Where to Buy Sulphuric Acid: Grades, Concentrations and Bulk Supply

The short answer

Sulphuric acid is a bulk industrial commodity, not a retail product. It is bought through three channels, and the grade you need decides which one applies:

• Acid producers — sulphur-burning contact plants, smelter-acid units and fertiliser complexes, selling by road tanker, rail tanker or ISO tank.
• Chemical distributors — carboys, drums and IBCs, released against a trade account and an end-use declaration.
• Merchant exporters — consolidating producer material, matching grade to application, arranging packing, dangerous goods documentation and shipping for overseas buyers.

The material: formula H₂SO₄, CAS 7664-93-9, molecular weight 98.08. It is produced industrially by the Contact Process, in which sulphur or a sulphide feed is burned to sulphur dioxide, catalytically oxidised to sulphur trioxide over vanadium pentoxide, and absorbed into circulating acid. Every commercial grade below comes from that route.

The query is often typed as "where to buy sulfuric acid" with the US spelling. Same substance, same specifications, same UN classification.

Formula, properties and identifiers

Before the commercial questions, the reference numbers people look up. Sulphuric acid is H₂SO₄, CAS 7664-93-9, molecular weight 98.08 g/mol. Concentrated 98 % acid has a density of about 1.84 g/cm³ — nearly twice that of water, which is why a drum feels far heavier than its volume suggests.

Three properties explain most of its behaviour, and all three are why it is handled the way it is.

• It is a strong diprotic acid. The first proton comes off completely; the second has a pK_a of about 2. That gives two acid equivalents per molecule, so a tonne of sulphuric acid neutralises considerably more alkali than a tonne of hydrochloric acid.
• It is a dehydrating agent. Concentrated acid strips hydrogen and oxygen out of organic matter as water, which is why it chars sugar, paper and skin. This is a different and more damaging mechanism than simple acid burn, and it is the reason the safety case is written around contact time rather than concentration alone.
• Dilution is strongly exothermic. Mixing acid and water releases a great deal of heat, enough to boil the mixture and eject it from the vessel. Always add acid to water, slowly, with stirring and cooling — never the reverse.

Sulphuric acid is made by the contact process: sulphur is burned to sulphur dioxide, oxidised over a vanadium pentoxide catalyst to sulphur trioxide, and the trioxide is absorbed into existing 98 % acid rather than into water, because absorption into water produces an unmanageable mist. Dissolving extra sulphur trioxide in the acid gives oleum, quoted either as percent free SO₃ or as its H₂SO₄ equivalent above 100 %.

It is produced in greater tonnage than any other manufactured chemical, which is why national sulphuric acid output has long been used as a rough index of industrial activity.

Why supply is controlled

Sulphuric acid is corrosive at strength, and it has been misused both in assaults and as a precursor in illicit manufacture. Most jurisdictions therefore restrict its sale to the general public while leaving industrial and institutional supply open.

If you are a private individual looking for a place to buy it, the accurate answer is that there is no ordinary retail channel. Small quantities move through laboratory and industrial distributors, and they are released against a business or institutional account, a stated end use, delivery to a registered address, and in some jurisdictions a licence. Suppliers are commonly required to record transactions and report suspicious enquiries to law enforcement. That is the position across most of Europe, the UK, India and a growing number of other markets, and it is not negotiable at the counter.

For an industrial buyer, the practical expectations are consistent regardless of market:

• Registered company or institution details, with tax and trade registration
• A written end-use statement naming the process the acid feeds
• Delivery to a commercial site with appropriate storage
• Evidence of handling capability — bunding, PPE, trained personnel
• Copies of any storage, poisons or precursor licences the destination requires
• A named authorised recipient for the consignment

Regulatory detail varies. Regimes such as the EU explosives-precursors regulation, the UK poisons and precursors framework, state-level poison rules in India, and various national licensing schemes each set their own concentration thresholds and licence categories, and those thresholds change. Confirm the current position for your destination with your own compliance function or customs broker before ordering.

Grades and concentrations

Sulphuric acid is sold across a wide concentration range, and separately across a purity range. Confusing the two is the most common specification error in enquiries.

Figures above are indicative of what the market commonly supplies. Where a formal standard applies — a national sulphuric acid specification, a battery-acid standard, a pharmacopoeial or food-chemical monograph, or an ACS reagent specification — that document, not a general table, defines the acceptance limits. Ask for the standard by name in your enquiry.

Battery grade is a purity specification, not a concentration

This is worth stating plainly because it drives a large share of mis-specified orders. Battery grade sulphuric acid is usually about 98% assay, the same nominal strength as ordinary technical acid. What separates it is contamination.

In a lead-acid cell, iron catalyses self-discharge and accelerates grid corrosion. Chloride attacks the lead grid and can liberate chlorine at the positive plate. Manganese, antimony, copper and nickel raise hydrogen evolution and shorten cycle life. So battery grade is defined by low-ppm ceilings on those species, by low residue on ignition, and by the absence of organics and colour. It is also supplied pre-diluted to electrolyte strength, typically in the 33–37% band with a specific gravity target, made up in demineralised water.

If you order "98% sulphuric acid" for a battery plant, you may receive perfectly compliant technical acid that ruins your cells. Specify the purity standard, not the number.

Oleum

Oleum is sulphur trioxide dissolved in sulphuric acid, quoted by free SO₃ content — 20%, 23%, 25% and 65% are common trade grades. It is used where water cannot be tolerated in a reaction, principally sulphonation and the preparation of nitrating mixtures. It fumes in moist air, is more aggressive than concentrated acid, and several grades have freezing points close to or above winter ambient, so tanks and lines are insulated and heat-traced. Oleum is a materially different handling proposition from 98% acid and should be enquired for separately.

What it is used for

Fertiliser is by a wide margin the largest global outlet. Sulphuric acid attacks phosphate rock to make phosphoric acid, which in turn feeds DAP, MAP and NPKs; direct acidulation gives single superphosphate. Fertiliser plants buy technical grade in tanker and ISO tank volumes.

Lead-acid batteries consume battery grade acid as electrolyte, both as 98% for on-site dilution and as ready-made electrolyte.

Metal pickling and steel processing use dilute acid to strip scale from carbon steel before rolling, coating or galvanising, and in electrowinning and copper leaching.

Petroleum refining uses concentrated acid as the alkylation catalyst producing high-octane gasoline blendstock, and in various treating steps. Spent acid is regenerated.

Pulp and paper uses it for pH control, tall oil splitting, chlorine dioxide generation and in sulphite pulping chemistry.

Water and effluent treatment uses dilute acid for pH correction, ion-exchange resin regeneration and alkalinity control.

Dyes and pigments use acid and oleum for sulphonation of aromatic intermediates and in titanium dioxide production by the sulphate route.

Pharmaceutical manufacture uses high-purity acid in intermediate synthesis, salt formation and pH adjustment, against pharmacopoeial specifications.

Detergents use oleum or SO₃ to sulphonate linear alkylbenzene into LAS surfactant.

Handling, storage and materials of construction

Dilution

Always add acid to water, slowly, with stirring and cooling. Never add water to concentrated acid.

The reason is thermal. Dilution releases a large amount of heat. Adding a small volume of water to a large volume of concentrated acid puts that heat into a thin layer at the surface, where the water — less dense than the acid and sitting on top — can flash to steam and eject acid from the vessel. Adding acid into a larger bulk of water spreads the same heat through a much greater thermal mass, so the temperature rise is manageable.

Reactivity

Concentrated sulphuric acid is a powerful dehydrating agent. It chars sugars, cellulose, paper and wood by stripping hydrogen and oxygen as water. Hot concentrated acid is also an oxidiser and will attack copper and other metals it does not touch when cold.

Keep it away from: water added incorrectly; bases and carbonates (violent neutralisation); chlorates, perchlorates, permanganates and peroxides; nitric acid and nitrates unless deliberately blending nitrating mixtures under controlled conditions; cyanides and sulphides, which liberate toxic gas; metal powders; carbides; and combustible organics.

Dilute acid in contact with steel, zinc or aluminium evolves hydrogen. In a closed tank this builds a flammable headspace. Vent it, bond and earth transfer equipment, and prohibit hot work on acid vessels without gas testing.

Materials of construction

There is a point here that surprises people new to the material: dilute sulphuric acid is more corrosive to carbon steel than concentrated acid is. At roughly 93% and above, at ambient temperature and low velocity, the acid forms a protective iron sulphate film on steel, and plain carbon steel tanks are standard. Break that film with high flow velocity, elevated temperature or dilution — including dilution by rainwater or condensate ingress at a vent — and corrosion accelerates sharply.

Practical guidance:

• 93–98% at ambient, low velocity: carbon steel tanks, with velocity and temperature limits observed
• Above ambient temperature or higher velocity: high-silicon cast iron, Alloy 20, or proprietary high-alloy acid-service steels
• Dilute, roughly 10–70%: rubber-lined steel, FRP with an appropriate corrosion barrier, PVDF, PTFE-lined, HDPE and PP for small vessels, or nickel alloys
• Gaskets and seals: PTFE
• Valves and instruments: PTFE-lined or fully fluoropolymer wetted parts
• Oleum: carbon steel, insulated and traced to stay above the grade's freezing point

Store in bunded areas sized for the largest vessel, away from water lines, drains and incompatible stock. Keep vents fitted with drying arrangements to exclude moisture.

PPE, spill and first aid

Chemical splash goggles with a face shield, acid-resistant gloves, an acid-resistant suit or apron, and boots. Respiratory protection where mists or oleum fumes are possible. Safety shower and eyewash within immediate reach of every transfer point, tested and unobstructed.

For spills, the principle is: evacuate and ventilate, stop the source if safe, contain, and neutralise small quantities with soda ash or lime before absorbing with inert material. Do not direct a water jet into a pool of concentrated acid — the heat release and spattering make it worse.

For exposure, the principle is: flush immediately and continuously with large volumes of water for at least 15 to 20 minutes, remove contaminated clothing under the water, and get medical attention. Do not attempt to neutralise acid on skin or in the eye. Follow Section 4 of the supplier's safety data sheet, and have that SDS available at the point of use before the first drum arrives.

Transport classification and documents

Confirm the entry against the current edition of the applicable modal regulations — IMDG for sea, ADR for European road, and the relevant national rules — before booking. Air movement of corrosive acids is heavily restricted and is not a practical channel for commercial quantities.

Common packing formats are 25 to 35 kg HDPE carboys, 250 kg HDPE drums, IBCs, rubber-lined or steel road tankers, and ISO tanks. Note that 98% acid has a density near 1.84 g/cm³, so a nominal 1,000 litre IBC would hold well over 1.8 tonnes at full volume; fill limits and IBC suitability for this service must be confirmed with the packer rather than assumed.

Sulphuric acid and oleum fall under HS heading 2807, with national sub-headings splitting the two. Verify the exact eight-digit code with your customs broker for both origin and destination.

An export consignment should carry: commercial invoice and packing list; a batch-specific certificate of analysis against the agreed specification; a 16-section GHS safety data sheet in the destination language where required; a dangerous goods declaration and container packing certificate; bill of lading; certificate of origin; and any end-use declaration, import permit, precursor licence copy or destination-country registration evidence the consignee is obliged to hold.

How to buy properly

What to put in an enquiry

A quotable enquiry states:

• Grade and governing standard — not "98%" alone, but the standard or monograph you are buying against
• Assay and the impurity limits that matter to your process — iron, chloride, heavy metals, residue on ignition, colour
• Quantity per shipment and expected annual offtake
• Packing — carboy, drum, IBC, ISO tank — and whether pallets need to be export-treated
• Destination port or delivery address, and Incoterms
• Documentation required — CoA scope, SDS language, certificate of origin type, any pre-shipment inspection
• Any import licence or precursor registration the destination imposes, and who holds it

Comparing quotes

Compare on delivered cost against an identical specification, not on headline price per tonne. Two quotes for "sulphuric acid 98%" are not comparable if one is battery grade and one is not. Check what the certificate of analysis actually reports — a CoA that omits the impurities your process cares about is not evidence of compliance. Confirm the packing is UN-marked and rated for the material, and that the supplier can produce the dangerous goods paperwork without a delay at the port.

Which channel to use

• Litres, for laboratory or QC use: laboratory chemical suppliers, in glass or PP bottles, against an institutional account
• Drums and IBCs, for pilot plant or moderate consumption: regional chemical distributors
• Tankers, ISO tanks and containerised drum loads, for production: acid producers directly, or merchant exporters where the buyer is overseas and needs grade selection, packing, documentation and shipping handled as one package

Enquire with a specification

Sulphuric acid and oleum are supplied by Scapex Exports from qualified Indian manufacturers, in packing formats and grades matched to the buyer's specification, with certificate of analysis, safety data sheet and full export documentation.

Send your grade, standard, impurity limits, quantity, packing preference and destination, and you will get a quotation against that specification rather than a generic one.

Frequently asked questions