TA Testing w/ Ph Meter

[Flame145]

I have a phep5 digital ph tester, just recently acquired. I was told by one of the guys at the wine store to use this formula for testing TA. Just want to make sure that I understood him right and I am doing the test accurately.

Add 10 ml of must
add .1 NaOH Solution until meter reads 8.2
Multiply the amount of .1 NaOH Solution by .75
That should = TA
example 8 ml solution X .75 = 6.0

Just want to double check.

I seen other posts on this or different formulas but none of the ever state how many ml of must to start with
Thanks

 

[Flame145]

Anyone ?????????

 

[Wade E]

Im no mathematician so I cant tell you if that formula is right but the link below is what ii use.
http://www.yeastwhisperer.com/uploads/YeastWhisp_Guide_to_TA.pdf

 

[Flame145]

Im no mathematician so I cant tell you if that formula is right but the link below is what ii use.
http://www.yeastwhisperer.com/uploads/YeastWhisp_Guide_to_TA.pdf

I read it and I still don't understand why his and any other formula that I have read fails to metion how much must do you use to run the test. Does it matter ?? I would think it has too.

 

[Joedaddy]

That is the formula I use but I mulitply by .075 so in your example, the TA would be .6 instead of 6.0

 

[djrockinsteve]

Yes that would represent 60% acid in your wine

 

[Flame145]

Yes that would represent 60% acid in your wine

OK, so then the formula I'm using is fine. Just wanted to make sure I was checking my TA the correct way. Thanks

 

[Flame145]

That is the formula I use but I mulitply by .075 so in your example, the TA would be .6 instead of 6.0

OHHH, Ok Thanks.

 

[ibglowin]

You are correct, the amount of sample absolutely matters. You would have twice as much acid as a 5ml sample. So does the strength of the NaOH.

I use a TA kit that says to use 5ml instead of 10ml. You use the same 0.1N NaOH but you multiply your results by 1.5 and not 0.75 (inverse proportion)

It should only take 4ml (your example) to reach a pH of 8.2 so it would be 4 x 1.5 =6.0

 

[sjo]

You are correct, the amount of sample absolutely matters. You would have twice as much acid as a 5ml sample. So does the strength of the NaOH.

I use a TA kit that says to use 5ml instead of 10ml. You use the same 0.1N NaOH but you multiply your results by 1.5 and not 0.75 (inverse proportion)

It should only take 4ml (your example) to reach a pH of 8.2 so it would be 4 x 1.5 =6.0

My TA kit says to use 15cc. .2 N NaOH. and no multiplication factor. For you math brainiacs, does this equate the same as glowin's results.
I have no problem following directions and doing the math- the problem arises when every place I look there is a different formula to figure out TA. different NoAH soloutions, Sample sizes and multiplication factors.

 

[ibglowin]

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

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


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

So for your case you would have: V x (0.2) x (75) x (100) / 1000 x (15) = V x (0.1)

So if you want the answer in g/L you would multiply x 10 and you then have V x 1 = V

Now the down side is can you purchase a standardized 0.2N solution? I have only seen 0.1N but looks like you found a 0.2N solution. The other thing is you have to be careful of overshooting the endpoint as you are using a 2X strength of NaOH so each drop will make a big drop in pH especially near the endpoint. Go slow!

 

[Wade E]

Thanks Mike, great job on explaining that. Not one of my strong points!!

 

[ibglowin]

And wood working is not one of my strong points!

 

[Wade E]

I tell you what, You help my daughter with her homework and Ill redo your cabinets or stairs.

 

[sjo]

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

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


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

So for your case you would have: V x (0.2) x (75) x (100) / 1000 x (15) = V x (0.1)

So if you want the answer in g/L you would multiply x 100 and you then have V x 1 = V

Now the down side is can you purchase a standardized 0.2N solution? I have only seen 0.1N but looks like you found a 0.2N solution. The other thing is you have to be careful of overshooting the endpoint as you are using a 2X strength of NaOH so each drop will make a big drop in pH especially near the endpoint. Go slow!

My TA test kit had .2 and all additional bottles of solution I have purchased is also .2NoAH. Which explains why it is tough to reach 8.2 without overshooting.
Test kit states that CC's of solution used to achieve color change equates to percent of acid. 5cc's = .5%
I purchased PH meter and searched for TA measurement procedure with meter. I found the only thing different was using the end point of 8.2 on the meter instead of color change. The correlation between the cc's of solution and % of acid stayed the same. 5cc's = 5%

As I pause in thought and before I lose it (my thought) A quick glance back to your formulas still leave me confused. Maybe here is where the elevator gets stuck. Am I seeing to different ways of measuring acid?
1. g/l (grams per liter)?
2. %
If so please help me out with this math.
I tested currant juice yesterday. I had 15cc sample, used 11 cc NoAH to get to 8.2 and noah was .2
My experience tells me I had 1.1% acid. Is this correct and what would it be in g/l?

Thanks
Scott

 

[Wade E]

That would be 11 g/l.. You are basically just moving the decimal over 1 spot. That acid is a little high and you will want to most likely cold stabilize and or use an agent to lower it.

 

[ibglowin]

Wade is correct.

TA is usually expressed in Grams per Liter (g/L). If you wish to think in terms of % then divide your result by 10. In your case 11/10 = 1.1%

Just noticed I had one too many zeros in my post (#11) above. Should be x 10 not 100 as originally posted.

 

[Rock]

Here is what i do,never mind all that math for me.Calibrate your meter,15mls wine sample into beaker,add 5mls of distilled water mix well.starting using your ph meter into sample.draw up 10mls of .2ns/h and slowly add to sample.When ph meter reaches 8.2 stop.Read how much .2n you used 1ml=.1g/l

 

[Wade E]

Now thats more along my math!!!!!!!! Basically what I do but have to have it written down and in my drawer to follow. Maybe someday ill get used to it and not need it on paper to follow.