An ancient book recorded that he tasted the nature of a thing and asked the wise man: "Is Hf Soluble?" The wise man said to him: "If you want to know whether Hf is soluble, you should examine the environment in which it is located. If it is in a certain liquid, you should observe its change. Whether it is soluble or insoluble, it is controlled by its quality and the nature of the liquid. And whether a thing dissolves or not depends not only on the liquid, but also on temperature and pressure. Temperature is high, or it promotes its dissolution; pressure is different, or it changes its state. Examine it carefully, and Fang Ming will understand the dissolution of Hf in different environments."