Persistent hot break?

[Nosybear]

Attempting to predict the pH of 5 gallons of amazingly good distilled or perfectly deionized water with a TDS of zero when 1 drop of 88% Lactic Acid is added.

Knowns:
88% Lactic Acid is 11.78 Molar = 11.78 moles/L
Lactic Acid is 'effectively' monoprotic with respect to pH's below 7

False presumptions for the aid of initial simplicity:
Lactic Acid fully dissociates at pH 4-5(ish)
10 drops of 88% Lactic Acid = 1 mL
Our water is perfectly deionized

How many liters are there in one drop:
1/10 = mL = 0.1
0.1 mL/1000 = 0.0001 L

How many moles are there in one drop?
0.0001 L x 11.78 moles/L = 0.001178 moles

When this drop is added into 5 gallons of water, how many moles/L are there?
0.001178 moles / (5 Gal. x 3.7854 L/Gal.) = 0.000062239 moles/L

pH = -log(molar concentration) [for the case of monoprotic and full dissociation]

Therefore:
pH = -log(0.000062239) = 4.206 pH

However, we know that at pH 4.3 Lactic Acid is only 73.4% dissociated, so to improve upon our guess:
Actual molar H+ = 0.734 x 0.000062239 = 0.000045683 moles/L
pH = -log(0.000045683) = 4.34 pH

But we know that our RO or distilled water isn't likely to exhibit a TDS of a perfect zero, so in the real world our measured pH will be a smidge higher than 4.34 due to the buffering of some minuscule amount of remaining Alkalinity.

Call it pH 4.36 as our final guess, provided that 10 drops = 1 mL

It's usually quite a bit more than 10 drops/ml, more on the order of 20-25. Depends on the dropper. I'm an RO brewer and generally it takes about 1ml 88% lactic acid to lower my mash pH by 0.1 pH. Strictly emperical observation and no math behind it, I use the water calculator every time.

 

[Silver_Is_Money]

It's usually quite a bit more than 10 drops/ml, more on the order of 20-25. Depends on the dropper. I'm an RO brewer and generally it takes about 1ml 88% lactic acid to lower my mash pH by 0.1 pH. Strictly emperical observation and no math behind it, I use the water calculator every time.

For the case of 20 drops per mL delivered, it would take 2 drops (as opposed to 1 drop) whereby to hit ~pH 4.36 in 5 gallons when starting with fully deionized water at zero alkalinity.

It wouldn't surprise me to discover that typical RO water has on the order of 5 to perhaps as much as 15 ppm of remaining Alkalinity. I know my homes well water still has ~26 ppm Alkalinity post the RO unit, but it starts out at a whopping ~377 ppm Alkalinity from the well. Water starting at 100 ppm Alkalinity would probably be at about 5 to 7 ppm Alkalinity post an RO unit.

 

[Nosybear]

For the case of 20 drops per mL delivered, it would take 2 drops (as opposed to 1 drop) whereby to hit ~pH 4.36 in 5 gallons when starting with fully deionized water at zero alkalinity.

It wouldn't surprise me to discover that typical RO water has on the order of 5 to perhaps as much as 15 ppm of remaining Alkalinity. I know my homes well water still has ~26 ppm Alkalinity post the RO unit, but it starts out at a whopping ~377 ppm Alkalinity from the well. Water starting at 100 ppm Alkalinity would probably be at about 5 to 7 ppm Alkalinity post an RO unit.

Mine has 5 to 15 ppm TDS depending on the time of year. Most RO filters remove 90 to 95% of the ions in the source water.

 

[Silver_Is_Money]

For the case of 5 gallons of water with 10 ppm Alkalinity, along with a dropper calibrated at 20 drops per mL, it would take ~8.5 drops of 88% Lactic Acid to bring this 5 gallons of water to pH 4.36. As opposed to 2 drops for the case of fully deionized water.

Achieving 5.4 pH would require 6 drops of 88% Lactic Acid for 5 gallons of 10 ppm Alkalinity water.

 

[Nosybear]

The alkalinity of my tap water runs around 80 ppm so I should assure my RO water is around 5 ppm as CaCO3. May help my mash calcs.

 

[Silver_Is_Money]

Way back in post #17 I appear to have left people dangling as to how it was determined that at a target of pH 4.3 Lactic Acid exhibits only 73.4% dissociation (effectively liberation) of its (effectively) monoprotic H+ ion. I wish to make amends:

First the relevant 'given' stuff:
pH target = pHt = 4.3
pKa1 for Lactic Acid = 3.86 [*this, by definition, is the pH at which Lactic Acids H+ ion #1 is only 50% liberated]
Normality of 88% Lactic Acid = 11.78N
Nominal mEq/mL Acid Strength of 88% Lactic Acid = 11.78 mEq/mL [milliequivalents per milliliter]

Next the formula:
Dissociation for each 'available to be liberated' H+ ion = 1-1/(1+10^(pHt-pKax))

Now the solution:
Dissociation of H+ #1 = 1-1/(1+10^(pHt-pKa1))
Dissociation of H+ #1 = 1-1/(1+10^(4.3-3.86)) [you can copy and paste this into your computers scientific calculator]
Dissociation of H+ #1 = 0.733633702
Dissociation of H+ #1 as a percent = 0.733633702 x 100 = 73.3633702%
Dissociation as a percent, rounded = 73.4%

Target pH's effect upon 88% Lactic Acid's nominal acid strength:
11.78 mEq/mL x 0.733633702 = 8.6422 mEq/mL
(88% Lactic Acid's mEq/mL strength at pH 4.3 is reduced to 8.6422)

* follow-up:
1-1/(1+10^(3.86-3.86)) = 0.5000...

 

[Silver_Is_Money]

Lactic Acid's pKa2 = 15.10

The dissociation of this second H+ ion at a nominal mash pH of 5.4 is:
1-1/(1+10^(5.4-15.10)) = 0.000000000199526

The dissociation of the second liberatable H+ ion is essentially zero at pH 5.4. And this is why Lactic Acid can be considered to be 'effectively' monoprotic.

 

[Dornbox]

Not to hijack a thread but since we're talking about it, @Silver_Is_Money , could PH extremes cause problems with low attenuation and cloudy final brews? I have extremely soft well water, which is typical for my area, and the only beers I've had turn out clear have been pale a few farmhouse ales of low ABV and high amounts of acidulated malt. Everything else, IPAs, Blonds, Marzens etc are cloudy and refuse to clear. I've done some water modifications (gyo and calcium chloride) and use the water chem calcs page but without a PH meter (which I just ordered) I feel like I've been throwing darts at my problems. My efficiencies have been great for whatever it's worth and I have no detectable off flavors in the finished beers... And to stay on topic, I get a solid hot break and my wort runs crystal clear from my Mash Tun to Kettle... and 90 minute boils. Thanks

 

[Silver_Is_Money]

Not to hijack a thread but since we're talking about it, @Silver_Is_Money , could PH extremes cause problems with low attenuation and cloudy final brews? I have extremely soft well water, which is typical for my area, and the only beers I've had turn out clear have been pale a few farmhouse ales of low ABV and high amounts of acidulated malt. Everything else, IPAs, Blonds, Marzens etc are cloudy and refuse to clear. I've done some water modifications (gyo and calcium chloride) and use the water chem calcs page but without a PH meter (which I just ordered) I feel like I've been throwing darts at my problems. My efficiencies have been great for whatever it's worth and I have no detectable off flavors in the finished beers... And to stay on topic, I get a solid hot break and my wort runs crystal clear from my Mash Tun to Kettle... and 90 minute boils. Thanks

I'm not sure if there is correlation with your water and cloudiness. Years ago, before I researched and started monitoring and attempting to address pH and Alkalinity, I brewed with a (what was then) local artesian spring water with about 120 ppm TDS that I now know to have 32 ppm Ca++, 4.3 ppm Mg++, and 74 ppm Alkalinity, and with no compensation other than a TSP of Gypsum for my Ale's, I generally made acceptable to decent beer, including a few light lagers which received no gypsum or added acidity and still tasted decent to excellent. Given that your well water is soft (I presume as verified via a TDS meter) I have no other explanation than perhaps your yeast or hop choices playing some part. Some yeasts just refuse to floc. Have you tried adding gelatin? Do you have analyticals for your well water?

For those in N/E Ohio, this is the spring water source I brewed with in the 80's and 90's:
http://www.watercompanyamherst.com/spring-water/

Edit: Here is a link to their water analyticals:
https://www.facebook.com/CherryKnol...195166132948/2272173512801780/?type=3&theater

 

[Dornbox]

@Silver_Is_Money

All off a report and not a in house kit but:

Calcium: 10 Ca+2
Magnesium: 3 Mg+2
Sodium: 7 Na+
Chloride: 11 Cl-
Sulfate: ( unknown but very low in the state, probably single digit ) SO4-2
Alkalinity: 40
pH: 7.9

Yeast have been varied as have been hops other than Citra to one degree or another.

 

[Ward Chillington]

The waters initial pH of 6.5 is actually of little (to approaching no) import or significance. Alkalinity combined with mineralization is the name of the game. At pH 6.5 you might have appreciable Alkalinity. Do you know the ppm Alkalinity of your mash and sparge waters, as well as the mash waters ppm Calcium and ppm Magnesium? NO

What is the grain bill, and what is the mash water volume? 9 # Two Row Pils, 12 oz Black, 8 oz Carapils 10# 2 oz mashed at 2 quarts per pound

Did you properly acidify your sparge water to pH 5.4-5.6 to reduce its Alkalinity? No need to, I didn't fiddle with the water at all.

Was any Baking Soda or acid added to the mash water, or the mash directly, and if so, how much?

Thanks never the less and at this stage I'm in the land of RDWHAHB !

 

[GFHomebrew]

Lactic Acid's pKa2 = 15.10

The dissociation of this second H+ ion at a nominal mash pH of 5.4 is:
1-1/(1+10^(5.4-15.10)) = 0.000000000199526

The dissociation of the second liberatable H+ ion is essentially zero at pH 5.4. And this is why Lactic Acid can be considered to be 'effectively' monoprotic.

My wife just got A High Destinction in her chemistry studies at University here I showed her this post this morning thinking she might follow what's being put down here. Yup she responded yup I get what he's saying.
Me confused. man my missus knows more about water chemistry than I do and she's never brewed a beer.

I love where beer can take you in life...

 

[Silver_Is_Money]

Phosphoric Acid (H3PO4) is triprotic, and at 85% concentration its Normality is 43.95 (which reflects a Molarity of 14.65 times a valence of +3 due to the three H's). Thus its full dissociation mEq/mL acid strength is 43.95 mEq/mL. But strangely it acts much weaker than 43.95 mEq/mL at a nominal mash pH of 5.4. This is due to the dissociation/liberation behavior (the pKa's) of its three H+ ions.

Phosphoric Acids 3 pKa's are:
pKa1 = 2.16
pKa2 = 7.21
pKa3 = 12.32

pH 5.4 fractional dissociations:
First H+ ion = 1-1/(1+10^(5.4-2.16)) = 0.999424891
Second H+ ion = 1-1/(1+10^(5.4-7.21)) = 0.015251942
Third H+ ion = 1-1/(1+10^(5.4-12.32)) = 0.00000012

The three H+ dissociations at pH 5.4 sum to 1.014676953, so the acid strength exhibited at pH 5.4 is:
1.014676953/3 = 0.338225651
0.338225651 x 43.95 mEq/mL potential = 14.865 mEq/mL actual

85% Phosphoric Acid's effective acid strength at 5.4 pH is 14.865 mEq/mL. A tad more than as if it was monoprotic.

 

[Silver_Is_Money]

You can think of Phosphoric Acid's triprotic dissociation this way: After the first H+ ion (or proton) has been liberated the remaining H2PO4- ion has become negatively charged, and since opposite charges attract, the remaining two positively charged H's are held much more tightly. And after the 2nd H+ has (with great effort) been dissociated, the remaining ion is even more negatively charged, meaning that dissociating the 3rd and last H+ will be far more difficult.

 

[Silver_Is_Money]

A practical application of the knowledge that at pH 5.4 Phosphoric Acid at 85% has an acid strength of 14.865 mEq/mL:

Let's say we have 5 gallons of sparge water with 80 ppm (mg/L) Alkalinity (as CaCO3) and we want to acidify it to a pH of 5.4. How much 85% Phosphoric Acid should we add?

The Molecular weight of CaCo3 is 100.0869 grams/Mole. Ca++ has a charge of plus 2. Therefore the Equivalent Weight of CaCo3 is 100.0869/2 = 50.04345 grams/Eq = 50.04345 mg/mEq

80 mg/L Alkalinity / 50.04345 mg/mEq = 1.5986 mEq/L Alkalinity

5 Gallons x 3.7854 L/Gal. = 18.927 Liters

18.927L x 1.5986 mEq/L = 30.2567 mEq of Alkalinity (overall)

30.2567 mEq Alkalinity / 14.865 mEq/mL Acid = 2.04 mL Acid

Thus 2.04 mL of 85% Phosphoric Acid is required to "completely" eradicate the Alkalinity and reduce it to zero.

But that results in a problem. Per a carbonate species chart, when Alkalinity (as HCO3-, or bicarbonate) is zero, the pH is ~4.3, and we have only been asked to add enough acid to hit a pH of 5.4

It turns out (also from the carbonate species chart) that if we add only ~90% of 2.04 mL we will hit a pH of ~5.4, thus:
2.04 mL x 0.90 = 1.84 mL

Final Answer: Add 1.84 mL of 85% Phosphoric Acid to 5 gallons of 80 ppm Alkalinity water to acidify it to ~pH 5.4

Carbonate Species chart: