I purchased the Milwaukee 102 PH meter and just used it for the first time today. I am not quite sure how I store the PH meter stick in between usage. I have seen the storage solutions for sale but I don't how know to use it. Am I supposed to put something in the plastic cap that goes over the PH reader? Please help as I want to make sure that the meter lasts a long time. Picture below to reference. Thanks.
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I have a 500 mL bottle of storage solution and I've cut a hole in the cap so that I can insert the probe. That is where my pH probe resides when not in use.
You can use the probe condom. However, you need to have a little dose of storage solution in there. The objective is to have a saturated solution of KCl in contact with the exterior of the bulb to help equalize the osmotic stress and prevent any water or ionic loss from the bulb.
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I built a holder for my pH meter that also holds an old pill bottle with cut out top. That's where I keep the probe submerged in storage solution. It makes sense to ensure a tight fit of the probe to reduce evaporation.
You should follow the manufacturers instructions in this regard. They usually direct you to put a couple of drops of their storage solution (which is usually saturated potassium chloride) into the provided cap (which often contains a little sponge). The goal is to keep the bulb (and reference frit) from drying out.
You should check on the cap from time to time as potassium chloride solution 'creeps' i.e. climbs out of containers it is placed in. After a week or two you will find crystals of potassium chloride well up on the side of the electrode.
Go to the grocery store and get some 'co salt' or whatever they call it. It's potassium chloride. Dissolve as much as you can of that in some tap water (or distilled water if you have it) and use that.
From the picture it appears that the electrode is gel filled. I think the real problem with distilled water is that it will migrate through the frit into the gel in order to try to equalize the chemical potentials of potassium and chloride across the frit. I've had essentially this happen with a sodium ion selective electrode (built identically to a pH electrode except for the sense glass).
Another option is rise it off withe DI water, put the cap on and put it away. If probably won't dry out in the time it takes the storage solution to get to you and if it does that's not a big deal - just rehydrate it (I assume it was shipped dry).