Salt, scientific name of sodium chloride, is an indispensable substance for human consumption and industrial production. In other ways, it also has wonderful functions.
I. Salt in the body
Salt is indispensable to the human body. If the human body is short of salt, people will be dizzy, tired and don't think about eating. In the long run, it will cause many diseases, white hair.
In the hospital, we often see patients infusion, many of which are sodium chloride saline (that is, 0.9% saline).
Why does the concentration of normal saline have to be 0.9%? Let's analyze an interesting experimental phenomenon first.
About 200 years ago, in order to improve the method of brewing wine, people filled a round glass tube with alcohol, and then, at the lower end of the glass tube, it was sealed with animal bladder membrane. The lower end of the glass tube was immersed in water, and soon it was found that the bladder membrane bulged automatically. Obviously, this is water seeping into the alcohol tank through the bladder membrane. The swelling of the liquid in the cylinder is called osmosis, while the films such as bladder membrane, cell membrane, sheepskin and cellophane are called semi-permeable membranes.
The leakage phenomenon is regular. If the two kinds of brine are separated by a semi-permeable membrane, the water in the salt solution always permeates from the weak brine to the strong brine until the concentrations on both sides are equal.
Blood in the human body contains salt. Blood consists of red blood cells and liquid plasma. There are three kinds of blood cells: red blood cells, white blood cells and platelets, of which red blood cells account for the vast majority. The cell membrane is a semipermeable membrane. Under normal circumstances, intracellular solution and extracellular plasma solution must maintain a certain concentration. When people are infusion, the saline solution entering the plasma must also maintain a certain concentration, that is, 0.09%. If normal saline is diluted or distilled water is misused, the concentration of plasma will be diluted after infusion, so that the water in plasma will penetrate into blood cells with high concentration. As a result, blood cells swell or even rupture, leading to hemolysis. If the physiological saline is too thick, the water in the blood cells will seep out again. So generally speaking, normal saline must be 0.9%.
In case of special circumstances, such as severe dehydration of plasma caused by extensive burns, it is necessary to use less than 0.9% normal saline infusion to supplement the lack of water in plasma; If the patient's plasma water content increases due to excessive sodium loss, it is necessary to use more than 0.9% physiological saline infusion to increase the blood plasma concentration.
In our daily life, we often use the concentration of physiological saline. For example, in a hospital, eye drops should be prepared to a certain concentration, otherwise the eyes will be dehydrated or painful. When swimming, you won't feel pain when you open your eyes in seawater, but you will feel uncomfortable in fresh water. That's the reason. For example, when curing meat, we usually use strong brine to sterilize it, and the meat that loses moisture is easy to preserve.
The more salt, the better.
An expert in Britain said that excessive salt is harmful to human health, and six grams a day is enough. People have long known that excessive consumption of salt will have adverse effects on health. In daily life, people can easily control their salt intake. When cooking or cooking by themselves, they can adjust the amount of salt according to their own tastes. However, according to the survey, three-quarters of British people usually eat semi-finished or fully processed food to get salt. However, the current food processing enterprises are completely unaware of the importance of their responsibilities. They often add a lot of salt to semi-finished products or processed foods. Although these enterprises have reduced the consumption of edible salt under the pressure of medical work, they still far exceed the standard requirements.
According to experts, the maximum daily salt intake is 6 grams, but now the average daily salt intake of most British people is about 9.5 grams, which leads to many people suffering from cardiovascular diseases.
If the daily intake of salt reaches the standard, the number of people suffering from myocardial infarction will decrease by 13%. However, the representative of the British Food Industry Association said that this may lead more British people to buy imported food, because now more and more British people prefer to eat green food. In order to meet people's requirements, they are constantly trying to reduce the content of edible salt in food.
At the same time, experts also pointed out that sea salt and mineral salt are essentially the same, and excessive consumption is harmful to human body.
Finally, experts say that salt plays a key role in regulating the taste of food and coordinating the functions of various organs of human body, but the best effect can be achieved only by ingesting appropriate amount of salt, otherwise it will cause harm to human body.
Four. Anecdotes about salt
For example, in western Asia, there is an inland sea called the Dead Sea in the Jordan Valley. There is no grass around it, and there is not even a fish or weed in the lake. When people in ancient times discovered this strange phenomenon, they called it the Dead Sea, which means the lifeless sea. It was not until modern times that the salinity of the Dead Sea was as high as 25%, which was caused by years of drought, lake surface decline and rising salt concentration. Today, it has become a tourist area, and many tourists are looking forward to visiting the sea. It turns out that people can't sink when swimming in this kind of sea, and the density of sea water is greater than that of human body, which produces great buoyancy.
In recent years, foreign research has found a wonderful function of salt. In the baby selection experiments in Canada and France, the method that women eat salty food rich in sodium and potassium before pregnancy was adopted to give birth to boys. Eat more milk, cheese, eggs, sweet butter and foods rich in calcium and magnesium, and you will have girls. The success rate of the experiment is over 80%. As for why diet control can choose the baby's sex, it is still under study.
Salt, our close partner in life, its wonderful function tells us that the salt eaten in daily life has a vital influence on people's physiological activities and health. Salt, such a common substance in our life, contains so many chemical reasons. It can be seen that there is actually a lot of chemical knowledge in life. As long as we pay more attention, it will definitely help our health.