Hydroxypropyl methylcellulose (Hypromellose), also known as hypromellose, is a kind of non-ionic cellulose mixed ether. It is a semisynthetic, inactive, viscoelastic polymer commonly used as a lubricant in ophthalmology, or as an excipient or vehicle in oral medicines. Soluble in water and some solvents, such as appropriate proportion of ethanol/water, propanol/water, etc. Aqueous solutions are surface active. High transparency and stable performance. Different specifications of products have different gel temperatures, and solubility changes with viscosity. The lower the viscosity, the greater the solubility. Different specifications of HPMC have certain differences in performance. The dissolution of HPMC in water is not affected by pH value.