In chemistry, pH was the measure of the acidity or basicity of an aqueous solution.
Baking soda had a pH higher than seven. Beckett Mariner requested it or anything similarly basic to neutralize the blood acid on her uniform shirt. (LD: "The Inner Fight")
In 3189, an atomic scan performed on Philippa Georgiou's respiratory system revealed that her blood base had a pH of 7.41. (DIS: "The Sanctuary")