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combining lactic phosphoric acid mix

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CraigR

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i am just getting into water chemistry - as i have always tended to brew darker beers and it was only when i had less success with lighter brews that I realised I needed to do more.
I have very high bicarbonate levels ~347ppm and total alkalinity of 285.

Using the brun'water calculator, adding either lactic (only) or phosphoric (only) gives me a warning that I may be over the taste threshold. (although I have read reports that the level of phosphoric could reasonably be higher).

With a bit of mixing and dilution, I could easily make an acid mix additive of say 1:1 lactic : phosphoric acids at (for example) an overall concentration of 20% to make measurement easier, which when added to my mash/sparge is giving a ppm addition in the low 200s for each acid and is expected to be below the taste threshold.

Does this seem like a good approach, I am presuming that the acid mix is stable enough to leave on the shelf for a while.
 

Silver_Is_Money

Larry Sayre, Developer of 'Mash Made Easy'
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I would not mix the acids. If I was going to mix them, I would independently determine the required addition quantity for each acid when used by itself, and then separately add half of each.

I was unaware that there is a taste threshold for phosphoric acid. It is generally presumed to be quite flavor neutral.
 
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CraigR

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You could also dilute your high bicarbonate source water 50/50 with RO water to reduce the bicarbonate.
thanks for your input.
RO water doesn’t seem to be as available in the UK as in USA, however I think will stick with the acid additions anyway, as apart from my high bicarbonate, my other mineral levels are pretty much where I want them, so no need for further adjustment
 
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CraigR

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I would not mix the acids. If I was going to mix them, I would independently determine the required addition quantity for each acid when used by itself, and then separately add half of each.

I was unaware that there is a taste threshold for phosphoric acid. It is generally presumed to be quite flavor neutral.
 
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CraigR

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Thanks, I will keep my acids separate.
For ease of measurement I have diluted each down to 10% before making my wort/sparge additions and just readjusted in my brunwater calculations.

it was brunwater spreadsheet which suggests phosphoric acid levels may be above flavour threshold if used exclusively- but I just made a brew with a mix of the two- it’s currently undergoing fermetation, so we’ll see how it goes
 

CascadesBrewer

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Using the brun'water calculator, adding either lactic (only) or phosphoric (only) gives me a warning that I may be over the taste threshold. (although I have read reports that the level of phosphoric could reasonably be higher).
I am curious about how much Phosphoric is it recommending you add? I am often adding around 30 ml of 10% and I don't notice any off flavors...but your bicarbonate and alkalinity values are much higher than mine.
 

Silver_Is_Money

Larry Sayre, Developer of 'Mash Made Easy'
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If we take the mEq/mL of 10% Phosphoric Acid to be ~1.074, then for the case of the OP's 285 ppm alkalinity, a volume of 25L of water to be treated, and a target of ~5.4 pH, the acid quantity requirement is:

285/50 x 25L = 142.5 mEq of alkalinity to be totally eliminated by acid (which means taking it to pH 4.3 with acid).

142.5 mEq/1.074 mEq/mL = 132.7 mL of 10% Phosphoric Acid to hit pH 4.3

To hit ~5.4 pH the acid addition required is ~90% of this, so:

132.7 x 0.90 = 119.4 mL of 10% Phosphoric Acid to hit ~ pH 5.4 for the case of 25 Liters of 285 ppm alkalinity water
 

Silver_Is_Money

Larry Sayre, Developer of 'Mash Made Easy'
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This chart expresses that to remove 100% of present alkalinity (this time expressed as bicarbonate, or HCO3-) requires hitting 4.3 pH. And also (via a bit of extrapolation along the Y axis which is scaled from 0 to 1) that to hit ballpark 5.4-5.5 pH requires about 90% of whatever acid is required to hit 4.3 pH.

 

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Larry Sayre, Developer of 'Mash Made Easy'
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One of the negatives of trying to mix two acids is that when chemicals are combined 500 mL of one plus 500 mL of another does not necessarily always result in 1,000 mL of the combined chemicals. There are even some rare cases whereby mixing equal amounts of two chemical solutions results in less volume than either one started with initially.
 
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