Question on PH meter samples

Here is a question I always wanted to ask..

I normally do a ph test on a 100 ml sample. I have a chemist friend that told me that 100ml is a good sample size.

I was doing my PH tests this weekend and the question struck me. Is there an optimum sample size for a PH meter? I believe that one will get the same reading no matter what the sample size. anyone know why size does not mater? could I simply stick my probe into a 500 liter tank?

JohnT said:

anyone know why size does not mater?

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I will defer this to the ladies of the forum.

Sorry, John, couldn't resist. You lobbed that one right out there.

wineforfun said:

I will defer this to the ladies of the forum.

Sorry, John, couldn't resist. You lobbed that one right out there.

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OMG, Too Funny!!! I was so fixated on the question above and I did not see that one...

Size doesn't matter. LOL What matters is that the sample is mixed well (must stirred) and that the probe tip is fully immersed. No reason you can't stick the probe right into the primary.

That is what I understood, but do you know why sample-size makes no difference?

A pH meter works sorta like a volt meter but instead of measuring electricity, its measuring pH.

Yes, but wouldn't it make sense that more wine means more free electrons, therefore higher PH?

I know that this is not how things works here, but I just want to understand. I guess I should have stayed awake in chemistry class....

I don't use but about 10 to 15 cc's! I prefer drinking my wine, not testing it.

500 ml seems like a lot to me.

First @ olusteebus. pH measurement is an NDA (non destructive assay) so you can just pour the sample back into the primary or wherever it came from.

@ John, an acidic solution has far more positively charged hydrogen ions in it than an alkaline one, so it has greater potential to produce an electric current in a certain situation—in other words, it's a bit like a battery that can produce a greater voltage. A pH meter takes advantage of this and works like a voltmeter: it measures the voltage (electrical potential) produced by the solution whose acidity we're interested in, compares it with the voltage of a known solution (inside the electrode), and uses the difference in voltage (the "potential difference") between them to deduce the difference in pH.

JohnT said:

Yes, but wouldn't it make sense that more wine means more free electrons, therefore higher PH?

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pH is a measure of per unit of whatever. So, having more units does not increase the pH. It does increase how much base can be neutralized.

OK,

Thanks guys! I think I get it now....

You only need enough wine to cover the electrode.