Salt, whose scientific name is sodium chloride, is indispensable for human consumption and industrial production. In other respects, it also has wonderful functions.
I. Salt in the body
Salt is indispensable to the human body. If there is a lack of salt in the human body, people will be dizzy, weak, and do not think about diet. If it goes on for a long time, it will cause many diseases and turn white hair.
In hospitals, we often see patients infusion, many of which are sodium chloride physiological saline (that is, 0.9% saline solution).
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 tightly sealed with animal bladder membrane. When the lower end of the glass tube was immersed in water, it was soon found that the bladder membrane bulged automatically. Obviously, this is the water permeating into the alcohol cylinder through the bladder membrane. The liquid in the cylinder bulges, which is called osmosis, while films such as bladder membrane, cell membrane, sheep skin and cellophane are called semi-permeable membranes.
There is a rule of seepage phenomenon. If we use a semi-permeable membrane to separate two kinds of brine, the water in the salt solution always permeates from the dilute brine to the concentrated brine until the concentrations on both sides are equal.
The blood in the human body contains salt. Blood is composed of red blood cells and liquid plasma. There are three kinds of blood cells: red blood cells, white blood cells and platelets, among which red blood cells account for the vast majority. Cell membrane is a semipermeable membrane. Under normal circumstances, the intracellular solution and extracellular plasma solution must maintain a certain concentration. When people are infusion, the saline solution that enters the plasma must also maintain a certain concentration, that is, 0.09%. If the 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 and even rupture, resulting in hemolysis. If the physiological saline is too thick, then the water in the blood cells will seep out again. Therefore, in general, physiological 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% physiological saline infusion to supplement the lack of water in plasma; If the patient's water content in plasma increases due to excessive sodium loss, it is necessary to use normal saline infusion above 0.9% to increase the concentration of blood paddle.
In our daily life, we often use the concentration of saline. For example, in hospitals, eye drops should be prepared with 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 when you are in fresh water. This is the reason. For example, when curing meat, we usually use concentrated brine to sterilize it, and the meat that has lost moisture is easy to preserve.
3. Salt is not the more the better
An expert in Britain said that excessive salt is harmful to human health, and six grams a day is enough. It has been known for a long time that excessive consumption of salt will bring adverse effects on health. In daily life, it is easy for people to 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 food or processed food. 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 intake of salt is 6 grams, but now the average daily intake of salt by most British people is about 9.5 grams, which leads to cardiovascular diseases in many people.
If the daily intake of edible salt meets the standard requirements, the number of people suffering from myocardial infarction will decrease 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 now making continuous efforts 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 all organs in the human body, but the best effect can be achieved only by ingesting appropriate amount of salt, otherwise it will cause harm to the human body.
IV. Anecdotes about salt
For example, in the west of Asia, there is a inland sea named Dead Sea in the Jordan Valley. There is no grass around it, and there is not even a fish or a weed in the lake. When people in ancient times discovered this strange phenomenon, they called it the Dead Sea, which means there is no sea of life. It was not until modern times that it was discovered that the salinity of the Dead Sea was as high as 25%, which was caused by the continuous increase of salt concentration due to years of drought and the decline of the lake surface. 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 sea, and the density of seawater is greater than that of human body, which produces great buoyancy.
In recent years, a wonderful function of salt has been discovered in foreign research. In the experiments on baby selection conducted 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, foods rich in calcium and magnesium, and you will have girls. The success rate of the experiment is as high as over 80%. As for why controlling the diet can choose the sex of the baby, it is still under study.
Salt, a close partner of our life, its wonderful functions tell us that the salt we eat in our daily life has a vital impact 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.