Molybdenum trioxide is an inorganic compound with the chemical formula of MoO3. It is mainly used to determine protein, phenol, arsenic, lead, bismuth, etc. It can also be used as a reducing agent for phosphorus pentoxide, arsenic trioxide, hydrogen peroxide, phenol and alcohol, and can also be used to prepare molybdenum salts and molybdenum alloys. It is used as a catalyst in the petroleum industry, and also in the production of metal molybdenum, enamel and glaze.

It reacts violently with halogen compounds such as bromine pentafluoride and chlorine trifluoride. It can be decomposed by high heat and emits toxic smoke. So, molybdenum trioxide should be stored in a well-ventilated palce. Keep container where molybdenum trioxide powder is placed sealed. It shall be kept by specially-assigned person. It should be stored separately from halides and edible chemical raw materials. Smoking, drinking and eating are not allowed at the operation site. Pay attention to personal protection during repacking and handling.