And did you know that...
Did the Swedish scientist A. Celsius test the temperature scale? “I repeated the experiments for two years, in different weather, and always found exactly the same point on the thermometer. I placed the thermometer not only in the melting ice, but also in the snow when it began to melt. I also placed a cauldron of melting snow together with a thermometer in a heating stove and always found that the thermometer showed the same point, if only the snow lay tightly around the thermometer ball. This is how A. Celsius described the results of his experiments in the 18th century.
There is a very fusible metallic substance - Wood's alloy? If you pour a teaspoon out of it, then in a glass of hot tea it will melt and drain to the bottom of the glass!
At the top of Mount Everest, the highest point on Earth, is the atmospheric pressure three times less than normal? At this pressure, water boils at a temperature of only 70 ° C? In “boiling water” of such a temperature, even tea cannot be brewed properly.
When removing a hot saucepan from the stove, do you need to use only a dry rag or mitten? If they are wet, you risk getting burned, since water conducts heat 25 times faster than air between the hairs of the fabric.
If coal or firewood had the same good thermal conductivity as metals, then it would be simply impossible to set fire to them? The heat supplied to them (for example, from a match) would be very quickly transferred into the thickness of the material and would not heat the ignited part to the ignition temperature.
On their way to Earth, the sun's rays travel through the vacuum of space for a huge distance - 150 million kilometers? And despite this, for every square meter of the earth's surface, an energy flow with a power of ≈ 1 kW falls. If this energy "fell" on the kettle, then it would boil in just 10 minutes!
If a person could see thermal radiation, then, once in a dark room, he would see a lot of interesting things: brightly shining pipes and radiators surrounded by light winding streams of warm air? The same streams would have been above the music center, TV.
In the 19th century, were frozen foods considered hopelessly spoiled? And only the difficulties of food supply, which became an obstacle to the development of large cities, forced to overcome prejudices. AT late XIX- At the beginning of the 20th century, laws were issued in many countries prescribing the construction of special structures - refrigerators.
Heat pumps that allow you to regulate the temperature and humidity of the air - air conditioners - began to be used already at the beginning of the last century? Since the 1920s, they have been installed in crowded buildings and premises: theaters, hotels, restaurants.
Thermometer
Thermometer (Greek θέρμη - heat; μετρέω - I measure) - a device for measuring the temperature of air, soil, water, and so on. There are several types of thermometers:liquid; mechanical; electronic; optical; gas; infrared.
Galileo is considered to be the inventor of the thermometer: in his own writings there is no description of this device, but his students, Nelly and Viviani, testified that already in 1597 he made something like a thermobaroscope (thermoscope). Galileo studied at this time the work of Heron of Alexandria, who already described a similar device, but not for measuring degrees of heat, but for raising water by heating. The thermoscope was a small glass ball with a glass tube soldered to it. The ball was slightly heated and the end of the tube was lowered into a vessel with water. After some time, the air in the ball cooled, its pressure decreased, and the water, under the action of atmospheric pressure, rose up in the tube to a certain height. Subsequently, with warming, the air pressure in the ball increased and the water level in the tube decreased; when cooled, the water in it rose. With the help of a thermoscope, it was possible to judge only about the change in the degree of heating of the body: it did not show the numerical values of the temperature, since it did not have a scale. In addition, the water level in the tube depended not only on temperature, but also on atmospheric pressure. In 1657 Galileo's thermoscope was improved by Florentine scientists. They fitted the instrument with a scale of beads and bled the air out of the tank (ball) and tube. This made it possible not only qualitatively, but also quantitatively to compare the temperatures of bodies. Subsequently, the thermoscope was changed: it was turned upside down, and brandy was poured into the tube instead of water and the vessel was removed. The operation of this device was based on the expansion of bodies; the temperatures of the hottest summer and coldest winter days were taken as "permanent" points. All these thermometers were air and consisted of a vessel with a tube containing air, separated from the atmosphere by a column of water, they changed their readings both from temperature changes and from changes in atmospheric pressure.
Liquid thermometers are described for the first time in 1667 "Saggi di naturale esperienze fatte nell'Accademia del Cimento", where they are referred to as objects long made by skilled artisans, called "Confia", warming the glass on a fanned lamp fire and making amazing and very delicate products from it. At first these thermometers were filled with water, but they burst when it froze; they began to use wine spirit for this in 1654 according to the idea of the Grand Duke of Tuscany Ferdinand II. Florentine thermometers have survived in several copies to our time in the Galilean Museum, in Florence; their preparation is described in detail.
First, the master had to make divisions on the tube, considering its relative dimensions and the size of the ball: divisions were applied with melted enamel on a tube heated on a lamp, every tenth was indicated by a white dot, and others by black. They usually made 50 divisions in such a way that when the snow melted, the alcohol did not fall below 10, and in the sun it did not rise above 40. Good craftsmen made such thermometers so successfully that they all showed the same temperature value under the same conditions, but this is not it was possible to achieve if the tube was divided into 100 or 300 parts in order to obtain greater accuracy. The thermometers were filled by heating the bulb and lowering the end of the tube into alcohol; filling was completed using a glass funnel with a thinly drawn end that freely entered a fairly wide tube. After adjusting the amount of liquid, the opening of the tube was sealed with sealing wax, called "hermetic". From this it is clear that these thermometers were large and could serve to determine the temperature of the air, but were still inconvenient for other, more diverse experiments, and the degrees of different thermometers were not comparable with each other.
Galileo thermometer
In 1703 Amonton ( Guillaume Amontons) in Paris improved the air thermometer, measuring not the expansion, but the increase in the elasticity of air reduced to the same volume at different temperatures by pouring mercury into an open knee; barometric pressure and its changes were taken into account. The zero of such a scale was supposed to be “that significant degree of cold” at which the air loses all its elasticity (that is, the modern absolute zero), and the second constant point was the boiling point of water. The influence of atmospheric pressure on the boiling point was not yet known to Amonton, and the air in his thermometer was not freed from water gases; therefore, from his data, absolute zero is obtained at −239.5° Celsius. Another Amonton air thermometer, made very imperfectly, was independent of changes in atmospheric pressure: it was a siphon barometer, the open knee of which was extended upwards, filled from below with a strong solution of potash, from above with oil and ended in a sealed reservoir of air.
The modern form of the thermometer was given by Fahrenheit and described his method of preparation in 1723. Initially, he also filled his tubes with alcohol and only finally switched to mercury. He set the zero of his scale at the temperature of a mixture of snow with ammonia or table salt, at the temperature of the “beginning of freezing of water” he showed 32 °, and the body temperature of a healthy person in the mouth or under the arm was equivalent to 96 °. Subsequently, he found that water boils at 212° and this temperature was always the same in the same state of the barometer. The surviving copies of Fahrenheit thermometers are distinguished by their meticulous workmanship.
Mercury thermometer with Fahrenheit scale
The Swedish astronomer, geologist and meteorologist Anders Celsius finally set both permanent points, melting ice and boiling water, in 1742. But initially he set 0 ° at the boiling point, and 100 ° at the freezing point. In his work Observations of two persistent degrees on a thermometer, Celsius spoke about his experiments showing that the melting point of ice (100 °) does not depend on pressure. He also determined, with amazing accuracy, how the boiling point of water varied with atmospheric pressure. He suggested that the 0 mark (the boiling point of water) could be calibrated, knowing at what level relative to the sea is the thermometer.
Later, after the death of Celsius, his contemporaries and compatriots, the botanist Carl Linnaeus and the astronomer Morten Strömer, used this scale upside down (for 0 ° they began to take the melting point of ice, and for 100 ° - the boiling point of water). In this form, the scale turned out to be very convenient, became widespread and is used to this day.
Liquid thermometers are based on the principle of changing the volume of liquid that is poured into the thermometer (usually alcohol or mercury) as the ambient temperature changes. In connection with the ban on the use of mercury due to its health hazard in many areas activities are looking for alternative fillings for household thermometers. For example, galinstan alloy can become such a replacement. Other types of thermometers are also increasingly being used.
Mercury medical thermometer
Mechanical thermometers of this type operate on the same principle as liquid thermometers, but a metal spiral or bimetal tape is usually used as a sensor.
Window mechanical thermometer
There are also electronic thermometers. The principle of operation of electronic thermometers is based on the change in the resistance of the conductor when the ambient temperature changes. Electronic thermometers of a wider range are based on thermocouples (contact between metals with different electronegativity creates a contact potential difference depending on the temperature). The most accurate and stable over time are resistance thermometers based on platinum wire or platinum sputtering on ceramics. The most common are PT100 (resistance at 0 °C - 100Ω) PT1000 (resistance at 0 °C - 1000Ω) (IEC751). The dependence on temperature is almost linear and obeys a quadratic law at positive temperatures and a 4th degree equation at negative ones (the corresponding constants are very small, and in the first approximation this dependence can be considered linear). Temperature range -200 - +850 °C.
Medical electronic thermometer
Optical thermometers allow you to record the temperature due to the change in the level of luminosity, spectrum and other parameters when the temperature changes. For example, infrared body temperature meters. An infrared thermometer allows you to measure temperature without direct contact with a person. In some countries, there has long been a tendency to abandon mercury thermometers in favor of infrared, not only in medical institutions, but also at the household level.
Infrared thermometer
If mechanics in the 18th century becomes a mature, fully defined area of natural science, then the science of heat is essentially only taking its first steps. Of course, a new approach to the study of thermal phenomena emerged as early as the 17th century. The thermoscope of Galileo and the thermometers of the Florentine academicians, Guericke, Newton that followed him prepared the ground on which thermometry grew already in the first quarter of the new century. The thermometers of Fahrenheit, Delisle, Lomonosov, Réaumur and Celsius, differing from each other in design features, at the same time determined the type of thermometer with two constant points, which is still accepted today.
As early as 1703, the Parisian academician Amonton (1663-1705) designed a gas thermometer in which the temperature was determined using a manometric tube connected to a gas reservoir of constant volume. The theoretically interesting device, the prototype of modern hydrogen thermometers, was inconvenient for practical purposes. The Danzig (Gdansk) glassblower Fahrenheit (1686-1736) from 1709 produced alcohol thermometers with fixed points. From 1714 he began to manufacture mercury thermometers. Fahrenheit took the freezing point of water as 32°, and the boiling point of water as 212°. Fahrenheit took the freezing point of a mixture of water, ice and ammonia or common salt as zero. He named the boiling point of water only in 1724 in a printed publication. Whether he used it before is unknown.
The French zoologist and metallurgist Réaumur (1683-1757) proposed a thermometer with a constant zero point, which he took as the freezing point of water. Using an 80% solution of alcohol as a thermometric body, and in the final version, mercury, he took the boiling point of water as the second constant point, designating it as the number 80. Réaumur described his thermometer in articles published in the journal of the Paris Academy of Sciences in 1730, 1731 gg.
The Réaumur thermometer was tested by the Swedish astronomer Celsius (1701-1744), who described his experiments in 1742. exactly the same point on the thermometer. I put the thermometer not only in the melting ice, but also in extreme cold brought snow into my room on the fire until it began to melt. I also placed a cauldron of melting snow together with a thermometer in a heating stove and always found that the thermometer showed the same point, if only the snow lay tightly around the thermometer ball. After carefully checking the constancy of the melting point of ice, Celsius examined the boiling point of water and found that it depends on pressure. As a result of research, a new thermometer, now known as the Celsius thermometer, appeared. Celsius took the melting point of ice as 100, the boiling point of water at a pressure of 25 inches 3 lines of mercury as 0. The famous Swedish botanist Carl Linnaeus (1707-1788) used a thermometer with rearranged constant point values. O meant the melting point of ice, 100 the boiling point of water. Thus, the modern Celsius scale is essentially the Linnaean scale.
At the St. Petersburg Academy of Sciences, Academician Delisle proposed a scale in which the melting point of ice was taken as 150, and the boiling point of water was taken as 0. Academician PS Pallas in his expeditions of 1768-1774. in the Urals and Siberia, he used the Delhi thermometer. M.V. Lomonosov used in his research a thermometer designed by him with a scale that was inverse to the Deliverian one.
Thermometers were used primarily for meteorological and geophysical purposes. Lomonosov, who discovered the existence of vertical currents in the atmosphere, by studying the dependence of the density of atmospheric layers on temperature, cites data from which it is possible to determine the coefficient of volumetric expansion of air, which, according to these data, is approximately ]/367. Lomonosov ardently defended the priority of the St. Petersburg Academician Brown in discovering the freezing point of mercury, who on December 14, 1759, first froze mercury with the help of cooling mixtures. This was the lowest temperature reached up to that time.
The highest temperatures (without quantitative estimates) were obtained in 1772 by a commission of the Paris Academy of Sciences under the guidance of the famous chemist Lavoisier. High temperatures were obtained using a specially made lens. The lens was assembled from two concave-convex lentils, the space between which was filled with alcohol. About 130 liters of alcohol were poured into a lens with a diameter of 120 cm, its thickness reached 16 cm in the center. By focusing the sun's rays, it was possible to melt zinc, gold, and burn a diamond. As in the experiments of Brown-Lomonosov, where the "refrigerator" was winter air, so in the experiments of Lavoisier, the natural "stove" - the Sun - served as a source of high temperatures.
The development of thermometry was the first scientific and practical use of the thermal expansion of bodies. Naturally, the very phenomenon of thermal expansion began to be studied not only qualitatively, but also quantitatively. The first accurate measurements of the thermal expansion of solids were made by Lavoisier and Laplace in 1782. Their method long time was described in physics courses, starting with the course of Biot, 1819, and ending with the course of physics by O. D. Khvolson, 1923.
A strip of the test body was placed first in melting ice and then in boiling water. Data were obtained for glass of various grades, steel and iron, as well as for different grades of gold, copper, brass, silver, tin, lead. Scientists have found that depending on the method of preparing the metal, the results are different. A strip of unhardened steel increases by 0.001079 of its original length when heated by 100 °, and of hardened steel - by 0.001239. A value of 0.001220 was obtained for wrought iron, and 0.001235 for round drawn iron. These data give an idea of the accuracy of the method.
So, already in the first half of the 18th century, thermometers were created and quantitative thermal measurements began, brought to a high degree of accuracy in the thermophysical experiments of Laplace and Lavoisier. However, the basic quantitative concepts of thermal physics did not crystallize immediately. In the works of physicists of that time, there was considerable confusion in such concepts as "amount of heat", "degree of heat", "degree of heat". The need to distinguish between the concepts of temperature and the amount of heat was pointed out in 1755 by I.G. Lambert (1728-1777). However, his instructions were not appreciated by his contemporaries, and the development of correct concepts was slow.
The first approaches to calorimetry are contained in the works of the St. Petersburg academicians GV Kraft and GV Rikhman (1711-1753). Kraft's article "Various Experiments with Heat and Cold", presented to the Conference of the Academy in 1744 and published in 1751, deals with the problem of determining the temperature of a mixture of two portions of a liquid taken at different temperatures. This problem was often referred to in textbooks as the “Richmann problem,” although Richman solved a more general and more complex problem than Kraft. Kraft gave an incorrect empirical formula for solving the problem.
We find a completely different approach to solving the problem in Richmann. In the article “Reflections on the amount of heat that should be obtained when mixing liquids having certain degrees of heat”, published in 1750, Richmann poses the problem of determining the temperature of a mixture of several (and not two, as in Kraft) liquids and solves it based on principle of heat balance. “Suppose,” says Richman, “that the mass of the fluid is a; the heat distributed in this mass is equal to m; another mass in which the same heat m must be distributed as in mass a, let it be equal to a + b. Then the resulting heat
is equal to am/(a+b). Here Richmann means temperature by "heat", but the principle he formulated that "the same heat is inversely proportional to the masses over which it is distributed" is purely calorimetric. “Thus,” Richmann writes further, “the heat of mass a, equal to m, and the heat of mass b, equal to n, are uniformly distributed over the mass a + b, and the heat in this mass, i.e., in a mixture of a and b, must be equal to the sum of the heats m + n distributed in the mass a + b, or equal to (ma + nb) / (a + b) . It was this formula that appeared in textbooks as the “Richmann formula”. “In order to obtain a more general formula,” Richmann continues, “by which it would be possible to determine the degree of heat when mixing 3, 4, 5, etc. masses of the same liquid having different degrees of heat, I called these masses a, b, c, d, e, etc., and the corresponding heats are m, p, o, p, q, etc. In exactly the same way, I assumed that each of them is distributed over the totality of all masses. As a result, "the heat after mixing all the warm masses is equal to:
(am + bp + co + dp + eq), etc. / (a + b + c + d + e), etc.,
i.e., the sum of liquid masses, over which, during mixing, the heat of individual masses is evenly distributed, relates to the sum of all products of each mass and its heat in the same way as unity to the heat of the mixture.
Richmann did not yet possess the concept of the amount of heat, but he wrote and logically substantiated the completely correct calorimetric formula. He easily discovered that his formula agrees better with experience than Krafg's formula. He correctly established that his "heats" are "not the actual heat, but the excess heat of the mixture compared to zero degrees Fahrenheit." He clearly understood that: 1. "The heat of the mixture is distributed not only over its mass itself, but also over the walls of the vessel and the thermometer itself." 2. "The intrinsic heat of the thermometer and the heat of the vessel are distributed both over the mixture, and along the walls of the vessel in which the mixture is located, and along the thermometer." 3. “Part of the heat of the mixture, during that period of time while the experiment is being carried out, passes into the surrounding air ...”
Richmann accurately formulated the sources of errors in calorimetric experiments, pointed out the reasons for the discrepancy between Kraft's formula and experiment, that is, he laid the foundations of calorimetry, although he himself had not yet come to the concept of the amount of heat. The work of Richmann was continued by the Swedish academician Johann Wilke (1732-1796) and the Scottish chemist Joseph Black (1728-1799). Both scientists, relying on Richmann's formula, found it necessary to introduce new concepts into science. Wilke, investigating the heat of a mixture of water and snow in 1772, found that part of the heat disappears. From here he came to the concept of the latent heat of melting snow and the need to introduce a new concept, which later received the name "heat capacity".
Black also came to the same conclusion without publishing his results. His studies were published only in 1803, and then it became known that Black was the first to clearly distinguish between the concepts of the amount of heat and temperature, the first to introduce the term "heat capacity". Back in 1754-1755, Black discovered not only the constancy of the melting point of ice, but also that the thermometer remains at the same temperature, despite the influx of heat, until all the ice has melted. From here Black came to the concept of latent heat of fusion. Later he established the concept of latent heat of vaporization. Thus, by the 70s of the 18th century, the basic calorimetric concepts were established. Only after almost a hundred years (in 1852) was the unit-quantity of heat introduced, which later received the name "calorie". ( Clausius also speaks simply of the unit of heat and does not use the term "calorie".)
In 1777, Lavoisier and Laplace, having built an ice calorimeter, determined the specific heat capacities of various bodies. The Aristotelian primary quality-heat began to be studied by the method of exact experiment.
There were also scientific theories of heat. One, the most common concept (which Black also adhered to) is the theory of a special thermal fluid - caloric. The other, of which Lomonosov was an ardent supporter, regarded heat as a kind of motion of "insensitive particles." The concept of caloric was very well suited to the description of calorimetric facts: the Richmann formula and later formulas that take into account latent heats could be perfectly explained. As a result, the theory of caloric dominated until the middle of the 19th century, when the discovery of the law of conservation of energy forced physicists to return to the concept successfully developed by Lomonosov a hundred years before the discovery of this law.
The idea that heat is a form of motion was very common in the 17th century. f. Bacon in The New Organon, applying his method to the study of the nature of heat, comes to the conclusion that "heat is a movement of propagation, hindered and occurring in small parts." Descartes speaks more concretely and clearly about heat as about the motion of small particles. Considering the nature of fire, he comes to the conclusion that "the body of the flame ... is composed of the smallest particles, very quickly and violently moving separately from one another." Further, he points out that "only this movement, depending on the various actions it produces, is called either heat or light." Turning to the rest of the bodies, he states that “that small particles that do not stop their movement are present not only in fire, but also in all other bodies, although in the latter their action is not so much strong, but due to their small size they themselves cannot be seen by any of our senses."
Atomism dominated the physical views of scientists and thinkers of the 17th century. Hooke, Huygens, Newton represented all the bodies of the Universe as consisting of the smallest particles, "insensitive", as Lomonosov briefly called them later. The concept of heat as a form of motion of these particles seemed quite reasonable to scientists. But these ideas about heat were of a qualitative nature and arose on a very meager factual basis. In the XVIII century. knowledge of thermal phenomena became more precise and definite; chemistry also made great strides, in which the theory of phlogiston, before the discovery of oxygen, helped to understand the processes of combustion and oxidation. All this contributed to the assimilation of a new point of view on heat as a special substance, and the first successes of calorimetry strengthened the position of supporters of caloric. Great scientific courage was needed to develop the kinetic theory of heat in this situation.
The kinetic theory of heat was naturally combined with the kinetic theory of matter, and above all of air and vapors. Gases (the word "gas" was introduced by Van Helmont; 1577-1644) in essence had not yet been discovered, and even Lavoisier considered steam as a combination of water and fire. Lomonosov himself, observing the dissolution of iron in strong vodka (nitric acid), considered
bubbles of nitrogen released by the air. Thus, air and steam were almost the only gases at the time of Lomonosov - "elastic liquids", according to the then terminology.
D. Bernoulli in his "Hydrodynamics" imagined air consisting of particles moving "extremely fast in different directions", and believed that these particles form an "elastic fluid". Bernoulli substantiated the Boyle-Mariotte law with his model of "elastic fluid". He established a connection between the speed of particles and the heating of air, and thereby explained the increase in the elasticity of air when heated. This was the first attempt in the history of physics to interpret the behavior of gases by the movement of molecules, an attempt undoubtedly brilliant, and Bernoulli went down in the history of physics as one of the founders of the kinetic theory of gases.
Six years after the publication of Hydrodynamics, Lomonosov presented his work Reflections on the Cause of Heat and Cold to the Academic Assembly. It was published only six years later, in 1750, together with another, later work, An Experience in the Theory of Air Elasticity. Thus, Lomonosov's theory of elasticity of gases is inextricably linked with his theory of heat and relies on the latter.
D. Bernoulli also paid great attention to the issues of heat, in particular the question of the dependence of air density on temperature. Without limiting himself to referring to the experiments of Amonton, he himself tried to experimentally determine the dependence of air elasticity on temperature. “I found,” writes Bernoulli, “that the elasticity of the air, which here in St. Petersburg was very cold on December 25, 1731, Art. Art., refers to the elasticity of the same air, which has heat in common with boiling water, as 523 to 1000. This value of Bernoulli's is obviously wrong, since it assumes that the temperature of the cold air corresponds to -78°C.
Lomonosov's analogous calculations mentioned above are much more accurate. On the other hand, the final result of Bernoulli is very remarkable, that “the elasticities are in a ratio composed of the square of the particle velocities and the first power of the densities”, which fully corresponds to the basic equation of the kinetic theory of gases in the modern presentation.
Bernoulli did not touch at all on the question of the nature of heat, which is central to Lomonosov's theory. Lomonosov hypothesizes that heat is a form of motion of insensitive particles. He considers the possible nature of these movements: translational, rotational and oscillatory - and states that "heat consists in the internal rotational motion of bound matter."
Taking as a starting point the hypothesis of the rotational motion of molecules as the cause of heat, Lomonosov deduces a number of consequences from this: 1) molecules (corpuscles) have a spherical shape; 2) “... with a faster rotation of particles of bound matter, heat should increase, and with a slower rotation, it should decrease; 3) particles of hot bodies rotate faster, colder ones - slower; 4) hot bodies must be cooled when they come into contact with a cold one, since it slows down the calorific movement of particles; on the contrary, cold bodies should heat up due to the acceleration of movement upon contact. Thus, the transition of heat from a hot body to a cold body observed in nature is a confirmation of Lomonosov's hypothesis.
The fact that Lomonosov singled out heat transfer as one of the main consequences is very significant, and some authors see this as a reason to rank Lomonosov among the discoverers of the second law of thermodynamics. It is unlikely, however, that the above proposition can be regarded as a primary formulation of the second law, but the whole work as a whole is undoubtedly the first outline of thermodynamics. Thus, Lomonosov explains in it the formation of heat during friction, which served as the experimental basis for the first law in Joule's classical experiments. Lomonosov further, referring to the question of the transfer of heat from a hot body to a cold one, refers to the following proposition: “Body A, acting on body B, cannot give the latter a greater speed of motion than what it itself has.” This provision is a specific case of the "universal conservation law". Proceeding from this proposition, he proves that a cold body B, immersed in a warm liquid A, "obviously cannot absorb a greater degree of heat than that which L has."
Lomonosov postpones the question of thermal expansion "until another time," until consideration of the elasticity of air. His thermodynamic work is thus directly related to his later work on the elasticity of gases. However, speaking of the intention to postpone the consideration of thermal expansion “until another time,” Lomonosov here also points out that since there is no upper limit on the speed of particles (the theory of relativity does not yet exist!), There is also no upper limit on temperature. But "by necessity there must be the greatest and last degree of coldness, which must consist in the complete cessation of the rotational motion of the particles." Lomonosov, therefore, asserts the existence of the "last degree of cold" - absolute zero.
In conclusion, Lomonosov criticizes the theory of caloric, which he considers a relapse of the idea of the ancients about elemental fire. Analyzing various phenomena, both physical and chemical, associated with the release and absorption of heat, Lomonosov concludes that “the heat of bodies cannot be attributed to the condensation of some thin, specially designed matter, but that heat consists in the internal rotational motion of the bound matter of the heated bodies." By "bound" matter, Lomonosov understands the matter of the particles of bodies, distinguishing it from "flowing" matter, which can flow "like a river" through the pores of the body.
At the same time, Lomonosov includes the world ether in his thermodynamic system, far ahead of not only his time, but also the 19th century. “Thus,” continues Lomonosov, “we not only say that such motion and heat are also characteristic of that finest matter of the ether, which fills all spaces that do not contain sensitive bodies, but we also affirm that the matter of the ether can communicate the calorific motion received from the sun our earth and the rest of the bodies of the world and heat them, being the medium by which bodies distant from each other communicate heat without the mediation of anything tangible.
So, long before Boltzmann, Golitsyn and Wien, Lomonosov included thermal radiation in thermodynamics. Lomonosov's thermodynamics is a remarkable achievement of the scientific thought of the 18th century, far ahead of its time.
The question arises: why did Lomonosov refuse to consider the translational motion of particles as a thermal motion, and stopped at the rotational motion? This assumption greatly weakened his work, and the theory of D. Bernoulli came much closer to the later studies of Clausius and Maxwell than the theory of Lomonosov. On this score, Lomonosov had very deep considerations. He had to explain such contradictory things as cohesion and elasticity, the cohesion of body particles and the ability of bodies to expand. Lomonosov was an ardent opponent of long-range forces and could not resort to them when considering the molecular structure of bodies. He also did not want to reduce the explanation of the elasticity of gases to elastic impacts of particles, i.e., to explain elasticity by elasticity. He was looking for a mechanism that would explain both elasticity and thermal expansion in the most natural way. In his work “Experience in the theory of air elasticity”, he rejects the hypothesis of the elasticity of the particles themselves, which, according to Lomonosov, “are devoid of any physical composition and organized structure ...” and are atoms. Therefore, the property of elasticity is exhibited not by single particles that do not have any physical complexity and organized structure, but are produced by a combination of them. So, the elasticity of a gas (air), according to Lomonosov, is a "property of the collective of atoms." The atoms themselves, according to Lomonosov, "should be solid and have extension", he considers their shape "very close" to spherical. The phenomenon of heat generated by friction makes him accept the hypothesis that "air atoms are rough". The fact that air elasticity is proportional to density leads Lomonosov to conclude "that it comes from some kind of direct interaction of its atoms." But atoms, according to Lomonosov, cannot act at a distance, but act only upon contact. The compressibility of air proves the presence of empty gaps in it, which make it impossible for atoms to interact. From here, Lomonosov comes to a dynamic picture, when the interaction of atoms is replaced in time by the formation of an empty space between them, and the spatial separation of atoms is replaced by contact. “So it is evident that the individual atoms of the air, in random alternation, collide with the nearest ones at insensible intervals of time, and when some are in contact, others rebound from each other and collide with those closest to them, in order to rebound again; thus, constantly repulsed from each other by frequent mutual shocks, they tend to scatter in all directions. Lomonosov sees elasticity in this scattering in all directions. "The force of elasticity consists in the desire of air to spread in all directions."
However, it is necessary to explain why atoms bounce off each other during interaction. The reason for this, according to Lomonosov, is thermal motion: "The interaction of air atoms is due only to heat." And since heat consists in the rotational motion of particles, to explain their repulsion it is enough to consider what happens when two rotating spherical rough particles come into contact. Lomonosov shows that they will push off from each other, and illustrate this with an example, well known to him from childhood, of the rebounding of the tops ("head over heels") that the boys let on the ice. When such spinning tops touch, they bounce off each other over considerable distances. Thus, elastic collisions of atoms, according to Lomonosov, are due to the interaction of their rotational moments. That's why he needed the hypothesis of thermal rotational motion of particles! Thus, Lomonosov fully substantiated the model of an elastic gas consisting of randomly moving and colliding particles.
This model allowed Lomonosov not only to explain the Boyle-Mariotte law, but also to predict deviations from it at high compressions. An explanation of the law and deviations from it is given by Lomonosov in the work "Addition to Reflections on the Elasticity of Air", published in the same volume of "New Commentaries" of the St. Petersburg Academy of Sciences, in which two previous works were also published. In the works of Lomonosov, there are also incorrect statements, which are fully explained by the level of knowledge of that time. But they do not determine the significance of the scientist's work. It is impossible not to admire the courage and depth of Lomonosov's scientific thought, who created in the infancy of the science of heat a powerful theoretical concept that was far ahead of its era. Contemporaries did not follow the path of Lomonosov, in the theory of heat, as was said, caloric reigned, the physical thinking of the 18th century required various substances: thermal, light, electrical, magnetic. This is usually seen as the metaphysical nature of the thinking of the naturalists of the 18th century, some of its reactionary nature. But why did it become like this? It seems that the reason for this lies in the progress of exact natural science. In the XVIII century. learned to measure heat, light, electricity, magnetism. Measures have been found for all these agents, just as they were found a long time ago for ordinary masses and volumes. This fact brought weightless agents closer to ordinary masses and liquids, forced us to consider them as analogues of ordinary liquids. The concept of "weightless" was a necessary stage in the development of physics, it allowed a deeper insight into the world of thermal, electrical and magnetic phenomena. It contributed to the development of an accurate experiment, the accumulation of numerous facts and their primary interpretation.
Long way thermometers
Temperature measuring instruments common today play important role in science, technology, in everyday life of people, have a long history and are associated with the names of many brilliant scientists from different countries, including Russian and those who worked in Russia.
A detailed description of the history of the creation of even an ordinary liquid thermometer can take up a whole book, including stories about specialists in various fields - physicists and chemists, philosophers and astronomers, mathematicians and mechanics, zoologists and botanists, climatologists and glassblowers.
The notes below do not pretend to complete the presentation of this very entertaining story, but may be useful for getting to know the field of knowledge and the field of technology, whose name is Thermometry.
Temperature
Temperature is one of the most important indicators that is used in various branches of natural science and technology. In physics and chemistry, it is used as one of the main characteristics of the equilibrium state of an isolated system, in meteorology - as the main characteristic of climate and weather, in biology and medicine - as the most important quantity that determines vital functions.
Even the ancient Greek philosopher Aristotle (384–322 BC) considered the concepts of heat and cold to be fundamental. Along with such qualities as dryness and humidity, these concepts characterized the four elements of "primary matter" - earth, water, air and fire. Although in those days and several centuries after they already talked about the degree of heat or cold (“warmer”, “hot”, “colder”), there were no quantitative measures.
Approximately 2500 years ago, the ancient Greek physician Hippocrates (c. 460 - c. 370 BC) realized that the elevated temperature of the human body is a sign of illness. There was a problem in determining the normal temperature.
One of the first attempts to introduce the concept of a standard temperature was made by the ancient Roman physician Galen (129 - c. 200), who suggested that the temperature of a mixture of equal volumes of boiling water and ice be considered “neutral”, and the temperatures of individual components (boiling water and melting ice) be considered four degrees, respectively. warm and four degrees cold. It is probably to Galen that we owe the introduction of the term temper(to equalize), from which the word "temperature" is derived. However, the temperature began to be measured much later.
Thermoscope and the first air thermometers
The history of temperature measurement has only a little more than four centuries. Based on the ability of air to expand when heated, which was described by the ancient Byzantine Greeks as early as the 2nd century BC. BC, several inventors created a thermoscope - the simplest device with a glass tube filled with water. It should be said that the Greeks (the first Europeans) got acquainted with glass as early as the 5th century, in the 13th century. the first glass Venetian mirrors appeared, by the 17th century. glasswork in Europe became quite developed, and in 1612 the first manual appeared "De arte vitraria"(“On the Art of Glassmaking”) by the Florentine Antonio Neri (died 1614).
Glassmaking was especially developed in Italy. Therefore, it is not surprising that the first glass instruments appeared there. The first description of the thermoscope was included in the book of the Neapolitan naturalist, engaged in ceramics, glass, artificial precious stones and distillation, Giovanni Battista de la Porta (1535–1615) Magia Naturalis("Natural Magic"). The edition was published in 1558.
In the 1590s the Italian physicist, mechanic, mathematician and astronomer Galileo Galilei (1564-1642), according to the testimony of his students Nelli and Viviani, built his glass thermobaroscope in Venice using a mixture of water and alcohol; measurements could be made with this instrument. Some sources say that Galileo used wine as a colored liquid. The working fluid was air, and temperature changes were determined by the volume of air in the device. The device was inaccurate, its readings depended on both temperature and pressure, but it allowed the column of liquid to be "dropped" by changing the air pressure. The description of this device was made in 1638 by Galileo's student Benadetto Castelli.
Close communication between Santorio and Galileo makes it impossible to determine the contribution of each to their many technical innovations. Santorio is known for his monograph "De statica medicine"(“On the Medicine of Balance”), containing the results of his experimental research and withstood five editions. In 1612 Santorio in his work "Commentaria in artem medicinalem Galeni"("Notes on the Medical Art of Galen") first described the air thermometer. He also used a thermometer to measure the temperature of the human body (“patients clamp the flask with their hands, breathe on it under cover, take it in their mouth”), used a pendulum to measure the pulse rate. His method consisted in fixing the rate of fall of the thermometer readings during ten swings of the pendulum, it depended on external conditions and was inaccurate.
Instruments similar to Galileo's thermoscope were made by the Dutch physicist, alchemist, mechanic, engraver and cartographer Cornelis Jacobson Drebbel (1572–1633) and the English mystic and medical philosopher Robert Fludd (1574–1637), who were supposedly familiar with the work of Florentine scientists. It was Drebbel's device that was first (in 1636) called a "thermometer". It looked like a U-shaped tube with two reservoirs. While working on the liquid for his thermometer, Drebbel discovered a way to make bright carmine colors. Fludd, in turn, described the air thermometer.
First liquid thermometers
The next small but important step towards the transformation of the thermoscope into a modern liquid thermometer was the use of a liquid and a glass tube sealed at one end as a working medium. The thermal expansion coefficients of liquids are less than those of gases, but the volume of a liquid does not change with a change in external pressure. This step was taken around 1654 in the workshops of the Grand Duke of Tuscany, Ferdinand II de' Medici (1610-1670).
Meanwhile, systematic meteorological measurements began in various European countries. Each scientist at that time used his own temperature scale, and the measurement results that have come down to us can neither be compared with each other nor connected with modern degrees. The concept of a temperature degree and reference points of the temperature scale apparently appeared in several countries as early as the 17th century. Masters applied 50 divisions by eye so that at the temperature of melting snow the alcohol column did not fall below the 10th division, and in the sun it did not rise above the 40th division.
One of the first attempts to calibrate and standardize thermometers was made in October 1663 in London. The members of the Royal Society agreed to use one of the alcohol thermometers made by the physicist, mechanic, architect and inventor Robert Hooke (1635–1703) as a standard and to compare the readings of other thermometers with it. Hooke introduced a red pigment into alcohol, the scale was divided into 500 parts. He also invented the minima thermometer (showing the lowest temperature).
The Dutch theoretical physicist, mathematician, astronomer and inventor Christian Huygens (1629–1695) in 1665 together with R. Hooke suggested using the temperatures of melting ice and boiling water to create a temperature scale. The first intelligible meteorological records were recorded using the Hooke–Huygens scale.
The first description of a real liquid thermometer appeared in 1667 in the publication of the Accademia del Cimento * "Essays on the natural scientific activities of the Academy of Experiments." The first experiments in the field of calorimetry were carried out and described at the Academy. It has been shown that under vacuum water boils at a lower temperature than at atmospheric pressure, and that when it freezes it expands. "Florence thermometers" were widely used in England (introduced by R. Boyle) and in France (distributed thanks to the astronomer I. Bullo). The author of the well-known Russian monograph "Concepts and Fundamentals of Thermodynamics" (1970) I.R. Krichevsky believes that it was the work of the Academy that laid the foundation for the use of liquid thermometers.
One of the members of the Academy, mathematician and physicist Carlo Renaldini (1615–1698) in his essay Philosophia naturalis("Natural Philosophy"), published in 1694, proposed to take the temperatures of melting ice and boiling water as reference points.
Born in the German city of Magdeburg, a mechanical engineer, electrical engineer, astronomer, inventor of the air pump Otto von Guericke (1602–1686), who became famous for his experience with the Magdeburg hemispheres, also dealt with thermometers. In 1672, he built a water-alcohol device several meters high with a scale that had eight divisions: from “very cold” to “very hot”. The dimensions of the structure, it must be admitted, did not advance thermometry.
Guericke's gigantomania found followers in the United States three centuries later. The world's largest thermometer, 40.8 m (134 ft) tall, was built in 1991 to commemorate the record high temperature reached in California's Death Valley in 1913: +56.7 °C (134 °F). A three-way thermometer is located in the small town of Baker near Nevada.
The first accurate thermometers that came into wide use were made by the German physicist Daniel Gabriel Fahrenheit (1686–1736). The inventor was born on the territory of present-day Poland, in Gdansk (then Danzig), orphaned early, began to study trading in Amsterdam, but did not finish his studies and, carried away by physics, began to visit laboratories and workshops in Germany, Holland and England. Since 1717 he lived in Holland, where he had a glass-blowing workshop and was engaged in the manufacture of precise meteorological instruments - barometers, altimeters, hygrometers and thermometers. In 1709 he made an alcohol thermometer, and in 1714 a mercury thermometer.
Mercury turned out to be a very convenient working fluid, since it had a more linear dependence of volume on temperature than alcohol, heated up much faster than alcohol, and could be used at much higher temperatures. Fahrenheit developed a new method for purifying mercury and used a cylinder instead of a ball for mercury. In addition, to improve the accuracy of thermometers, Fahrenheit, who owned glassblowing skills, began to use glass with the lowest coefficient of thermal expansion. Only in the area of low temperatures mercury (freezing point -38.86 °C) was inferior to alcohol (freezing point -114.15 °C).
Since 1718, Fahrenheit lectured in Amsterdam on chemistry, in 1724 he became a member of the Royal Society, although he did not receive a degree and published only one collection of research articles.
For his thermometers, Fahrenheit first used a modified scale adopted by the Danish physicist Olaf Römer (1644–1710) and proposed by the English mathematician, mechanic, astronomer, and physicist Isaac Newton (1643–1727) in 1701.
Newton's own initial attempts to develop a temperature scale proved naive and were abandoned almost immediately. It was proposed to take the air temperature in winter and the temperature of glowing coals as reference points. Then Newton used the melting point of snow and the body temperature of a healthy person, linseed oil as a working medium, and broke the scale (based on the model of 12 months a year and 12 hours a day until noon) by 12 degrees (according to other sources, by 32 degrees) . In this case, the calibration was carried out by mixing certain amounts of boiling and freshly thawed water. But this method was also unacceptable.
Newton was not the first to use oil: back in 1688, the French physicist Dalence used the melting point of cow butter as a reference point for calibrating alcohol thermometers. If this technique had been preserved, Russia and France would have had different temperature scales: both ghee common in Russia and the famous Vologda butter differ in composition from European varieties.
The observant Roemer noticed that his pendulum clocks run slower in summer than in winter, and the divisions of the scales of his astronomical instruments are larger in summer than in winter. To improve the accuracy of measurements of time and astronomical parameters, it was necessary to carry out these measurements at the same temperatures and, therefore, to have an accurate thermometer. Roemer, like Newton, used two reference points: the normal temperature of the human body and the melting temperature of ice (fortified red wine or a 40% alcohol solution tinted with saffron in an 18-inch tube served as the working fluid). Fahrenheit added a third point to them, which corresponded to the lowest temperature reached then in a mixture of water-ice-ammonia.
Having achieved significantly higher measurement accuracy with his mercury thermometer, Fahrenheit divided each degree of Roemer into four and took three points as reference points for his temperature scale: the temperature of the salt mixture of water with ice (0 ° F), the body temperature of a healthy person (96 ° F) and the melting temperature of ice (32 °F), the latter being considered the control.
Here is how he wrote about it in an article published in the magazine Philosophical Transaction"(1724,
vol. 33, p. 78): “... putting the thermometer in a mixture of ammonium salt or sea salt, water and ice, we find a point on the scale indicating zero. The second point is obtained if the same mixture without salt is used. Let's designate this point as 30. The third point, designated as 96, is obtained if the thermometer is taken into the mouth, receiving the warmth of a healthy person.
There is a legend that Fahrenheit took the temperature to which the air cooled in the winter of 1708/09 in his hometown of Danzig as the lowest point on the Fahrenheit scale. One can also find statements that he believed that a person dies from cold at 0 ° F and from heat stroke at
100°F. Finally, it was said that he was a member of the Freemason lodge with its 32 degrees of initiation, and therefore adopted the melting point of ice equal to this number.
After some trial and error, Fahrenheit came up with a very comfortable temperature scale. The boiling point of water turned out to be 212 °F on the accepted scale, and the entire temperature range of the liquid state of water was 180 °F. The rationale for this scale was the absence of negative degrees.
Subsequently, after a series of precise measurements, Fahrenheit found that the boiling point varies with atmospheric pressure. This allowed him to create a hypsothermometer - a device for measuring atmospheric pressure by the boiling point of water. He also belongs to the primacy in the discovery of the phenomenon of supercooling of liquids.
Fahrenheit's work marked the beginning of thermometry, and then thermochemistry and thermodynamics. The Fahrenheit scale has been adopted as official in many countries (in England since 1777), only the normal temperature of the human body was corrected to 98.6 o F. Now this scale is used only in the USA and Jamaica, other countries in 1960- 1970s and 1970s switched to the Celsius scale.
The thermometer was introduced into wide medical practice by the Dutch professor of medicine, botany and chemistry, the founder of a scientific clinic, Hermann Boerhaave (1668–1738), his student Gerard van Swieten (1700–1772), the Austrian physician Anton de Haen (1704–1776) and, regardless of them by the Englishman George Martin.
The founder of the Vienna School of Medicine, Haen, found that the temperature of a healthy person rises and falls twice during the day. Being a supporter of the theory of evolution, he explained this by the fact that the ancestors of man - reptiles that lived by the sea - changed their temperature in accordance with the ebb and flow. However, his work was forgotten for a long time.
Martin wrote in one of his books that his contemporaries argued whether the melting temperature of ice changes with height, and to establish the truth, they transported a thermometer from England to Italy.
It is no less surprising that scientists who became famous in various fields of knowledge later became interested in measuring the temperature of the human body: A. Lavoisier and P. Laplace, J. Dalton and G. Davy, D. Joule and P. Dulong, W. Thomson and A. Becquerel , J. Foucault and G. Helmholtz.
"A lot of mercury has leaked" since then. The almost three hundred year era of widespread use of mercury thermometers seems to be coming to an end soon due to the toxicity of liquid metal: in European countries, where people's safety is becoming more and more important, laws have been passed to restrict and prohibit the production of such thermometers.
* Founded in Florence in 1657 by students of Galileo under the auspices of Ferdinand II Medici and his brother Leopoldo, the Accademia del Cimento did not last long, but became the prototype of the Royal Society, the Paris Academy of Sciences and other European academies. She was conceived for propaganda scientific knowledge and expanding collective activities for their development.
Printed with a continuation
temperature scales. There are several graduated temperature scales and the freezing and boiling points of water are usually taken as reference points. Now the most common in the world is the Celsius scale. In 1742, the Swedish astronomer Anders Celsius proposed a 100-degree thermometer scale in which 0 degrees is the boiling point of water at normal atmospheric pressure, and 100 degrees is the melting temperature of ice. The division of the scale is 1/100 of this difference. When they began to use thermometers, it turned out to be more convenient to swap 0 and 100 degrees. Perhaps Carl Linnaeus took part in this (he taught medicine and natural science at the same Uppsala University where Celsius is astronomy), who back in 1838 proposed to take the melting point of ice as 0 temperature, but did not seem to think of the second reference point. To date, the Celsius scale has changed somewhat: 0 ° C is still taken as the melting temperature of ice at normal pressure, which does not really depend on pressure. But the boiling point of water at atmospheric pressure is now equal to 99 975 ° C, which does not affect the measurement accuracy of almost all thermometers except for special precision ones. The Fahrenheit temperature scales of Kelvin Reaumur and others are also known. The Fahrenheit temperature scale (in the second version adopted since 1714) has three fixed points: 0 ° corresponded to the temperature of the mixture of ice water and ammonia 96 ° - the body temperature of a healthy person (under the arm or in the mouth ). As a control temperature for the comparison of various thermometers, the value of 32 ° for the melting point of ice was taken. The Fahrenheit scale is widely used in English-speaking countries, but it is hardly used in the scientific literature. To convert Celsius temperature (°C) to Fahrenheit temperature (°F), there is a formula °F = (9/5)°C + 32 and for reverse conversion - the formula °C = (5/9) (°F-32 ). Both scales - both Fahrenheit and Celsius - are very inconvenient when conducting experiments in conditions where the temperature drops below the freezing point of water and is expressed as a negative number. For such cases, absolute temperature scales were introduced, which are based on extrapolation to the so-called absolute zero - the point at which molecular motion must stop. One of them is called the Rankin scale and the other is called the absolute thermodynamic scale; temperatures are measured in degrees Rankine (°Ra) and kelvins (K). Both scales start at absolute zero and the freezing point of water is 491 7° R and 273 16 K. The number of degrees and kelvins between the freezing and boiling points of water on the Celsius scale and the absolute thermodynamic scale is the same and equal to 100; for the Fahrenheit and Rankine scales, it is also the same but equal to 180. Celsius degrees are converted to kelvins using the formula K \u003d ° C + 273 16 and degrees Fahrenheit are converted to Rankine degrees using the formula ° R \u003d ° F + 459 7. in Europe has long been common Réaumur scale introduced in 1730 by René Antoine de Réaumur. It is not built arbitrarily like the Fahrenheit scale, but in accordance with the thermal expansion of alcohol (in the ratio 1000:1080). 1 degree Réaumur is equal to 1/80 of the temperature interval between the melting points of ice (0°R) and the boiling points of water (80°R), i.e. 1°R = 1.25°C 1°C = 0.8°R. but is now out of use.
