How precise can I target the pH of my water with phosphoric acid 10%?

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Finlandbrews

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Interesting to read that Gordon strong treats his water with 1/4 tsp phosphoric acid 10% to get his brewing liquor (water to brew with) around 5.5 pH when measured at 20 degree celsius which is about 70 Fahrenheit.

For some reason there is no indication of his untreated water pH.

This leads me to question:

1) is the amount of phosphoric acid 10% that is needed for reaching pH 5.5, independent of the pH of the original/untreated water he uses?

2) can we make an estimate of how many ml of phosphoric acid 10% will I need in order to reach pH 5.5 if my water has a pH of 8.3?

3) why do I hear water pH is not important when a triple ninkasi award winning homebrewer and master judge is focusing on changing the pH of his water in every beer he does?

Thank you for clarifying. Cheers
 
What water pH would he get after his RO treatment? I wish to calculate my acid addition too in order to get there before my mash. Thanks
 
Interesting to read that Gordon strong treats his water with 1/4 tsp phosphoric acid 10% to get his brewing liquor (water to brew with) around 5.5 pH when measured at 20 degree celsius which is about 70 Fahrenheit.

For some reason there is no indication of his untreated water pH.

This leads me to question:

1) is the amount of phosphoric acid 10% that is needed for reaching pH 5.5, independent of the pH of the original/untreated water he uses?

It depends on the pH of the water and the total amount of bicarbonate/carbonate/carbonic dissolved in it. All that is usually rolled into a single number, the alkalinity. If the alkalinity is known then it is not necessary to know the pH. As has been noted Gordon has a friend who supplies him with all the RO water he needs. The alkalinity of RO water is very small as there is little dissolved in it. Pure water at pH 5.5 contains 1000*10^-5.5 = 0.00316 mEq/L hydrogen ions and that is how much acid needs to be added to pure water to reach pH 5.5.

1/4 tsp of 10% phosphoric acid which is about normal at mash pH yields 5/4 = 1.25 mEq. Put into 20 L of water that would give 1.25/20 = 0.0625 mEq/L which would result in a pH of about -log(.0625/1000) = 4.2. Apparently, thus, the alkalinity of Gordon's RO water is not 0 but somewhat higher (to be expected as RO does not remove 100% of anything)

2) can we make an estimate of how many ml of phosphoric acid 10% will I need in order to reach pH 5.5 if my water has a pH of 8.3?

We would also need the carbo content or, absent that information, just the alkalinity (from which we can calculate the carbo content and thus the required acid).

3) why do I hear water pH is not important when a triple ninkasi award winning homebrewer and master judge is focusing on changing the pH of his water in every beer he does?
pH information is not needed if and only if you know alkalinity.

What water pH would he get after his RO treatment? I wish to calculate my acid addition too in order to get there before my mash.
I would guess he gets 5.5 because I am sure he has determined the amount of acid required to get that for his particular RO water. As noted above were he using DI water it would be closer to 4.2. for you to determine the amount of acid needed you will have to get alkalinity information or experimentally add acid to a sample of your water to see how much it takes to get a liter of it to 5.5. Note that this is effectively measuring the alkalinity.
 
Welcome back AJ! I take it the construction project is wrapped up and you are back in VA?
In order: no and yes. Construction will proceed but without me there to get uptight about everything little thing I see that doesn't look right. I'm guessing general and subs all went to the nearest bar to celebrate when they saw us pull out of the driveway
 
It depends on the pH of the water and the total amount of bicarbonate/carbonate/carbonic dissolved in it. All that is usually rolled into a single number, the alkalinity. If the alkalinity is known then it is not necessary to know the pH. As has been noted Gordon has a friend who supplies him with all the RO water he needs. The alkalinity of RO water is very small as there is little dissolved in it. Pure water at pH 5.5 contains 1000*10^-5.5 = 0.00316 mEq/L hydrogen ions and that is how much acid needs to be added to pure water to reach pH 5.5.

1/4 tsp of 10% phosphoric acid which is about normal at mash pH yields 5/4 = 1.25 mEq. Put into 20 L of water that would give 1.25/20 = 0.0625 mEq/L which would result in a pH of about -log(.0625/1000) = 4.2. Apparently, thus, the alkalinity of Gordon's RO water is not 0 but somewhat higher (to be expected as RO does not remove 100% of anything)



We would also need the carbo content or, absent that information, just the alkalinity (from which we can calculate the carbo content and thus the required acid).


pH information is not needed if and only if you know alkalinity.

I would guess he gets 5.5 because I am sure he has determined the amount of acid required to get that for his particular RO water. As noted above were he using DI water it would be closer to 4.2. for you to determine the amount of acid needed you will have to get alkalinity information or experimentally add acid to a sample of your water to see how much it takes to get a liter of it to 5.5. Note that this is effectively measuring the alkalinity.

Thank you ajdelange! So my alkalinity is 0.51 mmol/L at 8.7 celsius degree. So now that I know that, can I know exactly how much phosphoric acid 10% or 75% do I need to add to reach water pH 5.5? I was told that my alkalinity is about 25 ppm/L.

On the third column is the water report for my tap water.

View attachment 1448759884059.jpg
 
Well you can't know exactly because the alkalinity and pH of the water that come from your tap will not be exactly those in your water report nor will any phosphoric acid you buy be exactly of the labeled strength. This is why it is best to determine the required amount experimentally. To do this one should have an approximate number and that can be calculated using the algorithm at http://wetnewf.org/pdfs/Brewing_articles/Water_acidification.html.
 
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