Assertion: hydrogen fluoride's fluorine | /r/ObjectUse | used in an amount of about 50
Facets:
value: to about 70 ppm
type: OTHER
value: usually
type: TEMPORAL
Source sentences:
text: When the overall impurity content is abont 50 to about 100 ppm, fluorine is used usually in an amount of about 50 to about 70 ppm.