The 2,069th Meeting of the Society

February 7, 1997

Metrology, the Science and the Philosophy

H. Steffen Peiser

National Institute of Standards and Technology

About the Lecture

Measurement with lowest achievable uncertainties in relation to an internationally agreed framework of units is widely held to be the lackluster occupation of uninspired pedants. Yet, basic science depends on measurement. First, it confirms hypotheses that cover a limited range to an adequate approximation. Thus a theory becomes established. Outside its range of applicability, however, or for measurements with previously unachieved uncertainties, significant deviations from relationships predicted by the theory are often uncovered. Measurements thus lead to deeper understanding and crucial refinements of theories.

Peiser describes the exhilaration of such measurements first in crystallography, then in low-temperature free-radical reactions. He illustrates the thrilling chase of error sources with the building of a new type of kilogram balance that was later donated to the International Bureau of Weights and Measures in Paris. Applications follow to crystal growth, atomic weights, and the current best direct determination of the Avogadro constant. Currently Peiser contributes to applications of metrology to openly revealed, credible chemical measurement methods and to persuade those responsible for the tabulation of high-accuracy physical-property data sets to accept retroactive assessments of reliability.

About the Speaker

Steffen Peiser was educated in England at St. Paul's, London, and Cambridge University (honors BA and MA in chemistry, physics, mathematics, and mineralogy), where he held a Hutchinson Research Studentship. He immigrated to the United States in 1957. From then to now he has been associated with the National Bureau of Standards (now the National Institute of Standards and Technology), since retirement as a consultant. He has led a number of missions on technology development to rapidly industrializing nations. For this work, which is not the subject of his presentation to the Society, he received a number of distinctions, including an honorary D.Sc. and a National Medal of Honor of the Republic of Korea.


President Lettieri called the 2069th meeting to order at 8:20 p.m. on February 7, 1997. The Recording Secretary read the minutes of the 2068th meeting and they were approved.

The speaker for the 2069th meeting was H. Steffan Peiser, from the National Institute of Standards and Technology. The title of his talk was “Metrology, The Science And The Philosophy.”

Mr. Peiser stated that a close relationship existed between modern philosophy and contemporary natural science. As an example, he pointed out that following most new insights of science, we formulate laws to rule our world and cosmic events. Scientific experimentation at first confirms the law's validity but soon shows the law to be “not quite true.” As an example, Mr. Peiser identified stoichiometry in chemistry as one of our “almost true laws.” Further, its exact truth is assumed at great peril since we have much experimental knowledge of departures with many chemicals and chemical reactions. This in no way is to detract from the immense value of “nearly true laws” and their technological by-products. Rather, it serves to point out the danger carried with the laws of a know-it-all belief. The prime place for this relationship between science and philosophy lies in measurement science, called metrology.

Mr. Peiser stated that a young man once asked him “is it not deadly dull to try simply to add one or two decimal digits to a number?” Mr. Peiser's responded that it may be true for accountancy, but to a scientist, such achievement would be heavenly.

Small discrepancies in measurements have been at the root of all progress in science. The modern claim of quality of a measurement is its estimated uncertainty. Considering Avogadro's constant, Mr. Peiser showed the changes in the value of the constant and the estimated uncertainty over the years until today when the uncertainty is on the order of 10-7.

Mr. Peiser also advised that atomic weight data since 1969 appears to be very reliable within the uncertainties given. However, related data such as the mass values of individual nuclides do not quite match the post 1969 atomic weight data with regard to reliability. Further, a compilation of atomic-weight values since 1884 finds much inferior reliability. This is not due to the competency of the scientists who did the measurements, who include some of the greatest chemists of all time. The inferior reliability is due rather, to lack of adherence to the discipline of metrology, especially in relation to uncertainty estimations.

Mr. Peiser then closed his presentation and kindly responded to questions from the audience.

President Lettieri thanked Mr. Peiser for the society and announced the next meeting. He then made the usual parking announcement and adjourned the 2069th meeting to the Social Hour at 9:37 p.m.

Attendance: 44
Temperature: 4.5°C
Weather: chilly

Respectfully submitted,

Bill Spargo
Recording Secretary