K-Meta, Na-Meta pH properties?

[VikeMan]

Figured I'd ask here, since they are pretty much a LODO thing...

My understanding is that Na-Meta solutions are acidic, but I know nothing of their buffering capacity. Anyone know more about the pH properties of K-Meta and/or Na-Meta? Have you modelled them in mash pH prediction tools? Is the impact big enough to move the needle? TIA!

 

[dmtaylor]

I don't have specifics, other than to say that bisulfite (regardless of Na or K) is a very weak acid in these very low concentrations. Sure, if you added pounds of it to your beer, you'll detect the acidity. But in tiny ppms, I don't think it's enough to be concerned about. A reduction of 0.05 pH unit is probably conservative for our purposes but I expect the real number might be closer to 0.005. But this is only an educated guess. I do not consider myself to be a "real" water expert. Somebody else much smarter than I will come along soon and overrule me and that's fine, I'm cool with that.

B.S. Chemical Engineering, Michigan Tech 1997, yadda yadda

 

[VikeMan]

^This is what I want to believe, i.e. something on the order of 0.005 in an "average" mash when building to, say, 30 ppm. But if it's more than that, I'm hoping someone has already analyzed it in way that can be modelled.

 

[9Kegs]

PH Drop = ( PPM Metabisulfite / 100 ) * 0.1

 

[VikeMan]

PH Drop = ( PPM Metabisulfite / 100 ) * 0.1

How was this determined, if you know? Thanks!

ETA: I assume that's some sort of average?

 

[9Kegs]

It's from Methods of the **************** - The ****************
Metabisulfite reduces pH by 0.1 per 100 ppm:
I do not know how it was determined.

 

[VikeMan]

It's from Methods of the **************** - The ****************
Metabisulfite reduces pH by 0.1 per 100 ppm:
I do not know how it was determined.

Thanks. The exact value for any given mash would have to be dependent on the baseline pH and buffering capacity of the mash. That's why I wonder if it is some sort of average. @Big Monk any insight?

 

[Big Monk]

Thanks. The exact value for any given mash would have to be dependent on the baseline pH and buffering capacity of the mash. That's why I wonder if it is some sort of average. @Big Monk any insight?

Originally, the folks who wrote the original GBF Helles paper, of which Die Beerery was a founding member, observed a 0.1 pH drop per 100 ppm.

Upon further investigation this year, I was able to factor it in to my charge balance equation by doing the chemistry. It’s actual a little more than 0.1 pH for both Na and K Meta.

I believe I used the acid characteristics and pH dependence of Sodium and Potassium bisulfite to match the empirical drop in pH.