Copper ii sulfide or cupric sulfide represented by the chemical formula CuS that bears the IUPAC name sulfanylidenecopper ^[1] is a black powder or lumps that is soluble in nitric acid but insoluble in water ^[3]. It occurs as the mineral covellite and is an ionic compound ^{[3, 4]}. It is stable in air when it is dry but gets oxidized to copper sulfate by moisture in the air ^[1].

Copper II Sulfide Identification
CAS Number	1317-40-4 [1]
PubChem CID	14831 [1]
ChemSpider ID	145403 [2]
EC Number	215-271-2 [1]

Composition and Synthesis

Copper ii sulfide can be prepared by a reaction between molten sulfur and copper that is later followed by boiling in sodium hydroxide ^[1].

Cu + S = CuS

Properties and Characteristics of Copper 2 Sulfide

General Properties
Molar mass/molecular weight		95.606 g/mol [1]
Physical Properties
Color/appearance		Black powder [3]
Melting point/freezing point		220°C, 428°F (decomposes) [3]
Boiling point		N/A [3]
Density		4.6 g ml-1 at 25°C [3]
State of matter at room temperature (normal phase)		Solid [3]
Refractive index		1.45 [1]
Chemical Properties
Solubility in water		N/A [1]
Atomic Properties
Crystal structure	Hexagonal [1]

Prominent Reactions of CuS

Copper ii sulfide reacts with oxygen at a temperature of 300-500°C to form copper oxide and sulfur dioxide ^[7].

2CuS + 3O₂ = 2CuO + 2SO₂

Cupric Sulfide Uses

1. In the preparation of mixed catalysts ^[3].
2. In developing aniline black dye for textile printing ^[3].
3. In antifouling paints ^[3].
4. In photo optic applications and as a semiconductor ^[6].

Is It Dangerous

Cupric sulfide is toxic if ingested. Contact with eyes and skin and inhalation should be avoided since it may cause irritation. It has a long lasting harmful effect on aquatic life ^{[1, 3, 5]}. Under fire conditions, it decomposes to produce hazardous copper oxides and sulfur oxides ^[8].

References
1. Copper (II) Sulfide – Pubchem.ncbi.nlm.nih.gov
2. Copper (II) Sulfide – Chemspider.com
3. Copper (II) Sulfide – Chemicalbook.com
4. Ionic bond examples – Examples.yourdictionary.com
5. Copper Sulfide CuS – Espimetals.com
6. Copper Sulfide – Americanelements.com
7. Copper sulfide react with oxygen – Chemiday.com
8. Material Safety Data Sheet – Chembk.com