After the first use of crucible immerse in 6 n hydrochloric acid solution, the carbon deposition caused by an organic compound sample available alcohol lamp burnt up carbon deposition, if carbon and metal oxides exist at the same time, can be burned in the alcohol lamp, the crucible first after cooling put in 6 n hydrochloric acid soaking, soak out after several hours, add distilled water, then dump, until close to neutral, with washing bottle blow wash for several times, then use infrared drying oven drying.