Back in the days before pilots a.k.a. "cowcatchers," cattle could cause the train to derail when struck--potentially killing the passengers on board. Putting salt on a railroad track would attract cattle and other large hooved animals. In Alabama, it is still considered a crime because the it's cruel, and the animal could still potentially hit the cab even though modern trains are built with pilots and anti-climbers*.
*Anti-climber-a device to help prevent objects struck by the train from rising up and hitting the cab of a locomotive.
the salt starts to disintegrate
It dies.
It floats.
nothing
explodes
People sometimes put their ear on a railroad track to see if a train is coming. It does not work because of the iron rail, it works because of the vibrations the train makes on the rail as it is moving.
Water dissolve and transport salt.
Nothing. They're terrestrial.
Your feet get wet.
The concentration of salt increase up to saturation.
The color of the flame depends on the metal from the salt.
It lowers the boiling point, and makes it "salt water".