Oxygen sources for space flights.

O XYGEN IS combined in many solid chemical forms, but only a few of these have the capa,city to readily release pure oxygen. One such group is composed of t,he alkali and alkaline earth peroxides, sup.eroxides and o,zonides. A second group is composed of the chlorates and perchlorates of the same metals. The former group releases oxygen upon reaction with water or cartoon dioxide and can be classified as demand chemicals. That is, the supply of oxygen released can be made self-regulating by reaction of water and carb.on dioxide in the expired breath. In the second class of compounds, oxygen is released either by direct heating or .by mixing with the oxygencontaining chemicals, a substance vchieh will ,be oxidized by part of the evo.lved oxygen and thus generate sufficient heat to sustain the reaction. This type of reaction is generally known as a controlled type since the rate of oxygen evolution depends on the compo.sition, size, and shape, of the preformed chemical mixture. The combination o.f oxygen supply and carbon dioxide absorbent is unique to .the demand chemicals; the long shelf life and high oxygen density o,f the controlled oxygen .sttp.plied is also deserving of consideration. Both classes .of compounds have been used