Chemical Properties
CALCIUM SULFIDE is OFF-WHITE POWDER
Physical properties
Calcium sulfide is slightly soluble in water but insoluble in alcohol. It reacts with acids, producing hydrogen sulfide gas.
Calcium sulfide is pale yellow to light gray with a bitter
taste. It is hygroscopic, producing an odor of H2S in
moist air.
Occurrence
Calcium sulfide occurs in nature as the mineral oldhamite. It has several applications. The ‘luminous’ calcium sulfide is used in phosphors, luminous paints and varnishes. Calcium sulfide also is used as an additive to lubri cants; and as a flotation agent in ore extraction.
Uses
CALCIUM SULFIDE is used in electron emitters. Luminous CaS used for making luminous paints or varnishes.
Uses
Calcium sulfide may be used to remove heavy metals from wastewater.
Uses
Calcium sulfide is used in phosphors, lubricant additives and luminous paints. It reacts with elemental sulfur to give a lime-sulfur. Further, it is used in ore dressing and flotation agent. In addition to this, it is used as a depilatory in the tanning industry and in cosmetics.
Preparation
Calcium sulfide can be
prepared by the direct reaction of the elements, calcined
in an inert atmosphere, at a 1:1.05 molecular ratio:
Ca＋S＋heat→CaS
This white material crystallizes in a cubic structurelike
rock salt and the bonding is highly ionic. This is
consistent with its description as an ionic solid.
CaS can also be produced by the “carbothermic
reduction” of calcium sulfate, which entails the conversion
of carbon, usually as charcoal, to CO2:
CaSO4＋ 2C→CaS＋ 2CO2
This can react further:
3CaSO4＋ CaS→4CaO＋ 4SO2
Thus, this type of preparation cannot be used to
prepare a pure CaS salt.
Calcium sulfide is available commercially as the pure
sulfide as well as the polysulfide due to its extensive
usage in the past as an insecticide both agriculturally
and in home gardens.
General Description
Crystal structure of CaS is cubic. Electrical conductivity of calcium sufide in the temperature range of 650
oC-1000
oC was studied in great detail. It was concluded that CaS could be used as a potential electrolyte in a sulfur concentration cell.2
