A matter of PH (?)?

[BM1]

I have a question concerning the directional references of 'PH'.

If I am manipulating PH level in a substance and am prompted for some reason to lower or raise it,what am I actualy doing?I understand that a PH of 4 is more acidic than 5 with 5 being more basic,but if I have changed my PH from 5 to 4 have I raised it or lowered it.This seems to be a reference that I find in text everywhere(raise PH/lower PH)and somehow I'm missing some clue about how the numbers relate to the terms.

[john mills]

Measurable ph ranges are 0-14. Theoretical ranges are greater, but not practical. To answer your question. Taking your ph from 5 to 4, you have lowered your ph.
Of you want greater in depth explainations of ph see Peter Frederick at the next meeting. He's the expert.

[psfred]

pH is literally the negative logarithm of the hydrogen ion concentration. Water dissociates into a hydrogen ion and a hydroxyl ion (OH-) spontaneously in the pure form, where there are 10-7 hydrogen and hydroxyl ions per liter for a pH of 7. Acid pH means there are more hydrogen ions than hydroxyl ions -- this can only happen when there are other things dissolved in the water.

When you change the pH you are changing the amount of hydrogen ions free in the solution. More acid (lower pH) means more hydrogen ions, higher pH means fewer. It's a bit more complicated than that, of course, but that's the simple answer.

pH is important for a couple of reasons -- low pH inhibits bacterial growth (this is why wine is so stable -- pH is around 3), and the activity of many of the enzymes important in brewing are affected by the solution pH. It's important to have the pH correct during mashing to get the proper enzyme activity.

Peter

[BM1]

Thank you both.That just about clears it up.