Role of reference materials for the realization of physicochemical
properties. Past, present, and future*
Kenneth N. Marsh
Department of Chemical and Process Engineering, University
of Canterbury, Christchurch, New Zealand
Abstract: Reference materials have long been considered essential
for both calibration and checking the correct operation of equipment
used for the determination of physicochemical properties. Up until the
1970s, the maintenance of pure reference materials and the means to
verify their properties through measurement using state-of-the-art equipment
was the prerogative of many national standards laboratories. Over the
last 30 years, many of the standards laboratories have either limited
or eliminated their activity in maintaining both reference materials
and state-of-the-art measuring equipment. One reason is the ready availability
of high-purity materials from commercial sources and the ease with which
one can now determine purity. A second reason is the ready availability
of instruments to measure digitally fundamental quantities such as time,
temperature, length, frequency, and voltage accurately has enabled chemical
calibration using reference materials to be replaced in many instruments
by electrical calibration. At the same time, digitization has enabled
the computerization of the whole measurement process. Such automated
devices, if not checked with reference materials, can give highly reproducible
results but have large systematic errors, leading to poor values. The
role of physicochemical reference materials in the past and the present
will be outlined, and their status in the future will be explored.
* Plenary lecture presented at the 16th
IUPAC Conference on Chemical Thermodynamics (ICCT-2000), Halifax, Nova
Scotia, Canada, 6-11 August 2000. Other presentations
are published in this issue, pp. 1799-1849.
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