Superboy (vol 1) #228 VF

The President of Earth calls in the leaders of the Legion of Super-Heroes to handle the governor of Australia, Deregon. He intends to start a war that would cause a world war and the President implores the Legion to prevent that from occurring. The Legion learns that Deregon has a partner from off the planet but are unable to figure out who it is, so Chemical King is asked to trace the calls with his unique abilities, even though he doesn't feel that he's a worthwhile Legionnaire. Eventually, Deregon learns the Legion is spying on him and declares war, starting a deadly radiation sphere that could destroy the planet. He reveals he's working for the Dark Circle and Chemical King sacrifices his life when he uses his power to stop Deregon. The Legion are ready to avenge his death.