distilled water is stored in acidic condition

[padma]

hi,
can anyone tell me the reason why we stored distilled water in acidic condition?

[kmunson779]

I'm not exactly sure what you're asking, but here's a tidbit of information:

Pure water has a pH of 7.0. However, water stored in the presence of air contains dissolved carbon dioxide which forms carbonic acid in solution. Therefore, once it's been stored for a while, even distilled water's pH will drop. For discussion of this, see here and here.

[padma]

hi,
i want to know if we use the ds water once,can we use the remaining distilled water or there is any need to take new one(ds water).if we open the cap of gallon what will be the effect of medium mean to say what will be the effect of CO2 present in air.
padma

[kmunson779]

If you're adding any sort of buffering agent to the water, I wouldn't worry about the pH drop. The whole point of buffers is to prevent pH change.

If you're storing nucleic acids (DNA, RNA) I would strongly suggest using a buffer rather than plain water, for this very reason (pH changes leading to chemical degradation).