sulfur sesquioxide

chemical compound

Also known as: sulphur sesquioxide

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 14, 2026

Quick Summary

Sulfur sesquioxide, also known as S₂O₃, is a blue-green solid that is stable only below 15° C (59° F). It is formed by dissolving sulfur in liquid sulfur trioxide.1

Other sulfur oxides include:
* Sulfur dioxide (SO₂): A pungent, colorless, poisonous gas used as a disinfectant, refrigerant, bleach, and food preservative.12
* Sulfur trioxide (SO₃): A colorless compound that is a strong dehydrating agent and highly corrosive.1
* Sulfur monoxide (SO): An unstable colorless gas.1
* Sulfur heptoxide (S₂O₇) and tetroxide (SO₄): Unstable compounds.1

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

3 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

sulfur oxide
…discharge in a mixture of sulfur dioxide and sulfur vapour at low pressure; upon cooling, it condenses to an orange-red solid that decomposes slowly to sulfur and sulfur dioxide. The sesquioxide, formed by dissolving sulfur in liquid sulfur trioxide, is a blue-green solid stable only below 15° C (59° F).…
Read More
…discharge in a mixture of sulfur dioxide and sulfur vapour at low pressure; upon cooling, it condenses to an orange-red solid that decomposes slowly to sulfur and sulfur dioxide. The sesquioxide, formed by dissolving sulfur in liquid sulfur trioxide, is a blue-green solid stable only below 15° C (59° F).…
Read More