4
But what exactly is this value equal to 1 A. E. M.? If you answer this question, you can find the masses of all other types of atoms, at the same time prove their reality. But none of the atoms, even the largest of them, can be seen in any microscope at that time. The situation is saved by the discovery made in 1828 by the English botanist Robert Brown. When a new microscope was brought to Robert Brown, he left it in the garden, and in the morning, dew drops formed on the "table" of the microscope, and Brown himself forgot to wipe them and automatically looked into the microscope. What was his surprise when he saw that the pollen particles in the dew drop were randomly moving. The particles are not alive and cannot move by themselves. It just couldn't be. But then, when this movement was recorded, some assumptions and hypotheses appeared to explain this phenomenon.
Perhaps this movement was explained by the fact that there are flows in the drop itself due to pressure and temperature differences, such as, for example, the movement of dust particles in the air. After all, if microscopic objects have such a movement, then it must also be in particles with a large size, like dust particles. After all, the movement of dust particles is explained precisely by air flows. But this idea was not confirmed, because the particles did not move in the same direction. After all, in the flow or flow of a jet of air, water or other medium, particles should move only in one direction, and the movement of microscopic particles in Brownian motion does not depend on each other.
In that case, perhaps this movement is the result of the environment? From external sounds, table shakes and other objects? This statement has already been refuted by the French physicist Gui. After conducting a series of experiments, he compared the chaotic Brownian motion with the movement in a remote basement in the village with the movement in the middle of a noisy street. The movements, of course, affected, but they affected only the entire drop as a whole, and not the Brownian motion of the particles itself. Moreover, there was the same movement in gases as in liquids, a striking example of such a movement is the movement of coal particles in tobacco smoke. For a visual example, you can compare two pictures. The way tobacco smoke forms and spreads in the air and the picture in the water, after a drop of paint or dye is dropped into it.
The explanation for all this is given by Carbonel, it is he who explains that the particles fall under the tremors from all sides, which causes their chaotic movement. And the smaller the particles, the more active their movement becomes, since the shocks throw them away more and more, and if the bodies are large, then the number of shocks from all sides somehow becomes almost equal, so furniture, buildings and people themselves do not vibrate by themselves and Brownian motion is not observed. It also turns out that as much as the temperature is higher, so is the velocity of these particles.
This picture becomes even clearer when Richard Sigmondi managed to invent his ultramicroscope, on the basis of which even smaller particles could already be seen. And their movement was no longer a simple movement, it was flickering, jumping and splashing, as Sigmondi himself would describe. But in order to better see this picture, the Svedberg method helped, which reduced the time of the passage of light into the microscope, thanks to which it was possible to fix exactly the specified moment, that is, it was possible to photograph this movement. And with a decrease in the time interval, doing less and less, it became possible to reach the moment when the particles in the photo simply froze in place.
And finally, the year 1908 comes, when it was finally established that atoms exist, have mass and are the basic units of matter, and combining with each other form molecules particles of any complex compound, be it water, acid, the human body, etc.
So, Jean Perrin, a French physicist, decides to study atoms and finds a very amazing way to do it. He takes a drop of gummigut, pieces of rubber resin or yellow paint, if you like. By rubbing this piece in water like a bar of soap, he got yellowish water. But when he took a drop and examined it with a microscope, it turned out that the gummigut was not completely gone, but simply divided into thousands and thousands of small particles of different sizes. Perrin decided that if they are of different sizes and all these are gummigut particles, then they have different masses, therefore, they can be separated using a centrifuge. That is, if you rotate this liquid, then the heavier particles will logically separate to the wall, and the lighter ones will remain.
And with increasing speed, the force increases not twice, but as many times as the speed increased, due to the second degree in the centripetal acceleration formula. Consequently, Mr. Perrin could easily claim that he could separate heavy particles from light particles by strong rotation and he used a centrifuge for this, the same device that rotated with a certain frequency without spilling all the liquid. Perrin used a centrifuge, which thus rotated 2500 times per minute. And even then, only in a small part of the center, places with homogeneous particles were formed, and the rest flew to the edges. Therefore, Mr. Perrin had to use the centrifuge like this several times. Even taking into account the fact that this centrifugal force, even at a radius of 15 cm, already exceeded the force of gravity (the force of gravity of the Earth) by 1,000 times. What can be seen, given that gravity is determined by the product (multiplication) of mass by the acceleration of the fall of any object g, which is the same for all objects and is equal to 9.81 m/ s2 (meters per second squared). And based on the fact that 2500 revolutions per minute are performed, it can be calculated that the angular acceleration according to (1.1).
It remains only to calculate the ratio and get the result (1.2).
The resulting number is indeed more than 1,000, that is, the force at a distance of only 15 cm is already greater than the force of attraction of the entire planet by 1,046.9 times. Thus, in the end, Perrin managed to obtain water only with the specified particle diameters 0.5 (5 out of 10 parts), 0.46, 0.37, 0.21 and 0.14 microns (1 thousandth of a millimeter or 10-6 m, which corresponds to a division of 1/1000000). And finally, having obtained such liquids only with a certain type of gummigut particles (such liquids are called emulsions), Perrin decided to experiment and observe them in a microscope. Watching them, turning the entire cuvette on its side, Perrin noticed that these particles decrease with increasing height. If at first they filled the entire liquid evenly or randomly, then they decreased with height, just as the air in the upper layers of the atmosphere decreases. And that was already a thought! If we compare this with the decrease in air at high altitudes, then we can establish a pattern. But in order to check it, Perrin decided to count these grains at each height.
Alas, it was not possible to photograph them, because the photos were not too clear due to the small size of less than 0.5 microns, and Perrin measured the number of gummigut particles several times at different heights, since the particles were moving, it was not possible to accurately count, so Perrin had to count several times even at the same height, and then say the average number. So at one time, he carried out the calculation at a height of 5, 35, 65 and 95 microns. And it turned out that the number of particles at a height of 35 microns was equal to almost half of the number of particles at a height of 5 microns, and at a height of 65 half of 35, etc. And this already perfectly fell under the law of reducing atmospheric pressure (the force of oxygen pressure on our planet) with an altitude that was determined by Blaise Pascal, the famous French scientist, back in the 17th century. He measured the amount of oxygen using the Torricelli barometer, a pressure measuring device, the principle of which is that at normal air pressure from above, the mercury in the tube is at a certain height, when the pressure becomes less, the mercury can rise, and if the pressure increases, then vice versa decreases, if there is no pressure, like gravity, it is a kind of weightlessness. Having calculated the difference in the layers of the atmosphere, Pascal even then determined that oxygen decreases with increasing altitude for every 5 km. But why is there a 2-fold decrease in gummigut particles only from 5 to 35, and in the atmosphere from 5 to 10, even if we do not take into account the scale?