Sea water is inexhaustible, and if there is a war one day in the future, we should take refuge on the island in order to escape the war, how should we solve the problem of "salt"?
First of all, we have to understand, why do human beings eat salt, and can they not eat it?
The answer is "absolutely not", salt can open the channel of the tube wall and cell membrane, simply put, nutrients cannot be directly absorbed by the cell, but need to pass through a door, and this door is the sodium and potassium ions in the salt.
At the same time, the waste products produced by cells also need to be excreted through the "gate", and our body cannot synthesize the "gate" independently, so it can only be ingested from the outside, that is, we need to ingest salt from nature.
Is there salt in seawater?
You may think this is nonsense, but at the beginning, the sea water was not salty like fresh water, and the reason why the sea water is very salty today is because the rain washes the salt from the soil and rocks on the land into the sea, and the sea water evaporates and rises, and continues to form rain on the land, and so on, and the salt content in the sea water naturally gets higher and higher.
In fact, there is also salt in rivers and lakes, but the content is too low for us to detect, so can we drink seawater directly?
It seems to be nonsense, but it is still necessary to understand the scientific principle, in addition to salt, there are about 47 minerals and metals in seawater, such as magnesium, sulfur, calcium, potassium, bromine, carbon, strontium, boron, fluorine, etc., on average, every 1 million liters of seawater contains 1270 kilograms of magnesium, 400 kilograms of calcium and 380 kilograms of potassium, unexpectedly, there is uranium in seawater, and the total amount of uranium in the global ocean can reach 4.5 billion tons.
Is it because seawater contains minerals and metals, so seawater cannot be drunk directly? Actually, it is not right, because these substances are evenly distributed in the ocean, and the content of minerals and metal substances in the little seawater that humans drink is negligible, and the reason why seawater cannot be drunk directly is because of "salt".
The concentration of salt in seawater is 3.5%, and if all the seawater is evaporated, 500 million tons of salt will be obtained, and the thickness of the flat surface on the land surface can reach 166 meters, which is about the height of a 59-story building at a height of 2.8 meters per floor of commercial housing.
The salinity of seawater, about 250ml of water to add 9 grams of salt, when the human body drinks seawater, because the concentration of seawater is too high, the concentration of salt in the body is low, in order to balance, the water in the body will continue to precipitate until the internal and external salinity is balanced, which is the meaning of dehydration, and the liquid with high salinity will also exceed the working range of the kidneys, so human beings can not directly drink seawater to obtain salt, otherwise it will only accelerate death.
Since the human body needs to consume salt, and cannot drink seawater directly, what other way can we get salt from seawater?
The wisdom of human beings lies in "wisdom", we can take some seawater and heat it directly with firewood to obtain salt crystals, but it is too wasteful to use the flame to heat it at the beginning, so it is a good choice to use the ancient method of salt production by the people by the sea.
The first step is to build multiple dikes on the beach, at high tide, the sea water will flood the dikes, but at low tide, the dikes will intercept a part of the seawater, which is gradually carried away by nature after being exposed to the wind and sun, leaving behind crystals rich in salt and other substances.
If you repeat the above operations many times, you can get seawater with a high salt concentration, which is called "brine", when is it qualified?
Throw 10 lotus seeds in the brine, if the 10 lotus seeds are floating on the surface of the water, it means that the "brine" is very thick, and you can proceed to the next step, at this time you can use artificial heating.
The salt content in the brine is very high and the water content is low, so as long as you use a small amount of heat energy, you can obtain salt crystals, that is, coarse salt, and collect it after shoveling down the coarse salt, but at this time, you must not eat coarse salt directly, after all, there are still a lot of impurities in it.
The next step is to purify the coarse salt, reheat part of the brine to 90 °C, and then pour in the coarse salt, you can get a higher purity salt.
In the brine at 90 °C, the saturated solubility of sodium chloride is 39 grams, and the magnesium chloride is 70 grams, and the coarse salt is continuously added, because the saturated solubility of sodium chloride is low, so the sodium chloride in the coarse salt will not be "eaten" by the brine, and the impurities such as magnesium chloride in the coarse salt will be "eaten" by the brine because of the high saturation solubility, so as to achieve the effect of purifying the coarse salt.
If you simply drink seawater, it will definitely not work, if you do not purify the coarse salt, it may be fine in the short term, but after a long time, the impurities in the coarse salt will become more and more in the human body, and it will not take long for the human body to get sick, and the medical conditions of the island where you are taking refuge are limited, it is difficult to carry out effective treatment, and finally there is a high probability of death.
You may wonder why humans eat salt, why haven't you heard that animals eat salt?
In fact, animals also eat salt, they will lick the salt crystals left on the rocks, such as rock sheep, and even risk their lives to eat salt on steep cliffs in order to eat a mouthful of salt.
Some cattle farmers also regularly provide rocks for their cattle to lick, and carnivores, such as lions and tigers, will draw salt from herbivores when eating herbivores, so salt is important not only for humans, but also for animals.
It is precisely because of the importance of salt that it will be strictly controlled in ancient times, after all, the difficulty of making salt in ancient times is not high, but whoever controls salt has a lot of right to speak, so salt is an important strategic material in ancient times, and it is forbidden to sell it privately.