What happened in the show: Fulminated mercury, or mercury(II) fulminate is first introduced to us in Season 1, where Walt uses the substance as an example of an explosive chemical when teaching his high school Chemistry class in Episode 6. Later on though, we see its effects in the real world when Walt uses it to blow up the headquarters of Tuco Salamanca. He throws a small bag of it to the floor to activate it, and it causes the windows to shatter and the cronies inside to run for cover. Walt walks away unscathed. Could it really happen? Yes, but not like it did in the show. Its true that fulminated mercury is a highly explosive chemical; its very unstable and can be detonated by triggers such as friction, heat, spark or shock. Walt goes for the shock option and throws it at the floor. The amount that Walt had was very small though, and he would have needed a much larger quantity of the compound thrown at much faster speeds to trigger an explosion of the size we saw. In that case though, he and everyone else in the building would have died so it wouldnt exactly have made good TV, accidentally killing off one of the main characters.
