TA Question

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silverbullet07

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ta g/L = (V *.1 *75)/ S

where V = mL Titrant needed to reach the endpoint; 0.1 = normality of the Titrant, S = mL sample. The value 75 is the equivalent weight of tartaric acid.


If I pull a 5ml sample of wine and add 15 ml of distilled water is S =20ml Or S =5ml ?
 
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silverbullet07

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Someone on another forum reported that I would use 5ml. The distilled water is neutral and does not effect the results. hopefully that is correct.
 

distancerunner

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Assuming that you are diluting the sample with distilled water in order to see the color change.

The sample is 5ml. The water does not affect the result of the test.
 

silverbullet07

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Thanks. Yes but I am using a ph meter and watching the meter reading as I add the sodium hydroxide.
 
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distancerunner

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Doesn't matter.

But why not just use a larger sample of wine? 10ml in a 50ml beaker is deep enough to contact the bulb of the pH meter. Two volumes of liquid increases the margin of error. At least it would for me.
 

silverbullet07

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Just something I was trying. Saw you could do it that way. i thought it uses less sodium hydroxide with a smaller sample. Maybe not.
 

Rice_Guy

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your formula is correct
* S is always the sample (normally) expressed as a volume. My kit uses 15ml for S.
E4886F84-10D5-444D-812D-005FB7079EF8.jpeg
* distilled water is transparent therefore you can add as much as you want/ don’t have to measure it
* there are other Normalities of NaOH available, presently I use 0.1N by BSG, used to get LD Carlson 0.2N but they have some lots that are 1.00N (anyone else have problems with LD C/ I have bought kits just for good NaOH)
* the vinmetrica TA test is with a 0.133N and 5 ml sample volume.
* I frequently change sample size for example if running cranberry juice or lemon juice I don’t waste titrant and use one ml. If you use the provided syringe you increase the error by reducing sample size. You can get around this by weighing the sample to two place accuracy and multiplying by the hydrometer reading.
* I also run TA on pulpy material and record the answer as a weight percent (work was all solid material which would be run in a blender with distilled water) If you are dealing with steeping crushed fruit in the primary a weight based number is more useful.
* I see drift on titrations with particulates (ex cider today). A good result will wait for the pH to reach steady state, in cider today that means let the probe sit with the pH 8.20 reading a minute before saying the answer is correct. Pulpy fruit like korean dogwood take longer. This can be minimized by mixing 100 gm with 100 gm of distilled water and blending (work was two minutes) or by mashing the 5.00 grams with a spoon washing the spoon in with a spray bottle, and then letting the sample equilibrate 15 minutes.
* Vinmetrica has a very good write up on TA in the SC300 manual, pg15.
ta g/L = (V *.1 *75)/ S

where V = mL Titrant needed to reach the endpoint; 0.1 = normality of the Titrant, S = mL sample. The value 75 is the equivalent weight of tartaric acid.

If I pull a 5ml sample of wine and add 15 ml of distilled water is S =20ml Or S =5ml ?
E1EC86C7-84E8-4D85-AC07-7ADCEB3BEACA.jpeg
some of today’s TA testing. note a small hydrometer allows a 15ml gravity sample size
note 2, the Extech has a flat glass “bulb” so I can run things like blocks of cheese or a liquid sample that is two drops (~0.05ml)
 
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silverbullet07

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your formula is correct
* S is always the sample (normally) expressed as a volume. My kit uses 15ml for S.
View attachment 83816
* distilled water is transparent therefore you can add as much as you want/ don’t have to measure it
* there are other Normalities of NaOH available, presently I use 0.1N by BSG, used to get LD Carlson 0.2N but they have some lots that are 1.00N (anyone else have problems with LD C/ I have bought kits just for good NaOH)
* the vinmetrica TA test is with a 0.133N and 5 ml sample volume.
* I frequently change sample size for example if running cranberry juice or lemon juice I don’t waste titrant and use one ml. If you use the provided syringe you increase the error by reducing sample size. You can get around this by weighing the sample to two place accuracy and multiplying by the hydrometer reading.
* I also run TA on pulpy material and record the answer as a weight percent (work was all solid material which would be run in a blender with distilled water) If you are dealing with steeping crushed fruit in the primary a weight based number is more useful.
* I see drift on titrations with particulates (ex cider today). A good result will wait for the pH to reach steady state, in cider today that means let the probe sit with the pH 8.20 reading a minute before saying the answer is correct. Pulpy fruit like korean dogwood take longer. This can be minimized by mixing 100 gm with 100 gm of distilled water and blending (work was two minutes) or by mashing the 5.00 grams with a spoon washing the spoon in with a spray bottle, and then letting the sample equilibrate 15 minutes.
* Vinmetrica has a very good write up on TA in the SC300 manual, pg15.

View attachment 83820
some of today’s TA testing. note a small hydrometer allows a 15ml gravity sample size
note 2, the Extech has a flat glass “bulb” so I can run things like blocks of cheese or a liquid sample that is two drops (~0.05ml)
Thanks for all the details!
 

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