Acid Lactic 88% strength doesn't seem to be right in EZ calculator

[meaulnes2]

Hi,

I am trying to use the EZ water calculator that seems very easy to use.
Nevertheless, there is one point I do not understand very well.
It is the quantity of acid that is used to lower the alkalinity with Lactic acid 88%.

Suppose I fix the mash water to 10 l.
Filling the cell, J37, I can see that, at a mash PH target equal to 5.4, a quantity of 1ml of Lactic acid 88% lowers the alkalinity by 117 ppm as CaCO3.
117 ppm as CaCO3 is also 117/50 mEq/l= 2.34 mEq/l
This also means that 1ml of Lactic acid 88% supplies 23.4 mEq. Consequently the strength of this acid is (a) 23.4 mEq/ml.

Other sources make me think that the actual strength of Lactic acid 88 at PH 5.4 is roughly (b) 11.45 mEq/ml.

I can read in Palmer's book "How to Brew" on page 346 that we need 1ml of 1N solution to reduce the alcalinity of one liter by 50 pph i.e. 1mEq/l.
On the following page I read that we need 84.7 ml of Lactic acid 88% to prepare one liter of 1N solution.
Consequently, 0.0847 ml of Lactic acid 88% lowers the alkalinity of one liter by 1 mEq/l
In other terms, the strength of this acid is (c) 1/0.0847= 11.8 mEq/ml

Value (b) is calculated according to this post i.e. it is calculated at a PH of 5.4.
Value (c) is more general and doesn't provide a PH value

The fact is that (b) and (c) values are both roughly twice the value of (a)

At the bottom of the calculator the author indicated is TH from this site.
Could TH, or anybody else, explain me why in the formula that calculates the acid contribution there is explicitly of factor of 2 that is used ?
I confess I am not a chemist but I like to understand what I am doing and what is under the hood of the tools I use.

 

[Silver_Is_Money]

Alkalinity (as CaCO3) does not live in a vacuum. For every 2.34 mEq/L of Anion CO3-- there must also be present within the water 2.34 mEq/L of Cation Ca++. Water is charge neutral.

 

[Silver_Is_Money]

Calcium MW = 40.078 grams/Mole

Calcium EQW = 40.078/2 = 20.039 grams/EQ = 20.039 mg/mEq

2.34 mEq/L x 20.039 mg/meq = 46.89 mg/L of Calcium cation.

See what happens when your 10 liters of 117 ppm Alkalinity (as CaCO3) water also contains 46.89 ppm of Calcium.

 

[meaulnes2]

Thank you very much for you help. Chemistry has always been some sort of brain teaser to me. Could you please be more explicit and make me understand how this 3 assertions match one an other? I must confess I cannot see this clearly.
Palmer says 0.0847 ml of 88% lactic acid lowers alkalinity of 1 liter by 50 ppm as CaCO3
That is also 1ml lowers 1 liter by 50/0.0847=590 ppm as CaCO3
EZ calculator when adding 1ml of 88% lactic acid lowers the alkalinity of 10 liters by 117 ppm as CaCO3
0.1 ml of of 88% lactic acid in lowers the alkalinity of 1 liter by 117 ppm as CaCO3
1ml of of 88% lactic acid in lowers the alkalinity of 1 liter by 1170 ppm as CaCO3
This troubles me a lot.

 

[Silver_Is_Money]

EZ Water does not appear to have been upgraded in a good number of years now. I have no idea as to what makes it tick, but if RA is involved, be mindful that RA is a secondary and merely man made derivative construct that has been seriously debunked within roughly the past 7 years by Chemists Barth and Zaman. The work of Kolbach in which RA is rooted does not pan out (lead one to his derived divisor constants for Ca++ and Mg++) when actually put to the test, albeit that for many decades it seems as if no one thought to attempt to repeat his work, but rather everyone accepted it as self evident truth. The "constants" turn out to be wildly variable as to value. In short, RA is a wildly moving target which can not be assessed without knowing some specifics about the malts (and adjuncts) involved in making up the grist. And as a consequence Mash pH generally does not fall as much as Kolbach (or to be more correct, those who misinterpreted Kolbach) presumed when Calcium is introduced into the mash water. AJ deLange once ballparked the pH drop within the mash at about 1/2 of what Kolbach predicts, and Barth and Zaman say loosely 1/2 to 1/4 as much drop, but grist component dependent.

But to be fair to Kolbach, he measured mineral induced pH drop post boil and cooling (at knockout), and not within the mash at all, so it only makes sense that the pH drop observed within the mash proper will be less. It is mainly a decades running misinterpretation of Kolbach which moves his results into the mash (incorrectly) that allowed for... (well, you get the picture, mash pH prediction gobbledygook).

As an aside, it has been stated (or at least highly suspected) that roughly 70-80% of critical medicinal/drug studies with high statistical confidence can (and/or will) not be independently verified to within any level of statistical confidence when actually repeated.

 

[Silver_Is_Money]

Chemical Reactions occur on an mEq to mEq equivalence basis (nominally, for dissociation constants set aside).

Assume 117 mg/L (~117 ppm) Alkalinity (as CaCO3)

117 mg/L / 50.04345 mg/mEq = 2.338 mEq/L Alkalinity (as CaCO3)

2.338 mEq/L x 10L = 23.38 mEq of Alkalinity (as CaCO3)

At pH 5.4 the mEq/mL acid strength of 88% Lactic Acid is 11.4515 (with dissociation factored in here).

23.38 mEq / 11.4515 mEq/mL = 2.0417 mL of 88% Lactic Acid required to bring the pH to ~4.3, which would effectively reduce Alkalinity to Zero.

However, only roughly 90% of 2.0417 mL is required whereby to achieve a pH of ~5.4, because Alkalinity is not Zero mg/L at pH 5.4 (see attachments).

2.0417 mL x 0.90 = 1.84 mL

The final answer is that 1.84 mL of 88% Lactic Acid should bring 10 Liters of 117 mg/L Alkalinity (as CaCO3) water to a nominal pH of around 5.4.

 

[Silver_Is_Money]

Notice that RA does not enter into any of this.

 

[meaulnes2]

OK thank you. you seem to be an expert. I feel I am starting to understand. But not being a chemist I probably need to open some good books to make my understanding better. I should have paid more attention to chemistry at school but at that time it was rather my pet peeve and I wasn't brewing yet.
I will have a look at your Mash Made Easy as I discover it now. Probably I will come back here for more help.

 

[Silver_Is_Money]

Thanks for the complement, but I certainly wouldn't label myself as being an "expert". Perhaps more like 'Above Average'.

 

[Silver_Is_Money]

There is a minor (and fully inconsequential with regard to targeting pH 5.4) mistruth within my post #6 above.

Due to it's poor dissociation at pH 4.3 (which is a consequence of pH 4.3 approaching Lactic Acids pKa1 value of 3.86) 88% Lactic Acid only exhibits an acid Strength of 8.644 mEq/mL at pH 4.3, so to actually achieve pH 4.3 for the 10L of 117 mg/L Alkalinity water being discussed, whereby to fully reduce its Alkalinity to zero) one must add 2.70 mL of this acid.

23.38 mEq ÷ 8.644 mEq/mL = 2.70 mL of 88% Lactic Acid (as opposed to 2.0417 mL)

Trivia: Any fully 'monoprotic' acid is reduced to half of its 'nominal' acid strength when targeting a pH identical to its pKa.

Trivia 2: Lactic Acid is very close to being fully monoprotic, but isn't quite monoprotic due to its pKa2 being at a very high value of 15.1. And when targeting pH 3.86 (pKa1) it exhibits an acid strength of 5.891 mEq/mL. 2 x 5.891 = 11.782 mEq/mL (with this likely being why your value derived from Palmer data as seen above in post #1 to this thread computes the acid strength of 88% LA at 11.8 mEq/mL).

Trivia #3: Many seem to be of the belief that Alkalinity is zero mg/L (ppm) when at pH's in the vicinity of pH 5.4, but this is not the case. See the charts I attached within post #6 above. Somewhere around pH 3.7-4.0 is required whereby to truly eliminate HCO3- derived Alkalinity (Bicarbonate ion, which pretty much sums up the source of Alkalinity, despite some odd decision from the past of correlating it to CaCO3).

Trivia #4: Others seem to believe Alkalinity is truly zero when your water is at pH 4.3, but this is only because titrations before there were any extant pH meters were done with color changing 'indicators', and the Methyl Orange indicator used (from memory here) whereby to proclaim zero Alkalinity, changes color at a nominal pH 4.3. For all practical purposes 4.3 pH is acceptable for 'zero' Alkalinity, but not quite factually correct...

 

[meaulnes2]

Largely above average. Thank you for this very detailed complement. It incites me to deepen my knowledge in chemistry.