A string of bombs detonated over the weekend in New York City and New Jersey. The police have arrested Ahmad Khan Rahami in connection with the attacks. C&EN explores the attacks from a scientific angle, looking at the likelihood that two materials – one called Tannerite and another named hexamethylene triperoxide diamine, or HMTD – were used as explosives. On Tannerite:

“It is impossible,” says Daniel Tanner, CEO of Tannerite Sports. Only a high-velocity bullet travelling at a minimum of 610 meters per second can trigger their exploding targets to go off. Tannerite is also resistant to fire, friction, and hard impacts. It cannot be merely jolted into exploding, suggesting that normal bomb triggers wouldn’t set it off. Furthermore, Tanner says finding aluminum or ammonium nitrate residue isn’t enough to say Tannerite was used. “Tannerite is not a compound,” he says. “It is a trademark.”

“Tannerite is not going to go off by itself,” Oxley says. “It is very stable stuff.

And on HMTD:

“HMTD is not stable and not nice stuff. You can easily set it off,” Oxley says. “To use HMTD there has to be some synthesis involved,” she says. Thus far, there are no reports as to how Rahami could have made or obtained HMTD for use in the bombs.