Author Topic: CaCO3 * 1.22 = HC03?  (Read 569 times)

Offline elemenoh

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CaCO3 * 1.22 = HC03?
« 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?

Offline Megary

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Re: CaCO3 * 1.22 = HC03?
« Reply #1 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.

Offline Silver_Is_Money

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Re: CaCO3 * 1.22 = HC03?
« Reply #2 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

Offline elemenoh

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Re: CaCO3 * 1.22 = HC03?
« Reply #3 on: February 23, 2021, 09:56:40 PM »
Alright thanks! This points me in the right direction!

Offline narvin

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Re: CaCO3 * 1.22 = HC03?
« Reply #4 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.

Offline mabrungard

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Re: CaCO3 * 1.22 = HC03?
« Reply #5 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.
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Offline Silver_Is_Money

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Re: CaCO3 * 1.22 = HC03?
« Reply #6 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).
« Last Edit: February 24, 2021, 03:24:06 PM by Silver_Is_Money »

Offline elemenoh

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Re: CaCO3 * 1.22 = HC03?
« Reply #7 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.

Offline Silver_Is_Money

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Re: CaCO3 * 1.22 = HC03?
« Reply #8 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.

Offline BrewBama

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Re: CaCO3 * 1.22 = HC03?
« Reply #9 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.
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Offline majorvices

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Re: CaCO3 * 1.22 = HC03?
« Reply #10 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.

« Last Edit: February 25, 2021, 01:06:27 AM by majorvices »

Offline Silver_Is_Money

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Re: CaCO3 * 1.22 = HC03?
« Reply #11 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

Offline narvin

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Re: CaCO3 * 1.22 = HC03?
« Reply #12 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.

Offline majorvices

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Re: CaCO3 * 1.22 = HC03?
« Reply #13 on: February 25, 2021, 02:02:51 PM »
I had to go look where I saw that (80/20) thing and it was here 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.

« Last Edit: February 25, 2021, 02:12:19 PM by majorvices »

Offline BrewBama

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Re: CaCO3 * 1.22 = HC03?
« Reply #14 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.


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