Siggaard-Andersen O
Scand J Clin Lab Invest Suppl. 1977;146:7-13. doi: 10.3109/00365517709098926.
It has been recommended to use SI units in clinical chemistry. A consequence of this is that pH is reported as the excess chemical potential (or standard chemical potential) of hydrogen ions with the unit kJ/mol. On the basis of the excess chemical potential of H+ it is possible to calculate the hydrogen ion concentration in the system = the equilibrium concentration of H+ = the concentration of free H+. This quantity must be clearly distinguished from the stoichiometric concentration of H+ = the excess concentration of total H+, which indicates the amount of added or removed H+. The latter quantity with opposite sign has been called the excess concentration of base, but the designation "stoichiometric concentration of H+" seems to be more logical. The general principles for description of a component in a chemical system are based on (1) an extensive quantity (the stoichiometric amount of substance), and (2) an intensive quantity (the excess chemical potential); the product of these has the dimension of energy.
临床化学领域建议使用国际单位制（SI）单位。这样做的一个结果是，pH值以氢离子的过量化学势（或标准化学势）来表示，单位为kJ/mol。基于H⁺的过量化学势，可以计算系统中的氢离子浓度 = H⁺的平衡浓度 = 游离H⁺的浓度。这个量必须与H⁺的化学计量浓度（即总H⁺的过量浓度）明确区分开来，H⁺的化学计量浓度表示添加或去除的H⁺的量。后一个带有相反符号的量被称为碱的过量浓度，但“ H⁺的化学计量浓度”这一名称似乎更符合逻辑。描述化学系统中一种成分的一般原则基于：（1）一个广延量（物质的化学计量量），以及（2）一个强度量（过量化学势）；这两者的乘积具有能量的量纲。
