|
Vol.
25 No. 3
May - June 2003
Measurement
of pH. Definition, Standards, and Procedures (IUPAC Recommendations
2002)
by
R. P. Buck, S. Rondinini, A. K. Covington, F. G. K. Baucke,
C. M. A. Brett, M. F. Camoes, M. J. T. Milton, T. Mussini,
R. Naumann, K. W. Pratt, P. Spitzer, and G. S. Wilson
Pure
and Applied Chemistry,
Vol. 74, No. 11, pp. 21692200 (2002)
The
definition of a "primary method of measurement" has permitted
a full consideration of the definition of primary standards
for pH, determined by a primary method (cell without transference,
Harned cell), of the definition of secondary standards by
secondary methods, and of the question whether pH, as a conventional
quantity, can be incorporated within the internationally accepted
system of measurement, the International System of Units (SI,
Système International d Unités). This
approach has enabled resolution of the previous compromise
IUPAC 1985 Recommendations [Pure Appl. Chem. 57,
531 (1985)]. Furthermore, incorporation of the uncertainties
for the primary method, and for all subsequent measurements,
permits the uncertainties for all procedures to be linked
to the primary standards by an unbroken chain of comparisons.
Thus, a rational choice can be made by the analyst of the
appropriate procedure to achieve the target uncertainty of
sample pH. Accordingly, this document explains IUPAC recommended
definitions, procedures, and terminology relating to pH measurements
in dilute aqueous solutions in the temperature range 550
°C. Details are given of the primary and secondary methods
for measuring pH and the rationale for the assignment of pH
values with appropriate uncertainties to selected primary
and secondary substances.
www.iupac.org/publications/pac/2002/
7411/7411x2169.html
>
later reviewed by Friedrich G.K. Baucke in CI
July 2003
Page
last modified 1 July 2003.
Copyright © 2002-2003 International Union of Pure and
Applied Chemistry.
Questions regarding the website, please contact [email protected]
|