The standardization of pH has been achieved in Great Britain 1 , in the United States 2 -5 , and recently also in Japan 6 • In their essential elements, the three standards are in agreement; only differences of detail exist. I t is the object of this report to summarize, for the information of all national groups interested in pH, the extent of standardization already achieved and to indicate how this area of agreement could perhaps be extended to other conceptions related to pH.
SYMBOLSThere already exists international agreement that pH should be written and pr.inted on line in roman type. We recommend that, with the unique exception of pH, the operator p (printed in roman) should denote -log 10 • For example pmHYH,CI pmnYft,CI means -log 10 mu means -log 10 (mHYH,ci) means -log 10 (mHYft,cJ) where m denotes molality and y denotes mean activity coefficient (molality scale).