[factory]

I just got a bottle of 85% food grade phosphoric acid and I used a spreadsheet to dilute some of it down to a 10% concentration.  When I plugged all of my numbers into Bru'n Water, it says that I need 46ml of 10% acid to bring my mash down to 5.2.  I'm brewing a Blonde Ale, BIAB 4 gallon batch.  5# 2 row, 8 oz carapils, and 5 oz aromatic malt.  yellow balanced profile, with 5.6 gallons of RO water.  I'm also adding 1.5 grams of gypsum and 1.5 grams CaCl.  When using 88% lactic acid, I only have to add 5ml. 

46ml of 10% phosphoric acid seems high to me.  Does it take that much more to move the pH? Or did I do something wrong in the spreadsheet?

[roger]

I have never tried diluting acid. But logically (and maybe too simplistic) it seems you added the equivalent of 46/8.5 ml of undiluted 85% acid. This is about 5.4 ml, which sounds about right to me.

Hopefully someone more knowledgeable will correct me if I'm wrong.

[HydraulicSammich]

Yes, plug in the 85%.  I use it all the time.

[toby]

46ml of 10% phosphoric acid seems high to me.  Does it take that much more to move the pH? Or did I do something wrong in the spreadsheet?

You didn't do anything wrong in the spreadsheet.  You just didn't need to dilute.  You could have just used the 85% in the spreadsheet and probably wound up getting about the same amount called for as 88% lactic.

[mainebrewer]

Looking at your grist and based on my experience with Brunwater, I'd say that 46 mL of 10% phosphoric acid sounds about right.

[klickitat jim]

10% phosphoric additions always freak me out but once you remind yourself that its 10%, in other words 50ml would only be 5ml at 100%... it calms me down

[jjflash]

Which version of Bru'n Water are you using?