Calculating acid when adjusting boil pH.

[ajdelange]

6 gallons x 3.7854 ~= 22.7 Liters
Moles of hydronium ions present (per Liter) for the initial post boil pH 5.3 wort = 10^-5.3 = 0.000005012
Moles of hydronium ions desired (per Liter) when at the target of pH 5.0 = 10^-5.0 = 0.00001

Moles of current Hydronium ion deficiency post boil (per Liter) = 0.00001 - 0.000005012 = 0.000004988
22.7 Liters x 0.000004988 moles/Liter deficiency = 0.000113228 moles of overall H+ deficiency

It seems to me that the goal is to supply sufficient acid to cover this overall amount of moles of H+ deficiency in order to move the wort from 5.3 pH to 5.0 pH

As has been explained to you dozens of times before acid requirement can be calculated from the difference in hydrogen ion concentrations as determined from the pH's ONLY when the solution has 0 buffering capacity. This is never true in aqueous solutions and is, therefore, not the case with wort. To determine how much acid is needed one must effectively titrate a sample of the wort between the initial pH and the desired pH as was explained earlier in this thread.

 

[Silver_Is_Money]

AJ, when Kolbach determined that nominally 0.29 grams of 88% lactic acid will move 1 Kg by 0.1 pH, what mash efficiency was he presuming, and does ones efficiency during the mash thereby matter?

I.E., if for a pH target of 5.1 we can derive that 10*290*0.948/90.8 = 30.278 and therefore the protons required to move a wort made with 1 kg of malt by 1 full pH unit = 30.278 mEq/kg•pH for the case of targeting 5.1 pH, does this mEq/kg•pH value have any relationship which correlates to ones nominal mash efficiency, such that if Kolbach's mash efficiency was nominally 85% when he initially derived this association and my mash efficiency is only nominally 73%, when using 30.278 mEq/kg•pH should this for my case be multiplied by 73%/85% and thereby be corrected to ~26 mEq/kg•pH?

Short version: Rather than using ones starting Kg's of grist, would it perhaps be better to somehow incorporate post boil and cooling specific gravity whereby to determine the worts presumed buffering capacity more precisely, and then from there determine the mL's of 88% lactic acid required to move the wort from its currently measured post boil and cooling pH to a post boil and cooling target of 5.1 pH?

And if there is any such mash efficiency correlation to buffering, would it not determine the buffering capacity characteristics of ones grist during the mash as well as for post mash?

 

[ajdelange]

AJ, when Kolbach determined that nominally 0.29 grams of 88% lactic acid will move 1 Kg by 0.1 pH, what mash efficiency was he presuming, and does ones efficiency during the mash thereby matter?

I may be having a senior moment here but I don't remember any conclusion like that from Kolbach. He noted in his "Enfluß.." paper that reduction of the alkalinity of the water (I assume that means mash and sparge) by a certain amount would result in a drop in knockout pH of a certain amount. Not reference was made in that paper to the nature of the mash itself. Given where he worked I assume this observation was made for typical German lagers.

And if there is any such mash efficiency correlation to buffering, would it not determine the buffering capacity characteristics of ones grist during the mash as well as for post mash?

I would assume that there is a correlation between mash efficiency and wort buffering but have no idea as to how strong it would be. It seems to me the best way to acidify wort is to do what Kunze recommends, i.e. measure the buffering of the wort (very easy to do) in ml/pH•Lactic acid and compute the lactic acid required for the adjustment accordingly.

 

[Silver_Is_Money]

I may be having a senior moment here but I don't remember any conclusion like that form Kolbach.

It came from post #2 in this thread.

I agree that the best way is to measure it, but few to none will be doing that.

 

[ajdelange]

Ah. You are attributing my interpretation of what Kolbach observed to Kolbach. As I said in the last post he found that a reduction of liquor alkalinity by a certain amount reduced knockout pH by a certain amount. At an assumed pH and assumed beer size it is easy enough to compute the amount of lactic acid required to remove a mEq of alkalinity. The qestion you should have asked is what efficiency, pH and water to grist ratio I assumed in coming up with the 0.29 number. This was Feb 2016 and as I can barely remember what I was up to in Feb of 2019 I'm afraid I have no idea as to what I assumed then. Fair assumptions would be those associated with nominal German Lager brewing. I should, of course, have been clearer.

 

[Silver_Is_Money]

Ah. You are attributing my interpretation of what Kolbach observed to Kolbach. As I said in the last post he found that a reduction of liquor alkalinity by a certain amount reduced knockout pH by a certain amount. At an assumed pH and assumed beer size it is easy enough to compute the amount of lactic acid required to remove a mEq of alkalinity. The question you should have asked is what efficiency, pH and water to grist ratio I assumed in coming up with the 0.29 number. This was Feb 2016 and as I can barely remember what I was up to in Feb of 2019 I'm afraid I have no idea as to what I assumed then. Fair assumptions would be those associated with nominal German Lager brewing. I should, of course, have been clearer.

Got it! Perhaps the next great move forward in precision for mash pH assistant software will be to incorporate a nominal mash efficiency percentage, or perhaps an anticipated end of the mash OG for the wort (pre-sparge). I've been thinking along the lines that if two people start with the same weight of (for example) Pilsner malt of the same brand and lot #, the same volume and mineralization level of initially identical mash water, etc..., but one of the two gets 85% as to mash efficiency and the other gets only 65%, the (for this example, basic with respect to a nominal mash pH target of 5.2 to 5.6) mEq's/L of acidity of the wort for the high efficiency mash might measure noticeably greater than that for the case of the well lower efficiency mash, simply because the mash water will have permeated into far more of the hidden confines of the grist for the case of high mash efficiency.

 

[Silver_Is_Money]

Short version: From a specific gravity reading one can back calculate to an "effective" grist weight, rather than the actual grist weight. And perhaps the case may be that the effective grist weight of a wort has greater correlation to buffering capacity than does actual grist weight.

 

[Silver_Is_Money]

There may even be a means whereby to link this new line of thinking into D. Mark Riffe's recent comment regarding his proposal of a buffer multiplier that reduces buffering by an initially estimated factor of 0.6X. Perhaps instead of being a fixed 0.6X, this multiplicative factor can be linked to a degree of variability which is associated with mash efficiency. The ideal case would be that his proposed multiplicative factor is one and the same as ones mash efficiency.

 

[Big Monk]

There may even be a means whereby to link this new line of thinking into D. Mark Riffe's recent comment regarding his proposal of a buffer multiplier that reduces buffering by an initially estimated factor of 0.6X. Perhaps instead of being a fixed 0.6X, this multiplicative factor can be linked to a degree of variability which is associated with mash efficiency. The ideal case would be that his proposed multiplicative factor is one and the same as ones mash efficiency.

You wouldn’t want to use Mash Efficiency. You’d want to use conversion Efficiency

You would find actual extract weight in kg and divide that by maximum extract weight in kg and maybe use that?

I’m not 100% how effective that would be. You need to be sure to apply this “Efficiency Factor” to the proper malt characteristic.

That’s if it’s even a valid concern.

 

[Silver_Is_Money]

You wouldn’t want to use Mash Efficiency. You’d want to use conversion Efficiency

You would find actual extract weight in kg and divide that by maximum extract weight in kg and maybe use that?

I’m not 100% how effective that would be. You need to be sure to apply this “Efficiency Factor” to the proper malt characteristic.

That’s if it’s even a valid concern.

Perhaps I'm confusing or conflating the two.

Could this be looked at from the simple perspective of "points", whereby if a grist has a maximum potential of 35.5 points per pound per gallon, and one computes via SG that one achieved 27 points, the factor would thus become (for this example) 27/35.5 = 0.76? Or alternately as the grists aggregate fine grind potential derived SG vs. actually measured SG?

I believe the metric equivalent to points per pound per gallon is termed as "Liter Degrees Per Killogram".

 

[Big Monk]

Perhaps I'm confusing or conflating the two.

Could this be looked at from the simple perspective of "points", whereby if a grist has a maximum potential of 35.5 points per pound per gallon, and one computes via SG that one achieved 27 points, the factor would thus become (for this example) 27/35.5 = 0.76? Or alternately as the grists aggregate fine grind potential derived SG vs. actually measured SG?

I believe the metric equivalent to points per pound per gallon is termed as "Liter Degrees Per Killogram".

Conversion Efficiency is how well you extracted an amount of first wort extract compared to the maximum amount. This will be based around total grain, extract potential (Fine or Coarse As Is) of the mash, and water to grist ratio.

Mash Efficiency is a measure of your achieved preboil mash extract (without sugar adjuncts) that takes into account Lauter Efficiency.

The former is what matters for pH estimation of the mash. If it matters at all.

 

[SanPancho]

Anybody have strength/normality of 75% phosphoric?

 

[Silver_Is_Money]

Anybody have strength/normality of 75% phosphoric?

It varies with target pH. What target pH do you want it for?

 

[Silver_Is_Money]

Anybody have strength/normality of 75% phosphoric?

In the end it's acid strength is not as highly variable as for weaker acids.

5.0 pH : 12.141 mEq/mL
5.1 pH : 12.164 mEq/mL
5.2 pH : 12.191 mEq/mL
5.3 pH : 12.223 mEq/mL
5.4 pH : 12.262 mEq/mL
5.5 pH : 12.310 mEq/mL
5.6 pH : 12.370 mEq/mL
5.7 pH : 12.444 mEq/mL
5.8 pH : 12.535 mEq/mL

 

[SanPancho]

5.4 generally in mash, although we also use for late kettle adjustments, fermenter, etc.

i need to know numbers for each? Maybe An average?

 

[Silver_Is_Money]

5.4 generally in mash, although we also use for late kettle adjustments, fermenter, etc.

i need to know numbers for each? Maybe An average?

In order to know where you are going, you first need to know where you are. It seems as if you could use both mash and kettle pH managing software. Or alternately use:

(Initial_pH_Grist/Wort - Target_pH_Wort) = mEq's required/(34 x Kg_Grist)

Solve for mEq's Required. Then apply the acid (or base) strength appropriate to your target pH.

Example for 50 mEq's required to hit a target of 5.4 pH:

50 mEq / 12.262 mEq/mL = 4.08 mL of 75% Phosphoric Acid to be added.

If you can derive "Initial_pH_Grist/Wort" the rest is easy. No software required.

 

[SanPancho]

Already have mash calc. So realistically this is more for kettle and ferm i guess. The kolbach equation works well enough for us. Typically within.1 of target. But our phosphoric just went down to 75 from 85. Hence the need for new figure to plug into the spreadsheet.