There are two possibilities you might be thinking of:

1. Carbon disulfide (CS₂): This is a highly flammable and toxic liquid. Its empirical formula is the same as its molecular formula: CS₂.

2. Carbon monosulfide (CS): This is a highly reactive molecule that exists in the gas phase. Its empirical formula is CS.

It's important to note that carbon disulfide is the more common and well-known compound, and it's likely what you're referring to.