Sodium perthiocarbonate, Na₂CS₄

Sodium perthiocarbonate, Na₂CS₄, is formed when an alcoholic solution of sodium sulphide is converted into the disulphide by the addition of sulphur and subsequently treated with carbon disulphide. Perthiocarbonates may also be formed by the direct combination of thiocarbonates with sulphur. There is no analogy to this latter method of preparation in the case of percarbonates; this fact is usually regarded as illustrating the superior chain-forming power of sulphur atoms as compared with oxygen atoms.

The ammonium salt may be obtained by extracting ammonium pentasulphide with carbon disulphide in a Soxhlet apparatus, washing first with hot carbon disulphide and then with ether, and centrifuging.