Platinum-iridium kilogram mass

The present standard of mass is the platinum-iridium kilogram mass kept at the International Bureau of Weights and Measures in Sevres, France. 

Mass kilogram kg Mass of a cylinder of platinum-iridium alloy kept at Paris. 

Analytical chemists make a distinction between calibration and standardization. Calibration ensures that the equipment or instrument used to measure the signal is operating correctly by using a standard known to produce an exact signal. Balances, for example, are calibrated using a standard weight whose mass can be traced to the internationally accepted platinum-iridium prototype kilogram. 

Variations in the Force Due to Gravity. The mass of an object is the quantity of matter ia the object. It is a fundamental quantity that is fixed, and does not change with time, temperature, location, etc. The standard for mass is a platinum—iridium cylinder, called the International Kilogram, maintained at the International Bureau of Weights and Measures, ia Snvres, France. The mass of this cylinder is 1 kg by definition (9). AH national mass standards are traceable to this artifact standard. 

For scientific work the fundamental standard of mass is the international prototype kilogram, which is a mass of platinum-iridium alloy made in 1887 and deposited in the International Bureau of Weights and Measures near Paris. Authentic copies of the standard are kept by the appropriate responsible authorities in the various countries of the world these copies are employed for the comparison of secondary standards, which are used in the calibration of weights for scientific work. The unit of mass that is almost universally employed in laboratory work, however, is the gram, which may be defined as the one-thousandth part of the mass of the international prototype kilogram. 

Mass Kilogram kg A platinum-iridium bar kept in a guarded chateau near Parisa... 

The standard kilogram is defined as the mass of a platinum-iridium cylinder kept at the International Bureau ofWeights and Measures in Sevres, France. The cylinder is removed from its very safe location only once a year for comparison with duplicates, such as the one shown here, which is housed at the National Institute of Standards and Technology in Washington, D.C. 

KILOGRAM (kg). A unit of mass and is based upon a cylinder of platinum-iridium alloy kept by the International Bureau of Weights and Measures at Paris. A duplicate in the custody of the National Bureau of Standards at Washington is the mass standard for the United States. The kilogram is the only base unit still defined by an artifact. (A kilogram equals (1) 1,000 grams (2) 2.205 pounds (3) 9,842 x 10-4 long tons or (4) 1 102 x 10-3 short tons. 

The standard kilogram is defined as the mass of a cylindrical bar of platinum-iridium alloy stored in a vault in a suburb of Paris, France. There are 40 copies of this bar distributed throughout the world, with two (Numbers 4 and 20) stored at the U.S. National Institute of Standards and Technology near Washington, D.C. 

The most important modem system of units is the SI system, which is based around seven primary units time (second, abbreviated s), length (meter, m), temperature (Kelvin, K), mass (kilogram, kg), amount of substance (mole, mol), current (Amperes, A) and luminous intensity (candela, cd). The candela is mainly important for characterizing radiation sources such as light bulbs. Physical artifacts such as the platinum-iridium bar mentioned above no longer define most of the primary units. Instead, most of the definitions rely on fundamental physical properties, which are more readily reproduced. For example, the second is defined in terms of the frequency of microwave radiation that causes atoms of the isotope cesium-133 to absorb energy. This frequency is defined to be 9,192,631,770 cycles per second (Hertz) —in other words, an instrument which counts 9,192,631,770 cycles of this wave will have measured exactly one second. Commercially available cesium clocks use this principle, and are accurate to a few parts in 1014. 

The second, symbol s, is the SI unit of time, defined as the duration of 9,192,631,770 cycles of radiation associated with a specified transition of the cesium atom. The meter, symbol m, is the fundamental unit of length, defined as the distance light travels in a vacuum during 1/299,792,458 of a second. The kilogram, symbol kg, is the mass of a platinum/ iridium cylinder kept at the International Bureau of Weights and Measures at Sevres, France. The unit of temperature is the kelvin, symbol K, equal to 1/273.16 of the thermodynamic temperature of the triple point of water. A more detailed discussion of tern-perature, the characteristic dimension of thermodynamics, is given in Sec. 1.4. The measure of the amount of substance is the mole, symbol mol, defined as the amount of substance represented by as many elementary entities (e.g., molecules)... 

The mass df an object is measured in terms of grams (g) or kilograms (kg), the kilogram being equal to 1000 g. The kilogram is defined as the mass of a standard object made of a platinum-iridium alloy and kept in Paris. One pound is equal approximately to 454 g, and hence 1 kg is equal to approximately 2.2 lb. Note that it has become customary in recent years for the abbreviations of units in the metric system to be written without periods. 

Mass Recall that mass is a measure of the amount of matter. The SI base unit for mass is the kilogram (kg). A kilogram is about 2.2 pounds. The kilogram is defined by the platinum-iridium metal cylinder shown in Figure 2-2. The... 

The basic unit of mass in the SI system is the kilogram (Table 1-6). The kilogram is defined as the mass of a platinum-iridium cylinder stored in a vault in Sevres, near Paris, France. A 1-lb object has a mass of 0.4536 kg. The basic mass unit in the earlier metric system was the gram. A U.S. five-cent coin (a nickel ) has a mass of about 5 g. 

Mass The mass of an object refers to the quantity of matter it contains. The SI unit of mass is the kilogram (kg), the only base unit whose standard is a physical object—a platinum-iridium cylinder kept in France. It is also the only base unit whose name has a prefix. (In contrast to the practice with other base units, however, we attach prefixes to the word gram, as in microgram, rather than to the word kilogram thus, we never say microkilogram. )... 

The kilogram is the mass of a platinum-iridium block in the custody of the Bureau International des Poids et Mesures at Sevres, France. 

Around 1800, one kilogram was defined as the mass of a cubic decimeter of water. In 1901, the kilogram was defined as the mass of a certain standard, made of platinum -iridium. This definition is still waiting for a replacement. 

The SI unit of mass is the kilogram (kg), which is interesting for a few reasons. It is the only basic SI unit defined with a prefix (kilo) already in place, and it is the only one defined by reference to a physical object—a mass of platinum-iridium held at Sevres in France. To express the large quantities of material that we encounter in the extraction and processing of ores it is usual to use the metric ton (sometimes written toime symbol t) ... 

The kilogram is the basic unit of mass. It is the mass of an international prototype in the form of a platinum-iridium cylinder kept at Sevres in France. It is now the only basic unit still defined in terms of a material object, and also the only one with a prefix [kilo] already in place, second [s]... 

Mass m Kilogram kg A kilogram (kg) is equal to the mass of an international prototype of mass. The prototype is a cylinder of platinum-iridium with a height and diameter of 0.039 m. Mass is the only unit defined in terms of an arbitrary artifact instead of a natnral phenomenmi... 

SI base unit of mass, equal to the mass of the international prototype of the kilogram, a cylinder consisting of a platinum-iridium alloy kept in a vault at Sevres in France. The kilogram is the only SI base unit that to date has yet to be defined in terms of physical constants. 

A short article dealing with the problems of maintaining "Le Grand K" the platinum-iridium bar whose mass defines the kilogram. "Bearing Down on the Kilogram Standard," Science News, Vol. 147, fanuary 28, 1995, 63. 

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