The body naturally keeps a proper pH balance if you give it the supplies it needs - minerals from fruits and vegetables - and don't overload it with acid-forming proteins.
Basically the way your pH balance works is if we eat a natural diet of fruits and vegetables with whole grain and a little meat, our body will be able to do what it needs to do and find that balance.
Our body will pull the minerals out of the fruits and vegetables and use them to balance the acid in our body fluids.
If we do not get enough fruits and vegetables, we are likely filling up on grains and meat - which are very acid forming in our bodies.
The body must keep the blood pH within a very narrow range around 7.35-7.45 and will keep it there at all costs. If it were to get off even a little, we would die. That is very rare because the body is so good at finding a way to alkalize despite eating a constant acid diet.
The urine, though, is another story. It should be a pH balance of about 6.8 throughout the day and, for most of us, it drops over night so the morning pH may be as low as 6.0.
Some collect all urine for 24 hrs to see what the average is. You can just check it each time you go all day and get an average that way. It doesn't have to be exact, just within the ballpark. (If you keep a gallon in your refrigerator all day be sure to label no drinkable;)
So what happens is... when the body needs to alkalize the urine, so that it wont burn up our urinary tract, it uses minerals from our foods. If we haven't eaten any fruits or vegetables to supply minerals, it goes to the reserves.
The first place it often goes to get minerals is from the bile made in the liver. It will pull the minerals right out of the gallbladder through the tissue. This will leave the other ingredients in the gallbladder too concentrated and no longer alkaline enough - so they form into stones.
Another place it pulls minerals from is our organs or bones (calcium) or even our muscles (magnesium).
If it can't find anything to neutralize the acid, it will store some excess acid in tissues, joints, muscles and arteries. (arthritis, gout, etc.)
Taking minerals will help neutralize the acid. Plus, it takes a while, but it will slowly replenish the mineral stores in your organs and bones.