pH meter questions

[RalphLambrecht]

I bought a cheap Hanna pH meter and hope to use it for the pool and some darkroom work, such as checking developer pH;I have two questions:
1.Can I calibrate it mixing 5g of Borax in 1 liter of water and assume this to be at pH9.2?
2.In the past I've stored the tip in a strong solution of KCl potassium chloride but the crystals 'grew' all over the meter and the container, making a mess and I lost valuable chemicals.Would a strong solution of Na Cl achieve the same purpose without making the mess?

 

[Alan Johnson]

(1) I calibrate my ebay pH meters in 5g/L Borax as one solution, they seem to be OK within 0.1pH with other known solutions, eg, Xtol.
(2)See Fledarmus:http://www.chemicalforums.com/index.php?topic=50263.0
I assume it is easier to clean up the electrode from creeping KCl than correct for drift with NaCl, I never tried it(the NaCl).

 

[Mick Fagan]

Ralph, I have been using the Hanna pHep range of meters for around 20 years. I have found that the life of the electrode in these meters, can be lengthened by using the Hanna storage solution.
https://www.hannainst.com.au/product/HI70300L/Storage+Solution+460ml

Not being that great in chemistry, I was very much in the dark about what exactly was the best way to store the electrode. A chemist friend regularly made a storage solution for me, increasing the life of the electrode from about 2 years to around 3 years.

I then started using the Hanna storage solution, electrode life went to around 5 years. I am currently still running a pHep 3 Hanna pocket meter. It is around 10 years old, I think it is just starting to fail. Last week when I used it after calibration, it started wandering all over the place, this was with fresh batteries. The perfect excuse to upgrade to the pHep 4 meter. This is by far, the longest I have had one of the Hanna pocket pH meters work.

Previously I used Hanna pH 7 (HI 7007), but with my current pHep 3 and the unit before it, I switched to the Hanna storage solution (HI 70300L) and apart from dropping my prior meter onto the floor, electrode first, I have no reason to believe it wouldn’t have had an extended electrode life like my current pHep 3 Hanna meter.

Mick.

 

[EdoNork]

You can simply wash the electrode with distilled water, refill with a KCl 3.5M solution and wet it with the appropriate maintenance solution. A saturated KCl (3.5M) solution is suggested by manufactures. It's the same solution that fills the electrode.

 

[chrisaisenbrey]

As far as I understand the electrode should be stored in the same solution as the electrolyte solution inside the electrode. For many (but not all) electrodes this is 3M KCl. I think it is not a good idea to replace KCl by NaCl here, because the sodium will diffuse inside the electrode.

I guess a one point calibration with borax is good if you want to measure solutions in this range (e.g. developer).

 

[EdoNork]

Depending on the electrode manufacturer the KCl solution can be either 3M or 3.5M, just check instructions.

 

[chrisaisenbrey]

It can also be saturated AgCl with 3(.5)M KCl depending on the construction of the pH electrode.
So definitely: check instruction!

 

[Alan Johnson]

Buffers I use:
6.86- sold for or with ebay pH meters
9.2- 5g/L Borax
11.6- 50g/L sodium carbonate anh. https://pubchem.ncbi.nlm.nih.gov/compound/sodium_carbonate#section=Decomposition
I always use two, taking into account the expected pH of the solution to be measured.