A pneumatic trough is a laboratory apparatus used in chemical experiments to mix gases and liquids. It is a shallow, cylindrical container with a gas inlet and a stirrer that is powered by compressed air. The compressed air creates a stream of bubbles that rise through the liquid in the trough, mixing the contents and facilitating the transfer of gases between the liquid and the gas phase.

Pneumatic troughs are commonly used in chemical synthesis, especially in the preparation of gases such as oxygen and chlorine, and in the study of gas-liquid reactions. They are also used in environmental chemistry to measure the concentration of gases in water samples.