The Birth of the Kilogram
In 1793, the chemist Antoine Lavoisier and the crystallographer René Just Ailly proposed to the French Commission of Weights and Measures to use the gram as a unit of mass—the mass of one cubic centimeter of pure water at the melting point of ice. For practical convenience, the already mentioned Lenoir made a standard copper weight weighing 1000 g. Since 1795, the new unit of mass has been called the kilogram (one cubic decimeter of water, or, more simply, one liter).
Four years later, the proposal of the physicist Louis Lefebvre-Guigneau to weigh water at the temperature of its maximum density (4 °C) was accepted. The new kilogram standard was made of platinum and placed in the archives of the Republic for safekeeping. Several copies were also made for use as samples to manufacture weights. However, measurements made in the 19th century showed that the mass of 1 cubic dm of water is 0.028 g less than the mass of the archive standard. To avoid any future misunderstandings, the International Commission on Standards of the Metric System decided in 1872 to adopt the mass of the prototype, the archive kilogram, as the unit of mass.
In 1880, the international kilogram standard was produced from an alloy consisting of 90% platinum and 10% iridium. Four of the six official copies of this standard that currently exist were also made. All of them are now kept under two hermetically sealed glass domes in a safe located in the International Bureau of Weights and Measures (BIPM) basement in Sèvres, near Paris.
Standards of the kilogram
In 1889, the 1st General Conference on Weights and Measures adopted the definition of the kilogram as equal to the mass of the international standard. This definition is still valid today.
However, in Russia, the kilogram officially became the main unit of weight only in 1918, with the decree "On the introduction of the international metric decimal system of measures and weights".
In 1875, the Metric Conference founded the International Bureau of Weights and Measures, whose goal was to create a unified system of measurements that would be used worldwide, but this is the topic of another article.
As we can see, various measures have existed for almost as long as humanity has. Science and technology are constantly evolving, and in the process of their development, new types of measurements and their units appear and are improved. These processes are especially intense these days, and we cannot even imagine what other units of measurement will appear in a few decades.
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