Oleum 65%
Oleum is sulfuric acid with extra sulfur trioxide dissolved into it — more sulfonating power packed into the same drum. At 65% free SO₃ (roughly 114.6% H₂SO₄ equivalent) it sits at the high-strength end of the commercial range, giving a faster, cleaner sulfonation than 98% acid for the same batch time.
Chelora Chemicals supplies 65% oleum to detergent, dye, pharmaceutical and agrochemical plants worldwide, moved as Class 8 corrosive cargo in acid-duty tankers and UN-approved drums, with a batch COA and GHS safety data sheet on every consignment.
Product identity
- CAS Number
- 8014-95-7
- IUPAC name
- Sulfuric acid, fuming
- Composition
- H₂SO₄ + 65% free SO₃
- H₂SO₄ equivalent
- ≈ 114.6%
- EC / EINECS
- 231-639-5 (H2SO4)
- UN Number
- 1831 · Class 8
- Appearance
- Colorless to brownish, fuming
- HS Code
- 2807 00*
* Confirm the exact HS heading with your customs broker — oleum sits under the same general heading as sulfuric acid in most tariff schedules, but some destinations classify it separately by SO₃ content.
What Oleum 65% is used for
Oleum 65% is a dense, colorless-to-brownish fuming liquid that releases visible SO₃ mist the moment it meets moist air. The extra sulfur trioxide is what plants are actually buying — it is the active sulfonating species, and 65% strength delivers more of it per tonne shipped than lower grades.
Its single largest use is sulfonation: linear alkylbenzene (LAB) for detergents, aromatic sulfonic acids for dyes and optical brighteners, and sulfonated intermediates for agrochemicals and pharmaceuticals. A second major stream is as the sulfuric-acid component of mixed nitrating acid, where the extra SO₃ absorbs the water generated by nitration and keeps the nitric acid concentrated enough to react efficiently.
Strength grades we supply
- Oleum 65% (this product) the standard high-strength grade for LAB sulfonation and mixed-acid nitration.
- Oleum 20% / 23% lower free-SO₃ grades for milder sulfonation and acid-plant blending; ask for the matching page.
- 98% Sulfuric acid the feedstock oleum is made from, and the acid used when fuming strength is not required.
- Chlorosulfonic acid a step beyond oleum in reactivity — used when sulfonation must also chlorinate. See that page.
State the free-SO₃ percentage on every purchase order — see the full acid and sulfonating-agent range.
Appearance and handling character
The material ships as a dense, oily, fuming liquid, colorless when fresh and darkening to brown with age or iron contamination. It reacts violently and exothermically with water, generating heat and SO₃/H2SO4 mist — acid is always added to water, never the reverse. The safety section below should be read before any handling is planned.
| Parameter | Typical value |
|---|---|
| Appearance | Colorless to brownish, fuming liquid |
| Free SO₃ (acidimetric) | 64 – 66% |
| H₂SO₄ equivalent | 114 – 115% |
| Iron (as Fe) | Reported per batch |
| Color / APHA | Reported per batch |
| Arsenic | Trace, reported per batch |
Important: the figures above are indicative of commercial-grade material and are offered for planning only. The batch certificate of analysis is the governing document. Free-SO₃ content is the figure that decides reaction yield — tell us your target and we will quote against it rather than against a generic grade.
| Property | Value |
|---|---|
| Physical state | Dense fuming liquid at ambient |
| Freezing point | ≈ 1 °C (65% SO₃ eutectic) |
| Decomposition / fuming | Evolves SO₃ continuously in air |
| Density | ≈ 1.99 g/cm³ @ 20 °C |
| Vapor pressure (SO₃) | ≈ 105 hPa @ 20 °C |
| Water solubility | Miscible — violently exothermic |
| Corrosivity | Severely corrosive to metals and tissue |
Physical constants compiled from public reference data for CAS 8014-95-7 and rounded for readability. Treat them as orientation, not as a specification.
Where our customers put this acid to work
Oleum 65% is bought for one property: the free SO₃ it carries. Everything below is a way of spending that SO₃.
Detergent alkylate sulfonation
Continuous-film sulfonation of linear alkylbenzene (LAB) to LAS, the workhorse surfactant in laundry and dish detergents, where oleum strength sets conversion and color.
- LAB / LAS sulfonation plants
- Film and falling-film reactors
- See our acid range
Dye & optical-brightener sulfonation
Aromatic rings are sulfonated to build water-solubility into dye intermediates and fluorescent whitening agents, where oleum strength controls mono- vs di-sulfonation.
- Dye intermediate manufacture
- Optical brightener precursors
- Batch kettle sulfonation
Mixed-acid nitration component
Blended with concentrated nitric acid, the free SO₃ absorbs water of reaction and keeps nitric acid active — the standard route to nitroaromatics and nitrate esters.
- Nitroaromatic intermediates
- Water-sink role in mixed acid
- Technical desk review of your ratio
Agrochemical & pharma intermediates
Sulfonation and sulfation steps in several agrochemical and active-pharmaceutical-ingredient routes draw on oleum where a plain 98% acid is too weak to convert fully.
- End-use declaration required
- Custom concentration on request
- Technical support for your route
Petroleum & refinery processing
Alkylate treating and selected refinery acid-treatment steps use oleum's SO₃ excess where sulfuric acid alone would dilute out before the reaction completes.
- Refinery-grade documentation
- Bulk tanker delivery available
- Contract supply programmes
Contract & scheduled supply
Continuous sulfonation plants consume oleum by the tanker-load on a fixed schedule. We hold inventory and release it against your production calendar.
- Annual contracts with scheduled call-off
- Price held across the contract period
- Second source held in reserve
How we supply Oleum 65%
Chelora Chemicals is a supplier and sourcing partner, not a manufacturer. On a corrosive, fuming acid where tanker compatibility and iron content both matter, owning no plant means we can route your order to the acid plant whose SO₃ strength and cleanliness actually matches your sulfonation line.
We place your order with whichever qualified producer best matches your assay, your specification, your price point and your delivery window.
We keep a second qualified source on this line. When a plant goes down for maintenance, your order switches source rather than stalling.
- Free-SO₃ confirmed before we quote. 64–66% is the commercial band — we state the exact figure on the COA rather than a generic "oleum" description.
- Iron and color reported, not averaged. Both affect downstream product color, so they appear as their own COA lines.
- Batch COA shared before dispatch. You approve free-SO₃, iron and appearance against your own spec while the tanker is still at our terminal.
- Corrosivity stated up front. Severely corrosive by all routes — we say so at enquiry stage so your EHS and logistics teams can plan loading arms and PPE.
- Acid-duty equipment confirmed. We verify your receiving tank, pump and hose materials are rated for fuming acid before the first load moves.
- Export machinery handled in-house. UN 1831 classification, acid-tanker compliance, labelling, freight booking and customs paperwork are ours to manage.
Packed the way your plant receives it
Pack format drives your landed cost and your handling effort. Tell us how the material will be charged at your end and we will quote the format that suits your operation.
MS drums (acid-resistant lined)
Lined mild-steel drums for Class 8 liquids — the standard format for smaller volumes and trial quantities.
ISO acid tank containers
Dedicated acid-duty ISO tanks for bulk ocean and rail movement, avoiding repeated decanting and its exposure risk.
Road tanker (regional)
Acid-duty insulated road tankers for domestic and cross-border deliveries where tanker infrastructure exists at both ends.
Trial / sample quantities
Small drums dispatched so your process team can qualify strength and performance before committing to tanker volumes.
Incoterms to suit you
Quoted on the Incoterm your purchasing team works to, with DG documentation filed before the booking is made.
Campaign despatch
We hold contracted tonnage and release it against your sulfonation plant's production calendar instead of landing it all at once.
Water reactivity is the controlling hazard
Oleum 65% is severely corrosive to skin, eyes and the respiratory tract, and reacts violently and exothermically with water, releasing heat and dense, corrosive SO₃/H2SO4 mist. The summary below is orientation only — the safety data sheet supplied with your consignment is the authoritative document.
Classified hazards
H314Causes severe skin burns and eye damage.H335May cause respiratory irritation.EUH014Reacts violently with water.H290May be corrosive to metals.
Hazard statements reflect classifications commonly published for fuming sulfuric acid (CAS 8014-95-7). The mist evolved on contact with moist air is itself a respiratory hazard, independent of liquid contact. Always read the SDS issued with your specific batch.
Spill & emergency orientation
Plan your response before the pallet arrives. Sections 4, 5 and 6 of the SDS are the authoritative instructions and should be posted at the point of use.
- Never add water to the acid. Acid is added to water, in small portions, with cooling — reversing this order causes violent spattering and boiling.
- Contain with dry inert absorbent. Dry sand, vermiculite or dry lime — never a combustible organic absorbent — and neutralise cautiously before disposal.
- Expect visible fuming at the spill edge. Evacuate and ventilate the area; SO₃ mist is heavier than air and will hug low ground and drains.
- Treat burns immediately. Flush affected skin or eyes with copious water for at least 15 minutes and seek medical attention — do not apply neutralising agents directly to skin.
- Reduction and dilution are both exothermic. Any dilution step in your process needs calorimetry and properly sized cooling; this is not a step to improvise on the day.
Storage
- Dedicated acid-duty tankage only. Mild steel, Hastelloy or acid-brick lined vessels rated for fuming sulfuric acid — standard stainless and most plastics are unsuitable.
- Keep bone dry. Moisture ingress generates SO₃ mist and internal pressure — vent through a drying trap, never leave a tank open to atmosphere.
- Segregate from water, organics and bases. Contact with any of these is exothermic and can be violent at oleum's SO₃ content.
- Bunded, access-controlled area. A severely corrosive liquid needs secondary containment and restricted access as standard practice.
- No fixed shelf life under correct storage. Degradation shows as darkening color or iron pickup rather than a hard expiry — re-assay before use after extended storage.
Handling & PPE
- Closed transfer only. Pump or gravity-feed through sealed, acid-rated lines; never open-pour or sample from an open bung without local exhaust.
- Full acid-resistant PPE. Face shield over chemical goggles, acid suit, and gauntlet-length nitrile or butyl gloves — splash risk is high during connection and disconnection.
- Emergency deluge shower and eyewash on site. Within seconds' reach of every transfer point, tested and logged routinely.
- Never mix grades or acids in one vessel. Blending different SO₃ strengths or acids without engineering control can run away thermally.
- Respiratory protection for mist. Acid-gas cartridge respirators or supplied air during any operation that can release SO₃ mist, per your exposure assessment.
Transport
Fuming sulfuric acid moves as regulated cargo under UN 1831, Class 8, Packing Group I. We classify each consignment, confirm tanker or drum compatibility, apply UN-approved labelling and file the dangerous-goods declaration before the booking is made — ask us for the current DG paperwork when you plan the shipment.
What travels with every consignment
A chemical shipment is only as good as the file that travels with it. Verifying what the source plant sends is precisely the work you are buying from a supplier.
Certificate of Analysis
Batch-specific free-SO₃, H2SO4 equivalent, iron and color — checked against your purchase specification before release.
GHS Safety Data Sheet
Full 16-section SDS in GHS format covering hazards, exposure controls, handling, storage, spill response and disposal, issued in the language your destination requires.
Dangerous Goods Declaration
UN 1831, hazard class, packing group and IMDG or RID/ADR declaration prepared and filed before the tanker or container is booked.
Certificate of Origin
Chamber-attested where required, plus preferential-origin forms where a trade agreement gives your import duty relief.
Third-party inspection
SGS, Intertek or Bureau Veritas sampling and inspection arranged on request before loading, giving you independent verification of what ships.
Retained & pre-shipment samples
Pre-shipment samples carry the same COA as the commercial lot, so what your laboratory qualifies is exactly what arrives.
Extra SO₃, dissolved and ready to react
Oleum is simply 100% sulfuric acid with more sulfur trioxide dissolved into it than the H2SO4 molecule alone can bind. The routes below are the general industrial pattern, not a process disclosure.
Burn sulfur to SO₂
Molten sulfur or pyrite roasting generates sulfur dioxide, the feedstock for the whole sulfuric-acid chain.
Catalytically oxidise to SO₃
Vanadium-pentoxide catalyst converts SO₂ to SO₃ at the contact-process plant.
Absorb SO₃ into acid, not water
Routing excess SO₃ into 98% acid rather than water gives oleum instead of more dilute acid — the step that defines the grade.
Ship as fuming acid
The finished oleum is drummed or tankered at the target free-SO₃ percentage, 65% in this case.
Why free-SO₃ content carries through the whole process
In a sulfonation or nitration reactor, oleum's strength is not a quality nicety — it is the stoichiometry:
- Free SO₃ is the limiting reagent. Under-strength oleum simply stops the reaction short of full conversion, leaving unreacted feedstock in your batch.
- Iron contamination colors the product. Trace iron picked up from mild-steel handling darkens sulfonated dyes and detergent intermediates.
- Moisture dilutes the active species. Any water ingress converts free SO₃ back to H2SO4, quietly lowering effective strength before it ever reaches your reactor.
- Color is the quick practical read. A darkening batch usually signals iron or organic contamination before the COA assay confirms it.
That is why we quote against your written free-SO₃ target rather than a generic "oleum" label, and why the batch COA is shared for approval before dispatch rather than sent with the invoice.
| Material | Downstream / use |
|---|---|
| Oleum 65% CAS 8014-95-7 — this product | LAB/LAS sulfonation, mixed-acid nitration |
| Oleum 20% / 23% Lower free-SO₃ grades | Milder sulfonation, acid-plant blending |
| 98% Sulfuric acid CAS 7664-93-9 | General acid-plant feedstock |
| Chlorosulfonic acid CAS 7790-94-5 | Sulfonyl chloride & saccharin chemistry |
We supply across this intermediate family — see the full intermediate range. Send the CAS number and we will confirm the correct material before quoting.
What actually moves the price of this product
Knowing what drives the quote helps you time a purchase and read whether an offer is realistic.
SO₃ absorption capacity sets the cost
Making oleum means absorbing extra SO₃ into an acid base rather than water — the higher the target free-SO₃, the more energy-intensive the absorption step.
- 65% sits near the practical ceiling
- Higher grades need tighter process control
- We flag when a lower grade would do
Elemental sulfur price
Sulfur is the ultimate feedstock for the whole chain, and its price tracks refinery and fertiliser-sector demand for sulfuric acid.
- Sulfur market moves feed through in weeks
- We note feedstock-driven swings in the quote
- Contracted call-off smooths exposure
Tanker and drum logistics
Fuming acid needs dedicated acid-duty tankage at both ends — that infrastructure requirement, not distance alone, shapes freight cost.
- Compare on landed cost, not ex-works
- Confirm receiving tank compatibility early
- We quote FOB, CIF, CFR or DDP as you prefer
Class 8 handling and insurance
Corrosive-cargo surcharges, specialist handling and higher cargo insurance all sit inside the delivered price of a fuming acid.
- DG surcharges vary by route and carrier
- We compare several qualified carriers
- Ask us about annual freight contracts
Co-product plant economics
A contact-process plant makes both standard acid and oleum from the same SO3 stream — demand for one affects the other's availability.
- Oleum and 98% acid prices move together
- Ask us what the base-acid market is doing
- Dual-source contracts smooth supply risk
Source availability
Sulfuric-acid plants run continuous campaigns; a turnaround or feedstock disruption removes capacity at short notice.
- We hold a second qualified source
- Qualify the alternate before you need it
- Ask us about dual-source contracts
| If your end use is… | Specify |
|---|---|
| Detergent alkylate sulfonation | 65% free SO3, low iron, tight color spec |
| Dye / brightener sulfonation | 65% free SO3, confirmed mono-sulfonation performance |
| Mixed-acid nitration | Free-SO3 content matched to your nitric-acid ratio |
| Agrochemical / pharma route | Full impurity profile, end-use declaration |
| Trial / qualification | Small acid-duty drum, full COA |
Not sure which column you are in? Describe what you make from it and our technical desk will recommend the grade — including telling you when a cheaper specification would do the job just as well.
Support that goes beyond shipping the drum
What our technical desk will do
- Confirm free-SO₃ content before anything else. On a fuming acid this is the number that decides reaction yield, and we settle it in the first reply.
- Be straight about the hazard profile. Severely corrosive, water-reactive, fuming — stated at enquiry stage so your EHS and logistics teams can plan loading arms and PPE.
- Review your receiving infrastructure. We ask about tank, pump and hose materials before the first load moves, not after a compatibility failure.
- Review your specification before it goes into a contract. So you are not locked into a strength no plant can consistently hit.
Regulatory & compliance notes
- Corrosive-cargo handling is jurisdiction-specific. Several regimes impose storage-tank certification and operator training for fuming acids. Confirm what applies at your site before the first delivery.
- Import controls vary by destination. We check destination rules before quoting, not after you have raised the PO.
- Chemical inventory listings differ between regions. We will supply the identity data you need for that filing.
- Effluent and neutralisation rules matter. Check your discharge consent against the material before introducing it to site.
None of the above is legal advice — your own regulatory affairs team owns the final compliance position for your import and your workplace. What we commit to is accurate product identity data, an honest statement of the hazard classification and complete documentation to work from.
From enquiry to delivered pallet
Send the specification
Product name or CAS 8014-95-7, your target free-SO₃%, quantity, pack or tanker preference and destination port.
Receive a firm quote
Pricing, lead time, packing and Incoterm confirmed in writing within 24 hours — our sourcing desk is staffed around the clock.
Qualify and approve
Sample dispatched if you are qualifying a new source. Batch COA shared for your approval before the material is released.
Ship and track
UN 1831 classification filed, DG freight booked, export documents issued, and the consignment tracked through transit and clearance to your plant.
What buyers ask us about Oleum 65%
What does "65%" mean on oleum?
How is this different from 98% sulfuric acid?
Why does iron content matter on this product?
What is the minimum order quantity?
How long does delivery take?
How should we store it?
Is this a dangerous good? What paperwork comes with it?
Do you supply to my country?
Do you manufacture this yourself?
Request pricing on Oleum 65%
Send your required free-SO₃ percentage, quantity, pack or tanker format and destination port. Our sourcing desk is available 24 hours a day, 7 days a week, and comes back with pricing, lead time and packing options — whether that is a single trial drum or a contracted programme for the year.