Disodium

From Memory Alpha, the free Star Trek reference.

Disodium is a component of the Arachnid Nebula, where it exists in a layer.

While aboard the Vahklas, a Vulcan civilian transport ship, in 2151, Subcommander T'Pol detected more than twenty million cubic meters of disodium in the Arachnid Nebula. (ENT: "Fusion")