TA Test Question

[jpp7717]

Is the below a correct way to test for TA with a PH meter:

Calibrate PH meter with 7.0 solution

Take 15ml sample of wine
Add to it 20ml of distilled water
Slowly drop 10ml of .2 NaOH into the mixture until PH reads 8.2

Each ml will represent .1 of TA in the wine

ie if i use 5 ml my % is .50

thanks

 

[robie]

Is the below a correct way to test for TA with a PH meter:

Calibrate PH meter with 7.0 solution

Take 15ml sample of wine
Add to it 20ml of distilled water
Slowly drop 10ml of .2 NaOH into the mixture until PH reads 8.2

Each ml will represent .1 of TA in the wine

ie if i use 5 ml my % is .50

thanks

I use Steve's method:

http://www.winemakingtalk.com/forum/showthread.php?t=11244

His method calls for .2 NaOH, 10ml of sample, and a .75 multiplier.

It all depends on how much actual wine sample you use and if you are using .2 or .1 NaOH. Depending on which you use, the multiplier changes.

Just remember to go slow after you get close to 8.2 PH. Also, don't be surprised if you see the PH value actual drop sometimes before it eventually rises.

 

[jpp7717]

I use Steve's method:

http://www.winemakingtalk.com/forum/showthread.php?t=11244

His method calls for .2 NaOH, 10ml of sample, and a .75 multiplier.

It all depends on how much actual wine sample you use and if you are using .2 or .1 NaOH. Depending on which you use, the multiplier changes.

Just remember to go slow after you get close to 8.2 PH. Also, don't be surprised if you see the PH value actual drop sometimes before it eventually rises.

It looks like he is using .1 NaOH in that picture, not .2, or am I reading that incorrectly?

Also do you know why you multiply by .75?

Thanks

 

[robie]

It looks like he is using .1 NaOH in that picture, not .2, or am I reading that incorrectly?
Also do you know why you multiply by .75?
Thanks

Thanks for catching my mistake. I do use the correct one, though. The .1 and .2 makes a big difference in the calculation.

The .75 is based on the amount of wine sample of 10ml and NaOH of .1 strength. If you change the sample size or the NaOH, you change the multiplier. IBGLOWIN is a chemical engineer and Steve is probably better at math than me, so I'll let one of them explain it better for you.

Math Whiz I am not!!!

 

[buddy]

If you are using a ph meter then you really don't need to add any distilled water as this is only used to make the color change more easily seen when using the indicator solution.

 

[ibglowin]

The factor can change based on the sample size or the strength of NaoH. 0.2 NaoH is 2X as strong as 0.1 NaoH.

Also if using the pH meter you should still add some distilled water as it will help ensure the entire probe is submerged under the solution at all times.

 

[SBWs]

Formula

The formula for TA is TA=(75*N of NaOH*Vol in ml of NaOH used to get to pH of 8.2)/Sample Vol

The 75 comes from dividing the molecular weight of tartaric acid 150.09 by the number of H+ ions donated by each molecule of acid which is 2.

Where I got my information.

 

[rhoffart]

Here is a quick Calculator

If you use NaOH of 0.1

and a 7.5ml wine sample

then your TA and you Titre of NaOH (mL) are 1:1

hope that not too confusing

 

[Rodnboro]

What multiplier to use?

So, if I am using a .2 Sodium Hydroxide solution, what multiplier do I use?

 

[ibglowin]

It still depends on your sample size. If you use 15ml then the multiplier is 1.

If you use 10ml, the multiplier is 0.75

 

[SBWs]

There is only one formula!

The formula is always the same. The only things that change are the normally of the NaOH and the sample size and the amount of NaOH it takes to get to the color change or pH of 8.2. The 75 does not change unless the titration is for a acid other than tartaric acid. You just plug your numbers into the formula to get your acid level.

Example 1: if you used 6 ml of .2 normal NaOH to get to a pH of 8.2 (color change) with a 15 ml sample then the formula would be:

TA= (75*.2*6)/15
TA=90/15
TA=6.0 g/L or .6% or 0.6 g/100mL

Example 2: if you used 7 ml of .1 normal NaOH to get to a pH of 8.2 (color change) with a 10 ml sample then the formula would be:

TA=(75*.1*7)/10
TA=52.5/10
TA=5.25 g/L or .525% or 0.525 g/100mL

 

[djrockinsteve]

When using your ph meter I always move the meter around in the liquid. Gotta keep the probes wet and since you are adding SO2 you need to be sure it is well blended in the sample.

The reading normally starts high and descends as the solution mixes. After awhile you will get an idea of where you will be when approaching 8.2 on your meter. .60% TA would be 8ml of solution added (75%).

Most of the California wines I do are in the .60-.65% range. From Erie and New York they have been much higher. Same for those from NC.

Never be afraid to ask a question so that you understand. Stop and think about what you are doing and "why" you are doing that. Measure carefully and make sure you are adding "teaspoons" and not "tablespoons".