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Home Brew Forums > Home Brewing Beer > Brew Science > Water Calculator: Does it look right?
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Old 12-13-2011, 03:37 AM   #11
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You lost me right there. You want NO chlorine. But it has nothing to do with calcium chloride.

I don't think Martin told you to reduce the calcium chloride, but if you can provide a link so I can see where he mentioned that, I can figure out what he's talking about.
important typo... that should say
"What if i kill the epsom salt and replace some of it with gypsum? The epsom and gypsom both add to my sulfate which i was advised to reduce so it is a fine line as i cant increase my calcium by much. I also cant add calcium chloride as i was advised to reduce my CHLORIDE too"

In post 5 of this thread:

Quote:
It doesn't look like you need to add the epsom salt to the water. The ending concentrations for both sulfate and chloride are too high and should be moderated
So in short, he mentioned that i should look at reducing my chloride as well as my sulfate, but i cant get my calcium up without affecting sulfate and or chloride. Catch 22 i guess.

It may also be important to note that my grams are NOT per gallon.. I noticed that his spreadsheet is done per gallon. The grams are total and the final water profile is the outcome based on my mash and sparge amounts.
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Old 12-13-2011, 04:24 AM   #12
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PHEW! okay using Bru'n Water and a lot of playing with numbers here is what i have. I need to check my alkalinity from the grains on the EZ calc as i know the amounts are right on this one.

1.5 grams of gypsom, 2.5 grams of baking soda, 1.4 grams of calcium chloride, 3.2 grams of chalk which yields:

Calcium - 68
Magnesium - 2
Sodium - 25.3
Sulfate - 34.1
Chloride - 30.4
Bicarbonate 169.7
S04 / CL ration or 1.1
Alkalinity 5.3
Net Mash Acidity 19.6

So, how does it look now?

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Old 12-13-2011, 06:55 AM   #13
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Not so good. You have violated one of the first principles: don't add alkali to water or mash unless a mash pH meter reading tells you one is necessary. Beyond that there is no way that you could have an alkalinity of 5.3. Adding that much baking soda to 9 gallons would give an alkalinity of 35 not to mention the chalk. The chalk does not dissolve in water. If you want it to do so you must add acid. Many brewers don't and add it to the mash instead. If you do this it is impossible to come up with an effective alkalinity number because there is no way to know the either the amounts or pK's of the acids that are available in the malt to dissolve it. If they are available in insufficient quantity to effect the dissolution of all the chalk then 1) all the calcium from the chalk is unavailable which throws that number off and 2)much more significant than that is that the mash pH will be pulled way too high. Probably more home brew stouts have been ruined by following a program like this one than Carter has sold pills. Put another way you are not the first guy to have been led into this trap. The spreadsheets do not model carbonate correctly.

Having followed this thread and the previous one I really think the best thing for you to do is add a teaspoonful of calcium chloride to your water and leave it at that. This will make a good beer. There is a chance that your mash pH will be on the low side depending on the nature of the dark malts you are using but at the level you propose to use them it is small. Your posts only serve to illustrate that tailoring water can be a complicated business and that all the various spreadsheets and calculators can lead you astray until such time as you understand the underlying principles better.

The Primer in the Stickies is intended to KISS this all for people in your position. I'd really suggest you use its guidance until you are a bit more up to speed.

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Old 12-13-2011, 07:34 PM   #14
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Man this water stuff is like a huge trap ha ha.

So I understand what you are saying about the chalk. Makes sense. But the rest has me thrown for a loop. In short, the beer I am trying to brew has a bit of roasted grains (2 lbs) and some crystal (1 lb 12 oz) which i expect will affect mash ph.

The Excel file i used on Bru'n Water is below. When going through it, it said that my mash ph is going to be too low that i needed to add alkalinity. Are you saying to ignore this entirely? It makes sense that the chalk is not easily measurable and; therefore, hard to judge. I understand that part, but should i not use another mineral to up this ph or are you saying that this alkalinity is not adding up for you? It appears as though I could use lime to up my calcium and adjust for ph in a more predictable manner. I have been advised to add calcium for sure, so that is the main source of calcium in this calculation but again, i dont want to overdue my mash ph.

Bru'n Water Link

On EZ water calc it shows my PH will be 5.65 but on Bru'n Water is says that it will be 5.3 with the same settings. The 5.62 is a high but the 5.32 is good ( as far as i know). Which would you think is correct?

Here is the EZ Water Calc if you want to see it.

EZ Water Calculator (no Chalk)

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Old 12-13-2011, 09:17 PM   #15
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On EZ water calc it shows my PH will be 5.65 but on Bru'n Water is says that it will be 5.3 with the same settings. The 5.62 is a high but the 5.32 is good ( as far as i know). Which would you think is correct?
This observation should speak volumes. I have no idea which if either is correct. These spreadsheets were prepared by 2 intelligent guys who came up with different models for carbonate and mash acidity based on their knowledge and experience. Their carbonate models are simplifications of the actual chemistry which are required to make them fit into a spreadsheet (or one you would be willing to tackle at any rate) and the malt part is not, IMO, capable of being modeled because of variations between maltsters, barley cultivars and titratable acidify differences between batches of the same cultivar malted in the same way by the same maltster. I have shared with both authors the results I obtain when I brew which did not match either and one has made adjustments so that his spreadsheet matches my experience more closely but that does not mean it will match yours.

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Man this water stuff is like a huge trap ha ha.
Yes it is and many have fallen into it. That's why I came up with the Primer (at he request of the moderator of this forum). It won't make the best beer but it will make a good beer and with experience you can make excellent beer by making gradual tweaks to its recommendations. You can shorten the time and effort required by investment in a decent pH meter.

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... the beer I am trying to brew has a bit of roasted grains (2 lbs) and some crystal (1 lb 12 oz) which i expect will affect mash ph.
It will. It will cause the pH to be lower than it would be without the dark malt. That is why dark malts were used - mash pH's were too high without them. Of course at the time brewers started using dark malt Doc Sørenson (inventor of the concept of pH) was a bit of mitochondrial DNA.


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Originally Posted by Jewrican View Post
The Excel file i used on Bru'n Water is below. When going through it, it said that my mash ph is going to be too low that i needed to add alkalinity.
It tends to do that relative to my experience.

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Originally Posted by Jewrican View Post
Are you saying to ignore this entirely?
Not exactly. I am really saying that when brewing a dark beer pH predictions can be way off and that the popular models tend to predict that it will be too low. I think this may be in part because home brewers have used pH strips to check mash pH and these tend to read 0.3 or more low which supports the low pH models. What I am saying is that you shouldn't ever add alkali to a mash unless a pH meter reading says you should. My experience and that which I have been able to glean from others is that the chances of going too high (from adding too much alkali) are greater than the chances of going too low by not having enough. But there are going to be cases where you can drop under. That's why you need a pH meter. If you don't have one then I feel that statistically speaking you will have fewer screwups by not adding alkali than if you do.

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Originally Posted by Jewrican View Post
It makes sense that the chalk is not easily measurable and; therefore, hard to judge. I understand that part, but should i not use another mineral to up this ph
The mineral you want is calcium bicarbonate. That is the source of alkalinity in natural water (magnesium bicarbonate is actually in there too. But you can't buy either of those salts. You have to make them which is an elaborate process involving chalk and CO2 gas.


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Originally Posted by Jewrican View Post
.. or are you saying that this alkalinity is not adding up for you?
You will find lots in the literature about how to get calcium and magnesium bicarbonate out of water but very little on how to put it in. That is because alkalinity is the brewer's enemy. The only times we want to add alkalinity is when we brew a style that has a lot of dark malt intended to combat the alkalinity that the brewers of yore could not get rid of but are trying to brew it with water that has even less than that (about 50 ppm as CaCO3). So no, it does not add up for me.

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Originally Posted by Jewrican View Post
It appears as though I could use lime to up my calcium and adjust for ph in a more predictable manner.
Calcium hydroxide is sometimes recommended because it reacts immediately whereas the reactions of carbonate can be very slow. But this is a curse as well as a blessing. Lime is a strong base. Calcium carbonate is not. If you slip with lime you are instantly screwed.

The use of lime will not lead to better mash prediction. It is easier to calculate it's contributed alkalinity as a function of the amount of acid it reacts with (because it is a strong base) but the other half of the problem is that you can't model the acids in the grains at all accurately.


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Originally Posted by Jewrican View Post
I have been advised to add calcium for sure, so that is the main source of calcium in this calculation but again, i dont want to overdue my mash ph.
Chalk is a very poor source of calcium because
1) You don't get all the calcium you added if there isn't enough acid in the malt to dissolve it all
2) For each unit of pH reducing power from the calcium in chalk you have approximately 3.5 units of pH increasing power from the carbonate.

A much better source of calcium is the chloride and, if you are doing a style which wants sulfate, gypsum.
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Old 12-14-2011, 09:10 PM   #16
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I have shared with both authors the results I obtain when I brew which did not match either and one has made adjustments so that his spreadsheet matches my experience more closely but that does not mean it will match yours.
Just out of curiosity, which one was adjusted to more closely match your results?

I am really concerned that my dark beers have sucked due to this mash ph... and like you pointed out that it is tough to say which if either calculator is right (or closest for that matter).

If i do get a ph meter to test the ph, i have seen that it takes up to 15 minutes for the ph to even settle. Is this true?

If so, will adjusting at that time even make a difference or is the "damage" done? I want it to be as easy as your recommendation with that calcium chloride but i really think that it will end up low in ph again and result in another crappy stout.

If i decide to get a ph meter, what do you recommend? Is there anything other than the meter itself that I will need? Like calibration items?
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Old 12-14-2011, 09:39 PM   #17
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Just out of curiosity, which one was adjusted to more closely match your results?
I'm reluctant to answer that as in the first place it might not help you and in the second place might appear to be an endorsement of one over the other. Besides which I don't know that the other author might not have modified his model as well. Or that the one that did hasn't modified his back. The point I want to make is that a model is a model - very useful for attaining understanding and playing "what if" games but not to be relied upon too heavily. To discover the actuality of your particular situation you must either measure or make dozens of experimental brews in the hope that you will stumble on the right water chemistry without measurement.

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I am really concerned that my dark beers have sucked due to this mash ph... and like you pointed out that it is tough to say which if either calculator is right (or closest for that matter).
That is quite possible but there are, of course, other ways to achieve less than the desired result.

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If i do get a ph meter to test the ph, i have seen that it takes up to 15 minutes for the ph to even settle. Is this true?
It can be. Where the acid source is sauermalz it can take that long or longer for the reading to stabilize. Where chalk has been added it can take a long time for that to react.

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Originally Posted by Jewrican View Post
If so, will adjusting at that time even make a difference or is the "damage" done?
Obviously it is better if the mash goes straight to the desired pH and no adjustment is required but if your pH reading indicates that an adjustment is necessary it is better to do it than not. It isn't quite like temperature i.e. you don't need to fear that you have irreversibly denatured the enzymes.

It's a good idea to make a test mash. Take a pound of base malt and add the other malts in the same proportion as you intend to use in the full brew. "Mash in" with warm water and try to get the test mash to about your planned strike temperature. Hold for a while and then check pH. Use acid or alkali to adjust the pH if it out of range. Scale the amount of acid or alkali to the full volume and add that to the full brew.

Another approach, if the pH isn't too far off, is to make a note of what happened and correct it next time. If pH comes in at 6 it isn't going to ruin the beer but you should use more acid next time you brew it. And conversely if it comes in at 5.2 make a note to use some alkali next time.

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I want it to be as easy as your recommendation with that calcium chloride but i really think that it will end up low in ph again and result in another crappy stout.
I can't guarantee that it will be as easy as just CaCl2 addition but there is a good chance that it will be. It takes a lot of calcium to move pH appreciably. The oft recommended 50 mg/L will only lower it 0.06 pH.

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Originally Posted by Jewrican View Post
If i decide to get a ph meter, what do you recommend?
I don't because I'm not that familiar with the instruments that a homebrewer is likely to use. I believe a lot of the guys use the Hanna pHep units with success. I hope someone else will respond here.

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Originally Posted by Jewrican View Post
Is there anything other than the meter itself that I will need? Like calibration items?
Yes. You will need a supply of distilled or otherwise deionized water to rinse the electrode, a squirt bottle to make dispensing it easy, pH 4 and pH 7 buffers and electrode storage solution.
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Old 12-14-2011, 10:30 PM   #18
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I can tell you that Bru'n Water was not amended per AJ's results. That was with good reason.

AJ's results reflect the use of RO or distilled water which has very little alkaliity and I believe that his results are valid. But there is another factor that influences the result when water with more alkalinity is utilized in brewing.

The decarbonation of water due to heating affects the water alkalinity. As a more alkaline water is heated, the solubility of CO2 is reduced and that gas is driven out of the water. This results in the calcium carbonate (chalk) that is associated with that alkalinity to precipitate out of solution. This is the process that some brewers can use to reduce the temporary hardness of their water. This results in a two-fold change to the water, the calcium concentration is reduced and the bicarbonate concentration is reduced. This effect does not occur in distilled or RO water since there is very little temporary hardness.

The net effect of this phenomena is that there is a mash pH shift due to that decarbonation. Dozens of mash results from brewers around the country were used to develop a relationship between the net acidity of the mash (grain acidity - water alkalinity) and mash pH. That effect is incorporated into the mash pH prediction in Bru'n Water and its apparently the reason that AJ concludes that the algorithm in Bru'n Water cannot be correct. The shift in mash pH is about 0.15 units lower due to this decarbonation effect. For most brewers, they deal with a brewing water with alkalinity. Bru'n Water works very well for them. For brewers working with distilled or RO water, they may see the pH result shifted about a tenth or so higher than predicted by Bru'n Water. I still consider that a pretty good result.

I've been working on an enhanced algorithm that accounts for the use of low alkalinity water in brewing. The results are promising, but I'm not willing to roll it out quite yet. The interesting thing is that even though heating decarbonates the water and drives off the CO2, the chalk is left in the water. As AJ can attest, this leaves the chalk delivering only half the alkalinty that it would produce if it was fully dissolved via CO2 dissolution. That effect needs to be accounted for in this equilibrium and that empirical chemistry still needs to be verified in practice. I've devised the experiments for this, but I have not yet conducted them.

Keep tuned!

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Old 12-15-2011, 06:45 AM   #19
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I can tell you that Bru'n Water was not amended per AJ's results. That was with good reason.
There's your answer, Jewrican

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Originally Posted by mabrungard View Post
AJ's results reflect the use of RO or distilled water which has very little alkaliity and I believe that his results are valid. But there is another factor that influences the result when water with more alkalinity is utilized in brewing.
That's true of my lagers but not true of my stouts (Lewis's Irish stout) which I usually brew with straight well water (alkalinity of about 80, calcium hardness about 60, Mg hardness about 50 - AFAIK those are pretty typical numbers). These are the beers that deviate most from the Bru'n water predictions (though the lagers do too). Normally I get 5.55 with this recipe. Last time I brewed it I reduced alkalinity and hardness to 2/3 of the usual values and the pH was 5.6.

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The decarbonation of water due to heating affects the water alkalinity. As a more alkaline water is heated, the solubility of CO2 is reduced and that gas is driven out of the water. This results in the calcium carbonate (chalk) that is associated with that alkalinity to precipitate out of solution. This is the process that some brewers can use to reduce the temporary hardness of their water. This results in a two-fold change to the water, the calcium concentration is reduced and the bicarbonate concentration is reduced. This effect does not occur in distilled or RO water since there is very little temporary hardness.

When brewers decarbonate water with heat they bring it to boiling and sparge it with steam or bring it to near boiling and sparge with air in order to drive off the CO2. At mash tun temperature (protein rest) the solubility of CO2 is still half what it is at room temperature (and at saccharification rest temperature 40% or so) but that may be moot at least in my case because the water (being well water) is oversaturated WRT CO2. OTOH is is well undersaturated WRT calcium carbonate. If I drive the CO2 off by boiling/sparging then the pH rises and the solution becomes supersaturated WRT CaCO3 and I get precipitation. This also happens with long standing and I'm sure heat helps move it towards equilibrium quicker but without the sparging I don't believe much CaCO3 is being dropped. That's why brewers, from the day they figured out how to do it, heat to boiling or use lime or some other means to reduce alkalinity. If the hardness and alkalinity are large enough i.e. if the water is, going in supersaturated WRT both CO2 and CaCO3 (e.g.I synthesize Burton water and put it in the HLT) then things are different. CaCO3 does precipitate at mash temperature and, of course, the alkalinity drops. But a brewer will still boil to get as much as he can out.

Even at boiling (at SLP) the solubility of CO2 is about 1/4 which is, in part, why it is unlikely that alkalinity can be brought below 50 by this technique (though you can do better by adding additional calcium before boiling).


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The net effect of this phenomena is that there is a mash pH shift due to that decarbonation.
At this point I am getting that decarbonated water produces mashes of lower pH than water that is not decarbonated. No problem with that concept. But I don't think much decarbonation takes place in the mash tun unless the water is close to saturation or supersaturated WRT CaCO3. I suppose if a brewer took alkaline water, mashed in with it cold and then heated it he would get CaCO3 precipitation in the mash tun but it would be a foolish brewer who did that. The object is to get rid of bicarbonate, not incorporate it in the mash as carbonate.

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Originally Posted by mabrungard View Post
Dozens of mash results from brewers around the country were used to develop a relationship between the net acidity of the mash (grain acidity - water alkalinity) and mash pH. That effect is incorporated into the mash pH prediction in Bru'n Water and its apparently the reason that AJ concludes that the algorithm in Bru'n Water cannot be correct.
No, I say it can't be correct (and I don't really say that - I say it is subject to the limitations of empirical models) because I don't believe you can know the "net acidity" of the system due to the effects of variations in the acidity of the malts from maltster to maltster, from cultivar to cultivar and from batch to batch. For example I once measured the DI water mash pH of Maris Otter at 5.6 whereas the EZ spreadsheet lists it at 5.77. The last time i did stout I got a mash pH of 5.6 so it's clear the DI mash pH of the MO wasn't 5.6. Obviously there is appreciable difference between samples of Maris Otter. And even if you did I doubt that would be sufficient as I think you would have to know the acidity as a function of pH i.e. the titration curve to be able to solve for pH.

But as this is an empirical model it only need fit the data. As you state plainly that the model does not consider any data from me I assume that it doesn't include data from anyone else who brews with RO water or anyone from the Pacific Northwest (where the water is soft and low in alkalinity) and therefore doesn't fit all the data. Thus it is not a useful predictor for people like us. This is what I mean by a limitation in the model. I'm not saying that it can't be improved to fit a broader range of data nor am I even saying that it should be.


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Originally Posted by mabrungard View Post
The shift in mash pH is about 0.15 units lower due to this decarbonation effect.
It almost looks as if you are saying that, putting the stouts aside for the moment, while Bru'n water underestimates pH for my Pils brewed with Pilsen like water were I to add some alkalinity it would produce a number closer to what I actually see and the reason for this is that the alkalinity would drop out in the mash tun. I have to admit I'm pretty confused here.

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Originally Posted by mabrungard View Post
For most brewers, they deal with a brewing water with alkalinity. Bru'n Water works very well for them.
How much alkalinity is required? The reason for asking this is that while, as I admitted above, I'm pretty confused here, it seems as if this 0.15 is a bias that is valid when the water is alkaline but not when it isn't which suggests that an adjustable bias of 0.15*alk/alk_max might work.


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Originally Posted by mabrungard View Post
For brewers working with distilled or RO water, they may see the pH result shifted about a tenth or so higher than predicted by Bru'n Water. I still consider that a pretty good result.
Given that most are using pH meters with accuracies of 0.05 to 0.1 I agree.

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The interesting thing is that even though heating decarbonates the water and drives off the CO2, the chalk is left in the water. As AJ can attest, this leaves the chalk delivering only half the alkalinty that it would produce if it was fully dissolved via CO2 dissolution.
If you suspend 100 mg (1 mmol) of chalk in one liter of DI water and take it to a lab with a request for an alkalinity test the lab will add strong acid to it gradually while measuring the pH. After the lab has added 1 mEq of acid the pH will be 8.3 and all ( actually 98%) of the chalk will have dissolved and been converted to bicarbonate. The solution will contain (approximately) 1 mmol of bicarbonate and 1 mmol of chloride (assuming hydrochloric acid was used). Upon adding a second mEq the pH will reach 4.3 which is the usual endpoint and so no more acid will be added and 2 mEq/L will be recorded as the alkalinity (which will be multiplied by 50 to give 100 ppm as CaCO3 as the reported value). Now if you added the first mEq of acid before you took the sample to the lab it would only have to add the 1 more and thus report the alkalinity as 1 mEq/L (50 ppm as CaCO3) because that's all it would take to reach the endpoint.

If you suspend 100 mg (1 mmol) chalk in a liter of water and bubble CO2 through it until all the chalk is dissolved and the pH is brought to 8.3 it will contain approximately 2 mmol bicarbonate - one from the chalk and the other from the carbonic acid formed when CO2 reacts with water. If you give that to an analyst and he adds enough acid to convert all the bicarb to carbonic (reach pH 4.3) it will take 2 mEq of acid to do that - one for each of the 2 mmol of bicarbonate. The analyst will report 2 mEq/L or 100 ppm as CaCO3 as the alkalinity.

Thus chalk suspended in water has the same alkalinity as chalk dissolved in water with CO2 (at pH 8.3) - not half. Chalk dissolved in water using a strong acid (pH 8.3) has alkalinity half that of chalk suspended in water or dissolved with CO2. Pertinent to this discussion is that chalk precipitated from water does not produce a reduction in alkalinity unless the water is separated from the precipitated chalk.


It's late and I'm rambling.
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Old 12-15-2011, 02:49 PM   #20
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Thinking a bit more about last night's post I thought it might be interesting to look a little deeper into what happens when one heats a solution of calcium bicarbonate. We've already noted that the solubilty of CO2 drops but so does the solubility of CaCO3. The loss of CO2 results in a rise in pH, this causes a conversion of bicarbonate to carbonate and the reduced solubility of carbonate causes precipitation of calcium carbonate. The proton which converts a bicarbonate ion to carbonic and then to CO2 and water is supplied by another bicarbonate ion which gives one up in the process of converting to carbonate which comes out of solution. Thus the pH doesn't change very much. After precipitation you have water over lime with CO2 over that. It is possible to compute what the concentrations of calcium, bicarbonate and CO2 are at thermodynamic equilibrium. Whether thermodynamic equilibrium is reached or not is a separate question. I think under the conditions of vigorous ebulition it probably is and fairly quickly. I think under the conditions of water sitting in an HLT or solution sitting in a mash tun it may take hours. I think for room temperature water in a beaker it takes days.

The numbers in the table below (excuse the dashes - I put them in there to force the numbers into columns) show equilibrium values. Temperature is in °C, alkalinity and hardness in ppm as CaCO3 and CO2 in mg/L. The drivers here are the partial pressure of CO2 in the atmosphere and the physical constants pK1, pK2, pKhy, pKw and pKs (respectively the negative logarithms of the acidity constant for the first dissociation of carbonic acid, the acidity constant for the second proton, the Henry coefficient which is here defined as the ratio of the concentration of CO2 in the solution to the partial pressure of CO2 in the atmosphere, the dissociation constant of water and the solubility product of CaCO3. All rows in the table except the last are for partial pressure of CO2 = 0.0003 atmosphere. The last row assumes the alarmists are correct and the partial pressure of CO2 is 0.0006 atm.

temp---pH----Alk----Ca Hard---CO2 ----pKs ----- pKhy
20 ----8.30--53.7-----51.7-----22.7---8.45-------1.41
50-----8.30--34.2-----32.1-----13.4---8.66-------1.72
66-----8.30--28.1-----25.7-----10.1---8.82-------1.83
100----8.22--21.5-----18.9----- 4.6----9.27-------1.98

100*---8.04--24.5---- 21.9-----7.4 ----9.27------1.98

Note that the change in pKs from 20 to 100 °C represents solubility of CaCO3 at boiling which is about 39% of what it is at room temperature.

All these numbers depend on the models I came up with for the variations of the constants with temperature. As they are models they are subject to the usual caveats that go with models. And the same goes for the model into which I stuck the constants. This is not something I've ever asked NUBWS to do so there is some caution attached to that as well. But this model should give a good general impression of what is going on.

The other point I did not make last night is that when water hits mash it is the phosphates and organic acids (the acid groups on proteins) that pull the pH low. Calcium does precipitate but preferentially as the phosphate (hydroxyl apatite) which is much less soluble that the carbonate. This precipitation of phosphate lowers pH by a net release of protons. Unless the water is way oversaturated WRT to CaCO3 the mash pH will not reach the saturation pH and no precipitation of CaCO3 will occur. This does not mean the mash pH can't be pulled high enough by the bicarbonate to be sub optimal however. That's why some form of acid is required in most cases.

To illustrate this consider a water at pH 8.3 with alkalinity of 200 ppm as CaCO3 and like calcium hardness. Suppose this is mixed with grain which contains a base malt at 1.5L per pound (i.e. fairly loose mash) and that the malt contains 2% phosphate by weight (typical value) as phosphorous half of which is available. This amounts to 8725 mg/L phosphate. Assuming it all to be in the monobasic form the mash pH would be 5.70 at 120 °F (protein rest temperature). This pH is 2.06 units less than the saturation pH WRT calcium carbonate. Calcium carbonate would not precipitate. It is, however, 1.3 pH units higher than the saturation pH WRT hydroxyl apatite and that mineral will precipitate. This is hardly the complete story as the amino acids have been ignored but from the point of view of the saturation pH of this water relative to the mash pH, however arrived at, it seems pretty clear that calcium carbonate will not precipitate in the mash.

[Edit] The phosphate number I gave for malt is more typical "as P2O5" not "as P". Cutting the value in phosphate value in half would be more reasonable. So consider the available portion higher if you want to accept the numbers I gave in the first posting. This leads to a reasonable mash pH. I also re-ran the numbers at half the phosphate which predicts mash pH at 6. This is still well below the saturation pH for calcium carbonate and well above the saturation pH for apatite so the conclusions don't change.

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