. I hope I can have the first draft in a couple of weeks.

Hi Pr. Ademario,

Yes, I am happy to read that. I will calibrate it by using more standard buffers and let you know.

For the video translation, good news! looking forward to it.

Thanks

If you have a double junction electrode the outer chamber is filled with KCL only as otherwise when using TRIS buffers the silver will precipitate in the juction killing your electrode. If you refill your electrode have a look for the manual for your electrode that should tell you what to use

Thanks Pr. Ne be-von-caron for your answer, I will check the manual once again.