This document is applicable to the low-boiling mixed liquid with butyric acid as the main component obtained from the top of the light removal tower in the process of producing butyric acid through oxidation and distillation using n-butyraldehyde as raw material, and is used as raw material for the production of mixed esters. Molecular formula of butyric acid: C4H8O2 Relative molecular mass of butyric acid: 88.11 (according to the 2016 international relative atomic mass)