A beginners guide to adding Baking Soda to mash water to raise its alkalinity

[Silver_Is_Money]

For our example, let's assume the following:
-------------------------------------------------
Our desired final target for mash water alkalinity = 100 ppm (or 100 mg/L)
Our initial mash water alkalinity = 30 ppm
Our volume of mash water to be raised to 100 ppm alkalinity = 5 gallons

Molecular Weight of Baking Soda = 84
Molecular Weight of Sodium = 23
Molecular weight of CaCO3 = 100
Normality of CaCO3 = 2
Normal weight of CaCO3 = 100/2 = 50
ppm = mg/L
1 Gal. = 3.7854 L

Procedure:
------------
Step 1) 100 ppm final alkalinity - 30 ppm initial alkalinity = 70 ppm of alkalinity to be added

Step 2) 5 Gal. mash water x 3.7854 Gal./L = 18.927 Liters of mash water to be treated

Step 3) 70 ppm x 84/50 x 18.927 L / 1,000 = 2.226 grams Baking Soda (rounded)

Our answer = add 2.226 grams of baking soda (or 2,226 mg) to achieve 100 ppm of alkalinity


Bonus stuff below this line:
------------------------------

What is the resulting (additional) ppm of sodium?
(2.226 g x 1000) x 23/84 / 18.927 L = 32.2 mg/L (ppm) sodium [additional to source water sodium]

 

[ajdelange]

You are assuming that the "normality" of bicarbonate us 1 mEq/mmol. That is only true at very low pH. Here are the normalities at some more typical mash pH's
5.2 0.938
5.4 0.905
5.6 0.858

 

[Big Monk]

You are assuming that the "normality" of bicarbonate us 1 mEq/mmol. That is only true at very low pH. Here are the normalities at some more typical mash pH's
5.2 0.938
5.4 0.905
5.6 0.858

This is obviously defty handled, in part, by the QAcid function in A.J.'s Brewing Functions sheet:

HCO3 Normality (mEQ/mmol) = 1 + QAcid ( pHz , 6.351 , 10.329 )

 

[ajdelange]

And even more deftly by

HCO3 Normality (mEQ/mmol) = 1 + Qcarb ( pHz )

which calls Qacid and supplies the pK's for carbonic. Saves a little typing (and having to remember pK's).

 

[Big Monk]

And even more deftly by

HCO3 Normality (mEQ/mmol) = 1 + Qcarb ( pHz )

which calls Qacid and supplies the pK's for carbonic. Saves a little typing (and having to remember pK's).

Very true.

 

[RPh_Guy]

I missed the part where this is a "beginners guide".

I use RO water and I put roasted grain in the mash, so I use however much sodium bicarb the silly little calculator says I need to hit mash pH.

 

[Big Monk]

I missed the part where this is a "beginners guide".

I use RO water and I put roasted grain in the mash, so I use however much sodium bicarb the silly little calculator says I need to hit mash pH.

I understand what Silver is trying to do, but “beginner” typically doesn’t apply to hand calculated water equations.

 

[Silver_Is_Money]

You are assuming that the "normality" of bicarbonate us 1 mEq/mmol. That is only true at very low pH. Here are the normalities at some more typical mash pH's
5.2 0.938
5.4 0.905
5.6 0.858

If I'm reading this correctly, for a mash target of pH 5.4 one would need to divide the beginners formula by 0.905 and add a bit more sodium bicarbonate thereby. Etc... But that adds a level of complexity that begins to remove this from the reach of the beginner. And it's likely better to err a bit on the low side for such additions, rather than on the high side.

 

[Big Monk]

If I'm reading this correctly, for a mash target of pH 5.4 one would need to divide the beginners formula by 0.905 and add a bit more sodium bicarbonate thereby. Etc... Btu that adds a level of complexity that begins to remove this from the reach of the beginner. And it's likely better to err a bit on the low side for such additions, rather than on the high side.

So how did I arrive at a low prediction that requires Baling Soda?

I’d wager no beginner is doing this by hand. So is this an explanation of theory behind spreadsheets? And if so, whose?

 

[Silver_Is_Money]

It is basic chemistry. It is simple enough to do by hand. Anyone with high school level chemistry should understand it, and even without high school chemistry it is quite easy to follow. I did preface it with it being beginner level. Why do we have a brewing science forum if it is intentionally being manipulated to keep it out of the hands of beginners and/or those trying to understand, but coming at this without doctorates? I don't see anyone else trying to help beginners with the rudimentary mathematics and chemistry on this forum, so I simply picked up the ball and started to run with it.

The alternative seems to be merely parroting existing and publicly available formulas, rather than attempting to understand this from a simplistic chemistry approach. Anyone can be a formula scarfing parrot. Some may even charge for it.

 

[Big Monk]

It is basic chemistry. It is simple enough to do by hand. Anyone with high school level chemistry should understand it, and even without high school chemistry it is quite easy to follow. I did preface it with it being beginner level. Why do we have a brewing science forum if it is intentionally manipulated to keep it out of the hands of beginners? I don't see anyone else trying to help beginners with the rudimentary mathematics and chemistry, so I simply picked up the ball and started to run with it. Others seem to want to make all of this so hard that it is out of reach for the average Joe.

Do beginners want the rudimentary mathematics and chemistry or are your posts solutions in search of problems?

Also, If they do want it, so they want simplified approximations or the actual equations?

 

[Silver_Is_Money]

Do beginners what the rudimentary mathematics and chemistry or are your posts solutions in search of problems?

I think they can be quite helpful. Can you fault the chemistry? Or are you merely willing to parrot the work of others? I generally prefer to blaze my own trails. You always quite honorably claim to be one who is simply trying to understand, and so am I. If the chemistry that led to my simplistic approaches formulas at the beginning of this thread is faulty, attack the faults in the chemistry, and replace it with an improved version that is within the reach of the average beer brewer. That way many can learn and benefit.

 

[RPh_Guy]

Easy or not, I guess we'll have to disagree that the average Joe wants to do this by hand.

 

[Big Monk]

I think they can be quite helpful. Can you fault the chemistry? Or are you merely willing to parrot the work of others? I generally prefer to blaze my own trails. You always quite honorably claim to be one who is simply trying to understand, and so am I. If the chemistry that led to my simplistic approaches formulas at the beginning of this thread is faulty, attack the faults in the chemistry, and replace it with an improved version that is within the reach of the average beer brewer. That way many can learn and benefit.

I would add the affect of pH on HCO3 normality. It’s an important and valid concept for someone trying to learn this stuff.

I’ll leave it at that.

 

[Silver_Is_Money]

You are assuming that the "normality" of bicarbonate us 1 mEq/mmol. That is only true at very low pH. Here are the normalities at some more typical mash pH's
5.2 0.938
5.4 0.905
5.6 0.858

A.J., though this is outside of the realm of beginner stuff, this quadratic formula derived from your 3 data points for baking soda seems to fit your normality correcting factors as seen above.

normality correction factor at mash pHz = -3.118 + 1.69*pHz - 0.175*pHz^2

A.J., do you agree with the validity of this method of baking soda addition quantity correction over a specifically narrow range of typical mashing pH targets spanning 5.1 to 5.7 pH?

I.E., does 1/(normality correction factor formula for pHz) * Baking Soda addition computed for a normality of 1 = actual baking soda addition required for a given pHz within the accepted mash pH range for nominal 25 degree C. meter readings?

Derek, does this properly address your concern as seen above? Or is your concern more along the lines of the chart (originally from A.J. I believe) seen below?

 

[Big Monk]

Though this is outside of the realm of beginner stuff, this quadratic formula derived from your 3 data points seems to fit your normality correcting factors as seen above.

normality correction factor at mash pHz = -3.118 + 1.69*pHz - 0.175*pHz^2

A.J., do you agree with this formula?

I.E., does 1/(normality correction factor formula for pHz) * Baking Soda addition computed for a normality of 1 = actual baking soda required for a given pHz?

Derek, does this properly address your concern as seen above? Or is your concern more along the lines of the chart (originally from A.J. I believe) seen below?

View attachment 612728

Why would we use a correction factor for something we have a direct equation for?

Why not just discuss and break down A.J.’s function?

 

[Silver_Is_Money]

Why would we use a correction factor for something we have a direct equation for?

Why not just discuss and break down A.J.’s function?

It's not we, it's me. And because if I simply accepted all of A.J.'s formulas then I would be merely parroting. Aren't all of these equations in the end merely empirical means to mathematically model an observed real world phenomenon? The R-squared correlation is right close to 1 for the correction formula I derived over the critical target range of 5.2 to 5.6 pHz's. Don't we all plot data points from observed data and then try to find an equation with the best R^2 correlation of fit possible?

 

[Big Monk]

It's not we, it's me. And because if I simply accepted all of A.J.'s formulas then I would be merely parroting. Aren't all of these equations in the end merely empirical means to mathematically model an observed real world phenomenon? The R-squared correlation is right close to 1 for the correction formula I derived over the critical target range of 5.2 to 5.6 pHz's. Don't we all plot data points from observed data and then try to find an equation with the best R^2 correlation of fit possible?

Parroting seems like an insult.

Yes, I am a fan of the way A.J. has presented the established chemistry and I feel that I now, more than ever, actually understand that chemistry. So I try to talk in terms of the functions A.J. created to help people understand the chemistry.

I try to stick with those because outside of the unknowns with respect to malt, all the other water chemistry equations, i.e. mineral acids, Baking Soda, Lime, alkalinity, etc. are well established. A.J. didn’t make these functions up out of thin air.

I’m gonna lay off for a while for 2 reasons:

1.) We are starting to dominate every water related topic on this forum;

2.) Its becoming less interesting. Over the summer was a thrilling time when we discussed all these interesting topics. Now there’s this.

 

[Silver_Is_Money]

Parroting seems like an insult.

Actually it is a means of duly honoring and respecting someones accomplishments, just as you have indicated. It simply isn't always my cup of tea. But I truly admire your accomplishments with it. And I wish I could figure out how to make your latest effort work in LibreOffice. It is in fact the sole reason why I blew trustworthy and stable LibreOffice 6.0 off of my computer and replaced it with their cutting edge version 6.2. My hope in doing so was to be able to run your latest spreadsheet.

 

[ajdelange]

Aren't all of these equations in the end merely empirical means to mathematically model an observed real world phenomenon?

No, not exactly. They are models but they are not empirical. The formulas in question here derive from the Henderson Hasslebalch equation which is a rearrangement of law of mass action and while the law of mass action may have originally been suggested by empirical observation it is now more grounded in the fundamental science. In deriving my take on the Henderson Hasselbalch equation I did not do empirical fits to anything. I simply algebraically manipulated Henderson Hasslebalch to determine individual species concentration and from them charge for all species derived from the acid in question (usually carbonic). My approach removes empiricism from the parts of the mash for which robust non-empirical models (Henderson-Hasselbalch) exist. Now the twist on this, which results in differences so small we can ignore them, is Debye-Hückle which is derived from the laws of physics but does not quite fit observation without an empirical adjustment (Davis adjustment).

The malts are a different matter. Their models are empirically derived.

Now when you have a function such as, 1- Qacid(pH), you can compute numbers from that function and then try to fit a polynomial to it and deduce that 1 - Qacid(pH) is approximately equal to a + b*pH + c*pH^2 + ... but why do that if you have 1 - Qacid(pH)? You might if it helps to to discover that 1 - Qacid(pH) is close to being linear in some region or close to being quadratic in another. In the case of bicarbonate it is clear that it is sort of linear in the mash pH region. For pH of 5.2 one can approximate its value as about 5% less than 1. For pH 5.4 it is about 10% less than 1 and for pH 5.6 it is about 15% less than one. These numbers are not exact. If one wants the exact numbers he puts 1 - Qacid(5.4) into his spreadsheet and gets the exact number. But if he had a proton surfeit of 100 mEq in a mash and wants pH 5.4 he can easily mentally approximate the required bicarbonate as 100/0.9 = 111 mmol.