by johngaltsmotor » Tue Feb 18, 2014 7:52 pm
As herjac says, it is the total number of ions. While DI water contains a large volume of a neutral pH, it is low in total ions so it has little buffering ability. So adding a little bit of anything with a different pH makes a difference. So when you mix DI water with meat the acidity of a little meat is able to overpower the neutrality of the water.
You can think of pH as indicating the ratio of OH (base) to H (acid). However, when you mix things you need to calculate the new ratio based on the total # of ions again, not just averaging the ratios.
So mixing volume A containing 1 OH and 1 H with volume B containing 40 OH and 50 H means you get a 41 OH : 51 OH end result which is essentially the same as B itself. (similar to meat in DI water)
So DI water would be low buffering (1:1) while hard water would be higher buffering (20:20), but both could have a neutral pH if the ratio of OH and H is the same (1:1 = 20:20 when it comes to measuring pH but not when it comes to buffering).
(hopefully that helped and didn't just confuse things more)
Pigs are magical creatures.... they turn vegetables into BACON!!