Not pH, but TA.
3.8 grams Tartaric Acid per US Gallon raises TA by + 1 g/L (or .1%)
It will also usually lower the pH. But it is NOT linear or equivalent to TA.
Each wine's unique make-up will cause it to respond to the acid adjustment in a unique way when making additions to the pH and TA. Two different wines with the same exact pH and TA will respond differently to an equivalent acid addition. Yes, the numbers are important, but ultimately, they only give you an idea of the boundaries you're working in, not absolute answers. A good analogy for this is thinking about driving at night: Not testing your pH is like driving in the dark with your headlights off- you have no idea which direction you're going. Testing not only illuminates the road ahead, but it also lights up the reflectors and paint lines. You can see where you are going along with the boundaries that promote safe driving. Furthermore, since it is quite difficult to know how any must or wine will react to an acid addition, I cannot express enough that it is always best to add a portion of the amount you think you need, then taste and test to be sure. It is very easy to overdo things. With a patient and measured approach, you'll be saved from having to fix an over-correction.
Once you have tasted the partial addition, you can decide if the rest will be needed.
