What chemistry and campden tablets

[ArrivaTrainsNorthern]

I've been using a quarter of a Campden tablet (sodium metabisulfite) to remove chlorate from my brewing water. How should I adjust my water chemistry calculations for this compound? Does it affect pH? How much sodium per tablet? Do I need to worry about the sulfite from a water chem point of view?

 

[TheMadKing]

I've been using a quarter of a Campden tablet (sodium metabisulfite) to remove chlorate from my brewing water. How should I adjust my water chemistry calculations for this compound? Does it affect pH? How much sodium per tablet? Do I need to worry about the sulfite from a water chem point of view?

Basically no to all of the above questions... perform your salt additions without worrying about it. I asked the same question awhile back, and Martin explained it to me, that yes it does add some sulfite but it's minimal so effectively zero. There is no sodium in it unless as an impurity, it's K2S2O5

 

[ArrivaTrainsNorthern]

Hi, thanks for this. Campden tablets can be either sodium or potassium metabisulfite and in this case I have sodium metabisulfite. Unfortunately the packaging doesn't give any information on how much sodium there is per tablet or per gram or whatever.

Still, good to hear I don't have to worry about pH!

 

[invictusbrew]

Basically no to all of the above questions... perform your salt additions without worrying about it. I asked the same question awhile back, and Martin explained it to me, that yes it does add some sulfite but it's minimal so effectively zero. There is no sodium in it unless as an impurity, it's K2S2O5

While I agree that the numbers added are indeed negligible (based on my reading and understanding of the subject), Campden tablets come in two forms: potassium metabisulfite (K2S2O5 as you brought up) and sodium metabisulfite (Na2S2O5), both are commonly available for the homebrewer in the form of campden tablets.

EDIT: Also, there is approximately .44g of sodium metabisulfite in one campden tablet, .11g in 1/4 of a campden tablet. While it has been quite some time since I took a chemistry class, I believe one could use the given information to figure out rough amounts of each element?

 

[ajdelange]

Ten posts above this one is a rather complete discussion of what remains in water treated with campden tablets depending on whether they are the potassium or sodium salt and on the form of the chlorine being removed. As apparently navigating that far is a challenge here's a link: https://www.homebrewtalk.com/showthread.php?t=361073