Sodium Bisulphate

It is majorly used in metal finishing and in cleaning products, like lowering the effective chlorination in swimming pools and hot tubs. In jewelry making, it is the primary ingredient used to remove the oxidation layer from surfaces and to restore glaze.

Synonyms: Sodium acid sulfate, Sodium hydrogen sulfate, Bisulfate of soda, NaHSO4, Nitre Cake, Sodium Acid Sulfate, Sodium Bisulfate
Chemical Formula: NaHSO4
CAS Number: 7681-38-1

Characteristics

Molar Weight: 120.06 g/mol

Melting Point: 150 °C

Boiling Point: 315 °C

Density: 2.74 g/cc

Forms: Off-White, Solid

Uses and applications

Key applications

Water treatment
Cleaning products
Polishing and cleaning
Pulp and paper
Catalysts
Solvents
Agricultural (non-pesticide)
Bleaching agent
Paint and Coatings

Industries

General information about Sodium Bisulphate

Sodium Bisulphate (Na2S2O7), also known as sodium pyrosulphate, is the disodium salt of disulphuric acid (H2S2O7). It is mainly used in industry as an oxidising agent and pH regulator and is considered a safe alternative to sulphuric acid, as it is available in powder form.

The salt does not occur in nature in its pure form because it is highly reactive. It absorbs moisture from the air and easily hydrolyses to sodium bisulphate (NaHSO4) or sulphuric acid (H2SO4).

Properties of Sodium Bisulphate

Sodium Bisulphate is a colourless, crystalline solid produced by heating sodium bisulphate (NaHSO4). At temperatures around 300 °C, dehydration occurs, whereby water is split off and Sodium Bisulphate is formed as a white powder.

Sodium Bisulphate in water treatment

Sodium Bisulphate is used in water treatment to lower the pH value. It dissolves in water and forms sodium bisulphate, which then reacts further to form sulphuric acid. This makes the water more acidic and lowers excessive pH values in a controlled manner. Areas of application include:

Cooling tower systems: Prevents limescale deposits and microbiological growth
Industrial piping: Removal of iron, manganese and metal oxide deposits
Process water: Regulation of the acid-base balance
Wastewater treatment: Neutralisation of alkaline wastewater

Thanks to these versatile functions, Sodium Bisulphate contributes to increased efficiency and system maintenance in industrial water systems.

Sodium Bisulphate in industrial chemistry

In industrial chemistry, Sodium Bisulphate serves as an intermediate product in the manufacture of sulphate compounds, in particular sodium bisulphate, which is used in cleaning agents and technical processes. It also functions as:

An oxidising agent in organic and inorganic reactions
A dehydrating agent in organic synthesis
pH regulator and reaction accelerator, as it forms sulphuric acid in aqueous solution

These properties make Sodium Bisulphate an important agent in process and synthetic chemistry.

Sodium Bisulphate in analytical chemistry

In analytical chemistry, Sodium Bisulphate is often used as a dehydrating agent to remove water from samples and solvents. It is also used in:

Redox reactions for determining chemical substances
Acid-base titrations for lowering pH
Removing metal ions or metal oxides from samples
Determining the water content in analytical materials

Its oxidising and hygroscopic effect makes Sodium Bisulphate a versatile analytical aid.

Sodium Bisulphate in the cleaning industry

In the cleaning industry, Sodium Bisulphate is used as a component in descalers and industrial cleaning agents. By forming sulphuric acid, it dissolves limescale deposits, rust and mineral residues. Typical applications are:

Descalers for household appliances (e.g. coffee machines)
Industrial sanitary cleaners
Cleaning agents for swimming pools
Special cleaners for glass and stainless steel

It also acts as a pH reducer to stabilise cleaning formulations.

Sodium Bisulphate in the textile and leather industry

In the textile industry, Sodium Bisulphate is used as a mordant in dyeing. The acidic environment created by its hydrolysis improves the adhesion of the dyes to the fibres. It is also used to remove excess dye in order to achieve uniform colouring. Other applications include:

Dechlorination after bleaching: neutralises chlorine residues to prevent fibre damage
Leather treatment: Removes calcium residues and lowers the pH value for better chrome absorption
Bleaching processes: Lightening of leather and removal of colour casts

Steel parts for industrial machinery round shape. Black and white toning. Close up.

Sodium Bisulphate in metal processing

In metal processing, Sodium Bisulphate is used as a pickling agent. The resulting sulphuric acid removes oxide layers, rust and impurities from metal surfaces. This prepares the surface for subsequent steps such as welding, galvanising, electroplating or painting.

Sodium Bisulphate is also used to clean precious metals (e.g. gold, silver, platinum) and to clean machine components after metalworking.

Further areas of application

Sodium Bisulphate in the cosmetics industry

In the cosmetics industry, Sodium Bisulphate is used as a cleaning agent and surfactant. It has an oxidising effect and removes grease, dirt and dead skin cells. Applications include:

Shampoos, shower gels and facial cleansers: cleansing and pH regulation
Exfoliating and anti-ageing products: chemical peeling for skin renewal
Hair dyes and lighteners: oxidising agent for dye activation
Hair treatments: pH stabilisation and formulation protection

Sodium Bisulphate in the pharmaceutical industry

In the pharmaceutical industry, Sodium Bisulphate serves as an oxidising agent in chemical reactions for the synthesis of active ingredients. Thanks to its hygroscopic properties, it is also used as a drying agent. Other pharmaceutical applications:

pH regulator and preservative in tablets, ointments and injection solutions
Stabiliser for chemical formulations
Component of analytical reagents and test substances in quality control

Sodium Bisulphate in the construction industry

In construction chemistry, Sodium Bisulphate is used for cleaning and pickling metal surfaces. It removes oxide layers and rust from steel girders, pipes or iron structures, thereby improving the adhesion of coatings. Other applications:

Control of the sulphate content in concrete and cement to prevent material weakening
Optimisation of cement quality and strength
Cleaning processes on construction sites: removal of stains and discolouration on tiles, bricks and stone surfaces

Its oxidising effect helps to reliably remove rust and dirt discolouration.

Summary

Sodium Bisulphate (sodium pyrosulphate) is a versatile inorganic salt with applications in water treatment, chemistry, cleaning, textile and leather processing, metalworking, cosmetics, pharmaceuticals and the construction industry. Its oxidising and acidic properties make it an efficient pH regulator, reagent and cleaning agent for numerous industrial processes.

Its stable powder form makes it significantly safer and easier to handle in technical practice than liquid acids such as sulphuric acid.