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% Phosphoric = % Lactic?

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  • % Phosphoric = % Lactic?

    Hi, I have a basic question about these two acids.

    We typically use 75% Phosphoric to adjust our water pH.
    I've been fooling around with a spreadsheet dealing with water chemistry, and it has a cell for entering the amount of Lactic you use and its percentage, and I basically need to know if it will make a difference if I just pretend it says Phosphoric, and enter my info as though it does.

    So in short, acidification-wise, does 75% Phosphoric = 75% Lactic?


  • #2
    It will make a difference.

    pKa is the term you need to fool around with. It is different for every acid and phosphoric has three protons to donate.

    Here's a kind of summary link.


    Liam McKenna


    • #3
      Try asking AJ DeLange over at the forum, in the brew science section. He is quite knoweldgable in water chemistry. He is the same AJ deLange who wrote many articles about PH in early copies of Brewing Techniques magazine. Hope this helps. Cheers!!!


      • #4
        Phosphoric acid will also consume calcium, which works against it being potentially more effective than lactic acid. I second contacting A.J. deLange, or at least reading his articles at If your tolerance for chemistry isn't that high, try downloading my water treatment spreadsheet at I've tested it pretty rigorously with lactic acid and highly alkaline water, but my phosphoric calculations haven't been verified (although they're in the same ballpark as the first brewery I worked in, which treated its water with phosphoric acid). In my experience, brewery lactic acid is typically 88%.