Seeing Li Xiu talking about the most important role of saltpeter, he suddenly stopped. Li Chengdao, who was itchy, couldn't help but ask: "Sir, what is the most important role of saltpeter?"

"This..." Li Xiu hesitated for a moment, and finally suddenly had an idea, "I won't talk about the most important role of saltpeter. I will give it to you for research as a topic and see who can discover it first!"

The biggest function of saltpeter is naturally to make gunpowder. It is no exaggeration to say that it was the emergence of gunpowder that wars moved from cold weapons to hot weapons, and also laid the foundation for modern wars in later generations. However, Li Xiu was still somewhat doubtful about the emergence of gunpowder.

First, the Tang Dynasty had just stabilized at home and abroad, and there would not be too big wars for the time being, so even if gunpowder appeared, it seemed that it would not be very useful. Second, he was worried that if the formula of gunpowder spreads and even falls into the hands of those with ulterior motives, it might be used by these people, which would cause uncontrollable changes in the originally stable situation of the Tang Dynasty. In addition, he did not want to bear too much credit to avoid being targeted by Li Yuan, so it would be better not to appear for the time being.

"Li Jijiu, can this method of making ice in saltpeter be promoted? This will allow the people of my Tang Dynasty to eat ice food in the scorching heat?" Princess Pingyang said excitedly at this time. No wonder Li Xiu said just now that he could do as much ice as possible. With a method to make ice, I am afraid that there will be no need to worry about not enough ice in the future.

"Haha, it's just a small path, and it's nothing to promote it. But in this way, the price of saltpeter will probably soar, so the princess will buy more saltpeter in the past few days, otherwise it will be difficult to buy in the future." Li Xiu smiled indifferently. He is not short of money, and making saltpeter ice can improve people's quality of life, so he naturally won't stop it.

"This is a problem. The weather is so hot now, so the amount of saltpeter must be very large. Li Jijiu must also need it at home, and there is still a summer to go through. It seems that you have to buy more." Princess Pingyang couldn't help but say to herself when she heard this. Saltpeter was only used for dyeing cloth and treating diseases, which made its yield not high. Now that the effect of ice making has been discovered, the price will definitely soar. I am afraid that even if I have money, I will not be able to buy it.

"You don't have to buy too much. Salter can actually be reused. For example, the ice made of saltpeter in front of you can dry it or boil it again after the ice melts, and you can get saltpeter again." Li Xiu smiled again and said with a smile on his lips and said.

"That's great. In this way, the amount of saltpeter will be greatly reduced, and ordinary people should be able to afford it!" Princess Pingyang couldn't help but shout happily when she heard this. She even began to think about taking out all the ice in the ice cellar at home and giving it to the servants.

"Brother, the basin is completely frozen. Can it be made into ice food?" At this time, Qi Niang blinked her big eyes and asked Li Xiu. She had been staring at the ice surface since just now, and her mind was fantasizing about the scene where she had not lacked ice food for the whole summer.

"Ice with saltpeter added inside is not eaten. If you want to eat clean ice, you should put it in a small basin in this large basin and put it clean water in it. When the water inside freezes, you can eat it." Li Xiu shook his head and smiled when he heard Qi Niang's words.

"Oh~" Qi Niang said disappointed when she heard this. Actually, she really wanted to taste what the ice made by her brother was like?

Seeing Qi Niang's disappointed look, Li Xiu couldn't help but smile. He asked her to wait for a while, then took some ice chips brought by Li Chengdao, added cream, and sprinkled with some chopped fruit particles. As a result, a portion of fruit ice cream that was almost no different from later generations was ready.

When Li Xiu brought the ice cream to the living room, Princess Pingyang and the others all lit up their eyes. After tasting it, they praised it. Even Li Chengdao, who doesn't like sweets, ate a big bowl. He also asked Li Xiu for the method of making it, saying that he would make it for his younger brothers and sisters after he went back.

The weather is hot and it is really not suitable to go out for activities, so Li Xiu and the others stayed in the living room all day long. The ice in the ice basin was replaced one piece after another, and the cart of ice brought by Li Chengdao was only enough for one day. As for the ice brought by Princess Pingyang, it was really divided by Li Xiu. All the servants in the family were assigned a large piece of ice, so that they would no longer have to worry about being so hot that they couldn't sleep. This treatment was very jealous of the helmet beside Princess Pingyang, but they would also live such a cool life after tomorrow.

That night, Li Xiu and everyone in the family had a rare good night's sleep, but that night, a cavalry rushed from south to north and towards Chang'an. The leader was Li Shimin. Because the war in Tuyuhun was settled, there were naturally other people to deal with it next, so Li Shimin rushed back to Chang'an. The reason why he rushed to the evening was naturally to avoid the hot summer during the day.

Seeing Chang'an right in front of him, Li Shimin also showed a smile on his face. During this period, he fought hard on Tuyuhun and finally defeated the other party. This was also the second time that he defeated Tuyuhun after Yang Guang. You must know that Tuyuhun's strength is no worse than Goguryeo in the Northeast. Such great military achievements are enough to make Li Shimin beat the game, proving that his military talent is by no means comparable to that of his elder brother Li Jiancheng.

However, although this battle proved Li Shimin's military talent, he could not stay outside for too long. After all, if he left Chang'an for a long time, God knew what would happen, so as soon as the war ended, Li Shimin immediately rushed back.

"Your Highness, we are less than ten miles away from Chang'an. Should we take a break first and then send someone to inform the city so that your Majesty can arrange someone to greet you!" At this time, Li Shimin rushed out behind him and walked alongside him. This person was Sun Wuji, the chief strategist whom Li Shimin relied most.

"No need, let's go directly to the city under Chang'an City and then ask to open the city gate to enter the palace. I want to see my father earlier and report to him about the war in Tuyuhun to him!" Li Shimin said excitedly. At this time, he was eager to see his father more than ever.

Seeing Li Shimin's excited look, Changsun Wuji couldn't help but sigh inwardly. He was probably the only one in this world who could understand Li Shimin's thoughts. Just a while ago, they suddenly received news from the court. His Majesty suddenly increased the number of memorials he had reviewed. As a result, the power in the prince's hands also decreased a little, which made Li Shimin think that his military achievements in Tuyuhun played a role, which made Li Yuan begin to favor him, so he was eager to enter the palace.

However, compared to Li Shimin's excitement, Changsun Wuji, as an outsider, felt that this was a bit strange, and it might not be a signal that His Majesty began to favor Li Shimin. For this reason, he once advised Li Shimin not to be happy too early to avoid having a happy moment. Unfortunately, Li Shimin, who was full of joy, couldn't listen at all, which made Changsun Wuji very helpless.

In fact, Changsun Wuji's intuition was correct, but he and Li Shimin would never dream of the reason why Li Yuan increased the number of memorials to review was just because Li Xiu gave him a pair of reading glasses, which relieved his eye disease. This made Li Yuan feel like he was much younger, so he took back some power.

The ten-mile journey was coming in a flash. When Li Shimin and his group came to the city gate, a trace of white fish appeared in the east. It was not yet time to open the city gate. However, after Li Shimin revealed his identity, the guards at the city gate naturally did not dare to neglect them. They immediately opened the city gate and let them in. Then Li Shimin did not even take off his armor and rushed to the palace.

Li Yuan was in a good mood during this period. Since Princess Pingyang gave him reading glasses, she no longer had to worry about not being able to see the memorial clearly. In addition, the concubines he loved in the palace were pregnant at the same time. It is estimated that by the spring next year, he will have more princes or princesses.

When he was in a good mood, he felt different. These days, Li Yuan got up early every day and rode his old war horse for a few laps. This war horse has followed him since he started the army in Taiyuan. He would ride it every time he went to the battlefield. However, after becoming the emperor, he and it had no chance to go to the battlefield again. Moreover, the horse is old and cannot go to the battlefield at all. At most, he usually trots a few laps.

But just as Li Yuan had just got off the horse and took a towel to wipe his face, he suddenly saw the eunuch trot forward and report: "Report to Your Majesty, Your Highness, the King of Qin, is back and is waiting in Liangyi Hall now!"

When Li Yuan heard that his second son had returned so soon, he was stunned. Then he immediately asked someone to set up the Liangyi Hall. When he walked into the hall, he saw Li Shimin wearing armor standing in the hall. When he saw him coming in, he immediately bowed and said, "Son Master, please see the father!"

"Haha, Erlang, you don't have to be too polite. You did a good job in Tuyuhun this time. The civil and military officials in the court praised you for your good work!" Li Yuan laughed loudly when he saw Li Shimin. The most proud thing in his life was to have two capable sons, but the same is true for the most troublesome thing, because there is only one seat, and sometimes he doesn't even know how to choose?

"Thank you, my father, for your praise. My son has just done his duties!" Li Shimin was modest, but he couldn't help but smile, and he received his father's praise. He thought of his father's previous revocation of the power from his elder brother, which made him more certain that his weight in his father's heart may have exceeded that of his elder brother.

Next, Li Shimin began to report to Li Yuan about the war in Tuyuhun, and took out a memorial to hand it over, which recorded the casualties of the battle, the consumption of materials, etc. Li Yuan took the memorial habitually and picked up the glasses next to him and put them on, then read the memorial while listening to Li Shimin's report.

Li Shimin was very surprised when he saw the glasses on Li Yuan's face. He couldn't help asking: "Father, what are you wearing on your face?"

"Haha, this is called reading glasses. It was given to me by your third sister. You also know that you have eye disease for your father. In the past, you had difficulty reading memorials, but this reading glasses relieved your eye disease for your father. Now you no longer have to worry about not being able to see the words on the memorials." Li Yuan said happily.

When Li Shimin heard this, he felt like he was struck by lightning. The expression on his face suddenly became solidified, as if he understood something. Moreover, Li Yuan said that the glasses were given to him by Princess Pingyang, which made him immediately think of someone. He couldn't help but grit his teeth in his heart and said intently: "Li Xiu, you bastard!" (~^~)
Chapter completed!