Indigo carmine is a synthetic blue dye that is often used as a food coloring (FD&C Blue #2), as well as in various industrial applications.

Here's how the formula breaks down:

* C18H14N2: This part represents the basic indigo molecule, which contains 18 carbon atoms, 14 hydrogen atoms, and 2 nitrogen atoms.

* Na2: This indicates the presence of two sodium ions, which are responsible for the dye's solubility in water.

* O8S2: This part represents two sulfonate groups (-SO3-), which are also attached to the indigo molecule.

Therefore, the full name of the compound is disodium indigo-5,5'-disulfonate.