Ordinary chestnut rice porridge, light boiled wild vegetables. The taste is not wonderful, but looking at Jiang Ruoniang who is smiling from ear to ear, Jiang Wei feels very happy to eat.

Until it was already late at night, Jiang Wei stroked Ruoniang's hair, looked at her sleeping appearance with a smile in the faint moonlight, considered the future, and thought about how to give Ruoniang good food and drink, no longer have to go to farming, no longer have to be tired.

But his body is still very weak, and he may not be well for ten days and a half months. As a modern mindset, he really didn't know how to survive in ancient times.

What would he be if asked? This starts when I was a student. Well, since he came into contact with chemistry, Jiang Wei has been very interested in chemistry, because chemistry is very interesting, and it once reached the level of obsession. So, when choosing a university major, he chose to major in engineering energy and power engineering without hesitation, and chose chemistry.

Well, because my parents said it would be easier to find a job after graduation.

But now, in this era, because the infrastructure is almost zero, his hands-on ability is only chemistry.

Other than that, he has no skills.

Jiang Wei thought about it seriously, but it was not correct, because he felt that many life skills were neglected by himself.

Like cooking? Although he has barely been able to cook at the level of cooking, he really does not have the confidence to use cooking to feed his brother and sister.

At the fifth watch, Jiang Wei dragged his weak body out of the house and picked up a branch by the moonlight.

If it comes to manual labor or something, he naturally can't make Ruoniang live happily, but the knowledge he has is different from anyone now.

That's chemistry.

In chemistry, in ancient times, it was simple to make money, and that chemical substance was almost ready to come out.

KNO₃

That is, saltpeter.

First, consider the amount of heat that needs to be released when the water freezes in the summer. Jiang Wei doesn't understand the indoor temperature during the day, so let's assume that the indoor temperature is 30 °C, and the ordinary water temperature should be around 25 °C at a standard atmospheric pressure, and the water freezing can be divided into two parts: water dropping from 25 °C to 0 °C and then freezing and releasing heat from 0 °C.

Jiang Wei picked up the branch and began to analyze it on the ground.

According to Q=cmt, the specific heat capacity of water is 4.2×10³J/(kg·°C), take one liter of water, that is, one kilogram of water. Then t 25→0 °C releases 105 kJ heat.

That is to say, at 0°C, one gram of water freezes and releases 80 calories, or 334.8 joules?

If only 334J is taken, then 334KJ will be released for one kilogram. Therefore, it is estimated that water will release 439KJ of heat from freezing at room temperature in summer.

Next consider saltpeter, the main component of saltpeter, potassium nitrate, KNO₃. The heat of dissolution of KNO₃ is 34.89 KJ/mol. At 20 °C, the solubility of KNO₃ is about 31.6g, and at 25 °C, the solubility is 35g, and the molar mass of potassium nitrate is 101g/mol.

After calculation, it can be obtained to absorb 439kJ of calories? Well, it takes 1270.8g of saltpeter, and the density of KNO₃ is 2.109g/cm³. That is, it should be 602.57 cm³.

In other words, 1000 cm³ of water needs to dissolve 602.57 cm³ of potassium nitrate to make ice?

This is still not considering the purity of saltpeter, and the calculation shows that it is impossible to make popsicles in large quantities, but there is no problem in making cold soup porridge products. And according to the characteristics of saltpeter, it can also be used again and again, which is a great cost saving.

At this time, the sky was not yet fully bright, and the villagers left the gentle harbor in an endless stream in the still gray sky with the coolness of the early morning.

At this time, Ruoniang sat up in a daze, rubbing her eyes that had not yet opened.

"Good morning!"

Suddenly, the sound made Ruoniang wake up completely, and she stared at Jiang Wei blankly for nearly two minutes, and her brain seemed to come back to her senses and threw herself into her weak arms.

"Brother!"

Jiang Wei smiled and rubbed his little head,

"Ruoniang doesn't have to get up so early in the future, because there is a brother here, you can sleep as long as you want."

Listening to the gentle voice, Ruoniang leaned her little head and looked up at the sky outside, showing hesitation,

"But my brother is still very weak, and there is not much chestnut rice left at home, and he has to pick wild vegetables, otherwise there will be no vegetables to eat."

"Na! Ruoniang doesn't believe in her brother? ”

Ruoniang shook her little head, and said in her eyes, still with lingering doubts,

"Ruoniang, you do my brother a favor."

"Brother, please speak."

"You go and tell those uncles and aunts, and say, brother, I have come to share the way to obtain wealth in order to thank you for your continued care."

"Wealth... Rich? What is it? ”

Ruoniang struggled to read words she had never heard before, confused.

"Wealth..."

Jiang Wei thought about it, and didn't know how to explain it for a while,

"Hmm... It's copper, no, what should the money of the Tang Dynasty be called? …… Yes, it's a copper coin, so it means that my brother got heaven... The teachings of the immortals, so they knew how to get a lot of copper coins. ”

Jiang Wei smiled awkwardly, he didn't want to lie, but the people of the Tang Dynasty were ignorant at this time, and in their opinion, this knowledge was no different from mythology, and it would be better to use immortals and the like to save some unnecessary trouble, after all, this can't be explained at all, do you need to make a formula to tell them the principle?

Ruoniang was stunned by these words, she looked up her little head with a look of admiration, nodded violently, quickly put on her coat, and quickly got out of bed and went out, leaving only a voice from afar.

"Brother, wait for me to come back~"

Half an hour later, the villagers came to the open space in front of the thatched hut one after another, and saw a young man with white hair sitting cross-legged on a stone squat. He was dressed in white, and his indifferent appearance of closing his eyes and recuperating was a little fairy in the eyes of these villagers.

It's not that Jiang Wei is pretending, it's just that he is too sleepy, and when he opens his eyes, he sees Ruoniang standing at the front with an adoring face.

Jiang Wei beckoned and asked Ruoniang to open a basin of cold well water and wash her face, which suppressed her sleepiness. Looking at the nearly 100 villagers, he said indifferently,

"Ahem~ Everyone, thank you for your care of your brothers and sisters during this time. Without your help, I can't imagine if my brother and sister would have survived. ”

"During the period when I was asleep, I Jiang Wei was fortunate to meet my master in a dream, and he taught me the true meaning of this world in my dreams and made me understand the essence of this world."

Looking at the dazed villagers, Jiang Wei couldn't stop, coughed, thought about it and continued to speak,

"In ancient times, immortals still existed on this land, and they recruited immortals and taught people immortal arts. And what is immortality? Immortal art is a kind of knowledge, which uses matter to generate power and produce miracles, which is immortal. Although not everyone can learn complex and powerful immortal arts, simple and ordinary immortal arts can be learned by everyone. Today, I have called you here to teach you one of these very simple immortal arts. In this way, you will be able to learn this immortal art and earn more copper coins through this immortal art. This is also my gratitude to everyone. ”

The villagers of Yunling Village were dumbfounded when they heard this, and couldn't help but swallow a mouthful of saliva, everyone can learn immortal arts? Really?

At this moment, a villager wearing a patched Confucian robe stepped forward.

The new cute trembling begging collection, begging for recommendation.