Author Topic: Phosphoric acid to adjust pH  (Read 2572 times)

Offline factory

  • Brewer
  • ****
  • Posts: 270
  • Virginia Beach, VA
    • View Profile
Phosphoric acid to adjust pH
« on: December 28, 2015, 02:09:44 PM »
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?

Offline roger

  • Cellarman
  • **
  • Posts: 29
    • View Profile
Re: Phosphoric acid to adjust pH
« Reply #1 on: December 28, 2015, 02:25:36 PM »
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.
Cheers,

Roger

Offline HydraulicSammich

  • Assistant Brewer
  • ***
  • Posts: 179
  • Logan, UT
    • View Profile
Re: Phosphoric acid to adjust pH
« Reply #2 on: December 28, 2015, 02:35:29 PM »
Yes, plug in the 85%.  I use it all the time.
AHA Member 900001775

Offline toby

  • Senior Brewmaster
  • ******
  • Posts: 1021
  • Galvez, LA
    • View Profile
    • Beer Judge Chronicles
Re: Phosphoric acid to adjust pH
« Reply #3 on: December 28, 2015, 04:18:42 PM »
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.

Offline mainebrewer

  • Brewer
  • ****
  • Posts: 434
  • Palermo, Maine
    • View Profile
Re: Phosphoric acid to adjust pH
« Reply #4 on: December 28, 2015, 09:28:46 PM »
Looking at your grist and based on my experience with Brunwater, I'd say that 46 mL of 10% phosphoric acid sounds about right.
BJCP Certified

Offline klickitat jim

  • I must live here
  • **********
  • Posts: 8604
    • View Profile
Re: Phosphoric acid to adjust pH
« Reply #5 on: December 28, 2015, 10:20:15 PM »
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

Offline jjflash

  • Assistant Brewer
  • ***
  • Posts: 155
  • New Mexico
    • View Profile
Re: Phosphoric acid to adjust pH
« Reply #6 on: December 29, 2015, 04:19:21 AM »
Which version of Bru'n Water are you using?
---JJ---

I don't know half of you half as well as I should, and I like less than half of you half as well as you deserve.
- Bilbo Baggins