Treating water with seperate acids

While Beer is 90-97% water, it is a very tricky subject.

Treating water with seperate acids

Postby london_lhr » Wed Apr 12, 2017 17:27

I wish to treat my brewing water with seperate acids and I have 25% sulphuric acid and 28% hydrochloric acid.
How much would 1ml of sulphuric acid per 1 litre of water reduce alkalinity and how much would 1ml of the hydrochloric acid per 1 litre of water reduce the alkalinity?
What would the calcium, sulphate and chloride contributions be to 1 litre of water per ml of of each acid used?
I intend just using this in a simple spreadsheet with the alkalinity reduction and the brew length.
Thanks in advance.
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Re: Treating water with seperate acids

Postby Aleman » Thu Apr 13, 2017 06:54

The issue is "Is the strength of the acid what it says it is?" You say 25% but is that v/v, v/w, or w/w? The difference is considerable.

I usually test my acids. So take 10litres of water, measure the alkalinity, add 1ml of acid, and remeasure the alkalinity. That way it matters not what the quoted strength is I know how much alkalinity 1ml will remove.

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Re: Treating water with seperate acids

Postby london_lhr » Thu Apr 13, 2017 15:17

Thanks Aleman.
Unfortunately I don't know which one it is, v/v, v/w, or w/w as I was given the acids.
It would probably be prudent to get some concentrated acids (98% and 36%) and dilute them appropriately.
If I dilute to Molar, what M concentration would be best for brewing purposes?
Thanks.
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Re: Treating water with seperate acids

Postby Aleman » Thu Apr 13, 2017 16:12

Do you have an alkalinity test kit? If so it is simple to determine the actual strength of your acid.

1) Measure 10Kg of water into a container
2) Measure the alkalinity
3) Add 1ml of your acid
4) stir and leave covered for 30 minutes
5) stir again
6) Measure the alkalinity

Hopefully you would have a significant (>50mg/l) change in alkalinity, but if not repeat steps 3-6 again. Once you have those values post them here and I'll run them through my spreadsheet to tell you what the Molarity of the acids is. In fact noting that you are in the Dengie you can probably get away with just 5Kg of water for the test. I have to use 10L, AND, dilute the acid 1 in 10!

Actually, if you do know the strength of the acids, they should be used in conjunction with an alkalinity test kit, even if just after treatment to determine the final alkalinity value.

When I'm diluting acids to 'bench strength' I use 2Molar for HCL and 1Molar for Sulphuric that way the acids have the same neutralising power WRT Alkalinity (sulphuric being diprotic, and hydrochloric being monoprotic)

please note:The use of punctuation, bold, underlining, italics, and different sized type, follows the convention used in writing, for many years, to place emphasis on the point being made, and to highlight the importance of that point in the opinion of the author. It is not the intention of the author to shout, if that was the case the author would adopt the, much more recent, convention of using all capital letters.
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Re: Treating water with seperate acids

Postby london_lhr » Thu Apr 13, 2017 17:34

My initial post should have read that I have access to the acids!
Rather than mess around, I will order 1M sulphuric and 2M hydrochloric acid.
How do you calculate the alkalinity reduction in mg/l of an acid?
Thanks.
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Re: Treating water with seperate acids

Postby Eric » Thu Apr 13, 2017 19:08

london_lhr wrote:My initial post should have read that I have access to the acids!
Rather than mess around, I will order 1M sulphuric and 2M hydrochloric acid.
How do you calculate the alkalinity reduction in mg/l of an acid?
Thanks.


As Aleman described.
You will still run a risk of the acids not being precisely to specification for nearly all acids you can easily obtain.
1 mole of sulphuric acid or 2 moles of hydrochloric acid will neutralise 1 mole of (alkalinity as) calcium carbonate.

It is not good practice to add a certain amount of acid without checking what effect it had, or on the presumption it reduced alkalinity by a specific amount. You should first measure how much alkalinity exists before treatment and how much remains after. The liquor should then have the correct level of alkalinity for your brew and eliminate the possiblity of having too much or worse, adding excess acid to your HLT and MT.

As Aleman has advised, use a Salifert kit to measure how much a given volume of acid reduces alkalinity in a given volume of your water to calculate its strength. Then on brew day measure alkalinity to then determine the amount of alkalinity to be neutralised. After treatment check the result and adjust if necessary. It is simpler to calculate the influence on sulphates and chlorides by reference to the reduction in alkalinity than by amount of acid used, for it matters not what strength the acid is. For every 10ppm reduction of alkalinity as calcium carbonate by sulphuric acid increases sulphates by 9.6ppm or with hydrochloric increase chlorides by 7.1ppm.

There will be no change to calcium levels by adding acid, for that you will need to add calcium salts.
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Re: Treating water with separate acids

Postby london_lhr » Thu Apr 13, 2017 19:49

Thank you Eric.
The idea of using a spreadsheet is to at least get an idea of how much acid to add to reduce a given amount of alkalinity.
I do agree that one would need to check the alkalinity before and also after treating the water.
I do use the Salifert kit for testing alkalinity and I also test for calcium to get an idea of the amount of salts to add to achieve a particular level of calcium.
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Re: Treating water with separate acids

Postby Eric » Fri Apr 14, 2017 12:41

london_lhr wrote:Thank you Eric.
The idea of using a spreadsheet is to at least get an idea of how much acid to add to reduce a given amount of alkalinity.


That is clear, but while in theory the answer appears straightforward, in practice it might not and is why there is reluctance to give a straight answer from what might be on the label. Our considered advice is first buy your acid and test its strength, Aleman has offered to do the calculations for you.

Four years ago I bought sulphuric acid from a very well known supplier to the brewing industry. The label was marked 25% w/w and their advice was that 1ml would neutralise 297mg of calcium carbonate. I found 1ml neutralised 440mg of calcium carbonate and this is not the only known case, indeed it is quite common.

london_lhr wrote:I do agree that one would need to check the alkalinity before and also after treating the water.
I do use the Salifert kit for testing alkalinity and I also test for calcium to get an idea of the amount of salts to add to achieve a particular level of calcium.


Doing the test is no more difficult than doing the Salifert test you describe. Take a known volume of water of measured alkalinity, add 1ml of the chosen acid and allow the reaction to complete. Re-measure alkalinity and subtract that from the initial value, both measurements in mg/l as calcium carbonate. Multiply that result by the number of litres of liquid present to give the amount of calcium carbonate 1ml of that acid will neutralise. Job done.
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