Metre Convention

The Convention was signed in Paris in 1875 by representatives of 17 nations. As well as founding the BIPM, the Metre Convention established a permanent organizational structure for member governments to act in common accord on all matters relating to units of measurement. The task of the BIPM is to ensure worldwide uniformity of measurements and their traceability to the International System of Units (SI). 

In October 1999, the directors of the NMIs of the industrialized states of the world signed a Mutual Recognition Arrangement (MRA) for national measurement standards and for calibration and measurement certificates issued by their institutes. This arrangement was drawn up by the International Committee of Weights and Measures (CIPM), under the authority given to it in the Metre Convention. 

A long capillary with a computer-controlled switching valve (the instruments must be separated by 2-3 metres because of the strong magnetic field) connects the exit from the HPLC with the probehead. The latter is completely different in its construction from conventional probeheads instead of the NMR tube there is a small flow cell, the volume of which is 40-100 pi. The transmitter and receiver coils are attached directly to the cell in order to maximize the sensitivity. 

It is cavitation in a heterogeneous medium which is the most studied by sonoche-mists. When produced next to a phase interface, cavitation bubbles are strongly deformed. A liquid jet propagates across the bubble towards the interface at a velocity estimated to hundreds of metres per second. At a liquid-liquid interface, the intense movement produces a mutual injection of droplets of one liquid into the other one, i. e. an emulsion (Fig. 3.3). Such emulsions, generated through sonication, are smaller in size and more stable than those obtained conventionally and often require little or no surfactant to maintain stability. It can be anticipated therefore that Phase Transfer Catalysed (PTC) reactions will be improved by sonication. Examples are provided later in this chapter. 

Convention du Metre (2006) The International System of Units. 8th edn. http //www.bipm. org/utils / common/pdf/ si brochure 8. pdf. Accessed 28 Oct 2011... 

According to the modern convention, measurable quantities are expressed in SI (System Internationale) units and replace the centimetre-gram-second (cgs) system. In this system, the unit of length is a metre (m, the unit of mass is kilogram (kg) and the unit of time is second (s). All the other units are derived from these fundamental units. The unit of thermal energy, calorie, is replaced by joule (1 J = 107 erg) to rationalize the definition of thermal energy. Thus, Planck s constant... 

Abstract An international system for providing traceability for the results from physical measurements has been under continuous development since the introduction of the Convention of the Metre over 100 years ago. Such a system has only been in existence for chemical measurements for about a decade and there is much that can be learnt from the way in which traceability has developed in physical measurements that will help its development for chemical measure-... 

The Convention of the Metre dates back to 1875, so there is a long history to the traceability of the results of physical and engineering measurements to international standards. Admittedly the mole was added to the base units in 1971 but there was little or no involvement of the International Committee of Weights and Measures (CIPM) in chemical measurements until a decade ago. It is therefore not surprising that traceability is not so well established for chemical measurements. 

The importance of using common reference scales has been recognised for centuries. For example, in England, King John introduced consistent measures throughout the land in 1215. Other countries also had their own measurements scales standards. Many city museums show the standard measures used for trade within the city or local state. As trade widened so did the need for comparability of measurement results and the use of common units widened. The many different measurements scales were harmonised with the introduction of the metric system and the SI units under the Convention of the Metre signed in 1875. An excellent summary of the historical development of units of measurement is given in the NBS Special Publication 420 [1], Under the Convention of the Metre a hierarchical chain of national and international measurement standards has been developed for the measurement of most of physical quantities. 

Bureau internationale de poids et mesures, Le Systeme international d unites (SI), Organisation Intergouvernemental de la Convention du Metres, Sevres, 1998. 

Molarity (moles of solute per liter of solution, symbolized by m) is a useful unit for concentration, but it is not recommended for highly accurate measurements by the international unit convention, Le Systeme International d Unites or Systeme International (SI). Nevertheless, we will use molarity in addition to the SI unit of mol m-3. We also note that SI as currently practiced allows the American spelling "liter and "meter as well as the British spelling "litre and "metre. ... 

When describing a measurement, you normally state both a number and a unit (e.g. the length is 1.85 metres ). The number expresses the ratio of the measured quantity to a fixed standard, while the unit identifies that standard measure or dimension. Clearly, a single unified system of units is essential for efficient communication of such data within the scientific community. The Systeme International d Unites (SI) is the internationally ratified form of the metre-kilogram-second system of measurement and represents the accepted scientific convention for measurements of physical quantities. 

Momentum. Although the SI unit of length is the metre and the units of momentum are kg m s, it is conventional in neutron scattering to express length in Angstrom units lA = 10 m. Consequently the conventional unit for the neutron wavelength is A and for the neutron wavevector A. ... 

The furnace is of conventional Ausmelt design approximately 4 metres internal diameter and 10 metres high, with external water cooling on the shell, roof and offtake. The furnace uses natural gas as fuel and the Ausmelt lances are oxygen enriched to approximately 40% to optimise process efficiency. 

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