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Author: Subject: distilled water for diy ph calibration solution ?
itsafineday
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[*] posted on 31-3-2019 at 07:10
distilled water for diy ph calibration solution ?


Does the ph of distilled water vary much ? Can otc distilled water be used to make diy ph calibration solution ?



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[*] posted on 31-3-2019 at 09:47


even distilled water as CO2 dissolved, so its pH is slightly acidic, and can not be ignored. no you can't use distilled water as a calibration source, it would be too easy:D





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[*] posted on 31-3-2019 at 09:54


pH of the distilled water means almost nothing since it has no ionic strength and can't be accurately read by a pH meter. Once the buffer salts are added, they will dominate the pH. However, it is good practice to boil water used to make solutions to expel CO2 and store in tightly sealed containers.
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[*] posted on 31-3-2019 at 10:15


i thought he meant just plain distilled water as the calibration solitution, without a buffer




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draculic acid69
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[*] posted on 31-3-2019 at 10:38


I seen one guy use skim milk as a calibration standard apparently it is ph6 exactly.
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[*] posted on 31-3-2019 at 17:00


The pH of pure water is 7, by definition, because the [H+] = 1 x E-7M. Granted that the ionic strength of pure water is very low, I would think that a decent pH meter would read 7 for a sample of pure water. Certainly to achieve a decent, reliable calibration the use of 1 or more buffer solutions is well-advised.
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[*] posted on 1-4-2019 at 05:43


potassium hydrogen tartrate is a NIST primary pH standard.

Buy yourself some cream of tartar, mix it with distilled or rainwater and use a saturated solution as a pH 3.557 at 25 °C

Cheap !

[Edited on 1-4-2019 by Harristotle]
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itsafineday
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[*] posted on 1-4-2019 at 05:54


Quote: Originally posted by Harristotle  
potassium hydrogen tartrate is a NIST primary pH standard.

Buy yourself some cream of tartar, mix it with distilled or rainwater and use a saturated solution as a pH 3.557 at 25 °C

Cheap !

[Edited on 1-4-2019 by Harristotle]


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[*] posted on 1-4-2019 at 13:06


Quote: Originally posted by CharlieA  
I would think that a decent pH meter would read 7 for a sample of pure water.


I wouldn't.

If you look at this
https://en.wikipedia.org/wiki/Glass_electrode#Construction
there's picture of a pH electrode, and the bit numbered 7 is the problem
It's a "salt bridge" and it will leak buffer from the probe into the water you are trying to measure.

It's much better to use borax near pH9
There's some talk about it here
http://www.reefcentral.com/forums/showthread.php?t=920017

and cream of tartar near pH 3.6 or (if you happen to have it, potassium biphthalate)

Here in the UK Borax is getting hard to find.
You might end up using something like sodium sesquicarbonate. (near pH 9.9)
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