Twilight Town has been dealing with so many issues lately that Todd feels a little overwhelmed.

He compiled the information at hand and summed up the three most urgent things.

1. Find a way to improve your relationship with the Valkyrie and gain access to the "Sacred Forest" to investigate the truth about the transformation of xenos into ordinary people.

Second, find a way to find a new way to manufacture saltpeter and restore the production line of explosives.

Third, find a solution to the possible food crisis as soon as possible.

Thinking about and comparing the above three items, Todd decided to prioritize the second thing - saltpeter production.

Here's why:

1. If you want to improve your relationship with the Valkyrie in order to enter the "Sacred Land", it is not something that can be done overnight, and you can only advance this matter step by step.

Second, the development of Duxi Town, whether it is a municipal road or a large construction project, requires a large amount of money. Where does the money come from? Tax collection and investment income simply cannot fill these holes. The only way is to plunder the property of the surrounding noble fiefs through constant wars to supplement the development needs of the town. And against the towering castles and thick walls of the aristocracy, explosives are indeed an indispensable helper. Therefore, finding new ways to manufacture saltpeter should be a top priority.

Third, as for the food crisis, Todd has some ideas. The North Island fleet went south to sell seafood, and when it returned to the sea, it was entrusted to purchase grain from the south, and then sold it to the town of Twilight to solve the food crisis, and as for the money to buy grain, war plunder, and trade income, it could fully cover the expenditure.

Since it has been decided to make nitrate in the first place, the question now is, how to get it?

Todd recalled the time-traveling classes and movies he had seen in his previous life, and there were many works that described the flow of science and technology, and there were some introductions to the acquisition of nitrate.

First, the Traverser explores and mines natural nitrate. With a little thought, Todd defines this approach as nonsense. Natural albite saltpeter and potash saltpeter are very rare in nature. For example, in the vast country where Todd traveled, there is only one area called Turpan in Xinjiang, which has sodium saltpeter mines, and there is no trace of saltpeter mines in other areas. (There is a lot of history, and the miscanthus in the "Compendium of Materia Medica" is considered to be saltpeter, and it is believed that saltpeter ore is common.) In fact, in ancient times, miscanthus nitrate referred to two substances, namely sodium sulfate and potassium nitrate)

Secondly, the soil is collected from earthen walls, saline-alkali ground, latrines and other places to obtain soil nitrate. This practice is also the main way to obtain nitrate soil in technologically backward areas. However, there are many problems with this method: first, this kind of "sweeping nitrate" collection method has geographical limitations, and is generally more suitable for dry areas or cold areas; second, after collecting once, it takes a long time to generate nitrate again; third, the obtained nitrate has more impurities, and the nitrate content is very low, which affects the effectiveness of gunpowder.

Having rejected both of these options, Todd, as a teacher of biochemistry, eventually planned to use microbial methods to make saltpeter.

There is a class of bacteria in nature, known as nitrifying bacteria, which is an aerobic group of bacteria that includes two completely different genera: nitrosomonas and nitrobacter.

Nitrous bacteria are commonly referred to as the "oxidizers of ammonium" because the only food source they support is ammonium. Ammonium is a cation (NH4+) formed by ammonia (NH3) dissolved in water, which is mainly produced by decaying organic matter, because it chemically behaves like a metal ion, so it is named "ammonium". In the presence of air, ammonium can be absorbed and utilized by nitrite bacteria. They oxidize their hydrogen atoms into water and replace them with oxygen, so ammonium becomes water and nitrogen oxide dissolved in water, the latter is called "nitrous acid", and its reaction formula is as follows: 2NH3+3O2→2HNO2+2H2O+158kcal

Nitric acid bacteria are commonly referred to as the "oxidizers of nitrous acid" because the main food source for their life is nitrite and nitric acid is produced as the end product of the nitrogen cycle, and its reaction formula is as follows: HNO2 +1/2 O2 = HNO3, -⊿G = 18kcal

To put it simply, the decay produces ammonium, which is oxidized to nitrite by nitrite bacteria, and then the nitrite acid is oxidized to nitric acid by nitric acid bacteria, and this reaction is called "nitrification reaction". This reaction is carried out by two different bacteria.

After talking about the principle of microorganisms and chemical reactions, the next thing Todd has to do is to formulate the specific process of microbial nitrate production.

In the first step, a test plot is prepared as a petri dish to propagate nitrite bacteria and nitric acid bacteria.

The second step is to prepare raw materials for microbial nitrate, prepare a large amount of human and animal feces or nitrogen-rich rotten fish and shrimp, and the static reaction will produce a large amount of ammonium.

The third step is to build a nitrate pond, and the bottom layer is sealed with cement. The inside of the pond is covered with a mixture of bulky clay and fine sand, and some slightly alkaline ash is appropriately mixed in. (Because nitrifying bacteria cannot survive in acidic environments), transplant the bacterial culture soil in the test field and loosen the soil regularly to ensure soil air permeability.

The fourth step is to build a roof, and can not transmit light, nitrite bacteria are very sensitive to the visible light of ultraviolet rays, and ultraviolet rays in the sunlight will cause fatal damage to bacteria.

The fifth step is to adjust the temperature in the pool in a timely manner according to the temperature of the external environment to ensure that the room temperature is about 25 degrees, because if the temperature is too high or too low, it will affect the cell division and reproduction of the nitrifying bacteria population.

In the sixth step, the raw materials (rotten fish, shrimp, human and animal feces, etc.) are diluted with water and sprayed in the bulky clay fine sand through a special pipe.

The seventh step is to regularly sprinkle some plant ash (mainly potassium carbonate, and a small amount of potassium sulfate) on the bulky soil, so that potassium nitrate can be directly obtained after scraping the nitrate soil at the end.

Finally, the potassium nitrate obtained, using the difference in the solubility of various salts, and then controlling the temperature and concentration, so that the potassium nitrate crystallizes out of the mixture, and the high-quality saltpeter used to make gunpowder is obtained.

After nearly a month of busyness, the first products of microbial nitrate production were sent to the biochemical plant in Richel, the production line of explosives was restarted, and a steady stream of explosive packs were delivered to the troops in Cumberland.

With explosives and xenomorphs, the Knights of Twilight swept through the entire eastern region of the Silver Ring Kingdom, and the castles of more than 70 nobles, large and small, were blown up in tears, and the defenders and mercenaries were as weak as children in front of the xenomorph soldiers, and countless treasures were transported into Twilight Town.

The Church of the Heavenly Father, the Holy Acropolis, the Silver Ring City, and the Barbarians, these four forces, have also gradually shifted their attention to this emerging and rising Knights.

One day in early July 1171 A.D., Tristan walked into the Order's headquarters and knocked on the door to Todd's room with a letter.

"Commander-in-chief, I have come to resign, and I will return to the capital of the Papal States tomorrow. ”

Todd looked up from the pile of papers, looked at the church deacon who had lived in Twilight for more than half a year, and asked, "Why is there such a hurry tomorrow?"

Tristan said solemnly: "There are two things. First, the First Inquisition had just announced the verdict of the Scourge of Truth a week earlier, and the teachers and students of the Royal Academy had been found guilty. Starting next month, they will be burned at the stake in batches. Second, the Church sent an official letter to the Knights of the Twilight......"

The deacon placed the letterhead in his hand on Todd's desk, and the latter opened it and looked at it again, his brow furrowing more and more.

In the official document, the Church asked the Knights of the Twilight West to capture the North Quarry, a heavily guarded military stronghold of the Silver Ring Kingdom, by the end of September. If the mission is completed, in return, the Church will recognize Todd's ownership of the captured lands and agree to the Knights of the Twilight West to establish a secular kingdom.