unknown quantity

This results in the release of unknown quantities of neurotoxins, carbon monoxide and other chemicals into the air.

The 46-year-old Dutch coach built a fine reputation with successes at Feyenoord, but was an unknown quantity to many Liverpool supporters and untested in the Premier League.

Humphries, but the veteran is of late something of an unknown quantity.

Reform are still a relatively unknown quantity in Scotland, and their swift rise to prominence is a factor that could make that election fairly unpredictable.

The firm added the crash had caused "multiple explosions" on board and an unknown quantity of jet fuel to be released.