The test point of this question is the characteristics of powder. The powder has the following characteristics: large specific surface area, easy dispersion, good absorption and quick action; Simple preparation; External use has a certain mechanical protection effect on the sore surface; Widely used in stomatology, otolaryngology, trauma and surgery, and also suitable for children. However, due to the large specific surface area, the powder is easy to absorb moisture, the chemical composition of the drug is enhanced, and it is easy to lose oxidation. Therefore, drugs that are easy to absorb moisture or undergo oxidative deterioration, drugs that are highly irritating, and drugs that contain a large amount of volatile components and large doses are not suitable for making powder.