Dimethyl Sulfate DMS · CAS 77-78-1
Chelora Chemicals is a supplier of Dimethyl Sulfate (DMS), the industrial methylating agent used across dye, pharmaceutical, fragrance and agrochemical synthesis. Because DMS is an acutely toxic, corrosive and suspected human carcinogen, every consignment leaves with a batch-specific COA, the current SDS and full dangerous-goods documentation, and we expect every buyer to have closed-handling controls in place before shipment.
Also known as: DMS · Sulfuric Acid Dimethyl Ester · Methyl Sulfate · Dimethyl Sulphate
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Price, lead time and a sample COA for Dimethyl Sulfate, usually within one working day. We ship worldwide to qualified, EHS-vetted buyers.
Request a Quote Email the DeskDocumentation
- Batch-specific COA (GC purity, acidity, colour)
- Safety Data Sheet (SDS)
- Dangerous-goods transport documents (UN 1595, Class 6.1 PG I)
- Third-party inspection on request
- Certificate of origin
What is Dimethyl Sulfate?
Dimethyl Sulfate is the dimethyl ester of sulfuric acid, formula C₂H₆O₄S, with the structure (CH₃O)₂SO₂. At room temperature it is a colourless, oily liquid with a faint onion-like odour, boiling around 188 °C and only slightly soluble in water, which it decomposes on contact with evolution of heat.
Its value as an industrial reagent comes from being one of the most reliable and cost-effective methylating agents available: it transfers a methyl group to phenols, amines, carboxylic acids and other nucleophiles cleanly and in high yield, which is why it has been produced commercially since at least the early 20th century despite its severe hazard profile.
Commercially, it is made by reacting methanol with sulfuric acid or sulfur trioxide under controlled conditions, and supplied as a high-purity liquid for industrial methylation chemistry.
Dimethyl Sulfate is one of the most hazardous chemicals in routine industrial use: it is acutely toxic by all routes of exposure, corrosive to skin, eyes and metals, and is reasonably anticipated to be a human carcinogen and a strong DNA alkylating agent. It is classified UN 1595, Class 6.1, Packing Group I — the most severe toxic-goods packing group — and must only be handled in closed systems by trained personnel with the correct engineering controls.
Why Dimethyl Sulfate specifically
- An efficient, general-purpose methylating agent. It methylates phenols, amines, thiols and carboxylic acids with high conversion and relatively mild conditions.
- Cost-effective at scale. Compared with other methylating agents such as methyl iodide, DMS is significantly cheaper per mole of methyl group transferred, which is why it remains in use for large-scale industrial synthesis despite the hazard.
- Established industrial process. Decades of plant experience exist for handling it safely in closed systems, which is why it is still specified by process chemists who need its reactivity and economics.
- A route to quaternary ammonium compounds. Its reactivity toward amines also makes it useful for preparing quaternary ammonium salts for surfactant and flocculant chemistry.
How Dimethyl Sulfate is Manufactured
Dimethyl Sulfate is made on purpose from methanol and a sulfur trioxide source, in a dedicated, closed, corrosion-engineered plant.
- Esterification. Methanol is reacted with sulfuric acid or sulfur trioxide under carefully controlled temperature in closed, corrosion-resistant equipment.
- Separation. The crude ester is separated from spent acid and unreacted methanol.
- Purification. The product is purified by vacuum distillation to remove acid and dimethyl ether impurities, since both affect stability and purity.
- Quality release. Purity, acidity and colour are confirmed against specification before the batch is released.
- Closed packing. The finished liquid is transferred and packed under closed-system conditions directly into corrosion-resistant, dangerous-goods-rated containers.
Typical Commercial Specification
Figures below are representative of commercial-grade Dimethyl Sulfate. Tell us your downstream route and the grade you need, and we will advise on the specification to order against.
| Parameter | Typical Value |
|---|---|
| Appearance | Colourless oily liquid, faint onion-like odour |
| Dimethyl sulfate content | 99% min by GC |
| Free sulfuric acid | To grade, low ppm |
| Dimethyl ether / methanol impurities | To grade, low ppm |
| Colour (Hazen / APHA) | To grade, typically 20 max |
| Density (20 °C) | About 1.33 g/mL |
| Boiling point | About 188 °C |
| Flash point | About 83 °C (closed cup) |
Physical & Chemical Properties
| Property | Value |
|---|---|
| Chemical formula | C₂H₆O₄S, (CH₃O)₂SO₂ |
| Molecular weight | 126.13 g/mol |
| Appearance | Colourless oily liquid |
| Melting point | About −32 °C |
| Boiling point | About 188 °C (decomposes on prolonged heating) |
| Density | About 1.33 g/mL at 25 °C |
| Solubility in water | Slightly soluble; hydrolyses with evolution of heat to methanol and sulfuric acid |
| Flash point | About 83 °C |
| Incompatibilities | Strong oxidisers, strong ammonia solutions, water (hydrolysis), most common metals (corrosive) |
Behaviour in the process
DMS's reactivity is exactly what makes it both useful and dangerous:
- Potent electrophilic methylation. Each methyl group is an effective electrophile, transferring readily to phenols, amines, carboxylates and thiols — the same property that makes it a strong DNA alkylating agent in a biological system.
- Hydrolysis. Contact with water decomposes DMS to methanol and sulfuric acid, releasing heat; this reaction is also how spilled or waste DMS is typically destroyed under controlled conditions.
- Corrosivity. It attacks most common metals and is corrosive to tissue, which drives the choice of construction materials for storage and transfer equipment.
- Combustibility. A combustible liquid (NFPA rating 2) that releases toxic vapours, including sulfur oxides, if it burns.
Dimethyl Sulfate and Alternative Methylating Agents
DMS is one of several industrial methylating agents, and the choice between them is a genuine trade-off between cost, efficiency and hazard.
| Methylating agent | Hazard profile | When it is the right choice |
|---|---|---|
| Dimethyl sulfate | Acutely toxic, corrosive, suspected carcinogen | Large-scale, cost-sensitive methylation in a plant with established closed-handling infrastructure |
| Dimethyl carbonate | Low toxicity, not classified as a carcinogen | Where a safer, greener methylating agent can achieve the same conversion, often at higher temperature |
| Methyl iodide | Acutely toxic, suspected carcinogen | Smaller-scale, higher-value synthesis where DMS's lower cost advantage matters less |
| Trimethyl phosphate | Toxic but generally regarded as somewhat less hazardous than DMS | Selected methylation routes where a phosphate ester by-product is acceptable |
| Methanol / acid catalyst | Low acute hazard | Esterifications and etherifications that do not require DMS's stronger electrophilicity |
Stated plainly: DMS is rarely the only chemically possible choice, but it is often the most economical one for a plant already equipped to handle it safely. Where that infrastructure does not exist, switching to a lower-hazard alternative is usually the right call rather than building new containment around DMS, and we are glad to talk through that trade-off with you.
Industries We Supply Dimethyl Sulfate To
The same methylating liquid feeds a dye-intermediate plant, a pharmaceutical synthesis unit and a specialty-chemical producer. What changes is the downstream methylation chemistry and, critically, the handling infrastructure each must have in place.
Where Dimethyl Sulfate is Used
DMS is bought entirely as a reagent consumed in methylation reactions, not as a component of any finished product. These are the synthesis steps our customers use it for.
In dye, pharma and agrochemical intermediate manufacture
DMS methylates the nucleophile of choice — a phenol oxygen, an amine nitrogen, a carboxylate — cleanly and in high yield under conditions that are well-characterised and widely documented in process literature. This reliability, combined with its low cost per methyl group transferred, is why many established plants continue to specify it despite the availability of lower-hazard alternatives.
Handling the trade-off
Because every use of DMS carries acute toxicity, corrosivity and carcinogenicity risk, process chemists increasingly evaluate whether dimethyl carbonate or another lower-hazard reagent can achieve the same conversion before committing a new process to DMS. For an existing, validated DMS-based process in a plant with the right containment, continuing with DMS is often still the most practical choice — which is the situation most of our customers for this product are in.
Need a specific purity, packing format, or a hazard review before you order?
Tell us your downstream route, your closed-handling infrastructure, the packing format you can receive and the annual quantity. We will come back with a price, a lead time, a sample COA and the full dangerous-goods documentation — and flag anything in your setup worth reviewing before the first shipment.
Quality Control & Testing
Every lot is released against a batch-specific Certificate of Analysis, with free-acid content reported alongside purity because it governs both stability and corrosion behaviour.
- Dimethyl sulfate content — by gas chromatography, the primary grade measure.
- Free sulfuric acid — reported because acid impurity accelerates hydrolysis and corrosion.
- Dimethyl ether / methanol impurities — checked as incomplete-reaction by-products.
- Colour (Hazen / APHA) — an indicator of thermal history and trace contamination.
- Density and boiling range — checked as fast purity and identity indicators.
Common Process Problems & Likely Causes
When DMS causes trouble, it is usually free-acid content, moisture ingress or corrosion in handling equipment. This table is the shortcut our technical desk works through before anyone opens a complaint file.
| Symptom | Likely cause | What to check |
|---|---|---|
| Reduced methylation yield | Free acid or hydrolysis during storage | Free-acid content and moisture exposure history |
| Corrosion in transfer lines | Free acid or moisture ingress attacking metal | Free-acid figure on the COA and line material compatibility |
| Unexpected exotherm on addition | Water contamination triggering hydrolysis | Moisture control on both the DMS and the receiving vessel |
| Colour carry-through to downstream product | Colour or trace contamination in the DMS lot | Colour figure on the COA |
| Gas evolution or pressure rise in storage | Slow hydrolysis from trace moisture | Tank integrity, moisture exclusion and venting design |
Packaging, Storage & Shipping
- Standard packing. Corrosion-resistant lined drums or ISO tank containers rated for Class 6.1 PG I toxic liquids; glass-lined or specialty-alloy construction is common.
- Moisture exclusion. Keep sealed and dry at all times; water hydrolyses DMS with evolution of heat and forms corrosive sulfuric acid in situ.
- Material compatibility. Avoid most common metals, which DMS corrodes; use equipment rated specifically for this reagent.
- Temperature control. Store at room temperature, away from heat sources and direct sun; keep above its melting point (about −32 °C) to remain liquid for handling.
- Segregation. Keep strictly apart from strong oxidisers and strong ammonia solutions, and from any water source.
- Transfer. Closed-system transfer only, with local exhaust ventilation and leak detection; never handled in open containers.
- Transport classification. UN 1595, Class 6.1 (toxic), Packing Group I — the most stringent toxic-goods category. ADR, IMDG, IATA and DOT requirements apply strictly to tank design, labelling and routing.
Hazards & Safe Handling
Dimethyl Sulfate is one of the most hazardous reagents in routine industrial use. It is fatal if inhaled, toxic if swallowed, causes severe skin burns and eye damage, is suspected of causing genetic defects, and is reasonably anticipated to be a human carcinogen. Closed-system handling by trained personnel is not optional.
- Acute inhalation toxicity. Vapour inhalation can be fatal and primarily damages the lungs, with injury also reported to the liver, kidneys, heart and central nervous system. Use is restricted to closed systems with engineered ventilation and continuous monitoring.
- Carcinogenicity and genotoxicity. DMS is reasonably anticipated to be a human carcinogen (US NTP) and is classified by the EPA as a probable human carcinogen (Group B2); it is consistently genotoxic as a strong DNA alkylating agent in laboratory assays.
- Severe corrosive injury. Causes severe skin burns, eye damage and, on inhalation, severe inflammation and necrosis of the eyes, mouth and respiratory tract.
- No safe informal handling. There is no level of open-container or ad hoc handling that is acceptable for this product; it must be dispensed and transferred only through closed, leak-tested systems.
- PPE and engineering controls. Fully encapsulating chemical-resistant suits, supplied-air respiratory protection, closed transfer systems, continuous gas detection and emergency decontamination facilities are the baseline, not an enhancement.
- Emergency response. Sites handling DMS must have a dedicated emergency response plan, trained first responders and immediate access to decontamination and medical support, since acute exposure can be life-threatening.
- Waste and spill handling. Controlled hydrolysis (reaction with excess water or dilute alkali under controlled conditions) is the standard destruction method; follow your site's validated procedure rather than improvising.
Regulatory & Compliance Notes
Dimethyl Sulfate is one of the most heavily regulated industrial reagents in routine commercial use. Because obligations differ sharply by territory and use, the notes below are orientation rather than legal advice — your regulatory and EHS teams must confirm your own position before you handle this product.
- GHS classification. Signal word "Danger"; hazard statements covering acute oral toxicity (H301), skin corrosion/severe burns (H314), skin sensitisation (H317), fatal if inhaled (H330), suspected genetic defects (H341) and suspected carcinogenicity (H350). The SDS carries the complete hazard statement set.
- Carcinogen listings. Listed by the US NTP as reasonably anticipated to be a human carcinogen, and by IARC and EPA under their respective probable/possible human carcinogen categories.
- Occupational exposure regulation. Many jurisdictions apply very low occupational exposure limits and require closed-system handling, specific training, medical surveillance and a documented control-of-substances-hazardous-to-health (or equivalent) assessment.
- Dangerous goods transport. UN 1595, Class 6.1, Packing Group I — the strictest toxic-goods packing group. ADR, IMDG, IATA and DOT requirements apply in full to tank design, labelling, routing and emergency information.
- REACH and chemical inventories. Registered under EU REACH with carcinogen/mutagen risk-management measures, and listed on major chemical inventories including TSCA.
- Site authorisation. Many jurisdictions require specific permits, process-safety reviews or major-hazard notifications for sites storing or using DMS above threshold quantities. Confirm your obligations before your first order.
We Supply Dimethyl Sulfate Worldwide
Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Dimethyl Sulfate from India and from partner sources to qualified customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, Class 6.1 PG I transport paperwork and specialised freight so the material arrives ready to use.
- Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
- Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other ports arranged where Class 6.1 PG I rules and routing allow.
- Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the full Class 6.1 PG I transport declaration issued as a complete set.
- Flexible volumes. From drum quantities up to full ISO tank loads on contract supply, subject to buyer qualification.
- Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.
Buying Dimethyl Sulfate from Chelora
We are an independent sourcing and supply partner. For DMS that means settling three things at enquiry: confirmation of your closed-handling infrastructure and training, the purity and packing format your process needs, and the Class 6.1 PG I documentation that moves it legally across your shipping lane.
- Buyer qualification first. We confirm closed-handling infrastructure, trained personnel and emergency response capability before confirming a first order.
- Documentation on every lot. Batch-specific COA with purity, free acid and colour, plus SDS and full Class 6.1 PG I transport paperwork.
- Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the material.
- Quantities. Drum quantities through to full ISO tank loads on contract supply.
- Inspection. Independent third-party inspection available at loading when the contract requires it.
- Lower-hazard alternatives. If your process has flexibility, we can also discuss dimethyl carbonate or other lower-hazard methylating agents as a long-term alternative.
How ordering works
- Send the enquiry. Quantity, destination, the Incoterm you buy on, and a summary of your handling infrastructure and training programme.
- We review your setup. Our technical desk confirms your closed-handling, PPE, ventilation and emergency-response capability before quoting.
- We quote. Price, lead time, packing format and a sample COA, normally within a few working days once qualification is complete.
- Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
- Allocation and QC. Material allocated and released against a batch-specific COA, with an independent inspection where the contract calls for it.
- Ship and document. Filled, labelled and loaded with the full export and Class 6.1 PG I transport document set, and tracked through to arrival.
Dimethyl Sulfate — Common Questions
The questions our technical desk is asked most often about Dimethyl Sulfate. If yours isn't here, call or email and you will reach someone who knows both the chemistry and the safety requirements.
What is the CAS number of Dimethyl Sulfate?
The CAS number for Dimethyl Sulfate is 77-78-1, and its EC number is 201-058-1. Its molecular formula is C₂H₆O₄S with a molecular weight of 126.13 g/mol.
What is Dimethyl Sulfate used for?
Mainly as an industrial methylating agent, converting phenols, amines and carboxylic acids to their methyl derivatives in the manufacture of dyes, pharmaceutical intermediates, fragrances, agrochemicals and quaternary ammonium surfactants.
Is Dimethyl Sulfate dangerous?
Yes, severely. It is fatal if inhaled, toxic if swallowed, causes severe skin burns and eye damage, is suspected of causing genetic defects, and is reasonably anticipated to be a human carcinogen. It must only be handled in closed systems by trained personnel with the correct PPE and engineering controls.
Do you supply Dimethyl Sulfate worldwide?
Yes, to qualified buyers. Chelora Chemicals supplies and exports Dimethyl Sulfate across Asia Pacific, Europe, the Middle East, Africa and the Americas, as well as throughout India, but we confirm a buyer's closed-handling infrastructure and training before shipping a first order. Every consignment carries the COA, SDS and full Class 6.1 PG I transport documentation.
How is Dimethyl Sulfate manufactured?
By reacting methanol with sulfuric acid or sulfur trioxide under controlled conditions in closed, corrosion-resistant equipment, followed by separation and vacuum distillation to the target purity.
What are the UN number and transport class?
UN 1595, Class 6.1 (toxic), Packing Group I — the most stringent toxic-goods packing group. ADR, IMDG, IATA and DOT rules apply strictly to tank design, labelling and routing.
How should Dimethyl Sulfate be stored?
In sealed, corrosion-resistant containers rated for Class 6.1 PG I liquids, kept strictly dry (it hydrolyses with evolution of heat on water contact), away from strong oxidisers and strong ammonia solutions, and handled only through closed transfer systems.
Is there a safer alternative to Dimethyl Sulfate?
Dimethyl carbonate is a lower-toxicity methylating agent that can replace DMS in some processes, though it often needs higher temperatures to achieve the same conversion. If your process has flexibility, we are glad to discuss whether it or another lower-hazard reagent could work for you.
Do I need special approval to buy Dimethyl Sulfate?
We confirm every new customer's closed-handling infrastructure, trained personnel and emergency response capability before shipping a first order, given the severity of this product's hazard profile. Many jurisdictions also require their own permits or process-safety notifications for sites storing or using it above threshold quantities.
What purity grades do you offer?
Standard commercial grade is 99% minimum by GC, with free-acid content and colour reported on the COA.
What packing sizes and order quantities are available?
Corrosion-resistant lined drums through to full ISO tank loads, all packed to Class 6.1 PG I dangerous-goods requirements, subject to buyer qualification.
Ready to source Dimethyl Sulfate?
Send us your quantity requirement and a summary of your closed-handling infrastructure. You will get a price, a realistic lead time and a sample COA from someone who understands both the chemistry and the safety standard this product demands — delivered anywhere in the world.