Ans: PETN stands for pentaerythritol tetranitrate. It is a complex organic compound containing nitrogen. Therefore, it belongs to the same family of nitrocellulose and nitroglycerin. Both these compounds are highly explosive in nature. Therefore, PETN also shows high explosive properties. PETN is produced by the chemical reaction between nitric acid and the alcohol pentaerythritol. The alcohol is commonly used in different varnishes and paints. Since the reaction is exothermic, it is carried out in chilled conditions.During the reaction, PETN is formed as a precipitate. It is precipitated out and filtered to remove any debris. After that, PETN is washed and dried. It is then subjected to a recrystallization process. The PETN crystals are then stored in a mixture of water and alcohol. This step is feasible because it is non-reactive with water. Moreover, keeping it in cold condition keeps it away from its ignition point.