NICKEL CHLORIDE (NICL2): STRUCTURE, PROPERTIES, PRODUCTION, USES - CHEMISTRY - 2025

The nickel chloride or nickel chloride (II) is an inorganic compound consisting of the elements nickel (Ni) and chlorine (Cl). Its chemical formula is NiCl ₂. It is a golden yellow solid when it is anhydrous (without water in its structure) and green in its hydrated form.

Anhydrous NiCl ₂ is a hygroscopic solid, it absorbs water easily, and is very soluble in it, forming green solutions. Its aqueous solutions are acidic. Hydrated NiCl ₂ has an affinity for NH ₃ ammonia, that is, it absorbs it easily due to the tendency of nickel ion (Ni ²⁺) to bind to ammonia. For this reason it is used in safety masks to breathe freely in environments where there is NH ₃, which is toxic.

Nickel (II) chloride anhydrous NiCl ₂. Author: Softyx. Source: Wikimedia Commons.

Nickel chloride is widely used in processes to make nickel coatings or coatings on other metals, to protect them from corrosion and other damage.

It is used as a catalyst or accelerator of reactions between organic compounds. Also to prepare catalysts of other nickel compounds. It has recently been tested on some batteries to improve battery performance.

However, NiCl ₂ is a very toxic compound that can harm humans and animals. It is a carcinogenic and mutagenic substance. It should never be disposed of into the environment.

Structure

Nickel (II) chloride NiCl ₂ is an ionic compound. It is formed by the nickel ion (Ni ²⁺) (with oxidation state +2) and two chloride ions (Cl ^-) with -1 valence.

Nickel (II) chloride. Author: Marilú Stea.

Nomenclature

• Nickel (II) chloride
• Nickel chloride
• Nickel dichloride
• Nickel chloride hexahydrate NiCl _{2 •} 6H ₂ O

Properties

Physical state

Golden yellow or green crystalline solid.

Molecular weight

129.6 g / mol

Sublimation point

The anhydrous NiCl ₂ when reaching 973 ° C goes from the solid state directly to the gaseous state.

Triple point

Anhydrous NiCl ₂ at a temperature of 1009 ° C exists simultaneously in its three states: solid, liquid and gaseous.

Density

3.51 g / cm ³

Solubility

Soluble in water: 64.2 g / 100 mL of water at 20 ° C; 87.6 g / 100 mL at 100 ° C. Soluble in ethanol (CH ₃ -CH ₂ -OH) and in ammonium hydroxide (NH ₄ OH). Insoluble in ammonia NH ₃.

pH

Its aqueous solutions are acidic, with a pH around 4.

Chemical properties

It is a solid with deliquescent properties, that is, it absorbs water from the environment easily. Anhydrous NiCl ₂ (without water) is golden yellow. The hexahydrate form (with 6 water molecules) NiCl _{2 •} 6H ₂ O is green in color.

Nickel chloride hexahydrate NiCl _{2 •} 6H ₂ O. Benjah-bmm27 / Public domain. Source: Wikimedia Commons.

Anhydrous NiCl ₂ in the absence of air sublimates easily.

NiCl ₂ is very soluble in water. In aqueous solution it separates into its Ni ²⁺ and Cl ^- ions. Aqueous solutions are acidic. In solution, the nickel ion joins 6 molecules of water H ₂ O, forming the hexaaquonickel ion ²⁺, which is green.

If the pH of these aqueous solutions is increased by adding for example sodium hydroxide (NaOH), the nickel hydroxide Ni (OH) _{2 is formed,} which precipitates or separates from the water forming a bulky green gel.

Important property of the hexaacu ion

Aqueous NiCl ₂ solutions can absorb ammonia (NH ₃) rapidly. This is because NH ₃ easily binds to the hexaaquonickel ion ²⁺ displacing water molecules and forming species like ²⁺ or even ²⁺.

Obtaining

Nickel (II) chloride can be obtained starting from nickel (Ni) powder or nickel oxide (NiO).

Nickel can be chlorinated by passing chlorine gas (Cl ₂) over the powder.

Ni + Cl ₂ → NiCl ₂

You can also react NiO with hydrochloric acid HCl and then evaporate the solution.

NiO + 2 HCl → NiCl ₂ + H ₂ O

Applications

For plating metals with nickel

Nickel chloride is used in solutions that make it possible to electrodeposition metallic nickel on other metals. Electroplating uses electrical current to deposit one layer of the metal on top of the other.

Decorative metal finishes are made where nickel (Ni) is the intermediate layer before coating the piece with chrome metal (Cr). It is also suitable for coatings in engineering applications.

The shiny parts of some motorcycles are pre-coated with metallic nickel by NiCl ₂ treatment and then plated with chrome metal. Author: Hans Braxmeier. Source: Pixabay.

Nickel coatings are applied to zinc, steel, tin-nickel alloys and other metals to protect them from corrosion and erosion or abrasive wear.

In analysis laboratories

NiCl ₂ is part of solutions used for the preparation of cancer tissue samples to be viewed under the microscope by medical pathologists specializing in cancer.

In organic chemistry reactions

Nickel chloride acts as a catalyst or accelerator for many reactions between organic compounds. For example, it allows the union of rings such as phospholes, which dimerize (two phospholes join) in the presence of NiCl ₂.

It also serves as a catalyst in the production of CCl ₄ carbon tetrachloride and diarylamine.

NiCl ₂ serves as a catalyst in organic chemistry reactions. Author: WikimediaImages. Source: Pixabay.

In industrial safety

Due to its high affinity for ammonia (NH ₃), NiCl ₂ is used in industrial safety masks. Ammonia is a toxic gas. The nickel chloride is placed in the filters through which the air that the person inhales passes.

In this way the air with NH ₃ passes through the filter, the ammonia is trapped by the NiCl ₂, and the person wearing the mask inhales only pure air.

NiCl ₂ is used in gas masks to protect people from NH ₃ ammonia gas. Author: Michael Schwarzenberger. Source: Pixabay.

In thermal batteries

NiCl ₂ is a promising material for use in thermal batteries. In tests carried out with lithium-boron batteries where the cathode is NiCl _2, they show excellent performance.

Thermal Battery. The NiCl ₂ in these batteries makes them perform better. Thomas M. Crowley, Chief, Munitions Fuzing Branch, Fuze Division, US Army Armament Research, Development & Engineering Center (ARDEC), Picatinny Arsenal, NJ / Public domain. Source: Wikimedia Commons.

In sodium metal halide batteries

Researchers have shown that the nickel chloride in sodium-metal halide batteries allows operation at much lower temperatures than with other halides. Metal halides are salts of halogens such as chlorine, bromine, and iodine with metals.

This type of battery is very useful for storing electrical energy in a stationary way, but it is usually problematic due to the high operating temperatures and therefore little use.

NiCl ₂ can help lower the operating temperature of sodium metal halide batteries. Author: Clker-Free-Vector-Images. Pixabay.

With NiCl ₂ you can solve the problem of high temperatures in these batteries.

In various applications

Nickel chloride NiCl ₂ is an intermediate in the preparation of nickel catalysts. It also serves to obtain other compounds such as complex nickel salts.

Discontinued use

Due to its toxicity towards most microorganisms, NiCl ₂ can act as a fungicide and was formerly used to eliminate mold that attacks certain plants.

However, this use was discontinued due to the danger it represents for the people who use it and for the environment.

Risks

Nickel (II) chloride or nickel chloride NiCl ₂ is a very toxic compound. It is not flammable but produces dangerous gases when exposed to heat or fire.

Human exposure to nickel (II) chloride can cause severe dermatitis, skin allergies, respiratory allergies, affect the lungs, kidneys, gastrointestinal tract, and nervous system.

It is also known for its carcinogenic and mutagenic effects (causing changes in the genes of cells).

Effects on animals and aquatic organisms

It is very toxic to terrestrial and aquatic animals, with effects that last over time. It can be lethal in low concentrations.

Some researchers found for example that trout exposed to NiCl ₂ dissolved in water suffer from oxidative damage and various pathologies in their brain tissues.

Trout can be severely damaged by NiCl ₂ contamination of the waters where they live. Author: Holger Grybsch. Source: Pixabay.

NiCl ₂ must never be disposed of into the environment.

References

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