pH Meter Calibration

mbobhat said:

I have one of those probes, but I never liked the cap design really, when you put the probe on its side the fluid looks like it could leak leaving the probe dry, that's probably why they say tap water, because if KCL leaked out you would get salt drying on the glass.

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Certainly KCl deposited on the glass is not a problem for a pH bulb as most manufacturers bathe their bulbs in a saturated solution of it in storage.

mbobhat said:

if you wanted to you could make up a KCL solution (I think they sell potassium chloride at aquarium stores) and just make it and put in a tall screwtop plastic container, cut a hole in the lid so that your probe fits in suspended in the container,and keep your probe upright soaking in KCL without the cap. KCL storage solution will last forever, especially if you cap the container. If it starts to dry just add some tap water to keep the level up.

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KCl is subject to creep. If there is any way out of a container a KCl solution will find it, dry out and deposit crysals. Everyone who has owned a pH meter has squirted dried KCl off various parts of the electrode.

One can, of course, easily prepare a saturated KCl solution for use as a storage solution using KCl bought at the supermarket (Co-salt) but one would be foolish to do so as opposed to using one prepared by the manufacturer of the probe one is storing. The reference electrolyte is very probably KCl but is not necessarily so. Don't use KCl for a Hach electrode, for example.

The people at Hach can't seem to make up their minds as to whether to store their electrode dry or not. It just makes sense to me that as the bulb clearly does not need to be hydrated in storage but does in use one could keep it partially hydrated by putting a couple of drops of DI water in the cap this keeping the RH in there pretty high. I'm guessing that this would allow quicker hydration when putting the electrode to use and people, including Hach, seem to have adopted this suggestion (or perhaps they thought of it themselves).

If you store a Hach meter in this way keep it vertical. It doesn't matter wrt the bulb but I don't think you want the water on the reference.

That's it. Aqueous solutions of KCl rand liquid helium at near 0 K are apparently the only fluids that exhibit this phenomenon.

After several uses I deem this meter only fit for a dumpster... waste of money. Steer clear.

Others have mentioned the issues and i can confirm they are 100% accurate.

If anyone else would like to experience the frustration of dealing with this thing i'll send it to you for the cost of shipping, otherwise it's going in the trash.