Critical temperature: Nitrous oxide

Basic, Basic Sciences

Nitrous Oxide is an anesthetic gas with a low potency with a MAC value of 104%. It is commonly used during mask inductions in pediatric patients, as an adjunct for labor analgesia, and in dentistry offices for conscious sedation. Among anesthetic gases, it has a unique physical chemical profile.

Triple Point: -90.82° C

The triple point of a substance is that at which it can exist in a solid, liquid and gaseous phase depending on the pressure or lack thereof applied (i.e. this is the freezing, boiling and sublimation point)

Critical Temperature: 36.37° C

The critical temperature of a substance is that at which it can no longer be converted from a gas to a liquid no matter the pressure applied to it.

In between these two temperatures, nitrous oxide can exist as a liquid or a gas depending on the pressure applied. Immediately below to the critical point, nitrous will boil at 1050.1 PSI (71.45 ATM) – above this pressure, nitrous oxide exists as a liquid; however, above this temperature, no matter the pressure applied, nitrous oxide is a gas. With such a low critical temperature, nitrous oxide cylinders have the potential for explosion if heated or handled improperly.

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Answered correctly

2017

Year asked

Author
Geoffrey Ramsdell, MD