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Manchester bombing

Dear Reader,

It has come to my attention that a bomb was detonated yesterday in Manchester, lets be clear. From the report so far this bombing was an attempt to kill and maim as many people as possible, a cynical and cowardly act aiming at a soft target.

Now right now the UK goverment need to do something, they need to find out if it was a lone criminal or a criminal acting with help from others. Now one of the things which I think is important is to identify the explosive used.

The nature of the explosive will give some clues as to how it was done and the level of help which the bomb maker had. Paul R. Haddad et. al. in Journal of Chromatography A, 2008, 1182, 205–214 explain how to use ion chromatography to identify homemade inorganic explosives such as ANFO, black powder, sugar / chlorate and sugar / perchlorate. In the interests of public safety I will not suggest which of these is most suitable for making bombs. But I can tell you that it is possible from the post detonation fragments to sometimes work out which explosive was used.

For example nitrate anions are characteristic of ANFO (ammonium nitrate / fuel oil) and black powder, while sulfate and thiosulfate are characteristic of black powder. Black powder is the technical term for the “gun powder” made from potassium nitrate, charcoal and sulfur.

From the chlorate / perchlorate explosives it is possible to detect chloride and either chlorate or perchlorate respectively. The information about the nature of the explosive will help the police trace the bomber backwards. In some ways it is similar to an arson investigation. I know that with careful gas chromatography it is possible to identify the brand of petrol used to light a fire. This is a useful thing to know as it is sometimes possible to recover a petrol can from a suspect or obtain CCTV film of them buying petrol shortly before the fire is lit.

Joseph Almog et. al. in Journal of Forensic Sciences, 2007, 52, 1284-1290 does consider the question of how to detect urea nitrate which is another explosive which is sometimes made at home by terrorists. One option for the detection of this explosive is to use para-dimethylamino cinnamalaldehyde, this forms a rather interesting red coloured substance with the explosive. This is reported by Rinat Rozin and Joseph Almog in Forensic Science International, 2011, 208, 25-28.

I downloaded the details of the crystalline solid from the CCDC and here it is. What you should note is that the dimethylamino group is flat, this is an indication that the nitrogen is sp2 hybridised and thus the dimethyl amino group is part of the pi system of the molecule. I think that the nitrogen lone pair is part of the pi system.

molecules of the urea and paradimethylaminocinnamaldehyde thing

Acetone peroxide has also been the subject of some research, this is an explosive which has been used in the past by terror bombers, the explosive is a too sensitive for it to be attractive to the military or the legal explosives industry so when it is found then it is a sign that some “lone wolf” terrorist or other person who can not gain access to “normal” explosives such as TNT has been going about their horrid activities. Likewise I think that the use of urea nitrate and the fuel / chlorate (and perchlorate) mixtures suggests that it is an explosive made by the bomber themselves (or by someone close to them).

Black powder and ANFO are not so clear these are explosives which have legal purposes which can also be made illegally. Black powder is used in fireworks and also sometimes in firearms. Already one group of terrorists (Boston marathon bombers) used fireworks as their source of explosives.

The use of nitroarene and nitroamine explosives such as TNT / picric acid and RDX would suggest to me that the bomber had outside help in the form of someone who could supply explosives such as Semtex to them. It is not uncommon for some trace of the explosive to survive the detonation event so even if a readymade high explosive was used it may be possible to work out what the explosive was. What this means to society is that even while the bomber is dead it maybe possible to work out from physical evidence some clues to what happened and where the bomb came from.

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