How Is Nickel Sulfate Produced and What Are Its Main Uses?
Nickel Sulfate is a crystalline inorganic compound that is yellow, green or blue coloured and produces toxic gasses upon heating. It is used in electroplating and as a chemical intermediate to produce other types of nickel compounds. Nickel Sulfate is a by-product of copper refining and it naturally occurs as a rare mineral which is retgersite. Retgersite is a type of chemical that is useful in utensils, jewellery, coins, metal buttons, and eyeglasses. Nickel Sulfate is also used for making paper clips, keys, enamel dyes, and electrical wiring. Nickel Sulfate hexahydrate is also known as blue salt. And it may be produced by the dissolution of nickel metal or nickel oxides in the sulfuric acid.
What is Nickel Sulfate?
Nickel sulfate or Nickel (II) sulfate is an inorganic compound. It is highly soluble in aqueous solutions.
This sulfate compound is a green coloured salt or ester of sulphuric acid.
It is formed by replacing one or both hydrogen atoms with Nickel (metal) atoms.
The chemical formula for Nickel Sulfate is NiSO4.
Nickel (II) Sulfate is available naturally in the form of mineral morenosite. It is usually unstable in the air.
It is also called,
Nickel (II) Sulfate,
Nickel monosulphate,
Nickelous Sulfate.
Nickel Sulfate hexahydrate.
Nickel (2+) Sulfate.
Nickel Sulfate can be formed in laboratories by dissolving Nickel oxide in Sulphuric acid. The reaction gives a concentrated solution of Nickel Sulfate Heptahydrate. On heating the concentrated solution, crystalline Nickel Sulfate hexahydrate is derived for commercial use.
It is a carcinogenic compound as exposure to its fumes can cause cancer.
Production of Nickel Sulfate
The production of Nickel Sulfate includes: It is made by dissolving nickel oxide in hot, dilute sulfuric acid. Nickel is basically delivered in a sealed reactor, with a sulphuric acid solution. This sealed reactor is then filled with oxygen. The temperature and the amount of pressure in the sealed reactor are kept constant during the whole operation. The oxidation process produces concentrated Nickel Sulfate solution in an enclosed environment. After heating and increasing the pressure in the sealed reactor, it results in the formation of blue crystalline Nickel Sulfate. The impurities of it are then removed from the crystals by treating them with a diluted solution of Barium carbonate. And this whole method is widely used to produce Nickel Sulfate in large quantities.
The Nickel Sulfate is usually prepared by dissolving nickel oxide into hot, dilute Sulphuric acid. The general steps involved in the process are,
The metal, Nickel, is supplied in an enclosed reactor along with Sulphuric acid solution.
Oxygen is introduced into the reactor.
During this process, temperature and pressure in the reactor are kept constant.
In an enclosed environment, the chemical process (oxidation) gives rise to concentrated Nickel Sulfate solution.
On further heating and increasing the pressure in the reactor, blue crystalline Nickel Sulfate is formed.
By treating the crystals with a diluted solution of Barium carbonate, elimination of impurities takes place.
This process is widely used for the mass production of Nickel Sulfate.
Physical Properties of NiSO4
It occurs in yellow solid when in anhydrous form, green-blue crystals when in heptahydrate form and in blue crystals when in hexahydrate state.
It is odourless.
Its molecular weight is 154.75 g/mol.
It is having a density of 3.68 g/cm3
Its boiling point is 840 °C
Its Melting point is > 100 °C in an anhydrous state and >53 °C for hexahydrate form.
The linear chemical formula is given as NiSO4(H2O)6.
It is soluble in water and methanol. Solubility in water is 293 g/L at 0°C.
Its CAS registration number is 7786-81-4.
Though it has a sweet, astringent taste, it is recommended not to taste.
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Nickel Sulfate is a yellow solid when it is anhydrous, Nickel Sulfate is a green-blue crystal when it is heptahydrate, and Nickel Sulfate is a blue crystal when it is hexahydrate.
Nickel Sulfate’s weight is 3.68 g/cm3 and its density is 3.68 g/cm3.
Nickel Sulfate’s molecular mass is 154.75 g/mol.
Nickel Sulfate’s boiling point is 840 degrees Celsius.
Nickel Sulfate is odourless.
Nickel Sulfate’s melting point is more than 100 °C in anhydrous form and more than 53 °C in hexahydrate form.
Chemical Properties of NiSO4
It is non-flammable.
It is insoluble in alcohol and ether.
It is not compatible with strong acids.
After dissolving in water, it forms an acidic corrosive solution. On corrosion, it emits fumes of oxides of sulfur.
When it is dissolved in water, and the solution is heated to decompose, it liberates fumes of nitrous oxide. Fumes of Nickel Sulphate are highly toxic.
As its aqueous solution is acidic, the pH value is 4.5.
On heating at 103°C, aqueous Nickel Sulfate loses the water molecules. And heating up to 848°C, the anhydrous form decomposes to form sulfur trioxide and nickel oxide. The chemical expression is
\[ NiSO_{4} \rightarrow NiO + SO_{3} \]
Nickel Sulfate gives double by-products of salts on reacting with alkali metals or ammonium sulfates. These sulfates are isomorphous.
Reacting with hydrochloric acid gives Sulphuric acid and Nickel Chloride. The chemical reaction is as shown,
\[ NiSO_{4} + HCl \rightarrow NiCl + HSO_{4} \]
While reacting with sodium hydroxide, it forms Sodium Sulfate and Nickel hydroxide. The chemical equation is
\[ NiSO_{4} + NaOH \rightarrow Ni(OH)_{2} + Na_{2}SO_{4} \]
Nickel Sulfate is non-combustible.
Nickel Sulfate has a pH value of 4.5 because its aqueous solution is of acidic nature.
Nickel Sulfate is incompatible with strong acids.
Nickel Sulfate generates an acidic corrosive solution when dissolving in water, producing sulfur dioxide emissions when it corrodes.
Alcohol and ether do not dissolve in Nickel Sulfate.
Nickel Sulfate is dissolved in water and the solution is heated to decompose, nitrous oxide emissions are released and its fumes are extremely poisonous.
Uses of Nickel Sulfate
Nickel Sulfate is widely used
As the electrolyte for surface finishing processes of metals such as metal plating and electrorefining.
In the preparations of many Nickel catalysts and compounds.
As a reducing agent for flashing on steel surfaces, imparting Nickel coating from the surface.
For blackening Brass and Zinc.
As a mordant in dyeing and printing metals, textiles and ceramics.
As a coating for many metals.
In the production of driers that are used in protective shields.
They are occasionally used as calibrants to measure magnetic susceptibility.
Nickel sulfate is used as an electrolyte in metal surface finishing operations like plating and electrorefining.
Nickel sulfate is also used as a protective layer for a variety of metals.
Different types of Nickel catalysts and compounds are made by this process.
Brass and zinc can be blackened with Nickel sulfate.
Various Metals, fabrics, and pottery are dyed and printed with Nickel sulfate as a mordant.
Nickel sulfate is used as a flashing reducer on steel surfaces, providing a nickel covering to the surface.
Effects of NiSO4 on Human Health
Nickel Sulfate can be assimilated into the human body by inhalation or ingestion. Once it is absorbed in the body, it concentrates in the lungs, gut, kidneys and liver. Exposure to NiSO4 causes :
Skin irritations
Giddiness
Lassitude
Headache
Myalgia
Gastrointestinal effects such as abdominal pain, nausea, vomiting, diarrhoea
Hemorrhagic gastritis
Transient hyperbilirubinemia and albuminuria
Bronchial asthma
Dyspnoea
Mild cyanosis
Chronic obstructive airways syndrome
Chronic urticaria
Dermatitis
Effects of Nickel Sulfate
Effects of Nickel Sulfate Include: Nickel sulfate can be incorporated into the human body by inhaling or ingesting it. Nickel sulfate concentrates in the lungs, intestines, kidneys, and liver once it is taken into the body. Nickel sulfate causes poisoning by being exposed to it. Nickel Sulfate causes Chronic obstructive pulmonary disease, Dyspnoea, Mild cyanosis, Chronic urticaria, Dermatitis. Nickel Sulfate also causes Irritation of the skin, giddiness, lassitude, headache, myalgia, abdominal pain, nausea, vomiting, diarrhoea, hemorrhagic gastritis, transient hyperbilirubinemia, and albuminuria are some of the gastrointestinal side effects.
FAQs on Nickel Sulfate: Properties, Preparation, and Applications
1. What is Nickel(II) Sulfate and what is its chemical formula?
Nickel(II) Sulfate, also known as nickelous sulfate, is an inorganic chemical compound. It is typically obtained as a byproduct of copper refining. The most common form is its hexahydrate, with the chemical formula NiSO₄·6H₂O. The anhydrous (water-free) form has the formula NiSO₄. It is a key source of the Ni²⁺ ion for various chemical syntheses and applications.
2. What are the key physical properties of Nickel(II) Sulfate?
The physical properties of Nickel(II) Sulfate vary based on its hydration state. Key properties include:
- Appearance: The anhydrous form (NiSO₄) is a yellow-green crystalline solid, while the common hexahydrate (NiSO₄·6H₂O) is a blue to emerald-green crystalline solid.
- Solubility: It is highly soluble in water and methanol but insoluble in ethanol and ether.
- Odour: Nickel(II) Sulfate is an odourless compound.
- Melting and Boiling Points: The anhydrous form decomposes at 848°C without boiling. The hexahydrate loses its water molecules upon heating above 53°C.
3. How is Nickel(II) Sulfate typically prepared in a laboratory?
Nickel(II) Sulfate can be prepared by reacting materials containing nickel with sulfuric acid. A common laboratory method involves the dissolution of nickel metal, nickel(II) oxide, or nickel(II) carbonate in dilute sulfuric acid. For example, reacting nickel(II) oxide with sulfuric acid yields Nickel(II) Sulfate and water, as shown in the equation: NiO + H₂SO₄ → NiSO₄ + H₂O. The resulting solution is then crystallized to obtain the hydrated salt.
4. What are the major industrial applications of Nickel(II) Sulfate?
Nickel(II) Sulfate has several important industrial applications, primarily related to surface coating and chemical manufacturing. Its main uses include:
- Electroplating: It is the principal electrolyte used in nickel plating baths to provide a protective and decorative coating on metals.
- Catalyst Production: It serves as a precursor in the manufacturing of various nickel-based catalysts used in hydrogenation processes.
- Battery Manufacturing: It is a key component in the cathode materials for lithium-ion batteries, particularly in nickel-manganese-cobalt (NMC) and nickel-cobalt-aluminium (NCA) types.
- Mordant in Dyeing: It is used as a mordant in the textile dyeing and printing industry to help fix dyes to fabrics.
5. What safety precautions are essential when handling Nickel(II) Sulfate?
Due to its toxicity and classification as a potential carcinogen, strict safety measures are required. Key precautions include:
- Wearing appropriate Personal Protective Equipment (PPE), such as gloves, safety goggles, and lab coats.
- Handling the compound in a well-ventilated area or under a fume hood to avoid inhaling its dust.
- Storing it in a cool, dry place away from incompatible substances like strong oxidizing agents.
- Avoiding direct contact with skin and eyes, as it can cause significant irritation and allergic reactions (nickel dermatitis).
6. Why does an aqueous solution of Nickel(II) Sulfate appear green?
The characteristic green colour of an aqueous Nickel(II) Sulfate solution is due to the presence of the hexa-aqua-nickel(II) ion, [Ni(H₂O)₆]²⁺. In this complex ion, the nickel atom is in the +2 oxidation state and has a d⁸ electron configuration. The water molecules act as ligands, causing the d-orbitals to split. The ion absorbs light in the red part of the visible spectrum to promote electrons between these split d-orbitals (a process called d-d transition), and the complementary colour, green, is transmitted, which is what we see.
7. How does the +2 oxidation state of nickel in NiSO₄ influence its chemical behaviour?
The +2 oxidation state is the most stable and common state for nickel. In NiSO₄, this state dictates its primary chemical properties. It allows nickel to form stable ionic compounds and coordinate complexes, such as the [Ni(H₂O)₆]²⁺ ion in solution. This stable divalent state is crucial for its role in electroplating, where Ni²⁺ ions are easily reduced to nickel metal (Ni) at the cathode. Its tendency to form complexes also makes it a useful precursor for creating various nickel-based catalysts.
8. What happens when Nickel(II) Sulfate is heated strongly, and what type of reaction is this?
When anhydrous Nickel(II) Sulfate (NiSO₄) is heated to a high temperature (above 840°C), it undergoes thermal decomposition. This is a chemical reaction where a single compound breaks down into two or more simpler substances due to heat. In this case, NiSO₄ decomposes to form nickel(II) oxide (NiO), a green solid, and sulfur trioxide (SO₃), a colourless gas. The balanced chemical equation for this reaction is: NiSO₄(s) → NiO(s) + SO₃(g).
9. Compare the role of Nickel(II) Sulfate in electroplating versus its role in battery technology.
While both applications utilize the nickel ion, its function is different.
- In Electroplating: Nickel(II) Sulfate provides a source of Ni²⁺ ions that are reduced to form a metallic nickel (Ni⁰) layer on an object. Here, the goal is to deposit a stable, non-reactive metal coating. The process is a direct application of redox chemistry at the electrode surface.
- In Battery Technology: It acts as a precursor material for synthesizing the cathode, such as in NMC (Nickel Manganese Cobalt) batteries. The nickel in the cathode remains in an oxidized state (like Ni²⁺ or Ni³⁺) and facilitates the intercalation and deintercalation of lithium ions during the charge-discharge cycle. Its role is to enable reversible electrochemical energy storage, not to be permanently reduced to metal.
