Lithium monosulphide, Li₂S

The Lithium monosulphide, Li₂S can be prepared by direct synthesis or by reduction of the sulphate with charcoal. The yellow product is amorphous, but heating in the electric furnace transforms it into transparent cubes of specific gravity 1.63 to 1.7. Evaporation of its aqueous solution yields hygroscopic crystals of the hydrosulphide, LiSH:

Li₂S+H₂O ⇔ LiSH+LiOH.

This decomposition is similar to that undergone by other alkali-metal sulphides. The heat of formation of the hydrosulphide in dilute solution is given by the equation

[Li]+[S](rhombic)+(H)+Aq. =LiSH,Aq.+68.3 Cal.