In Wencheng Village, in the newly built school, the teacher is giving a lecture on how steel is made.

When it comes to how steel is made, it is natural to think of a book, "How Steel is Made" by the former Soviet writer Nikolai Ostrovsky.

At the moment, the school is not telling a story about that book, but about how steel is made.

How steel is made, there is this passage in this book:

The most precious thing for a person is life, and life is only once for a person. A man's life should be spent in such a way that when he looks back, he will not regret that he has done nothing and wasted his time, nor will he feel guilty for being a despicable person and living a vulgar life.

In fact, what this book talks about is very similar to real ironmaking, and steel can only be tempered in a thousand tempers.

Giving children the basics of ironmaking and steelmaking can help them learn a lot, and although they can only get a rough idea, they can at least make an impression and learn to increase their knowledge. Slowly cultivating their interest, a semester of study is almost over, and the school organizes an exam.

The subjects of the exam are: pinyin, arithmetic and ancient poetry, as well as basic chemistry and physics.

In addition, the school also taught everyone about salt making.

Salt is the necessities of people's lives, but also the basic raw materials of the chemical industry, salt has a wide range of uses in agriculture, animal husbandry and fishery, in ancient society, salt and iron is an important source of national financial income. Tell the children how to make salt and tell them the importance of salt so that they know the origin of iodized salt.

In modern society, everyone knows the importance of iodine, but in fact, table salt itself does not contain iodine.

Iodized salt refers to salt containing potassium iodate sodium chloride, salt itself does not need to be iodized, but due to the lack of iodine in most parts of China, the shortcomings will cause iodine deficiency disease, so the state compulsorily adds a small amount of iodized salt to the edible sodium chloride salt, so now you can buy salt with the iodized salt mark in the market.

The children learned several ways to make salt:

The first is called the boiling method: the process of the decoction method is to make salt brine first, and then boil salt.

The first is to make brine (scraping mud and leaching leakage), spread mud with salty mud in the leaky bowl, wait for its salty quality to drain out, it is dug out with a shovel, and piled up around the leaky bowl, which is called light mud, also known as raw mud.

There are many accumulations, when the weather is fine or the west wind blows strongly, pick up the salt field with a basket, repave the field, let the sea water flow into the salt field, the salt is absorbed by the light mud, the sun blows, the water vapor evaporates, the salt attracts up, the field is as white as frost, so it is called the white ground (that is, the salt flower).

After scraping the mud and waiting for the salt field to whiten, flatten the waist of the towing knife with both hands, and walk backwards according to the frame of the towing knife, scraping the floating mud on the surface of the field into pieces. The mud scraped by the mud is unevenly wet and dry, dried in the sun, and then dragged and scratched by the backs of the two people, and repeatedly copied to make it dry and loose.

The mud is dry and loose, and two people will cut the board to make the soil integrated into a straight line, and each line is about 3.5 meters apart to facilitate soil picking.

Most of the mud collection is carried out by women and children. Pick the mud to put the salty mud into the soil basket, shoulder to the center of the soil foundation, pile up like a fu, called the mud canopy, press to make it extremely hard, into a sharp cone, so that the rainwater will not seep in, at any time into the leaky bowl, carry the water and leach the brine, this is called the mud pile.

The bottom of the leakage bowl is first covered with a layer of dried weed or ridge hair, and then the salty mud of the mud canopy is put into it to make it level with the mouth, and it is solid with both feet, and it is smooth and smooth as a mirror.

After the leakage control is completed, the bucket is used to draw seawater from the canal, pour the leaky bowl, and every few hours or half a day, the salt brine is poured into the bamboo pipe from the bottom of the drain through the grass root or ridge hair, and poured into the brine tank. After the brine jar is full, it is extracted with a brine hang, poured into the bucket, and hidden in other tanks or brine barrels for the purpose of boiling.

The iron plate is rectangular and is composed of 3~8 pieces of iron about one inch thick. The joints are filled with lime.

It is erected on the top of the pointed stove, and then woven with ribbon-shaped bamboo strips, surrounded by iron plates, and the inside and outside of the bamboo and the junction of the bamboo and the iron plate, are also smeared with lime, which is called a masonry plate.

One end of the iron disc is close to the fire door, and its rear end is on the stove. If there is still room for it, 2~4 iron pots are arranged longitudinally, which is called a warm pot.

After the plate is made, the brine is poured into the plate with bamboo from the brine barrel, and at the same time it is filled with a warm pot, and the firewood is put into the fire door to open the frying. After the brine in the warm pot is cooked, exchange it and hang it into a plate towel, and then pour the cold brine into the warm pot.

This is carried out repeatedly, the salt brine water in the dish evaporates, the salt gradually crystallizes, and then the high temperature is added to make all the bitter brine in the dish dry, and the salt has been made at this time, and the salt is copied into the basket with a salt shovel.

Fry one plate for about 1.5~2.5 hours. And so on, day and night. On the fourth and tenth days, the fire is extinguished, and it is called a creation. Each stove has a certain period of time, which is determined by the field officer.

After the ignition is turned off, the iron plate will be disassembled, and then fried and rebuilt with a new plate. One load of brine can be boiled 10 kg of salt. Its salt contains a variety of impurities, the taste is astringent and bitter, the color is slightly black, the cost is high, and the yield is low.

Another method is called the plate drying method:

This method can also be carried out at home, with the door board at home to fill the halogen test drying, the salt of the board drying, less impurities, white color and fresh taste, low cost, high yield.

Pick brine in the place where the tide returns to the sea, cut off the grass roots, and the light is as flat as a mirror, which is called the ash field (referring to the soil as fine as ash).

The ash field is divided into three sections: the offshore area is soaked in tidal water, which is not easy to be exposed to the sun, and is the end;

The middle part of it is tidal and receding, and it is susceptible to sun exposure, which is the midfield;

Those who are far away from the sea, with the tide is not small, and they will be flooded with water, so they are called on the field.

Tide: 13-18 in the first half of the lunar calendar, from the 27th to the third day of the next month, the tide is full on the 6th.

On the day of the big tide, there are no three games, since the third and eighteenth days of the new year, the tide is decreasing, the first is on the field, the second is in the middle of the field, and then the sun is down.

Therefore, the upper and middle games can be dried twice a month, and the next field can only be exposed once.

Wait for the salt frost on the ground and put it away with a shovel, which is called scraping. The soil is piled up in the pier tower, the bamboo pipe is run through, a well is opened next to it, and the tile cylinder is buried.

There are mostly one well per tower, and there are also two towers and one well. The pier tower is piled up, watered on it, and the brine flows into the well by the bamboo pipe, and then the brine in the well is hoisted out and stored in a large bucket for the purpose of drying salt.

On a sunny day, at 5~6 o'clock in the morning, the salt board is distributed on the ground, and then the brine storage is poured on the board with a wooden ladle until the flat mouth.

After being exposed to the sun, to 2~3 o'clock in the afternoon, white particles appear at the bottom of the board, scraped and gathered with a wooden board, and the brine that has not yet become salt is stored in the basket, and the brine is dripping into white salt.

The sun is weak in spring and winter, and the daily salt per plate ranges from 0.25~0.75 kg. In summer and autumn, when the production is prosperous, each plate produces about 2 kg of salt per day.

Beach drying: Divide the beach into a number of lattice beach fields, directly use sea water, from high to down, according to the beach field water to make brine, and then by the crystallization pond to dry salt. The salt production method on this beach saves time and effort, and the yield is also high.

In modern salt production, seawater is extracted from the sea and filtered through a sophisticated process.

At this time, the filtered seawater is more than 10 times cleaner than the original seawater.

After that, the seawater is concentrated by the membrane concentration method, which not only bears a certain electric charge, but also has thousands of small holes with a diameter of 1 mm, through which the salt is passed through the membrane to complete the brine concentration process, this method is membrane dialysis.

In this process, direct current is used as an energy source for the thin-film dialysis process. This method of concentrating seawater is a brine mining method used in the Japanese salt production process.

The concentrated brine contains a large amount of salt. The salt content of ordinary seawater does not exceed 3.3%, but the salt content of seawater treated by membrane dialysis can reach 20%!!

In addition, by using this electrically charged film, it is possible to remove contaminants and various bacteria from seawater.

By membrane dialysis, the concentration of the brine reaches 20 times that of the original halide, after which the brine is introduced into an evaporation tank and crystallized by evaporation at high temperature by heating to make salt. Normally, the volume of the evaporation tank is about 5 meters in diameter and 15 meters in height, and four evaporation tanks are used at the same time in the salt production process.

The brine is heated at high temperatures inside the evaporation tank and is constantly stirred. A vacuum is formed inside the evaporation tank, and this energy can complete the evaporation crystallization process with 3 times the original amount of steam. This method can be called either vacuum evaporation or multi-utility evaporation, and is a production method that can save energy and reduce consumption.

During the evaporation process, the particle size of the salt crystals in the evaporation tank can also be controlled by careful planning adjustments. The wet salt discharged from the evaporation tank needs to be passed through a centrifuge to separate the salt crystals from the bitter brine. After that, the moist salt is heated and dried at high temperatures to make table salt and premium salt.