The measurements check out on strange-Steve’s formulae and also my friends. I think I’m going to give it a try at these doses.
Apologies, strange-steve. I think I am trying to run before I can walk on this.
I've heard in the past that the dosages recommended by Murphy's tech sheet for AMS/CRS has been off, so I wouldn't be surprised at this. I've never used it or phosphoric acid so I have no personal experience with them, but I recommend that a test should be done to determine alkalinity reduction by anyone using them.Given that the Murphy's 75% Phosphoric Acid technical sheet seems to indicate a need for in the neighborhood of twice as much acid addition for any given task as I had computed, I have spent the better part of the day evaluating all of the mash and sparge pH adjustment spreadsheets and online calculators I could gather together to see what they were calculating. They are all in close agreement with my method, and not one of them comes close to agreeing with Murphy's.
pH sticks which are only capable of pH 4.6 at the low end may not reveal how low adding nearly twice as much acid is potentially dropping the pH, since anything below 4.6 will still read as 4.6.
OK so let's assume you're brewing an IPA. For this you might want a water profile something like this:
Calcium ~160ppm
Sulphate ~250ppm
Chloride ~50ppm
Alkalinity ~30ppm
This means you want to add roughly 50 calcium, 200 sulphate, 25 chloride, and remove 340 alkalinity. Note these are all approximate, don't be too worried about being a few ppm out, and it's not always possible to get your desired profile.
An addition of 0.35g/l gypsum will add 195 sulphate and 80 calcium.
An addition of 0.05g/l calcium chloride will add 24 chloride and 14 calcium.
An addition of 1.05ml/l of phosphoric acid will remove 340 alkalinity.
Those additions will give the following profile:
Calcium 201ppm
Sulphate 208ppm
Chloride 48ppm
Alkalinity 30ppm
Which actually isn't half bad.
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