Titratable Acidity: A Better Way!

A better way to measure titratable acidity?


So what’s that contraption pictured above? I wrote about it back in February, and I think it’s a better way to measure titratable acidity (TA). It works by adding a measured sample of wine to sodium bicarbonate (baking soda). The baking soda reacts with acid in the sample, giving off carbon dioxide gas (CO2) in direct proportion to the amount of acid. This device measures that CO2, and you can use that to determine the TA of the sample.



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15 thoughts on “Titratable Acidity: A Better Way!

  1. Erroll Post author

    Thanks guys,

    I belong to the Puget Sound Amateur Wine and Beer Makers Club, and one of our members makes these. I’ve been wanting to get one from him for a long time, but I haven’t been able to make it to the meetings until recently. This is one of those things that looks easy, even obvious, after someone else explains it.

    I’m really glad I met Don Proctor, because I’d probably be doing titrations for the rest of my life if it weren’t for him. But now that I have one of his devices, and he’s explained it to me, it looks pretty simple. I’ll bet a lot of people could make one just from my brief description and the photo. For the rest, I plan another article or two on the details of how it works and how its made.

    Erroll

  2. Mike

    Errol…

    Last year you tried tomato wine.. Your recipe’s came up in a search.

    After all this, do you think it’s worth it…?? Or should I can tomatoes and put them into the soup and stews instead…

    thanks, Mike

  3. Erroll Post author

    Hi Mike,

    Ah, my tomato wine! When I last looked in on it, I described it as “young, tart, and bone dry.” That was back in February. I plan to taste and test it again, neutralize some of the acid, and age it some more. So I’m not done yet, and this story may have a happy ending.

    But at this point, I can’t recommend it for general use – tinkerers and experimenters only! To them, I would say watch your acid. Consider not adding any up front then measure and adjust after the wine has fermented out. Above all, keep in touch so we can compare notes.

    Erroll

  4. gail

    Hi, i am trying to figure out TA and what the unknown numbers in the formulas mean. For instance, one formula reads as follows,
    TA(IN G/100ML)= (ml of sodium hydroxide solution)(normality
    of sodium hydroxide solution)(75)(100) divided by 1000xsample
    volume in ml.

    What on earth does the (75) mean in the equation?

    PS I love the machine you made, market it, looks much easier to use than this math…………thanks

  5. Erroll Post author

    Hi Gail,

    That’s a common formula, and it’s meant to simplify things. Really! It’s meant to be used by just plugging in your own numbers without thinking about what each term in the formula means.

    Let’s say you’re using 0.1N sodium hydroxide (the normality should be printed right on the label), and you keep adding it to a 100 ml sample of wine until you reach the endpoint of your titration. Plugging some numbers into the formula:

    TA = ( (ml sodium hydroxide) * 0.1 * 75 * 100 ) / ( 1000 * 100 )
    = ( (ml sodium hydroxide) * 750 ) / 100,000
    = (ml sodium hydroxide) * 0.0075

    I don’t remember, off the top of my head, where the 75 comes from (I learned chemistry two decades ago). If you know the normality and volume of sodium hydroxide, you should be able to determine the amount (in moles) of tartaric acid. That plus the molecular weight should get you the mass of tartaric acid. I think the 75 is the result of multiplying some of those constants together. I’m afraid I’ll just get into trouble if I try to go into more detail than that.

    The short answer is, you can use the formula literally. Just plug in your own numbers. It’s important to pay attention to your units – if it asks for ml give it ml, and remember that it’s giving you g/100 ml. So if you want g/L, multiply by 10.

    Hope this helps,
    Erroll

  6. Rich

    Eroll,
    You are a wonderful scientist, magician and storyteller! Thanks for this interesting and informative web site.

    Please explain in more detail the *process* of using the titrating device in the photo. How do you take the readings and then how do you convert the raw data into usable information?

    Thanks!

  7. Tomer1

    Wouldnt sodium bicarbonate only react with tartaric acid?
    What about fruits which mainly feature citric or malic acid?

  8. Erroll Post author

    Hi Tomer,

    An acid, any acid, is a molecule that can break into one (or more) hydrogen ion(s) and the rest of the molecule. A hydrogen ion is just a free proton, and that’s why acids are sometimes described as “proton donors.”

    When sodium bicarbonate is in a solution with an acid, the sodium (NA) combines with “the rest” to form a salt, and the bicarbonate (HCO3) combines with the hydrogen ion to form carbonic acid (H2CO3). The carbonic acid then breaks down into carbon dioxide gas (CO2 – which is what the acid testing device measures) and water (H2O).

    This works for tartaric acid, citric acid, malic acid, and any other acid. Hope this helps,

    Erroll

  9. Brian

    Any more on the TA titration contraption you posted back in 08′? I would like to know how it works and how to go about making one.
    thanks

  10. Erroll Post author

    Hi Brian,

    I started getting inconsistent results with this device. My hunch is that the seals aren’t airtight anymore, and I’ve been meaning to replace some of the parts (hoses, syringe, and maybe the bung). Haven’t gotten to that yet. It’s on the list!

    Erroll

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