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ERIC Number: EJ913045
Record Type: Journal
Publication Date: 2010-Jan
Pages: 3
Abstractor: As Provided
Reference Count: 13
ISSN: ISSN-0021-9584
One-Hundred Years of pH
Myers, Rollie J.
Journal of Chemical Education, v87 n1 p30-32 Jan 2010
The idea of expressing the hydrogen-ion concentration on a log arithmetic scale was presented by S. P. L. Sorensen in 1909. The symbol that he used was the letter p and a smaller H appearing almost as a subscript. Typographical convenience led journals to adopt the current symbol. It has been common to assume that the p represented a word such as power, but in 2000, it was asserted that the p came from the way that Sorensen designated the cells that he used to measure pH. Biological workers quickly adopted the pH symbol to specify buffer conditions, but chemists were slow to adopt it. Today this symbol is widely used, and the little p has assumed a life of its own. We trace some of the history of buffers, indicators, and the pH meter. We also show the slow incorporation of pH into "Chemical Abstracts" and into Introductory Chemistry in Berkeley. The modern definition of pH is a purely operational one. Buffers that have been carefully calibrated to closely follow the activity of the hydrogen ion are used to standardize pH meters, and these meters are then used to interpolate between these standards. The teaching problems caused by the definition pH in terms of a single-ion activity are also discussed.
Division of Chemical Education, Inc and ACS Publications Division of the American Chemical Society. 1155 Sixteenth Street NW, Washington, DC 20036. Tel: 800-227-5558; Tel: 202-872-4600; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A