Scales - one of the oldest inventions of mankind, which is still used today. Street vendors began to use the simplest models in ancient Egypt. Since then, people have been concerned about the problem of accurately determining weight.

## Metric

The metric system was developed in France during the revolution. French peasants were given the right to free trade. But they soon realized that the system of measures adopted at that time was inconvenient for constant calculations. It was difficult to convert from one unit of weight to another. For example, each landowner could set his own value for the pound. As a result, one hundred different pounds were known. The French decided to create a new, more convenient system of measures. They took as a basis the principle of converting one unit of measure into another by multiplying or dividing by the number ten or its power.

## Kilogram

The "grav" was taken as a measure of mass. Its standard was the weight of a cubic decimeter of water under certain conditions. This method of determining the weight was not very convenient. After all, it required very precise instruments. Not everyone liked the consonance of the name of the measure with the title of count. Eventually it was changed tograms and began to designate them one thousandth of the standard. For convenience, merchants began to use a measure of a thousand grams - a kilogram. After 100 years, the kilogram standard was replaced by a cylinder made of an alloy of platinum and iridium.

Kilogram is the only unit of the metric system that has a prefix in its name. It is also the last unit of measure for which the reference is used. Over time, the platinum-iridium cylinder loses some of its mass. But at the same time, it still remains the current standard of the kilogram. Other units of measurement in the metric system are tied to it. Currently, scientists are considering options for determining the kilogram through physical constants. During the reign of Napoleon, the metric system spread throughout Europe. Unconquered by France, England retained its own system of measures. The main units of measurement of weight in it are the pound and the stone. It is also used in the United States of America and Canada.

## Measures of mass in Russia

In Russia, units were used as measures, which were based on the mass of cereal grains. A unified system of weight measures was introduced during the reign of Prince Vladimir. They introduced an annual check of the scales. Peter the Great tightened fines for false scales. In 1730, the scales of the St. Petersburg customs were considered especially accurate. They were used as exemplary to create test at the Senate.

In 1841, the Depot of Exemplary Weights and Measures was built in St. Petersburg. Merchants brought instruments for testing into it. Standards of measures were stored in the depot. The tasks of the organization included the creation of tables of Russians andforeign measures, production of standards for distribution to the regions. Later, the Main Chamber of Weights and Measures was founded. In 1882 D. I. Mendeleev headed the State Service for Weights and Measures. In 1898, he made the pound standard.

## Metric conversion

Russia switched to the metric system in 1918. Prior to this, the main Russian measure of mass was the pound (0.41 kg). He was accepted under Tsar Alexei Mikhailovich. This unit was also called the hryvnia. The hryvnia was used to weigh expensive metals. This word was also used to designate a monetary unit.

A pood was equal to forty pounds. Ten pounds were Berkovets. This name comes from the name of the island of Bjork. A standard barrel weighed 1 Berkovets. Smaller units of weight, the lot and the spool, were also used. Old measures of mass are still found in proverbs and sayings. The transition took seven years. Only in 1925 was a unified system established throughout the Soviet Union. Carat, gram, kilogram and ton were adopted as the main units of weight measurement.