Sorry to kind of do a hijack here but it is an interesting conversation and it may fit right in.
So do you have the science on the campden tabs reducing the PH? Sorry to sound like you dont know, damn typing. I have soft water, low in minerals, and high in PH. If the Campden will lower PH and remove Chlorine then it may be something I like. I have also read that Campden tabs will act as an anti-oxidant to help with HSA during the beginning of the mash.
If my water profile will help here is a thread to it.
http://www.aussiehomebrewer.com/forum/inde...showtopic=25058
As far as I understand... Metabisuplhite (S2O5)2- reduces to SO2 and SO3 in solution.
SO2 leaves solution usually or can form (with water) H2SO3, sulfurous acid, and SO3 + H2O = H2SO4 (sulfuric acid).
A chemistry lesson then? I have studied a wee bit of chemistry in my life.......
Firstly, when we refer to chlorine in water we are not talking about Cl2. 'free chlorine' actually refers to HOCl and OCl(-). Chloramine NH2Cl, is also found in town water.
Campden tablets are usually in the form of the potassium salt but for those used to the old homebrew santisers, lets refer to it as sodium metabisulphite (Na2S2O5). If you have the potassium salt, replace Na with K in the reactions below.
Na2S2O5 + H2O --> 2NaHSO3
NaHSO3 + HOCl --> NaCl + H2SO4
So in removing the 'free chlorine' you are generated Na(+), Cl(-) and H2SO4, hence, reducing the pH.
In addition, when you add the campden tabs you arent adding the exact amount required to just remove the free chlorine, you are adding a massive excess.
Whilst i have a decent understanding of chemistry, i am still learning what impact this has on brewing, hence i dont treat my water at all. Robbing peter to pay paul and all that malarky. From the reading i have done on the subject the most important ions in brewing are Ca(2+) and SO4(2-). Adding campden tabs doesnt change the Ca(2+) concentration but it does increase the amount of SO4(2-) significantly as well as reducing the pH.
Oooo, i do love a good chemsitry discussion and one that involves beer is even better.
Cheers
DrSmurto - uber nerd