Checking TA with PH Meter

[Goodfella]

Hi Everybody,


I am still new to my Hanna PH Meter. George told me how to check the TA with this, But I am not sure if I have it correct.


I think ya take 15 ML of must and start adding Sodium Hydroxide... When the meter reads 8.2 you check how many ML sodium hydroxide was used... And that is your TA. (Example 6 ML S.H.= .60 TA)


Is this correct?


Thanks for your help...


Joel

 

[ibglowin]

It depends on the Normality (strength) of your NaOH. If your using 0.1N then you multiply the ml required by 1.5

 

[Goodfella]

Meaning 6 ML of .1 NaOH= .90 TA?

 

[ibglowin]

I forgot to mention its also dependent on sample size.

Here is the link to the FVW Acid Testing page. Looks like sample size is 15ml and NaOH is 0.2N in order to get it to come out 1 to 1 like what you were thinking.

If you use 5ml sample and 0.1N NaOH then you multiply the result by 1.5.

 

[Goodfella]

I am using .10








So I am still a little confused... on a 15 ML sample and .10N solution... am I accurate on 6 MLs= .60 TA?


I tested a must from fresh Apple cider I am making into wine, I have not added any Acid... The PH was 3.5.... Using this method the TA was .90 (pretty high). But then I checked with a Accuvin Acid test and that said .70


I have also had a must that was 3.7 PH and the TA was .75.... I am confused because PH 3.7 is somewhat high, but to lower the PH you raise the TA.... But .75 TA is already high???????

 

[ibglowin]

Here is the Equation for using any sample size and any strength NaOH.

TA as tartaric acid (g/100 ml) = _(V) (N) (75) (100)_
(1000) (v)

V = ml of sodium hydroxide solution used for titration
N = Normality of sodium hydroxide solution
v = sample volume (ml)

If the above procedure is followed, the total titratable acidity can be calculated by multiplying the volume of 0.1 N NaOH used by a factor of .15.

Example: 6 ml of 0.1 N, NaOH was used to titrate a 5 ml wine sample, what is the TA of the wine?

Answer: 6 x .15 = .9% TA

So for your example you have:

(6ml NaOH used) x (0.1N NaOH) x (75) x (100) / (1000 x 15ml sample) = 0.3 TA

 

[Goodfella]

I'mconfused....


6 x .1 x 75 x 100/1000 x 15 gives me 675 (or something)


I am also confused because .3 TA sounds more what I would expect, but the Accuvin was .70 (I know the color tests are sometimes hard to read, but this was pretty clear)


P.S Thanks for taking time with me on this Mike!!!

 

[ibglowin]

(6 x 0.1 x 75 x 100) / (1000 x 15) = 0.3

 

[Goodfella]

Getting my butt kicked trying to check the acidity using my PH Meter!!!


I think I finally have the math down, But as I drop the Sodium Hydroxide in my test.... The meter jumps way up.... Then SLOWLY counts back down....


Am I missing something? (I am stirring as i drip)

 

[ibglowin]

Stirring or swirling?

Its normal for it to jump up and then stabilize as the NaOH gets evenly distributed throughout the vial. The faster you stir the quicker the distribution and the faster the reading will stabilize.

Patience grasshopper!

 

[Goodfella]

I am swirling.....


I left it in a buffer solution just to see what it would do...


It slowly dropped in that also....


Maybe it's messed up?

 

[ibglowin]

Its OK to slowly drop but it should stabilize at some point. Is this a new meter, old meter that has been heavily used? Stirring (mag stirrer of sorts) is MUCH better than swirling but it should line out either way. Buffer could be old, battery could need replacing, probe could be dirty or malfunctioning.

Here is a video on [ame="http://www.youtube.com/watch?v=XstQOtL3H8E"]Measuring TA with a pH meter[/ame]

 

[Goodfella]

Its a new meter...


Battery, ect. should be good, but something is acting funny.


Thanks for the video link. I actually watched that the other day.


I will keep working with it and keep ya posted...

 

[Randoneur]

Is your sample container sized so that you have the end of the pH meter covered with the sample? The bulbneeds to be flooded while swirling the sample.

 

[Wade E]

When you first start it up what does it say for battery power?

 

[Goodfella]

Battery says 100%.... its brand new.


Yes, I make sure the end is covered. My test jar is narrow.

 

[Randoneur]

What does it look like in a two point calibration if you retest both calibration solutions? Use fresh calibration solutions and see what happens. Your calibration will be off if the solutions are not fresh.



My Hanna pH 5 always acts strange if the calibration solutions are off point a little bit.

 

[Goodfella]

Its kind of strange.... I tried the calibration solutions (the day I was having the troubles). It would read correct at first, then it would slowly count down!!!


I will try it again soon...... see what happens....

 

[Wade E]

You did let it sit in the solution for the hour at first right to acclimate the probe? Maybe you better give George a call on this soon if you dont figure it out.

 

[Goodfella]

I have the cap filled with 4.01 solution.