Heavy water, Vemork museum, Rjukan, Norway

Heavy water (D2O)was first discovered in USA in 1933. It was established that ordinary water contains 0.02% heavy water. Heavy water has poilin point 1.04C above ordinary water and it freezes by 40C.The hydrogen is of a special kind which is twice the weight of ordinary hydrogen. This giving heavy water a 10% weight increase over ordinary water. Heavy water is used as a "breake fluid" in atomic fision. In the Norsk Hydro facilites in Vemork heavy water has first commercial success in 1934. During the WWII Norsk Hydro facilites in Vemork became  under the German control and research in an attempt to make nuclear weapons.