# PH probe



## Slochteren (Mar 1, 2022)

Hi, I bought some lab equipment, it came with 2 of these PH Probes, on the picture you can see some solids inside the probe, looks like dry silicon. Is this a sign off unusable, like they replaced the probes with new ones and put the unusable back in the box? I have only the probes so I cannot test them. 

Paul


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## MGH (Mar 1, 2022)

> on the picture you can see some solids inside the probe, looks like dry silicon. Is this a sign off unusable...?


Not necessarily. The residue is most likely Potassium Chloride (KCl). It's a common filling solution for pH probes, and will often dry out like that during storage. In and of itself it does not indicate if the probe is functional. You may be able to refill the probe with filling solution (might need to rinse the inside with filling solution once or twice), let the bulb equilibrate, and be good to go. But if it were me I wouldn't bother trying until I had a meter with which to test the probes.

The question still remains, however - why would someone put a functional pH probe back in the box. Yes, it could happen, if a lab is getting packed up to move. Or it could have been placed in the box years earlier "just in case" it might be needed later on. Happens all the time.

Good luck!


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## olawlor (Mar 2, 2022)

Put the probe in a clean beaker filled with deionized or distilled water, and if the white material dissolves within a few minutes, it was almost certainly potassium chloride salt. 

Many electric pH probes are designed to be stored immersed in saturated potassium chloride solution, and are shipped with at least a few drops of this salt solution on them. Stored in a dry place this solution often dries out and the salt creeps out that way, just wash it off and should be ready to go, it's possible the probe has never been removed from the box!


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