# Homebrewers Association | AHA Forum

## General Category => All Grain Brewing => Topic started by: elemenoh on February 23, 2021, 03:31:26 PM

Title: CaCO3 * 1.22 = HC03?
Post by: elemenoh on February 23, 2021, 03:31:26 PM
Hi, first time poster. I'm trying to understand my water better. I'm reading the Palmer Water book again. Unfortunately, my chemistry is weak (as water you might say). And I can't seem to find all the answers to my questions.

I can not find HCO3 (Bicarbonate) on my water report. But I do have Hardness as CaCO3 (calcium carbonate). It appears that if I multiply my Hardness as CaCO3 by 1.22 I can get the correct number for HCO3.

First off, is this correct? Second, if so, where does the "1.22" come from?
Title: Re: CaCO3 * 1.22 = HC03?
Post by: Megary on February 23, 2021, 04:58:51 PM
Both hardness and alkalinity are expressed as CaCO3.

From Bru'N Water (Thanks, Martin):

Alkalinity (ppm as CaCO3) = Bicarbonate (ppm) * .83

...which would be fine as

Alkalinity (ppm as CaCO3) *1.22 = Bicarbonate (ppm)

I'm no water expert, but I think that's correct.
Title: Re: CaCO3 * 1.22 = HC03?
Post by: Silver_Is_Money on February 23, 2021, 09:03:51 PM
It is a ratio of equivalent weights (EQ Wt).

MW of CaCO3 = 100.0869 g./mole
Valence of Ca++ = 2
Therefore EQ Wt = 100.0869/2 = 50.04345 g./Eq

MW of HCO3- = 61.01684 g./mole
Valence = 1
Therefore Eq Wt = 61.01684 g./Eq

61.01684/50.04345 = 1.21928
Title: Re: CaCO3 * 1.22 = HC03?
Post by: elemenoh on February 23, 2021, 09:56:40 PM
Alright thanks! This points me in the right direction!
Title: Re: CaCO3 * 1.22 = HC03?
Post by: narvin on February 24, 2021, 01:37:05 AM
It is a ratio of equivalent weights (EQ Wt).

MW of CaCO3 = 100.0869 g./mole
Valence of Ca++ = 2
Therefore EQ Wt = 100.0869/2 = 50.04345 g./Eq

MW of HCO3- = 61.01684 g./mole
Valence = 1
Therefore Eq Wt = 61.01684 g./Eq

61.01684/50.04345 = 1.21928

This is all true, for converting alkalinity as Ca CO3 to bicarbonate ppm.

However, hardness and alkalinity are two completely different things, as mention in the previous post.  You cannot convert water hardness as CaCO3 to bicarbonate. If your water report doesn't list alkalinity or bicarbonate (which is equivalent) you should just send a water sample to ward labs to get a complete brewing test for \$16.
Title: Re: CaCO3 * 1.22 = HC03?
Post by: mabrungard on February 24, 2021, 02:03:30 AM
I can not find HCO3 (Bicarbonate) on my water report. But I do have Hardness as CaCO3 (calcium carbonate). It appears that if I multiply my Hardness as CaCO3 by 1.22 I can get the correct number for HCO3.

You have a HARDNESS value.  You can't use it to calculate a bicarbonate content.  You would need to have an ALKALINITY value.
Title: Re: CaCO3 * 1.22 = HC03?
Post by: Silver_Is_Money on February 24, 2021, 02:23:20 PM
Ah, after a good jolting, I see now what the OP is attempting.  But hardness (as CaCO3) times 1.219... does not at all equal (or equate to) bicarbonate.  Alkalinity (as CaCO3) times 1.219... equals (or better, equates to) bicarbonate (but only for specifically the case where the waters pH is within the typical or 'normative' pH neutrality range).
Title: Re: CaCO3 * 1.22 = HC03?
Post by: elemenoh on February 24, 2021, 02:52:20 PM
I can not find HCO3 (Bicarbonate) on my water report. But I do have Hardness as CaCO3 (calcium carbonate). It appears that if I multiply my Hardness as CaCO3 by 1.22 I can get the correct number for HCO3.

You have a HARDNESS value.  You can't use it to calculate a bicarbonate content.  You would need to have an ALKALINITY value.

OK thanks! I have a total alkalinity value. But not alkalinity as CaCO3 ... not sure if there is a difference. I will probably just do the water analysis someone mentioned.
Title: Re: CaCO3 * 1.22 = HC03?
Post by: Silver_Is_Money on February 24, 2021, 03:25:29 PM
If Hardness is reported in units of CaCO3, that typically means that Alkalinity will also be reported in units of CaCO3.
Title: Re: CaCO3 * 1.22 = HC03?
Post by: BrewBama on February 24, 2021, 07:13:15 PM
In my mind Hardness is Calcium and Magnesium.
To get Ca = Total Hardness / 1.25.
To get Mg = Total Hardness / 5.
(Ref: Noonan)

At normal water supply pH, most of the alkalinity is present as bicarbonate. Alkalinity is the resistance (buffer) to a change in pH.
Bicarbonate = alkalinity *61 / 50.
(Ref: Troester)
Title: Re: CaCO3 * 1.22 = HC03?
Post by: majorvices on February 24, 2021, 09:38:57 PM
In my mind Hardness is Calcium and Magnesium.
To get Ca = Total Hardness / 1.25.
To get Mg = Total Hardness / 5.
(Ref: Noonan)

Yeah - 80% of the total hardness is (usually but not always) calcium while magnesium makes up the rest IIRC.

But the alkalinity is what is important is the alkalinity not the *technically* the hardness since that is what the mash reacts to. I keep it simple. I just brew my water straight up for the SRM it is suited for and dilute with RO for paler beers and add bicarbonate for darker beers.

Title: Re: CaCO3 * 1.22 = HC03?
Post by: Silver_Is_Money on February 25, 2021, 05:16:21 AM
Yeah - 80% of the total hardness is (usually but not always) calcium while magnesium makes up the rest IIRC.

Closer to 70% of fresh water total hardness is Ca++ and 30% is Mg++ on average in my research.  YMMV

MW of CaCO3 = 100.0869
MW of Ca++ = 40.078
MW of Mg++ = 24.305

100.0869/40.078 = 2.4973
100.0869/24.305 = 4.118

Total Hardness (as CaCO3) = TH = 2.4973(Ca++) + 4.118(Mg++)

Therefore, on average:

Ca++ ions mg/L (ppm) ~= (0.70*TH)/2.4973
Mg++ ions mg/L (ppm) ~= (0.30*TH)/4.118
Title: Re: CaCO3 * 1.22 = HC03?
Post by: narvin on February 25, 2021, 01:22:49 PM
Yeah - 80% of the total hardness is (usually but not always) calcium while magnesium makes up the rest IIRC.

Closer to 70% of fresh water total hardness is Ca++ and 30% is Mg++ on average in my research.  YMMV

MW of CaCO3 = 100.0869
MW of Ca++ = 40.078
MW of Mg++ = 24.305

100.0869/40.078 = 2.4973
100.0869/24.305 = 4.118

Total Hardness (as CaCO3) = TH = 2.4973(Ca++) + 4.118(Mg++)

Therefore, on average:

Ca++ ions mg/L (ppm) ~= (0.70*TH)/2.4973
Mg++ ions mg/L (ppm) ~= (0.30*TH)/4.118

Can confirm that it does vary  ;). My well water has 11ppm Mg but only 17ppm Ca, which is just over 50% Mg hardness.  It also has high sodium chloride.  This makes me think it's likely very soft and the main mineral contributions are from ice melt applied to a major highway nearby.  We're only a mile away but I've heard that houses right next to it have had water treatment systems installed by the state due to ppm in the thousands.
Title: Re: CaCO3 * 1.22 = HC03?
Post by: majorvices on February 25, 2021, 02:02:51 PM
I had to go look where I saw that (80/20) thing and it was here (https://byo.com/article/understanding-residual-alkalinity-ph/) from years ago. And yeah, just because it matches up mostly with my water doesn't mean it is universal.

"Total hardness is the sum of magnesium and calcium hardness. Dividing the calcium level in mg/L by 20 and multiplying by 50, or multiplying the value in mEq/L by 50, will determine the calcium hardness as CaCO3. For magnesium hardness as CaCO3, divide the magnesium level in mg/L by 12.1 and multiply by 50, or multiply the value in mEq by 50. If hardness is not separated into the contributions of calcium and magnesium, you can estimate it by attributing 80 percent to calcium and 20 percent to magnesium (the actual percentages in your water may be different). To calculate alkalinity as CaCO3, divide the bicarbonate level in mg/L by 61 and multiply by 50, or again multiply the value in mEq/L by 50."

I have a high school understanding of chemistry that was clouded by a lot of marijuana smoke and an art degree on top of that so, don't listen to me. But that is a very good article  FWIW.

Title: Re: CaCO3 * 1.22 = HC03?
Post by: BrewBama on February 25, 2021, 02:12:05 PM
+1. My understanding of chemistry is rudimentary at best.

At any rate, I believe the OP confused hardness and alkalinity.

We all agree hardness is a measure of calcium (Ca+2) and magnesium (Mg+2) ions in the water.

Alkalinity is a separate issue. It is a measure of carbonates (CO3-2), bicarbonates (HCO3-) and hydroxide (OH-) in the water, and is defined by how much strong acid is necessary to move a sample to a predetermined pH.

Sent from my iPad using Tapatalk
Title: Re: CaCO3 * 1.22 = HC03?
Post by: Troy Walker on March 05, 2021, 01:57:15 AM
Hi,

I'm a water guy.  Water chemistry is a bit challenging because we use funny units to measure and report things.  Bicarbonate (HCO3-) is often reported in water quality reports as "alkalinity".  And that's correct.  Most water between pH of about 4.2 and 8.2 (where our city water usually is) almost all the alkalinity in water is bicarbonate.  Yep, the same thing that's in baking soda.

So I was trained as a chemical engineer.  I learned my periodic table and all that.  Trouble is, water treatment was first done by civil engineers.  Lovely people, don't get me wrong, but chemistry.....wasn't their strong suit.  So instead of using things like "moles" or other chemistry concepts, they decided in water to use a common currency for measurement that makes the math a bit easier.  Actually not a bad idea.  What they landed on was to measure things in terms of the molecular weight of calcium carbonate (CaCO3).  You know why?  Well, the atomic weight of calcium is 40. Carbon is 12.  Oxygen is 16 (and there are three of those).  40 + 12 + 16 + 16 +16 = 100!  So it's a convenient number to use.

Here's the confusing bit.  It isn't actually calcium carbonate.  It's just expressed in those units.  Think of it as converting Euros to dollars.

So yes, you will often see bicarbonate (or sometimes just alkalinity) reported as mg/L CaCO3.  In other words, milligrams per liter as calcium carbonate.  Here's an excerpt from the Water Board of California that gives an explanation of the chemistry.  But yes, HCO3 = 1.22 x bicarbonate expressed as calcium carbonate.

https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/documents/drinkingwaterlabs/AlkalinityConversions.pdf

Alkalinity is important in water because it acts as a buffer.  What does that mean?  If you have low alkalinity, a small amount of acid or caustic will cause the pH to have big swings low or high.  If you have high alkalinity, that same amount of acid or caustic won't change the pH quite so much.  Because it's buffered.  Buffering happens because pH is actually a balance between bicarbonate and dissolved carbon dioxide in water.  You add acid, you convert some of the bicarbonate to CO2.  You add caustic, you do the reverse.  If there's lots of bicarbonate, then you need to add a lot of acid to make enough CO2 to change the pH.

Anyway, hopefully your head isn't spinning.  Relax, don't worry, and have a homebrew.
Title: Re: CaCO3 * 1.22 = HC03?
Post by: BrewBama on March 05, 2021, 03:10:49 AM
Good stuff Mr Walker!
Title: Re: CaCO3 * 1.22 = HC03?
Post by: roger on March 05, 2021, 01:44:44 PM
+1 Thanks for the explanation.
Title: Re: CaCO3 * 1.22 = HC03?
Post by: majorvices on March 06, 2021, 03:34:13 PM
Great explanation, thanks!