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Author: Subject: pH measurement tool?
Smoker Root
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[*] posted on 13-10-2019 at 14:54
pH measurement tool?


Hi, I am going to procced on a reaction which is extreamly pH sensitive. I am working with materials that corrode easily plastics and needs a pH measuring tool which can preciley measure in the range of 5.0-8.0
I can't find any of this precision in a normal pH paper, and the elctronic pH readers I have looked uo, all have plastic.
So what should I get?
Thanks
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Sulaiman
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[*] posted on 13-10-2019 at 16:39


What do you consider to be precise ?
(+/- 0.1 pH, +/- 0.01pH etc.)

I bought two cheap digital +/-0.1pH resolution meters,
probably my most useless chemistry hobby purchase :(

I now use pH papers for approximate measurements (so far good enough for my purposes)
and VERY occasionally, titration for accurate measurement of molarity, which could be converted to pH.

eBay has pH papers for many ranges
(1-14, 3.8-5.4, 5.4-7.0, 6.4-8.0, 6.9-8.4, ....)
if you need better accuracy than that then I guess that you are looking at
a very expensive pH meter with buffered pH reference solutions and a lot of care,
or titrations.

from memory, pH measurment is quite temperature sensitive in the range that you are considering.

EDIT: copied this graph from Researchgate https://www.researchgate.net/figure/Variation-of-pH-vs-tempe...

pH_vs_temperature.jpg - 99kB

[Edited on 14-10-2019 by Sulaiman]




CAUTION : Hobby Chemist, not Professional or even Amateur
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phlogiston
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[*] posted on 14-10-2019 at 01:06


The glass bulb itself in a pH sensor is all glass I believe. And you can get some pretty long ones (30 cm certainly, perhaps even longer), with the plastics (connector etc) at the other end. Perhaps you can shield the connector end from your reaction mixure?



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Arthur Dent
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[*] posted on 15-10-2019 at 12:04


For pH testing, the cheap chinese pH meters from Ali are adequate. As a trick, after you do a reading, immediately dip the probe in cold, distilled water to neutralize your chem. Or rinse it in cold running water. Do two or three readings in a row, and compare (and average) the results.

Using pH calibration solutions, I find that they are fairly accurate, and I prefer them to pH paper. I have two of them and have used them to test the pH of beer wort and yeast solutions. It does the job, and at reasonable pH levels, they remain accurate for a long time! :)




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G-Coupled
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[*] posted on 15-10-2019 at 18:07


Quote: Originally posted by Arthur Dent  
It does the job, and at reasonable pH levels, they remain accurate for a long time! :)


To what kind of values of 'reasonable'? Just not at either of the far extremes?

I have also seen some more glass bulb pH meters that have the bulb at the end of a (presumably also glass) stick.
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B(a)P
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[*] posted on 16-10-2019 at 03:36


They are likely to be plus or minus 0.1 pH unit. Also make sure the probe is stored wet and close to pH neutral.
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[*] posted on 16-10-2019 at 03:58


Quote: Originally posted by B(a)P  
They are likely to be plus or minus 0.1 pH unit. Also make sure the probe is stored wet and close to pH neutral.


Any good ideas for a DIY solution to store probes in?
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Carbon8
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[*] posted on 16-10-2019 at 16:20


Cole-Parmer suggests 4M KCl for the conditioning and storage of electrodes.

https://www.coleparmer.com/tech-article/ph-electrode-care
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[*] posted on 16-10-2019 at 23:43


Quote: Originally posted by Carbon8  
Cole-Parmer suggests 4M KCl for the conditioning and storage of electrodes.

https://www.coleparmer.com/tech-article/ph-electrode-care


Cheers!
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