Assertion: ozone | /r/HasProperty | obtained by various methods
Facets:
value: from them
type: OTHER
Source sentences:
text: The resulting mixtures of ozone and original gases are suitable for most industrial purposes, although purer ozone may be obtained from them by various methods; for example, upon liquefaction, an oxygen-ozone mixture separates into two layers, of which the denser one contains about 75 percent ozone.