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  • Acid, titration, depth/out of

    Oh chums!

    Why have you even opened this thread? Just to mock the totally ignorant, or to be altruistic and try and tell me what Bertie Tanner (chemistry teacher) failed in? Well this is the question I'm looking at:

    I'm using a Ritchie acid testing kit. I want to find the %acid in my sample. The wrinkle is I'm looking at acetic acid (mainly) in cider vinegar. Because I'm expecting 5-10% acid by volume, I cut the sample by 1/10th to use 0.5ml of the target liquid (vinegar) - I use a 1ml plastic syringe, so pretty accurate. Into the test tube, an inch of water, 3 drops of indicator, then drop in the peroxide. Exactly 5ml and it goes the wispiest of pinks and stays pink no matter how much I shake it.

    So 5% acid, eh? QED...

    Or is it?

    That's my problem, somewhere I think it says the measure is based on sulphuric acid - so is there the equivalent of 5% sulphuric but a different % acetic? Somewhere I found a table that looked like acetic was 60% strength of sulphuric: does that mean I've got an 8% acetic acid by volume?
    Now bottling 20DJs of 2013 red and making room to rack 5 carboys of 2014 red to the DJs where they can wait for another winter.
    Thank goodness for eBay! (local cache of DJs)

  • #2
    do you have PH meter ?
    Gluten free, caffeine free, dairy free, fat free – you gotta love this red wine diet!

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    • #3
      Thanks Brian, messing in GooG to respond to your idea gave the answer!

      Originally posted by Cellar_Rat View Post
      do you have PH meter ?
      Hi Brian, I've got litmus paper, but I am labouring under the understanding that pH and TA are different. a pH of 3 for example doesn't have an equivalence to a % of acid. Am I wrong? Does your pH meter give a % reading as an alternative? If so I'll be getting one pronto!

      Why am I interested, well there are guides for how strong your vinegar should be to make it safe for pickling "things". Now it's possibly not so troublesome when you pickle shallots - but I like pickling herrings (happy to share a recipe/process if anyone's interested) and I'd like to start with 6% vinegar (some recipes say 10%) but the US FDA says (reportedly) 4.6% is needed to prevent botulism.

      So 4.6% is a measure of concentration, I think it means 4.6% of the whole mixture is acetic acid.

      pH, I guess, is a measure of strength. I say "I guess" because the back of my neck goes cold and my diaphragm scrunches when I read that it's a logarithm of the concentration of free protons, expressed with a positive sign. I think the idea is that acetic acid is a weak acid (like citric and tartaric) but sulphuric and hydrochloric are strong acids. So, I reason without any confidence, a lot of acetic acid in a solution will have the same pH as a smaller amount of sulphuric.

      That brings me back to the titration question - if the titration answer is "5%"... I think Bob said in one of his lessons somewhere that in UK titration kits that's "5% equivalent sulphuric acid" and there's some conversion to get the % acetic (or tartaric, etc). There's another problem - allegedly titration consistently under-measures the real acid content

      Of course it's not just the pickling strength - I'm interested in flavour, economy and plain curiosity. If I was making 8% vinegar, which I suspect, I could cut that with water to knock it back to 6% and make it go further or just achieve consistent results (herring in very strong vinegar goes creamy/mushy which is less attractive to me).

      Oh wow! I found it! http://www.wine-consultants.com/down...lculations.pdf AND I found some of Bob's writing saying Richies is based on sulphuric: http://www.winesathome.co.uk/forum/s...estion-of-acid... it always comes down to putting the right phrase into Google - I've done a very similar search about 50 times!

      So, I divide my 5% (Sulphuric) by 0.82 to get 6% (Acetic) ... assuming there's not much tartaric in cider... and 6% is where I want to be!
      Now bottling 20DJs of 2013 red and making room to rack 5 carboys of 2014 red to the DJs where they can wait for another winter.
      Thank goodness for eBay! (local cache of DJs)

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