Grave (mass)
Encyclopedia
A grave is a metallic reference standard of one thousand gram
s that was used for a few years until it was replaced by the kilogram
standard in 1799.
Our modern kilogram has its origins in the pre-French Revolution
days of France
. Louis XVI
created a Consultative Commission for Units to create a new decimal
-based system of measurement. This royal commission, which included such aristocrats as Antoine Lavoisier
, founded the very beginnings of the “metric system
”, which later evolved into the contemporary International System of Units
(SI).
On 7 April 1795, the “gramme”, upon which the kilogram is based, was decreed to be equal to “the absolute weight of a volume of pure water equal to a cube of one hundredth of a metre, and at the temperature of the melting ice”. Although this was the definition of the gram, the regulation of trade and commerce required a “practical realisation”: a single-piece, metallic reference standard that was one thousand times more massive that would be known as “grave” (symbol G). This mass unit, whose name is derived from the word “gravity”, was used since 1793. Notwithstanding that the definition of the base unit of mass was the gramme (alternatively “gravet”), this new, practical realisation would ultimately become the base unit of mass. A provisional kilogram standard was made and work was commissioned to determine precisely how massive a cubic decimetre (later to be defined as equal to one litre
) of water was.
Although the decreed definition of the kilogram specified water at 0 °C — a highly stable temperature point — the scientists tasked with producing the new practical realisation chose to redefine the standard and perform their measurements at the most stable density point: the temperature at which water reaches maximum density, which was measured at the time as 4 °C. They concluded that one cubic decimetre of water at its maximum density was equal to 99.92072% of the mass of the provisional kilogram made earlier that year. Four years later in 1799, an all-platinum standard, the “Kilogramme des Archives”, was fabricated with the objective that it would equal, as close as was scientifically feasible for the day, to the mass of cubic decimetre of water at 4 °C. The kilogram was defined to be equal to the mass of the Kilogramme des Archives and this standard stood for the next ninety years.
Note that the new metric system did not come into effect until after the French Revolution
, when the new revolutionary government captured the idea of the metric system. The decision of the Republican government to name this new unit the “kilogramme” had been mainly politically motivated, because the name “grave” was at that time considered politically incorrect as it resembled the aristocratic German title of Graf
, an alternative name for the title of Count
that, like other nobility titles, was inconsistent with the new French Republic notion of equality (égalité)
. Accordingly, the name of the original, defined unit of mass, “gramme”, which was too small to serve as a practical realisation, was adopted and the new prefix “kilo” was appended to it to form the name “kilogramme”. Consequently, the kilogram is the only SI base unit
that has an SI prefix
as part of its unit name.
Gram
The gram is a metric system unit of mass....
s that was used for a few years until it was replaced by the kilogram
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...
standard in 1799.
Our modern kilogram has its origins in the pre-French Revolution
French Revolution
The French Revolution , sometimes distinguished as the 'Great French Revolution' , was a period of radical social and political upheaval in France and Europe. The absolute monarchy that had ruled France for centuries collapsed in three years...
days of France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
. Louis XVI
Louis XVI of France
Louis XVI was a Bourbon monarch who ruled as King of France and Navarre until 1791, and then as King of the French from 1791 to 1792, before being executed in 1793....
created a Consultative Commission for Units to create a new decimal
Decimal
The decimal numeral system has ten as its base. It is the numerical base most widely used by modern civilizations....
-based system of measurement. This royal commission, which included such aristocrats as Antoine Lavoisier
Antoine Lavoisier
Antoine-Laurent de Lavoisier , the "father of modern chemistry", was a French nobleman prominent in the histories of chemistry and biology...
, founded the very beginnings of the “metric system
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...
”, which later evolved into the contemporary International System of Units
International System of Units
The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...
(SI).
On 7 April 1795, the “gramme”, upon which the kilogram is based, was decreed to be equal to “the absolute weight of a volume of pure water equal to a cube of one hundredth of a metre, and at the temperature of the melting ice”. Although this was the definition of the gram, the regulation of trade and commerce required a “practical realisation”: a single-piece, metallic reference standard that was one thousand times more massive that would be known as “grave” (symbol G). This mass unit, whose name is derived from the word “gravity”, was used since 1793. Notwithstanding that the definition of the base unit of mass was the gramme (alternatively “gravet”), this new, practical realisation would ultimately become the base unit of mass. A provisional kilogram standard was made and work was commissioned to determine precisely how massive a cubic decimetre (later to be defined as equal to one litre
Litre
pic|200px|right|thumb|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre...
) of water was.
Although the decreed definition of the kilogram specified water at 0 °C — a highly stable temperature point — the scientists tasked with producing the new practical realisation chose to redefine the standard and perform their measurements at the most stable density point: the temperature at which water reaches maximum density, which was measured at the time as 4 °C. They concluded that one cubic decimetre of water at its maximum density was equal to 99.92072% of the mass of the provisional kilogram made earlier that year. Four years later in 1799, an all-platinum standard, the “Kilogramme des Archives”, was fabricated with the objective that it would equal, as close as was scientifically feasible for the day, to the mass of cubic decimetre of water at 4 °C. The kilogram was defined to be equal to the mass of the Kilogramme des Archives and this standard stood for the next ninety years.
Note that the new metric system did not come into effect until after the French Revolution
French Revolution
The French Revolution , sometimes distinguished as the 'Great French Revolution' , was a period of radical social and political upheaval in France and Europe. The absolute monarchy that had ruled France for centuries collapsed in three years...
, when the new revolutionary government captured the idea of the metric system. The decision of the Republican government to name this new unit the “kilogramme” had been mainly politically motivated, because the name “grave” was at that time considered politically incorrect as it resembled the aristocratic German title of Graf
Graf
Graf is a historical German noble title equal in rank to a count or a British earl...
, an alternative name for the title of Count
Count
A count or countess is an aristocratic nobleman in European countries. The word count came into English from the French comte, itself from Latin comes—in its accusative comitem—meaning "companion", and later "companion of the emperor, delegate of the emperor". The adjective form of the word is...
that, like other nobility titles, was inconsistent with the new French Republic notion of equality (égalité)
Liberté, égalité, fraternité
Liberté, égalité, fraternité, French for "Liberty, equality, fraternity ", is the national motto of France, and is a typical example of a tripartite motto. Although it finds its origins in the French Revolution, it was then only one motto among others and was not institutionalized until the Third...
. Accordingly, the name of the original, defined unit of mass, “gramme”, which was too small to serve as a practical realisation, was adopted and the new prefix “kilo” was appended to it to form the name “kilogramme”. Consequently, the kilogram is the only SI base unit
SI base unit
The International System of Units defines seven units of measure as a basic set from which all other SI units are derived. These SI base units and their physical quantities are:* metre for length...
that has an SI prefix
SI prefix
The International System of Units specifies a set of unit prefixes known as SI prefixes or metric prefixes. An SI prefix is a name that precedes a basic unit of measure to indicate a decadic multiple or fraction of the unit. Each prefix has a unique symbol that is prepended to the unit symbol...
as part of its unit name.
See also
- International System of UnitsInternational System of UnitsThe International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...
(SI) - GramGramThe gram is a metric system unit of mass....
- KilogramKilogramThe kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...
- Kilogram-forceKilogram-forceA kilogram-force , or kilopond , is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a gravitational field...
- Metric systemMetric systemThe metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...
- MassMassMass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
- SI base unitSI base unitThe International System of Units defines seven units of measure as a basic set from which all other SI units are derived. These SI base units and their physical quantities are:* metre for length...
s - SI derived unitSI derived unitThe International System of Units specifies a set of seven base units from which all other units of measurement are formed, by products of the powers of base units. These other units are called SI derived units, for example, the SI derived unit of area is square metre , and of density is...
s