A Le Chatelier density flask is a laboratory instrument used to determine the density of liquids. The flask is a specialized type of graduated flask that has a unique design, which allows it to compensate for thermal expansion and accurately measure the density of a liquid.

The flask is filled with the liquid to be tested, and the volume is determined by observing the level of the liquid in the flask at two different temperatures. The difference in the volume readings at the two temperatures is used to calculate the density of the liquid.

The Le Chatelier density flask is named after the French chemist Henri Louis Le Chatelier and is widely used in chemical and physical laboratories for determining the density of liquids.