Purpose of the experiment: Determine the average density of the Earth Determine the constant of universal gravitation. The Experience of Henry Cavendish (1798) Reference Notes of Alexandria. In 1798, Henry Cavendish published data
Biography
Henry Cavendish was born on October 10, 1731 in Nice in the family of Lord Charles Cavendish, son of the second Duke of Devonshire, William Cavendish, and Lady Anne Gray, daughter of the first Duke of Kent, Henry Gray. Henry's younger brother Frederick suffered severe brain damage from an accidental fall at the age of twenty-one during his final year at Cambridge University. Evidence suggests that he was attempting to repeat Benjamin Franklin's famous experiment on the nature of lightning during an approaching thunderstorm, and fell from an upper window of the building. He required special care throughout his life. Lady Anne died, presumably of tuberculosis, shortly after Frederick was born, so neither boy knew their mother. The Cavendish family was closely associated with many of Britain's aristocratic families, with a history dating back some eight centuries to the Norman era.
Henry, along with his brother Frederick, received his early education at home. Initially, it was planned to continue the brothers’ education at Eton, a classical English school that provided good training for future statesmen. However, neither Henry nor his brother showed any inclination towards legal science, so their father decided to send them to a specialized scientific institution. He settled on Hackney Academy, many of whose teachers were closely acquainted with the leading minds of modern science. Henry and Frederick were the first members of the Cavendish family to graduate from Hackney Academy, but the school later became very popular among other aristocratic English families.
In 1749, at the age of eighteen, Henry entered Cambridge University and, continuing the family tradition, became the twenty-first member of the Cavendish family to enter this university. His brother Ferderic enters university two years later. Studying at the university, which absorbed the ideas of Isaac Newton, greatly influenced the brothers’ worldviews. Henry Cavendish left the university in 1753 without receiving a degree because he saw no need for an academic career. After leaving the university, he begins to conduct his own scientific research in the privacy of his home.
Scientific achievements
Pneumatic chemistry
Cavendish's published works relate mainly to the study of gases and date back to the period 1766-1788. We will focus on the main work of the scientist “Artificial air”. This work is of great scientific interest, telling about the composition and properties of water.
Cavendish's pneumatic research is remarkable for the number of discoveries it led to. Among the most significant of these is the first complete statement of the properties of hydrogen and carbon dioxide; demonstration of the constancy of the composition of atmospheric air and its first calculation of its composition with relatively high accuracy; records of famous experiments that led to the discovery of non-trivial properties of water and to the discovery of the composition of nitric acid.
Before Cavendish's seminal experiments, pneumatic chemistry hardly existed. In the works of a few scientists around the world, there were references to an “elastic liquid” that participates in certain chemical transformations. Paracelsus had some familiarity with hydrogen. Van Helmont, who introduced the concept of "gas", worked on the separation of carbon dioxide and some flammable gaseous compounds of carbon and sulfur, Boyle encountered carbonic acid and hydrogen in his experiments.
The listed scientists were closest to understanding gases as individual substances, but were too little familiar with their various properties by which these gases can be distinguished and recognized. The conviction that it is air, and not individual gases, that is released during the reaction process was characteristic of almost all chemists of the second half of the eighteenth century. The development of pneumatic chemistry could only occur on the basis of observing the differences between the artificial air obtained in different reactions, but chemists paid little attention to these differences, pointing only to the similarities and differences between the resulting gases and atmospheric air.
A striking example is the famous essays of Stephen Hayles, in which he writes about reactions in which "atmospheric air" or "elastic liquids" are released. According to modern ideas, in the course of his research he actually received oxygen, hydrogen, nitrogen, chlorine, carbon dioxide, sulfurous acid and other gases. Hales failed to notice differences in odor, color, solubility in water, or flammability of the resulting substances. He considered them identical to atmospheric air because they showed the same elasticity and, as it seemed to the scientist due to the inaccuracy of the equipment, they had the same weights. He considered their striking differences in reactivity to be the result of accidental mixing of “true air” with foreign impurities, and not as essential and distinctive properties of various “elastic liquids” or gases.
Hacourt, examining Boyle's experiments, noted some differences between the “elastic liquids” he obtained and atmospheric air. In the absence of other evidence, this theory was dismissed as false.
1754, however, marks the appearance of Black's first dissertation, which shows the existence of at least one "elastic liquid" which has permanent chemical properties different from those of atmospheric air. Since the results of his research were contrary to the prevailing opinion, he does not dare to give the isolated gas (hydrogen) a name and refers to an experimental error, planning to define it more precisely in the future.
What follows are attempts to determine the amounts of “bound air” in alkali metal carbonates. To do this, Cavendish measured the loss of mass of the solution when carbonates reacted with hydrochloric acid. He concluded that ammonium carbonate contains much more bound air than marble, since the reaction with hydrochloric acid is more violent.
Cavendish was able to accurately determine the composition of the Earth's atmosphere. After careful measurements, the scientist concluded that “ordinary air consists of one part air without phlogiston (oxygen) and four parts air with phlogiston (nitrogen).”
A 1785 paper describes an experiment in which Cavendish managed to remove oxygen and nitrogen from a sample of atmospheric air, but there was still a certain portion that the scientist could not remove using methods known to him. From this experiment, Cavendish concluded that no more than 1/120 of atmospheric air consists of gases other than oxygen and nitrogen. Despite the fact that argon was already known at that time, it took about a hundred years for Ramsay and Rayleigh to show that it was this gas that constituted the residual part of atmospheric air.
Gravitational constant
In addition to his achievements in the field of chemistry, Cavendish is also famous for his experiments, with the help of which he was able to measure the gravitational force and determine the exact value of the density of the Earth. Based on his results, it is possible to calculate the value for G = 6.754·10−11 m²/kg², which coincides well with the well-known value of 6.67428·10−11 m²/kg². For his experiment, Cavendish used equipment built and designed by geologist John Mitchell, who died before the experiment began. The equipment was sent to Cavendish, who completed the experiment in 1797 and published the results in 1798.
The experimental setup consisted of a torsion balance to measure the gravitational attraction between two 350-pound lead balls and a pair of 1.61-pound 2-inch balls. Using this equipment, Cavendish determined that the average density of the Earth was 5.48 times that of water. John Henry Poynting later noted that the data should have resulted in a value of 5.448, and indeed this number is the average of Cavendish's twenty-nine experiments described in his work.
Electricity Research
Cavendish was responsible for several papers on the study of electricity, written for the Royal Society, but most of his experiments were collected and published by James Maxwell only a century later in 1879, soon after other scientists had arrived at the same results. Cavendish's discoveries include:
- The concept of electrical potential, which he called "degree of electrification"
- Determination of the capacitance of the sphere and capacitor
- Material dielectric constant concept
- The relationship between electric potential and current, now called Ohm's law. (1781)
- Laws for current division in parallel circuits, which is currently associated with the name of Charles Wheatstone
- The inverse square law of change in electrical force with distance, now called Coulomb's law.
He experimentally established (1771) the influence of the environment on the capacitance of capacitors and determined (1771) the value of the dielectric constants of a number of substances. In 1798, he designed a torsion balance and used it to measure the force of attraction between two spheres, confirming the law of universal gravitation; determined the gravitational constant, mass and average density of the Earth. He was involved in determining the heat of phase transitions and the specific heat capacity of various substances. He invented the eudiometer, a device for analyzing gas mixtures containing flammable substances, and introduced desiccants into practice. Anticipated many 19th-century inventions in the field of electricity, but all his works remained in the family archives in Devonshire until James Maxwell published his selected works in 1879. The physics laboratory at the University of Cambridge, established in 1871, is named after Cavendish.
- Cavendish led a quiet and secluded life. He communicated with his maids exclusively through notes and did not establish personal relationships outside the family. According to one source, Cavendish often used the back door to get home to avoid meeting his housekeeper. Some modern doctors (such as Oliver Sacks) suggest that Cavendish suffered from Asperger's syndrome, although he may simply have been very shy. His social circle was limited only to the Royal Society club, whose members dined together before weekly meetings. Cavendish rarely missed these meetings and was deeply respected by his contemporaries.
- He also enjoyed collecting finely crafted furniture, and his documented purchase of “ten chairs and a satin-upholstered mahogany sofa.”
- Cavendish's favorite way to spend money was through charitable work. Once, having learned that a student who was helping him organize his library was in a difficult financial situation, Cavendish immediately wrote him a check for 10 thousand pounds - a huge amount at that time. He acted in this way all his life - and, nevertheless, he always had millions of pounds sterling at his disposal, as if he had a fabulous “irredeemable ruble.”
- Cavendish was completely indifferent to the world around him and was never interested in the events taking place in this world - even such significant ones as the French Revolution or the Napoleonic Wars that swept across Europe.
- Most of Cavendish's scientific works were not published until the second half of the 19th century, when James Maxwell began to analyze the Cavendish archives. And even now, several boxes filled with manuscripts and instruments, the purpose of which cannot be determined, remain undisassembled.
- One consequence of his gravitational measurements was a fairly accurate determination of density. However, this result was not known for almost 100 years, since Cavendish did not care about the publication of his work, nor about any recognition by the scientific world.
- In 1775, he invited seven eminent scientists to demonstrate an artificial electric stingray he had constructed, and gave each one an electric shock exactly identical to the way a real stingray paralyzes its victims. And at the end of the show, he, ahead of his contemporaries Galvani and Volta, solemnly announced to those invited that it was this new force he had demonstrated that would one day revolutionize the whole world.
- Although it is widely believed that the world famous Cavendish Laboratory is named after Henry Cavendish, this is not true. It is named after Henry's relative, William Cavendish, 7th Duke of Devonshire. He was Chancellor of the University of Cambridge and donated a large sum to the opening of the world's first teaching and research laboratory at the university.
- About 11 years before Coulomb, the law of interaction of charges was discovered by G. Cavendish, but the result was not published and remained unknown for a long time.
- He died unmarried on February 24, 1810, leaving an estate of £700,000 and a further 6,000 annual income from the estate. Unfortunately, not a single pound of this wealth was donated to science. The scientist’s will contained a categorical requirement that the crypt with his coffin be tightly walled up immediately after the funeral, and there were no inscriptions outside indicating who was buried in this crypt. And so it was done. Cavendish was buried in Derby Cathedral. Neither an examination of the body nor an autopsy was performed. And not a single reliable portrait of Cavendish has survived either.
Date of Birth: 10.10.1731
Citizenship: Great Britain
Biography
English physicist and chemist, member of the Royal Society of London (since 1760). Born in Nice (France). Graduated from Cambridge University (1753). Conducted scientific research in his own laboratory.
Works in the field of chemistry relate to pneumatic (gas) chemistry, of which he is one of the creators. Isolated (1766) carbon dioxide and hydrogen in their pure form, mistaking the latter for phlogiston, and established the basic composition of air as a mixture of nitrogen and oxygen. Received nitrogen oxides. By burning hydrogen he obtained water (1784), determining the ratio of the volumes of gases interacting in this reaction (100:202). The accuracy of his research was so great that it allowed him, when obtaining (1785) nitrogen oxides by passing an electric spark through humidified air, to observe the presence of “dephlogisticated air,” constituting no more than 1/20 of the total volume of gases. This observation helped W. Ramsay and J. Rayleigh discover (1894) the noble gas argon. He explained his discoveries from the perspective of the phlogiston theory.
In the field of physics, in many cases he anticipated later discoveries. The law according to which the forces of electrical interaction are inversely proportional to the square of the distance between charges was discovered by him (1767) ten years earlier than the French physicist C. Coulomb.
He experimentally established (1771) the influence of the environment on the capacitance of capacitors and determined (1771) the value of the dielectric constants of a number of substances. He determined (1798) the forces of mutual attraction between bodies under the influence of gravity and at the same time calculated the average density of the Earth. Cavendish's work in the field of physics became known only in 1879 - after the English physicist J. Maxwell published his manuscripts, which had been in the archives until that time.
The physics laboratory at the University of Cambridge, established in 1871, is named after Cavendish.
Based on materials from the biographical reference book "Outstanding Chemists of the World" (authors V.A. Volkov and others) - Moscow, "Higher School", 1991.
Touches to the portrait
Born in Nice on October 10, 1731, Henry Cavendish came from a famous Anglo-Norman family. Having lived poorly in his youth and had a rather modest income, after his death he left enormous wealth. It is known that his condition did not arise as a result of any financial transactions. A letter survives from the bank where Cavendish kept a very small part of his money. In this letter, the bank invited him to place the rest of his fortune there, promising the most favorable conditions. Sir Henry's answer was unequivocal: “Take care of the money that I deposited in your bank, and stay away from the rest. If you don’t know what to do with it, I will gladly take it. And if you bother me one more time, I will immediately I'll do it."
Cavendish's favorite way to spend money was through charity work. Once, having learned that a student who was helping him organize his library was in a difficult financial situation, Cavendish immediately wrote him a check for 10 thousand pounds - a huge amount at that time. He acted in this way all his life - and, nevertheless, he always had millions of pounds sterling at his disposal, as if he had a fabulous “irredeemable ruble.” Some believe that this inexhaustible wealth was brought to him by his successful studies in alchemy, but this, of course, is only an assumption.
In February 1753, Cavendish graduated from the prestigious Cambridge University. But, being one of the most outstanding scientists of the 18th century, he never received any academic degree. One possible explanation: in those days, any Cambridge graduate could not be an unbeliever, and Cavendish's atheism was well known. But the reason could be different.
It is difficult, however, to explain another unusual fact: Cavendish, who, as already mentioned, did not have any academic degree and had not published a single scientific work, was admitted to the Royal Academy of Sciences at the age of 29.
In 1773, 20 years after graduating from Cambridge, Cavendish, already fabulously wealthy, settled in Clapham Common, on the street that today bears his name. It was from then on that the scientist began to behave strangely towards those around him: he could not stand it when anyone addressed him, and even if some stranger spoke to him on the street, Cavendish silently turned away and called a cab and immediately returned home.
He generally considered women to be some kind of people with whom he did not want to have anything in common. He ordered an external staircase to be added to the house and ordered the servants to use only it. Those of them who dared to use the internal ones, he immediately fired.
They tell the following story. One day Cavendish dined at the Royal Scientific Society club. At this time, a young beautiful woman appeared in the window of the house opposite and began to examine the passing carriages. Many of the men present in the club came to the window to get a better look at her. Deciding for some reason that they were admiring the full moon, Cavendish was about to join them, but realizing his mistake, he immediately left the club, out loud expressing his disgust at what was happening.
But one day, without hesitation, he rushed to the woman’s defense. Once, while in Clapham, Cavendish saw a woman in a meadow trying to escape from an angry bull. He instantly rushed to the rescue, rushed between the woman and the animal and managed to drive it away. Then, without expecting gratitude, he turned and silently left.
He communicated with the manager of his house only by correspondence. So, for example, in one of his memorandums he writes: “I have invited several gentlemen to dinner and would like each of them to be served a ham of mutton. And since I do not know how many hams a ram has, I will ask you to figure it out yourself question."
It was completely impossible to talk to him, since he simply turned his back to whoever was trying to do it and left. According to rumors, he still had several friends, but no information about them is available.
For 30 years, Cavendish led a life the details of which are still largely unknown to this day. He wore a purple, completely faded suit, a 17th-century style wig, and always hid his face. He traveled to the village in a carriage equipped with a meter of his own design, reminiscent of modern taximeters.
One fine day he called a servant and announced: “Listen carefully to what I tell you. I intend to die soon. When this happens, go to Lord George Cavendish and tell him what happened.” The servant muttered that it wouldn’t be a bad idea in that case to confess and take communion. “I have no idea what it is,” Cavendish answered. “You’d better get some lavender water and don’t appear here again until I die.”
When the heirs got acquainted with the documents left by Cavendish, it turned out that the deceased owned a huge number of shares in the Bank of England - very good for a man who had not earned a penny in his life, but at the same time was constantly generously wasting money.
The scientist’s will contained a categorical requirement that the crypt with his coffin be tightly walled up immediately after the funeral, and there were no inscriptions outside indicating who was buried in this crypt. And so it was done. Cavendish was buried on 12 March 1810 in Derby Cathedral. Neither an examination of the body nor an autopsy was performed. And not a single reliable portrait of Cavendish has survived either.
Most of Cavendish's scientific work was not published until 1921, and even now several boxes filled with manuscripts and instruments whose purpose cannot be determined remain undisassembled. And what little is known looks very unusual. Cavendish conducted scientific experiments that were centuries ahead of his time. For example, he calculated the deviations of light rays due to the mass of the Sun 200 years before Einstein, and his calculations almost coincide with Einstein’s. He accurately calculated the mass of our planet and was able to separate light gases from the atmospheric air. At the same time, he did not care at all about the publication of his works, or about any recognition by the scientific world.
In 1775, he invited seven eminent scientists to demonstrate the artificial electric stingray he had constructed, and gave each of them an electric shock exactly identical to the way a real stingray paralyzes its victims. And at the end of the show, he, ahead of his contemporaries Galvani and Volta, solemnly announced to the guests that it was this new force he had demonstrated that would one day revolutionize the whole world.
Cavendish could determine current voltage by touching an electrical circuit with his hand, which indicates his extraordinary physical qualities. Despite the very modest capabilities of his laboratory from the point of view of modern science, he was able to very accurately calculate the mass of the Earth. And Cavendish made all these extraordinary, outstanding discoveries, relying not even on the science of his time, but using the achievements of medieval alchemy, the language and symbols of which he mastered.
Cavendish was completely indifferent to the world around him and was never interested in the events taking place in this world - even such significant ones as the French Revolution or the Napoleonic Wars that swept across Europe.
However, it is hardly legitimate to explain his actions as ordinary eccentricities. And handing out money left and right, he was not a philanthropist at all. And his hostility towards women also defies explanation. One of Cavendish's contemporaries, a scientist named Lovecraft, put it this way: “His appearance is just a mask. The creature hiding under it is not human.” However, Cavendish was by no means an exception among the outstanding figures of the 18th century - a whole galaxy of brilliant scientists worked, whose discoveries were ahead of their time. So, for example, Roger Boscovich published a treatise in 1736 in which one can find references not only to the theory of relativity, but also to such areas of knowledge about which science knows almost nothing to this day - for example, about time travel or antigravity .
Among the outstanding scientists who were clearly ahead of their time, Cavendish is not alone. His contemporaries Saint-Germain, Boscovich, Benjamin Franklin, Joseph Priestley and Count Rumfoord are also in this row. It is known that these people knew each other and were in correspondence. Let us remember what Benjamin Franklin wrote to Joseph Priestley (and this was the end of the 18th century): “It becomes simply uneasy when you imagine what powers man will have in a thousand years. He will learn to deprive large masses of matter of the force of gravity, which will give them absolute lightness and will allow them to be moved without the slightest effort. In agriculture, labor costs will be much reduced, and yields will increase. All our diseases, including aging, will be defeated. And human life can be extended unlimitedly, even beyond the limits that are known to us from Bible."
Between 1750 and 1800 many discoveries were made that the science of that time was simply unable to exploit. For example, the English mathematician Cayley said that he believed that an engine powerful enough to lift an object heavier than air would soon be invented. Based on this assumption, he already developed a design for an airplane in 1800. Around the same period, the concept of an artificial satellite appeared, which, launched from a giant cannon, would circle around our planet...
Plan:
- Introduction
- 1 Biography
- 2
Scientific achievements
- 2.1 Pneumatic chemistry
- 2.2 "Artificial air"
- 2.3 Electricity Research
- 3 Interesting Facts Notes
Introduction
Henry Cavendish(English) Henry Cavendish; 10 October 1731 - 24 February 1810) - British physicist and chemist, member of the Royal Society of London (since 1760).
1. Biography
Henry Cavendish was born on October 10, 1731 in Nice in the family of Lord Charles Cavendish, son of the second Duke of Devonshire, William Cavendish, and Lady Anne Gray, daughter of the first Duke of Kent, Henry Gray. Henry's younger brother Frederick suffered severe brain damage in an accidental fall at the age of twenty-one during his final year at Cambridge University. Evidence suggests that he was attempting to repeat Benjamin Franklin's famous experiment on the nature of lightning during an approaching thunderstorm, and fell from the top window of the building. He required special care throughout his life. Lady Anne died, presumably of tuberculosis, shortly after Frederick was born, so neither boy knew their mother. The Cavendish family was closely associated with many of Britain's aristocratic families, with a history dating back some eight centuries to the Norman era.
Henry, along with his brother Frederick, received his early education at home. Initially, it was planned to continue the brothers’ education at Eton, a classical English school that provided good training for future statesmen. However, neither Henry nor his brother showed any inclination towards legal science, so their father decided to send them to a specialized scientific institution. He settled on Hackney Academy, many of whose teachers were closely acquainted with the leading minds of modern science. Henry and Frederick were the first members of the Cavendish family to graduate from Hackney Academy, but the school later became very popular among other aristocratic English families.
In 1749, at the age of eighteen, Henry entered Cambridge University and, continuing the family tradition, became the twenty-first member of the Cavendish family to enter this university. His brother Ferderic enters university two years later. Studying at the university, which absorbed the ideas of Isaac Newton, greatly influenced the brothers’ worldviews. Henry Cavendish left the university in 1753 without receiving a degree because he saw no need for an academic career. After leaving the university, he begins to conduct his own scientific research in the privacy of his home.
2. Scientific achievements
2.1. Pneumatic chemistry
Cavendish's published works relate mainly to the study of gases and date back to the period 1766-1788. We will focus on the main work of the scientist “Artificial Air”. This work is of great scientific interest, as well as the composition and properties of water.
Cavendish's pneumatic research is remarkable for the number of discoveries it led to. Among the most significant of these is the first complete statement of the properties of hydrogen and carbon dioxide; demonstration of the constancy of the composition of atmospheric air and its first calculation of its composition with relatively high accuracy; records of famous experiments that led to the discovery of non-trivial properties of water and to the discovery of the composition of nitric acid.
Before Cavendish's seminal experiments, pneumatic chemistry hardly existed. In the works of a few scientists around the world, there were references to an “elastic liquid” that participates in certain chemical transformations. Paracelsus had some acquaintance with hydrogen. Van Helmont, who introduced the concept of "gas", worked on the separation of carbon dioxide and some flammable gaseous compounds of carbon and sulfur; Boyle encountered carbonic acid and hydrogen in his experiments.
The listed scientists were closest to understanding gases as individual substances, but were too little familiar with their various properties by which these gases can be distinguished and recognized. The conviction that it was air, and not individual gases, that was released during the reaction process was characteristic of almost all chemists of the second half of the eighteenth century. The development of pneumatic chemistry could only occur on the basis of observing the differences between the artificial air obtained in different reactions, but chemists paid little attention to these differences, pointing only to the similarities and differences between the resulting gases and atmospheric air.
A striking example is the famous essays of Stephen Hayles, in which he writes about reactions in which “atmospheric air” or “elastic liquids” are released. According to modern ideas, in the course of his research he actually received oxygen, hydrogen, nitrogen, chlorine, carbon dioxide, sulfurous acid and other gases. Hales failed to notice differences in odor, color, solubility in water, or flammability of the resulting substances. He considered them to be identical to atmospheric air because they showed the same elasticity and, as it seemed to the scientist due to the inaccuracy of the equipment, they had the same weights. He considered their striking differences in reactivity to be the result of accidental mixing of “true air” with foreign impurities, and not as essential and distinctive properties of various “elastic liquids” or gases.
Hacourt, examining Boyle's experiments, noted some differences between the “elastic liquids” he obtained and atmospheric air. In the absence of other evidence, this theory was dismissed as false.
1754, however, marks the appearance of Black's first dissertation, which shows the existence of at least one "elastic liquid" that has permanent chemical properties different from those of atmospheric air. Since the results of his research were contrary to the prevailing opinion, he does not dare to give the isolated gas (hydrogen) a name and refers to an experimental error, planning to define it more precisely in the future.
However, Black takes a big step forward from his predecessors. In later works he describes the properties of a solution of carbonic acid; twelve years later, Cavendish shows that it has exactly the same chemical properties in the free state.
2.2. "Artificial air"
His first report on gases, entitled "Artificial Air", was published in 1766. It begins by defining artificial air as "any kind of air which is contained in other organs in an 'inelastic' state, and can be obtained from there." This is followed by references to Black's work, in which he states his intention to use the term "fixed air" to refer to the gas contained in the carbonates of the alkali and alkaline earth elements. Cavendish also calls this gas “non-flammable”, contrasting it with the gas that is released during the decay of living organisms and the interaction of metals with acids. The terms “flammable” and “non-flammable” gas subsequently found wide use.
Cavendish divides his message into three parts: the first relates to hydrogen, the second to carbon dioxide, and the third to gases released during fermentation and putrefaction. Cavendish's main observations included the following: zinc, iron and tin were the only metals that released “flammable air” when reacting with dilute solutions of sulfuric and hydrochloric acids. Zinc dissolved in both acids at a faster rate than iron and tin, but the same amount of gas was released regardless of the acid used. Iron gave the same amount of “flammable gas” in solutions of sulfuric acid of different strengths. Tin dissolved best in warm hydrochloric acid. An ounce of zinc produced about 356, an ounce of iron 412, and an ounce of tin 202 ounces of "combustible gas."
All these metals dissolved readily in nitrous oxide (nitric acid) and produced "non-flammable air" (nitrogen oxides), as well as in hot oil of vitriol (concentrated sulfuric acid), also producing "non-flammable air" with a strong unpleasant odor.
From these observations, Cavendish concluded that when metals are dissolved in dilute sulfuric or hydrochloric acid, "their phlogiston flies away, without changing its nature with the change of acid and forming 'combustible air,' but when the metals react with concentrated sulfuric or nitric acid , their phlogiston loses its flammability.”
In his work, Cavendish pointed out the following properties of the “combustible gas” (hydrogen): it does not lose its elasticity, does not show noticeable dissolution in water and does not interact with alkalis. Cavendish also investigated the effect of the composition of the mixture of oxygen and hydrogen on explosiveness. A mixture of one part “combustible air” and nine parts “ordinary” burned exclusively within the confines of the vessel in question. A mixture of 8 parts “combustible air” and 2 parts “normal” ignited without explosion. When the amount of hydrogen approximately doubled, combustion occurred explosively. From these experiments, Cavendish tried to establish the proportion between hydrogen and atmospheric air necessary for complete combustion of the mixture, but he made the mistake of calculating that two volumes of hydrogen required 7 volumes of air, while 5 volumes of the latter would be sufficient.
Cavendish also tried to establish the mass of the "flammable gas" of hydrogen. He concluded that flammable air escapes 8,760 times lighter than water, or 11 times lighter than “ordinary air.” Hydrogen, however, is actually 14.4 times lighter than air.
Cavendish completes the first part of his work with a study of the interaction of copper with hydrochloric acid and attempts to obtain a “combustible gas” in this way. The scientist comes to the conclusion that the gas released in the reaction (gaseous hydrochloric acid) does not ignite when mixed with atmospheric air, and also loses elasticity when interacting with water (due to dissolution), which means that it is not possible to obtain a “flammable gas” in this way seems possible. Cavendish did not study gaseous hydrochloric acid.
The second part of Cavendish's work is entitled "Experiments on Bound Air, or Artificial Air Obtained from Alkaline Substances by Reaction with Acids or Calcination."
In describing this part of the work, Cavendish relies on the results obtained by Black regarding the effect of carbonic acid on the hardness of carbonates. Cavendish obtained carbon dioxide by dissolving marble in hydrochloric acid. He discovered that the released gas is soluble in water, quickly interacts with alkalis, but can persist for up to one year under a layer of mercury without losing its elasticity and chemical properties. To determine the solubility of carbon dioxide in water, Cavendish used an apparatus, the discovery of which is often attributed to Priestley. Cavendish released known volumes of the gas and water under study into a graduated vessel filled with mercury; Thus, he established that “at a temperature of 55°, water absorbs much more of the gas under study than ordinary air.” In the course of his experiments, he found, however, that water does not always absorb the same volume of gas bound in marble. The scientist explained this fact by the fact that this gas contains substances that have different solubility in water. The scientist also found that cold water dissolves much more of this gas than hot water; to explain this fact, he gave the example of boiling water, which not only is not able to absorb any gas, but is also deprived of what it has already absorbed.
The density of carbonic acid was determined in the same way as in the case of hydrogen; it turned out to be equal to 1.57 the density of atmospheric air. This definition closely reproduces the currently known value of 1.529. The inaccuracy of the determination is due to the presence of an admixture of gaseous hydrochloric acid, as well as to imperfect equipment. A series of experiments were carried out on the effect of carbon dioxide on the combustion process; Cavendish used a simple setup containing a glass jar and a wax candle. If there was only atmospheric air in the jar, the candle burned for 80 seconds. When the jar contained one part of “bound air” (carbon dioxide) and 19 parts of atmospheric air, the candle burned for 51 seconds, with a ratio of 1 to 9 - only 11 seconds. Thus, adding even small amounts of carbon dioxide to atmospheric air deprives the latter of its ability to support combustion.
What follows are attempts to determine the amounts of “bound air” in alkali metal carbonates. To do this, Cavendish measured the loss of mass of the solution during the interaction of carbonates with hydrochloric acid. He concluded that ammonium carbonate contains much more bound air than marble, since the reaction with hydrochloric acid is more violent.
The third part of Cavendish's work is devoted to "Air formed in the processes of fermentation and putrefaction." McBride, following Black's suggestion, showed that these processes produce exclusively carbon dioxide. Cavendish confirmed this result with experiments on the fermentation of sweet wine and apple juice. Indeed, the gas released in these processes was completely absorbed by the potassium carbonate, and also had the same water solubility, flame action and specific gravity as the “air” released from the marble.
Cavendish obtained the gases released during the decay process by decomposing the broth at a temperature close to the boiling point of water. The experiment was carried out until gas ceased to be released. The resulting gas was passed through a solution of potassium carbonate, while carbon dioxide was absorbed and what remained was a mixture of “ordinary air” and some “flammable air” in a ratio of 1 to 4.7. Next, Cavendish determined the specific gravity of the resulting mixture and compared it with the specific gravity of 1 part of atmospheric air and 4.7 parts of hydrogen; the share of the latter turned out to be less. The scientist concluded that the new “flammable gas” obtained has almost the same nature as that obtained by the interaction of metals with acids.
Cavendish was able to accurately determine the composition of the Earth's atmosphere. After careful measurements, the scientist concluded that “ordinary air consists of one part air without phlogiston (oxygen) and four parts air with phlogiston (nitrogen).”
A 1785 paper describes an experiment in which Cavendish managed to remove oxygen and nitrogen from a sample of atmospheric air, but there was still a certain portion that the scientist could not remove using methods known to him. From this experiment, Cavendish concluded that no more than 1/120 of atmospheric air consists of gases other than oxygen and nitrogen. Despite the fact that argon was already known at that time, it took about a hundred years for Ramsay and Rayleigh to show that it was this gas that constituted the residual part of atmospheric air.
2.3. Electricity Research
In addition to his achievements in the field of chemistry, Cavendish is also famous for his experiments, with the help of which he was able to measure the gravitational force and determine the exact value of the density of the Earth. Based on his results, it is possible to calculate the value for G = 6.754×10 −11 m²/kg², which coincides well with the well-known value of 6.67428×10 −11 m²/kg². For his experiment, Cavendish used equipment built and designed by geologist John Mitchell, who died before the experiment began. The equipment was sent to Cavendish, who completed the experiment in 1797 and published the results in 1798.
The experimental setup consisted of a torsion balance to measure the gravitational attraction between two 350-pound lead balls and a pair of 1.61-pound 2-inch balls. Using this equipment, Cavendish determined that the average density of the Earth was 5.48 times that of water. John Henry Poynting later noted that the data should have resulted in a value of 5.448, and indeed this number is the average of Cavendish's twenty-nine experiments described in his work.
Cavendish wrote several papers on the properties of electricity for the Royal Society, but most of his experiments were collected and published by James Maxwell only a century later in 1879, shortly after other scientists had arrived at the same results. Cavendish's discoveries include:
- The concept of electrical potential, which he called the “degree of electrification”
- Determination of the capacitance of the sphere and capacitor
- Material dielectric constant concept
- The relationship between electric potential and current, now called Ohm's law. (1781)
- Laws for current division in parallel circuits, which is currently associated with the name of Charles Wheatstone
- The inverse square law of the change in electrical force with distance, now called Coulomb's law.
He experimentally established (1771) the influence of the environment on the capacitance of capacitors and determined (1771) the value of the dielectric constants of a number of substances. In 1798 he designed a torsion balance and used it to measure the force of attraction between two spheres, confirming the law of universal gravitation; determined the gravitational constant, mass and average density of the Earth. He was involved in determining the heat of phase transitions and the specific heat capacity of various substances. He invented the eudiometer, a device for analyzing gas mixtures containing flammable substances, and introduced desiccants into practice. Anticipated many of the 19th century's inventions in the field of electricity, but all his works remained in the family archives in Dervonshire until James Maxwell published his selected works in 1879. The physics laboratory at the University of Cambridge, established in 1871, is named after Cavendish.
Many sources mistakenly describe Cavendish's work as measuring the gravitational constant (G) or the mass of the Earth, and this mistake has been pointed out by several authors. . In reality, Cavendish's main goal was to determine the density of the Earth. This result served as the basis for calculating the constant G, which was first used in 1873, almost 100 years after the Cavendish experiment. The results of the Cavendish experiment can also be used to calculate the mass of the Earth.
3. Interesting facts
Cavendish led a quiet and secluded life. He communicated with his maids exclusively through notes and did not establish personal relationships outside the family. According to one source, Cavendish often used the back door to get home to avoid meeting his housekeeper. Some modern doctors (such as Oliver Sacks) suggest that Cavendish suffered from Asperger's syndrome, although he may simply have been very shy. His social circle was limited to the Royal Society club, whose members dined together before their weekly meetings. Cavendish rarely missed these meetings and was deeply respected by his contemporaries.
He also enjoyed collecting finely crafted furniture, and his documented purchase of “ten chairs and a satin-upholstered mahogany sofa.”
Cavendish's favorite way to spend money was through charity work. Once, having learned that a student who was helping him organize his library was in a difficult financial situation, Cavendish immediately wrote him a check for 10 thousand pounds - a huge amount at that time. He acted in this way all his life - and, nevertheless, he always had millions of pounds sterling at his disposal, as if he had a fabulous “irredeemable ruble.”
Cavendish was completely indifferent to the world around him and was never interested in the events taking place in this world - even such significant ones as the French Revolution or the Napoleonic Wars that swept across Europe.
Most of Cavendish's scientific works were not published until the second half of the 19th century, when James Maxwell began to analyze the Cavendish archives. And even now, several boxes filled with manuscripts and instruments, the purpose of which cannot be determined, remain undisassembled. And what little is known looks very unusual. Cavendish conducted scientific experiments that were centuries ahead of his time. For example, he calculated the deviations of light rays due to the mass of the Sun, 200 years before Albert Einstein, and his calculations almost coincide with Einstein’s [ source not specified 31 days] .
One of the consequences of his gravitational measurements was a fairly accurate determination of density. However, this result was not known for almost 100 years, since Cavendish did not care about the publication of his work, nor about any recognition by the scientific world.
In 1775, he invited seven eminent scientists to demonstrate the artificial electric stingray he had constructed, and gave each of them an electric shock exactly identical to the way a real stingray paralyzes its victims. And at the end of the show, he, ahead of his contemporaries Galvani and Volta, solemnly announced to the guests that it was this new force he had demonstrated that would one day revolutionize the whole world.
(Cavendish, Henry) (1731-1810), English physicist and chemist. Born October 10, 1731 in Nice. Son of Lord Charles Cavendish, who was related to the Duke of Devonshire and the Duke of Kent. Four years of study at Cambridge University (1749-1753) instilled in Cavendish a love of the natural sciences. Having inherited a large fortune, he spent almost all of his income on experimental work. He set up a laboratory in his house in London, where he collected the best instruments and instruments of that time. In 1766, Cavendish published the first important work in chemistry, Factitious Air, which reported the discovery of “combustible air” (hydrogen). In 1784 and 1785, two other of his works were published in the Transactions of the Royal Society. The first of them described experiments on burning a gas mixture of 5 parts ordinary air and 2 parts hydrogen to form water, which indicated the complex nature of this substance. The second work showed that when an electrical discharge is passed through air above the surface of water, nitrogen reacts with oxygen to form nitric acid. At the same time, Cavendish drew attention to the fact that 1/120 of the original volume of air does not react. Due to the imperfection of analytical methods and instruments, Cavendish was unable to detect new elements in the unreacted gas residue. They were discovered more than a hundred years later by W. Ramsay and called noble (inert) gases. In 1796-1798, Cavendish was engaged in determining the heat of phase transitions and specific heat capacities of various substances. He invented the eudiometer, a device for analyzing gas mixtures containing flammable substances, and introduced desiccants into practice. Cavendish anticipated many inventions of the 19th century. in the field of electricity, but all his works remained in the family archive in Devonshire until in 1879 J. Maxwell prepared his selected works for publication. Cavendish introduced the concept of electric potential and studied the dependence of the capacitance of a capacitor on the medium. In 1798 he designed a torsion balance and used it to measure the force of attraction between two spheres, thereby confirming the law of universal gravitation; determined the gravitational constant, mass and average density of the Earth. Being an adherent of the phlogiston theory, he nevertheless did not dispute the views of his contemporary A. Lavoisier, admitting that Lavoisier’s theory has the same right to exist. Among his published works are Electrical Phenomena (Phenomena of Electricity, 1771); Discovery of the Composition of Water, 1784; Discovery of the Composition of Nitric Acid, 1785; Freezing Point of Mercury, 1783; Experiments to Determine the Density of the Earth, 1798; An Improved Method for Graduating Astronomical Instruments, 1809. In 1851, D. Wilson published the Life of Honorable Henry C. Cavendish, and in 1921 the Royal Society published a two-volume history of his scientific work. In some areas, Cavendish was significantly ahead of contemporary science, but for a long time he remained almost unknown in scientific circles. He was a lone scientist, and besides, he considered it possible to publish only those articles in the reliability of which he was completely confident. Cavendish rarely spoke and did not always inform the Royal Society, of which he had been a member since 1760, about his discoveries. Cavendish died in London on March 10, 1810. The physics laboratory at the University of Cambridge, established in 1871, is named after Cavendish.
Henry Cavendish(English Henry Cavendish; October 10, 1731 - February 24, 1810) - English physicist and chemist, member of the Royal Society of London (since 1760).
Born October 10, 1731 in Nice. Graduated from Cambridge University in 1753. Having inherited a large fortune, he spent almost all his income on conducting experiments.
In 1766, Cavendish published the first important work in chemistry, Artificial Air, which reported the discovery of “combustible air” (hydrogen). He isolated carbon dioxide and hydrogen in their pure form, mistaking the latter for phlogiston, and established the basic composition of air as a mixture of nitrogen and oxygen. Received nitrogen oxides. By burning hydrogen he obtained water (1784), determining the ratio of the volumes of gases interacting in this reaction (100:202).
He experimentally established (1771) the influence of the environment on the capacitance of capacitors and determined (1771) the value of the dielectric constants of a number of substances. In 1798 he designed a torsion balance and used it to measure the force of attraction between two spheres, confirming the law of universal gravitation; determined the gravitational constant, mass and average density of the Earth. He was involved in determining the heat of phase transitions and the specific heat capacity of various substances. He invented the eudiometer, a device for analyzing gas mixtures containing flammable substances, and introduced desiccants into practice. He anticipated many of the 19th century's inventions in the field of electricity, but all his works remained in the family archives in Devonshire until James Maxwell published his selected works in 1879.
Cavendish died in London on February 24, 1810. A physics laboratory at the University of Cambridge, established in 1871, is named after him.
Interesting Facts
- Cavendish's favorite way to spend money was through charity work. Once, having learned that a student who was helping him organize his library was in a difficult financial situation, Cavendish immediately wrote him a check for 10 thousand pounds - a huge sum at that time. He acted in this way all his life - and, nevertheless, he always had millions of pounds sterling at his disposal, as if he had a fabulous “irredeemable ruble.” Some believe that this inexhaustible wealth was brought to him by his successful studies in alchemy, but this, of course, is only an assumption.
- Cavendish behaved strangely towards those around him: he could not stand it when anyone addressed him, and if some stranger spoke to him on the street, Cavendish would silently turn away, hail a cab and immediately return home. He generally considered women to be some kind of people with whom he did not want to have anything in common. He ordered an external staircase to be added to the house and ordered the servants to use only it. Those of them who dared to use the internal ones, he immediately fired.
- They tell the following story. One day Cavendish dined at the Royal Scientific Society club. At this time, a young beautiful woman appeared in the window of the house opposite and began to examine the passing carriages. Many of the men present in the club came to the window to get a better look at her. Deciding for some reason that they were admiring the full moon, Cavendish was about to join them, but realizing his mistake, he immediately left the club, out loud expressing his disgust at what was happening.
- The scientist’s will contained a categorical requirement that the crypt with his coffin be tightly walled up immediately after the funeral, and there were no inscriptions outside indicating who was buried in this crypt. And so it was done. Cavendish was buried on 12 March 1810 in Derby Cathedral. Neither an examination of the body nor an autopsy was performed. And not a single reliable portrait of Cavendish has survived either.
- Most of Cavendish's scientific works were not published until 1921, and even now several boxes filled with manuscripts and instruments whose purpose cannot be determined remain undisassembled. And what little is known looks very unusual.
- Cavendish conducted scientific experiments that were centuries ahead of his time. For example, he calculated the deflections of light rays due to the mass of the Sun, 200 years before Albert Einstein, and his calculations almost coincide with Einstein’s. He accurately calculated the mass of our planet and was able to separate light gases from the atmospheric air. At the same time, he did not care at all about the publication of his works, or about any recognition by the scientific world.
- Cavendish could determine the strength of the current by touching an electrical circuit with his hand, which indicates his extraordinary physical qualities. Despite the very modest, from the point of view of modern science, capabilities of his laboratory, he was able to very accurately calculate the mass of the Earth. And Cavendish made all these extraordinary, outstanding discoveries, relying not even on the science of his time, but using the achievements of medieval alchemy, the language and symbols of which he mastered.
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