- An unstable, poisonous allotrope of oxygen, O<sub>3</sub>, that is formed naturally in the ozone layer from atmospheric oxygen by electric discharge or exposure to ultraviolet radiation, also produced in the lower atmosphere by the photochemical reaction of certain pollutants. It is a highly reactive oxidizing agent used to deodorize air, purify water, and treat industrial wastes.
- Fresh, pure air.
- A modification of oxygen, having increased chemical activity; a colorless gas having a peculiar odor like that of air which contains a trace of chlorin.
- In the gaseous state, ozone, if seen through a column of sufficient depth or under considerable pressure, has a blue color like that of ordinary oxygen, but more marked, and when liquefied appears dark blue. The liquid boils under atmospheric pressure at—100° C. (—159° F.). It is magnetic, and more soluble in water than ordinary oxygen. Animals breathing air which contains ozone in appreciable quantity present the phenomena of slow respiration, enfeebled circulation, lowering of bodily temperature, venous condition of the blood, and ultimately death. Air charged with ozone has been applied to the treatment of distilled spirits with a view to the removal of fusel-oil, but with only partial success.
- A colorless gaseous substance (O3) obtained (as by the silent discharge of electricity in oxygen) as an allotropic form of oxygen, containing three atoms in the molecule. It is a strong oxidizer, and probably exists in the air, though by the ordinary tests it is liable to be confused with certain other substances, as hydrogen dioxide, or certain oxides of nitrogen. It derives its name from its peculiar odor, which resembles that of weak chlorine.
- An <xref>allotrope</xref> of <xref>oxygen</xref> (symbol O3) having three <xref>atoms</xref> in the <xref>molecule</xref> instead of the usual two; it is a <xref>blue</xref> <xref>gas</xref>, generated from oxygen by <xref>electrical</xref> <xref>discharge</xref>; it is <xref>poisonous</xref> and <xref>highly</xref> <xref>reactive</xref>, but in the <xref>upper</xref> <xref>atmosphere</xref> it <xref>protects</xref> <xref>life</xref> on <xref>Earth</xref> from <xref>ultraviolet</xref> <xref>radiation</xref>.
- <xref>Fresh</xref> <xref>air</xref>, especially that breathed at the <xref>seaside</xref> and smelling of <xref>seaweed</xref>.
- a colorless gas (O3) soluble in alkalis and cold water; a strong oxidizing agent; can be produced by electric discharge in oxygen or by the action of ultraviolet radiation on oxygen in the stratosphere (where it acts as a screen for ultraviolet radiation)