Assertion: fluorine's compound | /r/HasProperty | known since ancient times
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Source sentences:
text: The most common compound of chlorine, sodium chloride (common salt), has been known since ancient times.
text: The most common compound of chlorine, sodium chloride, has been known since ancient times; archaeologists have found evidence that rock salt was used as early as 3000 BC and brine as early as 6000 BC.