Oleum 65%
The Oleum 65% supplied by Chelora Chemicals — high-strength fuming sulfuric acid carrying 65% free dissolved sulphur trioxide, for the most demanding sulfonation and dehydration chemistry — exported from Indonesia in specialised moisture-proof packaging with full batch documentation on every shipment.
What Oleum 65% is, and why buyers source it
A working overview of high-strength fuming sulfuric acid's chemistry, why its very high free SO3 content is reserved for the most demanding sulfonation needs, and how this grade compares with the lower-strength 23% oleum.
Oleum 65% is fuming sulfuric acid carrying 65% free, uncombined sulphur trioxide by weight — nearly three times the free-SO3 concentration of the 23% grade in our catalogue, and correspondingly a markedly more aggressive sulfonating and dehydrating agent. At this concentration, the free SO3 approaches being the dominant component of the liquid mixture by reactive significance even though sulfuric acid is still the greater share by mass, and the material fumes very heavily and immediately on any exposure to atmospheric moisture.
At room temperature it is a colourless to brown, dense, heavily fuming liquid, handled with even greater care than the 23% grade given both its higher reactivity and its somewhat higher viscosity and density. Buyers specify this grade specifically where a reaction's substrate is comparatively unreactive, where very high sulfonation conversion is required, or where process economics favour using a smaller volume of a stronger reagent over a larger volume of the 23% grade.
Where it fits in the value chain
Oleum 65% is used across the more demanding end of sulfonation chemistry: dye and pigment intermediates that are comparatively resistant to sulfonation under milder conditions, high-conversion surfactant sulfonation where the 23% grade would leave an unacceptable level of unreacted substrate, and specialty pharmaceutical and agrochemical fine-chemical sulfonation where reaction completeness is critical to downstream purity. It is also used as a particularly strong dehydrating agent in nitration and condensation chemistry where the reaction generates comparatively large amounts of water that must be absorbed to keep the reaction progressing.
Grades we supply
Chelora Chemicals offers Oleum at this 65% free-SO3 high-strength grade for the most demanding sulfonation and dehydration chemistry, alongside our standard 23% grade for more moderate reactions. Each grade is supplied with a batch-wise certificate of analysis covering free SO3 content.
How Oleum 65% 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 65% is produced by the same fundamental process as the 23% grade — absorbing additional sulphur trioxide gas into concentrated sulfuric acid — but carried further, dissolving proportionally more SO3 into the acid base to reach the higher target free-SO3 percentage. Reaching and holding this higher concentration requires closer control of absorption conditions, since the mixture's vapour pressure and fuming tendency increase substantially as free SO3 content rises, making containment and moisture exclusion progressively more demanding at each higher strength.
As with the 23% grade, the absorption step is exothermic and the finished product fumes immediately on any exposure to atmospheric moisture, so finishing and packaging are carried out under tightly controlled, moisture-excluded conditions, with the product transferred directly into the specialist lined packaging it ships in.
Industries and processes that use it
Oleum 65% is consumed across the most demanding sulfonation reactions in dye, surfactant and specialty-chemical manufacture, plus high-intensity dehydration chemistry. The fields below account for most of the demand we see through our export desk.
High-Conversion Dye & Pigment Sulfonation
Sulfonates comparatively resistant aromatic dye and pigment intermediates that do not reach acceptable conversion under the milder 23% oleum grade.
High-Conversion Surfactant Sulfonation
Used where very high conversion of the surfactant substrate is required, minimising unreacted starting material carried into the finished surfactant product.
Specialty Pharmaceutical & Agrochemical Sulfonation
Introduces sulfonic acid groups into comparatively unreactive specialty pharmaceutical and agrochemical fine-chemical intermediates where reaction completeness is critical to downstream purity.
High-Intensity Dehydration & Nitration Chemistry
Used as a particularly strong dehydrating agent in nitration and condensation reactions generating comparatively large amounts of water.
How the reagent is typically used forward
The very high free SO3 content governs almost all of Oleum 65%'s further use. The categories below account for most of the ways it is applied in downstream synthesis.
High-Conversion Aromatic Sulfonation
The high concentration of free SO3 drives sulfonation of comparatively unreactive aromatic substrates to a high conversion level that the 23% grade cannot reliably achieve on its own.
Intensive Dehydration in Reaction Mixtures
Added to nitration, condensation or esterification mixtures generating substantial reaction water, absorbing that water aggressively to keep the overall acid medium at the strength needed to sustain the reaction.
Reduced-Volume Process Economics
Used where a smaller volume of this higher-strength reagent achieves the same or better conversion than a larger volume of 23% oleum, an economic consideration for high-throughput sulfonation processes.
Further SO3 Supply (In-Situ)
Serves as a concentrated, storable, liquid-phase source of reactive SO3 for processes needing to release a larger quantity of SO3 per unit volume of reagent added.
Oleum 65% against the lower-strength oleum grade and other sulfuric derivatives we supply
Buyers sourcing Oleum 65% for a demanding sulfonation step may also want to compare it against the lower-strength 23% grade, or a different sulfuric derivative entirely. A quick reference to what else is on our regular supply list.
| Product | CAS Number | Category | Notes |
|---|---|---|---|
| Oleum 65% | 8014-95-7 | Fuming sulfuric acid, high strength | The product on this page — a high-strength sulfonating and dehydrating agent for the most demanding reactions. |
| Oleum 23% | 8014-95-7 | Fuming sulfuric acid | A related, moderate-strength oleum grade for more routine 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 65%.
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 very heavily and immediately on exposure to atmospheric moisture, releasing a dense, corrosive acid 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, more critical than for lower-strength oleum given the higher fuming tendency.
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 dense, corrosive acid mist even more readily than the 23% oleum grade given its considerably higher free SO3 content. 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, with particular care given this grade's heightened reactivity relative to lower-strength oleum. 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, with particular attention to container integrity given this grade's heightened fuming tendency relative to lower-strength oleum. 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.
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 65% 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 65% used for?+
02What is the difference between Oleum 65% and Oleum 23%?+
03How is Oleum 65% produced?+
04What grades does Chelora Chemicals supply?+
05Is Oleum 65% hazardous?+
06When should I choose Oleum 65% instead of Oleum 23%?+
07What packing options are available?+
08How long does delivery take?+
09Can I get a sample before placing a bulk order?+
10Do you supply the lower-strength oleum grade and other sulfuric derivatives as well?+
Need Oleum 65% 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.