International Committee on Weights and Measures

Certain units not part of the SI are so widely used that it is impractical to abandon them (e.g., liter, minute, and hour) or are so well established that the International Committee on Weights and Measures has authorized their continued use (e.g., bar, curie, and angstrom). In addition, quantities that are expressed in terms of the fundamental constants of nature, such as elementary charge, proton mass, Bohr magneton, speed of light, and Planck constant, are also acceptable. However, broad terms such as atomic units are not acceptable, although atomic mass unit, u, is acceptable and relevant to chemistry. 

The International Temperature Scale of 1990 is described in Section 1 of this Handbook, where the defining fixed points are listed. The Consultative Committee on Thermometry (CCT) of the International Committee on Weights and Measures (CIPM), which oversees the temperature scale, has recommended a number of secondary reference points whose values have been accurately determined with respect to the primary fixed points. The most accurate of these, referred to as first quality points , satisfy several criteria involving purity of the material, reproducibility, and documentation of the measurements. The CCT also lists second quality points that do not yet satisfy all the criteria but are still useful. Taken together. 

Acceleration due to gravity n. The acceleration of a body freely falling in a vacuum. The International Committee on Weights and Measures has adopted as a standard or accepted value, 980.665 cm/s or 32.174ft/s. Hartland S (ed) (2004) Surface and interfacial tension. CRC Press, Boca Raton, FL. 

Metrologia International Committee of Weights and Measures (CIPM) Pavilion de Breteuil Parc de St. Cloud, Prance Includes articles on scientific metrology worldwide, improvements in measuring techniques and standards, definitions of units, and the activities of various bodies created by the International Metric Convention. 

The ITS is an artifact scale, designed to relate temperature measurements made with practicable instruments as closely as possible to the thermodynamic scale. The scale is established and controlled by the International Committee of Weights and Measures (BIPM) through its Consultative Committee on Thermometry, which was established in 1937. The BIPM itself is established to maintain and implement the Treaty of the Meter, to which most nations of the wodd subscribe thus the ITS has not only scientific but legal status in most nations. Within nations, the Temperature Scale is maintained by national standards establishments, eg, in the United States the National Institute for Standards and Technology (NIST), in England the National Physical Laboratory (NPL), and in Germany the Physikalisch-Technische Bundesanstalt (PTB). 

The General Conference on Weights and Measures (CGPM) meets every 4 years and makes additions to, and changes in, the international system of units (SI).3 A select group of 18 internationally recognized scientists from the treaty nations is the International Committee of Weights and Measures... 

Abstract This paper reviews the current state of play of the Mutual Recognition Arrangement created by the International Committee for Weights and Measures in 1999. The aim of the MRA is to provide a framework within which National Metrology Institutes can demonstrate the equivalence of their realisations of the units and quantities of the SI system to which accredited laboratories are traceable. The article offers some views on the need for traceable... 

Abstract Establishment of the traceability and the evaluation of the uncertainty of the result of a measurement are essential in order to establish its comparability and fitness for purpose. There are both similarities and differences in the way that the concepts of traceability and uncertainty have been utilised in physical and chemical measurement. The International Committee of Weights and Measures (CIPM) have only in the last decade set up programmes in chemical metrology similar to those that have been in existence for physical metrology for over a century. However, analytical chemists over that same period have also developed techniques, based on the concepts of traceability and uncertainty, to ensure that their results are comparable and fit for purpose. This paper contrasts these developments in physical and chemical metrology and identifies areas where these two disciplines can learn from each other. 

CIPM), which meets annually and oversees the work of the International Bureau of Weights and Measures (BIPM). The BIPM, based at Sevres just outside Paris, has the responsibility for international standards and is a center for international research and cooperation in metrology. The CIPM has created a number of advisory specialist committees (consultative committees) that are each chaired by a member of CIPM. The committee of interest to chemists is the Consultative Committee on the Amount of Substance (CCQM). It oversees the Avogadro project and coordinates a series of international interlaboratory trials called Key Comparisons (BIPM 2003), which... 

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