Oleum 23%
The Oleum 23% supplied by Chelora Chemicals — fuming sulfuric acid carrying 23% free dissolved sulphur trioxide, a stronger sulfonating and dehydrating agent than sulfuric acid alone — exported from Indonesia in specialised moisture-proof packaging with full batch documentation on every shipment.
What Oleum 23% is, and why buyers source it
A working overview of fuming sulfuric acid's chemistry, why its free SO3 content gives it reactivity sulfuric acid alone cannot match, and how this 23% grade is positioned against its stronger counterpart.
Oleum, commonly called fuming sulfuric acid, is sulfuric acid holding additional, uncombined sulphur trioxide in solution beyond what pure H2SO4 itself represents — conceptually, more than 100% strength sulfuric acid. That free SO3 content is both the source of the material's name (it fumes visibly in moist air as the volatile SO3 reacts with atmospheric moisture) and the entire reason buyers choose oleum over ordinary concentrated sulfuric acid: the free SO3 is a considerably more aggressive sulfonating and dehydrating agent than the bound sulfuric acid molecule alone, enabling reactions that plain sulfuric acid cannot drive to completion, or can only drive slowly and incompletely.
At room temperature it is a colourless to brown, dense, heavily fuming liquid. The 23% grade — meaning 23% free SO3 by weight dissolved in the balance of sulfuric acid — is the lower-strength of the two oleum grades Chelora Chemicals carries, chosen for sulfonation and other reactions where a reactive excess of SO3 is wanted but the very highest reactivity of the 65% grade is either unnecessary or would be difficult to control.
Where it fits in the value chain
Oleum 23% is used across sulfonation chemistry in dye, surfactant (including the linear alkylbenzene sulfonation route we cover on our LAB and chlorosulfonic acid pages) and specialty-chemical manufacture, wherever a moderate excess of reactive SO3 beyond ordinary sulfuric acid's own strength drives a sulfonation reaction to acceptable yield and rate. It is also used as a dehydrating agent in certain organic syntheses and nitration chemistry, where the free SO3 helps absorb water generated during the reaction and keeps the overall acid medium at the strength the reaction needs throughout.
Grades we supply
Chelora Chemicals offers Oleum at this 23% free-SO3 strength as our standard technical grade for general sulfonation and dehydration chemistry, alongside our stronger 65% grade for applications needing the higher reactivity. Each grade is supplied with a batch-wise certificate of analysis covering free SO3 content.
How Oleum 23% is produced
An overview of the production route for orientation purposes. Our manufacturing partners' own process parameters and in-process controls are proprietary and are not disclosed beyond what is needed to interpret the certificate of analysis.
Oleum 23% is produced by absorbing additional sulphur trioxide gas, generated in the same catalytic SO2-to-SO3 conversion process used for conventional sulfuric acid manufacture, into concentrated (98%+) sulfuric acid at a controlled ratio, rather than diluting that SO3 fully into new sulfuric acid molecules. Controlling the amount of SO3 absorbed relative to the acid base is what sets the final free-SO3 percentage, with 23% being one of two standard strengths produced for the broader chemical market, alongside the higher 65% grade.
Because the absorption of SO3 into sulfuric acid is itself exothermic and the product fumes on any exposure to atmospheric moisture, the finishing and packaging steps are run under tightly controlled, moisture-excluded conditions, with the product transferred directly into the lined, moisture-proof packaging it ships in rather than exposed to open-air handling at any stage.
Industries and processes that use it
Oleum 23% is consumed across dye, surfactant and specialty-chemical sulfonation, plus select dehydration and nitration chemistry. The fields below account for most of the demand we see through our export desk.
Dye & Pigment Sulfonation
Introduces sulfonic acid groups onto aromatic dye and pigment intermediates, improving water solubility for the finished colourant.
Surfactant Sulfonation
Used in the sulfonation step of certain surfactant manufacturing routes, converting a hydrophobic organic substrate into a water-soluble anionic surfactant.
Specialty Chemical & Pharmaceutical Intermediate Sulfonation
Introduces sulfonic acid or related functional groups into specialty chemical and pharmaceutical fine-chemical intermediates.
Dehydrating Agent in Organic Synthesis
Used as a dehydrating agent in select organic syntheses and nitration reactions, where the free SO3 helps absorb reaction water and maintain acid strength.
How the reagent is typically used forward
The free SO3's heightened reactivity governs almost all of Oleum 23%'s further use. The categories below account for most of the ways it is applied in downstream synthesis.
Aromatic Sulfonation
The free SO3 reacts directly with an aromatic ring under electrophilic substitution conditions, introducing a sulfonic acid group more readily and completely than ordinary sulfuric acid alone would achieve.
Dehydration in Nitration Mixtures
Added to nitration acid mixtures to absorb the water generated as the nitration reaction proceeds, keeping the overall acid strength high enough to sustain the reaction to completion.
Esterification/Dehydration Catalysis
Used as a strong dehydrating catalyst in select esterification and condensation reactions where ordinary sulfuric acid's water affinity is insufficient.
Further SO3 Supply (In-Situ)
In some processes, oleum serves simply as a convenient, storable, liquid-phase source of reactive SO3 that is released as needed during the reaction rather than handling gaseous SO3 directly.
Oleum 23% against the stronger oleum grade and other sulfuric derivatives we supply
Buyers sourcing Oleum 23% sometimes need the stronger 65% grade for a more demanding sulfonation step, or a different sulfuric derivative entirely. A quick reference to what else is on our regular supply list.
| Product | CAS Number | Category | Notes |
|---|---|---|---|
| Oleum 23% | 8014-95-7 | Fuming sulfuric acid | The product on this page — a moderate-strength sulfonating and dehydrating agent. |
| Oleum 65% | 8014-95-7 | Fuming sulfuric acid, higher strength | A related, considerably more reactive oleum grade for more demanding sulfonation chemistry — see its product page. |
| Sulfuric Acid | 7664-93-9 | Mineral acid | The parent acid both oleum grades are made from — see its product page. |
| Chlorosulfonic Acid | 7790-94-5 | Mixed acid chloride/sulfonic acid | A related, even more specialised derivative used for direct sulfonyl chloride introduction — see its product page. |
Exact free-SO3 content and purity specifications are confirmed per batch on the certificate of analysis — treat the notes above as a sourcing guide, not a specification sheet, for products other than Oleum 23%.
Safety classification at a glance
Based on GHS classification as commonly listed for this substance. This is a summary for orientation only — always work from the current safety data sheet supplied with your specific batch.
Causes severe skin burns and eye damage.
Toxic if inhaled.
Reacts violently with water.
Fumes heavily on exposure to atmospheric moisture, releasing a corrosive sulfuric acid/SO3 mist.
Chemical-resistant gloves, full-face respiratory protection and acid-resistant clothing are required for routine handling.
Must be handled under strictly moisture-controlled conditions.
Danger
This product causes severe skin burns and eye damage on contact, is toxic if inhaled, and reacts violently with water, releasing substantial heat and a corrosive acid mist — a reaction that begins simply from exposure to atmospheric humidity if a container is not kept properly sealed, which is also the source of the visible fuming the material is named for. Handling requires chemical-resistant gloves, full-face respiratory protection, acid-resistant clothing and work in a fume hood or otherwise well-ventilated, moisture-controlled area. Full first-aid, storage, spill and PPE guidance is in the MSDS issued with every shipment, and must be read in full before this material is handled.
Keeping it on spec between delivery and use
General storage guidance for this grade. Site-specific storage rules, segregation requirements and re-test intervals should follow your own EHS procedures and the MSDS issued with your batch.
Store in specialist lined, moisture-excluding containers in a cool, dry area, strictly away from water, organic materials and strong bases. Any container showing signs of pressure build-up or heavy fuming at the seal should be treated with particular caution and isolated rather than opened under uncontrolled conditions. Re-check free SO3 content on a batch held past its retest date before use, since atmospheric moisture ingress gradually consumes the free SO3 even in well-sealed storage.
How it ships from Indonesia
Standard packing and export terms for this product. Confirm exact figures against your order — they vary slightly by destination and quantity.
What travels with every batch
Specification is agreed before the purchase order, not discovered on arrival. Every shipment of Oleum 23% leaves with a documented, checkable paper trail.
Certificate of Analysis
Batch-wise assay, colour and key physical constants, issued against the agreed specification so your QC team can check it, not just file it.
Safety Data Sheet
GHS-format SDS in English covering hazard classification, handling, storage, first-aid and spill response for the exact grade shipped.
Technical Data Sheet
Reference physical and chemical properties, recommended storage and typical applications, for internal circulation to your process or R&D teams.
Certificate of Origin
Confirms Indonesian origin for customs clearance and any preferential-duty claim at your destination port.
Dangerous Goods Declaration
UN packing group, classification and shipper's declaration prepared ahead of loading so documentation never holds up customs.
Third-Party Inspection
Independent pre-shipment inspection and re-sampling can be arranged on request, at your cost, for buyers who require it as a matter of policy.
Frequently asked questions
What buyers most often ask our sales desk about this grade.
01What is Oleum 23% used for?+
02What is the difference between Oleum 23% and Oleum 65%?+
03How is Oleum 23% produced?+
04What grades does Chelora Chemicals supply?+
05Is Oleum 23% hazardous?+
06Why does Oleum fume visibly while ordinary sulfuric acid does not?+
07What packing options are available?+
08How long does delivery take?+
09Can I get a sample before placing a bulk order?+
10Do you supply the stronger oleum grade and other sulfuric derivatives as well?+
Need Oleum 23% on spec, on time?
Send us your required free SO3 content, quantity, packing preference and destination port. Our desk quotes most enquiries within one working day.