Barium Chloride (BaCl2): Properties, Preparation & Uses

Barium chloride (BaCl2) is a chemical compound composed of one barium ion (Ba2+) and two chloride ions (Cl-) in a 1:2 ratio. In other words, it is an inorganic compound that is one of the most common water-soluble salts of barium. It is a white powder that is highly toxic and imparts a yellow-green coloration to a flame.

This compound is used in the laboratory as a precipitating agent and also to prepare other barium compounds. It is formed by the reaction of barium hydroxide and chlorine gas, resulting in colorless crystals that are soluble in water. Barium chloride is a white solid that is soluble in water and its chemical formula is BaCl2. It is a strong electrolyte and is used as a cathode material in electroplating.

Barium Chloride Structure

Barium chloride (BaCl2) has a crystal structure in which each barium ion (Ba2+) is surrounded by eight chloride ions (Cl-) and each chloride ion is surrounded by four barium ions. The arrangement of atoms in the crystal lattice of barium chloride is such that it forms a three-dimensional network.

In its crystalline form, barium chloride adopts a crystalline lattice structure known as the orthorhombic crystal system. This means that its unit cell has three axes of different lengths at right angles to each other.

Each barium ion is surrounded by eight chloride ions in a cubic arrangement. Likewise, each chloride ion is surrounded by four barium ions.

The structural formula of barium chloride can be represented as BaCl2•xH2O, indicating that it may also contain water molecules within its structure when in hydrated form. This hydrated form is usually found as BaCl2·2H2O (barium chloride dihydrate), where each formula unit of BaCl2 is associated with two water molecules.

Preparation of Barium Chloride

Barium chloride (BaCl2) is an inorganic compound that can be prepared in various ways.

One method involves reacting barium hydroxide (Ba(OH)2) or barium carbonate (BaCO3) with hydrogen chloride (HCl). In this process, the barium hydroxide or barium carbonate is mixed with hydrochloric acid, which results in the formation of barium chloride and water. The reaction between barium hydroxide and hydrochloric acid is represented by the following chemical equation:

Ba(OH)2 + 2 HCl → BaCl2 + 2 H2O

The reaction between barium sulfide and hydrochloric acid can produce Barium Chloride:

BaS + 2HCl → BaCl2 + H2S

Alternatively, barium chloride can also be prepared by reacting barium oxide (BaO) with hydrochloric acid, as shown in the following chemical equation:

BaO + 2 HCl → BaCl2 + H2O

Another method involves the direct reaction of barium metal with chlorine gas to form barium chloride:

Ba + Cl2 → BaCl2

However, this method is less common because the direct reaction of a metal with a non-metal is usually avoided due to safety concerns.

In an industrial setting, barium chloride is produced through the reaction of barium sulfate (BaSO4) with either hydrochloric acid or sulfuric acid:

BaSO4 + 2 HCl → BaCl2 + H2SO4 BaSO4 + H2SO4 → BaCl2 + 2 H2O + SO2

These reactions take place in a controlled environment to ensure the safety of the process and to prevent the release of harmful gases.

Physical Properties of Barium Chloride

  • Barium chloride (BaCl2) is a white crystalline solid.
  • It has a melting point of 962 °C (anhydrous) and a boiling point of 1,560 °C.
  • The molar mass of anhydrous barium chloride is 208.23 g/mol, and for the dihydrate form, it is 244.26 g/mol.
  • The density of the anhydrous form is 3.856 g/cm3, and for the dihydrate form, it is 3.0979 g/cm3.
  • The solubility of barium chloride in water is approximately 31.2 g/100 mL at 0 °C, 35.8 g/100 mL at 20 °C, and 59.4 g/100 mL at 100 °C.
  • It is soluble in methanol but insoluble in ethanol, ethyl acetate, and toluene.
  • The vapor pressure is close to 0 mmHg.
  • Barium chloride is a strong electrolyte and dissociates in water to form Ba2+ and Cl- ions.
  • It is highly toxic and imparts a yellow-green coloration to a flame.
  • Hygroscopicity: Hygroscopic (absorbs moisture from the air)
  • pH of Aqueous Solution: Acidic (around pH 5-6)
  • Odor: Odorless

Chemical Properties of Barium Chloride

  • Hygroscopicity: Absorbs moisture from the air, forming hydrated forms.
  • Solubility in Water: Highly soluble, forming an aqueous solution.
  • Acid-Base Properties: BaCl2 aqueous solution is slightly acidic, with a pH around 5-6.
  • Thermal Decomposition: Upon heating, it decomposes to form barium oxide (BaO) and hydrogen chloride gas (HCl).
  • Redox Reactions: It can act as an oxidizing agent, especially in reactions involving metals like aluminum.
  • Formation of Complexes: Forms complexes with ligands due to the high charge density of the barium ion.
  • Reaction with Sulfates: Forms insoluble barium sulfate (BaSO4) upon reaction with sulfate ions, commonly used in analytical chemistry for the detection of sulfate ions.
  • Precipitation Reactions: Forms insoluble salts with certain anions, such as sulfate and carbonate ions.
  • Reaction with Water: Reacts with water to form barium hydroxide and hydrogen chloride gas.

Uses of Barium Chloride

  • Heat treatment of metals: Used in heat-treating baths to alter the properties of metals.
  • Barium salt manufacturing: A primary raw material for producing other barium salts.
  • Electronic instruments: Used in the production of specific electronic components.
  • Water softener: Helps to soften hard water by precipitating calcium and magnesium ions.
  • Identification and separation of SO42- ions: Used to identify and separate sulfate ions in laboratory experiments.
  • Purification of brine water: Used to purify brine water in caustic chlorine plants.
  • Manufacture of barium salts and pigments: Used in the production of various barium salts and pigments.
  • Dehydrating agent and analysis reagents: Used as a dehydrating agent and in analytical chemistry.
  • Machining heat treatment calibration instruments and devices: Used in the calibration and production of heat-treatment equipment.
  • Evaluation methodology and quality assurance: Utilized in quality control and evaluation processes.
  • Wool and leather industry mordant: Used as a mordant in the wool and leather industries.
  • Pesticides for controlling plant pests: Employed as a component in pesticides to control plant pests.
  • Firework production: Used in the manufacture of fireworks for various color effects.
  • Hardening of steel: Used in the hardening of steel to improve its mechanical properties.
  • Lubrication oil additive: Added to lubrication oils to improve their performance.
  • Textile dye: Used in the dyeing of textiles.
  • Pigments: Used in the production of various pigments.
  • White leather: Used in the processing of white leather.
  • Aluminum refining: Employed in the refining process of aluminum.
  • Boiling water treatment: Used in the treatment of boiling water.
  • Porcelain enamels for sheet steel: Used in the production of porcelain enamels for sheet steel.