Speaking of the production of nitrocellulose, sulfuric acid, the Northern Army originally had some production capacity, mainly for testing and battery and drug manufacturing, but the production of nitric acid has always been laboratory level.

The laboratory production of nitric acid is very simple, the saltpeter and sulfuric acid are reacted and distilled, this method is called dry distillation, which was first discovered by alchemists in the Middle East in the eighth century, but to be industrial-grade, the most common in later generations is ammonia oxidation production, which needs to be made by compressor first.

If he could make that thing, the first thing Ma Qiang would do was definitely air conditioning!

The dry distillation method, dilute nitric acid is OK, concentrated nitric acid needs high-purity saltpeter, theoretically speaking, it can produce more than 96% concentration of concentrated nitric acid, but such saltpeter... Only Chile has it.

Ma Qiang thought about it and decided to use the advantages of his enough generators to make nitric acid by the arc method.

The arc method, that is, simulating nature's lightning, makes nitric oxide from nitrogen and oxygen in the air, and then combines nitric oxide with oxygen in the air to form nitrogen dioxide, which can be dissolved in water to form nitric acid.

It can be said that because the air is inexhaustible, this method of making nitric acid is also unlimited.

The only problem is that the concentration is not enough, and it is also necessary to use sulfuric acid to remove water and thicken.

Ma Qiang wrote and painted, which can be regarded as setting the direction of the renewal of firearms in the next few years.

By the time Ma Qiang finished drawing various design drawings, the sun was about to set.

The afterglow of the setting sun shone on the battlefield, making the purple-black blood clots on the battlefield turn red again.

"Ming Gong, Yan Liang has withdrawn from the army, and their offensive strength today is not as strong as yesterday!"

Xian Yufu stepped forward to report the battle situation to Ma Qiang, and Ma Qiang put away the drawings, and these papers were already worth more than gold after Ma Qiang wrote them.

Well! If you think about it carefully, your words are much more valuable than Zhang Zhi and Zhang Chang.

Zhang Zhi, who should have passed away, was still alive and well in the plain at this time, and it is said that he also dug a pond for washing pens and studied italic calligraphy.

These literary and artistic celebrities are also thieves who like to go to extremes, engaging in cursive writing that no one can recognize, and regular script that is more upright than a soldier.

"It seems that Yuan Jun is bent on breaking the wall with gunpowder, go, go down and ask Wang Xiu, if you heard anything."

Under the city wall, urns were half-buried in the ground, and then people with sensitive ears stuck to the urns to listen to the sound, in order to find the direction of Yuan Jun's tunnel.

"Wang Junshou, what have you discovered?"

Wang Xiu arched his hand and said, "It's too noisy during the day, so I can only hope to find something out at night." ”

"Where's the hot air balloon?" Ma Qiang looked at Huang Xu, who had just walked over, Huang Xu shook his head and said, "Chun Yudao's military camp is densely covered with flags, and the tents are well covered, although there are traces of excavation, but I can't find the direction at all." ”

"Also, I've heard the name of the digger army, it won't be so simple, Wang Junshou, pass the order, whoever is the first to discover the direction of the tunnel will be rewarded with ten thousand dollars!"

Ma Qiang can only give a heavy reward now, no matter how powerful he is, he can't make an underground detector.

And so, three days passed.

"Yuan Tan actually has a bit of a strategy, using a deceit to let Hua Xiong venture into the siege, if Yan Rou hadn't arrived, Commander Hua would have folded in Zhongshan!

I didn't see it before. Ma Qiang was eating pancakes while looking at the bulletin sent from Guangzong.

"Yuan Tan's lower officials have also seen it, but they have a plan."

Ma Qiang listened to Han Fu's words, nodded, and remembered that among the four states occupied by Yuan Shao in history, Qingzhou was led by Yuan Tan himself, and it seemed that he was indeed not an ordinary gentleman, and he was assisted by Guo Tu and others.

Speaking of Yuan Shao, it is also luck, if these strategists get together, it will be absolutely bad, and now Yuan Shao has used them separately, which has brought the abilities of these strategists to the extreme.

There are still too few strategists in their hands, although many qualified grass-roots and even middle-level officials have been trained from the Qianshou, but military strategy relies more on experience and talent, and to some extent, talent is more important than experience.

It's a pity that Tian Feng is unwilling to help himself, otherwise it would be a big help.

After this fight, you have to go south quickly, whether it is Sima Yi or Zhuge Liang, you have to catch one first.

Ma Qiang was thinking about something, and before he knew it, he finished eating the pancakes, he put down the report, wiped his hands, looked at Han Fu and said, "How did Han Envoy Jun use it?" Let's go see the people and the wounded soldiers. ”

Han Fu immediately gulped down the remaining pancakes, and then followed Ma Qiang in the city.

The autumn harvest has passed, the weather is getting colder, Ma Qiang looked at the people living in the temporary tents on the streets and squares in the city, and saw that although more than ten days have passed, the mood of the people is still stable, although there is not much to eat, but there is thick porridge and batter, with salted fish, it is not bad.

"Report!!"

When Ma Qiang was inquiring about the situation at the door of a common household, a shout came from behind him, and a sergeant rushed to Ma Qiang and said, "Ming Gong, Wang Junshou said that he found the direction of Yuan Jun's tunnel!" ”

"Let's go!"

Ma Qiang came to the city wall with a large group of people, Wang Xiu threw himself on the ground and was listening to the urn, seeing Ma Qiang coming, he hurriedly stood up, and he didn't care about wiping the dust on his face and said, "Ming Gong, it's coming in this direction!" However, the voice was very faint, and it was impossible to hear without careful listening, but it had been confirmed by a few old scouts. ”

Ma Qiang didn't care about the soil, he lay on the urn and listened for a while, and sure enough, he heard the rustling sound of digging, and his five senses were better than ordinary people, so he heard it obviously.

"Good!" Ma Qiang looked around and asked, "Who found out first?" ”

"It's this little man!"

A black-skinned teenager was pushed out, and he looked at Ma Qiang, his face a little red with excitement.

"Yes, reward! If you are willing to join the army in the future, you can be promoted to the team rate! ”

Many people looked at the teenager with envy.

"Wang Xiu, you immediately organize manpower and materials to prepare to build the urn city!"

"No!"

Everyone was excited, once the urn city was completed, the victory that Yuan Jun thought he had won would surely turn into a big defeat.

Time passed day by day, and in the blink of an eye, it was the eighth day.

In the past few days, troops have continued to come out of the Taihang Mountains and join the camp of Yuan's army.

And Fang Yue in Hanoi also raised troops, and Sima Ju and Guan Hai had already sent a telegram asking if they wanted to intercept it.

At the same time, a capable army, under the banner of koji, appeared in the north.

Yuan Shao's chess pieces have all arrived, and the decisive battle is just around the corner.

Ma Qiang was inspecting the three-meter-high urn city at this time.

Don't think three meters is short, there is a three-meter-deep and two-meter-wide trench in front of this urn city.

The reason why there is such a trench is, on the one hand, that the construction of the urn city requires earth and stone, and on the other hand, it is also afraid that Yuan Jun will dig under the urn city.

Once that situation occurs, Ma Qiang can't even think about that scene.