What's the deal with storage solution btw?
Revised buying guide for pH meter (based on the book Water)
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What's the deal with storage solution btw?
Storage solution typically has a high ionic content that helps reduce leaching of the electrolyte from the probe and keeps the bulb saturated. The solution is often a solution of potassium chloride along with some sort of preservative like sodium benzoate. Some probes include a water tight cap that helps the bulb stay saturated.
The art in the pH meter lies not, as you might at first think, in the pH sensing glass bulb but rather in the thing that connects to the other side of the circuit: the reference junction. This is usually a porous ceramic frit of some sort or even just a strip of rag but the important aspect of it is that ions must be able to flow through it. The interior part usually contains a solution saturated WRT potassium chloride (3M) and silver chloride. Potassium chloride solution is one of two substances (the other being Helium II) which is capable of creep i.e. it can easily make it's way through the frit unless the chemical potential of potassium chloride on the other side of the frit is the same as it is interior to the electrode. The same is true of water: it will migrate from one side of the frit to the other unless the chemical potential of water is the same on both sides. How do we equalize chemical potential of KCl and H2O across the frit? Bathe both sides of the frit is equimolar aqueous solutions of KCl. Thus most pH meter's storage solutions are saturated solutions of KCl.
Were it not for this situation with the reference junction electrodes could be stored dry (and indeed some are) but this can be inconvenient as the actual pH sensing requires a hydrated layer on both sides of the glass. If an electrode is stored dry it must be hydrated before use and this can take 20 minutes or more. Thus a second benefit of storing in 3M KCl is that the electrode is hydrated and ready to roll as soon as it is removed from the storage solution.
If your storage solution is indeed KCl the creep will signal this fact. The liquid will creep out around the edges of the cap and deposit crystals on the outside and up the probe body. These are harmless and easily rinsed away with a blast of DI water from a squirt bottle but the storage solution that has crept out must be replaced.
Were it not for this situation with the reference junction electrodes could be stored dry (and indeed some are) but this can be inconvenient as the actual pH sensing requires a hydrated layer on both sides of the glass. If an electrode is stored dry it must be hydrated before use and this can take 20 minutes or more. Thus a second benefit of storing in 3M KCl is that the electrode is hydrated and ready to roll as soon as it is removed from the storage solution.
If your storage solution is indeed KCl the creep will signal this fact. The liquid will creep out around the edges of the cap and deposit crystals on the outside and up the probe body. These are harmless and easily rinsed away with a blast of DI water from a squirt bottle but the storage solution that has crept out must be replaced.
Ferny78
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Hello, first of all I would like to thank all the people who posted useful information for purchasing a pH-meter. Taking into account the different options where I live (Spain), I decided to get the Omega PHH-7011. Today I performed a stability test after the first calibration and I wanted to share the results. I know it is too soon, but based on these results, I'm quite happy with the purchase.
Looks good to me.
lurchalicious
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Anyone have feedback on meters since the last posting in 2016?
I have been reading over multiple threads however some of the information seems above my knowledge. I just want to make sure my mash water is in good range for efficiency.
Amazon is flooded with 14-16 dollar meters that seem like they fit the bill, but these can't possibly be worth dealing with are they?
I have been reading over multiple threads however some of the information seems above my knowledge. I just want to make sure my mash water is in good range for efficiency.
Amazon is flooded with 14-16 dollar meters that seem like they fit the bill, but these can't possibly be worth dealing with are they?
There are some here that swear by these cheap meters but most who buy them wind up swearing at them.
Am I being an idiot by keeping the MW102 probe in storage solution in a beaker, covered over with plastic film to slow evaporation (not very well - crystallization is crazy)? Can I safely saturate the - don't know what it's called, some sort of cap with a sponge at the bottom, a tube that slips over the electrode - can I saturate this, slip the probe in this, for storage? Seems like I'm burning a lot of storage solution and concerned about the amount of crystallization that gathers on the probe, beaker, everything.
"KCL creep happens", I get that on my Hanna big time, much less so on the Hach because it has an O-ringed cap unlike the Hanna.
I'm surprised the MW102 doesn't have a probe cap you could simply fill with storage solution, as I do with the Hanna and Hach models.
Is the cross-section above the bulb end round? If so I bet you could come up with some kind of cap for it...
Cheers!
I'm surprised the MW102 doesn't have a probe cap you could simply fill with storage solution, as I do with the Hanna and Hach models.
Is the cross-section above the bulb end round? If so I bet you could come up with some kind of cap for it...
Cheers!
No problem with doing things this way except...
Storage solutions are almost always saturated solutions of KCl. Thus water evaporation is not a problem from the POV of the strength of the solution. It stays saturated. Deposition of KCl crystals on the electrode is not a problem either. Just rinse them off with a stream of DI water from a lab squirt bottle.
Yes. That is how the manufacturer intends it to be stored. The sponge is there to retain some liquid it being important to keep the bulb moist rather than wet. The only problem with the storage cap approach is that KCl creep will eventually remove the liquid even if the electrode with cap is stored vertically so be sure to check it and top it off from time to time if you are using it infrequently.
You shouldn't be seeing this in the Hach because you shouldn't be filling the cap with storage solution. A few drops of DI water in the bottom of the cap with the meter stored vertically keep the humidity inside the cap high enough to keep bulb and junction hydrated.
It does.
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The MW 102 probe cap:
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And yes, we still have the MW102 on sale.
http://www.buckeyehydro.com/mw102-ph-meter/
Use the coupon code HBT MW102 for $15 off. For Home Brew Talk users only.
Russ
http://www.buckeyehydro.com/mw102-ph-meter/
Use the coupon code HBT MW102 for $15 off. For Home Brew Talk users only.
Russ
OK great, many thanks AJ.
You as well, Buckeye.
I'm really liking my Thermoworks 8689. It's budget friendly and very effective. They also have good customer support.
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No, they aren't. Uber low end pH meters are really not worth owning.
