Potassium Sulfide (K2S): Preparation, Properties And Uses

Overview

Potassium sulfide is an inorganic salt that is not found as an isolated compound in nature. It always found as a mixture with potassium hydrosulfide. It is a colorless crystal with a typical sulfur smell. Potassium sulfide can be prepared through the reaction of pure carbon with potassium sulfate at high temperatures. Potassium sulfide is used as a component of pyrotechnics. It is used particularly in Asia to manufacture the fireworks Senki hanabi.

Other names of potassium sulfide are:

• Dipotassium monosulfide
• Dipotassium sulfide
• Potassium monosulfide

Potassium Sulfide Identification

Preparation

• Hydrogen sulfide is passed through 3 parts of concentrated potassium hydroxide solution until no further absorption takes place.
• 2 parts of concentrated potassium hydroxide solution is added in order to neutralize potassium hydrosulfide.
• In preparation of potassium sulfide, it is far much better for the mixture of potassium hydroxide and potassium sulfide (preparation mixture) to contain a little potassium hydrosulfide than potassium hydroxide.
• More importantly, potassium sulfide should be well protected from air and moisture.
• Alternatively, it can be prepared in the laboratory by reaction of potassium and sulfur in anhydrous ammonia.
• Potassium sulfide can also be prepared through the reaction of pure carbon with potassium sulfate at high temperatures.

Chemical And Physical Properties Of Potassium Sulfide

• The chemical formula of potassium sulfide is K₂S. this means that the compound is formed by two potassium cation (K⁺) and one sulfide anions S^2-
• Pure Potassium sulfide is colorless whereas the impure potassium sulfide is yellow-brown.
• Potassium sulfide crystal has a typical sulfur smell.
• It is moderately soluble in water and acids.
• Potassium sulfide is not found in nature.
• The geometry of the potassium sulfide molecule is an antifluorite structure, with a cation K⁺ being surrounded by eight sulfide anions.
• Potassium sulfide is soluble in ethanol, glycerol.
• Potassium sulfide reacts with water.
• It is insoluble in ether.
• Chemically stable under the conditions of storage, handling and use.
• The density of potassium sulfide is 1.74g/cm³
• The melting point of potassium sulfide is 840^oC (1540^oF, 1,110K).
• The boiling point of potassium sulfide 912^oC (1,674^oF, 1185K).
• It has a molar mass of potassium sulfide is 110.262 g/mol
• Potassium sulfide has a tetrahedral crystal structure
• Potassium sulfide is highly flammable and its particles can form explosives mixtures in air, igniting spontaneously.
• The monoisotopic mass of potassium sulfide is 109.8999483 Da.
• Potassium sulfide is not found as an isolated compound, it is always found as forming the mixture with KSH.
• Potassium sulfide suffers spontaneous hydrolysis in water, reacting to form potassium hydroxide and potassium hydrosulfide.

Chemical Reactions Of Potassium Sulfide

Potassium sulfide (K₂S) reacts with silver nitrate (AgNO₃) to form aqueous potassium nitrate (KNO₃) and silver sulfide precipitate.

Potassium sulfide (K₂S) reacts with dilute hydrochloric acid (HCl) to form potassium chloride (KCl) and hydrogen sulfide (H₂K).

Potassium sulfide (K₂S) reacts with cobalt III bromide (CoBr₃) to form cobalt III sulfide and potassium bromide (KBr).

Potassium sulfide (K₂S) reacts with concentrated sulfuric acid (H₂SO₄ ) to give potassium bisulfate, sulfur dioxide, sulfur and water.

Uses Of Potassium Sulfide

• Used  as a component of pyrotechnics
• It is used particularly in Asia to manufacture the fireworks senki hanabi.
• As a reagent in analytical chemistry.
• It also has been used for staining and coloring bronze and other metals.
• Used in the production of glitter.
• Used as depilatory and medicine.
• It is also used as a photographic toner.

Health Effects

Potassium sulfide is dangerous for health. The toxic fumes formed after heating are harmful for inhalation. It is highly flammable and its particles can form explosives mixtures in air, igniting spontaneously.

Summary Of Properties Of Potassium Sulfide In Tabular Form