Distillation Flask

Distilling flasks are made of glass, and consist of three main parts: a spherical base, a cylindrical neck, and a cylindrical sidearm that is connected to the flask neck. They are usually made of a type of glass (such as Borosilicate) that can withstand high temperatures.
The distilling flask is used to separate liquid mixtures by distillation. Distillation is the process of separating mixtures based on the difference in boiling points of the components of that mixture. As the flask and the contents are heated, each component of the mixture changes from the liquid phase to the gas phase (components change in order from lowest boiling point to highest boiling point). As the molecules in the gas phase rise, they are usually routed through the sidearm into a condenser (the top of the neck is usually sealed with a cork or rubber stopper)