Thioformaldehyde, (H₂CS)₃

Thioformaldehyde, (H₂CS)₃, results from the reduction of carbon disulphide by nascent hydrogen.

Methyl mercaptan cannot be obtained directly from carbon disulphide, but methane may be prepared by passing the vapour together with hydrogen sulphide over heated copper:

CS₂ + 2H₂S + 8Cu = 4Cu₂S + CH₄.

Carbon disulphide, like the dioxide, is the anhydride (or, more strictly, thioanhydride) of a feeble acid, thiocarbonic acid, H₂CS₃. Moreover, between carbonic and thiocarbonic acids a number of intermediate acids are capable of existence. They are as follows:

Carbonic Acid.

Thionearbonic Acid.

Thiolcarbonic Acid. (Xanthic Acid).

Thiolthioncarbonic Acid

Dithiolcarbonic Acid.

Thiocarbonic Acid.