| 释义 |
pH
symbol
the negative logarithm of the effective hydrogen-ion concentration or hydrogen-ion activity in gram equivalents per liter determined in various ways (as by means of a hydrogen electrode or a glass electrode) and used for convenience in expressing both acidity and alkalinity usually on a scale of 0 to 14 on which 7 represents the value for pure water at 25° C or neutrality, values less than 7 represent increasing hydrogen-ion concentration and increasing acidity (as 3.1 for vinegar, 2.3 for lemon juice, and 1.04 for tenth-normal hydrochloric acid), and values greater than 7 represent decreasing hydrogen-ion concentration and increasing alkalinity (as 8.2 for one percent sodium bicarbonate solution, 10.7 for one percent sodium carbonate solution, 13 for tenth-normal sodium hydroxide)
< instead of saying that the concentration of hydrogen ion in pure water is 1.00 × 10-7, it is customary to say that the pH of pure water is 7 — Linus Pauling >
< soils may vary in pH form about 3.5 to 9, but the general range most favorable for ordinary crops is from 6.0 to 7.5 — E.G.Davies >
— compare pk, rh |