Text: The boiling point of water is 100℃. Why does the advertisement say that water can be heated to 125℃ for sterilization?

Everyone knows that boiling water is 100℃. Seriously, the new regulations were implemented after 1990. The boiling point of water at standard atmospheric pressure is 99.974℃. How can I heat the water to 125℃ for sterilization? Isn't this pseudoscience?

The origin of raw potatoes and pressure cookers

Papin, a great French scientist, once cooked potatoes on the top of the mountain when he was still a baby, but he couldn't understand it. In fact, many people had similar experiences at that time, so they either roasted or simmered on the mountain, but Papin wrote it down!

Later, he had the opportunity to work with the great chemist and physicist Boyle. He asked Boyle when he remembered the cooking of the earth on the top of the mountain. Boyle told him that the boiling point of water would decrease with the decrease of atmospheric pressure. The air pressure at the top of the mountain is lower than that in the plain, so the boiling point is very simple!

Boyle

This Papin is an expert in DIY. He quickly thought of a way to keep the air pressure and let the boiling point of water return to the plain. He immediately made a special pressure cooker, which was clamped and locked in place with screws to prevent steam from lifting the lid. After several cooking experiments, the effect is quite good, and he even used this pressure cooker to cook when entertaining friends, which won unanimous praise!

But unfortunately, the pressure cooker invented by Papin did not attract attention at that time. Because of its troublesome structure and inconvenient use, it can only be used as special laboratory equipment, and it may even explode, which makes everyone stay away from this pressure cooker. Later, the pressure relief valve was invented, but it was not until nearly 200 years after Papin's death that the pressure cooker was accepted by everyone and became popular all over the world!

However, Papin has made countless contributions to steam power, safety valves and centrifugal pumps all his life, but he still spent his life in poverty, and finally he couldn't even find a tombstone!

Supercritical and ultra-supercritical boilers

The water in the pressure cooker can cook food quickly on the mountain, because the steam generated by water is enclosed in a closed space, which can increase the pressure, and then the boiling point of water rises, even exceeding 100℃. Generally, the atmospheric pressure of the pressure cooker is 40~80Kpa, and one atmospheric pressure is 100Kpa, so the pressure in the pressure cooker is about 1.4 ~ 65433.

So if the pressure is infinite, will the boiling temperature of water keep rising? It seems to be the result, but there is a condition that when the pressure is 22. 1MPa and the temperature reaches 374℃, water becomes supercritical water. At this time, the density of water expanded by high temperature is exactly the same as that of water vapor compressed by high pressure. At this time, there is no difference between the liquid state and the gas state of water!

They are completely integrated and become a new high-temperature and high-pressure fluid. This is the magical property of supercritical fluid discovered by Baron Canard Delatour in the experiment of 1822. At present, supercritical state has many applications, such as supercritical extraction of carbon dioxide, because the supercritical temperature of carbon dioxide is only 3 1. 1 degree Celsius, and the pressure only needs 72.8 standard atmospheric pressure.

Therefore, supercritical carbon dioxide extraction of caffeine or plant essential oil from coffee beans can be operated at low temperature, while high temperature will not affect the chemical properties of the extract, so the application of supercritical carbon dioxide extraction is very convenient.

Ultra-supercritical unit

Just mentioned above, when the temperature of water reaches 374℃ at 22. 1MPa, it becomes supercritical, but there is no upper limit for this temperature. Therefore, in this closed pressure vessel, the pressure can continue to be unbearable. Generally, the working medium pressure in the furnace is called subcritical boiler, and above this pressure, it reaches the level of supercritical boiler. If the steam temperature in the furnace is higher than 593℃ or the steam pressure is not lower than 36544.

So theoretically, a brand of mineral water is sterilized at 125℃. Actually, there's nothing wrong with it. As long as there is enough pressure, nothing can be done. 125℃ is about 2 atmospheres, which is still very easy to achieve! Many ordinary pressure cookers can reach this pressure, but using this as a propaganda selling point seems to be a title party, which is also a perfect copy!

The history of human civilization is the history of boiling water.

Speaking of boiling water, in fact, the whole history of civilization is a history of boiling water! In the past, we often boiled water for cooking. Later, scientists invented the steam engine, and the boiling steam pushed the piston to output power. Later, the steam turbine appeared, and the way of burning water changed from firewood to coal and natural gas!

Later, man discovered nuclear fission. Although it was first used to make atomic bombs, it was later found that a large amount of heat released by nuclear fission could be used to boil water to drive steam turbines, so nuclear power plants appeared! The energy of nuclear power plants is extremely huge, and uranium mines on the earth can fully meet the development of human civilization, but unfortunately, nuclear fission has a lot of radiation, and the waste is very difficult to deal with!

So now scientists are studying nuclear fusion, which sounds tall, but it is still used to boil water to drive steam turbines. It seems that human civilization has always learned to boil water. When can we get out of this boiling water era? It is estimated that only in this way can civilization go up a storey still higher!