A police source told The Associated Press the substance was believed to be triacetone triperoxide, or TATP, an explosive used in the 2005 London bombings.

One weapons expert said even a tiny amount of TATP could blow a person's hand off. "It is very unstable, very sensitive to both friction and shocks," Svante Karlsson, a weapons expert at the Swedish Defense Research Agency, told AP, adding the substance had no civilian use.

Can I replace substance with chemical without change of meaning?


Yes. In a context like this, there's not much difference.

Thanks, Clive.