Acid Titration Kit

[cbritton]

I've had an acid titration kit sitting with my wine equipment for about 2 months but I've been too intimidated to try it until today.
Is it really as easy as the instructions make it seem?
Any hints?

 

[ibglowin]

Its easy if your using a pH meter to read the endpoint! Not so much if your using your eyeball and your testing a red wine.......

 

[olusteebus]

Its easy if your using a pH meter to read the endpoint! Not so much if your using your eyeball and your testing a red wine.......

Uh, what do you mean endpoint?

 

[ibglowin]

The endpoint of a TA reading with a pH meter is 8.2

 

[Julie]

When I first started out I used a titration kit and to be honest I really did not have a problem seeing the color change. Yes a ph meter would be more accurate but to be honest when you are first starting out and still learning the ropes, the titration kit is going to do the job, it will get you into the ballpark that you want to be in. Don't be intimated by it, go test some wine! You will do fine.

 

[JohnT]

I agree with julie.

A titration kit might not be all together that precise, but it does not need to be. The "margin for error" is normally so minor that it is definitely "good enough". just add your Sodium Hydroxide S L O W L Y and run the test twice to confirm your results.

johnT.

 

[olusteebus]

Ok, I have searched and finally found something I can almost understand about reaching the "endpoint" to determine the ta in a wine. Here it is:

"The technique is simple. Although it isn't absolutely necessary, you will get more accuracy if you re-calibrate your pH pen using a pH 7 buffer. Measure out a 15 millilitre sample of the red wine or must to be tested and place it in a beaker.

Fill a syringe with 0.2 N sodium hydroxide. With the pH pen held in the sample, start adding sodium hydroxide while continuously swirling the container.

You will observe that the digital reading of the pen soon begins to climb. You need to take it up until it reads pH 8.2, adding drops very slowly as you approach that point.

The number of millilitres of sodium hydroxide used to reach pH 8.2 gives you the TA in g/L."

How does it give me the TA when it reaches 8.2. If I count the millilitres, is there some conversion.

I am sorry I don't get it. I didn't have chemistry in high school or college. I had mechanical drawing and a two hour phys ed class instead!

 

[grapeman]

Those who do a lot of acid testing read the final reading in g/L so 7.5 ml to get to the endpoint (with .2N solution), it means you have 7.5g/L. Since it is metric if you read it as percentage, then divide by 100 so the 7.5g = .75%TA It doesn't get much easier than that. Just titrate the solution until the meter reads 8.2. That is the pH reading of the solution when the phenylalanine would normally change colors. If intersted try it that way and compare.

 

[ibglowin]

8.2 is the pH where the phenolphthalein indicator changes color with the tartaric acid. (Endpoint)

There is no conversion if you use that amount of sample and that strength of NaOH. If you use a different sample size or a weaker solution of NaOH (0.1) then yes, there is a different multiplication factor.

 

[olusteebus]

So, if I add sodium hydroxide to a vile of wine with the probe in it, once the ph meter reads 8.2, I determing the number of cc's it took. If it reaches 8.2 with 7 cc's, it is a ta of .70, is that correct?

Thanks for putting up with my ignorance.

 

[ibglowin]

Yes, just remember you have to use the right amount of wine 15ml for 0.2N NaOH

You can add distilled water to the wine sample to bring up the volume.

If you really, really want to be a stickler you can start off with distilled water that you have brought to pH 8.2 before you add the wine sample to it. Then add your wine, then titrate again back to to 8.2 and read your syringe for amount of NaOH added.