It was burned cleanly, and all the facilities around the coal mine were left with only some red bricks still standing, and there were only a few tiles left on the red bricks.

Since it has been washed by fire once and there is no fire now, it is naturally safe.

"There's no danger anymore. Let's go down and take a look. We can't see anything here."

Hearing Wang Zheng say that he wanted to go down and take a look, Zhang Zheng was shocked and hurriedly bowed and said, "Sir, no, sir, if you want to know something, just let me go down and check it out. I have made a big mistake and it is not a pity to die. How can I let you take risks again?"

Li Si also said with some concern: "Whatever the master wants to investigate, let me go and take a look. It's hard to say what's going on here now. Even if the fire doesn't burn again, the surrounding mountain walls are exposed a lot. Whether there will be any collapse is a problem."

Wang Zheng shook his head and said, "It's really alright. Let's go down and take a look. Just don't get close to the cliff."

In fact, nothing could be seen below as all the snow and water had frozen. After Wang Zheng walked around for a while, he followed Zhang Zheng's guidance, looked at the mine pit emitting black oil and went back.

Li Si looked at the smoky fire and said with some disdain, "It stinks, and there's a puff of black smoke. It's not suitable for reading. It's not as good as a candle."

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The emotions of the wounded were relatively stable. After all, some of them were from Yuzhou, and they naturally knew the rules of Yuzhou. When encountering such things, Wang Zheng would not ignore them. With them as examples, those Tibetans would not have any problems.

In the end, Wang Zheng still chose to use boiling water, but instead of soaking it, he put the jar directly into the iron pot and boiled it.

The next day, he walked around the jar, thinking about how to refine the petroleum into gasoline or kerosene.

Zhang Zheng thought for a moment and suggested, "Since it evaporates so easily, why don't we boil some water and soak it in it for a while."

Because he was afraid of sparks from the impact, Wang Zheng only brought one steel fiber and the hammer he used was a wooden hammer.

As soon as the channel was opened, oil came out and everyone immediately covered their noses.

Wang Zheng nodded and said, "Hurry up and bring the jar over. This volatile substance should also be a kind of fuel. It's not good to evaporate too much."

Because of the complex composition of petroleum, it does not have a specific freezing point, but it is definitely very low. The freezing point of gasoline is above minus 50 to 60 degrees Celsius.

“Will this be less efficient?”

Li Si smashed it a few times and couldn't help complaining, "This thing doesn't bear much force and will bounce back."

Zhang Zheng nodded, "I will remember your instructions, Master."

"Take your time, each of you can smash it for a while."

"Just smash it slowly, build a new channel, and extract some samples. We have to figure out what it is before we know how to deal with it. Since it can burn, it must be useful. Maybe it can even be a blessing in disguise."

Now that they have received Wang Zheng's personal guarantee, they naturally feel more relieved. As long as the steward does not give up on them, it will be fine. The steward is not short of money.

Wang Zheng nodded and praised, "It's a very good idea, but this thing is much more dangerous than alcohol, so we should also improve the distillation method accordingly. There is only one jar of black oil, so it won't be a big problem. We still have to be cautious."

Wang Zheng consoled him and then said to Zhang Zheng, "Since it is flammable, don't let it see open flames, not even sparks. Don't use iron tools here anymore. Make some wooden tools. Ceramic ones are also fine. This can be made into a rule here. Well, it should be called an imperial decree."

Wang Zheng didn't know whether this was gasoline, kerosene, or diesel, but it should be enough for lighting, so he just called it kerosene for now.

Zhang Zheng suggested: "Sir, I think this thing has many similarities with sake. Both are volatile and flammable. Can we separate it by distillation?"

After the water in the iron pot boiled, clear and pungent oil slowly flowed out of a bamboo pipe in another room.

The stove and chimney were both outside the house, and there was only an iron pot in the room, the edges of which were sealed tightly with mud to ensure that not a single flame would escape.

The jar was a kimchi jar with an edge. After Li Si filled the jar with oil using a wooden spoon, he put on the lid and covered the edge with a circle of snow. That was it.

The boiling water on the plateau may seem to be boiling, but it is actually only about 60 to 70 degrees. If you don't cover the lid when cooking rice, there is no chance of it being cooked.

After being distilled by Wang Zheng, the sake of the Ba people has a head of about 50 to 60 degrees. Not only can it be used for medical sterilization, but it can also be burned. As one of the first batch of students, Zhang Zheng naturally knows about strong liquor.

Although there were enough people, it still took a whole day to reopen the nearly one-meter-wide channel. The diameter was very small, only about one foot square. If the steel fiber was not long enough, it could not be dug so deep. The ice cubes that were dug had to be scooped out with a wooden spoon.

After returning to the city, Wang Zheng visited each room to comfort the wounded and made some promises, guaranteeing that they and their families would receive subsidies according to their circumstances in the future, and that there would also be corresponding compensation this time.

Afterwards, someone brought wooden boards to cover the entrance of the cave and piled some snow on top of it. Wang Zheng and others returned to the city before dark.

He filled a bamboo tube with kerosene, took it to another room, and covered it tightly with a bamboo lid with an iron wick. Wang Zheng waited for the wick to soak for a while, and then lit the wick with a candle.

The next day, Wang Zheng asked Li Si to bring a steel fiber and a big wooden hammer and return to the mine.

Niu Lao San retorted: "I just think it works well, it's brighter than a candle, and it's OK to use it to illuminate at night. This thing is much easier to get than a candle."

There were candles in this era, but they were made of butter, which ordinary people could not afford. Even though the people in Yuzhou were relatively wealthy, they usually only used tung oil or vegetable oil for lighting.

There is an old saying that goes "a lamp is as bright as a bean", which is used to describe vegetable oil lamps. You can imagine how bright they are.

Zhang Zheng finally showed a smile on his face and said to Wang Zheng: "Sir, this oil lamp is very good. The people need such oil lamps."

Wang Zheng nodded and said with a smile, "Indeed, I will leave this place to you in the future."