The ancients have mastered the technology of saltpeter ice making, so why use the freezer to store ice?

At the end of the Tang Dynasty, people mined saltpeter when producing gunpowder. Nitrate is a white bitter crystal. In the crisp autumn season, it usually precipitates in the form of shells or salt flowers, covering the ground and walls. The chemical name of saltpeter is calcium nitrate. When it is dissolved in water, it will absorb heat and lower the temperature. People use this characteristic of saltpeter to make ice cubes. But in this case, most ancient people still used ice chambers to store ice cubes, rather than directly using saltpeter to make ice. This is because saltpeter can make ice, but it is not an easy task.

First of all, saltpeter was originally refined by the ancient alchemist, but at that time, saltpeter was difficult to obtain and the quantity was very small. You need to find clods containing nitrate, put them in barrels and soak them in water. After filtration, the filtrate was boiled or dried in the sun to obtain saltpetre crystals, which were originally used as medicines. To make ice with saltpeter, you need to pour some water into a big basin, then put a small basin, then pour another basin of water into the small basin, and then pour saltpeter into the big basin. The water in the small basin will turn into ice. We need a lot of saltpeter here, but we can only get a small basin of ice, which is too expensive and complicated.

Although at the end of the Tang Dynasty, people mined a large number of saltpeter mines when producing gunpowder, we know that in ancient times, gunpowder and mining were not things that ordinary people could do, and the government was generally responsible. The productivity in ancient times was very low, and even if a large number of ores were found, it was difficult to mine. Even using saltpeter to make ice is not affordable for ordinary people.

Moreover, before mastering the ice-making technology, ice storage in the ice room has a history of thousands of years and has become an ancient traditional custom for a long time. It's hot in summer and freezing in winter in northern China, so it's a custom to store ice cubes in the freezer in winter for the next summer. There were officials in charge of the ice room in the ancient court, and ice cubes? Ice well? . Every winter comes, the ancients will hold a grand ice-cutting and ice-storing ceremony, which is quite a grand activity and has been recorded in many ancient books.