MODEL RELEASED. Chemistry research. Male research chemist in laboratory. The chemist is working with a series of reflux condensers holding different coloured liquids. A reflux condenser is used to carry out reactions at high temperatures. It will rapidly cool any vapour which rises from the reaction mixture. The vapour is condensed and falls back into the reaction mixture. This allows reactions to be carried out at boiling point. The reflux condenser cooling medium used here is liquid nitrogen. Nitrogen is liquid at minus 195.7 degrees Celsius. The liquid is fed into the reflux system from the fuming containers at the bottom of the picture.