Page 810 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Appendix A: International System of Units

The system of units used for measurement throughout the with those of the English. The metric system was legalized,
world is the International System of Units, called the SI however, with the Metric Act of 1866. In 1893, the inter-
system. In using the SI system, a set of conventions has national meter and kilogram became the fundamental standards
evolved. This appendix reviews the origin and status of the of length and mass in the United States (ASTM, 1991). In
SI system, and describes the conventions for the use of the 1902, Congressional legislation requiring the federal govern-
system. The American Society for Testing Materials (ASTM) ment to adopt the metric system was defeated by a single vote.
report (1991) was the primary reference for this review and is Despite these tendencies toward metrication, and while the rest
recommended for further reading. After completing this of the world was adopting the metric system, the United States
appendix, a book by Cardarelli (1999) was found, which has maintained its adherence to the English system.
listed almost every obscure unit imaginable, each converted to The federal government began further movement toward
SI units and with interesting and useful notes. Fundamental metrication in 1968 legislation to study its benefits and prob-
constants are also given. Online conversions were available lems. This was followed by the 1975 Metric Conversion Act
at several Web sites (http:==www.Imnoeng.com=units.htm (Interagency Council on Metric Policy, 1991; Carver, 1992).
and http:==onlineconversion.com=) provided by colleagues at From this act, the expectation was that there would be a
Colorado State University. 10 year long voluntary transition period. The government
failed to maintain leadership, however, and so the momentum
A.1 DEVELOPMENT OF THE INTERNATIONAL underway was dissipated by about 1980.
SYSTEM OF UNITS The next legislation was in the 1988 Omnibus Trade and
Competitiveness Act that had ‘‘metric usage’’ provisions for
The modernized metric system is called the International federal agencies and was an amendment to the 1975 Act.
System of Units. This name in French, Le Système International Then on July 25, 1991, President Bush issued Executive
d’Unités, and the abbreviation, SI, were adopted in 1960 by the Order 12770, ‘‘Metric Usage in Federal Government Pro-
11th conference (ASTM, 1991). The system is maintained by grams,’’ which gave authority to the Secretary of Commerce
the General Conference on Weights and Measures. to provide the needed leadership and coordination for adopt-
The decimal system of units, the genesis of the present SI ing the metric system. The office implementing the program
system, was developed in the sixteenth century. In 1790, the was the Metric Program of the National Institute of Standards
French National Assembly requested the French Academy of and Technology (NIST), which has had this kind of respon-
Sciences to develop a system of units suitable for adoption sibility since 1901. Executive Order 12770 mandated that
worldwide. The problems of doing business and communicat- each federal agency make a transition to metric units in
ing with a myriad of local units were recognized by all government publications, work with government and private
nations, and by the scientific community in particular. The groups on metric implementation, and formulate and imple-
international standardization began with an 1870 meeting of ment a Metric Transition Plan by November 30, 1991. To
15 nations in Paris that led to the May 2, 1875, International coordinate the implementation among federal agencies, the
Metric Convention, and the establishment of a permanent Interagency Council on Metric Policy (ICMP) was established
International Bureau of Weights and Measures near Paris. A under the Department of Commerce (ICMP, 1991). The Met-
General Conference on Weights and Measures (Conférence rication Operating Committee, with 10 subcommittees, was
Générale des Poids et Mesures, CGPM) was also constituted given the responsibility to implement the metrication policy.
to handle international matters concerning the metric system. The Construction Subcommittee established the goal of insti-
The CGPM meets at least every 6 years in Paris and controls tuting the use of metric in all federal facilities by January,
the International Bureau of Weights and Measures, which 1994 (ICMP, 1991).
preserves the metric system (ASTM, 1991). The United States is the only country that has not adopted
the SI system. Nevertheless, the system, commonly used by
A.2 THE SI=METRIC SYSTEM IN THE UNITED the scientific community, is legal and has been adopted
widely in engineering, and by most professional organizations
STATES
in the water quality field. The SI system is not new to engin-
Article 1, Section 8, of the United States Constitution gives eers, as its predecessor, the metric system, e.g., CGS, MKS,
Congress the power to ‘‘ .. . fix the standard of weights and has been a part of engineering and scientific education for
measures.’’ Although Thomas Jefferson and John Quincy many decades. Metric conversion is continuing, and a grow-
Adams were early advocates of the metric system, the prevail- ing consensus indicates that complete conversion is inevit-
ing notion was to bring the U.S. measures in closer harmony able. When the conversion is completed depends upon such

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