New images related to the sinister of Tianjin (China) show the presence of a huge crater, whose epicenter is located at ground zero of the explosion.
These images remind to those obtained after the incident which took place on September the 22nd 2001 at the AZF chemical plant in Toulouse, France.
This incident occurred when 500 kg of sodium dichloroisocyanurate were mistakenly stored as ammonium nitrate. Both products reacted and formed nitrogen trichloride, whose following decomposition caused the ammonium nitrate detonation.
Although in the case of Tianjin is still early to establish the causes of the accident, the worldwide press drew to acetylene as the chemical which caused the first explosion. This compound, highly explosive, is obtained by reacting calcium carbide and water. Early theories suggest that this explosion of acetylene triggered the catastrophic explosion that followed.
Taking into account the few news known, it is not easy to determine who or what caused the explosion. However, the size and shape of the crater indicates that the causative chemical was in solid state, ready to be sold in bulk. A chemical in liquid phase is not seen as the cause because such chemicals are stored in metal containers, and the walls of these latter prevent cratering.
It is known that large amounts of sodium cyanide have been released to the atmosphere. This chemical is typically used in conjunction with the ammonium nitrate to obtain salts, so is quite possible that ammonium nitrate was also stored in facilities. According to its properties, as well as the events of AZF, it seems that the cause of the explosion that rocked Tianjin on August the 5th was the ammonium nitrate, whose detonation was caused by acetylene.
Anyway, it is too early to clarify the causes of the disaster, so we are waiting for the news coming from Beijing.