Urea, also known as urea or carbonamide, is a final product of protein metabolism in humans and mammals, and is also a major organic nitrogen compound excreted by animals. The pure product is white granular or needle-like or prismatic crystal, and it is light red or yellow mixed with heavy metals such as iron. Tasteless and odorless, easily soluble in water, ethanol and benzene, insoluble in ether and chloroform. At 20°C, 100 kg of water can dissolve 105 kg of urea, and it absorbs heat during dissolution. Aqueous solutions are neutral. The nitrogen content of the pure product is 46.65%, and the agricultural urea is 42% to 46%. It contains a small amount of biuret, generally less than 2%, which is usually harmless to the growth of crops. The specific gravity and bulk density of urea are small, and each cubic meter The fertilizer weighs 0.65 tons. When the temperature is below 20°C and the relative humidity is lower than 70%, urea will not only absorb moisture, but will also evaporate the water and reduce its water content; when the temperature exceeds 20°C and the relative humidity is higher than 80%, it will begin to absorb moisture. It was mushy and re-agglomerated when the air was re-dried, second only to ammonium nitrate. When the urea aqueous solution is at 80 °C, hydrolysis and decomposition reactions will occur, forming ammonium carbamate, ammonia gas, and carbon dioxide, respectively. Under acidic and alkaline conditions, the decomposition of urea is accelerated when it is heated.