Metre Convention Systeme international measurement

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. 

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. 

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). 

Hgure 1 The structure of the international measurement system established by the Convention of the Metre in 1875. The chart shows the key international organizations and the links between them. (Reproduced with permission from the BIPM website.)... 

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-... 

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