The Dean Stark is a type of laboratory glassware used in synthetic chemistry to collect water, or sometimes other liquid, from a reactor. The apparatus was invented by E. W. Dean and D. D. Stark in 1920 for determining water content in petroleum. Used in combination with a reflux condenser and a batch reactor, it ensures continuous elimination of the water that is produced during a chemical reaction conducted at reflux temperature. There are two types of Dean Stark apparatus � one designed for use with solvents having density less than water and the other for use with solvents having density greater than water.