[Federal Register Volume 73, Number 96 (Friday, May 16, 2008)]
[Notices]
[Pages 28432-28433]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-11058]


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DEPARTMENT OF COMMERCE

National Institute of Standards and Technology

[Docket No.: 080505629-8631-01]


Interpretation of the International System of Units (the Metric 
System of Measurement) for the United States

AGENCY: National Institute of Standards and Technology, Commerce.

ACTION: Notice.

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SUMMARY: The International System of Units (SI) (the metric system of 
measurement) has been recognized for use in the United States since 
1866 (15 U.S.C. 204) and is the preferred system of measurement for 
trade and commerce. The SI was established and is maintained by the 
General Conference of Weights and Measures and is interpreted or 
modified for use in the United States by the National Institute of 
Standards and Technology (NIST) by authority of the Secretary of 
Commerce (15 U.S.C. 205). This notice describes the recent 
modifications to the SI and announces the publication of the latest 
interpretation of the SI for the United States in the 2008 Edition of 
NIST Special Publication 330 ``The International System of Units.'' The 
2008 Edition of NIST Special Publication 811 ``Guide for the Use of the 
International System of Units'' was also published. Together these 
publications provide the legal interpretation of and guidelines for the 
use of the SI in the United States.

FOR FURTHER INFORMATION CONTACT: Dr. Ambler Thompson, National 
Institute of Standards and Technology, Weights and Measures Division, 
International Legal Metrology Group, 100 Bureau Drive, Stop 2600, 
Gaithersburg, MD 20899-2600 or by telephone (301) 975-2333, Fax: (301) 
975-8091, or by e-mail at ambler.thompson@nist.gov.
    For information regarding NIST's efforts to coordinate the 
transition to the International System of Units, contact: Elizabeth 
Gentry, Metric Coordinator, National Institute of Standards and 
Technology, Weights and Measures Division, Laws and Metric Group, 100 
Bureau Drive, Stop 2600, Gaithersburg, MD 20899-2600 or by telephone 
(301) 975-3690, Fax (301) 975-8091, or by e-mail at TheSI@nist.gov.

SUPPLEMENTARY INFORMATION: The International System of Units 
(abbreviated as SI in all languages), generally known as the metric 
system, is the preferred system of measurement for use in trade and 
commerce in the United States (15 U.S.C. 205b) but use of traditional 
systems of weights and measures in non-business activities is 
permitted. The SI was established in 1960 by the General Conference of 
Weights and Measures (abbreviated CGPM in all languages) and is 
interpreted, or modified for, the United States by the Secretary of 
Commerce (15 U.S.C. 205c) who has delegated this authority to the 
Director of the National Institute of Standards and Technology (NIST). 
The CGPM is an international organization established by the Meter 
Convention in 1875 in which more than 50 countries participate. One of 
the responsibilities of the CGPM is to ensure the SI reflects the 
latest advances in science and technology and provides a single 
international language for measurement. In 2006 the CGPM published 
changes to the SI in the 8th Edition of the Bureau of International 
Weights and Measures SI publication commonly known as the ``SI 
Brochure.'' This notice describes the modifications to the SI and 
announces the publication of the latest interpretation of the SI for 
the United States in the 2008 Edition of NIST Special Publication (SP) 
330 ``The International System of Units (SI).''
    NIST SP 330 describes the history of the Meter Convention, explains 
how the International System of Units was developed, and describes the 
global effort to maintain the system. A comprehensive description of 
the SI's base units, terminology, units and symbols is also provided. A 
description of the decimal system and the appropriate multiples and 
submultiples to be used in expressing units and values is included. 
Also provided are editorial style guidelines to ensure that SI values 
and units are properly formatted and clearly written. NIST has also 
published the 2008 Edition of its Special Publication 811 ``Guide for 
the Use of the International System of Units (SI),'' which includes 
additional guidance on the use of the SI and a broad range of 
conversion factors. When used together, these publications provide the 
most current interpretation of the SI and present the latest guidance 
on the use of the SI in the United States.

I. Changes to the International System of Units (SI)

    The CGPM adopted the following changes in the 8th Edition (2006) of 
the SI Brochure and these have been

[[Page 28433]]

incorporated in the 2008 Edition of NIST SP 330:
    a. Full incorporation of the 2000 Supplement which clarified the 
definition of the second and incorporated the new coherent SI unit with 
a special name and symbol for the mol s-1, the katal with 
symbol kat, for expressing values of the quantity catalytic activity;
    b. A discussion designated as ``the set of coherent SI units'' was 
added to clarify that the base and coherent derived units of the SI 
form a coherent set;
    c. New section entitled ``Units for quantities that describe 
biological effects'' was added in view of their importance for human 
health and safety;
    d. New section entitled ``Historical note'' was added to provide 
updated information from Section 1.1 of the 7th Edition;
    e. Appendix 1 was updated to include all the recent decisions of 
the CIPM and CGPM which impact the SI;
    f. Appendix 2, which discusses the experimental realization of 
units, is made available only in electronic form on the BIPM Web site 
at http://www.bipm.org/en/si/si_brochure/appendix2/, so that it may be 
easily updated between SI brochure versions; and
    g. New Appendix 3 entitled ``Units for photochemical and 
photobiological quantities,'' was added to point out that the SI 
already includes a SI base unit, the candela, which is considered to be 
a biological effects unit of importance to industry and human health 
and safety.

II. Modifications to the SI for Its Use in the United States

    The 2008 Edition of NIST SP 330 differs from the ``SI Brochure'' to 
conform to the language and customary use of measurement units in the 
United States:
    a. The spelling of English words is in accordance with the United 
States Government Printing Office Style Manual, which follows Webster's 
Third New International Dictionary rather than the Oxford Dictionary. 
Thus, the spellings ``meter,'' ``liter,'' and ``deca'' are used rather 
than ``metre,'' ``litre,'' and ``deka'' as in the original BIPM English 
text;
    b. The name of the unit with symbol t is defined according to 1 t = 
103 kg which is called ``metric ton'' rather than ``tonne;''
    c. The four units curie, roentgen, rad, and rem are included in 
Table 10;
    d. A number of Editors' notes are added in order to indicate 
differences of interpretation and to clarify the text;
    e. A few minor editorial changes are made in order to 
``Americanize'' some phrases.
    This notice supersedes the last interpretation of the SI that was 
published in the Federal Register on July 28, 1998 (Vol. 63, No. 144--
FR 40334--40340).
    NIST SP 330, NIST SP 811, and other useful information regarding 
the International System of Units (SI) are published electronically 
(http://physics.nist.gov/cuu/Units/index.html and http://nist.gov/metric) and in hard copy. Requests for hardcopies can be sent to: 
TheSI@nist.gov.
    Although there is no formal comment period, comments and 
suggestions on the SI are invited and should be sent to Dr. Ambler 
Thompson at the address previously indicated.

    Dated: May 9, 2008.
James M.Turner,
Deputy Director.
 [FR Doc. E8-11058 Filed 5-15-08; 8:45 am]
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