The oldest material unit of measurement today is the standard of mass. The international definition of the ideal kilogram has not changed since 1875. A kilogram was defined as the weight of one cubic decimeter of water at its highest density, at a temperature of 4 degrees. In Russia, a copy of the ideal kilogram is kept at the St. Petersburg Research Institute of Metrology named after. D.I. Mendeleeva.
A cubic decimeter of water from the Parisian River Seine was immortalized in a platinum-iridium prototype. Pure platinum does not oxidize and has greater density and hardness. But platinum is not an ideal metal; it reacts too sensitively to temperature changes. The problem was solved by adding iridium. 90% platinum and 10% iridium became the perfect material for storing weights in the 19th century. Oddly enough, this prototype still serves as a universal weight standard. Although its accuracy is not as high as that of other more modern standards. If the unit of time is reproduced with an error of several units of the 16th digit, then, say, quantities such as electrical, the same kilogram, the same thermal quantities, this is something like the ninth, eighth digit. That is, the difference is 6-7 orders of magnitude, that is, tens of millions of times. The kilogram is the most problematic standard in the world. Despite careful storage, the heavy-duty kettlebell gradually changes in weight.
Over the past 100 years, relative to the international standard, the international prototype, which is stored in Paris, the Russian kilogram standard has changed to 30 micrograms. Evaporation and mechanical wear occur from the surface of the metal; atoms of oxygen, hydrogen, and heavy metals are deposited on the metal. As long as we use this prototype, this cannot be avoided. What are the consequences of a deviation from the weight standard of 30 micrograms? What is one microgram? Thousandth of a milligram or millionth of a gram? 500 micrograms of regular apples is 1 cubic millimeter.
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In the household trade sector, no one will notice such changes. Another thing is pharmaceuticals. If there is a mistake in the manufacture of a medicine by one milligram, the consequences can be very tragic. Scientists around the world are working to create an updated standard of mass - a ball of ultra-pure silicon. Silicon has an ideal crystal lattice. Using force microscopes, metrologists will determine the exact number of atoms in one kilogram of silicon.
Time standards.
Already, modern people are faced every minute with the operation of the most complex metrological devices, without even knowing it. For example, mobile communications, mobile phone. . Who ever wondered why it works? I pressed the button - it works. In order for mobile communications to work, these cell stations, these towers that people still see, must be strictly synchronized with each other, that is, linked in time. And this timing to ensure the functionality of mobile communications is in millionths of a second.
People measured time by the revolutions of the heavenly bodies until the mid-20th century. But this method turned out to be far from ideal. The Earth is slowly slowing down in its rotation. Moreover, it does not rotate quite evenly. That is, roughly speaking, sometimes faster, sometimes slower. Metrology faced the question: how to calculate and store an accurate time interval? In 1967, a new standard was created.
This is 9 billion 192 million 631 thousand 770 periods of radiation of the cesium 133 atom in the ground state. When so many periods of radiation are counted, this is one second. And there are devices, specific devices, physical installations that implement this. Why cesium? It is the most insensitive to external influences. In Russia, the main standard of time is stored in the Moscow Research Institute of Physical, Technical and Radio Engineering Measurements. A very complex set of devices - keepers of both frequency and time scales - is responsible for determining the exact time. The Russian time standard is one of the best world standards. Its relative error is no more than 1 second in half a million years.
Only the invention of atomic clock time standards made it possible to create the most complex navigation systems: GPS and Glonass. In order for movement on the road to be convenient, the system must determine the position of the car within one meter. A meter for a satellite is 3 billionths of a second. Information about the vehicle's movement is being updated at such incredible speed. Using satellite signals, metrologists around the world exchange data on the exact time. The installations record the difference in the clock readings of the laboratories and the satellite. Next, the data from all laboratories are compared using a special program. The result is synchronized international atomic time. The satellite complex located near Moscow transmits data into space with an error of only one nanosecond, that is, one billionth of a normal second.
ʼʼKeepers of timeʼʼ. No matter how mysterious the position of these specialists may sound, the atomic clocks at the Institute of Radio Engineering Measurements, by which the whole country checks their hands, do not look fantastic. Although they operate here in nano and pico seconds, a person cannot feel such precision.
“When they talk about the exact time, then for the most part, at the everyday level, people hear transmitting signals to check the time on the radio, “pi, pi, pi,” this is the exact time. In fact, this time from our bell tower is not very accurate, very modest accuracy. The national time scale is the one we are creating here. The error per day is approximately a few hundred billionths of a second per day. It takes millions of years for an atomic clock to move forward or fall behind by a second. The main consumers of reference time are cellular communications and navigation.
“Modern radio navigation systems use electromagnetic signals that travel at the speed of light.” In a billionth of a second, light travels 30 centimeters. If we want to use GLONASS to determine our location with meter accuracy, this means that the entire system must operate with an error of one to two billionths of a second. GPS, GLONASS - a system of satellites that are designed to accurately determine geographic coordinates and exact time. GPS, otherwise called NAVSTAR, is an American constellation of satellites, GLONASS is Russian.
Atomic time is as old as astronautics. Half a century. The rapid development of quantum physics led to the appearance of the first atomic clock in the mid-20th century, and the International Committee on Weights and Measures decided to switch to the atomic standard. The modern time standard is a cesium frequency reference. The device is behind glass, you cannot enter the room, because... The device has “greenhouse conditions”, they are created specifically so that the outside world does not interfere with work. And if we talk about accuracy, then this is a ten-millionth of a billionth of a second. It’s difficult to pronounce and comprehend. It would seem that what else in nature should be more accurate? It turns out, maybe neutron stars. Pulsars or neutron stars are what stars turn into after they die. Οʜᴎ explode, quickly spin. A ball appears with an iron shell and a huge force of attraction, emitting waves with strict periodicity. “The electric field pulls out electrons directly from the surface of the star, and it is iron, they fly, accelerate, and in the direction of their movement they emit different waves.” Pulsars were discovered by English astronomers in 1967. The information was secret for a long time. They thought it was a signal from extraterrestrial civilizations. After all, natural objects cannot produce radio signals with such a frequency. They even brought in cryptographers. However, the hypothesis about the artificial origin of the outbreaks was not confirmed. “If we wanted to make contact with someone,” says Mikhail Popov, “we can submit call signs, they do not carry any information, impulses that should not be formed in life. Until pulsars were discovered, they thought so. The idea of using pulsars to synchronize earth clocks was proposed by Russian scientists. The accuracy of stellar pulses exceeds the atomic standard by several orders of magnitude. It turns out that soon the Universe will answer the question: “What time is it?”
There is no such thing as too much precision. That is why a system of international measurements has been created and exists throughout the world, expressed in the standards of all measurements known to man. And only the kilogram standard stands out in the line of units of measurement. After all, he is the only one who has a physical, actually existing prototype. How much the international standard kilogram weighs and in which country is stored, we will answer in this article.
Why are standards needed?
Does a kilogram of, for example, oranges weigh the same in Africa and in Russia? The answer is yes, almost. And all thanks to the international system for determining the standards of the standard kilogram, meter, second and other physical parameters. Measurement standards are necessary for humanity to ensure economic activity (trade) and construction (unity of drawings), industrial (unity of alloys) and cultural (unity of time intervals) and many other areas of activity. And if your iPhone breaks in the near future, it is very likely that this happened due to changes in the weight of the most important mass standard.
History of standards
Each civilization had its own standards and standards, which replaced each other over the centuries. In Ancient Egypt, the mass of objects was measured in kantars or kikkars. In Ancient Greece these were talents and drachmas. And in Russia, the mass of goods was measured in pounds or spools. At the same time, people of different economic and political systems seemed to agree that the unit of measurement of mass, length or other parameter would be comparable to a single contractual unit. Interestingly, even a pood in ancient times could differ by a third among traders from different countries.
Physics and standards
Agreements, often verbal and conditional, worked until a person took up science and engineering seriously. With the understanding of the laws of physics and chemistry, the development of industry, the creation of the steam boiler and the development of international trade, the need for more precise uniform standards arose. The preparatory work was long and painstaking. Physicists, mathematicians, and chemists all over the world worked to find a universal standard. And first of all, the international standard of the kilogram, because it is from this that other physical parameters are based (Ampere, Volt, Watt).
Metric Convention
A significant event took place on the outskirts of Paris in 1875. Then, for the first time, 17 countries (including Russia) signed the metric convention. This is an international treaty that ensures uniformity of standards. Today, 55 countries have joined it as full members and 41 countries as associate members. At the same time, the International Bureau of Weights and Measures and the International Committee of Weights and Measures were created, whose main task was to monitor the unity of standardization throughout the world.
Standards of the first metric convention
The standard of the meter was a ruler made of an alloy of platinum and iridium (9 to 1) with a length of one forty-millionth of the Paris meridian. A kilogram standard made from the same alloy corresponded to the mass of one liter (cubic decimeter) of water at a temperature of 4 degrees Celsius (highest density) at standard pressure above sea level. The standard second became 1/86400 of the duration of an average solar day. All 17 countries participating in the convention received a copy of the standard.
Place Z
The prototypes and the original standard are today stored in the Chamber of Weights and Measures in Sèvres near Paris. It is in the outskirts of Paris that the place where the standard kilogram, meter, candela (light intensity), ampere (current intensity), kelvin (temperature) and mole (as a unit of matter, there is no physical standard) is stored. The system of weights and measures that is based on these six standards is called the International System of Units (SI). But the history of standards did not end there; it was just beginning.
SI
The system of standards that we use - SI (SI), from the French Systeme International d'Unites - includes seven basic quantities. These are meter (length), kilogram (mass), ampere (current), candela (luminous intensity), kelvin (temperature), mole (amount of substance). All other physical quantities are obtained by various mathematical calculations using basic quantities. For example, the unit of force is kg x m/s 2. All countries in the world except the USA, Nigeria and Myanmar use the SI system for measurements, which means comparing an unknown quantity with a standard. And a standard is the equivalent of a physical value that everyone agrees is absolutely accurate.
How much is the standard kilo?
It would seem something simpler - the standard of 1 kilogram is the weight of 1 liter of water. But in reality this is not entirely true. What to take as a standard kilogram from about 80 prototypes is a rather complicated question. But by chance, the optimal alloy composition was chosen, which lasted for more than 100 years. The standard kilogram of mass is made of an alloy of platinum (90%) and iridium (10%), and is a cylinder whose diameter is equal to its height and is 39.17 millimeters. Its exact copies were also made, amounting to 80 pieces. Copies of the kilogram standard are located in the countries participating in the convention. The main standard is stored in the outskirts of Paris and covered in three sealed capsules. Wherever the kilogram standard is located, reconciliation with the most important international standard is carried out every ten years.
The most important standard
The International Standard of the Kilogram was cast in 1889 and is kept in Sèvres, France, in a safe at the International Bureau of Weights and Measures, covered with three sealed glass covers. Only three high-ranking representatives of the bureau have the keys to this safe. Along with the main standard, the safe also contains six of its duplicates or successors. Every year, the main measure of weight, which is accepted as the standard kilogram, is ceremonially removed for examination. And every year he becomes thinner and thinner. The reason for this weight loss is the detachment of atoms when extracting the sample.
Russian version
A copy of the standard is also available in Russia. It is stored at the All-Russian Research Institute of Metrology. Mendeleev in St. Petersburg. These are two platinum-iridium prototypes - No. 12 and No. 26. They are on a quartz stand, covered with two glass covers and locked in a metal safe. The air temperature inside the capsules is 20 °C, humidity 65%. The domestic prototype weighs 1.000000087 kilograms.
The standard kilogram is losing weight
Standard comparisons showed that the accuracy of national standards is about 2 micrograms. All of them are stored under similar conditions, and calculations show that the standard kilogram loses 3 x 10 −8 weight over a hundred years. But by definition, the mass of the international standard corresponds to 1 kilogram, and any changes in the real mass of the standard lead to a change in the very value of the kilogram. In 2007, it turned out that a kilogram cylinder began to weigh 50 micrograms less. And his weight loss continues.
New technologies and a new standard of weight measurement
To eliminate errors, a search is underway for a new structure of the kilogram standard. There are developments to determine a certain amount of silicon-28 isotopes as a standard. There is a project “Electronic kilogram”. The National Institute of Standards and Technology (2005, USA) designed a device based on what is necessary to create an electromagnetic field capable of lifting 1 kg of mass. The accuracy of such a measurement is 99.999995%. There are developments in determining mass in relation to the rest mass of the neutron. All these developments and technologies will allow us to move away from being tied to a physical mass standard, to achieve higher accuracy and the ability to carry out reconciliation anywhere in the world.
Other promising projects
And while the world's scientific luminaries are determining which way to solve the problem is more reliable, the most promising is considered to be a project in which the mass will not change over time. Such a standard would be a cubic body made of atoms of the carbon-12 isotope with a height of 8.11 centimeters. There would be 2250 x 281489633 carbon-12 atoms in such a cube. Researchers from the US National Institute of Standards and Technology propose to determine the kilogram standard using Planck's constant and the formula E=mc^2.
Modern metric system
Modern standards are not at all what they were before. The meter, originally related to the circumference of the planet, today corresponds to the distance that a ray of light travels in one 299,792,458th of a second. But a second is the time during which 9192631770 vibrations of a cesium atom pass. The advantages of quantum precision in this case are obvious, because they can be reproduced anywhere on the planet. As a result, the only standard that exists physically remains the kilogram standard.
How much does the standard cost?
Having existed for more than 100 years, the standard is already worth a lot as a unique and artifact item. But in general, to determine the price equivalent, it is necessary to calculate the number of atoms in a kilogram of pure gold. The number will come from about 25 digits, and this does not take into account the ideological value of this artifact. But it is too early to talk about selling the kilogram standard, because the only remaining physical standard of the international system of units has not yet been disposed of.
In all time zones on the planet, time is determined relative to UTC (for example, UTC+4:00). What is noteworthy is that the abbreviation has no decoding at all; it was adopted in 1970 by the International Telecommunication Union. Two options were proposed: the English CUT (Coordinated Universal Time) and the French TUC (Temps Universel Coordonné). We chose a medium neutral abbreviation.
At sea, the "knot" measurement is used. To measure the ship's speed, they used a special log with knots at the same distance, which they threw overboard and counted the number of knots over a certain period of time. Modern devices are much more advanced than a rope with knots, but the name remains.
The word scrupulousness, the meaning of which is extreme precision and accuracy, came into languages from the name of the ancient Greek standard of weight - scruple. It was equal to 1.14 grams and was used when weighing silver coins.
The names of monetary units also often originate in the names of measures of weight. Thus, sterling in Britain was the name given to coins made of silver; such coins weighed a pound. In Ancient Rus', “silver hryvnias” or “gold hryvnias” were in use, which meant a certain number of coins expressed in weight equivalent.
The strange measurement of car horsepower has a very real origin. The inventor of the steam engine decided to demonstrate the advantage of his invention over traction transport in this way. He calculated how much a horse could lift per minute and designated this amount as one horsepower.
International prototype without protective case
September 2014 marks 125 years since the birth of the international prototype of the kilogram. The decision to create a standard was made at the General Conference of Weights and Measures on September 7-9, 1889 in Paris.
It is kept at the International Bureau of Weights and Measures near Paris and is a cylinder with a diameter and height of 39.17 mm made of a platinum-iridium alloy (90% platinum, 10% iridium). This composition was chosen due to the high density of platinum, so that the standard can be made of a relatively small size: smaller in height than a matchbox.
National prototype of the British kilogram in a protective case, the 18th copy of the international prototype
The mass of the international prototype is approximately equal to 1 liter of water at a temperature of 4°C, and its weight depends on the altitude above sea level and the force of gravity.
When the international prototype was made, 40 copies were made from the same platinum-iridium alloy along with it. They were sent to national bureaus of weights and measures in different countries so that scientists did not have to refer to the main standard each time to make measurements.
National prototypes are checked against the main prototype every 40 years. The last test took place in 1989, and then the maximum difference in weight was 50 micrograms. These deviations worry scientists. They understand that the mass of a given sample changes over time due to physical damage and other artifacts.
The national prototype is kept in the safe of the National Physical Laboratory
Unfortunately, this anniversary will most likely be the last for the international prototype. Two experiments to create more accurate mass standards are now nearing completion. Their goal is to determine mass through a natural constant, rather than through a reference sample.
One of the experiments involves determining the kilogram using Planck's constant. To do this, they measure the current passing through a [wired] coil in a magnetic field in relation to the force of gravity acting on a kilogram, explain specialists from the UK National Physical Laboratory, where in honor of the 125th anniversary of the kilogram they opened a festive section on the website. It was in Great Britain that the experiment on watt balance began in 1975, which is now being continued in Canada.
Another method is proposed by German experts: within the framework of the Avogadro project, they create a silicon sphere the size of a grapefruit, which contains about 50 septillion silicon-28 atoms.
Avogadro's Silicon Sphere
Since the mass of silicon and the density of the substance are known, the reference value of a kilogram can be tied to the volume of the sphere and, accordingly, to Avogadro’s constant.
Measuring the mass of Avogadro's sphere
The kilogram remained the last SI unit, which is expressed through a physical standard. This indicates that 125 years ago, physicists very wisely chose the material to make the prototype. And even if it is soon taken out of use, it has served well over the years.
Federal Agency for Education
State educational institution of higher professional education
SIBERIAN FEDERAL UNIVERSITY
POLYTECHNICAL INSTITUTE
Department of Instrument Engineering and Telecommunications
ABSTRACT
STANDARD FOR LENGTH AND WEIGHT
Completed:
st gr. R 54-2
A. E. Shamova
Checked:
teacher
Krasnoyarsk 2007
Standard is a measuring instrument (a set of measuring instruments) designed to reproduce and store a unit of quantity and transfer its size to other, less accurate, measuring instruments.
International standards are stored at the International Bureau of Weights and Measures, located in Sèvres, a suburb of Paris. In accordance with international agreements, with their help, comparisons of national standards of different countries are periodically carried out, including mutual comparisons of national standards. For example, national meter and kilogram standards are compared once every 20-25 years, and volt and ohm standards - once every three years.
Standard unit of length.
In 1971, the French National Assembly adopted the length of ten millionths of a quarter arc of the Parisian meridian as the unit of length, the meter. At that time in France the toise was used as a unit of length. The ratio between meter and toise turned out to be equal 1 m = 0.513074 toise.
But already in 1837, French scientists established that a quarter of the meridian contains not 10 million, but 10 million 856 m. Around the same period of time, it became obvious that the shape and size of the Earth are changing over time. Therefore, in 1872, on the initiative of the St. Petersburg Academy of Sciences, an international commission was created, which decided not to create updated meter standards, but to accept the meter of the Archive of France as the initial unit of length.
In 1889, 31 meter standards were produced in the form of a platinum-iridium rod of an X-shaped cross-section, which, as follows from consideration Rice. 1 fits into a square.
The length of the ruler is 102 cm. Three strokes are applied on each of its ends at a distance of 0.5 mm from each other. Thus, the distance between the middle strokes is 1 m.
The error of platinum-iridium line meters is. Already at the beginning of the 20th century. this error turned out to be quite large, not satisfying the requirements for length measurements.
In 1960, the XI General Conference on Weights and Measures adopted a new definition of the meter: meter is a length equal to 1650763,73
wavelength in vacuum of radiation corresponding to the transition between levels 
And 
atom of krypton-86.
The krypton meter standard consists of a gas discharge lamp filled with krypton-86 placed in a Dewar flask containing liquid nitrogen ( Rice. 2). When an electrical voltage of +1500 is applied in the lamp, a glow of excited krypton-86 atoms is formed. The capillary in which the glow occurs (with an internal diameter of about 3 mm) has an optical output to an automatic interference photoelectric comparator. Using an interference comparator, the distance between the lines is determined, which makes it possible to find the number of wavelengths that fit between the middle lines of the ruler ( Rice. 1). In fact, not the entire number of wavelengths that “fit” in a meter is determined, but the difference between the measured length and the reference length reproduced by the gas-discharge lamp is estimated. The wavelength and energy characteristics of the glow are measured using spectrointerferometers.
The error in reproducing the meter, estimated by the standard deviation of the measurement result, using this standard decreased significantly compared to the error of the platinum-iridium prototype of the meter and amounted to 
.
New meter standard.
Increasing the accuracy of the length standard became possible with the possibility of extending absolute frequency measurements (in the radio frequency spectrum of oscillations) to the optical range and the development of highly stable lasers, which made it possible to clarify the value of the speed of light. In 1983, the XVII General Conference on Weights and Measures adopted a new definition of the meter: “A meter is the length of the path traveled by light in a vacuum in 1/299,792,458 of a second (exact).” This definition of the meter is fundamentally different from the definition of 1960: the “krypton” meter was not directly related to time, the new meter is based on the standard unit of time - the second and the known value of the speed of light.
For many years to come, metrology and technology will use the speed of light value established by the XVII General Conference on Weights and Measures.
Currently, to ensure a high degree of stabilization of the most important parameter of laser radiation - frequency, helium-neon lasers at the radiation wavelength are widely used 
µm (infrared region of the spectrum) and 
µm (visible region of the spectrum), respectively stabilized by saturated absorption in methane ( Not-Ne/CH 4
) and molecular iodine ( Not-Ne/I 2
).
Lasers based on ( Not-Ne/CH 4 ) in terms of frequency reproducibility, they are close to the cesium standard, which is the basis of the time and frequency standard. Operating in the visible range of the spectrum Not-Ne/I 2 The laser makes it possible to realize a new definition of the meter through the speed of light propagation in a vacuum. The presence of radiation at two wavelengths (µm and µm) makes it possible to ensure high accuracy of measurements using an interferometer. The second is reproduced using cesium frequency standards in the microwave range of electromagnetic oscillations, and the new meter is reproduced in the optical frequency range, i.e., several orders of magnitude higher than the frequencies used in the time and frequency standard. Thus, a “bridge” is needed to transmit the reference frequency of the cesium standard to the optical part of the range.
A set of equipment for “transferring” frequency measurements in a “radio frequency” time standard to measuring the frequency of highly stable lasers (in the optical range) was called a radio-optical frequency bridge (ROFB). ROFM made it possible to obtain the highest accuracy in measuring the speed of light in a vacuum and consider it as a fundamental physical constant, and was the basis for the creation of a single standard of frequency - time - length. This standard includes a time and frequency standard, RFCM equipment, as well as a new meter standard, including Ne-Ne lasers, wavelength comparison interferometer Not-Ne/CH 4 lasers and Not-Ne/I 2 lasers, an interferometer that directly forms a unit of length - a meter. This standard has a reproduction error in the form of a standard deviation of the measurement result of about , the systematic component does not exceed , i.e., more than three orders of magnitude less than the error in reproducing a meter using a “krypton” meter.
Standard unit of mass.
The international prototype of the kilogram was approved at the First General Conference on Weights and Measures in 1889 as a prototype of a unit of mass, although at that time there was no clear distinction between the concepts of mass and weight, and therefore the mass standard was often called the weight standard.
The standard includes:
A copy of the international prototype of the kilogram (No. 12), which is a platinum-iridium weight in the form of a straight cylinder with rounded ribs with a diameter and height of 39 mm. The prototype of the kilogram is stored at VNIIM named after. D.I. Mendeleev (St. Petersburg) on a quartz stand under two glass covers in a steel safe. The standard is stored while maintaining the air temperature within (20±3)°C and relative humidity 65%. In order to preserve the standard, two secondary standards are compared with it every 10 years. They are used to further convey the size of a kilogram;
Equal-arm prismatic scales for 1 kg No. 1 with remote control (in order to eliminate the influence of the operator on the ambient temperature), manufactured by Ruprecht, and equal-arm modern scales for 1 kg No. 2, manufactured at VNIIM. D. I. Mendeleev. Scales No. 1 and No. 2 serve to transfer the size of a unit of mass from prototype No. 12 to secondary standards.
On Rice. 3 The kilogram standard in its modern form is shown. On the right in the figure, a double-circuit glass protective device is shown together with the prototype of kilogram No. 12.
The error in reproducing a kilogram, expressed by the standard deviation of the measurement result, is 
.
More than 100 years have passed since the prototypes of the kilogram were created. Over the past period, national standards were periodically compared with the international standard. IN Table 1 The results of only two comparisons (they also took place after 1954) of kilogram standards are presented.
Table 1
New kilogram standard
It was recently discovered that the Paris kilogram standard is not entirely accurate. Solve this problem, i.e. A program involving scientists from eight countries will help create a new mass standard. The first 140 grams of the substance for the new standard already exist. This is ultra-pure silicon, consisting of 99.99% of the silicon-28 isotope.
In three years there will already be 5 kg of such silicon. This is enough to make a one-kilogram ball, the number of silicon-28 atoms in which will be precisely known. And then the antediluvian weight in the Parisian Chamber of Weights and Measures will be replaced by a standard, not only the mass, but also the number of atoms in which will be determined with the utmost accuracy for today's world science.
Scientists, and especially physicists, have long dreamed of obtaining a new, truly accurate standard of mass. Some of the work has been completed, but there is still a huge amount of work ahead. The fact is that in microelectronics they have mostly learned to produce chemically pure silicon. But natural silicon consists of three isotopes with naturally different masses of atoms - 28 (92%), 29 (5%) and 30 (3%) carbon units. And for the mass standard, only identical atoms are needed. Only after obtaining isotopically pure silicon in Russia will they make an ideal smooth ball in Australia. And then the ball will be checked for a long time and carefully in Germany and France. Thus, for the first time it becomes possible to clarify one of the most fundamental chemical quantities - Avogadro's number.
Reference- is a measure or measuring device used to reproduce, store and transmit units of any quantity. The standard approved as the reference standard for the country is called the State Standard.
Brief historical background
A person needs to describe the reality around him, and in such a way that other people understand him. It is for this reason that all civilizations created their own measurement systems.
The modern measurement system originates in the 18th century in France. It was then that a commission of famous scientists proposed their own decimal metric system of measures. Initially, the metric system included the meter, square meter, cubic meter and kilogram (mass of 1 cubic decimeter of water at 4 °C), capacity - liter, that is, 1 cubic meter. decimeter, land area - are (100 square meters) and ton (1000 kilograms).
In 1875, the Metric Convention was signed, the purpose of which was to ensure international unity of the metric system. On the basis of this metric system, their own systems and units arose, which did not correlate well with each other, so in 1960 the International System of Units SI (SI) was adopted. The SI uses several basic units of measurement: meter, kilogram, ampere, kelvin, candela, mole, as well as additional units for measuring angles - radians and steradians.
Mass standard
To keep the measurement error to a minimum, scientists create large and difficult-to-use complexes. However, the standard of mass remains unchanged - it is a platinum-iridium weight made in 1889. A total of 42 standards were produced, two of which went to Russia.
The kilogram standard is stored in St. Petersburg, at VNIIM named after. D.M. Mendeleev (it was he who initiated the adoption by Russia of the French metric system). The standard stands on a quartz stand, under two glass covers (to prevent dust from entering), inside a steel safe. The reference scales, which are part of the standard, stand on a special foundation. This structure weighs 700 tons and is not connected to the walls of the building so that vibrations do not distort the measurements.
Temperature and humidity are maintained at a constant level, and all operations are carried out using manipulators to eliminate the influence of body temperature and random dust particles when using human labor. The error of the Russian mass standard does not exceed 0.002 mg.
The essence of the measuring operation remains the same and comes down to comparing two masses when weighing. Ultra-sensitive scales have been invented, weighing accuracy is increasing, thanks to which new scientific discoveries are emerging, but still the mass standard is a source of headaches for metrologists around the world.
The kilogram is in no way connected with physical constants or with any natural phenomena. Therefore, the standard is protected more carefully than the apple of an eye - literally, they do not allow a speck of dust to land on it, because a speck of dust is already several divisions on a sensitive scale.
The international prototype of the standard is taken out of storage no more than once every fifteen years, the Russian one - once every five years. All work is carried out with secondary standards (only they can be compared with the main one); from the secondary standard, the mass value is transferred to the working standards, and from them to the standard sets of weights.
Years pass, and the standard kilogram becomes thinner or fatter. It is fundamentally impossible to determine what exactly is happening to it - the sameness of all mass standards is a disservice here. Therefore, many metrology laboratories around the world are intensively searching for new ways to create and determine the kilogram standard.
For example, there is an idea to tie it to volts and ohms, units of measurement of electrical quantities, and weigh it using a standard unit of current - an ampere scale. Theoretically, one can imagine the kilogram standard in the form of an ideal crystal containing a known number of atoms of a certain chemical element (more precisely, one of its isotopes). But methods for growing such crystals are not yet known.