Sulfur hexafluoride is a useful gas for medicine, manufacturing, and science projects. This non-toxic invisible gas is heavier than air and essentially non-reactive. Here are some facts about sulfur hexafluoride and a couple of fun demonstrations to try.
Sulfur Hexafluoride Formula and Other Facts
The chemical formula of sulfur hexafluoride is SF6. The molecule consists of one sulfur atom covalently bonded to six oxygen atoms.
- Chemical formula is SF6
- Inorganic compound
- Invisible as a gas, colorless as a liquid or solid
- Octahedral geometry
- Poorly soluble in water; soluble in nonpolar organic solvents
- Gas density is 6.13 g/L at sea level
Sulfur Hexafluoride Demonstrations
Most science demonstration involving helium also work with sulfur hexafluoride. While helium is about six times lighter than air, sulfur hexafluoride is around six times heavier or more dense.
Float a Boat
Float light objects on the invisible vapor.
- Fill a bowl, aquarium, or box with sulfur hexafluoride. While the gas mixes some with air, it mostly sinks.
- Float light objects on this invisible gas, making them appear suspended in the air. Good objects to try include paper airplanes, paper boats, or foil boats.
- If you scoop out a cupful of the gas and pour it over your plane or boat, it will sink.
Get a Deep Voice
Both helium and sulfur hexafluoride change the timbre of your voice (they don’t actually raise or lower the pitch). Helium makes your voice sound higher, while sulfur hexafluoride makes it sound deeper. The density of the gas changes the speed of sound. In normal air, this is about 343 m/s. With sulfur hexafluoride, it’s about 134 m/s at room temperature.
- Fill a balloon with sulfur hexafluoride. Alternatively, dispense it into a deep bowl or a box.
- Inhale the gas.
- Speak or sing.
Use care and avoid hypoxia. Don’t breath either helium or sulfur hexafluoride for a prolonged period of time or keep repeating the demonstration.
Where to Get Sulfur Hexafluoride
Sulfur hexafluoride is a common gas that finds use in eye surgery, ultrasound imaging, insulating the space between window panes in insulated windows, and as an inert gas for manufacturing processes. So, you can purchase it from a specialty gas supplier (search online for one near you) or from a business that uses it. You don’t need a lot of it for science demonstrations, so if you can borrow a tank, it’s likely cheaper and more practical than purchasing a whole tank.
Sulfur hexafluoride is non-toxic, non-flammable, and reasonably non-reactive. Science demonstrations using this chemical generally are considered safe. However, there are risks associated with its use that you should keep in mind.
- Since it’s supplied as a liquefied, compressed gas, dispensing it poses a frostbite risk. As with any compressed gas, as it gas expands, it cools. Wear gloves when appropriate.
- When you inhale sulfur hexafluoride, it displaces oxygen. So, as with helium, it poses an asphyxiation risk if you inhale took much. If you feel faint or light-headed, get fresh air immediately. Unlike helium (which rises), sulfur hexafluoride sinks. Its concentration is greatest at the lowest point of its container.
- Sulfur hexafluoride is a mild anesthetic, slightly less potent than nitrous oxide.
- The CDC’s NIOSH Pocket Guide to Hazardous Chemicals mentions sulfur hexafluoride may contain a toxic impurity in the form of sulfur pentafluoride.
- While it’s a great insulator, an electric discharge or arc causes a chemical reaction, forming highly toxic disulfur decafluoride (S2F10).
- Fluorides tend to be reactive, but sulfur hexafluoride is not. However, it does react exothermically with lithium.
- Dervos, Constantine T.; Vassilou, Panayota (2000). “Sulfur Hexafluoride: Global Environmental Effects and Toxic Byproduct Formation”. Journal of the Air & Waste Management Association. Taylor and Francis. 50 (1): 137–141. doi:10.1080/10473289.2000.10463996
- NIOSH Pocket Guide to Chemical Hazards. “Sulfur hexafluoride“. Centers for Disease Control and Prevention National Institute for Occupational Safety and Health (NIOSH).
- Shriver, Duward; Atkins, Peter (2010). Inorganic Chemistry. W. H. Freeman. ISBN 978-1429252553.