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Short answer
The density of dichloromethane (DCM, methylene chloride, CAS 75-09-2) is about 1.33 g/mL at 20 °C (1.3255 g/mL in the Merck Index entry reproduced by PubChem). That is roughly one-third denser than water, so DCM sinks below an aqueous layer. It boils at about 40 °C and has a vapour pressure of 47.4 kPa at 20 °C, which is why it evaporates fast at the bench.
Definition and scope
Dichloromethane (DCM, also called methylene chloride; CAS 75-09-2) is a volatile chlorinated organic liquid widely used in laboratories as a solvent, notably for extraction and for dissolving organic compounds before evaporation. This page covers its physical properties as listed by PubChem and International Chemical Safety Card 0058, and what they imply for bench work.
This page is a bench-oriented property sheet for DCM as a laboratory solvent: what each number is, where the published values differ, and what the numbers mean for extraction, evaporation and handling. It is general reference information, not a safety data sheet; follow your institution’s chemical hygiene plan and the supplier’s SDS for any work.
Dichloromethane density: 1.3255 g/mL at 20 °C
PubChem lists several density values for DCM from different primary compilations. They are not in conflict; they differ in temperature, rounding and the reference they come from.
| Reported value | Conditions | Source cited by PubChem |
|---|---|---|
| 1.322 | 68 °F (20 °C) | USCG CHRIS, 1999 |
| 1.3255 g/mL | 20 °C / 4 °C | Merck Index, 2013 |
| 1.3266 | 20 °C | Protective Action Criteria (US DOE) |
| 1.3 (relative density, water = 1) | 20 °C | ILO-WHO International Chemical Safety Card 0058 |
| 1.33 | not stated | OSHA chemical database; NIOSH Pocket Guide |
For calculations, 1.33 g/mL is the usual working figure and 1.3255 g/mL is the figure to quote when you need four significant figures at 20 °C. Density falls as temperature rises, so a value taken at 20 °C should not be reused unchanged for solvent that is warm from a bath or cold from a freezer. Use the certificate or SDS for your specific lot when precision matters.
Is dichloromethane denser than water?
Yes. At about 1.33 g/mL against roughly 1.00 g/mL for water, DCM is denser, and the USCG CHRIS entry states it plainly: “Denser than water; will sink.” In a separatory funnel the DCM layer is therefore normally the lower layer when the other phase is water. This is the opposite of ethyl acetate or diethyl ether, which float on water (compare the ethyl acetate density sheet). The order can change when a heavily loaded aqueous phase, such as a concentrated salt solution, becomes denser than the organic phase, so check which layer is which by adding a few drops of water rather than assuming.
Why DCM does not mix with water
DCM is only partly soluble in water: ICSC 0058 gives 1.3 g/100 mL at 20 °C, and PubChem lists values of about 13 g/L (13,000 to 13,200 mg/L) at 25 °C. That is enough to form a separate phase at any ordinary extraction volume, though a small amount of DCM does dissolve in the water layer. DCM is, by contrast, miscible with ethanol and diethyl ether and soluble in carbon tetrachloride (PubChem), which is why it is used to pull organic compounds out of aqueous mixtures.
Boiling point, vapor pressure and freezing point
| Property | Value | Source |
|---|---|---|
| Boiling point | 40 °C (39.75 °C at 760 mmHg listed separately) | ICSC 0058; PubChem |
| Melting / freezing point | −97 °C (other compilations list −95 to −97.2 °C) | ICSC 0058; PubChem |
| Vapour pressure | 47.4 kPa at 20 °C; 435 mmHg at 25 °C | ICSC 0058; PubChem |
| Viscosity | 0.437 mPa·s at 20 °C | PubChem |
| Refractive index | 1.4244 at 20 °C (D line) | PubChem |
| Explosive limits in air | 13 to 22 vol% | ICSC 0058 |
Where it matters for labs: what the numbers mean at the bench
- Rotary evaporation. A boiling point near 40 °C and a vapour pressure close to half an atmosphere mean DCM leaves a flask readily at modest vacuum and a mild bath. That also means it is easy to lose volatile products with it. See what a rotary evaporator is for how bath temperature and vacuum interact.
- Containers and transfers. High vapour pressure means vapour builds up in closed bottles and in a warm room, and the vapour is not something to breathe: transfers belong in a ventilated enclosure such as a fume hood.
- Low viscosity. At 0.437 mPa·s DCM is less viscous than water at the same temperature, so it runs through filters, columns and syringe needles quickly and drips from pipette tips.
- Refractive index. A value of 1.4244 is a useful identity check when a refractometer is available for an unlabelled solvent.
- Freezing point. At −97 °C it will not freeze in a standard freezer or dry-ice bath, so it is usable at low temperature where water-based media are not.
Is dichloromethane toxic to humans?
ICSC 0058 lists hazards including: harmful if swallowed; skin and eye irritation; drowsiness and dizziness; central nervous system effects after repeated inhalation; possible damage to blood, liver, heart and lungs; and that it may cause cancer. The card also records reactions with strong oxidants, strong bases and aluminium and magnesium powders. The same card gives an ACGIH TLV of 50 ppm (8-hour time-weighted average, classification A3, skin notation) and an EU occupational exposure limit of 100 ppm (353 mg/m³) as a time-weighted average with 200 ppm as a short-term limit. In the United States, OSHA’s methylene chloride standard (29 CFR 1910.1052) sets its own permissible exposure limit and procedures; our guide to the OSHA methylene chloride standard covers how it applies in laboratories, and how to read a safety data sheet explains the SDS sections you should consult first.
Why is DCM getting banned?
The US Environmental Protection Agency regulates methylene chloride under the Toxic Substances Control Act (TSCA). According to EPA’s risk management page for methylene chloride (read 2026-11-07), a 2019 rule banned its consumer use in paint and coating removal, and a final TSCA risk management rule announced in April 2024 prohibits consumer uses and most industrial and commercial uses, with most uses phased out over two years. Laboratory use is not banned outright: it continues under a Workplace Chemical Protection Program (WCPP) of exposure controls. EPA published a final rule in November 2025 extending certain WCPP compliance dates for non-federal laboratories by 18 months. Because TSCA rules for this chemical have been the subject of litigation and further rulemaking, check EPA’s page and the current Federal Register text for the status and dates that apply to your facility before changing or continuing a procedure.
Common misunderstandings
- “Bottom layer means the product is in the water.” With DCM and water the organic layer is usually the lower one. Label both layers and keep both until the product is confirmed.
- “DCM and water do not mix at all.” About 1.3 g per 100 mL dissolves at 20 °C; it separates, but it is not perfectly insoluble.
- “One density number fits every temperature.” The published values (1.322 to 1.3266) reflect different temperatures, sources and rounding.
- “It is not flammable, so it is safe in the open.” ICSC lists explosive limits in air of 13 to 22 vol%, and its health hazards come from inhalation and contact, not from fire.
Frequently asked questions
What is the density of dichloromethane in g/mL?
About 1.33 g/mL at 20 °C; the Merck Index value is 1.3255 g/mL at 20 °C/4 °C.
Is dichloromethane denser than water?
Yes. It sinks in water and forms the lower layer in a water and DCM mixture.
What is the boiling point of dichloromethane?
About 40 °C (39.75 °C at 760 mmHg in one listed value).
What is the vapor pressure of dichloromethane?
47.4 kPa at 20 °C (ICSC 0058) and 435 mmHg at 25 °C (PubChem).
What is the freezing point of dichloromethane?
About −97 °C; other compilations give −95 to −97.2 °C.
Why does DCM not mix with water?
Its water solubility is limited to about 1.3 g/100 mL at 20 °C, so it separates into its own, denser phase.
Is dichloromethane toxic to humans?
ICSC 0058 lists acute and chronic hazards and states it may cause cancer. See the toxicity section above and the SDS for your product.
Why is DCM getting banned?
EPA’s 2024 TSCA rule prohibits consumer and most industrial and commercial uses; laboratory use continues under workplace controls. Check EPA for current status.
Sources
- PubChem, Dichloromethane, CID 6344 (density, boiling point, melting point, vapour pressure, solubility, viscosity and refractive index headings; National Library of Medicine), https://pubchem.ncbi.nlm.nih.gov/compound/Dichloromethane, read 2026-11-07.
- International Chemical Safety Card 0058, Dichloromethane (ILO-WHO), https://inchem.org/documents/icsc/icsc/eics0058.htm, read 2026-11-07.
- US EPA, Risk Management for Methylene Chloride, https://www.epa.gov/assessing-and-managing-chemicals-under-tsca/risk-management-methylene-chloride, read 2026-11-07.
- Federal Register, 2025-19881 (13 November 2025), https://www.govinfo.gov/content/pkg/FR-2025-11-13/html/2025-19881.htm.
