Early the next morning, Zhang Mao went to the palace with a secret report and a new letter, but Zhang Hao got up an hour later than usual, and when he arrived at Dujia Village in a leisurely manner, it was already noon.

From a distance, Zhang Hao saw two people standing in the blacksmith shop at the entrance of the village, one was Du Blacksmith, and the other was Du Shen who was dressed in shabby Rushan.

Du Shen saw that the stupid apprentice had only come at this time, and said curiously: "Why did the apprentice come at noon today?" ”

Zhang Hao said with a bitter face: "Master, I don't know, after the apprentice went back yesterday, he was beaten by that old thing, and the pain was that he didn't sleep well all night, so he came late." ”

Du Shen shook his head, domestic violence is unacceptable, look at the beating of my apprentice, even my father doesn't shout.

"Apprentice, don't make your father angry in the future, in case you are beaten up, it will be difficult for the teacher to speak for you."

Zhang Hao recalled the dozens of willow whips in his father's drawer, shook his head coldly, and nodded thoughtfully.

"What the master said is very true."

Du Shen bowed, then turned to the blacksmith Du on the side and asked, "Is my blackboard ready?" And the pile of pebbles that was thrown at you yesterday will be taken away today. ”

Du blacksmith Weng Li said angrily: "It's all done, but the stones you let burn, in the early morning, I saw that the burning was fast and took it out, and after cooling down at this time, it was white, you tell me, what is this thing for?" ”

Du Shen pouted, "Naturally, it is useful for me, this is the agreed money, do you see if it is enough." ”

Seeing that he didn't say anything, Blacksmith Du didn't ask any more questions, counted the copper plates handed over by Du Shen, and smiled on his face.

"Enough is enough."

As he spoke, Blacksmith Du enthusiastically and Du Shen carried the blackboard one after the other, while Zhang Hao grinned and carried the bag of burnt stones and walked towards the private school.

When they arrived at the private school, the blacksmith said goodbye and left, and the master and apprentice worked together to hang the blackboard on the wall of the private school.

Wiping the fine sweat oozing from his forehead, Du Shen looked at the blackboard with satisfaction, and finally looked like he was in class.

Frankly speaking, this blackboard is actually not very good, the edges and corners are extremely rough, there are still some prickly hands to touch, and the surface is not very smooth, after all, it is the Ming Dynasty, and the iron-smelting technology is not developed, and it is almost impossible to wrap it with a whole piece of iron.

Blacksmith Du used six pieces of iron to piece together this blackboard.

Fortunately, the traces of the combination can not be seen after the black paint is applied, and it is no problem to use.

At this time, Zhang Hao asked curiously: "Master, this blackboard is used to teach students?" ”

Du Shen said: "Yes, write on the blackboard with chalk, and it can be reused, just wipe off the chalk words with a rag." ”

Saying that, Du Shen instructed Zhang Hao again: "Come with the teacher, and I will teach you the most basic chemical principles today." ”

Zhang Hao hurriedly followed, and the master and apprentice went to the courtyard.

The yard is not very large, with only a stone mill, a willow tree and a water tank.

Of course, the bag of burnt pebbles was also in the yard.

Du Shen first instructed Zhang Hao to take out the pebbles from the bag and put them neatly into the water tank, and then explained to him.

"It's best to use limestone to make chalk, because it contains the most calcium sulfate, and calcium sulfate is lime, but you have also seen that there are three broken private schools for the teacher's family, and one of them is also used as a bedroom, so we can only use pebbles instead."

Zhang Hao put the burnt pebbles into the water tank and asked thoughtfully: "Is it because this pebble also contains the so-called calcium sulfate?" ”

Du Shen approvingly: "Yes, but the calcium sulfate content in the pebbles is not much, and there is only such a small bag after firing, and after it undergoes a chemical reaction to form gypsum, this bag can be left with thirty percent of the incense." ”

Zhang Hao heard it in a fog, racking his brains to figure out the relationship, but as for what calcium sulfate, chemical reactions and gypsum are all things, he has a black eye, and he can only be blind.

After all the pebbles to be burned are placed in the water tank.

Du Shen went to fetch a bucket of water, asked the silly apprentice to wash his hands, and poured it all into the water tank.

Suddenly......

The sound of rattling was accompanied by a large amount of white dust and bubbles.

Zhang Hao was so frightened that he hurriedly stayed away from the water tank, as if there was a fierce beast in it.

Seeing this, Du Shen shook his head and smiled: "What are you afraid of." ”

Zhang Hao pointed to the water tank and said, "Master...... This tank ......"

Du Shen replied: "This is the chemical reaction, the pebbles contain calcium sulfate, after high temperature firing, the impurities in it are removed, and the rest is calcium sulfate and the rest of the substances, which will decompose after soaking in water, calcium sulfate is lighter, the upper part, and the bottom is other messy things." ”

Zhang Hao learned another word, decomposition.

At this moment, he was not afraid, but a little curious, after all, it was the number one scourge in the capital, and he was the character of the eldest and my second child on weekdays, and he walked to the edge of the water tank and watched it.

And the scene inside the water tank is also as Du Shen said.

Zhang Hao saw that the burnt pebbles were soaked in water, gradually splitting apart, and then becoming loose, and slowly, the whole water tank was covered with powder.

Curious, he put his hand into the water tank and crushed the stones that had not been soaked.

Seeing this, Du Shen couldn't help but think of the students before the crossing, and said funny: "Don't put your hands in it for too long, calcium sulfate is acidic, which will corrode people's skin and hair." ”

When Zhang Hao heard this, he quickly took his hand out of the water tank, and at the same time fished out a stone.

"Master, there is a stone here that has no chemical reaction."

Du Shen shrugged his shoulders and said: "It seems that when Blacksmith Du fired these pebbles, he did not deal with them all, the stone was heated unevenly, and the impurities in it were not reduced. ”

As he spoke, Du Shen took another broom and put it in the water tank and began to stir.

While stirring him, he said: "It's too troublesome for you to pinch with your hands, and it's not safe, stand back and let the teacher come." ”

Zhang Hao stood obediently aside, thinking about the teachings of his master just now, while watching the changes in the water tank.

As Du Shen stirred, the slurry in the tank became more cloudy, and when he lifted the broom out of the tank, there were many small stones caught at the end of the broom.

Most of these stones are impurities in the pebbles, neither calcium sulfate nor anything else, and they must be made, otherwise they will have to be picked out one by one when making chalk.

Zhang Hao saw that Du Shen no longer paid attention to the water tank, so he obediently walked over and pinched his master's shoulder.

It's still good to be a teacher, don't say anything by example, and talk so carefully, unlike my father, who knows how to beat himself.

Bah... Old stuff...

……

Forbidden City, inside the Taihe Palace.

The early dynasty has been going on for a while.

Emperor Hongzhi sat on top of the main hall, with eunuchs serving on both sides, and his face was generous, and he did not look majestic, but extremely friendly.

In history, Emperor Hongzhi was an emperor who defended the country, he ruled the country with benevolence, reduced taxes, made great efforts, stabilized the economy and military strength of the Ming Dynasty, and later generations also spoke highly of him.

At this time, the benevolent Emperor Hongzhi looked extremely tired.

Without him, there have been many floods in the south, hundreds of thousands of displaced people, and there has been a long-term drought in the north.

This was not the most troublesome, as the British Duke Zhang Mao handed over the secret report about the Tatar barbarians to him along with the memorabilia.

At first, he was furious with the Tatar barbarian Qiujin, and after seeing the twists and turns, he was shocked that the young man named Du Shen could come up with such a good plan, and he couldn't help but want to meet this great talent.

But as soon as he thought of the compromise, Du Shen's plan to crown the seven sons of the little Tatar prince Dayan Khan as the king of Tatar, Emperor Hongzhi had a headache.