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Residual Alkalinity - LaMotte vs Palmer

Trying to make sense of results from the LaMotte BrewLab and use in them in a
spreadsheet calculators like John Palmers.

Specifically, I am getting seemingly different results for Residual Alkalinity.

Measured values from the LaMotte kit (all "as ppm CaCO3’):
Total Alkalinity = 120
Calcium Hardness = 70
Magnesium Hardness = 30

Using the LaMotte equation I get 96.
Using the Palmer spreadsheet I get 52.

I’ve attached screenshots of both.

Can anyone determine what is right or wrong?

Palmer has always had problems with alkalinity. I don’t know if they’ve been fixed. Compare to Bru’nwater. If Palmer is the same, great. If not, believe Bru’water.

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I’m thinking perhaps the LaMotte formula is in error as Palmers seems to agree with Brun Water:

Trying to pay attention to using the proper units.
No RDWHAHB here ;(

Well, there ya go…if Bru’nwater says it, you can believe it.

I think my confusion comes from not understanding the right units to use in each formula.

In Palmers spreadsheet, The “Total Alkalinity” and the “Residual Alkalinity” are shown in terms of “as CaCO3” but for “Calcium (ppm)” and “Magnesium (ppm)” the values that have to be entered are the Ca2+ and Mg2+ ions, not their CaCO3 equivalents. I assumed all variables in Palmers formula would use the same units.

The LaMotte formula uses the CaCO3 value for all variables.

At the end LaMotte and Palmer agree, with Brun Water providing the assist:

Thanks for listening Denny!

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As mentioned above, the Ca and Mg are presented as ‘CaCO3’. But to use them in the Palmer equation, those Ca and Mg hardness values have to be converted to their true Ca and Mg concentrations. Bru’n Water has converters to make that conversion easier.

To get to the true concentrations, I’ve read in Mn water manual, the use of 2.5 x Ca… and 4.12 x Mg… Are these equations applicable? As I tried them with the above data, I was no where near the sums… Sneezles61

Thank you Martin.
The detailed background information in Brun Water regarding the residual alkalinity equation was the “aha” moment for me in regard to using the right units within a given equation.

I think you’re hitting the same bumps in the road as I did.
The conversion factors you mention of 2.5 and 4.12 appear to be the inverse of 0.4 and 0.24 as in:

Calcium hardness (ppm as CaCO3) x 0.4 = CA+2 ion concentration
Magnesium hardness (ppm as CaCO3) x 0.24 = Mg+2 ion concentration

I’ve seen two forms of the residual alkalinity equation…each using different units.

The Lamotte equation I cited uses “ppm as CaCO3” as the unit for all of its variables…the Palmer equation, while correct, is mixing “as CaCO3” and ion concentration units.

I can’t claim I know how to fight my way out of this wet paper bag, yet, I do my best to wrap my head around the basics of water, mash, and malts… I try do the equations and my answers don’t match… So I read some more… I get different info from just about every piece I read… This really can’t be complicated, or perhaps… doesn’t need to be… BUT, there is little candle flickering in my mind that wants to know… :disappointed: Sneezles61

Wet paper bag…good analogy. I have been brewing many years and only now have I decided to get into water adjustment. As I look back I can recall a number of incremental steps towards improving my brewing…finally went all grain only about two years ago. Water chemistry is daunting and can be somewhat of a rabbit hole. There is a position of, you can brew good beer w/o treating your water, though the type of water where you are might lend itself to certain styles…i.e. Malt forward, hop forward., etc. If you haven’t tried these sources for water knowledge, is pretty good, and is excellent and deep. Lots of good beersmith podcasts on youtube - I listen while commuting. For me I keep listening, re-reading and chipping away, trying to mine the practical aspects. Never give up, never surrender :!

My bad…forgot to include “Bru’n Water” which is an excellent resource.

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I have been reading the WATER book, I too was Kia’s braukaiser… I’m not good at getting a computer to do stuff for me, so I tend to keep things a bit simpler… Along my path of home brewing, there has been many changes… most of them for the good. Water is my focus now, and has been for a year… I’m able to manipulate it for pH… and getting somewhat comfortable altering for malt or hoppy brews… I’ve not done any reading about the barley side of brewing yet… Another piece of the puzzle…
I feel fortunate to be able to interact with many peeps on this forum to help guide me to my level of brew I’m at today… I still have questions, and find the answer, piece by piece right here… Thank you all! Sneezles61

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