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We currently do some pH adjustments of jams (target pH of 3.2) using citric acid, however, when there is a large difference between the starting pH and the target pH this can be quite a time consuming process (add to vessel, mix, take sample, repeat).

It's been a long time since I've done chemistry, but I believe that because the pKa of the citric acid is close to the target pH and the jams are a complex mix of buffering agents that it isn't easy to come up with a simple formula for the amount to add (in fact, I observe, even at a similar starting pH, the amount of citric acid required varies a lot).

My idea was to titrate citric acid into a sample of jam that has been diluted with distilled water for easier mixing:

  • Jam @ 50% dilution
  • Citric Acid dissolved at a ratio of 1:9 in distilled water

My thought is that if I keep taking samples and titrating the citric acid with the diluted Jam that I will get a nice correlation between the titration amount and the amount of citric acid required to add to the batch.

My question is:

  • Will this produce a nice correlation?
  • Is it possible to do this theoretically?

Thanks,

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You can do this at any dilution of both titrate and titrant, as long as you "keep the books" up to date when calculating the results you should be fine. I would probably only dilute the titrate though, unless you have good reasons. (If the dilution of jam is to make it less viscous then that is a good reason for doing it)

Whenever I needed to perform titration something of unknown pH and contents (and I had a large supply of the solutions) I would do a low resolution "sweep" with high concentrates and low tech (old school burettes are usually the fastest, valve fully open and stirring at... vigorous). I'd do two or three of those, just to pinpoint the area of interest. (Sometimes there are several, but then you just do the below for all of them). Assuming one specific point of interest was at 100% addition of titrate, I would add 80% of the titrant to a sample of titrate, then do another titration at 10x dilution of titrant. Three fast samples. Repeat the above, and now at 100x dilution i'd put it in the autotitrator and get some graphs.

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