Potassium Chlorate at High Altitude: Lost to History

The use of potassium chlorate and other chlorates from the nineteenth century until the present is reviewed with an emphasis on use at high altitude. Chlorates that undergo high-temperature thermal decomposition are a source of supplemental oxygen for inhalation. The oral uses of potassium chlorate on mountaineering expeditions have ranged from simple lozenges for pharyngitis to the erroneous idea that oral ingestion could provide supplemental oxygen and prevent or treat mountain sickness. Furthermore, today's aircraft and spacecraft still employ chlorates and perchlorates to produce emergency supplemental oxygen for inhalation.