Substance profile
Hydrogen
Hydrogen is a colorless gas and is odorless.
01 · Identification
What Hydrogen is
Hydrogen is a colorless gas and is odorless. Its molecular formula is H2 and its molecular weight is 2.016 g/mol. It boils at -259 °C, melts at -253 °C.
Under the GHS it carries the signal word Danger. It is classed as flammable agents - 4th degree.
02 · GHS classification
Hazards and label elements
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
| Code | Hazard statement |
|---|---|
| H220 | Extremely flammable gas. |
03 · Physical and chemical properties
Hydrogen properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | -259.16 °C (-434.5 °F) | HSDB | |
| -252.78 °C (-423 °F) | at 760 mmHg | CAMEO | |
| Melting point | -252.76 °C (-423 °F) | HSDB | |
| -258.89 °C (-434 °F) | CAMEO | ||
| Density | 0.0001 g/cm³ | HSDB | |
| 0.071 g/cm³ | at -253 °C | CAMEO | |
| Solubility | Very low solubility in most liquids | HSDB | |
| In water, 1.62 mg/L at 21 °C | at 21 °C | HSDB | |
| Solubility in water, mg/l at 21 °C: 1.62 (very poor) | at 21 °C | ICSC | |
| Vapor pressure | 1240000 mmHg | at 25 °C | HSDB |
| Flash point | Flammable gas | ICSC | |
| Autoignition temperature | 500 °C (932 °F) | HSDB | |
| 573.89 °C (1065 °F) | CAMEO | ||
| Lower explosive limit (LEL) | 4 % by volume | HSDB | |
| 4.1 % by volume | HSDB | ||
| Upper explosive limit (UEL) | 75 % by volume | % by vol | HSDB |
| 74.2 % by volume | HSDB | ||
| 75 % by volume | CAMEO | ||
| Vapor density | 0.07 (air = 1) | ICSC | |
| Critical temperature and pressure | -239.9 °C (-399.8 °F) | HSDB | |
| Corrosivity | Noncorrosive | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
04 · Handling and storage
Storing and handling Hydrogen
Storage conditions
Store in a cool, dry, well-ventilated location. Outside or detached storage is preferred. Isolate from oxygen, halogens, other oxidizing materials. /Hydrogen, refrigerated liquid/
Source: Hazardous Substances Data Bank (HSDB)
Incompatible materials
Release of hydrogen @ 47.5 bar into a vented 17.5-l chromium-plated sphere caused explosive ignition. /Hydrogen/
Source: Hazardous Substances Data Bank (HSDB)
Planning storage for a mix of chemicals? Check Hydrogen in the storage compatibility matrix →