Phlogiston is filled between heaven and earth and flows in lightning storms. It is contained in the earth, sky, ocean, land, animals, plants, minerals and people's hearts. The atmosphere contains phlogiston, which will cause lightning in the air and make the atmosphere turbulent; Living things are full of vitality when they contain phlogiston; When inanimate matter contains phlogiston, it will burn. Phlogiston not only has various mechanical properties, but also, like the soul, it is a kind of power and a kind of "fire power". Objects lose phlogiston, become ashes, ashes gain phlogiston, and objects will be resurrected.
When a substance is heated, phlogiston cannot decompose automatically. But combustion can only be achieved by adding air to suck out phlogiston; Good air has the property of absorbing phlogiston.
Corrosive agents seize phlogiston in metal, and the metal is corroded; When metals are calcined, they lose their noble light and become dross-when they are endowed with phlogiston, they become arrogant again.
The more phlogiston in an object, the more it burns; Less phlogiston, weak combustion. Good air has the property of absorbing phlogiston, so objects must be in the air to burn; All kinds of entities are composed of basic substances (elements) owned by an object and its unique "gas field", which can be distinguished by fire. When the entity is heated, the "gas field" escapes from the entity.
Because the mass of metals and other substances increases after oxidation, some scientists think that phlogiston, like "halo", repels the center of the earth and has a negative weight (so-called "light weight"), so when metals lose phlogiston, their weight increases instead. Some people say that the loss of phlogiston in metal is like the loss of the soul of the living, so just as the body of the dead is heavier than that of the living, the "dead" ashes are naturally heavier than the living metal. The phlogiston theory proved to be wrong.
The phlogiston theory was formed at the end of 17 and the beginning of 18 to explain the combustion phenomenon and even the whole chemistry. According to phlogiston theory, combustible elements are gaseous substances, which exist in all combustible substances, and this element is phlogiston; When burning, phlogiston flies out of combustible materials and combines with air, thus emitting light and heating, which is fire; Grease, wax, charcoal, etc. Are extremely phlogiston-rich substances, so the combustion is very intense; Stone, wood ash and gold do not contain phlogiston, so they cannot be burned. Chemical changes of substances can also be attributed to the process of releasing phlogiston or absorbing phlogiston. For example, when zinc or lead is calcined and phlogiston escapes from it, white zinc ash and red lead ash are produced; When zinc ash and lead ash are roasted with charcoal, zinc ash and lead ash absorb phlogiston from charcoal, and the metal is regenerated. Alcohol is a mixture of water and phlogiston. Water still exists after alcohol is burned. The dissolution of metal in acid is the process that phlogiston is taken away by acid. At that time, the phlogiston theory could not be justified, and the biggest criticism was the fact that metal gained weight after calcination. With more quantitative research on chemical reactions, phlogiston theory becomes more contradictory. It was not until the discovery of oxygen in the 1970s of 18 that the essence of combustion was finally revealed to the world, and phlogiston theory withdrew from the historical stage.
At first, medical chemists imagined that chemicals contain three elements: sulfur is combustible, mercury is mobile and volatile, and salt is fixed and inactive.
In the17th century, Joachim Becher, a medical professor at the University of Mainz, slightly revised the theory of medical chemistry, and proposed in 1669 that solid soil materials generally contain three components:
"Stone soil", a kind of fixed soil existing in all solids, is equivalent to the salt element of early medical chemists.
"Oily soil", which exists in all combustible materials, is equivalent to sulfur.
"Mercury soil", a mobile soil, is equivalent to mercury.
Priestley believes that all combustible materials contain sulfur and oily "oil soil", which escapes when burning with other "soil"; In other words, combustion is a kind of decomposition. The ash left after burning is a simpler substance.
According to phlogiston theory, the process of combustion and calcination involves the decomposition of compounds into components, that is, into sulfur "oil soil" and fixed "stone soil" in the simplest case. Theoretically, a simple object can't burn, because the substance containing "oil soil" and another soil must be a compound.
In the18th century, the supporters of new chemical concepts and phlogiston theory had a heated debate. 1703, Georg Ernst Starr, a professor of medicine and chemistry at Harley University, renamed priestley's "petroleum soil" as "phlogiston" and developed this theory into a broader theoretical system to explain many chemical phenomena such as oxidation, respiration, combustion and decomposition. Metals are compounds of ash and phlogiston. When heated, phlogiston is released, leaving ashes. Generally speaking, phlogiston is the basic element of all combustible objects, and fuels such as oil, fat, wood and carbon all contain a lot of phlogiston. When these objects burn, phlogiston is released, either into the atmosphere or into substances that can combine with them, such as ashes, thus forming metals.
By 1740, phlogiston theory was generally accepted in France; Ten years later, this view became an accepted chemical theory.
However, phlogiston theory failed to reasonably explain the results of quantitative experiments; According to phlogiston, magnesium will release phlogiston after burning, but in fact its weight will increase instead of decrease. Later, lavoisier proved that oxygen is essential in the combustion process, explained the phenomenon of weight increase after combustion, and laid the foundation for the later heat theory.
The phlogiston theory reversed the explanation of combustion phenomenon and described the combination process as decomposition process, but unified the explanation of most chemical phenomena at that time, helped people get rid of and end the rule of alchemy, liberated chemistry and played a positive role in history. Although the phlogiston theory itself is wrong, it guides and inspires people to think and explore, and constantly practice, verify, correct hypotheses or make new discoveries. It is also a large number of scientific experimental data accumulated in this continuous process that prepare the conditions for the establishment of scientific combustion theory.
British chemist priestley visited Paris. At the banquet held in lavoisier, priestley told lavoisier that three months ago, he found a gas with remarkable combustion-supporting effect in the experiment of heating water and silver ash. This information inspired lavoisier, who immediately set about synthesizing and decomposing biscite. Lavoisier was convinced by the experimental facts that it was not fire particles or phlogiston that combined with metal in combustion, but probably the purest air.
At the end of 1775, after priestley published a paper on oxygen (he named it defluorinated air), lavoisier suddenly realized that this special substance was a new gas element. Later, he made a careful investigation on the properties of this new gas element, and confirmed that this element can not only support combustion and respiration, but also combine with many nonmetallic substances to generate various acids. Therefore, he named this element acid, and now the chemical symbol 0 of oxygen comes from the Greek acid: oxygen.
After a systematic study of oxygen, lavoisier clearly pointed out that air itself is not an element, but a mixture, mainly composed of oxygen and nitrogen.
In 1778, he further pointed out that the combustion process is a combination of combustible substances and oxygen in any case, and combustible substances absorb oxygen and gain weight during combustion. The so-called phlogiston does not actually exist. Lavoisier's combustion oxidation theory finally made people understand the essence of combustion, replaced the phlogiston theory, unified the experimental facts of many chemical reactions, and laid an important foundation for the development of chemistry.
Water has long been considered as an element. Lavoisier not only synthesized water through experiments, but also decomposed water into oxygen and hydrogen, confirmed the composition of water, and gave an accurate explanation with the oxidation theory. According to the theory of oxidation, lavoisier published a paper in 1777, pointing out that animal breathing is inhaling oxygen and exhaling carbonic acid gas, which is also a burning phenomenon. In cooperation with Laplace, a French scientist, he designed an ice calorimeter at 1782 and measured the specific heat and latent heat of some substances.