Arthur didn''t attend the serfs'' welcome meeting because he had more important things to do.


    Over the past few months, he has been sending people to look for caves with appropriate conditions in the Qingfeng mountains. Naturally, he intends to make nitrate instead of being a caveman.


    To be exact, I intend to boil cave nitrate!


    Nitrate, that is, potassium nitrate, commonly known as soil nitrate, fire nitrate, salt nitrate, etc.


    In China, nitrate making began more than 2000 years ago, and until the 1960s and 1970s, there were people like nitrate makers in many rural areas of China.


    The most well-known use of nitrate is to produce black powder and fireworks.


    Black powder is one of the four great inventions of China. The formula is well known: one nitrate, two sulfur and three charcoal.


    This is the chemistry knowledge of junior middle school.


    However, in addition to making black powder and producing explosives and firecrackers, nitrate is actually quite widely used.


    For example, he can also be used as a drug, called mirabilite. Arthur vaguely remembers that the chemistry teacher in junior high school said it can cure abdominal distension, dry stool and no feces.


    In addition to medicine, nitrate can also be used in industrial production, such as dyes, glass, matches and kneading fur.


    In addition to industrial use, nitrate can also be used for food processing, such as hair color agent or marinated meat products, which can not only improve color and flavor, but also prevent corruption. Of course, this stuff is poisonous. When it is used as food additive, it must be strictly controlled.


    In addition to the above, nitrate is most widely used in agriculture. It is a chlorine free nitrogen potassium compound fertilizer with high solubility, can be quickly absorbed by crops, and has no chemical residues, which will not harden the land.


    This is the main purpose of Arthur''s boiling cave nitrate.


    Agriculture is always the most basic and important industry. It not only provides people with survival security, but also the primary condition for all production.


    Although lingfengbao has achieved self-sufficiency in grain and even some surplus grain after some agricultural reforms, this grain is far from enough if it wants to develop some light industry.


    For example, Arthur has been looking forward to the wine industry.


    Therefore, while expanding the area of cultivated land, we should also strive to increase grain production.


    The main reason why China''s grain output is several times that of the world is the use of seeds and chemical fertilizers.


    Seeds


    So we have to work hard on chemical fertilizer.


    After months of searching, nearly 20 caves suitable for boiling cave nitrate were found in the Qingfeng mountains.


    Most of these caves are small caves less than half a mile deep. Although these small caves can also be used to boil cave nitrate, the output will not be too high.


    Fortunately, in addition to these small caves, there are six larger caves, including two caves. The people in charge of exploring the caves have not yet figured out how deep they are. They only said that they could not reach the end after burning two torches.


    Cave nitrate is naturally boiled in the cave.


    After finding these two large caves, Arthur named them No. 1 and No. 2. Then he asked people to cut wood to open the way, and vigorously carried out the nitrate making movement in No. 1 cave.


    To boil tunnel nitrate, first dig nitrate pit, also known as nitrate leaching pool. As long as it is easy to operate, the larger the pit, the better.


    Because nitrate boiling is a cumbersome process, the larger the nitrate pit is dug, the more output can be obtained in a single cumbersome nitrate making process.


    Now the nitrate pit in front of Arthur is a nitrate pit with a diameter of more than three meters and a depth of two meters.


    After digging the pit, then tamp the soil on the pit wall and bottom. As for the degree of tamping, Arthur''s requirements for the nitrate workers are: tamp until you can''t move!


    After the nitrate pit is ready, a small hole shall be pierced at the bottom of the pit, and a small pit shall be excavated below. A container shall be placed in the pit to receive the nitrate water seeping from above.


    It takes a lot of effort to build such a funnel-shaped nitrate pit. It took more than a month for 70 or 80 nitrate workers to build 11 such pits on the right side of the cave.


    After the preparation of nitrate pit, nitrate soil is prepared.


    Nitrate soil exists in many places, such as thatched houses, fences for pigs, cattle, sheep and livestock, old corners of courtyards, caves and other places that are not easy to be washed by water.


    The amount of nitrate soil in thatched cottages and other places is too small and inconvenient to collect, but Arthur has also asked farmers to collect and store it, and Lingfeng castle will agree to purchase it every year. It can also be regarded as generating income for farmers.


    Cave boiling nitrate, the main source of nitrate soil, is naturally the nitrate soil in the cave.


    According to Arthur''s memory, the best nitrate soil will taste spicy in his mouth, and the worst nitrate soil will be slightly sweet.


    This is what he heard from the female guide when he visited a cave in his last life. He also tasted some nitrate soil at that time.


    After Arthur''s repeated attempts, the conclusion is that the excavation depth of nitrate soil in tunnel 1 can reach at least half a meter.


    Before pouring the nitrate soil into the nitrate pit, a layer of hay needs to be paved at the bottom of the pit. After pouring the nitrate soil, the nitrate soil should be continuously compacted. Similarly, the tighter the better.


    Because Arthur, who is rich and powerful, sits in an iron mine, directly let the forging factory build a huge iron funnel that can directly cover the nitrate pit.


    The purpose of this is to prevent the water from leaking around when spraying nitrate, and to facilitate reuse.


    After filling the nitrate soil, start to add water to the pool, preferably the dead water in the cave.


    The process of water infiltration from top to bottom is nitrate leaching.


    Because it was the first time to make nitrate, Arthur only used one nitrate pit for the purpose of experiment.


    The nitrate pit where nitrate was being poured began to inject water four days ago. Because the nitrate soil was compacted very tightly, no nitrate water leaked into the big wooden basin below until early this morning.


    With the continuous exudation of nitrate water, Thorne and others couldn''t help sniffing their noses. They found that the strange smell in the air seemed to be getting stronger and stronger.


    Close to Arthur, Thorne said anxiously, "Sir, it tastes strange. It smells more choking than the urine of cattle and horses. Is there something wrong?"


    Arthur, who sat waiting, smiled. The choking smell in the air was really bad, but he enjoyed it now.


    "Don''t worry, that''s the smell!" he said excitedly. "And the more choking, the better. It shows that the concentration of nitrate water we get is high enough!"


    At this point in the experiment, Arthur''s heart was more than half secure. As long as a high concentration of nitrate water can be obtained, the subsequent process is nothing more than a distillation and purification step.


    Even if there is no way to obtain high-purity potassium nitrate, it is more than enough to fertilize crops.


    It was estimated that the exudation of nitrate water was enough. After an experiment, Arthur asked people to pour it into a big black pot on the left side of the cave, light a fire and start boiling.


    ……