Pre-measured and mixed salts? - Page 2 - Home Brew Forums
Register Now For Free!

Home Brew Forums > Home Brewing Beer > Brew Science > Pre-measured and mixed salts?

Thread Tools
Old 12-05-2012, 03:29 PM   #11
Mar 2011
Olympia, Washington
Posts: 461
Liked 17 Times on 13 Posts

Originally Posted by mabrungard
Those calculations are easily accessible to any brewer via the Bru'n Water software.
Thanks, AJ and Martin. I'm just starting water adjustments (one batch so far) but I've followed the guidance in Bru'n Water.

Reply With Quote
Old 03-15-2016, 05:40 PM   #12
Brewniversity student
philipCT's Avatar
May 2013
, Connecticut
Posts: 769
Liked 157 Times on 115 Posts

Waking a dead thread here because I'm consistently seeing a strange issue balancing the pH of my sparge water, and this issue seems to belong here.

Background: I use the Brunwater spreadsheet to great effect balancing my mash - whether it's a lager or a porter - really great. I brew on a 3-vessel HERMS system and always start with 12 gallons of sparge water in the HLT regardless of how much I intend to use (most often with a 10g batch I use most of it). I use the Hanna pHep meter with a good/new probe.

I always add the prescribed amount of salts and acid to the sparge and let it mix/recirculate for at least 10 minutes during the temperature ramp to mash-out 170F. What I've noticed is that if I add, say, 1.3cc, and then extract, cool and measure a sample pH at something like 6.2, I want to add a little additional lactic to bring the down to 5.6-5.8. If I then add 0.2cc, wait 5-10mins, extract, cool and measure a new sample, it will have dropped dramatically to something like 4.7 all of a sudden.

Can anyone explain this weird phenomenon? Is the changing temperature of the sparge water affecting the pH (keeping in mind I cool all samples to room temp before using my pH meter)?

Reply With Quote
Old 03-15-2016, 09:27 PM   #13
Aug 2010
McLean/Ogden, Virginia/Quebec
Posts: 9,415
Liked 1559 Times on 1185 Posts

In going from pH 5.7 (I'll use the average) to pH 4.7 the charge on 1 mmol of carbo (the carbonic, bicarbonate, carbonate system) changes Qc(4.7) - Qc(5.7) = 0.156 mEq/mmol. As 88% lactic acid is about 11 N (each cc releases 11 mEq protons in going to pH's near 5) then the carbo level must be
0.2*11/0.156 = 14.1 mmol (for the whole 12 gal).

So we have 0.2*11/(Qc(4.7) - Qc(5.7) ) = 14.1 for this second change in pH. For the first change you used 1.3 mL of acid which has normality of about 11.7 N (because the pH is a bit higher) and the same formula applies:
1.3*11.7/(Qc(5.7) - Qc(pH?) ) = 14.1 mmol
because the amount of carbo is the same but now the shift is from pH? to 5.7. It doesn't take long to figure that pH? = 9.92 and so if the water you started with had a high pH (even if not as high as 9.92 because we are being pretty approximate) then everything is quite normal. Now, OTOH, if you started with water at pH 7 then things aren't kosher here.

Reply With Quote
Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
Leaf Hop Absorption Measured ChemE Recipes/Ingredients 29 08-13-2014 02:44 PM
Is fermentation complete? When is F.G. measured? D_Nyholm Cider Forum 4 12-24-2011 02:48 PM
Uh Oh, mis-measured! Turfmanbrad Beginners Beer Brewing Forum 2 09-25-2011 02:06 PM
Under-measured water.. what effects will this have? Looper General Techniques 7 04-25-2011 04:13 AM
Measured OG higher than estimated Frodo Brewing Software 2 11-18-2009 05:09 PM

Forum Jump