Total alkalinity equation. Palmer vs Bru'n Water vs Kaiser

[jdebonth]

I have compared the following water sheets: Palmer, Bru'n Water, and Kaiser. As far as I can tell, all the calculations are more or less the same, with one key difference, the total alkalinity. The total alkalinity drives the RA and so is probably the most important calculation on the sheet.

Bru'n Water and Kaiser are the same and calculate Total Alkalinity based purely on bicarbonate as an input, whereas John Palmer uses PH in addition to the bicarbonate. The issue is that I get a 15% difference in values between the two using the same inputs, and I am fairly certain my pH value is correct (I am using bottled water and so I assume the value is professionally measured and tightly controlled).

Has anyone else picked up on this difference? Is there a view as to which is more accurate and why?

I know the 3 authors frequent this site, it would be great if they could comment! Thanks.

 

[ajdelange]

I have compared the following water sheets: Palmer, Bru'n Water, and Kaiser. As far as I can tell, all the calculations are more or less the same, with one key difference, the total alkalinity. The total alkalinity drives the RA and so is probably the most important calculation on the sheet.

Total alkalinity is the most important single water parameter but as RA isn't really important at all except as a cursory means of comparing one water source to another its dependency on total alkalinity is really not a matter of importance.

Bru'n Water and Kaiser are the same and calculate Total Alkalinity based purely on bicarbonate as an input, whereas John Palmer uses PH in addition to the bicarbonate.

The first thing people need to understand (and all three of the gentlemen you mentioned do) is that the laboratory measures alkalinity - not bicarbonate. To measure bicarbonate requires some pretty hairy gear whereas the alkalinity test is very simple. If you go to the aquarium shop, do they sell you a bicarbonate test kit? No, they sell you an alkalinity test kit. Having measured the alkalinity the lab then calculates the bicarbonate and carbonate from the alkalinity and pH - that is where pH comes into it. The calculations are detailed in the sticky at https://www.homebrewtalk.com/showthread.php?t=473408. I noticed a few years back that Ward Labs reports didn't quite check out, corresponded with them and found out that they were a)doing the alkalinity titration wrong and b) calculating bicarb and carb wrong. Fortunately this was only a problem when pH was above 8.2. They are now doing the titration right and the bicarbonate calculation is closer to being correct but the carbonate calculation is still off. As most people's reports show CO3-- < 1 that is not really a problem.

Has anyone else picked up on this difference? Is there a view as to which is more accurate and why?

Hell yes I've noticed the difference and complained for years that all the spreadsheets should be fixed to treat alkalinity correctly. Given the power of a modern laptop or smart phone there is really no excuse for this imprecision even though it be small in most cases. The real problem it causes is confusion to users of the programs.

What I used to hear was "You don't have to do all that. Most everybodys' water is at pH < 8 and alkalinity = 50*bicarbonate/61 or bicarbonate = 61*alkalinity/50 is close enough. Well everybody's water isn't < 8 especially, it seems, since this Flint business, but that may be confirmation bias on my part.

The problem as I see it is that the programs all want bicarbonate as input when the fundamental parameter is alkalinity. To do mash pH calculations you have to have the alkalinity so the program has, somehow or other, to figure it out from the bicarbonate and pH if the alkalinity isn't given. But quite the other way round the programs want you to tell them the bicarbonate if all you have is the alkalinity.

The issue is that I get a 15% difference in values between the two using the same inputs, and I am fairly certain my pH value is correct (I am using bottled water and so I assume the value is professionally measured and tightly controlled).

I'm not really sure what you are shooting for here. In fact I'm not sure what you are calculating. Is it alkalinity from bicarbonate and pH on a bottled water label or bicarbonate from alkalinity and pH? Post some numbers and I'll do the calcs for you and you can compare to spreadsheets to see which gives the best result. I assume pH is above 8 because below that they all ought to agree.

In the mean time if you would like to send a donation to my new organization CARABAC (Committee for Accurate Representation of Alkalinity in Brewing Application Calculators) let me know and I'll send details.

 

[jdebonth]

Thanks for the elaborate answer.

I was under the impression that the RA is what really drives the mash pH and is what is to be targeted in the water profile based on the beer style. In my case, brewing mainly hoppy pale ales, the main thing I try to do with my water profile is to try and target a RA of 0, whilst keeping the rest of the flavor minerals close enough to my target profile. Should I be focussing on Total Alkalinity as a target instead of RA?

Back to the main question - what I am trying to do is to calculate the Total Alkalinity and RA based on the available info of my brewing water which is: 4.0 Ca, 1.0 Mg, 3.0 Na, 0.8 Cl, 0.4 SO4, 23.4 HCO3, 6.7 pH. What I get from Palmer is a Total Alkalinity of 28, RA of 25, and from Bru'n Water/Kaiser I get a Total Alkalinity of 19 and RA of 16. I realise they are close but just wondering if one is a better approximation than the other. The numbers tend to drift more with other water profiles and after adding salts which makes me unsure where my final corrected profile is at.

 

[ajdelange]

I was under the impression that the RA is what really drives the mash pH and is what is to be targeted in the water profile based on the beer style.

It was noted years ago that the waters of beers of a give style tended to group roughly but the grouping was way to rough to make RA a principle design parameter (which didn't stop some people from trying to do it).

In my case, brewing mainly hoppy pale ales, the main thing I try to do with my water profile is to try and target a RA of 0, whilst keeping the rest of the flavor minerals close enough to my target profile. Should I be focussing on Total Alkalinity as a target instead of RA?

You need to focus on having the totality of the protons absorbed by the alkalinity sources in the water, absorbed by light colored grains, given up by dark colored grains, given up by acids you add and given up when water reacts with malt phosphate sum to 0 at your desired mash pH. Residual alkalinity happens to be the sum of the first and last terms on that list but does not represent the whole story. It is probably best, until this concept becomes more familiar to brewers, to say that you should focus on your mash pH. To do that you will have to use one of the available tools which at this stage in their development deal with the proton balance equation implicitly rather than explicitly.

Back to the main question - what I am trying to do is to calculate the Total Alkalinity and RA based on the available info of my brewing water which is: 4.0 Ca, 1.0 Mg, 3.0 Na, 0.8 Cl, 0.4 SO4, 23.4 HCO3, 6.7 pH. What I get from Palmer is a Total Alkalinity of 28, RA of 25, and from Bru'n Water/Kaiser I get a Total Alkalinity of 19 and RA of 16. I realise they are close but just wondering if one is a better approximation than the other.

The alkalinity for 20 °C and assuming you want the alkalinity as defined by ISO is 20.38 and the RA 16.94. Ward Labs would find 20.87 as they use a lower pH for the end point of the alkalinity titration (4.4 as opposed to the 4.5 used in the ISO procedure). So Kai and Martin are pretty close. The differences between what they get and what I am saying is correct may be because they are not adding on the small but finite (1.5 ppm) alkalinity of the water itself i.e. assuming the akalinity of of the carbonate and bicarbonate is the only akalinity detected in the test. That is the size of the discrepancy. No idea how the Palmer calculation gets to be that far off.

 

[mabrungard]

When performing my empirical studies of mash pH, I did find the RA has a direct influence on mash pH. However, RA is only one part of the equation. The grist also enters into the mix. That is why it is important that brewers forget about targeting RA and focus on the resulting pH.

By the way, Bru'n Water does employ the classic RA formulation to assess the alkalinity of the water and uses it in conjunction with estimates of the mash acidity to predict mashing pH. RA is important, but should not be a targeted value.

 

[jdebonth]

The alkalinity for 20 °C and assuming you want the alkalinity as defined by ISO is 20.38 and the RA 16.94. Ward Labs would find 20.87 as they use a lower pH for the end point of the alkalinity titration (4.4 as opposed to the 4.5 used in the ISO procedure). So Kai and Martin are pretty close. The differences between what they get and what I am saying is correct may be because they are not adding on the small but finite (1.5 ppm) alkalinity of the water itself i.e. assuming the akalinity of of the carbonate and bicarbonate is the only akalinity detected in the test. That is the size of the discrepancy. No idea how the Palmer calculation gets to be that far off.

Thanks for that! Exactly what I was looking for. Is there an easy way I can calculate these myself? Is there an online tool or xls available? Not that it is really needed as Bru'n Water and Kaiser are extremely close. Thanks again.

 

[jdebonth]

By the way, Bru'n Water does employ the classic RA formulation to assess the alkalinity of the water and uses it in conjunction with estimates of the mash acidity to predict mashing pH. RA is important, but should not be a targeted value.

I guess this is the best approximation brewers can make in the planning/recipe design stage. Once the brewing water mixes with the malt bill, pH measurements can then be taken to see how close the predictions were, and then fine adjustments can be made via acid, if needed. Is this the recommended procedure?

 

[ajdelange]

Sure. At the top of the page here you will find a Sticky: https://www.homebrewtalk.com/showthread.php?t=473408. That contains the math for calculating bicarb and carbonate from alkalinity and pH. There's not a lot of explanation there but the key is in the three fractions f1, f2 and f3. Bicarbonate is f2*C where C is the total of carbonate, carbonic and bicarbonate: bicarb = f2*C. If you know bicarb it's easy to get C= bicarb/f2. Once you have C you need to use f2 and f3 to compute the difference in charge C*(Q(pHe) - Q(pHs)) with pHe being the end point of the alkalinity titration (4.5 for ISO) and pHs the sample pH. The charge difference is the alkalinity of the carbo, Add the terms for step 1 and 2 (those are the alkalinites of the hydroxyl and hydrogen ions). Multiply by 50 for ppm as CaCO3. See if you can figure it out and come back with questions. Palmer didn't want to put this stuff in his book despite my efforts to convince him. Pity but it is, after all, his book. Maybe in the 2nd edition.

 

[ajdelange]

I guess this is the best approximation brewers can make in the planning/recipe design stage. Once the brewing water mixes with the malt bill, pH measurements can then be taken to see how close the predictions were, and then fine adjustments can be made via acid, if needed. Is this the recommended procedure?

At first one should use calculation to estimate the mash pH. If the maltsters would furnish acidity data as part of their COAs in the form of a simple table or print it on the bag that would make the calculations a piece of cake. They don't seem to have much interest in doing that though. In any cae someone starting out should prepare, based on the calculations, a small test mash and check it's pH and adjust acid/saurmalz etc based on that. As with many other things in brewing with some experience one knows what to expect and a check of the actual mash pH then suffices.

 

[jdebonth]

Interestingly, Palmer seems to be using your equation in his sheet. Looks like something is going wrong somewhere though.

 

[ajdelange]

Yes but r1 and r2 are a little off. He must be using values of p1 and pK2 from a different source.

 

[jdebonth]

Yes but r1 and r2 are a little off. He must be using values of p1 and pK2 from a different source.

The r1 and r2 are using the same formulae as in your post. Appreciate if you could have a look at my calculations as I am doing something wrong.

I have emailed you an XLS as I cannot attach this file type here.

 

[ajdelange]

I can spot a couple of things from the picture. First, you used exactly 6.38 and 10.30 for the pK's and when I do it I calculate the pKs from a temperature dependent formula and get slightly different values viz. 6.3817 and 10.3756. That doesn't mean we know those pK's to 4 decimal places. That's just how many I display out of the interpolation formula. Second, the charge Q(pHs) = -0.67621 - 2*0.00014 = -0.67649 and similarly Q(pHe) = -0.01301. An extra 1 seems to have slipped in there. This shouldn't matter in the end as you are working with the difference of these two charges.

Now here's where the trouble arises and not for the first time (by which I mean expressing alkalinity "as CaCO3" or worse, "as bicarbonate" does not help people trying to learn this stuff). These calculations are all done in mEq/L. The equivalent weight of the bicarbonate ion is 61 mg/mEq so dividing 23.4 by that you get 0.3836 mEq/L. Put that in there and I think everything should be right.

 

[jdebonth]

Thanks a lot, I'm getting the correct numbers now.

P.s. The email address on your website is bouncing back. I got the error: 550 5.1.1 Recipient not found.

 

[ajdelange]

That explains why I didn't get it then. Which address did you use?

Never mind. You say the one on my website. Well I forgot to pay the bill on that one and so they closed the account. If I knew who they were I'd get in touch and get it opened up again but I don't remember who they are. Of course at my age we consider ourselves lucky if we remember where we live.