Potassium sulfide represented by the chemical formula K₂S is a compound of potassium and sulfur that is moderately soluble in acids ^[1]. It is deliquescent and may spontaneously ignite in air. It is a reducing agent and an ionic compound ^[4].

Potassium Sulfide Identification
CAS Number	1312-73-8 [1]
PubChem CID	20072150 [3]
ChemSpider ID	142491 [2]
EC Number	215-197-0 [1]

Composition and Synthesis

Potassium sulfide can be prepared by first treating potassium hydroxide to excess hydrogen sulfide to form potassium hydrosulfide (KHS). Further treatment of KHS with the same amount of potassium hydroxide generates potassium sulfide ^[9].

KOH + H₂S = KHS + H₂O

KHS + KOH = K₂S + H₂O

Properties and Characteristics of Potassium Sulfide

General Properties
Molar mass/molecular weight		71.158 g/mol [3]
Physical Properties
Color/appearance		White to yellow powder [4]
Melting point/freezing point		840°C, 1544°F [1]
Boiling point		912°C, 1674°F [1]
Density		1.80 g cm-3 [1]
State of matter at room temperature (normal phase)		Solid [1]
Chemical Properties
Solubility in water		N/A [1]
pH		>7 (basic) [5]
Atomic Properties
Crystal structure	Tetrahedral [6]

 

Prominent Reactions of K₂S

Potassium sulfide reacts with cobalt iii bromide to produce cobalt iii sulfide and potassium bromide ^[10].

3K₂S + 2CoBr₃ = Co₂S₃ + 6KBr

Potassium sulfide reacts with dilute hydrochloric acid to produce potassium chloride and hydrogen sulfide ^[11].

K₂S + 2HCl = 2 KCl + H₂S

It reacts with concentrated sulfuric acid to give potassium bisulfate, sulfur dioxide, sulfur and water ^[13]

K₂S + 3H₂SO₄ = 2KHSO₄ + SO₂ + S + 2H₂0

The compound reacts with silver nitrate to form aqueous potassium nitrate and silver sulfide precipitate ^[12].

K₂S + 2AgNO₃ = 2KNO₃ + Ag₂S

Potassium Sulfide Uses

1. In pyrotechnics ^[7].
2. As a reagent in analytical chemistry ^[4].
3. As a depilatory and medicine ^[4].

Is It Dangerous

It may cause a fire hazard, so precautions must be taken not to bring it in contact with air. In the form of powder or dust, it is explosive. Ingestion, inhalation and skin contact may result in severe injury and even death.  It also harmfully affects the eyes and skin causing eye damage and skin burns. Hence all contact should be avoided. It emits toxic fumes if heated to decomposition ^[4]. It is of a corrosive nature and poisonous for the environment ^[8].

References
1. Potassium Sulfide – Americanelements.com
2. Potassium Sulfide – Chemspider.com
3. Potassium Sulfide – Pentachemicals.eu
4. Potassium Sulfide – Chemicalbook.com
5. Is K2S acidic or basic? – Quora.com
6. Dipotassium Sulfide – Webelements.com
7. What are the uses of potassium sulfide? – Quora.com
8. Potassium Sulfide – Merckmillipore.com
9. Preparation of potassium sulfide – Prepchem.com
10. Solubility Rules and Net Ionic Equations Practice – Vincentianacademy.org
11. Potassium sulfide react with hydrogen chloride – Chemiday.com
12. Question #e42f1 – Socratic.org
13. Potassium sulfide react with sulfuric acid – Chemiday.com