Chemist checking the temperature of a distillation apparatus. The liquid being distilled is heated in a glass flask enclosed by the metal water-bath. An electrically-heated water bath is used when volatile substances are to be distilled; the naked flame of a bunsen burner would cause an explosion. Vapour is cooled in the large glass condenser (containing spiral tubing) and the distillate collected in the lower glass flask. Photographed in a quality control laboratory of the National Dairy Development Board, Gujarat, India.