Mercurium isochromate was a substance used by some species in the Delta Quadrant as an energy source for starship propulsion.

In 2375, Captain Kathryn Janeway offered Torat twenty centiliters of mercurium isochromate as an incentive, as well as promising him enough to power his ship for an entire year, in exchange for his help in locating a wormhole out of Devore space. (VOY: "Counterpoint")