Dimethyl Sulfoxide (DMSO) CAS 67-68-5

What Is Dimethyl Sulfoxide (DMSO)?

Dimethyl sulfoxide, commonly abbreviated as DMSO, is a highly polar aprotic solvent with the chemical formula C₂H₆OS. It is supplied as a clear, colorless and hygroscopic liquid and is completely miscible with water.

DMSO combines high solvency, low volatility and compatibility with many organic and inorganic substances. It is used in pharmaceutical and agrochemical synthesis, polymer processing, electronics cleaning formulations, industrial cleaning, extraction and laboratory analysis.

Its CAS number is 67-68-5 and its molecular weight is 78.13 g/mol.

Industrial-grade DMSO must not automatically be described as pharmaceutical, sterile, injectable, cell-culture or cryopreservation grade. These applications require separately qualified products and regulatory documentation.

DMSO Quick Facts

Values above are reference properties. The applicable AOZUN specification, quotation and Certificate of Analysis should determine the contracted product quality.

Why Is DMSO Called a Polar Aprotic Solvent?

DMSO is strongly polar but does not contain an acidic hydrogen bonded to oxygen or nitrogen. It is therefore classified as a polar aprotic solvent.

Its sulfoxide group produces a strong molecular dipole. This allows DMSO to interact with ions and polar molecules while its methyl groups also provide compatibility with many organic compounds.

These properties give DMSO an unusually broad solubility range and make it useful as a reaction medium, processing solvent and cleaning-formulation component.

How Does DMSO Work as a Polar Aprotic Solvent?

The strongly polar sulfur-oxygen group in DMSO can stabilize and solvate many ions and polar compounds, while the methyl groups help it interact with less-polar organic structures. This combination allows DMSO to dissolve or disperse a wide variety of salts, polymers, resins, dyes and organic intermediates.

Why Water Content Matters

DMSO is hygroscopic and readily absorbs moisture from the atmosphere. Water can change:

• Solvent strength

• Reaction rate

• Chemical selectivity

• Polymer dope viscosity

• Crystallization behavior

• Extraction performance

• Analytical background

• Electronic-cleaning performance

• Active content per kilogram

Containers should remain tightly closed, and low-moisture applications should use appropriate transfer and storage controls.

Typical AOZUN DMSO Specifications

These values describe a typical commercial specification. Confirm the current specification, analytical methods and batch COA before ordering.

What Do the Main DMSO Specifications Mean?

DMSO Content

DMSO content is normally measured by gas chromatography. Purity alone does not describe water, trace metals, UV-absorbing impurities or residue after evaporation.

Moisture

Moisture is commonly measured by Karl Fischer titration. A maximum of 0.10% is typical for many 99.9% commercial and reagent grades.

Applications requiring anhydrous conditions may need a lower water specification, moisture-protected packaging and controlled transfer.

Acid Value

Acid value indicates the amount of acidic material present in the product. Low acidity is important for reaction control, equipment compatibility and product stability.

The unit and analytical method must be stated. A value expressed in milligrams of KOH per gram cannot be directly compared with a titratable-acidity result reported in milliliters of standard sodium hydroxide.

Crystallization Point

Crystallization point is an identity and purity indicator. Pure DMSO crystallizes at approximately 18.5°C.

A low result may indicate water or other impurities. However, a product can remain liquid below its normal freezing point because of supercooling.

Transmittance and UV Absorbance

Transmittance at 400 nm provides a general indication of clarity and light-absorbing impurities.

HPLC or spectrophotometric applications usually require absorbance limits at several wavelengths, such as 268, 275, 300, 350 and 400 nm. A single 400 nm transmittance specification does not automatically qualify a product as HPLC or UV-spectrophotometric grade.

Refractive Index

Refractive index helps confirm product identity and consistency. It is affected by temperature, moisture and dissolved impurities, so the measurement temperature must be stated.

Residue After Evaporation

Nonvolatile residue is important in electronics, analytical, polymer and high-purity cleaning applications. It indicates the amount of material remaining after DMSO has evaporated.

Color

High-purity DMSO is normally water-white. Applications sensitive to color may require an APHA or Pt-Co color limit.

Trace Metals

Semiconductor and electronic applications may require very low levels of sodium, potassium, calcium, iron, copper and other metallic contaminants.

A standard industrial COA does not normally provide sufficient trace-metal control for advanced electronics manufacturing.

Available DMSO Grades

Industrial Grade DMSO

Industrial grade is used in general chemical processing, polymer applications, extraction and industrial cleaning formulations.

Typical priorities include:

• Purity

• Water

• Acidity

• Crystallization point

• Color

• Batch consistency

Synthesis Grade DMSO

Synthesis grade is intended for chemical-reaction and intermediate-manufacturing applications. Customers may require tighter controls over water, acidity and organic impurities.

Anhydrous DMSO

Anhydrous DMSO is used when moisture can affect reaction yield, selectivity or stability.

The package must be protected from humidity, and the customer’s transfer system should prevent moisture pickup after opening.

ACS Reagent Grade DMSO

ACS reagent grade must meet the applicable reagent specification for assay, water, color, acidity and residue after evaporation.

Industrial purity of 99.9% does not by itself establish ACS compliance.

HPLC and Spectrophotometric Grade DMSO

These grades require controlled UV absorbance in addition to high purity, low water and low nonvolatile residue.

They are selected for analytical methods where solvent background can affect detection.

Electronic Grade DMSO

Electronic-grade DMSO is produced for semiconductor or electronic cleaning formulations requiring extremely low metal ions, particles and nonvolatile residue.

The term “electronic grade” should be supported by numerical contaminant limits and suitable manufacturing controls.

Pharmaceutical or Excipient Grade DMSO

Pharmaceutical DMSO may need to comply with USP, Ph. Eur. or other applicable pharmacopeial requirements. It may also require GMP manufacturing, impurity profiling, change control and regulatory support.

A product used as an excipient, processing aid or API must be specifically qualified for that use.

Sterile and Cell-Culture Grade DMSO

DMSO used in cell culture or cryopreservation may require:

• Sterility testing

• Bacterial-endotoxin limits

• Cell-culture performance testing

• Qualified aseptic processing

• Appropriate container-closure validation

• GMP or application-specific quality systems

Industrial DMSO must not be substituted into these applications.

DMSO Applications

Pharmaceutical and Fine-Chemical Synthesis

DMSO is widely used as a reaction solvent in pharmaceutical, agrochemical and fine-chemical synthesis.

As a polar aprotic medium, it can support:

• Nucleophilic substitution

• Oxidation chemistry

• Alkylation

• Cyclization

• Polymerization

• Salt dissolution

• Intermediate purification

• Crystallization and antisolvent processes

Reaction safety, solvent removal and impurity formation must be evaluated for each process.

Agrochemical Formulations and Synthesis

DMSO may be used as a formulation solvent or synthesis medium for selected agricultural active ingredients and intermediates.

Final formulations require testing for:

• Active-ingredient solubility

• Storage stability

• Packaging compatibility

• Crop safety

• Worker exposure

• Regulatory compliance

Industrial DMSO should not be applied directly to crops unless it is part of an approved and validated formulation.

Polymer Processing

DMSO can dissolve or process selected polymers and is used in applications involving:

• Polyacrylonitrile spinning

• Membrane casting

• Acrylic-resin processing

• Polysulfone systems

• Polymer residue removal

• Polymerization reaction media

Water content, polymer molecular weight, solids concentration, temperature and coagulation conditions can significantly affect the process.

Carbon-Fiber Precursor Production

DMSO may be used as a solvent in selected polyacrylonitrile-based precursor-fiber processes.

The required grade depends on:

• Polymer purity

• Dope viscosity

• Moisture

• Metal ions

• Filtration

• Fiber-spinning conditions

• Solvent recovery

• Coagulation behavior

Not every carbon-fiber production route uses DMSO.

Electronics and Semiconductor Cleaning

DMSO is used as a component in selected photoresist-removal, polymer-residue and electronic-cleaning formulations.

These applications may require:

• Extremely low metallic contamination

• Low particle counts

• Low nonvolatile residue

• Controlled water

• High optical purity

• Consistent organic-impurity profile

DMSO alone is not automatically compatible with every wafer material, photoresist, metal layer or dielectric. Complete formulations must be qualified on representative substrates.

Industrial Cleaning

DMSO’s broad solvency makes it useful in formulations designed to remove:

• Polymer residue

• Resin

• Paint

• Coating deposits

• Adhesive residue

• Process contamination

Surface compatibility, ventilation, fire controls, wastewater management and operator exposure must be evaluated before use.

Paint and Coating Removal

DMSO may serve as a solvent in formulated paint and coating removers. Its relatively low volatility can increase surface contact time.

Performance depends on the coating chemistry, film thickness, substrate, temperature and other formulation ingredients.

It should not be promoted as a universally safe household paint remover.

Dye and Pigment Processing

DMSO can be used to dissolve selected dyes, pigments and formulation ingredients. However, describing its chemical function simply as “dyes and pigments” is inaccurate.

Its primary chemical function is as a polar aprotic solvent.

Extraction and Separation

DMSO can be used in selected liquid extraction, aromatic-separation and purification processes because of its polarity and solvency.

Process design should address:

• Partition behavior

• Water content

• Product recovery

• Solvent recycling

• Thermal stability

• Corrosion

• Residual-solvent limits

Laboratory and Analytical Use

Qualified reagent, HPLC or spectrophotometric DMSO is used for sample preparation, dissolution, analytical standards and reaction studies.

The grade should match the analytical method. Standard industrial DMSO may produce unacceptable UV background or nonvolatile residue.

DMSO vs DMF and NMP

DMSO may be evaluated as an alternative to DMF or NMP, but it is not an automatic drop-in replacement.

Before substitution, compare:

• Solubility

• Reaction kinetics

• Product selectivity

• Boiling point

• Energy required for recovery

• Water sensitivity

• Viscosity

• Crystallization risk

• Equipment compatibility

• Residual-solvent limits

• Waste-treatment requirements

Why Does DMSO Freeze in a Cool Warehouse?

DMSO has a relatively high crystallization point of approximately 18.5°C. It can therefore crystallize during winter shipping or storage even though it is normally described as a liquid.

Crystallization does not automatically mean the product is defective or degraded.

To restore the liquid:

1. Keep the container closed.

2. Warm it gradually using an approved temperature-controlled system.

3. Avoid open flames and uncontrolled direct heating.

4. Allow sufficient time for complete melting.

5. Mix the container or tank to restore uniformity.

6. Check appearance before use.

7. Follow the supplier’s heating and handling instructions.

Partially melted DMSO may not be compositionally uniform because water and impurities can concentrate in the remaining liquid phase.

How to Prevent DMSO Crystallization Problems

For cold-weather logistics and production:

• Review the expected transport temperature.

• Use insulated storage where appropriate.

• Maintain suitable warehouse temperature.

• Provide approved drum or tank warming capability.

• Allow time for thawing before production.

• Do not take a representative sample from partially frozen material.

• Rehomogenize the product after complete melting.

• Protect the product from moisture during warming.

DMSO Material Compatibility

DMSO is a strong solvent and may soften, swell or extract components from certain plastics, elastomers, coatings and seal materials.

Before selecting equipment, test or confirm compatibility for:

• Storage tanks

• Drum and IBC materials

• Pump seals

• Gaskets

• Hoses

• Valves

• Transfer lines

• Protective gloves

• Coated surfaces

Stainless steel and appropriately qualified materials are commonly used, but suitability depends on temperature, exposure time and product grade.

How to Evaluate a DMSO Supplier

A qualified supplier should be able to confirm:

1. Product identity and CAS number

2. Intended grade

3. Purity and test method

4. Moisture limit

5. Acid value or titratable acidity

6. Crystallization point

7. Refractive index

8. Optical transmittance or UV absorbance

9. Nonvolatile residue

10. Trace-metal limits, when applicable

11. Manufacturing and quality system

12. Batch traceability

13. Packaging compatibility

14. COA, TDS and SDS availability

15. Change-notification procedure

16. Pharmaceutical or electronic documentation when claimed

Do not qualify a pharmaceutical or electronic grade based only on a 99.9% purity result.

Recommended Incoming Quality Checks

Depending on the application, incoming DMSO may be checked for:

• Container and seal condition

• Label and batch number

• Appearance

• Purity by GC

• Water by Karl Fischer titration

• Acid value

• Crystallization point

• Refractive index

• Color

• Optical transmittance

• UV absorbance

• Residue after evaporation

• Trace metals

• COA compliance

Sampling equipment must be clean, dry and compatible with DMSO.

DMSO Packaging Options

DMSO may be supplied in:

• Compatible drums

• IBCs

• ISO tank containers

• Bulk tank shipments

• Small laboratory containers

• Moisture-controlled high-purity packaging

Packaging availability depends on grade, order volume and destination.

High-purity and electronic grades may require specially cleaned containers, controlled filling and additional contamination protection.

DMSO Storage

Store DMSO in a cool, dry and well-ventilated area in tightly closed, compatible containers.

Recommended controls include:

• Protect the product from atmospheric moisture.

• Keep it away from incompatible chemicals.

• Control ignition sources.

• Maintain an appropriate storage temperature.

• Prevent container contamination.

• Use dry, dedicated transfer equipment.

• Avoid prolonged uncontrolled heating.

• Clearly identify partially used containers.

• Follow first-in, first-out inventory management.

Storage below approximately 18.5°C may cause crystallization.

DMSO Safety Information

DMSO has a relatively low vapor pressure and a comparatively favorable toxicological profile for an industrial solvent, but it still requires controlled handling.

Important hazards include:

• Eye irritation

• Possible skin irritation

• Combustible-liquid behavior

• Skin penetration

• Transport of dissolved contaminants through the skin

• Hazardous reactions with incompatible chemicals

• Thermal-decomposition risk under unsuitable process conditions

Contaminated DMSO can carry other dissolved substances through the skin. Avoid direct skin contact and keep working surfaces and gloves free of hazardous chemicals.

Glove selection should be based on manufacturer permeation data for DMSO and the complete chemical mixture. A generic glove-material recommendation may not provide adequate protection.

DMSO Process-Safety Considerations

DMSO is stable under normal recommended storage conditions, but process conditions can create additional hazards.

Before heating or scaling a DMSO reaction, evaluate:

• Maximum operating temperature

• Heat of reaction

• Contaminants

• Strong oxidizers

• Strong acids

• Acid chlorides

• Halogenating reagents

• Dehydrating reagents

• Pressure generation

• Emergency cooling

• Solvent decomposition

• Waste-stream compatibility

Reaction calorimetry and a formal process-hazard assessment may be required for unfamiliar or large-scale chemistry.

DMSO Transport Information

DMSO is commonly listed as not regulated as dangerous goods under major transport systems, although some workplace classifications describe it as a combustible liquid.

Final classification must be confirmed using:

• The shipment-specific SDS

• Product flash point

• Container size

• Transport mode

• Destination-country regulations

• Any additives in the product

A DMSO formulation may have a different classification from pure DMSO.

What Documents Should a DMSO Supplier Provide?

Depending on grade and application, buyers may request:

• Certificate of Analysis

• Safety Data Sheet

• Technical Data Sheet

• Product specification

• Manufacturing statement

• Country of Origin

• Commercial invoice

• Packing list

• Regulatory-inventory statement

• Residual-solvent statement

• Trace-metal report

• UV absorbance data

• GMP statement

• USP or Ph. Eur. compliance statement

• Sterility and endotoxin results

• Change-control documentation

Only request pharmaceutical or sterile documentation when the purchased grade is specifically produced and qualified for that application.

Why Source DMSO from AOZUN?

AOZUN supports international industrial buyers sourcing DMSO for chemical synthesis, polymer processing, industrial cleaning and other qualified applications.

Commercial support may include:

• Grade and specification review

• Batch-specific COA

• TDS and SDS documentation

• Moisture and crystallization-point confirmation

• Packaging discussions

• Sample evaluation

• Cold-weather shipment planning

• Export-document coordination

• Third-party inspection

• Technical communication during qualification

Product grade, specification, packaging, regulatory status and suitability must be confirmed in the final quotation and sales contract.

Information to Include in Your DMSO RFQ

For a more accurate quotation, provide:

• Product name and CAS number

• Required grade

• Minimum purity

• Maximum water content

• Acid-value limit

• Optical-transmittance requirements

• UV-absorbance requirements

• Trace-metal limits

• Intended application

• Order quantity

• Packaging requirement

• Destination

• Required documentation

• Sample requirement

• Delivery schedule

If you are replacing another DMSO grade, attach its current specification or representative COA.

Frequently Asked Questions

What is DMSO?

DMSO is dimethyl sulfoxide, a highly polar aprotic solvent used in chemical synthesis, polymer processing, electronics, industrial cleaning and laboratory analysis.

What is the CAS number of DMSO?

The CAS number is 67-68-5.

What is the molecular formula of DMSO?

Its molecular formula is C₂H₆OS, and its molecular weight is 78.13 g/mol.

Is DMSO soluble in water?

Yes. DMSO is completely miscible with water.

Why does DMSO crystallize?

Pure DMSO crystallizes at approximately 18.5°C. It may therefore freeze in a cool warehouse or during winter transportation.

Is frozen DMSO defective?

Not necessarily. It can normally be restored by controlled warming, complete melting and mixing. The supplier’s instructions should be followed.

Is DMSO flammable?

DMSO has a flash point around 87°C and may be classified as a combustible liquid. It should be kept away from ignition sources and uncontrolled heat.

Can DMSO pass through skin?

DMSO can penetrate skin and may increase the absorption of dissolved contaminants. Direct skin contact must be avoided.

Can industrial DMSO be used for pharmaceutical production?

Industrial DMSO may be used as a synthesis solvent where appropriately qualified, but it must not be represented as USP, Ph. Eur., injectable or excipient grade without the required specification and quality documentation.

Is 99.9% DMSO automatically HPLC grade?

No. HPLC grade also requires suitable UV absorbance, residue, water and impurity controls.

Is 99.9% DMSO electronic grade?

No. Electronic grade usually requires extremely low metal ions, particles and nonvolatile residue in addition to high purity.

Can industrial DMSO be used for cryopreservation?

No such assumption should be made. Cryopreservation requires an appropriately qualified grade with relevant sterility, endotoxin and biological-quality controls.

Can DMSO replace DMF or NMP?

It may be evaluated as an alternative, but solvent substitution requires testing of solubility, reaction performance, recovery, crystallization, equipment compatibility and product quality.

What specifications should buyers compare?

Compare purity, water, acidity, crystallization point, refractive index, color, transmittance, UV absorbance, nonvolatile residue, organic impurities and trace metals.

How should DMSO be stored?

Keep it tightly closed, dry and protected from incompatible materials. Storage temperature should account for its approximately 18.5°C crystallization point.

Can AOZUN provide a DMSO sample and COA?

Sample and batch-document availability can be discussed during quotation. Include the required grade, application, specification and destination in the inquiry.

Request a DMSO Quote

Contact AOZUN for dimethyl sulfoxide pricing, specifications, packaging and export information.

Send us your required grade, purity, moisture limit, application, quantity, packaging, destination and delivery schedule. Our team will review the requirement and confirm the appropriate commercial specification.