Dichromate (Cr2O72-) is a chemical ion containing chromium and oxygen.
The "Silver Blood", discovered by the USS Voyager on a Y-class planet in 2374, were composed of deuterium, hydrogen sulfate, dichromates, and proteins. (VOY: "Demon")
In 2375 aboard the mimetic USS Voyager, created from the Silver Blood, the Doctor used a dichromate catalyst to revert the mimetic B'Elanna Torres back into her original fluid state. (VOY: "Course: Oblivion")