I have 1/5N NaOH. If I use it to test acid using a ph meter do I double
the reading?

I plan on buying some 1/10, but for the time being...

"Marty Phee" > wrote in message
. com...
>I have 1/5N NaOH. If I use it to test acid using a ph meter do I double
>the reading?
>
> I plan on buying some 1/10, but for the time being...

No need to buy 0.1N when you have 0.2N on hand. Either use what you have
directly and double the volume reading or dilute it 1:1 and use that.

Fortunately, TA measurements aren't that terribly critical. Accuracy to ±
0.5 g/100 ml is good enough for winemaking purposes. You should be able to
do that well, despite the fact that your NaOH standard will slowly change
over time as it absorbs atmospheric CO2. :^/

If you _really_ needed an an accurate result you'd want to standardize the
NaOH solution against 3 or 4 carefully dried and weighed (to the nearest
0.0001 g) samples of potassium hydrogen phthalate (measuring the NaOH to the
nearest 0.01 ml) and average the results. I did this in chem lab in college
many years ago. It's tedious, but teaches one good technique and
discipline.

Tom S
www.chateauburbank.com

Yeah, the standard freshman chem second lab (the first is using the
analytical balance).

It is enough to make someone NOT want to be a chemist. And it is
funny, winemaking is one of the last industries to use
titration....other labs like water quality have long since switches to
much more sensitive methods.

Thanks. I finally figured it out. I was using 5ml sample and getting
weird results. I increased to 15ml per other sites and the numbers came
out where they should.

I was going off of directions for using 0,1N, but using 0.2N and was
getting confused.

Still learning about all of this.

My sangiovese is finally where it should be.

The rest are a little low.
Chianti TA 5.5, pH 3.57, Pinot Nior TA 4.5 pH 3.6+.



Tom S wrote:
> "Marty Phee" > wrote in message
> . com...
>> I have 1/5N NaOH. If I use it to test acid using a ph meter do I double
>> the reading?
>>
>> I plan on buying some 1/10, but for the time being...
>
> No need to buy 0.1N when you have 0.2N on hand. Either use what you have
> directly and double the volume reading or dilute it 1:1 and use that.
>
> Fortunately, TA measurements aren't that terribly critical. Accuracy to ±
> 0.5 g/100 ml is good enough for winemaking purposes. You should be able to
> do that well, despite the fact that your NaOH standard will slowly change
> over time as it absorbs atmospheric CO2. :^/
>
> If you _really_ needed an an accurate result you'd want to standardize the
> NaOH solution against 3 or 4 carefully dried and weighed (to the nearest
> 0.0001 g) samples of potassium hydrogen phthalate (measuring the NaOH to the
> nearest 0.01 ml) and average the results. I did this in chem lab in college
> many years ago. It's tedious, but teaches one good technique and
> discipline.
>
> Tom S
> www.chateauburbank.com
>
>

"Marty Phee" > wrote in message
news
> Thanks. I finally figured it out. I was using 5ml sample and getting
> weird results. I increased to 15ml per other sites and the numbers came
> out where they should.
>
> I was going off of directions for using 0,1N, but using 0.2N and was
> getting confused.
>
> Still learning about all of this.
>
> My sangiovese is finally where it should be.
>
> The rest are a little low.
> Chianti TA 5.5, pH 3.57, Pinot Noir TA 4.5 pH 3.6+.

If those pH numbers are accurate I'm not so sure I'd monkey with the TA.
Those are reasonable for red wines. OTOH, if the wines taste flat you might
kick the TA up a tad with tartaric and chill out the excess bitartrate. Let
your palate be your guide. The numbers are _guidelines_ - not rules.

Tom S
www.chateauburbank.com