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Potassium Sulfide

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

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

Potassium Sulfide Formula

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]

Potassium Sulfide Structure

Lewis Dot Structure for Potassium Sulfide


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].


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  5. Is K2S acidic or basic? –
  6. Dipotassium Sulfide –
  7. What are the uses of potassium sulfide? –
  8. Potassium Sulfide –
  9. Preparation of potassium sulfide –
  10. Solubility Rules and Net Ionic Equations Practice –
  11. Potassium sulfide react with hydrogen chloride –
  12. Question #e42f1 –
  13. Potassium sulfide react with sulfuric acid –

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