These reports are part of NIST's growing effort to respond to the need for accurate and timely information on subjects related to national and international standards and conformity assessment. Other related reports are listed on the Office of Standards Services web site [3]. NIST has also formed federal working groups to address such issues, has responded to many thousands of requests for information on these topics, and has provided staff members to give lectures at numerous workshops and at various public and private sector fora.

Maureen Breitenberg is internationally recognized as a leading authority on conformity assessment issues, standards, guidelines and practices. Her many publications have been used nationally and internationally to address trade-related issues. They have been widely distributed by NIST to private sector organizations, other U.S. federal agencies, state agencies involved in trade development and assistance, U.S. embassies, foreign governments, colleges, universities, and libraries for education and training purposes and for responding to trade related inquiries. Several have been translated and/or reprinted by foreign and domestic government and private sector organizations. Her latest publication, the 1999 edition of SP 739, Directory of Federal Government Certification and Related Programs [4], has been highlighted as a very useful resource in terms

of depth of content, authority, and how well the information is presented.

Breitenberg received the NIST Bronze Medal in 1992. She was also elected to the Government and Industry Quality Liaison Panel's Leadership Team, which resulted in harmonizing federal agency quality system requirements for suppliers to the government. The Panel received the Vice President's National Performance Review (Golden Hammer) Award in 1995 for its efforts.

Prepared by Maureen Breitenberg.

Bibliography

[1] Maureen Breitenberg, Questions and Answers on Quality, the ISO 9000 Standard Series, Quality System Registration, and Related Issues, NISTIR 4721, National Institute of Standards and Technology, Gaithersburg, MD (1991).

[2] Maureen Breitenberg, More Questions and Answers on the ISO 9000 Standard Series and Related Issues, NISTIR 5122, National Institute of Standards and Technology, Gaithersburg, MD (1993).

[3] NIST publications on standards and conformity assessment activities are listed on the web site (http://ts.nist.gov).

[4] Maureen Breitenberg (ed.), Directory of Federal Government Certification and Related Programs, NIST Special Publication 739, 1999 Edition, National Institute of Standards and Technology, Gaithersburg, MD (1999).

Today we take it for granted that when we buy pound of hamburger, whether we are in New York, St. Louis, or California, we will be getting the same amount of product for our money. A hundred years ago consumers could not be so sure that a "pound" in one state was the same as a "pound" in another. Concerns about the uniformity of weights and measures standards and laws from state to state led the National Bureau of Standards to convene the first "Conference on the Weights and Measures of the United States" in January 1905. This first meeting laid the foundation for the creation of the National Conference on Weights and Measures (NCWM), which continues to this day. The NCWM is the primary mechanism used by NIST to fulfill its responsibility, as stated in its Organic Act, to work with the states "in securing uniformity in weights and measures laws and methods of inspection." Only 11 delegates attended the first Conference; however, there are now over 3,000 NCWM members representing state and local weights and measures jurisdictions, the Federal Government, industry, consumers, and other countries.

NBS published the report of the 1905 Conference and has since published the reports of the 83 other Conferences held since that first meeting [1]. The reports document the history of the NCWM's development of standards in the form of model weights and measures laws, regulations, and practices. When state and local weights and measures jurisdictions adopt these standards, they become mandatory. The reports of the Conference serve as a legislative history of the requirements in the model laws; therefore, state officials, the NIST Office of Weights and Measures, Federal and international standards agencies, members of the public, and others often consult the reports to identify the intent of the requirements. The reports contain a wealth of technical and historical information, including special addresses by NCWM Chairmen and by NBS/NIST Directors, who have served as Honorary Presidents of the NCWM. It would not be practical to describe all the reports in this centennial book; however, particular attention is called to the report of the first Conference because of its historical significance. In addition, it contains a history of U.S. weights and measures from the beginnings of the country up to 1905. This historical information was used as the basis for later

NBS publications, such as SP 447, Weights and Measures Standards of the United States, A Brief History [2].

Over the years, the uniform laws, regulations, and practices developed by NIST in cooperation with the NCWM have been gathered together and published in a series of NIST Handbooks. Two Handbooks of particular note are Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices [3], and Handbook 130, Uniform Laws and Regulations, in the areas of legal metrology and engine fuel quality [4].

Handbook 44 was first published in 1949, having been preceded by similar handbooks of various designations and in several forms, beginning in 1918. This Handbook has become the standard for specifications and tolerances for commercial weighing and measuring devices in the United States. These devices include scales, liquid-measuring devices, volumetric measures, linear-measuring devices, mass flow meters, grain moisture meters, timing devices, near infrared grain analyzers, and multiple dimension measuring devices. All 50 states have adopted the Handbook as the legal basis for regulating commercial weighing and measuring devices. It is updated by NIST each year following the Annual Meeting of the NCWM to include changes adopted at the meeting. A NIST staff member serves as Technical Advisor to the NCWM Specifications and Tolerances Committee, which recommends changes and additions to the Handbook. Nearly 3,000 copies of the Handbook are distributed annually to NCWM members. Another thousand copies are sold through the Government Printing Office and hundreds of copies are distributed to Depository Libraries throughout the country. In addition, many associations reprint portions of the Handbook to distribute to their members. In a number of states, commercial weighing and measuring device servicepersons and agencies are required to demonstrate their knowledge and understanding of the Handbook in order to be registered by the states. The significance of the Handbook is further indicated by the fact that it serves as the basis for the National Type Evaluation Program (NTEP), a cooperative effort of NIST and the NCWM. NTEP evaluates models of weighing and measuring devices to determine if they meet the requirements of Handbook 44. Forty-four

states require that only weighing and measuring devices with an NTEP Certificate of Conformance can be installed in commercial applications in the state. (Fig. 1) NIST Handbook 130 compiles the latest uniform laws and regulations and related interpretations and guidelines adopted by the NCWM. In 1979, NBS issued the first compilation of the various laws and regulations that had been adopted by the NCWM under the title "Model State Laws and Regulations." The name of the publication was later changed to make it clear that the standards in the publication were recommended for adoption by

local as well as state jurisdictions. Handbook 130 is the standard for uniform weights and measures laws and regulations in the United States. It has been estimated that weights and measures laws and regulations impact transactions involving $4.5 trillion (52.8 %) of the $8.51 trillion U.S. Gross Domestic Product (1998 figures). NIST technical advisors, working with members of the NCWM Laws and Regulations Committee, have helped develop and maintain the standards in Handbook 130. These standards have been widely adopted by the weights and measures community. For

example, 44 states have adopted a Weights and Measures Law based on the uniform law in Handbook 130. As of 1999, 45 states have adopted Packaging and Labeling requirements and 42 states have adopted Method of Sale requirements based on the uniform regulations in Handbook 130.

Prepared by Joan Koenig.

Bibliography

[1] Reports of the National Conference on Weights and Measures 1905-1999. Various editors over the years. Latest report: Henry

V. Oppermann and Joan Koenig (eds.), Report of the 85th National Conference on Weights and Measures, NIST Special Publication 957, National Institute of Standards and Technology, Gaithersburg, MD (2000).

[2] Lewis V. Judson, Weights and Measures Standards of the United States, A Brief History, NBS Special Publication 447, National Bureau of Standards, Washington, DC (1976).

[3] Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, NIST Handbook 44 (various editors over the years; editors of the 2001 edition: Tina G. Butcher, Terry L. Grimes, and Juana Williams).

[4] Uniform Laws and Regulations, in the areas of legal metrology and engine fuel quality, NIST Handbook 130, (various editors over the years; editors of the 2001 edition: Thomas Coleman and Terry L. Grimes).

There are numerous examples in trade and commerce in which small particles play an important role, either as the commodity of trade itself, as unwanted contaminants in a product or an environment, or as a basis for comparison between a "normal" particle and an "abnormal" one. Many of the products we buy come in the form of small particles, powders, or particle suspensions, including medicines, cosmetics, food products, paints, talcum powder, cements, photocopier toners, and milk (which is essentially a suspension of microdroplets of fat in water). In other cases, small particles are unwanted, for example in cleanrooms for microelectronics or pharmaceutical manufacturing, in lubricating oils in motor vehicles, and in the air we breathe and the water we drink. There are also situations where one would like to compare a known, standard particle to an unknown, test particle as in the case of blood-cell testing. In all of these instances, particle standards play a key role, enabling quality control, product uniformity, conformance to standards, traceability to NIST, interchangeability of instrumentation, uniformity of measurement, or some combination of these goals.

With these benefits in mind, the National Bureau of Standards set out, in the early 1980's, to develop a range of particle-sizing Standard Reference Materials (SRMs) for use in calibrating and certifying instruments that measure particle size, whether as products, by-products, or contaminants. In cooperation with ASTM Committee E-29 on Particle Size Measurement, researchers in the Precision Engineering Division (PED) at NBS developed a series of five SRM's consisting of monosized polystyrene microspheres with diameters of 0.3, 1, 3, 10, and 30 μm [1-4]. The three smallest particles, donated by commercial vendors, were certified first, since such small microspheres were comparatively easy to grow using conventional polymer emulsion techniques. However, for the two larger diameters, 10 μm and 30 μm, the techniques that existed at the time did not yield rigid particles of the required sphericity because of the detrimental effects of gravity on the microsphere growth process. (At the time, there were techniques to make large microspheres, but these were relatively soft and unsuitable for use as SRMs, which must be rigid and stable.)

At about the same time that NBS was certifying its series of particle-sizing SRMS, a group of researchers led by John Vanderhoff of Lehigh University and

Dale Kornfeld of NASA Marshall Space Flight Center was conducting experiments aboard the space shuttle to determine the effect of microgravity on chemical reaction rates of emulsion polymerization, as well as on the morphology (shape) of polymer microspheres grown in microgravity [5]. The first experiments of the Monodisperse Latex Reactor (MLR) were conducted in 1982 aboard space shuttle flight STS-3 and resulted in microspheres as large as 5 um in mean diameter. A subsequent experiment on a later shuttle flight, STS-6, produced particles of 10 μm mean diameter. In 1984, the NBS group obtained samples of the 5 μm and the 10 μm materials and did a detailed intercomparison between the space-made particles and earth-made particles of similar composition [1,2]. In both cases, the space-made materials were found to be superior in terms of individual particle sphericity, narrowness of size distribution, and, importantly, in particle rigidity. An agreement was then made between NASA and NBS for NASA to provide a sufficient quantity of the 10 μm material to make up 600 5 mL vials containing liquid suspensions of the polystyrene microspheres for use as an SRM. The agreement also called for NBS to receive the 30 μm polystyrene spheres to be grown on a subsequent shuttle flight.

To certify SRM 1960, the so-called "space beads" (Figs. 1 and 2), researchers at NBS, led by Tom Lettieri of the PED, developed three new particle-sizing techniques, which are described in the publication Certification of SRM 1960: Nominal 10 μm Diameter Polystyrene Spheres ("Space Beads") [1]. These techniques were center distance finding (CDF), resonance light scattering (RLS) from a liquid suspension of microspheres, and metrology electron microscopy (MEM). The primary certification technique for SRM 1960, center distance finding, was developed by Ike Hartman of the PED. CDF uses a conventional optical microscope and relies on the fact that the microspheres act like tiny lenses when placed on a glass slide in the microscope. The microspheres were spread onto a slide such that they formed long chains of contacting spheres, rather than the regular hexagonal arrays formed in conventional array sizing. This ensured that the particles were in close contact, compared to conventional array sizing where the non-zero diameter distribution of the microspheres leads to voids, cracks, gaps, and other flaws in the arrays. These flaws lead to uncertainties in