Carbon Monosulphide, CS

The first indication of the existence of the sulphur analogue of carbon monoxide was the observation of Losanitsch and Jovitschitsch that carbon disulphide is decomposed by the silent electric discharge in presence of hydrogen or carbon monoxide with the formation of a lower sulphide supposed to be CS; Thomsen also found that when nitrogen saturated with carbon disulphide vapour is passed repeatedly over heated copper, the copper removes some sulphur from the disulphide, leaving the monosulphide. More recently Dewar and H. O. Jones found that thiocarbonyl chloride reacts rapidly with nickel carbonyl at the ordinary temperature according to the equation:

xCSCl₂ + xNi(CO)₄ = xNiCl₂ + 4xCO + (CS)_x.

When nickel chloride is extracted by water from the solid product, a brown substance remains which by analysis is shown to have the empirical composition represented by the formula CS, but which, on account of its being a non-volatile solid, must be a polymer (CS)_x. The same product was always obtained, although the conditions of its formation were varied, and after purification and drying it had a density of about 1.6 in the finely divided state and of 1.83 after compression.

Polymerised carbon monosulphide gives a purplish-brown solution with concentrated sulphuric acid, from which the unchanged substance is reprecipitated on pouring into water. Aqueous and alcoholic solutions of ammonia, ammonium sulphide, and potassium hydroxide, sulphide, and hydrosulphide, also give deep brown solutions from which the monosulphide is precipitated unchanged by acid. The solid is unchanged below 360° C. in a vacuum, but at a low red heat a change takes place in accordance with the equation:

2(CS)_x = xC + xCS₂.

When carbon disulphide is exposed for a long time to sunlight a red substance is obtained, which is supposed also to be a polymeric form of the monosulphide.

So far the nature of the simple substance CS had not been elucidated, but Dewar and Jones followed up this communication with another in which evidence was forthcoming of the formation of the non-polymerised monosulphide. Carbon disulphide vapour at low pressure was submitted to the action of the silent electric discharge, with the consequence that sulphur separated. When the resulting vapour was cooled in a tube immersed in liquid air and then brought again to the temperature of the atmosphere an explosion took place, and the brown substance previously identified as (CS)_x was formed. It appears, therefore, that carbon monosulphide is an endothermic gas, condensible by means of liquid air, which rapidly polymerises to (CS)_x at atmospheric temperature.